A fast beam position monitor for dynamic proton radiography at the Los Alamos Neutron Science Center

The Proton Radiography facility at LANSCE uses 800 MeV protons delivered by a LINAC for imaging of dynamic experiments. One challenge in the image analysis is obtaining precise measurements of the beam position for image correction. A new prototype of a beam profile monitor utilizing plastic scintillating fibers aims to solve this problem. The monitor has eight fibers each in the horizontal and vertical directions to obtain the beam profile in the x and y directions. The spacing between the fibers is varied so that there are four fibers to be used in each direction for each of the three field of view sizes corresponding with the three levels of magnification available. The fibers are connected to photodiodes from which the signal can be read out in real time using oscilloscopes. The monitor has been shown to be able to be used during dynamic imaging experiments without interruption on image quality due to it being sufficiently thin and made of a light plastic. Thus far, data collected has shown the prototype to be successful for image analysis correction and further refinements are being made for the 2023 beam run cycle to ensure that sensitivity is either equal or can be corrected for between the different channels.