Comparison of thermal properties of a hot target magnetron operated in DC and long HIPIMS modes

Abstract

Thermal properties of the magnetron discharge with uncooled copper and chromium targets were studied experimentally and theoretically for DC and long HiPIMS (L-HiPIMS) operation modes. A set of thermal fluxes was considered to build a numerical model of the hot target exposed to DC and high-power pulsed plasma. The modeling results were tested in the experiments. The temperature of targets was measured directly in course of magnetron discharge operation with an elaborated contact thermocouple method. The measurements were made in two modes. At first the temporal evolution of temperature was recorded for a fixed applied discharge power. The results were found to well agree with temperature values expected from calculations. At 2 kW power, it takes ~50 s to reach the melting point of copper. The steady-state temperature values were also measured for a number of discharge power levels. The obtained dependence clearly demonstrated that the main mechanisms of the target heat balance at high temperatures are surface radiation and heat transfer due to thermal conductivity of the heat insulation supports between the target and water-cooled cathode. The parameters of DC hot target magnetron were compared to the high-power pulsed regime with the pulse-on time 20 ms. A promising method of a hot target magnetron discharge operation was considered that involves applying long (>20 ms) high-power pulses to the target pre-heated in the DC mode during the pulse-off period.