Application of the Ball-Pen Probe in Two Low-Temperature Mag-netised Plasma Devices and in Torsatron TJ-K

The ball-pen probe is an innovative electric probe for direct measurements of plasma potential in magnetised hot plasma. This probe is based on the Katsumata probe concept. The ball-pen probe can adjust the ratio I^-_sat I⁺_sat of the electron and ion saturation currents to be equal to one causing the ball-pen probe characteristics to become symmetric. If this is achieved, the floating potential of the ball-pen probe is equal to the plasma potential. We show the application of a ball-pen probe in two low-temperature magnetised plasma devices and in torsatron TJ-K