HELMHOLTZ GEMEINSCHAFT VUV FEL EO systems at the DESY VUV-FEL Stefan Düsterer for the VUV - FEL Team F. Van den Berghe, J. Feldhaus, J. Hauschildt, R. Ischebeck, K. Ludwig, H. Schlarb, B. Schmidt, S. Schmüser, S. Simrock, B. Steffen, A. Winter and all the others Adrian Cavalieri, David Fritz, Soo-Heyong Lee, David Reis (Michigan University Ann Arbor, Michigan)

HELMHOLTZ GEMEINSCHAFT VUV FEL The 2 EOS systems Experiments EOS „Electro Optical Sampling“ chirped laser pulseEOS „Electro Optical Sampling“ chirped laser pulse TiSa fs-oscillator TEO „Timing Electro Optical sampling“ 45° - geometryTEO „Timing Electro Optical sampling“ 45° - geometry pump-probe fs-laser for FEL-experiments

HELMHOLTZ GEMEINSCHAFT VUV FEL T iming EO Timing monitor for the FEL-optical pump-probe Experiments optimized for electron bunch ARRIVAL TIME measurements part of the pump-probe laser system final goal:final goal: provide timing data to users delay delay + jitter

HELMHOLTZ GEMEINSCHAFT VUV FEL Layout: pump-probe experiments optical laser FEL pulse Optical pulse to TEO

HELMHOLTZ GEMEINSCHAFT VUV FEL TEO Pockels cell 50 % beam splitter

HELMHOLTZ GEMEINSCHAFT VUV FEL The laser hutch overview picture - CDR layout TEO

HELMHOLTZ GEMEINSCHAFT VUV FEL The TEO layout - in the laser hutch laser hutch - CDR layout

HELMHOLTZ GEMEINSCHAFT VUV FEL The TEO layout - in the tunnel tunnel - CDR layout High degree of automation 19 motors 6 cameras 3 photo diodes / PMTs 3 photo diodes / PMTs every important parameter can be controlled and changed from the control room - fully integrated in the control system - High degree of automation 19 motors 6 cameras 3 photo diodes / PMTs 3 photo diodes / PMTs every important parameter can be controlled and changed from the control room - fully integrated in the control system -

HELMHOLTZ GEMEINSCHAFT VUV FEL TEO - first steps... Laser hutch Accelerator tunnel

HELMHOLTZ GEMEINSCHAFT VUV FEL TEO - simulations critical parts like the compressor the phase-shaper the imaging of the crystal the interaction between laser and el. field in the crystal were simulated in order to optimize TEOs performance

HELMHOLTZ GEMEINSCHAFT VUV FEL introducing LAB II simulation software Th. Feurer and group Simulation of fs-pulse propagation by Th. Feurer and group (Jena / MIT /Bern) time - frequency domain (no spatial calculations) linear and nonlinear effects / three wave mixing various materials compressors, strechers and phase shaper auto- / cross-correlation, FROGs and much much more Based on LabView Free download at

HELMHOLTZ GEMEINSCHAFT VUV FEL Lab II - simulation of TEO ~ 70 fs FWHM

HELMHOLTZ GEMEINSCHAFT VUV FEL The compressor compensate for dispersion induced fs-pulse broadening by the 170 m glass fiber compensates the huge Group Velocity Dispersion (GVD) (second order deriv. of phase) BUT induces third (and higher) order phase distortions (TOD) optimization dilemmabandwidth transmission (constant grating size) induced TOD highly dispersive gratings (1800 lines / mm)  low dispersive gratings (1200 lines / mm)  TOD induced by fiber: fs 3 / TOD by compressor: fs 3

HELMHOLTZ GEMEINSCHAFT VUV FEL the phase shaper - actual design Geometry is entirely on-axis. ( design by G. Stobrawa, U. Jena) folding mirror algorithms for LCD-matrix - start with genetic algorithm (Soo / Michigan) -next step: parameterization with to Taylor coefficients. of the phase (about 100 times faster - Jena) algorithms for LCD-matrix - start with genetic algorithm (Soo / Michigan) -next step: parameterization with to Taylor coefficients. of the phase (about 100 times faster - Jena)

HELMHOLTZ GEMEINSCHAFT VUV FEL TEO - imaging ray tracing well below diffraction limit wave front propagation 1:2 imaging using achromatic lenses Tilted object → tilted camera diffraction limited resolution < 10 µm for 2 mm field of view

HELMHOLTZ GEMEINSCHAFT VUV FEL 0.5mm 10mm The wedged crystal (ZnTe) SignalTemporal resolution Thick crystal  Thin crystal  online Change sensitivity vs. temporal resolution online

HELMHOLTZ GEMEINSCHAFT VUV FEL Wedged crystal

HELMHOLTZ GEMEINSCHAFT VUV FEL Simulation of EO-Response Function First reflection of THz field e-beam Linear diode array 1000 pixel incidence angle of laser freq. dependent refraction freq. dependent EO-coeff. group velocity mismatch multiple reflection

HELMHOLTZ GEMEINSCHAFT VUV FEL Simulation of EO-Response Function T=-50 fs 20% shorter bunch 5% more charge origin 100 pixel 17%

HELMHOLTZ GEMEINSCHAFT VUV FEL Challenge: detection at 1 MHz ELIS photo-diode array (silicon video inc.):  Pixels: 1024 / 8 µm  Readout: 30 MHz  1000 pixel -> 30 µs  128 pixel -> 4 µs  Gating 15 ns  Low cost ns 15 ns

HELMHOLTZ GEMEINSCHAFT VUV FEL Differences between TEO and SPPS  Pockels cell behind fs-oscillator ~ 100% of laser power available  all reflective shaper  70 fs pulses (FWHM) at crystal are possible 60 nm transmission through the whole system  jitter: no regenerative laser amplifier - but larger distance to experiment  gating by detection (line camera) wedge crystal  wedge crystal – change temporal resolution continuously and online  More than 20 motors / 6 cameras – TEO can be entirely remote controlled

HELMHOLTZ GEMEINSCHAFT VUV FEL EOS Timing monitor for the FEL-optical pump-probe Experiments Flexible EOS system to test various concepts scanning EO chirped pulse EO Electron bunch diagnostic longitudinal bunch structure Sub 15 fs Femtolaser Located in container close to the accelerator 15 m beamline (future upgrade: amplified pulse / single shot correlation) Container electrically isolated / RF shielding Temperature stabilized RF cable Beamline for CTR -> EOS in container ( test of crystals …)

HELMHOLTZ GEMEINSCHAFT VUV FEL EOS - Setup To spectrometer OTR ZnTe crystal 300 µm electrons TiSa fs pulse 65 nm FWHM / 15 fs

HELMHOLTZ GEMEINSCHAFT VUV FEL Conclusion 2 EOS systems2 EOS systems –to test different EO schemes –Cross-check (Goal) Measure at 1 MHz – each pulse –Machine diagnostics –Essential for user pump-probe experiments TEO –50 fs arrival time monitor –Highly automated (standard diagnostics) EOS –100 fs longitudinal electron bunch resolution

HELMHOLTZ GEMEINSCHAFT VUV FEL Dies ist eine schöne vorlage...

HELMHOLTZ GEMEINSCHAFT VUV FEL TEO in numbers TEO in numbers shaper: 640 element LCD matrix, 1800 l/mm grating, 500 mm focal distance wavelength transmission: nm TOD compensation = fs 3compressor: 1500 l/mm gratings / 140 mm wide / 1.2m separation wavelength transmission: nm TOD induced = fs 3fiber: 170 m long Single mode polarization maintaining TOD induced = fs 3 cutoff wavelength < 780 nm

HELMHOLTZ GEMEINSCHAFT VUV FEL ErEr Principal of electro-optical sampling PD Sampling: simple analysis balanced detector allows high sensitivity good synchronization required multi-shot method arbitrary time window possible ErEr Principal of temporal- wavelength correlation camera Chirp laser method: single shot method some more effort for laser and laser diagnostics required resolution due to laser ~ √t 0 · t chirp time window ~ 1-20ps

HELMHOLTZ GEMEINSCHAFT VUV FEL Space -time correlation method Timing o.k. EO-Crystal v ErEr camera v laser is „late“ v laser is „early“ laser

HELMHOLTZ GEMEINSCHAFT VUV FEL the phase shaper - principle actual shaper

HELMHOLTZ GEMEINSCHAFT VUV FEL Time structure and energy budget Ti:Sa oscillator pulses fiber 108 MHz OPA SHG 10% PM 0.01% Pockels cell 1 MHz Rotator SHG 92% 5% 91% stretcher SLM ~ 800 ns  t = 1600 ns 9.3 ns 1 MHz tunnel  t = 0 ns gated detector EO-crystal e-bunch 0.6% 10% 90% X % ~ 800 ns ~ 1600 ns Synchronized to electron beam at EO-crystal Synchronized to VUV-FEL beam at sample Pulse for SHG sampling the fiber length Pulse for SHG for reference 50% 92% 130 pJ 2.5 nJ 90% 10% 2*40 pJ 15 pJ 98% Feedback Fiber length Pump-probe experiment PM