On the measurement of energy fluxes in plasmas using a calorimetric probe and a thermopile sensor

Abstract

Two different diagnostics for the determination of the energy influx in plasma processes were used to characterize an ion beam source and an asymmetric RF discharge. The related energy fluxes were measured in dependence on the ion energy and on the RF power, respectively. The first sensor, called HFM (Heat Flux Microsensor) is a thermopile which allows for direct energy flux measurements. With the second sensor, a calorimetric probe, the energy influx has been calculated from the temporal temperature evolution preliminarily registered. Although the working principle of both sensors is different, the obtained results are in good agreement. In the ion beam (<1.5 keV)) rather high energy influxes are achieved (up to 700 mW cm −2 ), whereas the values measured in the asymmetric RF discharge were lower than 50 mW cm −2 for discharge powers in the range 10–100 W. The performances and limitations of both sensors are compared and discussed.