First Wall Particle Flux Measurements by an F82H Permeation Probe in QUEST

Abstract

First wall particle flux measurements in the QUEST spherical tokamak have been conducted, using a permeation probe that employs a first wall candidate ferritic steel alloy F82H as the membrane and also SUS304 as a comparative reference membrane. Permeation measurements have been done during the conditioning steadystate discharges heated with 2.45 GHz and 8.2 GHz ECR. Diffusion and recombination coefficients measured in a laboratory-scale plasma device: VEHICLE-1 are used to interpret the results from the permeation probe measurements in QUEST. These permeation membranes have been analyzed with XPS to evaluate the effects of surface impurities.

Hydrogen Permeation through Sputter-Deposited Tungsten Coated F82H in QUEST

“…The hydrogen plasma is produced by the 2.45 GHz ECR system with an input power of 7.5 kW and the toroidal filed coil current is kept at 17 kA. This condition is same with that of the previous work [2]. The steady-state permeation flux for the SP-W coated F82H membrane has been measured to be ∼2.1 × 10 13 H/cm 2 /s at 300 • C.…”

“…In this work, a sputterdeposited tungsten (SP-W) coated F82H permeation probe has been installed in QUEST. The data have been compared with experimental results obtained by a bare F82H permeation probe [2] and the effects of SP-W coatings on hydrogen PDP are discussed.Experiments are performed in the medium sized spherical tokamak QUEST [4] with the major and minor radii of 0.68 m and 0.4 m, respectively. Schematic view of the tokamak cross-section is shown in Fig.…”

“…In this work, a sputterdeposited tungsten (SP-W) coated F82H permeation probe has been installed in QUEST. The data have been compared with experimental results obtained by a bare F82H permeation probe [2] and the effects of SP-W coatings on hydrogen PDP are discussed.…”

“…Thus, it is crucial to measure the particle flux to the first wall. In our previous work [2], a permeation probe made of a reduced activation ferritic steel (RAFS) F82H was used to measure the hydrogen permeation flux in QUEST at Kyushu University. Those measurements were conducted during wall conditioning steady-state discharges.…”

“…In our previous work [2], the steady-state permeation flux was measured to be ∼2.4 × 10 13 H/cm 2 /s at 270 • C using a 0.2 mm thick bare F82H membrane. Notice, however, that there was no radiation shield during that QUEST campaign.…”