The ORS at FLASH and sFLASH

The ORS at FLASH and sFLASH

Peter van der Meulen

Stockholm UniversityDiv. Molecular Physics

FLS2010, March 1-5, 2010, 48th ICFA Advanced Beam Dynamics Workshop on Future Light Sources

a new diagnostic tool for characterizing electron bunches

ORS: Optical Replica Synthesizer

FLASH, XFEL, JFEL, LCLS: SASE

electron bunch properties: longitudinal density profileslice emittanceslice energy spread

SASE is very sensitive to the properties of the electron bunch

need to control and measure these properties!

electron bunch: moving at v ≈ cca. 20 m longca. 100 m wide

hard to measure directly measure an optical copy instead





Erbium fiber oscillator:• 1550 nm• ca. 54 MHz• amplified• frequency doubled, 1 mm PPLN• 1 – 5 mW

Clark-MXR CPA2001• Ti:Sapph CPA system • 5 Hz (1 kHz)• ca. 700 J/pulse• 0.2 – 3.0 ps


ORS: temporal overlap

Er:fiberoscillator

stretcher compressorTi:Sapphamplifier

to tunnel

ca.54 MHzpulse train

FLASH 5 Hz trigger

ca.19 ns

Fourier Transform 24th harmonic

ca. 1.3 GHz

diff. freq.mixing

FLASH RF1.3 GHz

vectormodulator

Matlab progam

piezo +delay

…+ cos[(.t + ] = 0

delay


ORS: Magnet structures

Undulators:• electromagnets• 1450 mm• 40 mm gap, 0.5 T max.• 14 poles (1/4,-3/4,1,-1…)• 4 power supplies• modulator vertical• radiator horizontal

Chicanes:• 4 dipole magnets• 1300 mm


ORS: spatial overlap

calibration and OTR screens on7Match and 3SUND1

Joern Boedewadt


https://ttfinfo.desy.de/TTFelog-secure/data/2009/04/25.01_M/2009-01-25T09:43:01-00.JPG


0 1 2 3 4 5 6

0

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Time (ps)

Coh

eren

t O

TR

int

ensi

ty (

arb.

uni

ts)

CoherentOTR

@ 385 nm

PRSTAB 11, 070702, 2008FLS2010, March 1-5, 2010, 48th ICFA Advanced Beam Dynamics Workshop on Future Light Sources

GRENOUILLE*

based on SH FROG technique (autocorrelator + spectrometer)

single shot measurement

2D phase retrieval algorithm => fully characterized pulse

Electric field profile electron bunch profile (I4)

femtosecond optical pulse characterization

* Swamp Optics


ORS: FROG trace

seed laser pulse: ca. 400 fs FWHMFROG trace: ca. 150 fs FWHM FLASH’s electron bunch spike?

Compatible with SASE!!!FLS2010, March 1-5, 2010, 48th ICFA Advanced Beam Dynamics Workshop on Future Light Sources

ORS: FROG trace

• ca. 1-5 J/pulse

• ca. 150 fs FWHM

• no direct comparison with TDC (LOLA) FLS2010, March 1-5, 2010, 48th ICFA Advanced Beam Dynamics Workshop on Future Light Sources

-800 -600 -400 -200 0 200 400 600 8000

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E-f

ield

(ar

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nits

)

Time (fs)-800 -600 -400 -200 0 200 400 600 800

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ORS at FLASH

Some remaining issues:

• cross check with TDC (LOLA) and/or EO measurement

• laser power: 1 mJ/ pulse 30 mJ/pulse

• better digital data collection: 8 bit 12/16 bit

• what happens under further bunch compression? CSR?

• what is the future of the ORS?

The ORS seems to work, but…


ORS: FROG trace

A FROG trace obtained upon further compressing the electron bunch:


ORS at sFLASH

temporary shutdown September 2009

rebuild ORS in new position


ORS at FLASH

Other applications of the ORS:

• phase of optical replica pulse energy chirp of electron bunch

• slice energy spread

• slice emittance

• 3D spatial electron bunch characterization via coherent OTR

• ‘echo’ test experiments (G. Stupakov, SLAC-PUB-13445, Oct. 2008)

• ORFIR

• general study laser – electron interactions


conclusions

• first ORS results obtained in 2009!!!

• the ORS seems a very useful addition to (s)FLASH, as a diagnostic device. Some issues deserve further study.

• more (parasitic) beam time is required to make the ORS a standard and routine diagnostic technique.

• ‘alternative’ applications of the ORS appear very promising.


DESY, 27 January 2009

Collaborators

Stockholm University: Peter Salen Mathias Hamberg Mats Larsson

Uppsala University: Volker Ziemann Gergana Angelova-Hamberg

DESY: Holger Schlarb Florian Löhl

Hamburg University: Joern Boedewadt Axel Winter Shaukat Khan

BESSY: Atoosa Meseck

DESY: E. Saldin, E. Schneidmiller & M. Yurkov


THANK YOU!



Holger SchlarbFlorian Löhl


ORS @ sFLASH

What to do:

• move undulators, dipoles and optical stations (+ cables)

• re-build OS1 chicane in vertical plane; re-design OS2 chicane

• change to HHG laser; 10% beamsplitter, ca. 4 mJ/pulse + compression

• improve laser beam diagnostics

• insert new OTR screens: diffuse scattering screen doped YAG screen for e-beam and laser? better optical quality: surface and flatness


DESY, 27 January 2009

BOA pulse compressorBother-free Optimized Arrangement

Swamp Optics

fused silicatransmission

grating,ca. 1000 l/mm

• no angular dispersion• no pulse front tilt• no spatial chirp


• imaging using coherent OTR/ODR: longitudinal bunch profile high k – small wavelength compared to THz measurements high intensity

I(r) N d2r’ dz (r’,z) Eone-electr(r-r’) 2

+

N2 d2r’ dz exp(-ikz) (r’,z) Eone-electr(r-r’) 2

Icoh(r) N2 d2 (,k) ( exp(ir))/( 2 + 2) 2 = k/

if (,k) = f() . g(k) X

but….

ORS contributions to sFLASH


The ORS as a routine diagnostic?PR

STA

B 1

1, 0

7070

2, 2

008

what about the possibility to do an image reconstructionusing algorithms similar to those applied in single-particle

X-ray diffraction?

multiple k’s and modulation using chirped seed pulses


The ORS at FLASH and sFLASH

Documents

future light sourcesors

future light sourcesgrenouille

frog tracea frog trace

frog traceseed laser

bunch compression

fs fwhmfrog trace

optical copy insteadfls2010

tdc lola fls2010