Speaker
Description
The WEST tokamak (Tungsten (W) Environment in Steady state Tokamak) aims at testing ITER-like divertor plasma-facing units (PFU) in an integrated tokamak environment, and performing long pulse operation with high fluence. To operate long plasma discharges with power loads in the range of those expected in ITER (10-20 MW.m-2) on the Plasma Facing Components (PFC), infrared (IR) thermography are key diagnostics, enabling real-time monitoring of PFC surface temperature for safe operation, while providing essential data for various physics studies.
The infrared thermography system at WEST (ref. 1) consists of a set of three different diagnostics: 1) 7 endoscopes located in upper ports devoted to machine protection, providing a full coverage of the lower divertor and of the 5 antennas of the auxiliary heating systems; 2) a wide-angle view of the vacuum vessel observes tangentially one sixth of the vacuum vessel, and in particular upper port protections, upper divertor targets, bottom baffle, and inner guard limiter; 3) a very high-resolution view (100µm pixel size) of the lower divertor to study finely the thermal behavior of the ITER like PFUs installed in WEST.
During the WEST C4 campaign (July to Nov. 2019, about 1200 pulses with a duration > 2s), IR thermography diagnostics produced about 10 To of data, which are now easily accessible from the WEST database with the versatile software ThermaVIP, and thus available for further physics analyses. As a part of the Wall Monitoring System (WMS), the stream of IR data was also routinely used during C4 campaign with a real time processing for PFC temperature monitoring, through the plasma control system (PCS) that reduces the power of the heating device (antenna) responsible for a temperature increase (ref. 2). For about 14% of the pulses, the IR monitoring led to a thorough reduction of the heating devices injected power, and thereby helped to protect the PFCs and ensure a safe operation, while allowing plasma discharges continuation.
The correspondence between a region of interest (ROI) monitored by an infrared diagnostic and a heating device is given by the knowledge of the heating phenomena observed in WEST and acquired with Tore Supra since the 90s and along the firsts WEST experimental campaigns. For each couple ROI/heating device, two temperatures are defined: the first one (T1) is the maximal acceptable working temperature for the component (as stipulated in the WEST operation instructions) before triggering a plasma soft stop, the second one (T2
| Affiliation | CEA, IRFM |
|---|---|
| Country or International Organization | France |
