Target Induced Halo Formation and Collimation Following MAGIX at MESA
Date issued
Authors
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
License
Abstract
The Mainz Energy-recovering Superconducting Accelerator (MESA) is a recirculating electron linear accelerator (Linac), that is currently under construction in the Institute for Nuclear Physics at the Johannes Gutenberg-University Mainz. MESA will be able to operate in energy recovery linac (ERL) mode, in which the energy of the accelerated beam is recovered through subsequent deceleration. This technique enables reaching high beam powers and therefore high luminosities available for experiments with considerably less installed amplifier power compared to conventional Linacs. The Mainz Gas Internal Target Experiment (MAGIX) takes advantage of the MESA beam currents of initially up to 1 mA at 105 MeV beam energy available in ERL mode to realize a variety of nuclear physics experiments. These experiments aim for a luminosity of minimum 10^35 cm^-2 s^-1. The ERL mode requires recirculation of the accelerated beam through the accelerator after passing the target and degradation of the beam through the beam-target interaction must be limited to ensure proper beam transport for energy recovery. The beam degradation at MAGIX is governed by scattering of beam electrons on the target, which leads to beam halo formation after the target and induces beam losses in following accelerator sections. Collimators are needed in sections downstream of MAGIX to intercept the beam halo in order to control beam losses and the lost beam power leads to a reduction of ERL efficiency as well as radioactive activation of exposed equipment. The target induced beam degradation consequently limits the practically achievable luminosity at the experiment. The formation of the halo and the behavior of subsequently occurring beam losses for the envisaged MAGIX experiments at MESA are studied in simulations in this thesis. A suitable collimation system is presented in the following and the resulting activation of accelerator equipment is examined to estimate a luminosity limit for MAGIX operation in MESA ERL mode. The presented results show that the operation of hydrogen and helium targets at the aimed at luminosity is possible, whereas a restriction of luminosity is required for heavier target gases.