2009.3.28
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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-Pass
High-Gain Laser-Seeded Free-Electron Laser Amplifier",
PRL 98, 034802 (2007).

Outline
1. Brookhaven National LaboratoryBNL(20032008 2.
3.



FEL


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-Pass
High-Gain Laser-Seeded Free-Electron Laser Amplifier",
PRL 98, 034802 (2007).



Brookhaven
National
Laboratory(BNL)
NationalSynchrotron
Light Source
(NSLS)

Source Development Lab at BNL-NSLSRF Photoinjector

10 m
NISUS undulator

ChicaneDiagnostic
stationAcc. section
THG

Acc. section

E < 250 MeV788 nm0.15 - 10+ ps

~10 psCompressor

FEL light
Compressor

Ti:Sapphire
788 nmlaser

optical delay

RFphotoinjector10m  "NISUS"

Diagnostic station
Undulator period = 3.89 cm
K = 1.1
Undulator length = 10 m
Electron energy = 102 MeVfor Superrad

研究テーマ-7.K?*D"&H*>*+Seeded FEL,- $(F<IACFEL7

0:9

- Seeded FEL7 '+#',61;!  B@G*EJ=etc



0:9

-385/.Seeded FELSuperradiance in a single-pass seeded FEL27)
THz%EO
High Gain Harmonic Generation (HGHG) FEL 54  FEL Free Electron Laser (FEL)とは?
uUndulator*+!.$,-& ")-.( #%'+r =  u

21+K2)(22u : undulator period : normalized e-beam energy
K = 0.93 u [cm] B [T ]

FELのいろいろFELFEL oscillator

Undulator

Single-pass FEL (Seeded(SASE) FEL)
 
FEL

r

r =  uUndulator  uHarmonic Generation - cascading - n21+K2)(2 2SASE   FEL  

Peak power vs z
GENESIS1.3

Seeded FELFEL   

Peak power vs z
GENESIS1.3

SASE vs Seeded FELSASE-  Seeded FEL

SASE

Seeded FEL-  

X-FEL:   FEL
- no cavity, no seed laser for x-ray -SASE
Radiation
e-beamSeeded FEL
Cascading of superaradiance*


4.9 nm 1.4 fs 5 uJ pulse n*L. Giannessi et al., J. Appl. Phys. 98, 043110 (2005).

Superradiance in FEL- ‘50 Superradiance! [1]
- ‘80’90 R.Bonifacio"FEL #Superradiance$[2]
" "!FEL(Steady-state regime)

Poutput =  Pebeam  Ne4 3" "FEL(Superradiant regime)

Poutput  Ne2

Ne : # electrons

[1] R.H. Dicke, Phys. Rev. 93, 99 (1954).
[2] R. Bonifacio, J. Opt. Soc. Am. B., 2, 20 (1985).

Superradiance = N2 dependence?
"!?"FEL(Superradiance regime)

It's more than that!

Poutput  Ne2&- Pulse shortening ,DLNJ-- Nonlinear gain ,%'AHGP-

< 27th International Free Electron Laser Conference, 2005 >
L. G., " "?4D(SuperradianceAB$ 8E)"
V. L., "(FELA @7-0?9ASuperaradianceA
BIM+OPK=>641C83*"
M. Z, “Superradiance=12&F ;9DickeA B(?EN2
<B?5.# @/42=126=:”
*.*, "BASuperradianceA@2"94I)E + ARS-O9@I)
Poutput  Ne2.%DF/DCKC1*C<CK)))+ Superradiance regimeEDExponential regime50L)
'O#8;MB)77.$()$(RS-/5
#N?@9H2,
+SuperradianceEEN2F)F)QTPE'AFC6)5SlippageDJL:>E
A94C1,
+UO#3MB)=I=IQTPEAQTP QTP"5#N?@6M,D)N2CE4N4/3CE4O&D!GMEF

AF* , %Slippage' )

Cooperation length = Slippage distance in a gain lengthLgrLcv=Superradiancec = (&$z ) v(4 z" %+ ! Gain lengthuLg =4 r = uc  vzvz

LcFEL&*#
Exponential gain regime < SlippageSlippage

3D simulation
e-beamSeed lasersuperradiant FEL in a perfect synchronized oscillator&-%!FEL oscillator (dL=0)

'+$pass=n &-%

slippage'+$ &-%
pass=n+1&-% x '$

|A|2 peak

chirp (%)pass number

JAERI-FEL!'+$

SHG signal (a.u.)

|A|2 peak

pulse widthp/TFEL 
'+$"

p/T, chirp (%)JAERI-FEL!#(),#*-

319 fs
4.09 cycle

delay (fs)
R.Hajima, R.Nagai, Phys. Rev. Lett. 91 (2003) 024801. 

BNL-NSLS
Superradiance in a seeded FEL$1!,2= 1%-0'FEL */"7m &()

#.+$1Superradiance(Linear scale)

 
Seeded FEL(Log scale)

 
Seed laser

Seed laser ~ 4.5 ps
FEL+ 

Seed laser ~ 130 fs
FEL 

!

GENESIS 
SuperradianceEvidence

L. Giannessi)!
04.

Ultrashort  Asymmetric  Single shot 5)&%
Ultrashort13-*(&'!

E ( ) = FT 1 [ E ( t )] = A( ) exp(i ( ))phase = asymmetry)(($+)*-2,/3
22I ( ) = E ( ) = A( ) exp(i ( )) = A( )#2"'FROG (Frequency-Resolved Optical Gating)E (t   )SHG
E SHG ( t,  )E (t)GratingE˜ SHG (,  )Fouriertransform

Detector
2E˜ SHG (,  )E ( t ) E ( t   )  E SHG ( t,  )I FROG ( , ) =

 E




2



( ) exp(i t)dt =  E( t) E( t   ) exp(i t)dt

SHG t,

22IFROG (,  ) =  E˜ SHG ( t,) exp(i t  i ) dtd : 2D Fourier transform

Phase retrieval is a solved problem when certain additional
information, such as finite support, is available.
In the case, E ( t ) E ( t   )  E SHG ( t,  )Seed laser
150 fs

FEL *,'$  #&(+%)$ 
FROG !"


"*(#!)* 

T. Watanabe, et al., PRL 98, 034802 (2007).

FROG &$ '*%FROG&"#FEL13/)   81.7 fs

80 +90(-,%#*'  ('$%#! &%#*'/2.03('$%#
T. Watanabe, et al., PRL 98, 034802 (2007).

Superradiance+&0,-(.

Single-pass seeded FEL+'Superradiace1 ! ,42:1
Superradiant795,1Wideband,583691 (+795"150fs82fs*)#1
795$ (/%
J.B. Murphy"+&*%
FEL

X.J. Wang FEL 


Y. Shen,#FROG

B. Singh

T. Tsang,#FROG

L. Giannessi, ENEA, Italy FEL! $'(,$)-P. Musumeci, ENEA, Italy FEL$'(,$)-Double-checkS. Reiche, UCLA, USA  FELGENESIS1.3


JAEA   

Superradiance+,*#
2nd harmonic

Fundamental

OD6.0


BPF 400 nm

#FEL (%! )
Saturation&$

3rd harmonic$

BPF 260 nm"$

'!

!Saturation)& )