Initiation of long, free-standing Z-discharges by CO2 laser gas heating
High current discharge channels can neutralize both current and space charge of very intense ion beams. Therefore they are considered as an interesting alternative for the final focus and beam transport in a heavy ion beam fusion reactor. At the GSI accelerator facility, 50 cm long, stable, free-standing discharge channels with currents in excess of 40 kA in 2 to 25 mbar ammonia (NH{sub 3}) gas are investigated for heavy ion beam transport studies. The discharges are initiated by a CO{sub 2} laser pulse along the channel axis before the discharge is triggered. Resonant absorption of the laser, tuned to the {nu}{sub 2} vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. This paper describes the laser-gas interaction and the discharge initiation mechanism. We report on the channel stability and evolution, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a hydrocode simulation.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 837408
- Report Number(s):
- LBNL-54918; HIFAN 1320; TRN: US0501007
- Journal Information:
- Journal of Applied Physics, Vol. 91, Issue 2; Other Information: Submitted to Journal of Applied Physics: Volume 91, No.2; Journal Publication Date: 01/15/2002; PBD: 19 Apr 2004
- Country of Publication:
- United States
- Language:
- English
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