X-ray diagnostics for the cavity-based x-ray free-electron laser project

The success of x-ray free-electron lasers (XFELs) in recent years has greatly advanced many scientific fields. However, most of these XFELs suffer from a low longitudinal coherence and instabilities due to the stochastic start-up process. A cavity-based x-ray free-electron laser (CBXFEL) is a possible future direction in the development of fully coherent and stable x-ray sources. One of the challenges of a CBXFEL is the requirement for the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi mathvariant="normal">μ</a:mi><a:mi mathvariant="normal">m</a:mi><a:mtext>−</a:mtext><a:mi>sized</a:mi></a:mrow></a:math> electron bunches to fully overlap in three dimensions with the circulating <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mi mathvariant="normal">μ</e:mi><e:mi mathvariant="normal">m</e:mi><e:mtext>−</e:mtext><e:mi>sized</e:mi></e:mrow></e:math> x-ray pulses in an x-ray cavity tens or hundreds of meters long. We present here the development of an x-ray diagnostics system for accurate alignment of x-ray beams in the CBXFEL cavity. The system was developed within the framework of a CBXFEL research and development collaboration among Argonne National Laboratory, SLAC National Accelerator Laboratory, and Spring-8. All the designed diagnostic components have been fully characterized at the Advanced Photon Source to demonstrate a capability for sub-<i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi mathvariant="normal">μ</i:mi><i:mi>rad</i:mi></i:math> angular and <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mrow><l:mi mathvariant="normal">μ</l:mi><l:mi mathvariant="normal">m</l:mi></l:mrow></l:math> spatial alignment of the CBXFEL cavity. Published by the American Physical Society 2024