Divertor ion temperature measurements on MAST by retarding field energy analyser
ORAL
Abstract
The ion temperature (T$_{i}$) at the divertor determines the heat flux and erosion due to plasma surface interactions. However, there are few measurements of T$_{i}$ at the divertor compared to the electron temperature (T$_{e}$) due to the relative complexity of the measurement. Divertor T$_{i}$ measurements have been made using a retarding field energy analyser at the lower outer divertor of MAST in L-mode, inter-ELM H-mode and during ELMs. These measurements are compared to the T$_{e}$ from Langmuir probes and the heat flux from IR thermography. The sweeping of the strike point means that T$_{i}$ profiles can be produced. In a range of L-mode discharges with I$_{P}$ = 400 \--- 900 kA, T$_{i}$ $\sim$ T$_{e}$, with T$_{i}$ = 3 \--- 15 eV, however in inter-ELM H-mode T$_{i}$/T$_{e}$ can be up to 3. In inter-ELM H-mode a dependence of T$_{i}$/T$_{e}$ on collisionality has been seen. First measurements of T$_{i}$ at the target during ELMs will be presented either measuring the ELM averaged ion temperature using a slow sweep of the discriminator voltage or using a fast (50$\mu$s) sweeping mode. The effect of parallel Mach flows on T$_{i}$ measured at the divertor will be considered for the discharges presented in this work.
*Work supported by the RCUK Energy Programme and EURATOM.
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