| 1. |
- Brenning, Nils, et al.
(författare)
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Radiation from an electron beam in a magnetized plasma : Whistler mode wave packets
- 2006
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 111:A11
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Tidskriftsartikel (refereegranskat)abstract
- Experimental studies are reported of oscillations and radiation that is spontaneously excited by an electron beam which is shot along a diverging magnetic field into a plasma from a hot cathode. In the present study we focus on oscillations below the electron gyrofrequency, where we find that whistler mode radiation appears in the form of bursts, or wave packets, each with typically 0.1-1 mu s time duration, and which together cover typically a few percent of the full time. Wave packets are found in a broad frequency range of 7-40 MHz, while each individual wave packet is dominated by a single frequency. There is propagation along two routes: at the group velocity resonance cone angle, away from the central channel where the waves are excited, and in a channel along the magnetic field. Features of the whistler mode wave packets that are studied include (1) the statistics of amplitudes, frequencies, and time durations; (2) the propagation and decay of wave packets with different frequencies; (3) the group and phase velocities; and (4) how the wave packet production varies with the energy, and the current density, in the electron beam.
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| 2. |
- Böhlmark, Johan, et al.
(författare)
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The ion energy distributions and ion flux composition from a high power impulse magnetron sputtering discharge
- 2006
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:4, s. 1522-1526
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Tidskriftsartikel (refereegranskat)abstract
- The energy distribution of sputtered and ionized metal atoms as well as ions from the sputtering gas is reported for a high power impulse magnetron sputtering (HIPIMS) discharge. High power pulses were applied to a conventional planar circular magnetron Ti target. The peak power on the target surface was 1-2 kW/cm(2) with a duty factor of about 0.5%. Time resolved, and time averaged ion energy distributions were recorded with an energy resolving quadrupole mass spectrometer. The ion energy distributions recorded for the HIPIMS discharge are broader with maximum detected energy of 100 eV and contain a larger fraction of highly energetic ions (about 50% with E-i > 20 eV) as compared to a conventional direct current magnetron sputtering discharge. The composition of the ion flux was also determined, and reveals a high metal fraction. During the most intense moment of the discharge, the ionic flux consisted of approximately 50% Ti1+, 24% Ti2+, 23% Ar1+, and 3% Ar2+ ions.
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