Thermographic Investigation of the Effect of Plasma Exposure on the Surface ofa MAST Upgrade Divertor Tile in Magnum-PSI

Thermographic Investigation of the Effect of Plasma Exposure on the Surface ofa MAST Upgrade Divertor Tile in Magnum-PSI

Thermographic Investigation of the Effect of Plasma Exposure on the Surface ofa MAST Upgrade Divertor Tile in Magnum-PSI 150 150 amit lakhani
UKAEA-CCFE-CP(20)103

Thermographic Investigation of the Effect of Plasma Exposure on the Surface ofa MAST Upgrade Divertor Tile in Magnum-PSI

One of the issues faced by future fusion devices will be high target heat loads. Alternative divertors are a potential solution to the heat loads. They have been investigated in TCV and DIII-D, and will be investigated on MAST-U. To evaluate their effectiveness, accurate target heat flux and power balance measurements are required in these machines.Infrared (IR) thermography is a widely used technique to determine the target heat flux, but is susceptible to surface effects and emissivity in carbon-walled machines. In this work, the effect of plasma exposure on graphite is assessed to understand what may happen in MAST-U. A sample of MAST-U graphite is exposed to 30 minute plasma pulses,with n_e=6×10^18 m^−3 and T_e=0.08 eV as measured by Thomson scattering. During these pulses, the temperature is measured by a medium wave IR camera and is seen to decrease by ≈70◦C over the course of 3 hours of plasma exposure. Pyrometer measurements suggest that the IR camera is affected by a change in the surface emissivity.Profilometry confirms the erosion of the graphite at the tile centre to a depth of ≈100 nm, and regions of deposition further out, amounting to ≈40 nm of material.

Collection:
Conference
Journal:
Nuclear Materials and Energy
Publisher:
Elsevier
Conference:
24th International Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI), South Korea, 24 - 29 January 2021