Diagnostics of low–charge electron bunches at REGAE

Shima Bayesteh Hamburg UniversityShima Bayesteh Hamburg University

for REGAE teamDPG, Karlsruhe, March 2011

Electron Diffraction Experiment

REGAE (Relativistic Electron Gun for Atomic Exploration)Femtosecond Electron Diffraction (FED):Fundamental information on ultra fast atomic processesor making a molecular movie,

How to solve Space‐charge problem?

1) Number of electrons per bunchSpatial resolution

reversible  processTime resolution

2) relativistic electron beam

Spatial resolution

Time resolutionirreversible  process

bunch current

Electron probe beam

sample

Laser pump beam

Courtesy of G. Sciaini ( of Toronto)

2DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

REGAE layout

3DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

Beam requirements single shot capability

Electron beam energy 2‐5 MeV

Bunch charge 100fC ~ 10⁶ electronsBunch length 30 fs (9 μm)g ( μ )

Coherence length 30nm

Transverse emittance 6×10‐3 mrad mm

rep rate 50 Hzrep. rate 50 Hz

4DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

Scintillator screens are used for diagnostics of transvers profile.

For charged particles : high density materials to increase l b lli i

LYSO * CsI(Tl)

Density (g/cm3) 7 4 4 51

energy loss by collision.

Density (g/cm )  7.4 4.51

Effective Atomic Number

66 54

Decay Constant (ns) 40‐44 1000Decay Constant (ns)  40 44

Peak Emission (nm)  428 560

Light Yield /MeV 27000 51800 

d f f 1 82 1 79Index of Refraction  1.82 1.79

* Cerium‐doped Lutetium Yttrium Orthosilicate

5DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

LITRANILIght TRansmission in ANIsotropic media

T f i till t d th i thi k b t di d• Type of scintillators and  their thicknesses can be studied.• a general purpose Monte‐Carlo program simulating light propagation in 

isotropic or anisotropic media. http://gentitfx.fr/litrani/• The program takes into account the variation of the physical parameters as 

a function of the wavelength.

scintillation propertiesscintillation propertiesAbsorption lengthStopping powerRefractive index

6DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

FOS (Fiber Optic Plate + coated scintillator) and its application onimproving spatial resolution.

Fiber Optic Plate (FOP) is used to transfer an image without using a lens. They consist of a large number of optical fibers bundled together.

FOP

…To CCD

CsITl & Gd2O2 S (terbium‐doped gadolinium oxysulfide) offered by Hamamatsu.Proxitronic also offers the same product coated with other crystalsProxitronic also offers the same product coated with other crystals.

7DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

DetectorsFor transported light after screen

I CCD I+CCD

EMCCD

ICCD(GENII) ICCD (GENIII) EMCCD

Gating Can reach to 2ns  3µs

QE > %15 >70% >70%QE > %15 >70% >70%

Coupling to CCD

☺

Price ☺

8DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

ICCD outputs

Background

Region of interest  .(24±2) photonsper pixel

9DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

EMCCD(Electron Multiplier CCD) resultsSub-ten photons per pixel detection in single shot

Background SignalBackground  Signal 

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Increasing attenuation more than befor to have single photon detection while we cannot resolve the pattern in single shot.

Background  Signal 

EMCCD has the potential to detect few photons per pixel and is appropriate for low‐charge diagnostics but other detectors should be tested.

11DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

outlook

• The first version of diagnostics stations are ready for commisssioning at• The first version of diagnostics stations are ready for commisssioning atApril 2011.

• New image intensifiers and different scintillators efficiency should be investigated for the next version of diagnosticsinvestigated for the next version of diagnostics.

• We hope to have the first beam in REGAE by summer 2011.

12DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

Acknowledgments

K. Floettmann1, H. Delsim‐Hashemi1, R. J. D. Miller2,3, M. , , ,Huening1, S.Lederer1, J. Hircht2, D.A. Mazurenko2, D. Zhang2, G. Moriena3

1 DESY, Hamburg, Germany.2 Max Planck Research Department for Structural Dynamics at the University of  HamburgHamburg.3 Department of Chemistry and Physics, University of Toronto, Canada.

13DPG/Karlsruhe /March 2011 Shima Bayesteh/DESY

Thanks for your attention!Thanks for your attention!☺