A system for online beam emittance measurements and proton beam characterization

Abstract

A system for online measurement of the transverse beam emittance was\ndeveloped. It is named $^{4}$PrOB$\\varepsilon$aM (4-Profiler Online Beam\nEmittance Measurement) and was conceived to measure the emittance in a fast and\nefficient way using the multiple beam profiler method. The core of the system\nis constituted by four consecutive UniBEaM profilers, which are based on silica\nfibers passing across the beam. The $^{4}$PrOB$\\varepsilon$aM system was\ndeployed for characterization studies of the 18~MeV proton beam produced by the\nIBA Cyclone 18 MeV cyclotron at Bern University Hospital (Inselspital). The\nmachine serves daily radioisotope production and multi-disciplinary research,\nwhich is carried out with a specifically conceived Beam Transport Line (BTL).\nThe transverse RMS beam emittance of the cyclotron was measured as a function\nof several machine parameters, such as the magnetic field, RF peak voltage, and\nazimuthal angle of the stripper. The beam emittance was also measured using the\nmethod based on the quadrupole strength variation. The results obtained with\nboth techniques were compared and a good agreement was found. In order to\ncharacterize the longitudinal dynamics, the proton energy distribution was\nmeasured. For this purpose, a method was developed based on aluminum absorbers\nof different thicknesses, a UniBEaM detector, and a Faraday cup. The results\nwere an input for a simulation of the BTL developed in the MAD-X software. This\ntool allows machine parameters to be tuned online and the beam characteristics\nto be optimized for specific applications.\n