Injector linac stability requirements for high precision experiments at MESA

8th International Particle Accelerator Conference

Hug, F.^1 ; Heine, R.^1

Institute for Nuclear Physics, Johannes Gutenberg-Universität Mainz, Johann-Joachim-Becher Weg 45, Mainz

55128, Germany^1

关键词: Accelerating fields;    Construction stages;    Longitudinal dispersions;    Operating condition;    Particle physics experiments;    Polarized electrons;    Stability requirements;    Superconducting accelerator;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/874/1/012012/pdf
DOI  :  10.1088/1742-6596/874/1/012012

来源: IOP

【 摘 要 】

MESA is a recirculating superconducting accelerator under construction at Johannes Gutenberg-Universität Mainz. It will be used for high precision particle physics experiments in two different operation modes: external beam (EB) mode and energy recovery (ERL) mode. The operating beam current and energy in EB mode is 0.15 mA with polarized electrons at 155 MeV. In ERL mode an unpolarized beam of 1 mA at 105 MeV will be available. In a later construction stage of MESA the beam current in ERL-mode shall be upgraded to 10 mA. In order to achieve high beam stability and low energy spread in recirculating operation for external beam the acceleration in the main linac sections will be done on a certain phase with respect to the maximum of the accelerating field (off crest) while the return arcs provide longitudinal dispersion. On specific longitudinal working points this can result in a setting where any RF phase or magnitude jitters from main linac do not contribute to the resulting energy spread of the final beam at all. Then the resulting energy spread of the beam at the experiment is mostly determined by the beam properties provided by the injector linac. On the other hand the acceleration in ERL operation mode most likely needs to be done on crest of the accelerating field aiming for the highest efficiency in the energy recovering process albeit we are currently investigating different recirculation schemes for the ERL mode as well. Using on crest acceleration the achievable energy spread is determined by the longitudinal phase space properties behind the injector linac again but mostly by the bunch length of the beam injected to the main linac. Within this contribution we will investigate the requirements on the stability of the MESA injector linac MAMBO for achieving the experimental goals under both operating conditions.