Overview of the different processes of tungsten coating implemented into WEST tokamak

Abstract

The Tore Supra tokamak is being transformed in an x-point divertor fusion device within the frame of the WEST (W-for tungsten-Environment in Steady-state Tokamak) project, launched in support to the ITER tungsten divertor strategy. The WEST project aims at testing W monoblock Plasma Facing Units (PFU) under long plasma discharge, with thermal loads of the same magnitude as those expected for ITER. The others Plasma Facing Components (PFC) will also be modified and coated with W to transform Tore Supra into a fully metallic environment. Different coating techniques have been selected, taking into account the specifications of the various PFC: heat loads, complex geometries (length up to 1m) and different substrates (CuCrZr for actively cooled PFC, graphite and CFC for other components). This paper gives an overview on the different processes used and the associated validation program and concludes on the adequacy of the W coating with the WEST experimental program requirements.

Emissivity measurement of tungsten plasma facing components of the WEST tokamak

“…The W-coated graphite sample was sliced from a W-coated graphite divertor PFC (graphite grade R 6710) which was tested in a HHF experiment (20 cycles of 8 MWm² for 2 s). The coating thickness is about 12 µm [26,27] with Ra = 2 µm. The two other samples (damage #1 and #2) have been provided by the same manufacturer as the W bulk sample.…”

“…In addition, all along plasma operations, the surface roughness of more or less all the PFCs will be modified through plasma surface interaction leading to erosion, deposition and possible damages (local melting…). In this context, a dedicated setup has been developed at CEA/IRFM to measure the emissivity of W samples coming from actively cooled bulk W components (also called ITER-like PFU [4]) and W-coated graphite component of the WEST divertor used in the early phase experiment [26,27]. The principle of the measurement and the experimental setup are depicted in section 2.…”

WEST actively cooled load resilient ion cyclotron resonance heating system results

“…Lateral limiters are located on both sides of each antenna and protrude by 2 cm from the edges of the Faraday Screen. These limiters are the ones used on Tore Supra and are made of CFC tiles coated with a double coating made of a first 80 µm molybdenum layer followed by an 80 µm tungsten (W) coating [11,12]. While having high Z materials close to an ICRH antenna was known to increase the tungsten sputtering attributed to the acceleration of light impurity ions in the rectified RF sheaths [13], this choice was motivated by the desire to keep a full W, reactor relevant machine [14].…”

Design and manufacturing of bulk tungsten tiles for WEST outer limiter

“…The main objective of the WEST project is to manufacture and test an ITER-like actively cooled tungsten divertor, and provide a full tungsten tokamak environment [1]. Besides the ITER-like actively cooled plasma facing units to be tested at WEST lower divertor, other WEST Plasma Facing Components (PFCs) were designed, manufactured and qualified [2][3][4]. The present paper focuses on the outer bumper limiter, a plasmafacing component aiming at protecting the RF antennae during the ramp-up and ramp-down normal phases, but also from transient energetic event like disruption and runaway beam.…”