Journal Article

PUBDB-2024-01980

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Thermoelastic effects in Bragg reflectors as a potential bottleneck for XFELs with megahertz repetition rate

Bahns, I. (Corresponding author)Extern*XFEL.EU* ; Rauer, P.Extern*XFEL.EU*DESY* ; Rossbach, J. ; Steinlechner, S. ; Sinn, H.

2024
Springer Nature London

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Please use a persistent id in citations: doi:10.1038/s42005-024-01581-1  doi:10.3204/PUBDB-2024-01980

Abstract: Bragg reflectors are essential for beam transport in X-ray free-electron laser (XFEL) facilities. On interaction with Bragg reflectors, a part of the pulse energy will be absorbed, causing the propagation of displacement waves due to rapid thermal expansion. It is suspected that these waves may cause stability problems for XFELs operating with megahertz repetition rates. Here, we experimentally investigate the displacement of a diamond Bragg reflector induced by an optical ultra-violet laser pulse, simulating XFEL pulses with mJ pulse energy, both at room temperature and cryogenic temperatures.Our experiment shows negligible damping of the displacement waves on μs timescales, which could cause disruption for subsequent XFEL pulses. We compare our measurements to a simulation framework based on the assumptions of local thermodynamic equilibrium and classical mechanics, observing reasonable agreement. Our results show that thermoelastic effects are critical for a reliable stability assessment of Bragg reflectors, but are often overlooked.

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Contributing Institute(s):

1. X-Ray Optics (XFEL_DO_ID_XRO)

Research Program(s):

1. 631 - Matter – Dynamics, Mechanisms and Control (POF4-631) (POF4-631)
2. 6G13 - Accelerator of European XFEL (POF4-6G13) (POF4-6G13)

Experiment(s):

1. Experiments at XFEL

Appears in the scientific report 2024

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