김 귀년 CHEP, KNU

1. Accelerator Activities in Korea for ILC 김 귀년 CHEP, KNU

2. Polarized e-/e+ Source for ILC

3. R&D work for PES in Korea J. Korean Phys. Soc. 44, (2004) 1303

4. 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)

5. ☻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.

6. 3rd generation polarized gun Inverted gun (SLAC) Nagoya JLAB 3 chambers: HV Gun chamber Inverted or Double insulator Prep chamber Load-lock Atomic hydrogen cleaning

7. 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

8. 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

9. 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

10. Photons 10-20 MeV Conventional vs. Gamma Based Positron Source Primary Beam Capture Optics Target thin target: 0.4 X0 Electrons 0.1-10 GeV thick target: 4-6 X0

11. Gamma Based Positron Source 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

12. 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

13. 2. Polarized Positron based on Laser Compton Gamma

14. Laser Compton Scattering Beam Line using Pohang Linac Pohang Accelerator Lab.

15. Bunch Compressor

16. σz =2.09 mm 339 µm 67 µm BYPASS BC2 BC3 ACC39 RF-GUN ACC1 ACC2 ACC3 ACC4 ACC5 ACC6 LOLA COLLIMATOR SEEDING UNDULATOR E = 120.9 MeV R56 = 169.9 mm σδ= 1.03% Θ= 17.5 deg E = 437.9 MeV R56 = 48.7 mm σδ= 0.57% Θ= 3.8 deg DUMP 1st Bunch Compressor (BC2) Y. Kim has charge of TTF2 1st BC (BC2) operation R&D Work for Bunch Compressor 1 GeV, DESY TESLA Test Facility Phase 2 (TTF2)

17. 20 GeV, DESY European XFEL Project - 4th Generation Light Source 6 GeV, SPring-8 Compact SASE Source Project – 4th Generation Light Source

18. 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

19. ACC5 ACC6 Oral Talk at 1st ILC Workshop, KEK, Japan Newly Proposed Bunch Compressor for ILC 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 z=6.00 mm 673 m 300 m Q=3.2 nC e-beam BC1 BC2 ACC2 ACC1 ACC3 ACC4 ACC39 E = 5.689 GeV  ~ 2.4% R56 = 236 mm  = 5.3 deg E = 6.0 GeV  ~ 2.174% R56 ~ 17 mm  ~ 1.4 deg 13.3 MV/m -21.5 deg 24.8 MV/m 170.0 deg 23.4 MV/m -45 deg Damping Ring Up to main linac : ELEGANT with CSR, ISR, and geometric short-range wakefields. but without space charge Final parameters E = 6.0 GeV  = 2.173% z=300 m nx= 8.7 m, ny= 0.02 m

20. Collaboration Possible Laboratory for ILC BC 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 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.

21. Summary • Based on R&D work • 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

22. Damping Ring- 김은산 박사 (포항가속기연구소)Modulator-오종석 박사(포항가속기연구소)Superconducting Cavity