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