Fusion Science and Technology / Volume 51 / Number 2T / February 2007 / Pages 292-294
Technical Paper / Open Magnetic Systems for Plasma Confinement
In order to extensively and simultaneously analyze frequencies of fluctuations of the end-loss ion current, we prepared three types of analog-to-digital converters (ADC) whose sampling frequencies are 62.5 kHz, 333 kHz and 64 MHz, respectively. The low and intermediate frequency ADCs have 20 channels. The high frequency ADC has a single channel and analyzes the summed signal of the MCP detector. We observed the fluctuations of Alfvén ion cyclotron (AIC) mode and the beat phenomenon appeared in the end-loss ion current. On the energy distribution functions of the end-loss ion, we have already observed the gentle humps. We found the relation between the gentle humps and the AIC waves observed in the end-loss ion current, and confirmed by the pitch angle analysis of the beat fluctuation that the AIC waves significantly influenced the trapped ion to transport into the loss region.