Observation of increase in ion temperature estimated from neutron rate on dropping Boron powder in WEST L-mode plasmas.*

The effect of dropping boron powder on LHCD-heated L-mode WEST plasmas was studied. The drop rates were increased from 0 mg/s to 53 mg/s in multiple steps. The ion temperature estimated from the neutron rate showed a 55% increase from 1.1 keV to 1.7 keV on dropping boron. The increase in ion temperature was found to be accompanied by a reduction in density scale length. This reduction in density scale length may reduce the growth rate of ion temperature gradient-driven instability and the associated thermal transport. Furthermore, upon adding boron, a reduction in D-alpha signal near the divertor was observed, suggesting a reduction in deuterium recycling. The line-integrated interferometer chord near the separatrix indicates a reduction in density after adding boron. The plasma internal inductance was also observed to increase with increased boron. The trends in the data are being analyzed to understand the cause of the increase in ion temperature. The results of the experiment and these analyses will be presented.