Speaker
Description
ITER reference design, inductively coupled single driver RF-source ROBIN is operational at
IPR, Gandhinagar. The first phase of the operation yielded H- ion current density of 22-25
mA/cm2 and with electron to-ion ratios >1. The Cesium (Cs) consumption was very high
compared to a similar source operated at IPP, Garching. The lessons learned from the
operational experience showed the operational limitations in presence of impurities and
excessive evaporation of Cs into the source. Since then the source was disassembled,
cleaned, and reassembled to enable the restart of operations under improved and
controlled conditions. Recent experiments assisted by relevant diagnosis on the cleaned
ROBIN source under controlled cesiated conditions and improvements based on the lessons
learned have resulted in achieving H- ion current densities >30 mA/cm2 and electron to ion
ratios < 1 and with Cs consumption reduced to ~12 mg/hr. Systematic studies related to
parametric dependence on the source filling pressure and power have been performed with
powers up to 80 kW coupled to the source at an RF frequency of 937 kHz. The role of plasma
grid bias on the H- ion current densities, electron to ion ratios, beam transmission, plasma,
and negative ion densities, and electron temperatures have been studied in detail. The
observations and results related to Cs conditioning, source performance optimization,
source parametric dependence on the beam, and related observations and findings related
to the effects of the bias voltage on the source performance shall be presented and
discussed.
