On three projects in low temperature plasma discharge physics

An overview will be given on discharge physics. Weakly ionized plasma discharges are driven electrically by voltage or current sources. These discharges have boundaries at which surface losses are important and    ionization of neutrals sustains the plasma in steady state. Furthermore, charged particle collisions with neutral gas atoms and molecules are important and electrons are not in thermal equilibrium with the ions. We will discuss three such discharges that are often applied in materials processing in various industries. These are the capacitive discharge, the inductive discharge and the magnetron sputtering discharge. Three active research projects will then be discussed. First is particle-in-cell Monte Carlo collision simulation on capacitive argon, chlorine and Ar/Cl2 discharge. We demonstrate how the electron power absorption in the discharge transition from pressure heating, to drift ambipolar and to drift ambipolar - striation mode as chlorine fraction in the feedstock is increased [1]. Then we discuss magnetron sputtering in particular high power impulse magnetron sputtering [2], a method used to deposit thin films and coatings. We discuss ionized physical vapor deposition (iPVD), the drop in deposition rate as the ionized flux fraction of the film-forming material is increased and how it depends on the sputter yield of the target material [3]. Finally we discuss the use of a three meter long inductive discharge in the cylindrical configuration for laboratory astrophysics. In the FIREBALL experimental campaigns at CERNs HiRadMat facility an electron-positron pair beam [4] is delivered through a plasma discharge with the goal of observing beam-plasma instabilities. This discharge enables studies of beam--plasma interactions over propagation lengths of several tens of centimeters, which are required for the development of the targeted instabilities [5].    [1] B. Mahdavipour and J. T. Gudmundsson, Particle in cell Monte Carlo collision simulations of capacitive Ar/Cl$_2$ discharges: Pressure and voltage dependence, Journal of Vacuum Science and Technology A, 44(5) (2026) 053007 https://doi.org/10.1116/6.0005635    [2] J. T. Gudmundsson, Physics and technology of magnetron sputtering discharges, Plasma Sources Science and Technology, 29(11) (2020) 113001 https://iopscience.iop.org/article/10.1088/1361-6595/abb7bd    [3] Kateryna Barynova, Nils Brenning, Swetha Suresh Babu, Joel Fischer, Daniel Lundin, Michael A. Raadu, Jon Tomas Gudmundsson and Martin Rudolph, Self-regulating electron temperature in high-power impulse magnetron sputtering discharges and its effect on the metal ion escape, Plasma Sources Science and Technology, 34(6) (2025) 06LT01 http://dx.doi.org/10.1088/1361-6595/adde82    [4] C. D. Arrowsmith, P. Simon, P. Bilbao, A. F. A. Bott, S. Burger, H. Chen, F. D. Cruz, T. Davenne, I. Efthymiopoulos, D. H. Froula, A. M. Goillot, J. T. Gudmundsson, D. Haberberger, J. Halliday, T. Hodge, B. T. Huffman, S. Iaquinta, F. Miniati, B. Reville, S. Sarkar, A. A. Schekochihin, L. O. Silva, R. Simpson, V. Stergiou, R. M. G. M. Trines, T. Vieu, N. Charitonidis, R. Bingham, and G. Gregori, Laboratory realization of relativistic pair-plasma beams, Nature Communications 15 (2024) 5029 https://doi.org/10.1038/s41467-024-49346-2    [5] C. D. Arrowsmith, F. Miniati, P. J. Bilbao, P. Simon, A. F. A. Bott, S. Burger, H. Chen, F. D. Cruz, T. Davenne, A. Dyson, I. Efthymiopoulos, D. H. Froula, A. Goillot, J. T. Gudmundsson, D. Haberberger, J. W. D. Halliday, T. Hodge, B. T. Huffman, S. Iaquinta, G. Marshall, B. Reville, S. Sarkar, A. A. Schekochihin, L. O. Silva, R. Simpson, V. Stergiou, R. M. G. M. Trines, T. Vieu, N. Charitonidis, R. Bingham, and G. Gregori, Suppression of pair beam instabilities in a laboratory analogue of blazar pair cascades, Proceedings of the National Academy of Sciences, 122 (45) (2025) e251336