A new pulsed cryogenic proton source cooled by liquid helium

Abstract
A new cryogenic proton source with liquid helium cooling system is presented. The anode is cooled down to about 4.2 K. A hydrogen ice is produced on the surface and used as the ion source. Proton beams of a current density 21 A/cm2 at 200 kV are extracted with good reproducibility. This new ion source is expected to be a proton source without contamination by nonprotonic ions.