Measurement of gigawatt radiation pulses from a vacuum and extreme ultraviolet free-electron laser

Abstract

In order to measure the photon flux of highly intense and extremely pulsed vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) radiation in absolute terms, we have developed a gas-monitor detector which is based on the atomic photoionization of a rare gas at low particle density. The device is indestructible and almost transparent. By first pulse-resolved measurements of VUV free-electron laser radiation at the TESLA test facility in Hamburg, a peak power of more than 100 MW was detected. Moreover, the extended dynamic range of the detector allowed its accurate calibration using spectrally dispersed synchrotron radiation at much lower photon intensities.

Operation of a free-electron laser from the extreme ultraviolet to the water window

“…In the latter, the FEL typically produces up to 30 radiation pulses (five times per second). The FEL pulse energies were measured using microchannel plates (MCPs) (29)and gas monitor detectors (30). The EUV spectra of the FEL fundamental mode and its harmonics were measured using three different grazing incidence spectrometer systems.…”

Non-thermal desorption/ablation of molecular solids induced by ultra-short soft x-ray pulses

“…The operation of FLASH and process of ultra-intense soft x-ray radiation generation in this nearly 300m long laser system is described in [1][2][3]. Exiting the undulator, the laser beam propagates along an ultra-high vacuum (UHV) beamline involving several diagnostic devices such as pulse energy measuring gas monitor detector (GMD) [23], a variable line spacing grating spectrometer (VLS) [24], optional ionizing gas monitor measuring the beam profile, etc. A gas attenuator is used to vary the average pulse energy and a pair of selectable circular apertures allows the suppression of beam pointing instability and reduces imperfections of the beam profile in the far field.…”

A femtosecond X-ray/optical cross-correlator

“…The FEL was operated at a macro bunch repetition rate of 5 Hz consisting of bunch-trains of 30 micro-bunches with 2µs separation (500 kHz). The pulse energies reached up to 16µJ, as measured through the facility gas monitor detector 29 and independently by an intensity monitor within the PG2 beamline. With a spot size of (395 ± 23)µm x (274 ± 14)µm 30 the fluence stays well below the optical damage threshold of the GaAs surface (50 mJ/cm 2 for 30 fs pulse length at 800 nm) 31 .…”