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) 2.8ns  100bunches (300Hz) may be no problem 2) 337ns  2820bunches (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.

3 rd generation polarized gun 3 chambers: HV Gun chamber Inverted or Double insulator Prep chamber Load-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 emittance vs. Higher leakage current and shorter cathode lifetime

Laser Laser for the ILC polarized electron source requires considerable R&D Pulse energy: > 5  J Pulse length: 2 ns # pulses/train: 2820 Intensity jitter: < 5% Pulse spacing: 337 ns Rep rate: 5 Hz Wavelength: 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 MeV Electrons GeV Primary BeamCapture Optics thin target: 0.4 X 0 thick target: 4-6 X 0

For the production of polarized positrons circularly photons are required. Methods to produce circularly polarized photons of 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: ~ 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-GUNACC1ACC2ACC3ACC4ACC5 BC2BC3 ACC6 BYPASS UNDULATOR DUMP COLLIMATOR LOLA SEEDING ACC39 E = MeV R 56 = mm σ δ = 1.03% Θ = 17.5 deg σ z = 2.09 mm 339 µm 67 µm E = MeV R 56 = 48.7 mm σ δ = 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 1 st BC (BC2) operation

20 GeV, DESY European XFEL Project - 4 th Generation Light Source 6 GeV, SPring-8 Compact SASE Source Project – 4 th Generation Light Source

Pohang Accelerator Laboratory XFEL Project – 4 th 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/m deg ACC5ACC6ACC3 BC1 E = GeV   ~ 2.4% R 56 = 236 mm  = 5.3 deg E = 6.0 GeV   ~ 2.174% R 56 ~ 17 mm  ~ 1.4 deg BC MV/m 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 1 st 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 3 rd 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 Project Microbunching 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 APS These 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

Summary Based on R&D work 1. Polarized Electron : 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