Physical insights and test stand results for the LANSCE-H surface converter source
- Edwin
- Ernest G.
- Edward G.
- Patrick D.
- Bruce J.
- Peter H.
- Gary
- Stuart
- Thomas J.
The Los Alamos Neutron Science Center (LANSCE) H{sup -} surface converter source has been under development for several years to reach 25-40 mA current with 7({pi}cm-mrad) lab emittance (95% beam fraction). The duty factor is 12% (120 Hz, 1 ms pulse length). Summary test stand results and interpretations for a six filament axial extraction H{sup -} source are presented. This source did produce 40-mA H{sup -} current, but with unacceptable emittance growth. More recently a fourth, modified LANSCE H{sup -} production source with radial H{sup -} extraction system has been constructed, and is presently undergoing tests. Currents up to 25mA H{sup -} have been observed with 20% emittance growth. This emittance growth may be acceptable for 800 MeV linac operations. A summary of physical principles of emittance growth mechanisms and converter physics are given. Significant upgrades to the LANSCE 800-MeV linac and Proton Storage Ring (PSR) operations can be realized by development of an if ion source with laboratory emittance of 7({pi}cm-mrad) at 95% beam fraction with 20-40mA H{sup -} current. The source beam energy is 80keV and the duty factor (df) is 12%. A six-filament version of the surface converter source with axial if beam extraction was developed in a collaborative effort between Lawrence Berkeley National (LBNL) and Los Alamos National Laboratories (LANL). Although this source did produce 40-mA H{sup -} current, an unexpected emittance growth factor of 2.5 made these higher current beams unacceptable for LANSCE operations. A subsequent decision was made to fabricate and develop a fourth production source to produce 25-mA H{sup -} current with an emittance growth of no greater than 20%. The source upgrade technology would be used in a 750-keV H{sup -}. injector B at LANSCE. Experiments and analysis on the six-filament axial extraction source will be reviewed in the next section. Evidence is given that at the higher discharge power characteristic of this source, two beams are formed at extraction. The two beams originate in surface (converter electrode) and volume processes. The third section summarizes recent work completed on the fourth production source with radial extraction. Effort is directed at increasing the if current without significantly increasing the discharge power, thus avoiding the two-beam emittance growth mechanism. All beam measurements were made on the LANSCE Ion Source Test Stand (ISTS), which is now computer controlled and may be operated on a 24 hour, 7-day/week bases.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 977834
- Report Number(s):
- LA-UR-04-6055; TRN: US1003734
- Resource Relation:
- Journal Volume: 763; Conference: Submitted to: 10th International Symposium on the Production and Neutralization of Negative Ions and Beams, September 14-17, 2004, Kiev, Ukraine
- Country of Publication:
- United States
- Language:
- English
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