The design study for a hard X-ray

generation by using High Harmonic

Generation Free Electron Laser

김 혜진, 김 은산

경북대학교

Contents

• Introduction to FEL

• The type of FEL

• Principle of HHG-FEL

• Advantage of HHG-FEL

• Optimization of HHG-FEL

• Summary

• Reference

Hard X-ray Free Electron Laser

Hard X-ray

Very Short (~Å) &

Very Fast (~THz)

SASE Amplifier

Laser Seeded Amplifier

(external seeding)

Chicane Radiator in/n

Harmonic Generation (external seeding)

Oscillator (self-seeding)

Type of FEL

Modulator

J.B. Murphy and J. Wu, The Physics of FELs, US Particle Accelerator School, Winter, 2009

Harmonic Generation

Modulator

Bunching Chicane

Radiator

Fresh Bunch Chicane

electron

Laser

electron

Laser HHG Laser

Laser Seeded HGHG Cascade

HHG Seeded Cascade FEL

1/ hlaser 21/ hhlaser

21/ hhHHG

Gas

1/ hHHG

NLS SCSS SwissFEL Wisconsin SOLEIL

Energy [GeV] 2.21 0.15 2.1 2.2 1

Wavelength [nm]

1~20 4.7 4 1 1

Repetition Rate (Hz)

1 k 10 100 1 M 10 k

Laser type Ti:Sa Ti:Sa Ti:Sa Ti:Sa Ti:Sa

country EURO Japan Swiss USA France

High Harmonic Generation FEL

HHG FEL at SCSS test accelerator

The HHG-FEL covers the soft X-ray(~nm) region.

High Harmonic Generation Energy modulation

is converted to

density modulation

in chicane.

Input seed laser

overlaps electron

beam in energy

modulator

Electron beam radiates

coherently in long

radiator undulator.

William S. Graves

R. Bartolini

Advantage of HHG FEL

SASE FEL HHG FEL

1 . High peak power with sharp peak( )

2 . Stability (shot to shot power, spectrum, …)

3 . Longitudinal coherent

4 . Control of pulse length

410~/

Designed Hard X-ray HHG scheme

Modulator

Quadrupole Magnet Chicane

Radiator

L=8cm B=1.5T

5.58mrad

λu=7cm K= 10.52

L=8cm B=1.5T

5.58mrad

λu=4.4cm K= 3.99 λu=2cm

K= 1.13

…

4.9m 2.64m 1.4m

5.6m 9.4m 50m

nm4.121 nm24.12 nm1033.03

electron

HHG Laser

Optimization of Radiator

34

ln

6.1

1,

3,

,

2

3,

1,

uDG

satDGsat

pkb

DG

DG

sat

L

Ee

PLL

PL

LP

Psat~ 6 GW Lsat~ 65 m

E0=6.44GeV εn=0.4 mm-mrad Bunch length = 9.76fs Bunch charge =0.2nC Peak current = 6kA

Optimization of first chicane

L=6.6 cm

Optimization of second chicane

L=6.6 cm

Chicane length [cm]

Optimization of chicane

B0= 1.5T

Optimization of λu

Parameters

• Optimized parameter of Radiator

– Period : 2.0 cm

– Undulator parameter K : 1.13408

– Undulator field Bu : 0.60711T

– Gap : 6.163mm

– Radiation wavelength : 0.1033nm

• FEL parameter

– FEL parameter ρ : 3.69159Х10-4

– Gain length : 3.58m

– Cooperation length : 1.28Х10-8m

Result

• Saturation Power ~ 4.32GW

• Total Length ~ 65m

4104.9/

Radiation power at Radiator Radiation Spectrum at Radiator

Research of the L-band BPM for the Superconducting Linear Accelerator

L-band BPM

Chamber

(ATF linac)

Resolution limit = Noise level [counts]

Calibration factor [counts/μm]

= 340 nm

The L-band beam position monitors are used

to stabilize the beam orbit in the linac in FEL

Also see : Poster session : A. Y. Heo Oral session : S. Y. Ryu

Summary

• We performed the design study of the Hard X-ray HHG-

FEL with 6.4 GeV of energy, 0.4 mm-mrad emittance and 6

kA of current of electron beam.

• The saturation power is 4.3 GW with the 65 m of total

length.

• The parameters of the beam which are used to the study

were gotten by the S2E simulation of the 6.4 GeV linac.

• We will use to the beam distribution get from S2E

simulation.

• We are collaborating with LBNL for the research of soft X-

ray HHG FEL.

Reference

• J.B. Murphy and J. Wu, The Physics of FELs, US

Particle Accelerator School, Winter, 2009

• R. Bartolini, Progress in Soft X-rays FELs

• G. Lambert et al, Proceedings of EPAC08, Genoa,

Italy

• Neil Thompson, Free Electron Laser 2009, Liverpool

BACK-UP

HHG Laser Scheme Ti:S laser @ 800nm

λ=160 nm (5th harmonic)

λ=32 nm (5th harmonic)

G. Lambert et al, Proceedings of EPAC08, Genoa, Italy

HHG Laser Principle

John W. G. Tisch, NLS Source Meeting, Daresbury, 2 March 2000