Measurements of Momentum Halo Due to the Reduced RFQ Voltage During the LIPAc Beam Commissioning

Abstract

International audienceThe Linear IFMIF Prototype Accelerator, LIPAc, is being commissioned aiming in particular at validating the RFQ up to 5MeV beam acceleration. Eventually, the nominal beam of 5 MeV-125 mA in 1 ms/1 Hz pulsed mode was achieved in 2019. The beam operation has been resumed since July 2023 after long maintenance including recovery from unexpected problems in the RFQ RF system. This new phase aims at the commissioning of the full configuration except SRF linac, which is replaced by a temporary beam transport line. Focusing on the RFQ behavior, it will be interesting to operate it at higher duty especially for longer pulses. Indeed, a beam simulation study suggested that the beam extracted from the RFQ includes considerable momentum halo when the RFQ voltage reduces by a few percent, with a slight decrease of mean energy. It can be a potential source of quench like the mismatched beam in the cryomodule. This could be studied measuring the energy from the Time-of-Flight among multiple BPMs while monitoring beam loss around the dipole, where momentum halo should be lost. During the upcoming commissioning, we propose to study them by scanning the RFQ voltage