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Superradiant
JASRI/SPring-8
2009.3.2864
T. Watanabe, X.J. Wang, J.B. Murphy, J. Rose, Y. Shen, T. Tsang,L. Giannessi, P. Musumeci, and S. Reiche,"Experimental Characterization of Superradiance in a Single-PassHigh-Gain Laser-Seeded Free-Electron Laser Amplifier",PRL 98, 034802 (2007).
1. Brookhaven National Laboratory BNL(2003 2008
2. FEL
3.
Outline
T. Watanabe, X.J. Wang, J.B. Murphy, J. Rose, Y. Shen, T. Tsang,L. Giannessi, P. Musumeci, and S. Reiche,"Experimental Characterization of Superradiance in a Single-PassHigh-Gain Laser-Seeded Free-Electron Laser Amplifier",PRL 98, 034802 (2007).
BrookhavenNational
Laboratory(BNL)
NationalSynchrotronLight Source
(NSLS)
Source Development Lab at BNL-NSLS
RF Photoinjector
Acc. section
Chicane
Acc. section
10 mNISUS undulator
Diagnosticstation
Ti:Sapphirelaser 788 nm
THG
Compressor
Compressor
788 nm0.15 - 10+ ps
E < 250 MeV
FEL light
optical delay
~10 ps
RF photoinjector
10m "NISUS"
Diagnostic station
Undulator period = 3.89 cmK = 1.1Undulator length = 10 mElectron energy = 102 MeV for Superrad
研究テーマ
Superradiance in a single-pass seeded FEL
Seeded FEL
- FEL
- Seeded FEL
etc
THz EOHigh Gain Harmonic Generation (HGHG) FEL
Seeded FEL
FEL
Free Electron Laser (FEL)とは?
Undulator
r = u
1+ K 2 2( )2 2
u : undulator period
K = 0.93 u cm[ ]B T[ ]
: normalized e-beam energy
u
FEL oscillator
FELのいろいろ FEL
FELSingle-pass FEL (SASE)
uUndulator
r
Single-pass FEL (Seeded FEL)
Undulator
r = u
1+ K 2 2( )2 2
Harmonic Generation - cascading -
n
SASE
Peak power vs z
FEL
GENESIS1.3
Seeded FEL
GENESIS1.3
Peak power vs z
FEL
Seeded FEL
SASE
SASE vs Seeded FEL
SASE
Seeded FEL
-
-
X-FEL: FEL - no cavity, no seed laser for x-ray -
Radiation
e-beam
SASE
Seeded FEL
*L. Giannessi et al., J. Appl. Phys. 98, 043110 (2005).
Cascading of superaradiance*4.9 nm 1.4 fs 5 uJ pulse
n
Superradiance in FEL
Poutput = Pe beam Ne
4 3" " FEL(Steady-state regime)
Poutput Ne
2" "FEL(Superradiant regime)
[1] R.H. Dicke, Phys. Rev. 93, 99 (1954).[2] R. Bonifacio, J. Opt. Soc. Am. B., 2, 20 (1985).
N
e : # electrons
- ‘50 Superradiance [1]- ‘80 ’90 R.Bonifacio FEL Superradiance
[2]
Superradiance = N2 dependence? It's more than that!
Poutput Ne
2" "FEL(Superradiance regime)
&- Pulse shortening - Nonlinear gain
< 27th International Free Electron Laser Conference, 2005 >
L. G. , " Superradiance "V. L. , "(FEL Superaradiance "M. Z , “Superradiance Dicke N2
”. , " Superradiance "
Poutput Ne
2
Superradiance regime Exponential regime
Superradiance N2
Slippage
N2 N4/3
Slippage
L
c
Cooperation length = Slippage distance in a gain length
Lg = u
4
Lc c vz( )Lg
vz
= r
4
r=
u
c vz
vz
FEL < Slippage
Gain length
Exponential gain regime Slippage
Superradiance =
e-beam Seed laser
3D simulation
FEL oscillator (dL=0)
pass=n
pass=n+1
superradiant FEL in a perfect synchronized oscillator
slippage
x
delay (fs)
SHG
sig
nal (
a.u.
)
pass number
|A|2
peak
p/T,
chi
rp (
%)
chirp (%)
p/T|A|2 peakpulse width
FELJAERI-FEL JAERI-FEL
319 fs4.09 cycle
R.Hajima, R.Nagai, Phys. Rev. Lett. 91 (2003) 024801.
BNL-NSLSSuperradiance in a seeded FEL
= FEL
7m
Seeded FEL(Log scale)
Superradiance(Linear scale)
Seed laser ~ 4.5 psFEL
Seed laser ~ 130 fsFEL
Seed laser
+
GENESIS
Superradiance Evidence
Ultrashort Asymmetric Single shot
I ( ) = E( )2
= A( )exp i ( )( )2
= A( )2
E( ) = FT 1 E t( )[ ] = A( )exp i ( )( )phase = asymmetry
Ultrashort
L. Giannessi
FROG (Frequency-Resolved Optical Gating)
IFROG
,( ) = ESHG
t,( ) exp( i t)dt
2
= E t( )E t( ) exp( i t)dt
2
SHG
E t( )
E t( )
ESHG t,( )Fouriertransform
Grating ˜ E SHG ,( ) Detector
˜ E SHG ,( )2
E t( )E t( ) ESHG t,( )
Phase retrieval is a solved problem when certain additionalinformation, such as finite support, is available.
IFROG ,( ) = ˜ E SHG t,( )exp i t i( )dtd2
: 2D Fourier transform
E t( )E t( ) ESHG t,( )In the case,
Seed laser 150 fs
FEL
FROG
T. Watanabe, et al., PRL 98, 034802 (2007).
FROG
FROG FEL
80 90
T. Watanabe, et al., PRL 98, 034802 (2007).
81.7 fs
Superradiant
Wideband
150fs 82fs
Single-pass seeded FEL Superradiace
Superradiance
J.B. Murphy
FEL
X.J. Wang
FEL Y. Shen
FROG
B. Singh
T. Tsang
FROG
L. Giannessi, ENEA, Italy FELP. Musumeci, ENEA, Italy FEL Double-checkS. Reiche, UCLA, USA FEL GENESIS1.3
JAEA
Fundamental 2nd harmonic 3rd harmonic
OD6.0 BPF 400 nm BPF 260 nm
Superradiance
FEL
Saturation Saturation