Development of a proton energy monitoring device for a high count rate environment

We developed a standalone data acquisition module that could digitize a maximum of 3 million samples per second for proton energy measurements. The module also includes a pile-up separation algorithm so that pile-up events could be rejected efficiently. Proton energy monitoring was performed by using the 45-MeV proton beam from the MC-50 cyclotron at the Korea Institute of Radiological and Medical Sciences. The energy profile of the proton beam was measured with a LYSO (Cerium-doped Lutetium Yttrium Ortho-silicate) crystal scintillator with a 40-ns decay time. The scintillator was coupled to a Photomultiplier tube, and its output signal was fed into the signal digitization module, followed by a preamplifier. The digitized signal was sent to a computer via Ethernet. We measured the energy profiles at different transverse beam positions. We found that the energy resolution become worse when pile-up was increased because of the high count rate at the central region. The energy resolution was improved when the pile-up rejection algorithm was applied.