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TY - CONF AU - Gulliford, C.M. AU - Bartnik, A.C. AU - Berg, J.S. AU - Crittenden, J.A. AU - Quigley, P. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Beam Based Measurements of the CBeta Main Linac Cavity Alignment J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - Initial attempts at steering the beam through the CBETA main linac indicated the cavities were vertically offset with respect to the BPMs on either side of the linac. In particular, manual alignment of the beam in the first and last cavities suggested a vertical offset of roughly 5 mm. This work presents the results of beam based measurements of the individual cavity offsets taken during the CBETA Fractional Arc Test. With only a single cavity powered at a time, beam was injected at several different vertical offsets, the RF phase was scanned over 360 degrees, and the beam position was measured at the end of the cryomodule. We analyzed the data in two ways. We first compute the RMS spread in the measurements at a given position, and considered the offset with the minimum RMS spread to be the cavity offset. We also fit the measurements at a given phase to a line as a function of initial displacement, and use a model for the transfer matrix of the cavity and downstream drift to compute the offset. The two methods agree well, resulting in an average vertical offset of the main linac cavities of 4.0 plus/minus 1 mm. PB - JACoW Publishing CP - Geneva, Switzerland SP - 755 EP - 757 KW - cavity KW - linac KW - cryomodule KW - survey KW - acceleration DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPRB078 UR - http://jacow.org/ipac2019/papers/moprb078.pdf ER -