Developing and Constructing a Piezoelectric Drive Amplifier (PDA) for Calibrating Ball Pen Pins of the Mix Probe Diagnostic to Measure Plasma Potential in the IR-T1 Tokamak

In this work, a Piezoelectric Drive Amplifier (PDA) was designed and constructed for the first time to calibrate Ball Pen Probe (BPP) pins of Mix Probe in order to measure plasma potential in IR-T1 tokamak. The PDA amplifies a triangular wave generated by a signal generator with ±10 V and 1 kHz frequency to ±100 V, 1 kHz frequency and a maximum current 100 mA to sweep the collector of BPP of the mix probe. Current–voltage characteristic of BPP was plotted for a 10 ms plasma duration at Last Closed Flux Surface (LCFS) while the collector was swept between ±100 V by the PDA. The Ball Pen coefficient ( $${{{{\alpha }}}_{{{\text{BPP}}}}}$$ ) was also calculated to be approximately 0.5. The time trace of plasma potential and electron temperature was additionally derived from the floating potential, which was assessed using both the BPP and Langmuir pins. The floating potential measured by the BPP is much more closely aligned with the plasma potential than the floating potential measured by the LP. Consequently, we can regard the floating potential measured by the BPP as the plasma potential.