Operation of a DC large aperture volume-production H sup minus source
In testing a multicusp volume-production H{sup {minus}} ion source (20 cm diameter, 23 cm long), we optimized the gas pressure, the plasma electrode bias potential and the magnetic filter. At the optimum pressure of 9 mT, the H{sup {minus}} beam output increased linearly with discharge power. The maximum H{sup {minus}} beam, measured with a current transformer downstream of the accelerator, was 100 mA while using a 6.67 cm{sup 2} aperture. Presently we are limited by overheating of the cathodes by the plasma ions. Under similar discharge conditions the maximum H{sup {minus}} current density was found to vary as a{sup {minus}0.7} where a is the aperture radius. Results from emittance measurements showed that the effective H{sup {minus}} ion temperature increased with a for a {gt} 0.8 cm. Thus the brightness of the beam decreased with increasing aperture radius. Operating the source with cesium would increase the H{sup {minus}} output however our accelerator must be improved to avoid breakdowns caused by the cesium contamination. 8 refs., 6 figs.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5570710
- Report Number(s):
- LBL-27421; CONF-890703-23; ON: DE90002668; TRN: 89-031358
- Resource Relation:
- Conference: International conference on ion sources, Berkeley, CA (USA), 10-14 Jul 1989
- Country of Publication:
- United States
- Language:
- English
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