Automated plasma probing system for laboratory experiments in high vacuum using closed loop control

Abstract

The Inverse Mirror Experimental Plasma Device (IMPED) is constructed to study the behaviour of magnetized plasmas in both collisional and collision-less regimes. The device has multiple active probe diagnostics to investigate turbulence, flow dynamics, instabilities, and wave interactions. In the paper, we report the development of feedback-controlled, very accurate (±0.2 mm accuracy of positioning) probe drive system, that achieves its performance utilizing inexpensive major components including motor, drive controller, and digital scale, which is used for position verification. This could make it economically feasible for even the small-scale experiment to use a large number of such drives. This facilitates the studies, where high temporal and spatial resolution are required for simultaneous measurements made at widely separated axial and/or azimuthal locations. Precise positioning is achieved by properly tuned Proportional–Integral–Derivative (PID) control. PC-based automation of the probe drive is validated for vacuum integrity by a pressure gauge and length measurement by digital scale. The software is developed on LabVIEW for integration with the Data Acquisition System (DAQ) and Python for its application in other experiments. The system has achieved ±0.2 mm accuracy in a linear scan of 0 to 80 mm, under the vacuum of 10−6 mBar and background magnetic field of 120 mT.