1. ESRF interest & commitment to (ultra-) fast science with X-rays Kees Scheidt Diagnostics group, Machine division

2. ESRF interest & commitment to (ultra-) fast science with X-rays 1)Thorough tests of the quasi-isochronous Storage Ring in 1995 : inadequate since incompatible with high-intensity demands so : typical bunch length remains ~100ps (fwhm) at 5mA single bunch 2)Operation of various filling patterns to satisfy the whole user community, including specialized time-resolved beamlines 3) Development of X-ray time resolved detector for sub-pico second time resolved diffraction experiments

5. ultra-fast X-ray diffraction experiments that use the pump-probe technique with : a 100femtoSec Laser light pump pulse and a 100picoSec X-ray probe pulse the ultimate time resolution depends on : 1) intrinsic time resolution of the Streak Camera for X-rays 2) the quality of synchronization Objective :1) sub-picoSec time resolution 2) high quality data by accumulation over many shots

6. the Streak-Tube : improved version of commercial model (Photonis)

8. 10 picosec 5mm

9. 460ps fwhm result when accumulating 900 shots

10. Critical laser issues : 1)Amplitude stability 2)Contrast (or pre-pulse energy variations)

12. Sensitivity for hard X-rays is low due to poor DQE of photo-cathodes decreasing DQE for increasing Energy best : Cesium-Iodide (100) low : Potassium-Iodide (10) Potassium-Bromide poor : Gold (1)

13. Conclusion (1): Optical synchronization by a GaAs photo-switch between a femtosec-laser and a Streak-Camera attains values <100fs when : -Laser energy>25uJ per pulse -Laser stability0.25% rms -Laser contrast>10 4 In these conditions (obtained after delicate adjustments) the time resolution of the system in accumulation mode is determined by the tube’s intrinsic time resolution, at ~500fs fwhm for UV light The exact time resolution for hard X-rays was never assessed since various attempts to produce a sub-pico sec event in an appropriate Pump-Probe experiments were without success.

14. Conclusion (2): The accumulating Jitter-Free X-ray streak camera for sub-pico sec pump-probe experiments was Not a scientific success due to : 1)The difficulty of conceiving an appropriate experiment 2)The required delicate adjustments on laser, photo-switch and streak-camera making it not user-friendly 3)The particular limitations of a Streak-Tube detector: a)No real space-dimension b) Low sensitive photo-cathode material