The BESSY The BESSY Soft X-Ray Soft X-Ray SASESASE FEL FEL

The BESSY Soft X-Ray The BESSY Soft X-Ray SASE FEL (Free Electron SASE FEL (Free Electron Laser)Laser)

Roland Müller

EPICS Meeting Spring `02, BESSY, Berlin

infrared

visible - uv

FEL facilities

electron bunch trainundulator + optical resonator

bunching

coherentemission

Classical FEL Scheme

undulator (amplifier)

bunching

coherentemission

electron bunch train undulator (spontaneous emission)

SASE FEL Scheme(Self Amplified Spontaneous Emission)

SASE-FEL SetupGoal:Photon Energy E 0.02 – 1 keVWavelength 60 – 1.2 nmPeak Brilliance B ~1029 *)

Pulse duration 20 – 100 fs*) photons/s/mm2/mrad2/0.1% bw

Required*):Beam Current I 1.5 – 5.0 kABeam Energy E 0.7 – 2.25 GeVEnergy spread

E 1 – 2 MeVEmmittance

n 1.5 10-6 m rad

Undulator Length Lund ~ 50 m*) Parameters are coupled

1980 First proposal1996 First experimental observation

UCLA: = 16 mDec. 1999 APS: lasing at = 523 nmFeb. 2000 DESY: lasing at = 80 nmSep. 2000 APS: saturation at = 523 nmFeb. 2001 VISA/BNL: saturation at = 800 nmApr. 2001 APS: saturation at = 385 and =

265 nmSep. 2001 DESY: saturation at = 100 nmOct. 2001 First user experiments @ DESY-TTF

History of SASE

Development steps towards VUV and X-ray FELs

SASE FEL User FacilitiesUnder construction and/or

operational• TTF / DESY* > 6 nm (80 nm)• LEUTL / APS* > 120 nm (265 nm)

Proposed• BESSY 1.2 nm (1 keV)• SLAC 1.5 Å (8 keV)• SPring8 15 nm 3.6 nm 0.1 nm• TESLA 0.85 Å (14 keV)• ELETTRA, ENEA, Daresbury …...

* Hybrid between FEL development & user facility

TESLA X-ray FEL

linear collider

> 0.85 Å (14 keV): X-rays

TTF FEL: TESLA Test Facility

> 6 nm (200 eV): VUV & XUV

User Feedback

Proposal: FEL user-facility that becomes operational after 2007

Important issues:

• Photon energy:………………………… 20 eV - 1.0 keV (60 1.2 nm)

• Micro-pulse duration:………………………… 20 fs

• Narrow spectral width:……………………… 10-4

• Synchronization with fs lasers

• As many as possible photons per pulse

• High average brilliance

1.5 - 2.25 GeV linac

TESLA module

injector3rd harmonic cavity

bunch compressor

The BESSY FEL

extraction

multiple undulators

BESSY II undulator UE46

drift for monochromator

s and beam-blowup

The BESSY FEL

undulator: 20 - 50 m

APPLEplanar

~2.5 m

~2.0 m

gap(wavelength change)

( po la r i za t io n c h an g e)

s h i ftdrift:- q- end pole correction- phase matching- orbit correction- orbit diagnose

uadrupole

Separate focussing undulator

(control of the -function)

The BESSY FEL

Linac Tunnel

Cryogenic Hall

Injector Hall

Experimental Hall

BESSY II

> 1.2 nm (1 keV): VUV & soft X-rays

Performance

1 0 0 1 0 1

1 02 1

1 02 4

1 02 7

1 03 0

1 03 3

0 . 0 1 0 . 1 1

B E S S Y F E L

T T F F E L

T E S L A F E L

w a v e l e n g t h ( n m )

pe

ak

br

illi

an

ce

(p

ho

ton

s/

se

c/m

m2

/mr

ad

2

/0.1

%b

w)

U E 5 6U 1 2 5

U 4 9

U 4 1

B E S S Y I I

1 0 m A s i n g l e b u n c h

= 0 . 1 %

p h o t o n e n e r g y ( k e V )

1 0 0 0 1 0 0 1 0 1 0 . 1

1 00

1 03

1 06

1 09

1 01 2

pe

ak

po

we

r(

W)

L C L S

T E S L A F E L

T T F

B E S S Y F E L

w a v e l e n g t h ( n m )

0 . 0 10 . 0 0 1 0 . 1 1 1 0

H H G

U 4 9

A P S

U 1 2 5e

xc

ime

rs

Ru

by

Nd

:Gla

ss

p la s m a l a s e r s

T W l a s e r

d y e la s e r s

p h o t o n e n e r g y ( k e V )

1 0 m A s i n g l e b u n c h

= 0 . 1 %

B E S S Y

The BESSY Soft X-Ray SASE FEL

X-RAYSTESLA X-FEL

VUV and SOFT X-RAYSBESSY FEL

COMPLEMENTARITY of theVUV and X-RAY FEL

20 eV to 1 keV PHOTON ENERGY 500 eV to 15 keV1 mJ PULSE ENERGY 1 mJ

200 fs to 20 fs PULSE LENGTH 100 fs1 kHz (1-25 pulses) REPETITION RATE 5 Hz (7200 pulses)

Critical Issues For any SASE-FEL Project:

– Stability of the electron beam– Diagnostics– Spiking nature of the SASE-FEL radiation– Synchronization with other laser sources

Specific for the BESSY SASE-FEL:– Cryogenic requirements (15 MV/m, cw)– Optimization of the photo-injector– Beamlines

Summary (1) Building of a “basic” FEL user facility

(based on super-conducting linac technology from DESY)

Goal: construction of a SASE-FEL for the

UV to soft X-ray spectral range construction of three parallel SASE-

FEL beamlines Synchronization with conventional fs

laser-sources: jitter 200 fs (rms)

Major cost factors: Civil engineering Cryogenic plant Accelerators Undulators Beamlines

Critical tasks: Injector system Bunch compressors Diagnostics Feedback (Microphonics, Timing …) Beamlines

Ppeak 5 GW*

t 35 fs

/ = 10-3

FEL Emax

(GeV)

min

(nm)E (eV)

123

0.851.702.25

15.02.51.2

85500

1000*Bpeak 1028 ph/sec/mm2/mrad2/0.1%bw)

Summary (2)Implementing FEL enhancements*

Enhancing the spectral resolution:

/ = 10-3 <10-4 (Seeding)

Shortening the micro-pulse duration:

t = 160 fs 20 fs ? fs

Flexible FEL output (fast scanning, chirping, etc.)

Increasing the average brilliance

*Not all enhancements can be obtained simultaneously