wg3a sources summary
DESCRIPTION
WG3a Sources Summary. Jim Clarke on behalf of John Sheppard, Masao Kuriki, Philippe Piot and all the contributors to WG3a. Goals for WG3a. Review ILC electron and positron source requirements. Review proposed source designs. Make recommendation for the baseline reference design. - PowerPoint PPT PresentationTRANSCRIPT
WG3a Sources Summary
Jim Clarke
on behalf of
John Sheppard, Masao Kuriki, Philippe Piot and all the contributors to WG3a
Goals for WG3a• Review ILC electron and positron source requirements. • Review proposed source designs. • Make recommendation for the baseline reference
design. • Develop list of R&D 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.
ILC Source Requirements
Parameter Symbol Value Units Particles per bunch
bn 102 10x ( 101 10x )† e- or e+
Bunches per pulse bN 2820 (5600) † number
Bunch Spacing Tb ~300 ns Pulse Repetition Rate
repf 5 Hz
Energy E0 5 GeV DR Transverse Acceptance A=2J 0.04 m-rad DR Energy Acceptance E/E 1 %,FW Overhead Factor Fc 1.5 number Electron Polarization Pe >80 % Positron Polarization (option) Pp ~60 %
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
N Yamamoto, Nagoya
OPCPA system for generation of trains
of femtosecond pulses with ~800 nm wavelength
Output pulse train Output pulse train of the OPCPAof the OPCPA
• OPCPA system generates trains of OPCPA system generates trains of picosecond or femtosecond pulses picosecond or femtosecond pulses
= 150 fs .. 20 ps (FWHM) = 150 fs .. 20 ps (FWHM)• pulse energy: pulse energy:
EEmicromicro = 50…100 = 50…100 JJEEtraintrain = up to 80 mJ = up to 80 mJ
• Available wavelength: Available wavelength: = 790…830 nm= 790…830 nm
up to 900 us
= 12 ps(FWHM)
= 523 nm
synchronizedNd:YLF Burst-Mode laser
pumping the OPA
= 150 fs (FWHM)Emicro = 50...100 J
@ f= 1 MHz
picosecond-pulseoutput channel:
pulse trains, 800 s long
= 15 ps 100 fs
G > 5 000primary
synchronization loop
master clockf = 1.3 GHz
mixer1.3 GHz
photodiode
Piezo
three-crystalOPA
outputpulse trains800 s long, = 790 ...
830 nm
gratingcompressorgrating stretcherTi:Sa oscillator
G ~ 20
I. Will, H. Redlin, MBI Berlin
K Floettmann, DESY
Easily stretched
Far more energy than needed
room-temperature accelerating sect.
diagnostics section
standard ILC SCRF modules
DC gun(s)
sub-harmonic bunchers + solenoids
laser
ILC polarized electron source, Baseline Recommendation!
Laser requirements:pulse energy: ~ 2 Jpulse length: ~ 2 ns# pulses/train: 2820Intensity jitter: < 5 % (rms)pulse spacing: 337 nsrep. rate: 5 Hzwavelength: 750-850 nm
DC gun:120 keV HV
Room temperature linac:Allows external focusing by solenoidsSame as e+ capture linac
photocathodes:GaAs/GaAsP
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 !!
“Conventional” Scheme
Conventional Target
W Stein, LLNL
Target material WRe
56kW absorbed
Target rotates at 360m/s
Operates at fatigue stress of material
Positron Yield
W Gei, ANL
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
Schematic Layout – Undulator @ 250GeV & Transfer Paths
Primary e-
source
e-
DR
5 – 100 GeV e- Bypass line
2nd e- Source
150 – 250 GeV e- Transfer Line
Target e- Dump
Photon Beam Dump
e+
DR
Auxiliary e- Source
Photon Collimators
Adiabatic Matching
Device
e+ pre-accelerator
~5GeV
Electron Linacs
100 GeV 150 GeV
HelicalUndulator
PhotonTarget
IP 250 GeV
Positron Linac
BeamDeliverySystem
D Scott, Daresbury
Undulator Based SourceMany options for undulator placement etc
Undulator Prototypes
D Scott, Daresbury
14mm SC, Rutherford Lab10mm SC, Cornell
14mm PM, Daresbury
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)
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
E-166 at SLAC
Undulator table
Positron table
Gamma table
Vertical soft bend
Undulator table
Positron table
Gamma table
Vertical soft bend
A Mikhailichenko, Cornell
E166 Undulator Area
A Mikhailichenko, Cornell
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
Electron storage ring
laser pulse stacking cavities
po
sitron
stacking
in m
ain D
RCompton Scheme
to main linac
Compton ring
T Omori, KEK
Proof of Principle at KEK
T Omori, KEK
Summary of Experiment1) The experiment was successful. High intensity short pulse polarized e+ beam was firstly produced. Pol. ~ 80%
3) We established polarimetry of short pulse & high intensity -rays, positrons, and electrons.
2) We confirmed propagation of the polarization from laser photons -> -rays -> and pair created e+s & e-s.
T Omori, KEK
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
Schematic View of Whole System (CO2)
~2.5A average current
One laser feeds 30 cavities in daisy chain
T Omori, KEK
e+ stacking in Damping Ring (simulation)1st bnch on 1st trn 5th bnch on 5th trn
100 bnchs on 18820th trn
10th bnch on 10th trn
before 11th bnch on 941st trn
11th bnch on 942nd trn 15th bnch on 946th trn
20th bnch on 951st trn before 21st bnch on1882nd trn
100th bnch on 8479th trn
100 bnchs on 9410th trn
~110 sec
~10 msec
~10 msec + 110 sec ~20 msec ~100 msec + 110 sec
~110 msec ~200 msec
T=0
-0.4 0.4Longitudinal Pos. (m)
-0.0
3
0.
03E
ner
gy/E
ner
gyi-th bunch on
j-th DR turn
Time
e+ in a bucket
stacking loss = 18% in total
T Omori, KEK
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
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