Experimental setup showing the arrangement and basic circuitry of the magnetron and probe diagnostics.
Measured magnetic field and field line directions for the magnetron used; top: |B| on a axial line above the racetrack at r = 24 mm, and right: |B| in radial direction at z = 1 mm.
Waveforms for the probe’s heating voltage pulse, , with the associated filament heating current, , the emitted electron current, , and the gate pulse, , for one HiPIMS pulse.
Floating potential as a function of the heating current, at the probe positions (r = 28 mm, z = 20 mm) and (r = 28 mm, z = 40 mm). The floating potential approaches to the plasma potential when the heating current exceeds about 2.1 A.
Plasma and floating potential waveforms, averaged over 100 pulses, measured at the probe position (r = 24 mm, z = 22 mm). Additionally, the discharge current waveform is shown or an applied voltage of 488 V, pulse width 100 μs, at a repetition rate of 100 Hz leading to peak current 170 A. The shaded areas around the averaged pulse shapes represent the envelopes containing data of all 100 pulses.
Nonaveraged plasma potentials measured at (r = 20 mm, z = 15 mm). The black curve is one example showing relatively large amplitude oscillations corresponding to frequencies in the range 20–100 kHz; the thin-line curves (red in the on-line version) are overlaid to illustrate the construction of the gray envelopes shown in Fig. 5 ; the central (blue in the on-line version) curve is the arithmetic mean of 100 pulses.
(a) and (b). Distribution of plasma potential (left column) and derived electric field (right column) at different times during a HiPIMS pulse. Each data point is the mean of 100 individual measurements. (b) is a continuation of (a) (enhanced online). [URL: http://dx.doi.org/10.1063/1.3700242.1]doi: 10.1063/1.3700242.1.
Floating potential distributions for selected times during a HiPIMS pulse.
Distribution of the electron velocities, where B is the static field originating from the permanent magnetics and the E field is derived from the measured plasma potential averaged over 100 pulses. In this sense, the velocity distributions displayed are smoothed and the actual and instantaneous drift velocities deviate from this average. The subfigures correspond to the beginning, middle and end of HiPIMS pulses. Positive values for the velocity imply a velocity vector direction into the plane.
Plasma potential distribution 4 μs after current onset ( ) as recorded using a hot probe whose emission current is not sufficiently high everywhere; this results in a valley region where the probe’s floating potential indicates a cold probe’s potential rather than the hot probe potential (cf. Fig. 4 ).
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