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