Development Of Beam Emission Spectroscopy For Turbulence Transport Study In Heliotron J

This paper describes the development study of the beam emission spectroscopy (BES) for the turbulent transport study in Heliotron J. Modification of the sightlines (10 x 4 for edge and 10 x 2 for edge) enables us to obtain 2-dimensional BES imaging. The cooling effect on the reduction in the electrical noise of avalanche photodiode (APD) assembly has been investigated using a refrigerant cooling system. When the temperature of the APD element has set to be -20 degrees C, the electrical noise can be reduced more than 50%. The measurement error of the phase difference in the case of low signal level has been tested by two light-emitting diode lamps. The APD cooling has an effect to improve the measurement error at the low signal level of APD. Published by AIP Publishing.