Plasma dynamics of individual HiPIMS pulses: imaging study using high-frame-rate camera

R1 Cathode voltage and discharge current of ten successive pulses for discharges operated in Ip = 50-400 A and p = 0.25-2.0 Pa range. The waveforms for Ip = 100-300 A and p = 0.25-0.5 Pa range demonstrate unstable discharge conditions with current alternating between high- and low-current regimes. Note that at 100 A, high-current regime waveforms are clipped because of the current range set on the oscilloscope. Also, some pulses are shorter than 150 µs due to the arc formation. R2 Compilation of videos for pulses 1 to 4 operated in Ip = 10-50 A and p = 0.25-2.0 Pa range. The videos demonstrates the reproducibility of plasma evolution for individual pulses with similar current waveforms. R3 Compilation of videos for pulses 1 to 4 operated Ip = 50-400 A and p = 0.25-2.0 Pa range. The videos demonstrate the reproducibility of plasma evolution. Nevertheless, more differences in the spoke evolution can be observed than in lower-current experiments shown in R2. R4 Front-view videos of plasma evolution for Ip = 50 A at 100 Hz and 500 Hz. The videos were compiled from videos in V3a and V4a. R5 The cathode voltage and discharge current waveforms corresponding to video R4. V1 Cathode voltage and discharge current of individual HiPIMS pulses for Ip = 10-50 A and p = 0.25-2.0 Pa range. The pulse on-time was 150 µs and the repetition frequency 500 Hz. Seven sequential are shown pulses for each condition. Plasma dynamics for these waveforms are shown in video V3. V2 Cathode voltage and discharge current of individual HiPIMS pulses for Ip = 50-400 A and p = 0.25-2.0 Pa range. The pulse on-time was 150 µs and the repetition frequency 100 Hz. Seven pulses with similar current waveforms are shown for each condition. Plasma dynamics for these waveforms are shown in video V4. V3a Front-view videos of plasma dynamics for seven individual HiPIMS pulses operated in Ip = 10-50 A and p = 0.25-2.0 Pa range presented in a high-contrast "royal" color map. The number in the top left corner of each frame shows the discharge current (in Ampere) at which the image was recorded. Seven sequential pulses are shown for each condition. The intensity of each frame was normalized between the lowest and the maximum brightness. The corresponding cathode voltage and discharge current waveforms can be found in V1. V3b The same as V3a video but presented in a lower-contrast "viridis" color map showing finer details. The light intensity of frames was normalized between the lowest light intensity and the maximum light intensity of the frame with the highest light intensity in the pulse. V4a Front-view videos of plasma dynamics for seven individual HiPIMS pulses operated in Ip = 50-400 A and p = 0.25-2.0 Pa range presented in a high-contrast "royal" color map. Seven selected pulses are shown for each discharge condition. The corresponding cathode voltage and discharge current waveforms can be found in V2. V4b The same as video V4a video but presented in a lower-contrast "viridis" color map. V5 Side-view plasma images recorded for individual HiPIMS pulses operated at Ip = 10-50 A and p = 0.25-2.0 Pa range. The images show plasma distribution at different times during the pulse in 25 µs steps from the pulse onset. The corresponding cathode voltage and discharge current waveforms can be found in V7 (pulse 1). V6 Side-view plasma images recorded for currents between 5 A and 40 A for Ip = 10-50 A and p = 0.25-2.0 Pa range selected from the video V8a (pulse 1). V7 Cathode voltage and discharge current of individual HiPIMS pulses for Ip = 10-50 A and p = 0.25-2.0 Pa range. The waveforms correspond to the videos of individual pulses shown in V8. V8a Side-view videos of plasma dynamics for seven individual HiPIMS pulses operated in Ip = 10-50 A and p = 0.25-2.0 Pa range. Videos are presented in a high-contrast "royal" color map with the same image processing as in video V3a. The corresponding cathode voltage and discharge current waveforms can be found in V7. V8b The same as video V8a video but presented in a lower-contrast "viridis" color map with the same processing as in video V3b. V9 Side-view plasma images recorded for individual HiPIMS pulses operated at Ip = 50-400 A and p = 0.25-2.0 Pa range. The images show plasma distribution at different times during the pulse in 25 µs steps from the pulse onset. The corresponding cathode voltage and discharge current waveforms can be found in V11 (pulse 1). V10 Side-view plasma images recorded for currents between 25 A and 250 A for Ip = 50-400 A and p = 0.25-2.0 Pa range selected from the video V12 (pulse 1). V11 Cathode voltage and discharge current of seven individual HiPIMS pulses for Ip = 50-400 A and p = 0.25-2.0 Pa range. The waveforms correspond to videos of individual pulses shown in V12. V12a Side-view videos of plasma dynamics for seven individual HiPIMS pulses operated in Ip = 50-400 A and p = 0.25-2.0 Pa range. The intensity of each frame was normalized between the lowest and the maximum brightness. The images are presented in a high-contrast "royal" color map. The corresponding cathode voltage and discharge current waveforms can be found in V11. V12b The same as video V12a video but presented in a lower-contrast "viridis" color map with the same processing as in video V3b. V13 Velocity of spokes as a function of discharge current for Ip = 10-50 A and p = 0.25-2.0 Pa range. Symbols represent different number of spokes and direction of rotation. V14 Velocity of spokes as a function of discharge current for Ip = 50-400 A and p = 0.25-2.0 Pa range. Symbols represent different number of spokes and direction of rotation. V15 Characteristic stages in the HiPIMS discharge for operated in p = 0.5-2 Pa range and Ip = 40 A. For more detailed description, refer to the text in the paper. V16 Characteristic stages in the HiPIMS discharge for operated in p = 0.25-1 Pa range and Ip = 400 A. In stage III, several sub-stages (labeled IIIa, IIIb, IIIab and IIIc) can be recognized based on the different current growth rates and typical spoke patterns. For more detailed description, refer to the text in the paper.