Status and operation of the Linac4 ion source prototypes

Abstract

CERN's Linac4 45 kV H-ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma and pulsed high voltages are described. The first experimental results of two prototypes relying on 2MHz RF-plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H-beam of 16-22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator and chopper of Linac4.

CERN’s Linac4 H− sources: Status and operational results

“…Two cesiated surface prototypes 4 were produced, the first one (IS02a) is equipped with a 4 turn solenoid and its ceramic chamber sealed with O-rings. It was operated at the test stand from mid-October 2013 to mid-April 2014 with the beam extraction optics dedicated for volume production in order to safely operate in volume and cesiated production modes.…”

“…The ion source of Linac4 shall eventually provide H -ions at 45 keV energy, in pulses of 0.5 ms duration and 80 mA intensity within a transverse rms emittance of 0.25 ·mm·mrad. The path chosen towards these beam properties includes three types of ion sources and beam intensity stages; 2 MHz Radio Frequency (RF) driven 20 mA H -source 2 relying on volume production 3 , 2 MHz RF-driven 40 mA cesiated surface H -source 4 inspired from the single cesiation approach successfully operating at the Spallation Neutron Source (SNS) 5 and an upgrade to 45 kV operation voltage of the Magnetron H -source 6 successfully operating at Brookheaven National Laboratory (BNL).…”

Cs-doped Mo as surface converter for H−/D− generation in negative ion sources: First steps and proof of principle

“…Consorzio RFX is currently building the full size ITER prototype sources [8,9]. Negative ions are also foreseen to be used by the proton synchrotron booster at CERN [10]. Negative hydrogen ion sources for ITER neutral beam injectors are based on the conversion of positive ions and neutrals into negative ions on a converter surface.…”

High-Power Proton Linac Technology at CERN

“…The first Linac4 H − source [13] to be prototyped was an un-cesiated RF volume source based on a DESY design. This source delivered up to 20 mA of H − and was used for the commissioning of the Linac4 front-end.…”