Prototype of Data Acquisition Systems for ITER Divertor Thomson Scattering Diagnostic

Abstract

Thomson scattering diagnostic is the most reliable and widely used method to measure electron temperature and density profiles of magnetically confined plasma. The prototype of data acquisition system for ITER divertor zone Thomson scattering diagnostic has been recently developed at the Budker Institute of Nuclear Physics (Novosibirsk, Russia). The small power (∼10−8W) and short duration (∼3–5 ns) are the main technical problems of the diagnostic. For detection and recording such low level signals the prototype of uniquely designed complex data acquisition system was developed. This system consists of 48 photodetector modules with 0–200MHz bandwidth, 48 simultaneously sampling ADC modules and synchronization subsystem. The photodetector modules are based on avalanche photodiodes and extremely low noise transimpedance preamplifiers. ADC modules include fast analog to digital convertors and digital units based on the Field-Programmable Gate Array for data processing and storage. The synchronization subsystem is used to form triggering pulses and to organize the simultaneously mode of ADC modules operation. Features of the system allow detection and recording short duration (3–5 ns) scattered pulses with 2GHz sampling rate and 10-bit total resolution in oscilloscope mode. At present, the system is tested on GLOBUS tokamak (St. Petersburg, Russia).