Characterization of millisecond-scale highpower impulse magnetron discharge in helium

Impulse magnetron discharges with millisecond-scale pulses—extended duration modes of technological high-power impulse magnetron sputtering (HiPIMS)—have promising applications in pulsed plasma facilities of different kinds due to high ionization degree (up to 90%), suitable duration, and scalable hardware design. Depending on operating conditions, at the same power level, two distinct diffuse regimes can be distinguished: the one with intense target sputtering— long HiPIMS (L-HiPIMS),—and the non-sputtering low-voltage one (non-sputtering magnetron discharge). The majority of existing studies of these discharge forms were made for argon working gas. For a number of prospective high-power pulsed plasma applications (e. g. pulsed plasma accelerators and thrusters), however, the option of using light gases is preferable. Here, the operation of a millisecond-scale impulse magnetron discharge (L-HiPIMS) in helium has been examined. The plasma parameters (electron density, electron temperature) were measured in a time-resolved fashion with a Langmuir probe. The electrical measurements were accompanied with optical emission spectroscopy. The use of the long pulsed modes enables achieving high plasma density and accelerating the ion flux with a peak energy of ~ 10 eV.