TY - CPAPER
AU - Viefhaus, J.
TI - An Online Diagnostic Unit for FEL Photon Parameter Determination and Optimization
J2 - Proc. of FEL2015
AB - Originally developed for the Variable Polarization XUV Beamline P04 at PETRA III, an online diagnostic unit for beamline quality control was successfully applied to FEL radiation as well. The relevant photon properties include relative photon flux, photon energy and bandpass, beam position and especially the degree of linear polarization of the photon beam. The device consist of sixteen individual electron time-of-flight electron spectrometers which are oriented in a plane perpendicular to the incoming radiation. A gas-phase target (usually rare gases at pressures of about 10⁻⁰⁸ to 10⁻⁰⁶ hPa) with very low absorption allows to put the device in front of the user experiment for online diagnostics of the x-ray beam. The efficient time-of-flight method with flight times in the order of tens of ns together with a fast multi-channel digitizer system and multi-threaded data evaluation algorithms allows true online shot-by-shot visualization at high repetition rates with minimal delay. Results from different FEL sources showing the flexibility as well as the real-time capabilities of the system will be presented. This work was only made possible by fruitful collaborations and extensive support from the facilities PETRA III and FLASH (DESY, Hamburg), European XFEL (Hamburg), FERMI (Elettra, Sincrotrone Trieste) and LCLS (SLAC, Menlo Park).
PB - JACoW
CY - Geneva, Switzerland
ER -