WG3a%20Sources%20Summary

1
WG3a Sources Summary

• Jim Clarke
• on behalf of
• John Sheppard, Masao Kuriki, Philippe Piot and
  all the contributors to WG3a

2
Goals for WG3a

• Review ILC electron and positron source
  requirements.
• Review proposed source designs.
• Make recommendation for the baseline reference
  design.
• Develop list of RD tasks.
• Discuss design options.
• Propose a timeline for the development of the ILC
  sources which includes criteria and milestones
  for technology selection.
• Make a list of current activities make a list of
  institutional interest in future development
  activities.

3
ILC Source Requirements
4
Electron source

• 2 sessions dedicated to electrons
• 7 presentations
• Type of gun
• DC or RF
• What DC voltage to use
• What RF scheme to use
• Photocathodes
• Lasers

5
N Yamamoto, Nagoya
6
OPCPA system for generation of trains of
femtosecond pulses with 800 nm wavelength
I. Will, H. Redlin, MBI Berlin

• OPCPA system generates trains of picosecond or
  femtosecond pulses t 150 fs .. 20 ps (FWHM)
• pulse energy Emicro 50100 mJ Etrain up
  to 80 mJ
• Available wavelength
• l 790830 nm

up to 900 us
Easily stretched
Far more energy than needed
Output pulse train of the OPCPA
K Floettmann, DESY
7
ILC polarized electron source, Baseline
Recommendation!
DC gun(s)
laser
room-temperature accelerating sect.
standard ILC SCRF modules
diagnostics section
sub-harmonic bunchers solenoids
DC gun 120 keV HV
Laser requirements pulse energy 2 mJ pulse
length 2 ns pulses/train 2820 Intensity
jitter lt 5 (rms) pulse spacing 337 ns rep.
rate 5 Hz wavelength 750-850 nm
photocathodes GaAs/GaAsP
Room temperature linac Allows external focusing
by solenoids Same as e capture linac
8
Positron Source

• 4 sessions dedicated to positrons
• 13 presentations
• 3 alternative schemes were considered in detail
• Lively discussion on pros and cons of each scheme
  !!

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Conventional Scheme
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Conventional Target
Target material WRe 56kW absorbed Target rotates
at 360m/s Operates at fatigue stress of material
W Stein, LLNL
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Positron Yield
Positron yield is defined as the ratio of the
number of captured positrons to that of incoming
electrons striking the conversion target.
Specification is 1.5 no safety margin
W Gei, ANL
12
Schematic Layout Undulator _at_ 250GeV Transfer
Paths
Undulator Based Source
Many options for undulator placement etc
D Scott, Daresbury
13
Undulator Prototypes
14mm SC, Rutherford Lab
10mm SC, Cornell
14mm PM, Daresbury
D Scott, Daresbury
14
Target and Yield

• Target
• Material is Ti
• 18kW absorbed
• Rotates at 100 m/s
• Factor of 2 safety margin in fatigue stress
• The value of positron capture for undulator-based
  source is 3-4 larger than that of electron-based
  source because of better positron beam emittance
  after target. (Y Batygin, SLAC)

15
E-166 Experiment

• E-166 is a demonstration of undulator-based
  production of (polarized) positrons for linear
  colliders
• - Photons are produced in the same energy range
  and polarization characteristics as for ILC
• -The same target thickness and material are used
  as in the linear collider
• -The polarization of the produced positrons is
  the same as in a linear collider.
• -The simulation tools are the same as those being
  used to design the polarized positron system for
  a linear collider.
• - Number of gammas per electron is lower 210
  times, however (150/1)(2.54/10)(0.4/0.17)2.

A Mikhailichenko, Cornell
16
E-166 at SLAC
Undulator table
Undulator table
Positron table
Positron table
Vertical soft bend
Vertical soft bend
Gamma table
Gamma table
A Mikhailichenko, Cornell
17
E166 Undulator Area
A Mikhailichenko, Cornell
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E-166 Results

• Number of photons agrees with expected
• Gamma polarisation agrees with theory 82-99.3
  10-20
• Number of positrons agrees with expected
• Positron Polarisation 95 30
• Simulated 84

A Mikhailichenko, Cornell
19
Compton Scheme
laser pulse stacking cavities
Compton ring
positron stacking in main DR
Electron storage ring
to main linac
T Omori, KEK
20
Proof of Principle at KEK

T Omori, KEK
21
Summary of Experiment
1) The experiment was successful. High
intensity short pulse polarized e beam was
firstly produced. Pol. 80
2) We confirmed propagation of the
polarization from laser photons -gt g-rays -gt
and pair created es e-s.
3) We established polarimetry of short pulse
high intensity g-rays, positrons, and electrons.
T Omori, KEK
22
Compton Scheme for ILC

• Electron storage ring
• Laser pulse stacking
• Positron stacking ring
• Two versions, based on either CO2 or YAG laser
• Expect 60 polarisation

23
Schematic View of Whole System (CO2)
2.5A average current
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One laser feeds 30 cavities in daisy chain
T Omori, KEK
25
e stacking in Damping Ring (simulation)
1st bnch on 1st trn
5th bnch on 5th trn
10th bnch on 10th trn
110 msec
T0
before 11th bnch on 941st trn
11th bnch on 942nd trn
15th bnch on 946th trn
10 msec
before 21st bnch on 1882nd trn
20th bnch on 951st trn
100th bnch on 8479th trn
10 msec 110 msec
20 msec
100 msec 110 msec
stacking loss 18 in total
100 bnchs on 18820th trn
100 bnchs on 9410th trn
110 msec
200 msec
T Omori, KEK
26
Open Issues for Positron Sources

• L-band warm structure 1ms operation U , LC and
  Cv.
• Target damage Cv.
• Radiation damage on target U,LC
• Thermal load of the capture section Cv.
• Damage by the operation failure U (MPS)
• Damage or failure by the instabilities U
• Degrade the electron beam quality U
• Positron Stacking in DR LC
• e beam stability in Compton Ring LC
• Vacuum pumping U
• Stability of integration of optical cavity LC
• Radiation loss, heat load in DR LC
• Fast Kicker operation with large kick angle for
  DR injection U, LC and Cv (DR problem)
• Mechanical failure on the rotation target Cv and
  U

Cv Conventional U Undulator LC Laser
Compton
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Baseline

• Baseline not yet agreed
• A number of issues for each scheme will be
  examined in detail (next week)
• Need some interaction with other groups (eg
  Damping Ring)
• Generate Performance Issues List
• Aim to make recommendation for baseline (and
  alternative) next week