PIC/MC calculation of current–voltage characteristic of emissive probe

Two numerical models were used to study the function of an emissive (electron-emitting) probe—the PIC/MC model and the thermal model. The PIC/MC model was used to calculate the I – V characteristics of the emissive probe. The calculations were focussed on the determination of the floating potential of the probe, which increases with increasing probe temperature. It was found that the floating potential can reach the value of the plasma potential, and it can even be higher than the plasma potential. The dependence of the floating potential on probe temperature is linear in the vicinity of the plasma potential, and the slope of this dependence changes when the floating potential equals the plasma potential. The potential profiles near the probe were also calculated and it was found that the space charge effects can be neglected for the plasma parameters studied (electron density 10 14 –10 16 m −3 , electron temperature 2500–40 000 K, probe temperature up to 2500 K). The thermal model was used for the calculation of the dependence of probe temperature and potential profiles on DC current passing through the probe (and heating the probe). The thermal model was based on the heat equation, which was solved using the finite element method. Finally, the results from both the above-mentioned models were combined to obtain the dependencies of floating potential on probe heating DC current.