WEST plasma control system status

Abstract

This paper presents the current status of the WEST Plasma Control System (PCS). From the first campaign at the end of 2016 to the latest campaign at the end of 2022, significant upgrades have been deployed to improve several aspects of the machine performance. The vertical instability control loop has been upgraded in order to increase the operation domain (i.e. plasma elongation). This upgrade optimizes the delay at each stage of the control loop using raw magnetic data coupled to a real-time vertical displacement observer. This allows for different shape control modes that address various operation issues such as X-point formation and gap control. The control of the plasma density uses generic feedforward and/or feedback controllers to control the 21 piezo-electric valves of the gas injection system and/or the pellet injection system. The heating systems of WEST (ICRH and LHCD) are also driven by the PCS, which has the ability to control both the power and the phase of the antennas. More recently, feedback control of the loop voltage using the LHCD power has been fully implemented in order to perform plasma discharges of up to 1000 s. Also in the most recent campaigns, the entirety of the lower divertor has been actively cooled. Operating a fully actively cooled metallic machine requires real-time machine protection strategies to avoid water-leaks or other damage to the first wall. On WEST, such protections are based on spectroscopic density measurements of impurities and on the infrared monitoring of critical components. These strategies trigger either minor adjustments of the reference scenario (e.g. decreasing of the requested heating power) or a soft plasma termination.