김 귀년
CHEP, KNU
Accelerator Activities
in Korea for ILC
Polarized e-/e+ Source for ILC
R&D work for PES in Korea
J. Korean Phys. Soc. 44, (2004) 1303
Polarized Electron Source (Nakanishi’s summary )
- DC gun with NEA–GaAs photocathode --------- Goal is not so far -----
☺ Photocathode ------GaAs–GaAsP strained superlattice----- Pol. 90%, QE (0.5 1.0)%∼ ∼ ∼ (Nagoya/KEK, SLAC, St. Petersburg,----)
☺ High gradient gun 120 keV (SLAC, worked well for SLC) 200 keV (Nagoya---under test, SLAC---planned) 500 keV (JLAB/Cornell, Nagoya/KEK---planned)
☻ Laser system
No complete system exists, considerations are needed. (Homework; Solutions must be proposed before the next WS ?)
Bunch–structure depends on the DR scheme (by Urakawa) 1) 2.8ns100bunches (300Hz) ---------- may be no problem 2) 337ns2820bunches (5Hz) ---------- may be not easy
☺ Buncher system (beam–width: 1ns 5ps) depends on bunch structure ------ may be no problem
☺ Important gun performances ○ NEA lifetime---- o.k. by recesiation and reactivation ○ Surface charge limit effect---- may be negligible ○ Gun emittance ( ≤ 10πmm-mrad)--------- may be o.k.
3rd generation polarized gun
3 chambers:HV Gun chamber
Inverted or Double insulator
Prep chamberLoad-lock
Atomic hydrogen cleaning
Inverted gun (SLAC) Nagoya
JLAB
Next generation guns
• Polarized RF gun– Holy grail of polarized electron source– UHV requirement precludes current photocathodes– Two photon excitation?– Large band gap materials like strained InGaN
• > 500 kV DC gun– Proposal to build 500 kV gun (Nagoya)
Higher voltage and smaller emittancevs.
Higher leakage current and shorter cathode lifetime
Laser• Laser for the ILC polarized electron source requires considerable
R&D
Pulse energy: > 5 JPulse length: 2 ns# pulses/train: 2820Intensity jitter: < 5%Pulse spacing: 337 nsRep rate: 5 HzWavelength: 750 ~ 850 nm (tunable)
– Photoinjector laser at DESY-Zeuthen
Towards ILC Polarized Electron Source
• Photocathode R&D– JLAB– Nagoya/KEK– SLAC– St. Petersburg Technical University
• Gun R&D– FNAL– JLAB– Nagoya– SLAC
• Laser R&D– DESY-Zeuthen– SLAC
Conventional vs. Gamma Based Positron 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
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
Gamma Based Positron Source
1. 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
2. Polarized Positron based on Laser Compton Gamma
Pohang Accelerator Lab.
Laser Compton Scattering Beam Line using Pohang Linac
Bunch Compressor
R&D Work for Bunch Compressor
RF-GUN ACC1 ACC2 ACC3 ACC4 ACC5BC2 BC3
ACC6
BYPASS
UNDULATORDUMP
COLLIMATOR
LOLA
SEEDING
ACC39
E = 120.9 MeV R56 = 169.9 mmσδ = 1.03%Θ = 17.5 deg
σz = 2.09 mm 339 µm 67 µm
E = 437.9 MeV R56 = 48.7 mmσδ = 0.57%Θ = 3.8 deg
1 GeV, DESY TESLA Test Facility Phase 2 (TTF2)
1st Bunch Compressor (BC2)
Y. Kim has charge of TTF2 1st BC (BC2) operation
20 GeV, DESY European XFEL Project - 4th Generation Light Source
6 GeV, SPring-8 Compact SASE Source Project – 4th Generation Light Source
Pohang Accelerator Laboratory XFEL Project – 4th Generation Light Source
Bunch Compressor
for ILC
Various experiences on
start-to-end (S2E) simulations,
design of injector, bunch compressor,
and linac for XFEL projects
Newly Proposed Bunch Compressor for ILC
Final parameters
E = 6.0 GeV = 2.173%z = 300 m nx= 8.7 m, ny= 0.02 m
z = 6.00 mm 673 m 300 m
ACC1 ACC2 ACC4
Q=3.2 nC e-beam
23.4 MV/m-45 deg
24.8 MV/m170.0 deg
ACC5 ACC6ACC3BC1
E = 5.689 GeV ~ 2.4%R56 = 236 mm = 5.3 deg
E = 6.0 GeV ~ 2.174%R56 ~ 17 mm ~ 1.4 deg
BC2
13.3 MV/m-21.5 deg
Up to main linac : ELEGANT with CSR, ISR, and geometric short-range wakefields.but without space charge
Initial parameters
E = 5.0 GeV = 0.13% (small !)z = 6.0 mm nx= 8.0 m, ny= 0.02 m
1/8.9 1/2.2
Damping Ring
ACC39
Oral Talk at 1st ILC Workshop, KEK, Japan
SLAC LCLS Project Beam Energy at BC2 ~ 4.54 GeV. This is similar to beam energy at ILC BC1 (~ 5 GeV). Hence, research on incoherent synchrotron radiation (ISR) and coherent synchrotron radiation (CSR) is possible. Coming FNAL Superconducting Module Test Facility (SMTF)Injector, superconducting module, and 3rd harmonic module (3.9 GHz) are same as those for ILC. Hence, research on nonlinearity compensation in longitudinal phase space is possible.
Existing BNL Source Development Laboratory DUV FEL ProjectMicrobunching instability in bunch compressor was continuously observed at this facility.Hence, research on microbunching instability with respect to laser profile is possible.
LBNL, SLAC, and APSThese labs are working for ILC damping ring. Hence collaborated research on impact of beam instability coming from damping ring on bunch compressor is possible.
Collaboration Possible Laboratory for ILC BC
SummarySummary
• Based on R&D work
1. Polarized Electron :
- 500 keV Gun Development
- Gun Test
2. Polarized Positron :
- Laser Compton Beam Line
- Test Facility for Positron Target
3. Bunch Compressor
- Design
- Construction
Damping Ring
- 김은산 박사 ( 포항가속기연구소 )
Modulator- 오종석 박사 ( 포항가속기연구소 )
Superconducting Cavity
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