Role of anti-pole aligned hybrid multi-cusp magnetic field strength on hydrogen plasma ignition and confinement using radio-frequency powered hollow cathode discharge

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This study investigates the critical influence of anti-pole aligned hybrid multi-cusp magnetic field (HMCMF) strength in optimizing hydrogen plasma ignition and confinement within a radio frequency (RF)-powered hollow cathode discharge system. Three configurations were systematically evaluated: a non-magnetic baseline (config. W), a moderate-strength HMCMF (config. X: 5 mm inner-ring magnets), and a reinforced HMCMF (config. Y: 10 mm inner-ring magnets), operating at hydrogen pressures of 0.7–3 Pa and a fixed RF (13.56 MHz) power of 50 W. Advanced Langmuir probe diagnostics demonstrated that HMCMF configurations (X and Y) significantly lowered the threshold ignition conditions to 0.04 Pa and 264 V (p-p), compared to 0.1 Pa and 272 V (p-p) for config. W. Config. Y achieved a peak plasma density of 5.47×1016 m−3 in the central groove, marking 57% and 42% enhancements over configs. W and X, respectively. Spatial analysis demonstrated superior confinement uniformity, with config. Y, exhibiting the highest plasma uniformity factor (PUF = 3.03) and minimal sheath expansion under sub-Pascal pressures. These findings underscore the efficacy of reinforced HMCMF topologies in enhancing low-pressure plasma density, stability, and energy efficiency, offering transformative potential for applications in semiconductor etching, thin-film deposition, and fusion-relevant ion sources.