sergio ricciarini ~ infn firenze on behalf of pamela collaboration vertex 2006 15 th international...
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PAMELA Silicon Tracker experience and operation. Sergio Ricciarini ~ INFN Firenze on behalf of PAMELA collaboration Vertex 2006 15 th International Workshop on Vertex Detectors Perugia, 28 September 2006. Summary. Introduction. The PAMELA experiment. - PowerPoint PPT PresentationTRANSCRIPT
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Sergio Ricciarini~
INFN Firenze
on behalf of PAMELA collaboration
Vertex 200615th International Workshop on Vertex Detectors
Perugia, 28 September 2006
PAMELA Silicon Trackerexperience and operation
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Summary
Introduction.• The PAMELA experiment.
The magnetic spectrometer and silicon tracker.• Detectors and read-out electronics.
Tracker performances.• Preliminary analysis of a sample of data taken in flight.
Examples of events collected in flight by PAMELA.
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
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ITALY: • INFN Florence and Physics Department of Florence University • Istitute of Applied Physics “Nello Carrara”, Florence • INFN Bari and Physics Department of Bari University • INFN and Physics Department of Rome "Tor Vergata" • INFN Naples and Physics Department of Naples University • INFN Trieste and Physics Department of Trieste University • INFN National Laboratories, Frascati
GERMANY: Physics Department of Siegen University
SWEDEN: Royal Institute of Technology, Stockholm
RUSSIA: • Ioffe Physico-Technical Institute, St Petersburg • Cosmic Rays Laboratory, Moscow Engineering and Physics Institute, Moscow • Lab. of Solar and Cosmic Ray Physics, P.N. Lebedev Physical Institute, Moscow
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
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PAMELA experiment Main scientific objectives:
• antiparticles in cosmic rays; • search for antimatter and dark matter;• cosmic-ray propagation; • solar modulation, solar physics.
Mission overview:• on-board Resurs-DK1 Russian satellite, launched from Bajkonur (Kazakhstan) 15 June 2006;• quasi-polar orbit 70° inclination, 350-600 km altitude; • long expected duration (> 3 years);
efficient rejection of atmospheric background (albedo); high statistics, also at lower energies (geomagnetic effect).
Design goals for PAMELA performance:
sensitivity in anti-He/He ratio ~ 10-7
particle kin. energy range
antiproton 80 MeV - 190 GeV(expected ~ 104/year)
positron 50 MeV - 270 GeV(expected ~ 105/year)
electron 50 MeV - 400 GeV
proton 80 MeV - 700 GeV
e- + e+ up to 2 TeV
nuclei Z ≤ 6 100 MeV/n - 200 GeV/n
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
operational
launch (rest)
Al containerfilled with N2 at 1 atm2 mm thick window
Primaryproduction annihilation m() = 964 GeV(Ullio 1999)
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Main requirements: high-sensitivity antiparticle identification, precise momentum measure.
Time-Of-Flightplastic scintillator strips + PMT: trigger, albedo rejection; mass identification up to E ~ 1 GeV; charge identification from dE/dX.
Magnetic spectrometerwith microstrip Si tracker: charge sign and momentum from the curvature; charge identification from dE/dX.
Electromagnetic calorimeterW/Si sampling; 16.3 X0, 0.6 λI: discrimination e+ / p, e- / from shower topology; direct E measurement for e-.
PAMELA apparatus
max diameter: 102 cmheight: 130 cmweight: 470 kgpower: 355 W
p
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
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Magnetic spectrometer Permanent magnet (5 modules): • Nd-Fe-B alloy elements, residual magnetization 1.3 T; • Al frames, tower height 44.5 cm; • geometric factor 21.5 cm2 · sr; • Bx ~ Bz < 0.1 By ;
• 3-axis map: 70000 points, 5 mm pitch.
Tracking system (6 planes, 8.9 cm apart): • 3 independent ladders per plane: • 2 Si microstrip sensors per ladder: • double sided, with double metallization on ohmic view; • integrated capacitive coupling;
• FE electronics (VA1 chips) integrated on hybrid boards. Si sensors hybrids
l a d d e r
VA1 chips
Bmean = 0.43 TBmax = 0.48 T
AD
C b
oard
s
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
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Silicon detector ladder Sensor dimensions: 70.0 mm x 53.3 mm x 300 μm. Read-out:
• 1024 read-out channels per ladder view; • strip/electrode coupling ~ 20 pF/cm;• channel capacitance to ground: < 10 pF junction view, < 20 pF ohmic view.
Bias:• VY -VX = + 80 V fed through guard ring surrounding the strips.• Bias resistor: • junction: punch-through, > 50 MΩ; • ohmic: polysilicon, > 10 MΩ.
• Leakage current < 1 μA/sensor.
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
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VA1 chip Main features:
• 1.2 µm CMOS ASIC (CERN - Ideas, Norway);• 6.2 mm · 4.5 mm chip area; 47 μm input pad pitch;• ± 2 V power rails;• 128 low-noise charge preamplifiers;• shaping time set to 1 μs;• ± 300 mV differential output range.
Operating point:• chosen for optimal compromise;• power consumption 1.0 mW/channel total dissipation 37 W for 288 VA1 (36864 channels);• voltage gain 7.0 mV/fC output saturation at ~ 10 MIP.
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
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ADC stage:• 36 ADC sections, 1 ADC / ladder;• ADC are operated in parallel at 0.5 Msps;• event acquisition time 2.1 ms.
DSP stage:• 12 DSP on 2 boards, 1 DSP/view (ADSP2187L);• control logics on FPGA chips (A54SX);• typical data compression factor 15 ~ 4 kbyte/event;• typical compression time 1.1 ms.
Tracking system electronics General characteristics:
• segmentation/redundancy of power and functional sections;• devices qualified for radiation hardness (TID, SEE);• compact mechanical assembly;• limited total power consumption (63 W);• limited data bandwidth occupation (~ 10 Gbyte/day available).
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
flight data
calib
ratio
nphysics runphysics run
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Tracker performances
Preliminary analysis of a sample of data taken in ~12 hours of flight.• Data show that the tracking system is working nominally as expected.
Thermal environment.
Noise performances.
Cluster multiplicity and total signal.
Signal correlation between X and Y views.
Signal/noise.
Charge discrimination capabilities.
Spatial resolution.
Momentum resolution.
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
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Temperatures in flight After power-up temperature remains stable:
• < 1º C variations along orbit;• < 10º C difference between PAMELA off and on.
Heat from VA1 on hybrids radiated to the magnetic tower:• black IR absorbing painting on the walls;• heat released from magnetic tower to cooling loop (liquid iso-octane).
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
At power-up: 21º C(5000 s ~ 0.9 orbits)
8 days after power-up: 28º C(10000 s ~ 1.8 orbits)
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Noise in flight
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
Noise
Pedestal
Y view (DSP 3)
Noise performance is nominal, as can be seen for a typical calibration taken in flight. Y (ohmic) view has worse performance because of double metallization.
X view (DSP 6)
Y view (DSP 3)X view (DSP 6)
N ~ 4 ADC counts N ~ 9 ADC counts
flight data flight data
flight data flight data
yellow line = ground data average
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all planes
flight data - preliminary
all planes
flight data - preliminary
one plane
flight data - preliminaryone plane
Cluster characteristics
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
Cluster inclusion cuts: S > 7 N (seed), S > 4 N (neighbours).
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Signal/noise ratio, calculated as Σ(S/N) over the cluster channels.
This sample contains also non-MIP cosmic rays (He etc.). Typical average signal/noise measured at beam-test for orthogonally incident MIP:
56 (X view) 26 (Y view)
Signal/noise ratio
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
flight data - preliminary
plane 1
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Full charge discrimination capabilities studied with beam-test data (GSI Darmstadt, 2006).
• Fragmentation of 12C projectiles on different targets(Al, polyethylene).
Single-channel saturation at ~ 10 MIP affects B-C discrimination.
Charge discrimination
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
beam–test data
average cluster signal
even
ts Good H-He charge discrimination capability.
flight data - preliminary
He
H
magnetic rigidity R = |pc/Z|
all planes
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Spatial resolution Critically depends on the signal/noise ratio. Resolution for junction (X, bending) view determines the momentum measurement.
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
x = (2.77 ± 0.04) m
y = (13.1 ± 0.2) m
Best spatial resolution obtained with non-linear η algorithm for normally incident MIP.
Resolution measurement and sensor alignment done at the last beam test of the flight model with protons of known energies (CERN SPS, 2003).
Whole-tracker alignment checked with cosmic rays collected at ground level during final qualification tests (INFN Rome “Tor Vergata” laboratories, 2005).
In flight: alignment parameters will be checked with high-energy electrons after collecting a sufficient statistical sample (at least 3 months of data taking).
Beam-test data - orthogonally incident MIP
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Momentum resolution Measured at beam test with protons of known momentum (CERN SPS, 2003). In flight cross-check with E
measured by calorimeterfor high-energy electrons.
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
MDR ~ 1 TVmult. scatt. spat. resol. X
magnetic rigidity R = |pc/Z|magnetic deflection η = 1/R = |Z/pc|
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S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
Flight data:10 GV
electronwith electr. shower
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S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
Flight data:1.56 GVpositron
with electr. shower
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S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
Flight data:36 GV proton
with hadronic shower
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S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
Flight data:18 GV
antiprotonwithout shower
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S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
Flight data:9.7 GV
He nucleuswithout shower
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Conclusions
PAMELA is taking data since 11 July 2006.• Up to now >900 Gbyte of data downlinked to ground.• Acquired ~ 90 · 106 events.• Apparatus operating also within radiation belts (SAA).
Magnetic spectrometer on-flight performances are nominal.
Data processing and analysis tools have been developed and used; they are now being finalized.
Next step: systematic data analysis.• Precise determination of detector characteristics.• Application to physics research items.
S. Ricciarini – PAMELA Silicon Tracker – Vertex 2006, Perugia 28 September 2006
trigger rate