gamma based positron source options for ilc klaus floettmann desy
DESCRIPTION
GAMMA BASED POSITRON SOURCE OPTIONS FOR ILC Klaus Floettmann DESY. Contents:. Basics of gamma based sources Status of work Who wants to Do What?. Conventional vs. Gamma Based Source. Photons 10-20 MeV. Primary Beam. Capture Optics. Target. thin target: 0.4 X 0. - PowerPoint PPT PresentationTRANSCRIPT
K. Floettmann KEK, Nov. 13-15, 2004
GAMMA BASED POSITRON SOURCE OPTIONS FOR ILC
Klaus Floettmann
DESY
K. Floettmann KEK, Nov. 13-15, 2004
Contents:
§ Basics of gamma based sources
§ Status of work
§ Who wants to Do What?
K. Floettmann KEK, Nov. 13-15, 2004
Conventional vs. Gamma Based Source
Target
Photons 10-20 MeV
Electrons 0.1-10 GeV
Primary Beam Capture Optics
thin target: 0.4 X0
thick target: 4-6 X0
K. Floettmann KEK, Nov. 13-15, 2004
Parameters of existing and planed positron sources
rep rate# of bunches per pulse
# of positrons per bunch
# of positrons per pulse
TESLA/ILC 5 Hz 2820 2 · 1010 5.6 · 1013
NLC 120 Hz 192 0.75 · 1010 1.4 · 1012
SLC 120 Hz 1 5 · 1010 5 · 1010
DESY positron source
50 Hz 1 1.5 · 109 1.5 · 109
K. Floettmann KEK, Nov. 13-15, 2004
The Problem: Target Heating
MeV cm
g
2
2
1 capture efficiency
heat capacity
source area
deppos
dep
ET N
c A
E
c
A
K. Floettmann KEK, Nov. 13-15, 2004
Number of Positrons / Source Area
Example of the rotating target for TESLA:
0.8 m diameter
1250 revolutions per minute
52 m/s on the circumference
4 cm in a pulse train of 0.8 ms
Conceptual design for a rotating feed-through:“A Megawatt Electron Positron Conversion Target – A Conceptual Design” 1st EPAC Rome 1988
K. Floettmann KEK, Nov. 13-15, 2004
Heat Capacity of the Target Material
Low Z materials have a higher heat capacity (Dulong Petit Rule)
but
high Z materials give a higher positron yield.
K. Floettmann KEK, Nov. 13-15, 2004
Positron Yield vs. Target Thickness for a Photon based Source
"Structural Modeling of Tesla TDR Positron Target," Werner Stein, John C. Sheppard, July 2002 (SLAC-TN-03-043)
K. Floettmann KEK, Nov. 13-15, 2004
Radiation Damage Material Test at BNL
collaborative effort of SLAC and other labs
NOTE: Gamma based sources produce significantly less neutrons than conventional sources.
K. Floettmann KEK, Nov. 13-15, 2004
How to Increase the Capture Efficiency?
Increase the acceptance of the capture optics
requires a Predamping ring with large acceptance
Improve the positron emittance
photon based positron source with thin target
K. Floettmann KEK, Nov. 13-15, 2004
Transverse momenta
conventional source
thin target source
K. Floettmann KEK, Nov. 13-15, 2004
Comments concerning the DR design
Present situation: on energy acceptance is ok, off energy acceptance is too small
• improve off energy acceptance
• investigate possibilities to reduce the energy spread by scraping or removing correlations
Better communication between DR people and positron people is required
• assumed positron distributions seem to be too pessimistic sometimes
• realistic distributions should be used as input
Operation of a gamma based positron source without predamping ring should be possible
K. Floettmann KEK, Nov. 13-15, 2004
Undulator Based Positron Source
• Undulator length depends on the integration into the system, i.e. the distance between undulator exit and target which is required for the beam separation:
• ~ 50-150 m
K. Floettmann KEK, Nov. 13-15, 2004
Integration of the Source into the BDS of TESLA
Auxiliary and Commissioning source
“Conceptual Design of a Positron Pre-Accelerator for the TESLA Linear Collider” TESLA-99-14“Conceptual Design of a Positron Injector for the TESLA Linear Collider” TESLA-00-12
K. Floettmann KEK, Nov. 13-15, 2004
Low energy operation
0.0
0.5
1.0
1.5
2.0
2.5
50 100 150 160 200 250Electron energy (GeV)
po
sitr
on
/ele
ctro
n y
ield
safety margin
used positrons
5 Hz operation2.5 Hz operation
K. Floettmann KEK, Nov. 13-15, 2004
Low energy operation
0.0E+00
5.0E+33
1.0E+34
1.5E+34
2.0E+34
2.5E+34
3.0E+34
3.5E+34
4.0E+34
100 150 200 250 300 350 400 450 500
Ecm (GeV)
Lu
min
os
ity
(c
m-2
s-1
) scaling (fundamental)
nominal5 Hz operation
2.5 Hz luminosityoperation
High-energy optimised sourceLow-
energy optimised source
NOTE: Higher currents are possible at lower energy if the source is integrated into the BDS (limited by DR)
K. Floettmann KEK, Nov. 13-15, 2004
Auxiliary and Commissioning Source
500 MeV electron source provides low intensity (~1%) e+ source but same bunch train• commissioning source
• standby source for MD when e- system is down• e-e- and physics options source
K. Floettmann KEK, Nov. 13-15, 2004
Design of the Positron Preaccelerator
K. Floettmann KEK, Nov. 13-15, 2004
The capture optics
x
x’
x
x’
1
1
i
i
BB z
g z
g P
e B
low frequency (L-band)
Ø large iris radius
Ø long wave length
K. Floettmann KEK, Nov. 13-15, 2004
Adiabatic Matching Device - AMD
Very basic design considerations by BINP Novosibirsk (internal report):
• long pulse seems to be possible
• problem is to achieve the required field quality
K. Floettmann KEK, Nov. 13-15, 2004
NC High Gradient Cavities (solenoid focusing)
Design by INR Troitsk
K. Floettmann KEK, Nov. 13-15, 2004
Optical functions in the Separator Section
• separation of photons, positrons and
electrons
• longitudinal collimation of the positron bunches
• transverse collimation can be done in the
solenoid section
aim for no particle loss during injection into
DR
K. Floettmann KEK, Nov. 13-15, 2004
NC Low Gradient Cavities (triplet focusing)
Design by INR Troitsk
K. Floettmann KEK, Nov. 13-15, 2004
Phase Space at the exit of the Preaccelerator
K. Floettmann KEK, Nov. 13-15, 2004
Positron Transfer Line
K. Floettmann KEK, Nov. 13-15, 2004
Acceleration to 5 GeV in SC Cavities
K. Floettmann KEK, Nov. 13-15, 2004
Polarized Positron Sources
For the production of polarized positrons circularly photons are required.
Methods to produce circularly polarized photons of 10-60 MeV are:
• radiation from a helical undulator
• Compton backscattering of laser light off an electron beam
K. Floettmann KEK, Nov. 13-15, 2004
Why polarized positrons
Physics potential beyond the scope of this workshop but we can gain a factor of two in the interaction rate (eff. luminosity) by using
polarized electron and positron beams
K. Floettmann KEK, Nov. 13-15, 2004
Polarization Transfer in Pair Production
K. Floettmann KEK, Nov. 13-15, 2004
Super Conducting Design
• Ribbon-wire wound in a double helix
Current
Current
K. Floettmann KEK, Nov. 13-15, 2004
Polarization vs. Emission angle
K. Floettmann KEK, Nov. 13-15, 2004
Model of the Prototype Helical Undulator at Daresbury
K. Floettmann KEK, Nov. 13-15, 2004
Model of the Prototype Helical Undulator at Daresbury
K. Floettmann KEK, Nov. 13-15, 2004
Compton Backscattering based Positron Source
K. Floettmann KEK, Nov. 13-15, 2004
GLC Polarized Positron Source Design
K. Floettmann KEK, Nov. 13-15, 2004
Multi Collision Point Layout
K. Floettmann KEK, Nov. 13-15, 2004
GLC Collision Region
10 collision sections, with 20 collision points each:
200 collision points
K. Floettmann KEK, Nov. 13-15, 2004
E-166 Demonstration Experiment for a Polarized Positron Source
About 47 members from 17 institutions:
Brunel, CERN, Cornell, DESY, Daresbury, Durham, Jefferson, Humboldt, KEK, Princeton, South Carolina, SLAC, Tel Aviv, Tokyo M.U., Tennessee, Wasada, Yerevan
K. Floettmann KEK, Nov. 13-15, 2004
E-166 Demonstration Experiment for a Polarized Positron Source
• Final Focus Test Beam (FFTB) at SLAC with 50 GeV Electrons.
• 1 m long helical undulator produces circular polarized radiation of up to 10 MeV.
K. Floettmann KEK, Nov. 13-15, 2004
Undulator Parameter for Polarized Positron Source
Parameter TESLA E-166
Length ~150 m 1 m
Beam 200 GeV 50 GeV
Period 14 mm 2.4 mm
B-field 0.7 T 0.76 T
Energy of first Harmonic
20 MeV 9.6 MeV
Positrons/bunch 3 · 1010 2 · 107
K. Floettmann KEK, Nov. 13-15, 2004
Pulsed Undulator for E-166
• Inner diameter 0.89 mm
• Magnetic field: 0.76 T
• Pulsed current: 2.3 kA
• Rate 30 Hz
K. Floettmann KEK, Nov. 13-15, 2004
E-166 Demonstration Experiment for a Polarized Positron Source
• Conversion of photons to positrons in 0.5 X0 Ti-target• Measurement of polarization of photons and positrons by Compton transmission method• Expected polarization ~50%
K. Floettmann KEK, Nov. 13-15, 2004
E-166 Demonstration Experiment for a Polarized Positron Source
• E166 is a demonstration of production ofpolarized positrons for future linear colliders
• Uses the 50 GeV FFTB at SLAC• Approved by SLAC in June 2003• All components or prototypes work properly• Installation of total experiment in FFTB tunnel in
August 2004• First data taking run in October 2004• Second data taking in February 2005
K. Floettmann KEK, Nov. 13-15, 2004
Experiment@KEK
K. Floettmann KEK, Nov. 13-15, 2004
Experiment@KEK
K. Floettmann KEK, Nov. 13-15, 2004
Experiment@KEK
1.) Production of polarized γ‘s and polarized e+
• pol. γ: finished 2002
• pol e+: underway
2.) Polarimetry
• polarimetry of short pulse & high intensity γ rays established
• same method applicable for polarized positrons
K. Floettmann KEK, Nov. 13-15, 2004
Who wants to Do What? (to be completed)
ASIA• contributions to E166
• conceptual design for a polarized positron source for ILC (simulation study) KEK: Y. Kurihara, T. Okugi, J. Urakawa, K. Yokoya, T. Omori Tokyo Metropolitan Univ.: K. Dobashi National Institute of Radiological Sciences: I. Sakai Waseda Univ.: T. Aoki, M. Washio, T. Hirose Sumitomo Heavy Industries: A. Tsunemi
• experimental production of polarized positron at ATFKEK: Y. Kurihara, T. Okugi, J. Urakawa, T.Omori Tokyo Metropolitan Univ.: A. Ohashi National Institute of Radiological Sciences: M. Nomura, M. Fukuda Waseda Univ.: I. Yamazaki, K. Sakaue, T. Saito, R. Kuroda, M. Washio, T. Hirose
K. Floettmann KEK, Nov. 13-15, 2004
Who wants to Do What? (to be completed)
Europe• EuroTEV (s. talk by E. Elsen)
• contributions to E166
• interest to continue work on preaccelerator: beam dynamics, structures, diagnostics INR Troitsk: V. Paramonov
• synergies with FEL work at DESY: NC structure design, code development, beam dynamics
K. Floettmann KEK, Nov. 13-15, 2004
Who wants to Do What? (to be completed)
USA• E166
SLAC, collaborators: John Sheppard et al.
• conceptual positron source design SLAC, collaborators: John Sheppard et al.
• material tests SLAC and collaborators: John Sheppard et al.
• more from SLAC ??????
• beam dynamics simulations/experiment ANL: Wei Gei et al. Fermilab: Philippe Piot et al.
K. Floettmann KEK, Nov. 13-15, 2004
Workshop Announcement
'Workshop on Positron Sources for the International Linear Collider‘
This workshop will discuss relevant issues for positron production for the ILC
Daresbury Laboratory
11th to 13th April 2005
http://www.astec.ac.uk/id_mag/ID-Mag_Helical_ILC_Positron_Production_Workshop.htm