The data acquisition and control system for the operation of ASDEX pressure gauge for the measurement of neutral pressure in ADITYA Tokamak

Abstract

Bayard-Alpert (BA) type hot cathode ionisation gauge is widely used to measure neutral pressure precisely in vacuum system below 10−3 Torr pressure. Neutral pressure measurement in magnetic confinement fusion experiments is quite challenging for standard BA type gauge due to higher pressure limitation and its ionisation is affected by strong magnetic and electrical fields. To overcome the above limitations, a special hot cathode ionisation gauge, named ASDEX Pressure Gauge (APG) system was developed by G. Haas at the Max-Planck-Institute, Germany. The APG system can work in high magnetic field up to 6 T and high temperature plasma environment with broad pressure measurement range from 10−1 to 10−6 mbar with fast response (<10 msec) and good noise immunity.In the present work, we report the design and development of control and data acquisition of ASDEX Pressure Gauge (APG) for ADITYA Tokamak to measure real time neutral pressure during the high temperature plasma. The developed system can achieve synchronous control of gauge controller using General Purpose Interface Bus (GPIB) and data acquisition of ion emission current of gauge head using Peripheral Component Interconnect (PCI) based data acquisition module. Initially, the APG calibration with standard BA type hot cathode ionization gauge had been carried out using the test set-up of low magnetic field and ultrahigh vacuum system with gases like H2, Ar, He. For APG calibration for various pressure ranges of these gases, precise gas feed control system has been developed using controller based hardware and LabVIEW based software. After testing and calibration, the APG was installed on ADITYA tokamak and calibrated under high magnetic field of ADITYA. The developed APG control system is configurable for presenting the gauge parameters before the plasma discharge. During plasma discharge, the analog signal equivalent to neutral pressure is acquired in real-time using simultaneous sampling analog to digital converter (ADC) module. The acquired raw data and processed real time pressure can provide valuable neutral pressure/density information of Tokamak plasma.