HELMHOLTZ GEMEINSCHAFT VUV FEL VUV FEL HELMHOLTZ GEMEINSCHAFT

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HELMHOLTZ GEMEINSCHAFT VUV FEL

HELMHOLTZ GEMEINSCHAFT VUV FEL

VUV FEL HELMHOLTZ GEMEINSCHAFT Streak camera monitoring of the arrival timing jitter Stefan Düsterer

VUV FEL HELMHOLTZ GEMEINSCHAFT Streak camera monitoring of the arrival timing jitter Stefan Düsterer for the VUV - FEL Team E. Plönjes, J. Feldhaus and many others + MBI- Berlin + Lund laser center + DCU Dublin + LURE Paris

The goal: Time-resolved measurements at the FEL VUV FEL HELMHOLTZ GEMEINSCHAFT fs-excitation AND fs

The goal: Time-resolved measurements at the FEL VUV FEL HELMHOLTZ GEMEINSCHAFT fs-excitation AND fs – detection is needed by BESSY Berlin VUV-VUV experiments Ø Many interesting processes are triggered by visible rather than by VUV light VUV-optical experiments Ø The visible laser is much more flexible Ø larger time-delay (ns. . . ) Ø variable pulse length / chirping Ø change color, polarization. . . Problem: jitter between the two independent sources

Layout of the optical laser system VUV FEL HELMHOLTZ GEMEINSCHAFT Laser parameters Wavelength: Pulse

Layout of the optical laser system VUV FEL HELMHOLTZ GEMEINSCHAFT Laser parameters Wavelength: Pulse duration: pulse energy for single laser pulse: Rep rate 790 nm. . . 830 nm ~100 fs 50 - 100 µJ 1 MHz

Layout: pump-probe experiments VUV FEL HELMHOLTZ GEMEINSCHAFT 5 exp. stations FEL pulse Optical pulse

Layout: pump-probe experiments VUV FEL HELMHOLTZ GEMEINSCHAFT 5 exp. stations FEL pulse Optical pulse optical laser

The temporal overlap at the experiment VUV FEL HELMHOLTZ GEMEINSCHAFT Overlapping the FEL Experimental

The temporal overlap at the experiment VUV FEL HELMHOLTZ GEMEINSCHAFT Overlapping the FEL Experimental chamber for the first pump-probe experiments and the optical pulse X-ray streak camera

(V)UV streak camera at the experiment VUV FEL HELMHOLTZ GEMEINSCHAFT The best so far

(V)UV streak camera at the experiment VUV FEL HELMHOLTZ GEMEINSCHAFT The best so far in UV: Zenghu Chang group, Kansas streak camera (Berkeley) ( H. Padmore, R. Falcone, A. Mac. Phee …) However: Average over 6000 shots 266 nm More about the camera we need: Andrew – next talk single shot 30 nm (+266 nm) With courtesy from Howard Padmore

X-ray streak camera at experiment HELMHOLTZ GEMEINSCHAFT Good idea , however … Ø Not

X-ray streak camera at experiment HELMHOLTZ GEMEINSCHAFT Good idea , however … Ø Not simple to integrate into experiment ( intensity, geometry …) Ø great to find temporal overlap at experiment Ø hard to use as online jitter / drift monitor Ø User facility Ø jitter / drift detection should be independent of user experiment VUV FEL

What am I gonna talk about ? VUV FEL HELMHOLTZ GEMEINSCHAFT Using an optical

What am I gonna talk about ? VUV FEL HELMHOLTZ GEMEINSCHAFT Using an optical streak camera to monitor the dipole radiation

Layout: experimental hall VUV FEL HELMHOLTZ GEMEINSCHAFT 5 exp. stations FEL pulse Optical pulse

Layout: experimental hall VUV FEL HELMHOLTZ GEMEINSCHAFT 5 exp. stations FEL pulse Optical pulse VUV pulse Electrons optical laser streak camera Dipole radiation

HELMHOLTZ GEMEINSCHAFT The problem. . . VUV FEL IR. . . 100 ms. .

HELMHOLTZ GEMEINSCHAFT The problem. . . VUV FEL IR. . . 100 ms. . . FEL systematic drifts within changes from macropulse the macropulse to macropulse ~300 fs ~ 600 fs . . . hours. . . longterm drifts > ps the pulses are NOT drawn to scale !

Strategies for using the optical streak camera HELMHOLTZ GEMEINSCHAFT systematic drifts within the macropulse

Strategies for using the optical streak camera HELMHOLTZ GEMEINSCHAFT systematic drifts within the macropulse ~300 fs VUV FEL Photoelectron s § Jitter close to resolution of streak camera (peak detection) Reinhard - shot § Reprate too low / space charge problems for single EOS Thursday later § Other methods are better suited for 1 MHz detection § Synchroscan – low camera jitter – integrate over macropulse Macropulse to macropulse ~ 600 fs § 10 Hz (1 D binning) readout works § rising edge for each macropulse will be monitored ( ~300 fs) § continuous monitoring -> detection of long term drifts longterm drifts > ps § using as feedback signal for RF shifter in laser

Two photon Above Threshold Ionization (ATI) M. Meyer, P. O´Keeffe LURE VUV FEL HELMHOLTZ

Two photon Above Threshold Ionization (ATI) M. Meyer, P. O´Keeffe LURE VUV FEL HELMHOLTZ GEMEINSCHAFT Superposition of visible and VUV pulse in a nobel gas jet Electron spectrometer VUV Visible fs laser pulse gas jet

Single-shot FEL -IR cross correlator VUV FEL HELMHOLTZ GEMEINSCHAFT visible strong fs- laser pulse

Single-shot FEL -IR cross correlator VUV FEL HELMHOLTZ GEMEINSCHAFT visible strong fs- laser pulse Gas jet FEL SASE pulse • resolution < 50 fs • Parasitic – does not destroy the FEL pulse Electron energy Photo electrons (1 D) imaging electron spectrometer spatial coordinate

Single-shot FEL -IR cross correlator VUV FEL HELMHOLTZ GEMEINSCHAFT (Proposal by M. Drescher, Universität

Single-shot FEL -IR cross correlator VUV FEL HELMHOLTZ GEMEINSCHAFT (Proposal by M. Drescher, Universität Bielefeld)

Strategies for using the optical streak camera VUV FEL HELMHOLTZ GEMEINSCHAFT systematic drifts within

Strategies for using the optical streak camera VUV FEL HELMHOLTZ GEMEINSCHAFT systematic drifts within the macropulse ~300 fs § Jitter close to resolution of streak camera (peak detection) § Reprate too low / space charge problems for single shot § Other methods are better suited for 1 MHz detection § Synchroscan – low camera jitter – integrate over macropulse Macropulse to macropulse ~ 600 fs § 10 Hz (1 D binning) readout works § rising edge for each macropulse will be monitored ( ~300 fs) § continuous monitoring -> detection of long term drifts longterm drifts > ps § using as feedback signal for RF shifter in laser

Layout of the dipole radiation beam line VUV FEL HELMHOLTZ GEMEINSCHAFT e 5 m

Layout of the dipole radiation beam line VUV FEL HELMHOLTZ GEMEINSCHAFT e 5 m electrons 4 Spherical collection mirror 2” diameter – 2. 3 m focal length → 20 mrad acceptance ~ 5 107 visible photons ev u ac a b ted e lin m a

Location of the “dipole experiments” VUV FEL HELMHOLTZ GEMEINSCHAFT Laser hutch 90° off-axis parabola

Location of the “dipole experiments” VUV FEL HELMHOLTZ GEMEINSCHAFT Laser hutch 90° off-axis parabola (4”) to focus on slit 40 µm spot size - ZEMAX simulation-

Emission geometry – principle limits ? VUV FEL HELMHOLTZ GEMEINSCHAFT Collecting mirror R=3. 6

Emission geometry – principle limits ? VUV FEL HELMHOLTZ GEMEINSCHAFT Collecting mirror R=3. 6 m → the electron bunch shape is accurately mapped onto the dipole light Electron trajectory Rays projected to object plane Path length difference between different rays on the arc < 3 fs Different rays projected to object plane ~ opening angle 3 10 mrad → 4 fs 20 mrad → 30 fs

Another problem: Dispersion VUV FEL HELMHOLTZ GEMEINSCHAFT Dipole light is white light Vacuum window

Another problem: Dispersion VUV FEL HELMHOLTZ GEMEINSCHAFT Dipole light is white light Vacuum window (3 mm) Bandwidth: temporal spread Streak camera lens temporal spread 400 nm 400 fs 12 ps 50 nm 50 fs 1. 7 ps 10 nm 10 fs 0. 3 ps Ways around : ● use band-pass filter (tremendous loss of photons) ● all reflective optics (expensive) ● focus directly onto the cathode (? ? ) ● don’t use a streak camera …. Measurements : TTF Phase I by Ch. Gerth

Streak camera test – synchroscan, 2 ps resolution VUV FEL HELMHOLTZ GEMEINSCHAFT Resolution of

Streak camera test – synchroscan, 2 ps resolution VUV FEL HELMHOLTZ GEMEINSCHAFT Resolution of arrival time jitter expected to be 300 fs measurements by Ingo Will, MBI Berlin The delay between two short laserpulses can be determined with a reproducability of <100 fs (FWHM) – despite a camera resolution of 2 ps !

What am I gonna talk about ? VUV FEL HELMHOLTZ GEMEINSCHAFT Next topic optical

What am I gonna talk about ? VUV FEL HELMHOLTZ GEMEINSCHAFT Next topic optical correlation between the dipole light and the laser

Optical correlation VUV FEL HELMHOLTZ GEMEINSCHAFT fs-laser Non-linear crystal Dipole radiation Line focus

Optical correlation VUV FEL HELMHOLTZ GEMEINSCHAFT fs-laser Non-linear crystal Dipole radiation Line focus

Test experiment - setup HELMHOLTZ GEMEINSCHAFT Timing from 800 nm, 80 fs. , 10

Test experiment - setup HELMHOLTZ GEMEINSCHAFT Timing from 800 nm, 80 fs. , 10 Hz repetition rate, ~2 m. J Ti: Sapphire laser. CCD, PSD Oscilloscope SHG imagine lens KDP β SHG Delay stage, ΔL BS Variable Attenuator τ = ΔL/ccos(β/2) t 0 Freq. Doubled light t 0+τ VUV FEL

Test experiment having 5 x 107 photons /pulse VUV FEL HELMHOLTZ GEMEINSCHAFT 1015 photons

Test experiment having 5 x 107 photons /pulse VUV FEL HELMHOLTZ GEMEINSCHAFT 1015 photons + 5 x 107 photons → 106 sum frequency photons Single shot detection with 1 MHz readout 30 fs resolution (in demo experiment) in 6 ps window

Conclusions HELMHOLTZ GEMEINSCHAFT Multiple (redundant) jitter diagnostics will be used (2 EOS, Dipole radiation,

Conclusions HELMHOLTZ GEMEINSCHAFT Multiple (redundant) jitter diagnostics will be used (2 EOS, Dipole radiation, Photoelectrons, x-ray streak) to find out which is best suited ( XFEL) • time overlap at the experiments – Use x-ray streak camera “downstream” experiment (<1 ps res. ) • Optical streak camera – Monitor macro pulse to macro pulse jitter ( ~300 fs res. ) – Use as feedback for long term drifts • Optical correlation +FEL and Dipole radiation – ~ 30 fs resolution – Detection at 1 MHz VUV FEL

VUV FEL HELMHOLTZ GEMEINSCHAFT . . .

VUV FEL HELMHOLTZ GEMEINSCHAFT . . .

ps - timing tool VUV FEL HELMHOLTZ GEMEINSCHAFT Simple way to get ps overlap

ps - timing tool VUV FEL HELMHOLTZ GEMEINSCHAFT Simple way to get ps overlap – just measuring charge ? Holzman et al. Appl. Phys Lett. 76, 134 (2000) Single photoconductive switch 2 switches second one grounds the first at ps delay