Drifting localization of ionization runaway: Unraveling the nature of anomalous transport in high power impulse magnetron sputtering
The plasma over the magnetron’s erosion “racetrack” is not azimuthally uniform but concentrated in distinct dense plasma zones which move in the {vector E}×{vector B} direction with about 10% of the electrons’ {vector E}×{vector B}/B{sup 2} drift velocity. The plasma zones are investigated with a gated camera working in concert with a streak camera for Al, Nb, Cu, and W targets in Ar or Kr background gas. It is found that each plasma zone has a high density edge which is the origin of a plasma-generating electron jet leaving the target zone. Each region of strong azimuthal density gradient generates an azimuthal electric field which promotes the escape of magnetized electrons and the formation of electron jets and plasma flares. The phenomena are proposed to be caused by an ionization instability where each dense plasma zone exhibits a high stopping power for drifting high energy electrons, thereby enhancing itself.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- Accelerator& Fusion Research Division; Environmental Energy Technologies Division
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 1055807
- Report Number(s):
- LBNL-5293E
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics
- Country of Publication:
- United States
- Language:
- English
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