Speaker
Description
Cavity-based X-ray free-electron lasers (CBXFELs) require tunable X-ray crystal cavities to broaden their practical utility. However, the previously proposed four-crystal bow-tie design has a lateral footprint comparable to the undulator length, limiting its deployment in accelerator tunnels. Here, we introduce a compact, broadly tunable X-ray cavity comprising six Bragg-reflecting crystals arranged in a non-coplanar three-dimensional geometry analogous to a pair of optical retroreflectors. This architecture reduces the lateral dimension to approximately 0.5 m while enabling enhanced photon-energy tunability across a wide hard-X-ray range. Although the non-coplanar geometry introduces polarization coupling absent in coplanar configurations, our theoretical analysis shows that polarization mixing vanishes at the center of the Bragg reflection and remains below 5% over a substantial portion of the reflection range, with the exact value depending on the Bragg angle. These results establish non-coplanar multi-crystal cavities as a viable and practical route toward compact, tunable X-ray resonators for CBXFEL implementation.
Representative optical designs will be presented, with details on tuning range, bandwidth, polarization mixing, and other design considerations.
Funding Agency
This research used resources of the Advanced Photon Source at Argonne National Laboratory, a DOE Office of Science user facility, under Contract No. DE-AC02-06CH11357.
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