Lee, S.H. Jansma, W.G. Siy, A.E. Sorsher, S. Suthar, K.J. Trakhtenberg, E. Waldschmidt, G.J. Zholents, A. JACoW Publishing Geneva, Switzerland 2673-5520 978-3-95450-229-5 10.18429/JACoW-MEDSI2020-WEPB04 English 273-275 GUI vacuum wakefield Windows alignment Contribution to a conference proceedings 2021 2021-10 https://doi.org/10.18429/JACoW-MEDSI2020-WEPB04 https://jacow.org/medsi2020/papers/wepb04.pdf An effort to build Argonne’s Sub-THz AcceleRator (A-STAR) for a future multiuser x-ray free-electron laser facility proposed in [1] is underway at Argonne National Laboratory. The A-STAR machine will utilize a compact collinear wakefield accelerator (CWA) assembled in modules. To extract the wakefield and monitor beam position downstream of each module, a 45-mm-long transition section (TS) has been proposed and designed. This paper will discuss the design and fabrication chal-lenges for production of the TS.