simulations on the simbol-x detector...
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Simulations on the SIMBOL-XDetector BackgroundSimulationen zum SIMBOL-X Detektor HintergrundMaster-Thesis von Steffen HaufMarch 2009
Fachbereich PhysikAstroteilchenphysik
Simulations on the SIMBOL-X Detector BackgroundSimulationen zum SIMBOL-X Detektor Hintergrund
vorgelegte Master-Thesis von Steffen Hauf
1. Gutachten: Prof. Dr. H. H. Hoffmann2. Gutachten: Dr. Markus Kuster
Tag der Einreichung:
Erklärung zur Master-Thesis
Hiermit versichere ich die vorliegende Master-Thesis ohne Hilfe Dritter nur mit den angegebenen
Quellen und Hilfsmitteln angefertigt zu haben. Alle Stellen, die aus Quellen entnommen wurden, sind
als solche kenntlich gemacht. Diese Arbeit hat in gleicher oder ähnlicher Form noch keiner Prüfungs-
behörde vorgelegen.
Darmstadt, den 23.03.2009
(Steffen Hauf)
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Abstract
Based on the GEANT4 tool kit, Monte Carlo simulations of the SIMBOL-X on orbit background with the goal of evaluating
the achievable detector sensitivity are computed. The simulated geometry is based on structural design models of the
mirror and detector spacecraft and features pixel detector layout and modelling of the on-satellite data treatment. Using
the characterisation of the instrument response to the diffuse hard X-ray and cosmic ray proton background, optimisations
of the structural layout and data processing are developed, with respect to minimizing the background rates and the anti-
coincidence induced detector dead time.
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Contents
1 A Brief History of X-ray Observatories 11
2 The X-ray Sky 132.1 Black Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 Active Galactic Nuclei . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 The Cosmic X-ray Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.4 Supernova Remnants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 Gamma Ray Bursts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3 The Cosmic Background 163.1 Particle Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2 Photon Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4 The SIMBOL-X Spacecraft 194.1 The Low Energy Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2 The High Energy Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3 The Graded-Z Shield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4 The Anti-Coincidence System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5 Simulations 235.1 Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.2 Modeling SIMBOL-X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.2.1 Detectors - Modeling and Read Out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.3 Modeling the Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.4 The Simulation Executable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
6 Analysis 286.1 Normalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7 Results 317.1 Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7.2 Optimisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7.3 Delayed Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8 Outlook 37
9 Summary 38
A SIMBOL-X Simulation Executable Parameters 45
B Detailed Results 46
5
6
List of Figures
1.1 Relative Absorption of Earth’s Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2 A Wolter-Type I Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3 Comparision of Spatial Resolution of INTEGRAL and XMM Observatories . . . . . . . . . . . . . . . . . . . . . 12
2.1 Compilation of known CXB Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2 Simulation of CAS A* Spectrum as seen by SIMBOL-X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1 Spectral Distribution of the Cosmic Ray Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2 Spectral Distribution of the Proton Background as used for Simulations . . . . . . . . . . . . . . . . . . . . . . 17
3.3 Spectral Distribution of the Cosmic X-ray and γ-Ray Background . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1 Overview of the Low Energy Detector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2 The SIMBOL-X High Energy Detector (Santangelo and Al., 2006) . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3 The SIMBOL-X Focal Plane (Santangelo and Al., 2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4 The SIMBOL-X Focal Plane with Shielding and AC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.1 Verification of GEANT4 results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.2 Schematic of the SIMBOL-X GEANT4 simulation program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.3 The SIMBOL-X geometry as implemented GEANT4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.4 GEANT4 runtime (1000 primary protons) vs. number of cpu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
6.1 Schematic of the SIMBOL-X analysis routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.2 Pixel patterns used for SIMBOL-X framed analysis as given by Strüder, L et al (2000) . . . . . . . . . . . . . . 30
7.1 Origin of LED background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7.2 Origin of HED background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.3 HED AC-Time influence on the Count Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.4 Delayed Background in HED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.5 Delayed Background in HED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7
8
List of Tables
4.1 Compilation of the top level scientific requirements for SIMBOL-X . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2 Layering of the Graded-Z Shield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.1 Physics Processes and their GEANT4 Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.1 Comparsion of SIMBOL-X 5 geometry Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7.2 Current Proton Background Rates for 6.1 Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
7.3 Current Count Rates from TUD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
9
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1 A Brief History of X-ray Observatories
The history of X-ray observations of the universe is relatively new. Although X-rays were discovered by Wilhelm Konrad
Roentgen in 1895 it would take another 60 years until astronomers where able to catch a first glipse of the X-ray sky. This
is mainly because the Earth’s atmosphere is transparent only for certain parts of the electromagnetic spectrum as can be
seen in Figure 1. X-rays along with gamma rays are readily absorbed. While this is very good for life on earth it also
blocks some of the most interesting emission from ground based observations. Theoretical calculations at the beginning
of the 20th century had concluded that many galactic and extragalactic objects, such as neutron stars, galactic clusters
and black holes should have unique features in their X-ray light. But without having any means to leave the obstructing
atmosphere any observatories were of a more speculative nature.
Figure 1.1: Relative Absorption of Earth’s Atmosphere
Relative absorption of EM-Radiation by Earth’s at-
mosphere and the interstellar medium (Camenzind,
2003)
Figure 1.2: A Wolter-Type I Telescope
Cut through the nested shells of a Wolter-Type I tele-
scope (Wolter, 1952)
This didn’t change until Wernher von Braun constructed the V2 during World War II. While being kept a closely guarded
military secret during and shortly after the war, scientists soon began persuating the U.S. Military (which had taken von
Braun and his engineers to the States), to allow use of their rockets for science. By the early 1950’s the first sounding
rockets with X-ray sensitive detectors were launched. At the beginning these were quite simple proportional counters,
much like Geiger-Muller-detectors, which did not have any spatial resolution. Very crude directional information could
be deduced by collimation of the incident light. While this of course does not allow any detailed studies of individual
objects, it did detect X-ray signals in the sky (especially towards the very bright Cygnus X-1) and motivated building more
sophisticated detectors (Chodil et al., 1965).
The first logical step was to move from suborbital sounding rockets which offered observation times of a few minutes
to a truely orbital observatory. This first X-ray Satellite, Uhuru, stilled used proportional counters along with all their
disadvantages, but due to the longer observation times was able to detect 339 different sources. It distinguished Cygnus
X-1 as an inidividual source, therewith discovering the first candidate for a black hole (Giacconi et al., 1971). The
next major breakthrough, imaging detectors, would first require solving some important engineering feats. Because
normal lenses and mirrors do not focus X-rays, Wolter-type optics have to be used. This involves nesting multiple
metal shells inside each other, polished to nanometer precision. Total reflection then occurs on theses surfaces which in
combination with hyperbolic surface shapes allow to focus X-ray radiation onto pixeled detectors as sketched in Figure
1. The first satellite to use this new technology was NASA’s HEAO-2, better known as Einstein. Compared to Uhuru this
new generation of observatories improved detection limits by more than two orders of magnitude (Giacconi et al., 1979)
and allowed the catalogisation of 1000s of X-ray sources. Engineering advances in mirror-construction and digital pixel
detectors lead to order of magnitude improvements with each new observatory. Another notable satellite was ROSAT,
which increased the number of catalogued objects to over 125,000 (Voges et al., 1999). This trend has continued and the
two most modern observatories ESA’s XMM Newton and NASA’s Chandra now offer spatial resolution in the arcsecond
range and spectral resolution of a few ten eV (Center, 1999), (Jansen, 1999).
All of these highly sensitive detectors share one downside: their imaging optics are limited to the soft X-ray band,
energies above 15 keV are not accessible. This is because their focal length, limited by the available launch systems, is
basically too short. The focal length of a gracing incidence optics can be calculated via the complex index of refraction
(RWTH Aachen, N.d.):
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n= 1− δ+ iβ (1.1)
The X-rays interact with the shell electrons of the mirror atoms. Using a Drude model ansatz one can calculate values
of δ ≈ 10−5 and β ≈ 10−6. Combining this with Snellius’ Law and approximating that no absorption takes place i.e. β = 0
gives a critical angle ΘC :
1−δ = cos ΘC (1.2)
≈ 1−Θ2
C
2(1.3)
ΘC =
r
r0λ2
πNA
Z
Aρ (1.4)
ΘC ∝ λ ∝1
E(1.5)
with the wavelength λ, bohr radius r0, atomic charge Z , Avagadro’s number NA, molar mass A and density ρ. Thus the
focal length
LF ∝1
ΘC
∝ E (1.6)
increases with incident photon energy E. Focussing hard X-rays requires focal lengths in the range of 20 meters.
Because of said launch limitations, today only non-focussing instruments operate in this hard X-ray regime. Though
some spatial resolution is possible by using coded masks (i.e GLAST, INTEGRAL), there still is a big gap in detection
resolution as illustrated in Figure 1.3. Even though every new X-ray observatory has been of great benefit to astronomers’
and astrophysicists’ understanding of the universe, the question remains if we can expect important breakthroughs when
viewing the hard X-ray sky. The next chapter details these possible scientific outcomes.
Figure 1.3: Comparision of spatial resolution of INTEGRAL and XMM observatories. SIMBOL-X will reach near XMM
resolution (Santangelo and Al., 2006)
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2 The X-ray Sky
Intensive surveys in the soft X-ray spectrum have revealed quite a lot about super nova remnants, black holes and
galactic clusters over the last decades. While the earlier observatories were in general more useful for finding and
classifying sources, high resolution observatories like XMM and Chandra are now being used to take a more detailed
look. Their spatial resolution combined with spectral sensitivity allows the study of small regions of supernova remnants
or galactic clusters. Here we can for instance observe X-rays originating from bremsstrahlung emitted by relativistic
particles. Though we see that strong acceleration mechanisms must take place in the vincinity of these remnants, black
holes, clusters of galaxies, neutron stars and the galactic center, to name just a few, the acceleration region itself is often
obscured by surrounding dust and gas. Because this dust is opaque even for less energetic soft X-rays, scientists are
looking towards more powerful probes: hard X-rays and gamma rays. Having an imaging hard X-ray observatory could
therefor shed significant new light on a lot of very energetic cosmological phenomena. Some of which we will go into
more detail.
2.1 Black Holes
Einstein’s theory of general relativity includes the possibility of space time singularities, caused by very massive objects.
These objects would bend space-time so much that not even light could leave their gravitational sphere of influence.
Everything crossing this ”Event Horizon” will stay inside the black hole (hence the name). While this is certainly also
true for X-rays and will prevent detecting ”direct” black hole radiation, we should see some signature of the matter which
is nearing it’s ”death”. This is because the enormous gravitational forces will put great stress on everything which nears
the hole, accelerating particles to highly-relativistic velocities, while they also start rotating, forming an accretion disk.
Black holes seem to come in two sizes: stellar size black holes from approximately 3.0 to 15.0 solar masses and Super
Massive Black Holes with millions of solar masses, residing in most galactic centers. Additionally to the optical thick but
geometrical thin disk of gas and dust, black holes usually feature highly relativistic particle jets, exiting at their poles.
While we see the jets, their origins are masked by the disk, inaccessable with soft X-ray observations.
This is why jet creation is not very well understood yet. Especially SMBHs, are almost completely occluded from our
soft X-ray view. The closest one, located at our own galaxy’s center shows some small soft residue, and gamma ray
observatories can put some bounds on it’s location, but a hard X-ray observatory like SIMBOL-X is needed to greatly
improve our understanding of accretion and galactic centers. In particular a SIMBOL-X class telescope would allow
resolving at least 50% of the cosmic X-ray background at its maximum energy leading to a more complete census of
SMBHs, allow more detailed studies of accretion around stellar and SM black holes and resolve our own galactic center,
pinpointing the origin of hard X-rays therein (Santangelo and Al. (2006)).
2.2 Active Galactic Nuclei
Active Galactic Nuclei are regions in the centers of galaxies which have a luminosity much higher than what would
be expected from the surrounding galaxy. The energy source thought to be driving them are SMBH’s at their center.
Observations show different kinds of AGN, for instance Seyfert-I and Seyfert-II type galaxies or also Quasars. Quasars are
thought to be the most distant AGN we see, placing them at the beginning of cosmologic evolution, while both Seyfert
types are thought to be the same class of objects observed from different angles. In Seyfert-I galaxies we directly observe
the center region since our line of view is perpendicular to the galactic plane. Seyfert-II galaxies we observe tilted, so
Compton scattering in the accretion disc obscures the center region. SIMBOL-X will be able to resolve the center regions
of these mildly Compton thick AGN, since radiation above 10 keV is still able to penetrate the surrounding Hydrogen if
NH < 1024.
Above NH = 1025 galaxies are called heavily Compton thick and the entire spectrum is supressed. Heavily Compton
Thick objects are characterized by strong Fe-Kα and Fe-Kβ lines and a Compton scattered continuum. Unfortunately
some of these features lie just above what can be detected by current telescopes but will be well within the SIMBOL-X
energy range. A better understanding of AGN is important for our concept of cosmologic evolution as outlined in the
next section.
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2.3 The Cosmic X-ray Background
Besides the proton background component which can be mistaken as X-ray hits and will be detailed later, there is another,
true X-ray background component. This cosmic X-ray background (CXB) can be linked to the sum of all AGN, which con-
tribute an important part to it. At low X-ray energies, where imaging telescopes are available and can resolve individual
sources around 80% of the CXB has been directly linked to Seyfert galaxies or Quasars in the 2-6 keV range and still
50-70% can be resolved in the 6-10 keV range (Brandt and Hasinger, 2005). At energies above 10 keV and especially
around 30 keV, where the maximum of the CXB is located, current focussing telescopes offer poor performance so that
only a few percent of the sources could be identified. Figure 2.3 shows that there still is a discrepancy between the data
collected by focussing observatories and those without, which is hoped to be understood with help of SIMBOL-X, which
will be the first single telescope to cover most of the important energy range. This could also help investigate if the CXB
is an echo of black hole creation, which would be the case if it is the sum of accretion radiation over cosmological time
scales (Santangelo and Al., 2006).
Figure 2.1: Compilation of known CXB data (as of 2006), San-
tangelo and Al. (2006)Figure 2.2: Simulation of CAS A* spectrum as seen by
SIMBOL-X (Santangelo and Al., 2006)
2.4 Supernova Remnants
Massive stars celebrate the end of their lifetime with a big cosmic firework: a supernova explosion. A star above the
Chandrasekhar mass limit (1.38 solar masses, Mazzali et al. (2007)) goes nova after it has burned all of it’s fusion fuel.
With the shortfall of the radiation pressure a gravitational collapse is triggered, usually resulting in a neutron star or
black hole, if it’s mass is above the Oppenheimer-Volkoff limit (1.5 - 3.0 solar masses, Bombaci (1996)). The collapse
releases large ammounts of gravitational energy. This energy heats surrounding stellar mass and expells it into space
creating shock fronts against the surrounding interstellar matter. In these shock fronts strong acceleration mechanisms
are present which result in typical radiation: thermal bremsstrahlung caused by shock heating of the interstellar medium,
synchrotron emmission of shock accelerated electrons transversing magnetic fields generated by the surrounding plasma
and non-thermal bremstrahlung emitted by suprathermal electrons accelerated at the shock boundries (Giacobbe, 2005;
Bethe, 1990). Soft X-ray observations have shown that the syncrotron emission from these remnants fits the cosmic ray
(CR) spectrum observed on Earth, fueling the discussion if novas are the origin of CR up to the knee at 1015 eV. Hard X-ray
observations are now needed to confirm this correlation above 10 keV. Figure 2.3 shows how SIMBOL-X will perform on
a typical SNR. SIMBOL-X observations of SNRs will also aid our understanding of nucleosynthesis in young remnants
(Santangelo and Al., 2006).
2.5 Gamma Ray Bursts
Gamma Ray Bursts are considered as some of the most energetic events in the known universe. While the details of their
creation are far from understood it is generally accepted that they occur when massive stars explode on cosmological
distances. This creates internal shocks within the collapsing star and external shocks from jets outbursting against the
interstellar medium. The internal shocks a responsible for the actual burst, while the external shocks create an X-ray
14
afterglow (Rees and Meszaros, 1998). The actual burst will not be detectable by SIMBOL-X since it is outside the
detectors energy range, but the afterglow is strong in the hard X-ray regime. With the aid of triggers from telescopes like
AGILE, GLAST or SWIFT, SIMBOL-X will be able to give a better unterstanding of the acceleration mechanisms within the
jets. Great benefit should come from SIMBOL-X’ ability to study the spectral development of such a burst simultaniously
in the soft and hard X-ray band.
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3 The Cosmic Background
While some of the singular sources described in Chapter 2 will be quite bright, most extended sources like supernova
remnants or galaxy clusters and heavily obscured singular sources like AGN and accretion Disks around black holes will
not. SIMBOL-X’ success will critically depend on it’s ability to distinguish true X-ray photons within it’s field of view from
other unwanted background events. To do this a good understanding of the ”background” is necessary, which can be
achieved by exposing a simulated spacecraft to the known background intensities. This simulation is the main scope of
this work, but before we begin discussing the actual simulations we want to get an idea of the background components
involved.
3.1 Particle Background
Every second the Earth and every other object in the universe are bombarded by numerous highly energetic particles,
called Cosmic Rays. Luckily for ourselves our atmosphere blocks most of them, but as discussed in the introduction
there are good reasons for positioning an X-ray telescope like SIMBOL-X outside this protective shield. Without natural
protection SIMBOL-X will experience quite a lot of Cosmic Ray impacts. Lower energy Cosmic Rays can readily be
observed by most space based telescopes as the background they see when looking at blank parts of the sky. The high
energetic rays lie outside the detection range of satellites but can be seen by ground based Cherenkov telescopes when
they interact with Earth’s atmosphere. While their origin is still somewhat uncertain (see 2.4), the shape of the spectrum
is quite well determined (except for the highest energy regions). The spectral shape is shown in Figure 3.1. As can be
seen the proton component dominates the spectrum with 98% over the Helium nuclei and leptonic components. Heavier
nuclei are also present in the spectrum but their flux is even below the leptonic flux. This is why it was chosen to only
simulate the proton part of the CR-spectrum for SIMBOL-X background analysis.
When simulating the cosmic ray flux one must also take into account the influence of the Sun’s and Earth’s magnetic
field. The Sun emits large ammounts of charged particles, called the solar wind, which in turn are mainly responsible for
the interplanetary magnetic field. Because this field deflects galactical cosmic rays their flux near Earth is anti-correlated
with the solar activity: during solar maxima the cosmic ray flux will be reduced while it is amplified during solar minima.
The flux difference between minima and maxima is about a factor of 2 (Daly (1995)). Because of this the extrasolar flux,
while being isotropic, depends on location and time.
Contrary to this the flux of the solar soft proton component emitted from the Sun with energies of up to a few 100keV
increases during solar maxima. It also depends on the Earth’s distance to the Sun and has its maximum when Earth is
in the perigee of it’s orbit (Read and Ponman, 2003). Both variabilities need to be accounted for in the simulation input
spectrum, especially since these soft solar protons have kinetic energies within the SIMBOL-X detection ranges.
For the simulations the proton spectrum in Figure 3.1 computed by Claret A. (2006) using SPENVIS (Belgian Institute
for Space Aeronomy, 2006) for the targeted SIMBOL-X launch date near the solar maximum was used. The mean proton
flux for this spectrum is 2.32 protons/(cm2 · s) for 4π (Chipaux et al., 2008). We also assume that the flux is isotropic and
without temporal variance since the simulated times are less than one hour.
More energetic protons can hit parts of the spacecraft structure where they deposit energy or activate nuclei. Hadronic
interactions between the incident protons and spacecraft structures may result in particle showers which produce hun-
dreds of secondaries ranging from muons, positrons and electrons to kaons, pions and more exotic particles. These
secondaries along with the primaries will then interact via ionisation, elastic and inelastic scattering, Bremsstrahlung,
Compton-scattering and other electromagnetic and hadronic processes. So while the higher energy protons themselves
lie outside the detection range, their secondaries may have critical energies lying within the detection ranges. The
simulation must be able to account for these possibilities.
A third particle backgroud component orignates from the compression of Earth’s magnetic field, when encountering
the solar wind. This compression results in belt like magnetic mirrors (the Van-Allen-Belts) in which charged particles
from the solar wind are trapped. The inner belt extends from an altitude of 700 - 10,000 km and mainly contains highly
energetic protons originating from atmospheric cosmic ray collisions with energies between 100 keV to 100s of MeV. The
magnetic fields in the outer belt (15,000 - 60,000 km) are weaker so mainly electrons, which have smaller gyroradii than
the protons, are trapped. These electrons originate from local acceleration and inward radial diffusion and have energies
of 0.1-10 MeV. Their flux depends strongly on geomagnetic anomalies and the current solar activity (Horne, 2005).
To avoid increased detector background or even damage to the detectors and electronics by Earth’s radiation belts the
perigee of SIMBOL-X’ orbit will be at 35,000 km, well outside the inner Van-Allen-Belt. A magnetic deflector on board
16
Figure 3.1: Spectral distribution of the Cosmic Ray
background. For the simulation we only
use the dominant proton component (Meyer,
1969)
Figure 3.2: Spectral Distribution of the Proton
Background by Claret A. (2006) as
used for simulations (squares). For
comparision spectra by O’Gallagher
and Maslyar III (1976) are also shown
Figure 3.3: Spectral distribution of the Cosmic
X-ray and γ-ray Background (Gruber
et al., 1999)
the mirror spacecraft will be used to deflect field of view electrons and soft protons from the outer belt, which will be
passed twice every orbital revolution. This is why these electrons will not be simulated.
3.2 Photon Background
As detailed in 2.3 SIMBOL-X will certainly be used for observing the CXB background by focussing photons within it’s field
of view. While this is desirable for such observations, random CXB photons have enough energy to deposit unwanted hits
in a non shielded detector. This is why it is important to simulate the background rate due to non field of view photons.
These follow a spectrum as shown in Figure 3.2 after Gruber et al. (1999). The CXB flux is again assumend isotropic and
can be integrated to be 197.2 photons/(cm2 · s) for 4π (Chipaux et al., 2008).
At softest X-ray energies up to 1 keV the Sun is the strongest X-ray source near Earth. Because it’s lower energies
outside the detection ranges the solar X-ray flux is less important to the SIMBOL-X background. Problematic are the
fluxes in the soft and low hard X-ray regime which orignate from AGN and supernova remnants as decribed in the
previous chapter and which have kinetic energies within or above the detection range (Read and Ponman, 2003; Gruber
et al., 1999).
17
These CXB-Photons can react with the satellite structure in multiples ways. The most important include photo-
ionisation and Compton-scattering as well as pair production at higher photon energies (≥ 1022 keV) This is especially
problematic for higher energy photons, which are able to penetrate parts of the graded shield and then ionize or pair
produce electrons in the lower layers which then contaminate the detectors.
18
4 The SIMBOL-X Spacecraft
The SIMBOL-X observatory will utilize a radically new design to achieve the necessary focal length for imaging in the
hard X-ray regime. Instead of trying to tackle the problem with one very large and expensive satellite, SIMBOL-X will use
two independent spacecrafts held in position by a laser guidance system. The mirror-spacecraft will use a Wolter I-type
mirror, currently designed to be built of over 100 shells polished to nanometer accuracy. This spacecraft will also feature
a spider-like arrangement of 1.7 Tesla magnets which are strong enough to deflect electrons and lower energy protons
within the high-energy-detector (HED) range of 5-100 keV. Additionally a sky-shield will keep optical and X-ray photons,
which didn’t pass the focussing mirrors, off the focal plane. The sky-shield is to be aided by a collimator at the front of
the detector spacecraft. It’s opening angle is calculated to only leave the mirrors non-obscured.
The detector-spacecraft will obviously hold the main detectors but also a shielding and anti-coincidence system. There
are two detectors in the focal plane: the low energy detector (LED) which is sensitive in the 0.5-20 keV energy range
and the HED which is sensitive in the 5-100 keV energy range. Their details are discussed in Section 4.1 and Section
4.2. Furthermore, the telemetry and data processing electronics will be located on this spacecraft. A compilation of the
technical requirements can be found in Table 4.1.
Table 4.1: Compilation of the top level scientific requirements for SIMBOL-X as given by Santangelo and Al. (2006). The
desirable energy band has been increased to 0.5-100 keV for simulation purposes
Parameter Value
Energy band 0.5 - ≥ 80 keV
Field of view (at 30 keV) ≥ 12’ (diameter)
On-axis sensitivity ≤ 10−14 c.g.s.( 0.5 µCrab), 10-40 keV band, 3σ, 1Ms, powerlaw spec. with Γ=1.6
On-axis effective area ≥ 100 cm−2 at 0.5 keV
≥ 1000 cm−2 at 2 keV
≥ 600 cm−2 at 8 keV
≥ 300 cm−2 at 30 keV
≥ 100 cm−2 at 70 keV
≥ 50 cm−2 at 80 keV (goal)
Detector background < 2×10−4ctss−1cm−2keV−1 HED
< 3×10-4 cts s−1cm−2keV−1 LED
Line sensitivity at 68 keV < 3 ×10−7 ph cm−2s−1, 3σ, 1Ms(2 ×10−7 goal)
Angular resolution ≤ 20”(HPDa), E < 30 keV
≤ 40”(HPD) @ E = 60 keV (goal)
Spectral resolution E/∆E = 40-50 at 6-10 keV
E/∆E = 50 at 68 keV (goal)
Absolute timing accuracy 100 µs (50 µs goal)
Time resolution 50 µs
Absolute pointing reconstruction ≈ 3’ (radius, 90%) (2” goal)
Mission duration 2 years of effective science time + provision for at least 2 calendar years extension
Total number of pointings > 1000 (nominal mission) 500 (during the 2 calendar years mission extension)
a Half Power Diameter
4.1 The Low Energy Detector
The SIMBOL-X LED is designed as a monolithic silicon DEPFET1 detector (Figure 4.1(a) consisiting of 128x128 pixels.
This design not only offers the advantage of not having any insensitive areas but it also provides as homogenious trans-
mission over the full detector area for the beneath lying HED. (Lechner et al., 2003). Additionally the DEPFET design
offers the advantages of high read-out rates, high quantum efficiency and radiation hardness. X-ray photons entering
the detector ionize the silicon atoms and thereby create electrons. These then follow the field gradient created by a
1 Depleted P-Channel Field Effect Transistor
19
concentric p-n-diode arrangement, known as a silicon drift detector (Figure 4.1(c)), across the area of each pixel. An
internal gate at the bottom of each potential well store theses electrons until the output circuit is activated. A schematic
of this can be seen in Figure 4.1(b). During this integration process no voltage needs to be applied to the detector. This
not only minimizes power consumption of the satellite but also reduces electrical heating of the detector components
which directly decreases vulnerability to thermally induced noise.
With a thickness of 450 µm the LED will be sensitive for photons with energies between 0.5-20 keV with a quantum
efficiency of 96% at 10 keV and 45% at 20 keV (Ferrando, 2006). The LED readout rate is designed to be 8000 Hz with
per row readout geometry. After a row is read out and reset it can start integration again without having to wait for the
remaining rows to be read out. The LED back-end electronics feature AC-rejection and frame analysis. Frame analysis
will include pattern and MIP2 rejection routines and significantly minimizes required telemetry rates to the ground.
(a) Cutaway of a DEPFET integrator as located at
the center of each SDD.
(b) Schematic drawing of a DEPFET.
(c) Complete SDD with DEPFET at its center.
Figure 4.1: Overview of the Low Energy Detector (Santangelo and Al., 2006).
2 Multiply Ionising Particle, particles which deposit energy in multiple pixels above a given threshold.
20
Figure 4.2: The SIMBOL-X High Energy Detector (Santangelo and Al., 2006)
Figure 4.3: The SIMBOL-X Focal Plane (Santangelo and Al., 2006)
4.2 The High Energy Detector
The SIMBOL-X HED will consist of 128x128 CdZnTe-Detectors with a sensitive area of 8.49×8.57 cm2 and underlying
amplifier and digitization electronics arranged into 16x16 so-called Caliste modules, totalling 64 detectors per module.
Each module has it’s own back-end electronics. The CdZnTe acts as ionisation volume which can reliably stop photons up
to 100 keV (≈ 100% quantum efficiency at 80 keV) and produces negligable Compton-scattering (Ferrando et al., 2004).
Integration and AC-rejection are done within a time window of 5 µs per pixel event by event. The possiblity of pattern
analysis for neighbouring pixels is being investigated as a background reduction method in addition to the possibility of
using a longer AC black out time.
4.3 The Graded-Z Shield
The graded-Z shield is placed inside the anti-coincidence system (see 4.4). It consists of thin layers of materials with
varying effective nuclear charge. The outermost layer has the highest Z-value. High-Z materials are dense and therewith
good absorbers but also emit strong Bremsstrahlung. This Bremsstrahlung is absorbed by the innerlying layers which
in turn emit fluorescence emission at energies decreasing with Z. The thickness of each layer is chosen so that it can
readily absorb the emission from it’s outerlying neigbour. The last layer has a high Carbon-abundance, which has just one
21
Figure 4.4: The SIMBOL-X focal plane as modelled in Saclay. HED is shown in blue, LED in light brown. The heat diffuser
is drawn in green. The detectors are enclosed by shielding (blue, orange) and the AC (purple). Also shown are
the mechanical supports and the detector platform.
flourescence line at 0.284 keV (National Institute of Standards and Technology (1996)), which is well below the detection
sensitivity of the LED. Ideally the graded shield absorbs those particles which are not energetic enough to deposit energy
above the anti-coincidence trigger threshold. The layer materials along with their corresponding thickness are given in
Table 4.2.
Table 4.2: Layering of the Graded-Z Shield. Spectroscopic data from National Institute of Standards and Technology (1996)
Material Z Thickness [mm] Kα Energy [keV]
Tantalum 73 1.5 57.3
Tin 50 2.2 25.3
Copper 29 0.5 8.0
Aluminum 13 0.27 1.5
Carbon 6 0.1 0.3
4.4 The Anti-Coincidence System
Apart from the graded-Z shield the Anti-Coincidence (AC) system is the most important background reduction method.
It consists of LYSO3 scintillation plates which surround the detectors and graded-Z shield, leaving a hole towards the field
of view. The plates are attached to photo-multiplier tubes and digitizers which quantify the energy deposit in each plate.
If the energy deposit reaches a certain treshold an AC event is triggered, which marks the current LED frame or HED
event as background contaminated. The trigger threshold should be low enough to detect particles which have enough
kinetic energy to pass the graded shield, but also high enough not to cause continuous dead time. Finding a desirable AC
threshold is part of the simulation goals.
The AC system consists of four AC groups: the bottom plate, the lower lateral plates, the upper lateral plates and the
roof plates. Each can be run with different trigger energies. Other scenarios include only using the upper AC system for
the LED because the volumnous HED would block most background events coming from below. Simulations of the AC
system should focus on reducing dead time while maintaining a high rejection efficiency.
3 LuYSiO5 : Ce3+
22
5 Simulations
In order to confirm mission feasibility a simulation of the expected background rates for both detectors is required. This
simulation should include all relevant physical processes and be based on the actual satellite geometry. Furthermore
it needs to model features of the readout electronics since these include multiple veto mechanisms. Based on these
simulations the focal plane geometry can be optimized.
5.1 Tools
The tool of choice for doing the physical simulations is GEANT4 (Agostinelli et al., 2003). This C++ Monte Carlo tool-kit
is developed and maintained at CERN1. Originally designed to model particle accelerators it by now includes models for
numerous physical processes in a variety of energy ranges. The only requirement for the modeled geometry is that it is
to be enclosed in a leak free volume which doesn’t change during simulation. Because of this GEANT4 is not limited to
simulating particle accelerators but can also be used for astrophysical purposes.
GEANT4 is programmed after the object orientated paradigm of C++. The toolkit itself consists of a collection of base
classes and libraries which the user has to modify for his or her needs. This allows fast building of simple simulations but
also gives the user access to detailed data along the simulation track which is of great benefit to the SIMBOL-X simulation
since a detailed understanding of the processes and particles involved in creating the background is required.
Prior to starting the actual SIMBOL-X simulations the accuracy of GEANT4 was tested against known flourescence
spectra and experimental quantum efficiency data for LE and HE detector materials. Work done by Christian Klose
during his diploma thesis (Klose, 2006) verified that GEANT4 is capable of modeling the observed data quite accurately.
Results can be seen in Figures 5.1(b) and 5.1(a). Since then GEANT4 physics models have improved further, minimizing
the apparent deviation between simulation and measurement in Figure 5.1(a) below 5%.
100
102
104
106
108
, , , , , , , ,1.1 1.2 1.3 1.4 1.5 1.6 1.8 2
Gammas
Fluoreszenzlinien von Al
Cou
nts
/ keV
Energie [keV]
(a) Comparision of GEANT4 simulated X-ray
flourescence lines with measurements of Alu-
minum (Klose, 2006). Kα2at 1.4863 keV, Kα1
at
1.4867 keV and Kβ at 1,5574 keV (Thompson and
Kortright (2001))
1 10 1000
20
40
60
80
100PTB
Geant4 4.8.0p1 LESi: 280 µm Si02/SiO: 30 nm/3 nm
Orsay
Old Geant4
Geant4 4.8.0p1 HESi: 280 µm Si02/SiO: 30 nm/3 nm
Qua
nten
effiz
ienz
[%]
Energie [keV]
(b) Comparision of GEANT4 simulated quantum
efficiences with measurements. Low energy data
from Hartmann, Stephan and Strüder (2000). High
energy data measured in Orsay labs. (Klose, 2006)
Figure 5.1: Verification of GEANT4 results
Additionally the radioactive decay module was tested. Halflife times and decay energies seem to be quite accurate,
the neutron flux should be further verified. A schematic of how the SIMBOL-X GEANT4 simulations work can be seen in
Figure 5.2.
1 Conseil Européen pour Recherche Nucléaire
23
Figure 5.2: Schematic of the SIMBOL-X GEANT4 simulation program
5.2 Modeling SIMBOL-X
To keep simulation time within a reasonable limit the simulation geometry must be a simplified version of the real me-
chanical design model (Figure 5.3). Because satellite parts closest to the two detectors and the AC-system have the
biggest impact on the overall background rate and spectrum these components were modeled with greatest detail. This
includes exact modeling of the chemical compounds in the graded shield as well as their thickness, the surrounding sup-
port structures as well as the collimator. More distant components have been simplified. The satellite auxilary structures
such as propulsion systems and overall mechanical support as well as backend electronics are modeled as a solid alu-
minum cube with an expected mean density of these components. From the mirror spacecraft only the skyshield which
will have the most impact on incident photon background is modelled. A corrected flux which models the performance
of the electron-deflection magnets is to be included in the future.
Each geometry is transferred from CAD-files to a format GEANT4 can interpret. This includes parameterizing parts of
the geometry so that the different simulation codes from the collaboration partners can attach to a common geometry
base.
Protons and photons can be selected as incident primary particles each following the spectral shape as described in
Chapter 3. To assure a isotropic input distribution with most of the emitted particles actually hitting the geometry a
spherical source of 50m radius was chosen. Particles are only emitted at an half angle of 0.01 radians off the surface
normal producing a cone which tightly encloses the satellite. The intersection of all cones originating from everywhere
on the source sphere forms a new inner sphere which is isotropic towards it’s inside. This source geometry was realized
with the general particles source (gps) of the GEANT4 package (Furguson, 2000).
5.2.1 Detectors - Modeling and Read Out
The modeling of the LED and HED has evolved from a single Silicon and CdZnTe slab to a truely pixeled detector design,
modeling each pixel and for the HED the caliste modules. The individual pixels are mapped to sensitive detectors. If one
of these detectors recieves a hit with a non-zero energy deposit this energy is stored on a per-pixel basis. Further hits from
24
Table 5.1: Physics Processes and their GEANT4 models. The list is missing auxilary classes i.e. for cross-sections
Processtype GEANT packages
EM-Ionisation: e-, e+, mu
G4hLowEnergyIonisation, G4hIonisation,G4ionIonisation,
G4MuIonisation, G4eIonisation, G4LowEnergyIonisationEM-Scattering: Rayleigh, Compton
G4LowEnergyRayleigh, G4LowEnergyCompton, G4MultipleScatteringEM-Gamma: photo-electric, gamma con-
versionG4LowEnergyPhotoElectric, G4LowEnergyGammaConversion
EM-Bremsstrahlung: e+, e-
G4LowEnergyBremsstrahlung, G4eBremsstrahlungEM-Other: capture, pair-prod., annihil.
G4eplusAnnihilation, G4MuPairProduction,
G4MuonMinusCaptureAtRestHadron-Breakup: Fermi, String, Fragmen-
tationG4FermiBreakUp, G4QGSMFragmentation, G4ExcitedStringDecay
Hadron-Scatter: elastic, inelastic + pro-
ton, neutronG4LElastic, G4NeutronHPElastic, G4NeutronHPInelastic
Hadron-Cascades
G4BinaryCascade, G4BinaryLightIonReactionHadron-Capture
G4LCapture, G4NeutronHPCaptureHadron-Other
G4LFissionRadioactive Decay (optional)
G4RadioactiveDecay
the same primary particle on a previously hit pixel add their energy to the previously stored deposit. Pixel-identification
is accomplished by the unique copy number2 of each pixel.
Besides of the energy deposit the sensitive detectors also store the coordinates of the pixel, particle type, creation
process type, primary event number and event global time3 for each pixel hit. After the simulation of a primary event is
completed this information is written into two binary files, one for LED-hits and one for HED-hits.
The anti-coincidence system is modeled in much the same way. Each AC slab is assigned to a sensitive detector, which
on the same code base as the LED and HED detectors, sums multiple hits to the same slab as it would with pixels.
The binary AC output file stores copy number, energy deposit and event global time as well as particle and process
imformation.
Additional optional optimisation components have also been included in the detector modeling. They are discussed in
more detail in Chapter 7 - Results.
5.3 Modeling the Physics
The physic models where chosen to account for the processes and particles described in Chapter 3. The electromagnetic
processes where modeled using the GEANT4 low energy extensions (Apostolakis, 1999) to include more accurate sim-
ulation results in the LED energy range. The processes modeled are summarized in Table 5.1 along with the hadronic
processes (from the std-hadron package) included (CERN, 2008).
2 In GEANT4 copy numbers may be used to identify parts of a geometry especially if multiple identical copies exist3 Time since the primary particle was emitted
25
(a) A cross section of the SIMBOL-X focal plane as modelled in GEANT4. The AC setup around the detectors at
the center is shown in red. The graded shield is drawn in green and light blue. Supporting structures are drawn
in purple and green. To the left part of the satellite platform is visible, while the colimator extends to the right.
Also shown are the trajectories of 10 primary protons as well as their secondaries.
(b) The SIMBOL-X detector spacecraft as mod-
elled in GEANT4
(c) Full view of the GEANT4 geometry. The
skyshield is to the left. The detector spacecraft
to the right.
Figure 5.3: The SIMBOL-X geometry as implemented GEANT4
26
5.4 The Simulation Executable
The resulting executable file has two major run modes: The single CPU version is useful for visualising the geometry
and tracks, preferably with OpenGL4. It can be used for debugging and for tracking analysis. The standard visualisation
macro includes multi color output of different particle types. It should not be used for running complete simulations for
background rate output since it will not take advantage of multicore systems. Also the graphical frontend reduces CPU
time available to the simulation.
The second mode can be used on a multi-processor or cluster system. The number of clients can be controlled via a
configuration file (see Appendix A. A networked run is basically possible). This mode should always be run automated
without visualisations, as these would spawn a display on each client. During the run it displays the currently processed
event number and after finishing the resulting hits are written to three different files: one for HED, LED and the anti-
coincidence. Two additional files are generated to map the particle origin data to the geometry and phyics processes. A
multiprocessor run is recomended for high particle count simulations since the performance scales almost linear with the
number of CPUs (Figure 5.4).
A detailed discription of both modes along with the necessary binaries can be found in the appendix.
Figure 5.4: GEANT4 runtime (1000 primary protons) vs. number of cpu.
4 Open Graphics Language, a open graphics standard maintained by SGI
27
6 Analysis
While the C++ base of GEANT4 would also provide the functionality of directly analysing the simulated hit data, it
was chosen to outsource analysis routines to an IDL program. This offers the advantage that simulation and analysis
are independent of each other and multiple scenarios can be tested with just one simulation result. While geometry is
hardcoded into the simulation, anticoincidence treatment and backend data processing routines are not and thus can be
quickly interchanged. This will be explained in detail in this chapter, an overview can be seen in Figure 6.1.
Before starting the actual analysis the binary imput data from the simulation is brought into a FITS-conform tagged
structure. In a next step the LED is binned into frames, the HED data is allocated into 5µs read out periods. This is done
by multiplying the event number by the mean time between two primary events. This mean time is calculated from the
input spectrum (simulation time t from Equation 6.4 devided by the number of primaries). The AC is later individually
binned for LED and HED analysis. Additionally the energy deposits for the LED and HED are brought into FITS pha
and pi formats. For analysis pi-energies in eV are used. Data preparation is completed by checking for duplicated pixel
coordinates in one frame (time period). If these occur their energies are summed and the duplicates are deleted.
Actual analysis starts with AC-treatment of the HED and LED data. For this the AC-detector file is checked if at a given
time any of the AC plates has a energy deposit greater than a given threshold. The fastet way of doing this in IDL is using
the histgram function with index reversal enabled. Both AC and detector data are binned into histogram of equal bin size
and length. From the substraction of both histograms the AC-vetoed frames are identified and excluded. AC-treatment is
variable enough to allow one AC trigger to block multiple frames or timing periods.
After AC treatment a HED-Level-1 hit analysis as will probably be carried out on-satellite, is performed: neigbouring N
pixel hits within one Caliste module are grouped as a pattern. If N exceeds a threshold, currently set to three, the pattern
is classified as non-valid, probably originating from a incident proton and discarded. Connected patterns across Caliste
module boundries are treated as individual patterns for each module. A further rejection is performed if the sum over all
deposited energies within one pattern exceeds the MIP threshold.
The on-satellite LED data processing involves a more complex pixel pattern and MIP detection algorithm. Patterns with
totalling energy deposits above a certain threshold (here the maximum of the LED range) or N greater four are discarded.
This also includes all types of tracks. Furthermore the patterns are checked against a validation mask, which excludes
patterns with non X-ray like energy distribution (Strüder, L et al, 2000). The allowed patterns can be seen in Figure 6.1.
If a non-valid pattern ist found, we imply that at least one pixel in the current frame is background contaminated and
so most likely also the total frame. In this case the whole frame is dropped. The procedure has neglible effects on the
detector dead time (below 1%), which is clearly dominated by the AC induced downtime 1.
As a possible on ground treatment the HED data is also run through the LED pattern an MIP detection.
6.1 Normalization
At each step of data treatment, detailed spectra and pixel maps of the data are produced. This allows to directly anaylse
the effects of each analysis step on the background. To obtain the spectra and resulting background count rates the
number of residue detector events has to be renormalized. To normalize to a count rate of ”cts /keV /s /cm2” we need
the simulated time, the detector area and the detector energy range. The last two are directly given by the specifications
as the detector area A= 64cm2 and the detector energy range∆ELED = 0.5− 20keV or∆EHED = 5− 100keV. The simulated
time can be calculated from the input flux and the source geometry:
n|E2
E1= A · tsim ·
∫ E2
E1
dN(E)
dE= A · t · 2.32
protons
cm2 s(6.1)
where n|E2
E1is the number of source protons emited during the simulated time t from an area A.
Since our inner source sphere is formed by the emmision cones originating from the outer sphere it will also be hit
by every primary. The incident flux would then seem to originate from the surface of the inner sphere which is given
by Asph,inner = 4πr2. It’s radius can be calculated from the radius R of the outer sphere and the opening angle α of the
emission cones: r = R · sinα.
Equation 6.1 is normalized to 4π emittance. Since we only emit inside the small sphere we devide the equation by 4π
which yields the flux per solid angle. The emittance solid angle of the small sphere is then given by Ω = π ∗ sin2α= π
1 for LED: AC-frames/total Frames, for HED AC-event/total events
28
with α for a hemisphere being π/2, to which we have to renormalize the flux. Sullivan (1971) identifies this as the
geometrical factor G = π · Asource. The number of particles traversing the real world detector is then given by
C = Φ · G (6.2)
with Φ being the integrated flux per steradian (2.32/4π protons/(cm2 s sr)) (Santin, 2007). The simulated time t is
then given by
t =n|
E2
E1
C=
n|E2
E1
Φ · 4π2R2sin2α·(6.3)
which together with the prior calculations yields
t =n|
E2
E1
Φ · 7826.87 cm2(6.4)
when using a source sphere of radius 50m and a cone opening angle of 0.01 rad. For protons we can calculate Φ =2.32
protons/(cm2 · s) while for photons integration of the source spectrum yields Φ =197.2 photons/(cm2 · s) (Chipaux et al.,
2008).
The normalisation used prior to March 2009 did not include the mentioned solid angle corrections but instead assumed
true 4π emission. Because of this all background rates prior to this date have to be devided by 4 to obtain correctly
normalized rates. If pattern analysis is included in the background calculations, theses should be redone because a
longer simulated time also influences the pattern distribution.
29
Figure 6.1: Schematic of the SIMBOL-X analysis routines
Figure 6.2: Pixel patterns used for SIMBOL-X framed analysis as given by Strüder, L et al (2000)
30
7 Results
The results of this work can be devided into three categories: optimisation of the baseline geometry, optimisation of
backend data processing and verification of the results. Optimisation may include changes to the geometry and to
standard analysis, while verification with the other colaboration members is carried out with an unchange geometry and
simplified analyis.
7.1 Verification
Continuing the work done by Christian Klose the first step was to replicate his previous results with his unchanged
code basis. After finding the right parameters his results could be replicated within 5% accuracy. As a next step the
simulation geometry was updated to the then current CVS version 5, which featured an updated anti-coincidence layout
and included first models for the support structures. These new results were then compared with the results of the
collaboration partners at Saclay and Tübingen (Table 7.1. Again an overall agreement with a maximum deviation of 40%
for the HED and 26% for the LED was found. The discrepancies stem from updated analysis approaches at CEA and IAAT.
Table 7.1: Comparsion of SIMBOLX 5 geometry Results. IAAT and CEA values from Bologna conference in May 2008, TUD
Results from August 2008. All values are given in units of 10−4ctss−1keV−1cm−1 on non-pixelized detectors for
proton primaries.The AC was set to 300 keV
TUD CES IAAT
LED 4.3 4.7 5.8
HED 5.3 5.9 8.9
After these verification steps further optimisation of the simulation routines was started. While previous analysis was
on a non-pixelized per-event basis this was changed to a per-pixel basis. Pixel events are now grouped in LED-frames
and HED-timing periods as described in detail in Section 5.2. At the same time the simulation code was modified to
enable parallization and increase overall speed (Figure 5.4. This new code and analysis base is incompatible to previous
simulation analysis, which is why a verification against the pre-optimisation results was omitted. Instead is was chosen
that each collaboration partner should move to the more realisic pixel analysis so that result verifications against each
other can be made. This step was completed with geometry version 6, which quickly evolved to 6.1, now including a
updated platform material a different collimator flange and minor bugfixes. Result comparisions with this new version
and the updated analysis version are currently underway. The results are summarized in Table 7.2. As can be seen an
agreement has not yet been fully reached and not all groups have updated their analysis routines to include full back-end
treatment. A comparision of the unprocessed event numbers between TUD and IAAT shows for 107 primary protons LED
rates of 56598 frames compared to 57369 frames on a geometry without collimator an prior to any back-end treatment.
This implies that post analysis has not fully converged while the simulations are in good agreement.
Table 7.3 gives the above count rates normalized including the additional factor of 4 as decribed in Chapter 6 along
with the current CXB-photon induced background rates where available. One can see that these are close to the sci-
ence requirement ranges (see Table 4.1). Also the satellite platform and collimator have great influence on the overall
countrates. This is discussed in more detail in the following optimisation section.
7.2 Optimisation
The main goal of these simulations is of course to optimize the focal plane layout with respect to background rates
and AC downtime. One important step was done with geometry version 6 which introduced a more compact AC setup
minimizing the sensitive volume while still enclosing the detectors. This reduces the false AC counts, thereby reducing
the downtime.
Ways to reduce the countrate are also being investigated. A comparision of this work and results by Chris Tenzer
(Table 7.2) show that the platform has signifcant influence on the HED and LED count rates. This is not unusual,
since the platform, which models the satellite auxilary structure is of high mass and volume (see Figure 4.4), which
readily produces secondaries which then increase the high energy particle background. As can be seen in Figure 7.1 the
31
Table 7.2: Current proton background rate results for 6.1 geometry. TUD results are current normalisation multiplied by
4 (see 6) and with HED AC time of 50µs. Results are as of Feb. 10th 2009. All count rates are given in units of
10−4cts/s/cm2/keV. Values in parathesis are for new normalistion.
Setup no meca-support, no
top-support
no meca-support, no
top-support, no plat-
form
no meca-support, no
top-support, no plat-
form, no collimatorInstitution TUD IAAT CEA TUD IAAT CEA TUD IAAT CEA
Primaries 106 107 ? 106 107 ? 106 107 ?
AC Threshold 1MeV 1MeV 1MeV 1MeV 1MeV 1MeV 1MeV 1MeV 1MeV
AC Deadtime [%] (18.7) 54 55 - (18.5) 53 55 (17.6) 52 53 -
LED CR before AC 700 - - 624 - - 536 - -
LED CR after AC 21 - 6.3 8.8 - - 1.76 - -
LED CR after Pattern & MIP 8.1 3.1 - 2.92 1.68 - 1.75 - -
HED CR before AC 876 246 - 840 230 - 700 - -
HED CR after AC 19.9 8.2 7.1 13.2 5.6 - 2.52 - -
HED CR with Level 1 13.3 - - 8.0 - - 2.04 - -
HED CR with Pattern 10.6 - - 6.2 - - 1.79 - -
Table 7.3: Current count rates from TUD with new normalisation. All count rates are given in 10−4cts/s/cm2/keV. AC
Threshold is set to 1 MeV. Reliable CXB rates are not yet available. Count rates given for simulations with
electric Field are work in progress.
no meca-support, no
top-support
no meca-support,
no top-support,
no platform
no meca-support,
no top-support,
no platform, no
collimator
no meca-support,
no top-support,
20 keV E-field
above LED +Al-
layer106 protons 107 photons 106 protons 106 protons 105 protons
LED Deadtime [%] 18.8 - 18.5 17.6 18.8
LED CR before AC 175.8 - 155.8 134.2 176
LED CR after AC 5.25±0.88 - 2.19±0.67 0.44±0.25 7.29 ± 3.2
LED CR after Pat. & MIP 2.04±0.55 - 0.73±0.33 0.44±0.25 2.91 ± 2.0
HED CR before AC 219 - 209.5 175.8 244
HED CR after AC 4.97±0.39 0.254 ± 0.254 3.35±0.32 0.63±0.14 3.59 ± 1.04
HED CR after Level 1 3.32±0.32 - 1.95±0.24 0.51±0.12 2.7 ± 0.89
HED after Pat. 2.67±0.28 - 1.56±0.220. 0.45±0.12 2.69 ± 0.9
HED Deadtime [%] 7.8 0.02 7.7 7.0 7.8
component from the platform originates mostly from electrons ionizing off the aluminum. In the further proceeding it
should be investigated how the positioning of the platform, i.e at one side of the detector, influences the background.
The largest background component in the LED are electrons, either as primaries or created by interactions of other
particles within the Silicon. This can be deducted from the corresponding spectra in Figure 7.1(a) and corresponding
figures in the appendix. For further optimisation it is necessary to have an understanding where these electrons originate
and which processes are causing them. A quantitive analysis was done by recording the primordal electrons along with
their creation region and their creation process. The particle type recorded is interchangeable so future analysis of all
important particles is possible.
As shown in Figure 7.1 these electrons mostly originate from within the detector material, by ionisation of silicon.
Electrons from one pixel are relocated to a neighbouring pixel. This results in invalid patterns which are efficiently
removed by pattern analysis as shown in Figure 7.1(e). After backend processing the electrons originating from the
collimator and shielding parts gain in importance to the background , which is not unusual since these are less likely to
be detected by the AC and pattern correction. This is supported by the corrected spectrum shown in the figure where
most electrons resulting from detector ionisation have been removed. It is further supported by the background rates as
given in the previous section which decrease when removing platform and collimator. The layout of the collimator and
platform should therefor be reevaluated for optimal design.
32
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
(a) LED spectra without AC or post analysis,106
primary protons, with collimator and platform. The
line emission qt 1.8 keV may originate from the
Si(1.84 keV) or Ta(1.79 keV) (National Institute of
Standards and Technology (1996))
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
(b) LED spectra with AC and post analysis, 106
primary protons, with collimator and platform.
0 5 10 15
LED_pixelS
LED_pixelS
LED_pixelS
GShieldUpper_Sn_phys
CollimatorConeC_
GShieldUpperHole_Al_phys
GShieldUpper_Ta_phys
(c) Origin of the primary generated electrons
which hit the LED. AC corrected. Multiple entries
for one geometry part are due to parallisation
0 5 10 15 20 25
hLowEIoni
LowEnConversion
LowEnergyIoni
muIoni
eIoni
hIoni
LowEnCompton
(d) Main creation processes for electrons hitting
the LED. AC corrected
0 2 4 6 8
LED_pixelS
LED_pixelS
Plattform
GShieldUpper_Ta_phys
ACLowerLateral_2_phys
CollimatorConeC_
HEDElectronics
(e) Origin of the primary generated electrons
which hit the LED. AC and pattern corrected. Mul-
tiple entries for one geometry part are due to par-
allisation
0 2 4 6 8 10 12
hLowEIoni
muIoni
eIoni
LowEnergyIoni
hIoni
LowEnCompton
LowEnConversion
(f) Main creation processes for electrons hitting
the LED. AC and pattern corrected
Figure 7.1: Origin of LED background
33
As can be seen in Figure 7.2 the electrons also dominate the HED spectrum. They mainly originate from the above
lying LED by ionisation and Compton-effect in the Silicon. It should be investigated if there are deflection possibilities
for these electrons such as a conductive layer between the detectors.
Figure 7.2(a) also shows that there is line emission at 4-5, 7-8, 26 and 31 keV. These lines can be attributed to
Sn(muliple between 4-5 keV), Cu (Kα= 8.05 keV), Ta,(multiple between 7-8 keV), Sn (multiple around 26 keV and 30
keV). As the figure shows these prominent lines disappear after AC treatment which implies that the particles responsible
are energetic enough to also trigger the AC. If all lines are supressed after AC filtering has not yet been investigated since
it implies having higher event counts for better statistics. A prolonged simulation run with several 107 primary protons
should be conducted in order to settle this issue.
It was also tested how different HED AC-times influence the countrate. As shown in Figure 7.3 increasing the AC-time
almost proportionaly lowers the count rates. Dead times of around 15% are still tolerable, which would allow using an
AC-time of 100µs resulting in a HED countrate of 4.58±0.37×10−4cts/keV/s/cm2 after AC.
A further optimisation test involved the placement of an electrical field of 20 keV/cm and a thin 100 nm layer of
aluminum above the LED. Such an electrical field could for instance be realized by applying a high positive potential
to the structures surrounding the detectors. Even if all the electrons hitting the LED within it’s detection range where
drained by the field the current would be very small ( ≈ 10.56 e−/s or 1.7×10−18A). As shown in Table 7.3 the influence
on the LED and HED countrates are small, with differences presumably stemming from the poorer statistics.
7.3 Delayed Background
Additionally to the direct background component which includes all secondary particles which occur within a few frames
or timing periods of an incident primary particle the delayed component due to radioactive decays was simulated. While
the materials used for satellite construction will be selected for minimal activation, cosmic ray hits may activate materials
of the satellite structure after launch. GEANT4 is capable of simulating these delayed decays but can not be used to
simulate radioactive equilibrium. While this doesn’t allow a quantative simulation of the total additional background due
to activation, estimates on the activation rate and importance of the different satellite materials can be made. It is also
possible to test the efficiency of the AC setup on delayed events from short-lived isotopes.
The plots shown are generated from data taken out of the IDL analysis pipeline after AC treatment. The data is not
corrected to the detector energy ranges and shows the delay between primary particle creation and hits registered in the
detectors. The delayed component starts at approximately 10−3s. A can be seen in Figure 7.3 the AC is quite efficient
in reducing delayed events, especially from isotopes with long half-life times. The complilation of activation isotopes
for SIMBOL-X by Klose (2006) shows that most decay via β-decays with energies above the AC-trigger of 1MeV, and are
therewith rejected.
With the data of this compilation it was also tried to identify some of the isotopes by their half-life times. Figure
7.3 shows the non-corrected background along with decay peaks for the distinguishable isotopes 5928Ni (7.5·104y), 60
27Co
(5.3y), 6832
Ge (288d) and 18273
Ta. The remaining ”continuum’ consists of products of faster decaying isotopes whose peaks
are not destinguishable. The figure shows that no single isotope clearly dominates the spectrum but instead a variaty of
isotopes is of importance to the background. This leads to the conclusion that on-orbit activation is not limited to specific
parts of the satellite structure. Furthermore without modeling equilibrium no definitive answer on the importance of
the delayed component for the total background can be given. Still Figure 7.3 suggests that the non-delayed component
is larger by orders of magnitude, especially if AC treatment is taken into account. This is supported by the ratios of
direct (t ≤ 10−3s)) to delayed background (t > 10−3
s)): for the LED these are 0.62% without and 2.5% with AC, for
the HED the values are 0.21% and 0.97%. Comparing the countrates with and without radioactive decay also supports
this conclusion: the LED countrate with decays is 1.69±0.22·10−4cts/s/cm2/keV as opposed to 2.04±0.55 without, both
after pattern and MIP detection. The HED countrate increases from 4.97±0.39 to 6.56±0.2·10−4cts/s/cm2/keV after AC
corrections. The insignificant reduction of the LED countrate is caused by additional AC triggers within one frame from
short-lived Isotopes, resulting in an increase of LED downtime from 18.8% to 18.9%. Contrary to this the HED trigger
window is much smaller which is why additional delayed AC triggers do not decrease the countrate and the downtime
stays the same at 7.8% for both with and without radioactive decays enabled.
34
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
(a) HED spectra without AC or post analysis, 106
primary protons, with collimator and platform. The
line emission qt 1.8 keV may originate from the
Si(1.84 keV) or Ta(1.79 keV) (National Institute of
Standards and Technology, 1996)
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
(b) HED spectra with AC and post analysis, 106
primary protons, with collimator and platform.
0 50 100 150 200 250
LED_pixelS
LED_pixelS
GShieldLower_Ta_phys
LED_pixelS
HEDElectronics
GShieldUpper_Sn_phys
LED_pixel
(c) Origin of the primary generated electrons
which hit the HED. AC corrected. Multiple entries
for one geometry part are due to parallisation
0 20 40 60 80
LowEnCompton
LowEnergyIoni
hLowEIoni
hIoni
LowEnPhotoElec
LowEnConversion
muIoni
(d) Main creation processes for electrons hitting
the HED. AC corrected
0 20 40 60 80
LED_pixelS
LED_pixelS
GShieldLower_Ta_phys
LED_pixelS
GShieldUpper_Sn_phys
ACUpperRoof_2_phys
Detector volume
(e) Origin of the primary generated electrons
which hit the HED. AC and pattern corrected. Mul-
tiple entries for one geometry part are due to par-
allisation
0 10 20 30
LowEnCompton
LowEnergyIoni
LowEnPhotoElec
LowEnConversion
hIoni
hLowEIoni
muIoni
(f) Main creation processes for electrons hitting
the HED. AC and pattern corrected
Figure 7.2: Origin of HED background
35
cts/sec/keV/cm²
5
10
15
45
50
55
60
HED AC Time [us]
0 100 200 300 400 500 600
Figure 7.3: The HED AC-time influence on the count rate is shown. The black line shows the HED count rate after AC, the
red line shows the corresponding downtime in % of total. Countrates are given in units of 10−4cts/keV/s/cm2
for a geometry including collimator and satellite platform.
10−10 100 1010 1020 1030
time [s]
10−8
10−7
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
/pro
ton]
Figure 7.4: Background components in HED (within energy range). Black is the uncorrected background, green after AC
treatment.
Counts
10-1
100
101
102
103
104
105
105
Decay Time [s]
10-5
100
105
1010
1015
1015
Ni
Co
Zn
Ta
direct hits non resolvable short and mid-lived
Figure 7.5: Background components in HED. The uncorrected background is shown along with peak locations of distin-
guishable isotopes. The short- and midlived isotopes can not be resolved.
36
8 Outlook
As shown in Chapter 7 full agreement for the current geometry version still has to be reached. This should be completed
within the next month. In a next step the delayed background should be evaluated in more detail. Since GEANT4 is not
capable of modeling radioactive equilibrium for long term activation other tools should be used for this after identifying
the most important isotopes. Also up to now we are modeling for just one orbital position and fluxes near the solar
maximum. For a more complete understanding of the background it is necessary to model other critical orbital phases.
The code basis developed as part of this work is modular enough that only small adjustments would be needed in the
input spectra.
Since SIMBOL-X is a precessor to the planned IXO mission (Kunieda, Parmar and White, 2008) another goal is to model
the IXO background once a geometry becomes available. Further performance optimisation may also be carried out with
the long term goal of providing a fast toolkit which allows to model background for given SIMBOL-X observations.
Additionally to the already implemented multi-cpu/multi-client parallelisation the possibility of porting the simulation
part to graphics (GPU) hardware, which would feature 100s of processing units on one board, should be verified. The
PS3 Gravity Grid has shown that this may be a very inexpensive way of obtaining processing power in the multi-petaflops
range (Khanna, 2009).
37
9 Summary
The work done within the scope of this thesis provides a solid simulation and analysis basis for further background
optimisation of the SIMBOL-X focal plane geometry. It was shown that current geometry setup is already close to the
scientific requirements for the observatory, even though result evaluation throughout the group is still required for the
newest geometry version. Results presented in the optimisation section lead to the conclusion that there is room for
further optimisations, less in the detector and AC geometry themselves but in the positioning of the auxilary satellite
structures and the setup of the colimator. The results for the delayed background implicate that most decays will be
detected by the anti-coincidence system. This makes it necessary to simulate the decay equilibrium with a non-GEANT4
toolkit to see how acummulated activation will influence the dead time of the detectors. Judging from the current
progress, the background goals for SIMBOL-X seem achievable. Confirming this in the near future would be an important
step concerning the feasibility of the SIMBOL-X project.
38
.
39
40
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43
44
A SIMBOL-X Simulation Executable Parameters
The following table summarizes the available parameters for the SIMBOL-X simulation
Parameter Meaning necessary for: SimbolX ParSimbolX
-help output help
-path X the output path for the hit data X X
-fn X filename prefix for output X X
-plm X Physics list: Fixed to HighEnergy X X
-dgm X Geometry mode : Fixed to SimbX X X
-a for automated mode X
-n X number of primaries X
-part X primary particle: proton(default) or gamma
-efield turn on eField
–TOPC-aggregated-tasks=XXX events to process before calling mas-
ter
X
When running ParSimbolX one also has to take care that there is a procgroup file in the directionary from which the
simulation is called. This file should look like the following.
l o c a l 0
l o c a l h o s t 1 − >slave1 . out
l o c a l h o s t 1 − >slave2 . out
#l o c a l h o s t 1 − >s l a v e 3 . out
#skpc5 1 − >s l a v e 8 . out
# The g e n e r a l format i s tha t " l o c a l 0" ( r e q u i r e d ) i m p l i e s c r e a t i o n o f a master .
# Otherwise t h e r e i s one l i n e per s l a v e .
# The f i r s t f i e l d i s the hostname or l o c a l h o s t ( in a form v a l i d f o r " r sh " )
# I f you p r e f e r s sh over rsh , then ( e . g . in c sh ) : s e t e n v RSH ssh
# The second f i e l d , 1 , i s o b l i g a t o r y .
# The t h i r d f i e l d i s an a b s o l u t e or r e l a t i v e pathname ( e . g . : . / XXX or . . / XXX)
# o f the b inary . A r e l a t i v e pathname i s appended to path o f the b inary
# on master . The s l a v e p r o c e s s w i l l e x e c u t e in the same d i r e c t o r y
# as the c u r r e n t working d i r e c t o r y o f the master , i f p o s s i b l e .
# Otherwise , the s l a v e w i l l e x e c u t e in the home d i r e c t o r y .
# I f the t h i r d f i e l d i s ‘− ’ , then the command l i n e ( i n c l u d i n g arguments )
# f o r tha t s l a v e w i l l be the same as on the master .
# Any a d d i t i o n a l f i e l d s ( f ou r th and beyond ) are appended to the
# command l i n e f o r tha t s l a v e on ly .
. . .
45
B Detailed Results
46
with Sat and Col - Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
LED
counts
0
1
2
3
4
5
6
7
0 32 64 96 128pixel
100120140160180200
col.
coun
ts100120140160180200row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
02468
col.
coun
ts0 2 4 6 810row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
01234
col.
coun
ts0 1 2 3 4row counts
0
32
64
96
128
pixe
l
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
LED
Hits 18681
AC Energy[eV] 1000000
AC Off CR 0.017580
Low Cts [cts/s] 260
LatLow Cts [cts/s] 603
LatUp Cts [cts/s] 1044
Up Cts [cts/s] 1448
AC counts [cts/s] 1462
Hits after AC 351
AC Downtime 0.187
AC only CR 0.000525
[cts/(keV s cm2)]+- 0.0000875
HED level One 0.000000
[cts/(keV s cm2)]+- 0.0000000
PatDet Downtime 0.001
AC + Pat Downtime 0.188
AC + Pat Countrate 0.0002042
[cts/(keV s cm2)]+- 0.000055
Output name: thesisSX61SatColNewAng Primaries:
1000000 protons - For comparing results with group. MECA
and Aluminum-Top support commented. Level 1 correction
for HED is N>3 correction. For LED full pattern and MIP
detection is used. GPS ang type cos is used.
LED
Total MIPS Non-Valid Valid
Sing. 132( 0.581) 0( 0.000) 8( 0.061) 124( 0.939)
Doub. 63( 0.278) 61( 0.968) 0( 0.000) 2( 0.032)
Trip. 20( 0.088) 20( 1.000) 0( 0.000) 0( 0.000)
Quadr. 5( 0.022) 5( 1.000) 0( 0.000) 0( 0.000)
N>4 7( 0.031) 7( 1.000) 0( 0.000) 0( 0.000)
47
with Sat and Col - Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
HED
counts
0134678
10111314
0 32 64 96 128pixel
300350400450500
col.
coun
ts400420440460480500row counts
0
32
64
96
128
pixe
l
counts
0
1
2
3
0 32 64 96 128pixel
05
101520
col.
coun
ts0 5 10 15row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
02468
col.
coun
ts0 2 4 6row counts
0
32
64
96
128
pixe
l
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
HED
Hits 60599
AC Energy[eV] 1000000
AC Off CR 0.021995
Low Cts [cts/s] 260
LatLow Cts [cts/s] 603
LatUp Cts [cts/s] 1044
Up Cts [cts/s] 1448
AC counts [cts/s] 1562
Hits after AC 874
AC Downtime 0.078
AC only CR 0.000497
[cts/(keV s cm2)]+- 0.0000386
HED level One 0.000332
[cts/(keV s cm2)]+- 0.0000316
PatDet Downtime 0.000
AC + Pat Downtime 0.008
AC + Pat Countrate 0.0002665
[cts/(keV s cm2)]+- 0.000028
Output name: thesisSX61SatColNewAng Primaries:
1000000 protons - For comparing results with group. MECA
and Aluminum-Top support commented. Level 1 correction
for HED is N>3 correction. For LED full pattern and MIP
detection is used. GPS ang type cos is used.
HED 1. col fraction of all, others frac. o. type
Total MIPS Non-Valid Valid
Sing. 335( 0.598) 6( 0.018) 43( 0.128) 286( 0.854)
Doub. 105( 0.188) 76( 0.724) 2( 0.019) 27( 0.257)
Trip. 63( 0.113) 61( 0.968) 1( 0.016) 1( 0.016)
Quadr. 26( 0.046) 26( 1.000) 0( 0.000) 0( 0.000)
N>4 31( 0.055) 31( 1.000) 0( 0.000) 0( 0.000)
48
with Sat without Col - Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
LED
counts
01
2
3
4
5
6
78
0 32 64 96 128pixel
100120140160180200
col.
coun
ts100120140160180row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
0246
col.
coun
ts0 2 4 6 8row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
0123
col.
coun
ts0.00.51.01.52.0row counts
0
32
64
96
128
pixe
l
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
LED
Hits 17975
AC Energy[eV] 1000000
AC Off CR 0.015581
Low Cts [cts/s] 256
LatLow Cts [cts/s] 594
LatUp Cts [cts/s] 1016
Up Cts [cts/s] 1438
AC counts [cts/s] 1446
Hits after AC 157
AC Downtime 0.185
AC only CR 0.000219
[cts/(keV s cm2)]+- 0.0000565
HED level One 0.000000
[cts/(keV s cm2)]+- 0.0000000
PatDet Downtime 0.000
AC + Pat Downtime 0.186
AC + Pat Countrate 0.0000729
[cts/(keV s cm2)]+- 0.000033
Output name: thesisSX61SatnoColNewAng Primaries:
1000000 protons - For comparing results with group.
Collimator excluded. MECA and Aluminum-Top support
commented. Level 1 correction for HED is N>3 correction.
For LED full pattern and MIP detection is used. GPS ang
type cos is used.
LED
Total MIPS Non-Valid Valid
Sing. 42( 0.467) 0( 0.000) 4( 0.095) 38( 0.905)
Doub. 24( 0.267) 23( 0.958) 0( 0.000) 1( 0.042)
Trip. 18( 0.200) 18( 1.000) 0( 0.000) 0( 0.000)
Quadr. 2( 0.022) 2( 1.000) 0( 0.000) 0( 0.000)
N>4 4( 0.044) 4( 1.000) 0( 0.000) 0( 0.000)
49
with Sat without Col - Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
HED
counts
023568
1011131416
0 32 64 96 128pixel
300400500600
col.
coun
ts300350400450500row counts
0
32
64
96
128
pixe
l
counts
0
1
2
3
0 32 64 96 128pixel
05
1015
col.
coun
ts0 5 10 15row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
012345
col.
coun
ts0 1 2 3 4 5row counts
0
32
64
96
128
pixe
l
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
HED
Hits 59311
AC Energy[eV] 1000000
AC Off CR 0.020950
Low Cts [cts/s] 256
LatLow Cts [cts/s] 594
LatUp Cts [cts/s] 1016
Up Cts [cts/s] 1438
AC counts [cts/s] 1545
Hits after AC 602
AC Downtime 0.077
AC only CR 0.000335
[cts/(keV s cm2)]+- 0.0000317
HED level One 0.000195
[cts/(keV s cm2)]+- 0.0000241
PatDet Downtime 0.000
AC + Pat Downtime 0.008
AC + Pat Countrate 0.0001557
[cts/(keV s cm2)]+- 0.000022
Output name: thesisSX61SatnoColNewAng Primaries:
1000000 protons - For comparing results with group.
Collimator excluded. MECA and Aluminum-Top support
commented. Level 1 correction for HED is N>3 correction.
For LED full pattern and MIP detection is used. GPS ang
type cos is used.
HED 1. col fraction of all, others frac. o. type
Total MIPS Non-Valid Valid
Sing. 216( 0.573) 4( 0.019) 28( 0.130) 184( 0.852)
Doub. 73( 0.194) 54( 0.740) 2( 0.027) 17( 0.233)
Trip. 40( 0.106) 38( 0.950) 1( 0.025) 1( 0.025)
Quadr. 21( 0.056) 21( 1.000) 0( 0.000) 0( 0.000)
N>4 27( 0.072) 27( 1.000) 0( 0.000) 0( 0.000)
50
Without Sat and Col - Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
LED
counts
01
2
3
4
5
6
78
0 32 64 96 128pixel
050
100150
col.
coun
ts0 50100150row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
0123
col.
coun
ts0 2 4 6row counts
0
32
64
96
128
pixe
l
counts
0
1
0 32 64 96 128pixel
0.00.20.40.60.81.0
col.
coun
ts0.00.20.40.60.81.0row counts
0
32
64
96
128
pixe
l
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
LED
Hits 16485
AC Energy[eV] 1000000
AC Off CR 0.013422
Low Cts [cts/s] 240
LatLow Cts [cts/s] 560
LatUp Cts [cts/s] 968
Up Cts [cts/s] 1362
AC counts [cts/s] 1375
Hits after AC 62
AC Downtime 0.176
AC only CR 0.000044
[cts/(keV s cm2)]+- 0.0000253
HED level One 0.000000
[cts/(keV s cm2)]+- 0.0000000
PatDet Downtime 0.000
AC + Pat Downtime 0.176
AC + Pat Countrate 0.0000438
[cts/(keV s cm2)]+- 0.000025
Output name: thesisSX61noSatnoColNewAng Primaries:
1000000 protons - For comparing results with group.
Satellite platform and collimator excluded. MECA and
Aluminum-Top support commented. Level 1 correction for
HED is N>3 correction. For LED full pattern and MIP
detection is used. GPS ang type cos is used.
LED
Total MIPS Non-Valid Valid
Sing. 14( 0.412) 0( 0.000) 0( 0.000) 14( 1.000)
Doub. 11( 0.324) 11( 1.000) 0( 0.000) 0( 0.000)
Trip. 7( 0.206) 7( 1.000) 0( 0.000) 0( 0.000)
Quadr. 0( 0.000) 0( -NaN) 0( -NaN) 0( -NaN)
N>4 2( 0.059) 2( 1.000) 0( 0.000) 0( 0.000)
51
Without Sat and Col - Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
HED
counts
0134678
10111314
0 32 64 96 128pixel
300400500600700800
col.
coun
ts300400500600row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
012345
col.
coun
ts0 2 4 6 8row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
0123
col.
coun
ts0 1 2 3 4row counts
0
32
64
96
128
pixe
l
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
HED
Hits 53072
AC Energy[eV] 1000000
AC Off CR 0.017584
Low Cts [cts/s] 240
LatLow Cts [cts/s] 560
LatUp Cts [cts/s] 968
Up Cts [cts/s] 1362
AC counts [cts/s] 1465
Hits after AC 167
AC Downtime 0.007
AC only CR 0.000063
[cts/(keV s cm2)]+- 0.0000137
HED level One 0.000051
[cts/(keV s cm2)]+- 0.0000123
PatDet Downtime 0.000
AC + Pat Downtime 0.007
AC + Pat Countrate 0.0000449
[cts/(keV s cm2)]+- 0.000012
Output name: thesisSX61noSatnoColNewAng Primaries:
1000000 protons - For comparing results with group.
Satellite platform and collimator excluded. MECA and
Aluminum-Top support commented. Level 1 correction for
HED is N>3 correction. For LED full pattern and MIP
detection is used. GPS ang type cos is used.
HED 1. col fraction of all, others frac. o. type
Total MIPS Non-Valid Valid
Sing. 52( 0.525) 0( 0.000) 9( 0.173) 43( 0.827)
Doub. 21( 0.212) 17( 0.810) 0( 0.000) 4( 0.190)
Trip. 10( 0.101) 10( 1.000) 0( 0.000) 0( 0.000)
Quadr. 8( 0.081) 8( 1.000) 0( 0.000) 0( 0.000)
N>4 8( 0.081) 8( 1.000) 0( 0.000) 0( 0.000)
52
With RadDecay Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
LED
counts
02479
111315182022
0 32 64 96 128pixel
600800
10001200
col.
coun
ts60080010001200row counts
0
32
64
96
128
pixe
l
counts
0
1
2
3
4
5
6
0 32 64 96 128pixel
010203040
col.
coun
ts51015202530row counts
0
32
64
96
128
pixe
l
counts
0
1
2
3
0 32 64 96 128pixel
05
1015
col.
coun
ts0 5 10 15row counts
0
32
64
96
128
pixe
l
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
LED
Hits 95538
AC Energy[eV] 1000000
AC Off CR 0.017373
Low Cts [cts/s] 261
LatLow Cts [cts/s] 603
LatUp Cts [cts/s] 1050
Up Cts [cts/s] 1451
AC counts [cts/s] 1465
Hits after AC 1872
AC Downtime 0.188
AC only CR 0.000467
[cts/(keV s cm2)]+- 0.0000369
HED level One 0.000000
[cts/(keV s cm2)]+- 0.0000000
PatDet Downtime 0.001
AC + Pat Downtime 0.188
AC + Pat Countrate 0.0001692
[cts/(keV s cm2)]+- 0.000022
Output name: thesisSX61SatColNewAngRad Primaries:
5000000 protons - For comparing results with group. MECA
and Aluminum-Top support commented. Level 1 correction
for HED is N>3 correction. For LED full pattern and MIP
detection is used. GPS ang type cos is used. With delayed
background.
LED
Total MIPS Non-Valid Valid
Sing. 771( 0.613) 3( 0.004) 34( 0.044) 734( 0.952)
Doub. 346( 0.275) 330( 0.954) 1( 0.003) 15( 0.043)
Trip. 107( 0.085) 107( 1.000) 0( 0.000) 0( 0.000)
Quadr. 22( 0.017) 22( 1.000) 0( 0.000) 0( 0.000)
N>4 12( 0.010) 12( 1.000) 0( 0.000) 0( 0.000)
53
With RadDecay Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
HED
counts
048
1216202428323640
0 32 64 96 128pixel
200025003000350040004500
col.
coun
ts200025003000350040004500row counts
0
32
64
96
128
pixe
l
counts
0
1
2
3
4
5
0 32 64 96 128pixel
020406080
col.
coun
ts203040506070row counts
0
32
64
96
128
pixe
l
counts
0
1
2
3
4
5
0 32 64 96 128pixel
010203040
col.
coun
ts0 10203040row counts
0
32
64
96
128
pixe
l
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
HED
Hits 303253
AC Energy[eV] 1000000
AC Off CR 0.022245
Low Cts [cts/s] 261
LatLow Cts [cts/s] 603
LatUp Cts [cts/s] 1050
Up Cts [cts/s] 1451
AC counts [cts/s] 1567
Hits after AC 5302
AC Downtime 0.078
AC only CR 0.000656
[cts/(keV s cm2)]+- 0.0000198
HED level One 0.000423
[cts/(keV s cm2)]+- 0.0000159
PatDet Downtime 0.000
AC + Pat Downtime 0.008
AC + Pat Countrate 0.0003342
[cts/(keV s cm2)]+- 0.000014
Output name: thesisSX61SatColNewAngRad Primaries:
5000000 protons - For comparing results with group. MECA
and Aluminum-Top support commented. Level 1 correction
for HED is N>3 correction. For LED full pattern and MIP
detection is used. GPS ang type cos is used. With delayed
background.
HED 1. col fraction of all, others frac. o. type
Total MIPS Non-Valid Valid
Sing. 2404( 0.661) 34( 0.014) 286( 0.119) 2084( 0.867)
Doub. 691( 0.190) 457( 0.661) 22( 0.032) 212( 0.307)
Trip. 294( 0.081) 283( 0.963) 10( 0.034) 1( 0.003)
Quadr. 105( 0.029) 105( 1.000) 0( 0.000) 0( 0.000)
N>4 143( 0.039) 143( 1.000) 0( 0.000) 0( 0.000)
54
With E-Field - Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
LED
counts
0
1
2
3
0 32 64 96 128pixel
010203040
col.
coun
ts0 10203040row counts
0
32
64
96
128
pixe
l
counts
0
1
0 32 64 96 128pixel
0123
col.
coun
ts0 1 2 3 4row counts
0
32
64
96
128
pixe
l
counts
0
1
0 32 64 96 128pixel
0.00.51.01.52.0
col.
coun
ts0.00.51.01.52.0row counts
0
32
64
96
128
pixe
l
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 5 10 15 20Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
LED
Hits 2021
AC Energy[eV] 1000000
AC Off CR 0.017653
Low Cts [cts/s] 274
LatLow Cts [cts/s] 599
LatUp Cts [cts/s] 1052
Up Cts [cts/s] 1446
AC counts [cts/s] 1466
Hits after AC 43
AC Downtime 0.188
AC only CR 0.000729
[cts/(keV s cm2)]+- 0.0003262
HED level One 0.000000
[cts/(keV s cm2)]+- 0.0000000
PatDet Downtime 0.001
AC + Pat Downtime 0.189
AC + Pat Countrate 0.0002918
[cts/(keV s cm2)]+- 0.000206
Output name: thesisSX61SatColNewAngEfield Primaries:
100000 protons - For comparing results with group. MECA
and Aluminum-Top support commented. Level 1 Correction
for HED is Mip 3 correction. For LED full pattern and MIP
detection is used. GPS ang type cos is used. A electrical
Field of 20keV/cm is added above the LED
LED
Total MIPS Non-Valid Valid
Sing. 13( 0.464) 0( 0.000) 0( 0.000) 13( 1.000)
Doub. 14( 0.500) 13( 0.929) 0( 0.000) 1( 0.071)
Trip. 1( 0.036) 1( 1.000) 0( 0.000) 0( 0.000)
Quadr. 0( 0.000) 0( -NaN) 0( -NaN) 0( -NaN)
N>4 0( 0.000) 0( -NaN) 0( -NaN) 0( -NaN)
55
With E-Field - Anti-Coincidence Energy: 1000000 eVwithout corrections after AC after AC + pattern ana.
HED
counts
0
1
2
3
4
5
0 32 64 96 128pixel
020406080
100
col.
coun
ts20406080100row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
02468
col.
coun
ts0 1 2 3 4 5row counts
0
32
64
96
128
pixe
l
counts
0
1
2
0 32 64 96 128pixel
0.00.51.01.52.0
col.
coun
ts0 1 2 3row counts
0
32
64
96
128
pixe
l
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
0 20 40 60 80 100Energy [keV]
10−6
10−5
10−4
10−3
10−2
Cou
nt R
ate
[cts
keV−
1 cm
−2 s
−1 ]
ProtonsElectronsPositronsNeutronsGammaOthers
HED
Hits 6775
AC Energy[eV] 1000000
AC Off CR 0.024406
Low Cts [cts/s] 274
LatLow Cts [cts/s] 599
LatUp Cts [cts/s] 1052
Up Cts [cts/s] 1446
AC counts [cts/s] 1560
Hits after AC 93
AC Downtime 0.078
AC only CR 0.000359
[cts/(keV s cm2)]+- 0.0001037
HED level One 0.000270
[cts/(keV s cm2)]+- 0.0000898
PatDet Downtime 0.000
AC + Pat Downtime 0.078
AC + Pat Countrate 0.0002695
[cts/(keV s cm2)]+- 0.000090
Output name: thesisSX61SatColNewAngEfield Primaries:
100000 protons - For comparing results with group. MECA
and Aluminum-Top support commented. Level 1 Correction
for HED is Mip 3 correction. For LED full pattern and MIP
detection is used. GPS ang type cos is used. A electrical
Field of 20keV/cm is added above the LED
HED 1. col fraction of all, others frac. o. type
Total MIPS Non-Valid Valid
Sing. 31( 0.525) 0( 0.000) 10( 0.323) 21( 0.677)
Doub. 15( 0.254) 11( 0.733) 0( 0.000) 4( 0.267)
Trip. 9( 0.153) 9( 1.000) 0( 0.000) 0( 0.000)
Quadr. 1( 0.017) 1( 1.000) 0( 0.000) 0( 0.000)
N>4 3( 0.051) 3( 1.000) 0( 0.000) 0( 0.000)
56
Acknowledgements
I would especially like to thank Prof. Dr. Dr. hc./RUS Dieter
H. H. Hoffmann for giving me this interesting opportunity
of directly participating in the development of a new
satellite observatory.
Special thanks also go to Dr. Markus Kuster, who aided me
with numerous very helpful discussions and put a very great
amount of effort in commenting on this work.
I would also like to thank the other members of the
Astroparticle Physics Group: Annika Nord, Helena Krutsch,
Philipp Lange and Daniel Nowakowski for their helpful
comments and the often funny discussions.
Last but far from least I want to thank my parents for
allowing me to study without any greater worries (be it
financial or otherwise).
Gracias mi preciosa.
57