Heavy ion linac as a high current proton beam injector

Abstract

A significant part of the experimental program at Facility for Antiproton and Ion Research (FAIR) is dedicated to pbar physics requiring a high number of cooled pbars per hour. The primary proton beam has to be provided by a 70 MeV proton linac followed by two synchrotrons. The new FAIR proton linac will deliver a pulsed proton beam of up to 35 mA of 36 μs duration at a repetition rate of 4 Hz (maximum). The GSI heavy ion linac (UNILAC) is able to deliver world record uranium beam intensities for injection into the synchrotrons, but it is not suitable for FAIR relevant proton beam operation. In an advanced machine investigation program it could be shown that the UNILAC is able to provide for sufficient high intensities of CH 3 beam, cracked (and stripped) in a supersonic nitrogen gas jet into protons and carbon ions. This advanced operational approach will result in up to 3 mA of proton intensity at a maximum beam energy of 20 MeV, 100 μs pulse duration and a repetition rate of up to 2.7 Hz delivered to the synchrotron SIS18. Recent linac beam measurements will be presented, showing that the UNILAC is able to serve as a proton FAIR injector for the first time, while the performance is limited to 25% of the FAIR requirements.

High brilliance uranium beams for the GSI FAIR

“…One of the crucial quantities at a fixed beam intensity to characterize the high current capability of a synchrotron injector is the horizontal beam emittance. The high current (2 mA) proton beam emittance growth inside the Alvarez was measured to be 17% (rms) [1] (Fig. 1).…”

“…High current uranium beam machine experiments at the GSI-High Current Injector (HSI) and the gas stripper section were conducted in October 2015 and July 2016, while at this time, due to work on the rf-amplifier system of the UNILAC post stripper (Alvarez), only three of the five Alvarez tanks were available. The achievable high current beam brilliance at injection into the heavy ion synchrotron SIS18 is currently estimated only by using front-to-end high current measurements with a proton beam performed in 2014 [1].…”

FLASH radiotherapy with carbon ion beams

“…A large-scale research synchrotron like the one at the GSI Helmholtzzentrum can currently extract about 1 × 10 10 carbon ions per spill. The configuration with the MUCIS source (operated with CH 4 gas) 76 and the UNILAC as an injector for the GSI SIS-18 synchrotron can presumably deliver even higher intensities for carbon ions (and protons). However, the GSI synchrotron can no longer be used for patient irradiation because the therapy pilot project 8,77 was discontinued 12 years ago.…”

Spallation-based neutron target for direct studies of neutron-induced reactions in inverse kinematics

“…The universal linear accelerator UNILAC and the 18-T•m heavy-ion synchrotron SIS-18 are the driver accelerators at GSI in Darmstadt (Germany). Proton intensities of up to 2.1 × 10 11 protons per pulse have routinely been achieved [17]. The magnetic rigidity of 18 T•m allows to accelerate protons to energies of 4.5 GeV.…”