A real-time density feedback control system with a 100 GHz
heterodyne interferometer has been designed, developed, and
commissioned in ADITYA-U tokamak. It consists of three subsystems
i.e. density measurement, feedback control, and gas fuelling. A
proportional feedback controller is configured in voltage amplitude
mode to operate the piezo valve for gas injection. Experiments are
performed during plasma discharges to achieve a predefined density
evolution as well as constant density. Stickiness of the piezo
valve restricts the temporal response of the valve. It is required
to minimize during the plasma discharge for a fast density response
which is achieved by a short preceding voltage pulse known as a
stick pulse. This paper describes the implementation of a real-time
density feedback control system which is successfully validated
using another existing 140 GHz interferometer system in ADITYA-U.
Moreover, the developed system consumes low power, is cost-effective
and re-programmable, can be easily upgraded, and provides interlock
with plasma parameters.