CW/Pulsed H - Ion beam generation with PKU Cs-free 2.45 GHz microwave driven ion source

Abstract

Circular accelerators used for positron emission tomography (PET, i.e. accelerator used for make radio isotopes) need several mA of CW H - ion beam for their routine operation. Other facilities, like Space Radio-Environment Simulate Assembly (SPRESA), require less than 10 mA pulsed mode H - beam. Caesium free negative hydrogen ion source is a good choice for those facilities because of its compact structure, easy operation and low cost. Up to now, there is no H - source able to produce very intense H - beams with important variation of the duty factor [1] . Recently, a new version of 2.45 GHz microwave H - ion source was designed at PKU, based on lessons learnt from the previous one. This non cesiated source is very compact thanks to its permanent magnet configuration. Special attention was paid on the design of the discharge chamber structure, electron dumping and extraction system. Source test to produce H - ion beams in pulsed and CW mode was carried out on PKU ion source test bench. In CW mode, a 10.8 mA/30keV H - beam with rms emittance about 0.16 π ·mm·mrad has been obtained with only 500 W rf power. The power efficiency reaches 21 mA/kW. In pulsed mode with duty factor of 10% (100Hz/1ms), this compact source can easily deliver 20 mA H - ion beam at 35 keV with rms emittance about 0.2 π ·mm·mrad when RF power is set at 2.2 kW (peak power). Several hour successive running operation in both modes and totaling more than 200 hours proves its high quality. The outside dimension of this new H - source body is φ116 mm × 124 mm, and the entire H - source infrastructure, including rf matching section, plasma chamber and extraction system, is φ310 ×180 mm. The high voltage region is limited with in a φ310 mm × 230 mm diagram. Details are given in this paper.