scholarly journals Dynamics of bipolar HiPIMS discharges by plasma potential probe measurements

Author(s):  
Michal Zanáška ◽  
Daniel Lundin ◽  
Nils Brenning ◽  
Hao Du ◽  
Pavel Dvorak ◽  
...  

Abstract The plasma potential at a typical substrate position is studied during the positive pulse of a bipolar high-power impulse magnetron sputtering (bipolar HiPIMS) discharge with a Cu target. The goal of the study is to identify suitable conditions for achieving ion acceleration independent on substrate grounding. We find that the time-evolution of the plasma potential during the positive pulse can be separated into several distinct phases, which are highly dependent on the discharge conditions. This includes exploring the influence of the working gas pressure (0.3 – 2 Pa), HiPIMS peak current (10 – 70 A corresponding to 0.5 – 3.5 A/cm2), HiPIMS pulse length (5 – 60 μs) and the amplitude of the positive voltage U+ applied during the positive pulse (0 – 150 V). At low enough pressure, high enough HiPIMS peak current and long enough HiPIMS pulse length, the plasma potential at a typical substrate position is seen to be close to 0 V for a certain time interval (denoted phase B) during the positive pulse. At the same time, spatial mapping of the plasma potential inside the magnetic trap region revealed an elevated value of the plasma potential during phase B. These two plasma potential characteristics are identified as suitable for achieving ion acceleration in the target region. Moreover, by investigating the target current and ion saturation current at the chamber walls, we describe a simple theory linking the value of the plasma potential profile to the ratio of the available target electron current and ion saturation current at the wall.

2020 ◽  
Vol 1492 (1) ◽  
pp. 012003
Author(s):  
M Dimitrova ◽  
M Tomes ◽  
Tsv Popov ◽  
R Dejarnac ◽  
J Stockel ◽  
...  

Abstract Langmuir probes are used to study the plasma parameters in the divertor during deuterium gas puff injection on the high- (HFS) or low-field sides (LFS). The probe data were processed to evaluate the plasma potential and the electron temperatures and densities. A difference was found in the plasma parameters depending on the gas puff location. In the case of a gas puff on the LFS, the plasma parameters changed vastly, mainly in the inner divertor – the plasma potential, the ion saturation-current density and the electron temperature dropped. After the gas puff, the electron temperature changed from 10-15 eV down to within the 5-9 eV range. As a result, the parallel heat-flux density decreased. At the same time, in the outer divertor the plasma parameters remained the same. We thus concluded that using a gas puff on the LFS will facilitate reaching a detachment regime by increasing the density of puffed neutrals. When the deuterium gas puff was on the HFS, the plasma parameters in the divertor region remained almost the same before and during the puff. The electron temperature decreased with just few eV as a result of the increased amount of gas in the vacuum chamber.


2021 ◽  
Vol 7 (2) ◽  
pp. 76-80
Author(s):  
L. N. Mishra ◽  
Å. Fredriksen

This article deals about the experimental measurement of plasma potential, ion saturation current and Mach number obtained with the variation of power, operating gas pressure and radial position using retarding field energy analyzer. We employed a retarding field energy analyzer by rotating with different angles such as 0° (facing toward source), 90° (facing side walls) and 180° (facing opposite the source). The coil current is varied from 0 to 15 A to produce the magnetic field which is used to confine the plasma. The flow of plasma has been characterized which was found to be subsonic. The low-temperature plasma is produced by means of a 13.56 MHz helicon plasma source at 300-1000 kW radio frequency power. The plasma is expanding from 13.8 cm diameter source into a 150 cm long diffusion chamber of 60 cm diameter.


2011 ◽  
Vol 18 (6) ◽  
pp. 063103 ◽  
Author(s):  
L. Yin ◽  
B. J. Albright ◽  
D. Jung ◽  
R. C. Shah ◽  
S. Palaniyappan ◽  
...  

2021 ◽  
Vol 03 (04) ◽  
pp. 23-34
Author(s):  
Ala F. AHMED

In this research, we have conducted an experimental study of the dusty plasma to the Aluminum oxide (Al2O3) dust material with a grain radius of (0.2) µm to (0.6) µm. In the experiment, we use air in the vacuum chamber system under different low pressure (0.1-0.8) Torr. The results have showed that the existence of dust particles in air plasma is equal to the Paschen minimum which is (0.4) Torr with Al2O3 dusty and without dust. The effect of Al2O3 dust particles on the plasma characteristics like floating potential (Vf), plasma potential (Vp), electron saturation current (Ies), temperature of the electron (Te), density of electron (ne) and density of ion (ni) of the DC system that can be calculated in the glow-discharge region. Parameter measurements are taken by four cylindrical probes which are diagnosed at a distance of (40) mm from the cathode diameter, the Paschen minimum at a pressure of (0.4) Torr. The plasma potential and the probe's floating voltage become more negative when dust is immersed in the plasma region. The features of these parameters show that the current discharge decreases while the discharge voltage increases when the aluminum oxide dust particles that are incorporated. And vice versa was in the absence of dust. Electron density increases in the existence of dust particles which causes the electron temperature to decrease.


2019 ◽  
Vol 59 (10) ◽  
pp. 106004 ◽  
Author(s):  
I.S. Abramov ◽  
E.D. Gospodchikov ◽  
R.A. Shaposhnikov ◽  
A.G. Shalashov

Open Physics ◽  
2005 ◽  
Vol 3 (4) ◽  
Author(s):  
Pavel Vrba ◽  
Miroslava Vrbová ◽  
Nadezhda Bobrova ◽  
Pavel Sasorov

AbstractWe performed computer modelling of a fast electrical discharge in a nitrogen-filled alumina capillary in order to discover discharge system parameters that may lead to efficient recombination pumping of soft X-ray laser with active medium created by H-like nitrogen ions. The space-time dependences of pinch plasma quantities were found by means of a one-dimensional MHD code. Time dependences of populations of all ionisation states and populations of selected energy levels of lithium-, helium- and hydrogen-like nitrogen ions were evaluated using the FLY code as a post-processor. The population inversion was found at the quantum transition corresponding to the Balmer α-line of N6+ ions and the resulting gain factor was evaluated for different capillary radii, initial pressure, electric current peaks and periods. A gain factor of 1 cm−1 spanning the time interval of 1 ns was found for an optimised arrangement with capillary radius 1.5 mm, peak current 50 kA, quarter period 40 ns and filling gas pressure 0.5 kPa. It is pointed out that even higher values of the gain factor may be achieved with thinner capillaries and shorter current pulses, e.g. a gain factor of 6 cm−1 is achieved if the capillary radius is 0.5 mm, peak current 56 kA, quarter period 15 ns, and filling nitrogen pressure 3.9 kPa.


The Landau equation can be derived as the sum of an expansion series in time provided certain non-Markovian short-time terms are neglected. The time series could be very useful for the solution of a variety of problems. It is necessary to estimate the time span over which the neglected term s are significant. The non-Markovian terms for the case of a homogeneous plasma are evaluated using a technique developed by Prigogine and Balescu. For typical values of plasma potential cut-offs the conditions under which the short-time terms may be ignored are estimated. It is found that for electrons of number density less than 1010 and protons of number density less than 1014 it may be possible to ignore the short-time effects. It is conjectured that for many situations the non-Markovian effects will be important for a time interval which has a lower bound t 0 and an upper bound several orders of magnitude greater than t .


2021 ◽  
Vol 03 (04) ◽  
pp. 17-22
Author(s):  
Hanaa Khudhaier Mohammed Ali AL-HAIDARY ◽  
A.F.Abed AL-KHADER

In this research, we have conducted an experimental study of the dusty plasma to the Aluminum oxide (Al2O3) dust material with a grain radius of (0.2) µm to (0.6) µm. In the experiment, we use air in the vacuum chamber system under different low pressure (0.1-0.8) Torr. The results have showed that the existence of dust particles in air plasma is equal to the Paschen minimum which is (0.4) Torr with Al2O3 dusty and without dust. The effect of Al2O3 dust particles on the plasma characteristics like floating potential (Vf), plasma potential (Vp), electron saturation current (Ies), temperature of the electron (Te), density of electron (ne) and density of ion (ni) of the DC system that can be calculated in the glow-discharge region. Parameter measurements are taken by four cylindrical probes which are diagnosed at a distance of (40) mm from the cathode diameter, the Paschen minimum at a pressure of (0.4) Torr. The plasma potential and the probe's floating voltage become more negative when dust is immersed in the plasma region. The features of these parameters show that the current discharge decreases while the discharge voltage increases when the aluminum oxide dust particles that are incorporated. And vice versa was in the absence of dust. Electron density increases in the existence of dust particles which causes the electron temperature to decrease.


2000 ◽  
Vol 6 (3) ◽  
pp. 206-212
Author(s):  
Vytautas Stauskis

The paper deals with the influence of the pulse length on the decay of the sound field energy. Six pulse lengths— 2000, 2500, 3000, 3500, 4000 and 4500 ms—were selected for investigations. Investigations show that a 2500 ms pulse is too short to correctly assess the background noise time interval. Such pulse length is not suitable for experiments. 3000 ms is the right length, while 3500 ms may be too long, resulting in errors of measurement results. When the pulse length increases to 4000 ms, the decay starting from 2000 ms is different from the pulse length 2500 ms and 3000 ms. Background noise starts from 2300 ms for these pulses, while for a 4000 ms pulse it starts from 3200 to 3300 ms. The length of 4500 ms is completely not suitable for investigations because the background noise zone starts very early, ie at 1800 ms, while for a short 2500 ms pulse it starts much later, after 2300 ms. While investigating energy decay, it is important to determine the maximum decay. At 63 Hz the sound field decay is almost uniform till— 18 dB. Later the decay character is different. The decay of the longest (4500 ms) and the shortest (2500 ms) pulse after— 18 dB is very steep and reaches—30 dB. However, the decay is influenced by the background noise. Thus the shortest and the longest pulses are not suitable for the lowest frequencies. The greatest energy decay is characteristic of the 3000 ms pulse. After 1700 ms energy decreases to—30 dB. Thus at this frequency one may measure the echoing time while approximating decay from 0 to—20 dB. As the frequency increases, the results change. At 100 Hz the energy decays by— 35–37 dB at pulse lengths of 2500 ms and 4000 ms. The greatest decay of— 42 dB is produced by the longest pulse 4500 ms though this arouses certain doubts. Then the echoing time may be measured from 0 to— 30 dB. At 125 octave frequency the smallest maximum decay of— 40 dB is observed with the shortest pulse (2500 ms), while the largest one— 50 dB is produced by the longest pulse (4500 ms). Thus standard echoing time may be measured for this frequency. In the frequency range of 250–2000 Hz, the maximum energy decay is sufficient and amounts to— 50–60 dB. At 4000 Hz the final part of decay is strongly dependent on the pulse length although, as the decay is about— 55 dB in all cases, the standard echoing time may be measured correctly. Pulse length is important only for the calculation of the low-frequency echoing time. At 63–100 Hz the best maximum decay is seen with the pulse 3000 ms long, while at 125 Hz and over the best pulse lengths are from 3000 to 4000 ms. When the hall contains audience and tapestries are on the walls, the energy decay is almost uniform at the pulse lengths of 2000 to 2800 ms. In this case a better decay is obtained with the longest pulse of 2800 ms.


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