“Two-dimensional distribution reconstruction and emittance diagnostics of proton beam phase space using tomography”

A two-dimensional distribution of a proton beam in phase space was reconstructed using beam profile data and a tomography technique in this study. These beam profile data were acquired by a wire scanner under various beam optics conditions, employing an experimental procedure identical, in principle, to the quadrupole magnet (QM) scan method to diagnose beam parameters. According to beam optics, beam profile data measured while changing the QM current is the same as that measured while rotating the beam distribution in the phase space. Thus, the set of the beam profile data can be converted into a sinogram, serving as source data for tomography. A filtered-back-projection (FBP) method is applied to reconstruct the beam distribution from this sinogram. However, if the range and distribution of the rotation angle are not sufficient, the reconstructed distribution data will be inaccurate, which will negatively affect beam parameter evaluation. To solve this limitation, a simulator incorporating the beam optics theory with the tomography was developed to derive an efficient experimental condition. The beam distribution in the phase space was successfully reconstructed, and the beam parameters evaluated from this were also confirmed to match well with the values obtained from the QM scan.