Implementation of longitudinal phase space tomography at MedAustron

Abstract

MedAustron is an ion therapy facility located in Wiener Neustadt, Austria, which uses third order resonant slow extraction to deliver protons and carbon ions for irradiation. The currently ongoing extensive studies of different extraction mechanisms, as well as general interest in the behaviour of the beam in the longitudinal phase space from injection to extraction motivate the implementation a new diagnostic tool. To further the understanding of longitudinal beam dynamics, orbit pick-up signals are evaluated using longitudinal tomography. This technique, which is well-established in other accelerator facilities, has been successfully implemented at MedAustron. Its iterative reconstruction algorithm relies on longitudinal profiles obtained from orbit pick-ups, along with machine and optics parameters, such as circumference and transition energy. The turn-by-turn datanecessary for reconstruction was acquired with two systems: single acquisition distribution system (SADS) and a micro-telecommunication computing architecture (μTCA)-structure. Of particular interest is the comparison between collected data and its reconstruction of the longitudinal phase space of the two acquisition systems, as MedAustron plans to upgrade its low-level radio frequency system using the μTCA-crate. To ensure suitability and adaptability of the measurement set-ups, systematic measurements describing regular operations with clinical beams were undertaken. Additionally, the accuracy of the tomographic reconstruction was evaluated in scenarios where the beam was manipulatedand benchmarked against simulation, using the Beam Longitudinal Dynamics (BLonD) tracking code. These mismatched longitudinal phase space distributions were more accurately reconstructed with 1.4× the operationally set, nominal radio frequency (RF) voltage.