Author :
Molloy, S. ; Frisch, J. ; May, J. ; McCormick, D. ; Smith, T. ; Baboi, N. ; Hensler, O. ; Petrosyan, L. ; Eddy, N. ; Piccoli, L. ; Rechenmacher, R. ; Ross, M. ; Wendt, M. ; Napoly, Olivier ; Paparella, Rita C. ; Simon, Claire
Abstract :
It is well known that an electron beam excites higher order modes (HOMs) as it passes through an accelerating cavity. The properties of the excited signal depend not only on the cavity geometry, but on the charge and trajectory of the beam. It is, therefore, possible to use these signals as a monitor of the beam´s position. Electronics were installed on all forty cavities present in the FLASH linac in DESY. These electronics filter out a mode known to have a strong dependence on the beam´s position, and mix this down to a frequency suitable for digitisation. An analysis technique based on singular value decomposition (SVD) was developed to calculate the beam´s trajectory from the output of the electronics. The entire system has been integrated into the FLASH control system.
Keywords :
accelerator cavities; accelerator control systems; electron beams; linear accelerators; nuclear electronics; particle beam diagnostics; DESY; FLASH control system; FLASH linac; SVD; beam position monitor; beam trajectory; cavity geometry; electron beam excitation; electronic filter; higher order mode excitation; singular value decomposition; superconducting accelerating cavity; Acceleration; Data mining; Electron beams; Filters; Frequency; Geometry; Monitoring; Particle beams; Particle measurements; Position measurement;
