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
/h1 laser
laser / h1h2
2
/ h1h
HHG
Gas
/ h1
HHG
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
10 4
~
/
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
nm 4 .
1 12
2 1.24nm 3 0.1033 nm
electron HHG Laser
Optimization of Radiator
3 4
ln 6
. 1
1 ,
3 ,
, 2
3 ,
1 ,
u D
G
sat D
G sat
pk b D
G D G sat
L
Ee L P
L
L P P L
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 λ u
Parameters
• Optimized parameter of Radiator
–
Period : 2.0 cm
–
Undulator parameter K : 1.13408
–Undulator field B
u: 0.60711T
–
Gap : 6.163mm
–
Radiation wavelength : 0.1033nm
• FEL parameter
–
FEL parameter ρ : 3.69159
Х10
-4 –Gain length : 3.58m
–
Cooperation length : 1.28
Х10
-8m
Result
• Saturation Power ~ 4.32GW
• Total Length ~ 65m
10 4
4 . 9
/
Radiation power at Radiator Radiation Spectrum at Radiator
Research
of the L-band BPMfor 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
