Conference paper

Overview of Soft X-ray GEM Diagnostic System for Tokamak Impurities Monitoring

A. Wojeński (Warsaw Univ. of Techn., Poland)

Plasma impurities monitoring is especially important in scope of achieving long plasma duration in tokamak. One of the methods is acquisition of soft X-ray radiation from the tokamak. The measurement process is very difficult, since the photons are received in big streams, during whole plasma duration time (and also after plasma shutdown), with no time correlation between events. Therefore, the measurement system needs to work with high speed data acquisition and processing. To measure the SXR radiation, system needs to be designed in a special way, including radiation hard electronics, proper cooling, immunity to EMI especially for analog signals. The described system is based on the GEM detector, used as a sensor for SXR measurements in range of 0.5 – 20 keV. The detector contains more then 100 channels with analog signal outputs from channels. The system is processing raw data, in order to offer maximum quality to the output data. Therefore, custom electronics has been designed including: analog frontend boards, analog-digital boards, multichannel FPGA data preprocessing and streaming boards, PCI-E interconnection 8-to-1 switch. The FPGA firmware contains blocks of ADC fast interfaces working in SERDES mode, data selection path, algorithms for data distribution through PCI-Express interface to the embedded PC. The system is based on the PCI-Express with data processing done in the embedded, high performance PC. Additional hardware units have also been designed, including high voltage power supply unit, custom water cooling system, protection system. For such a complex system, advanced control and readout software has also been designed. The system is automatically setup and diagnosed by the low-level modular software. The CPU optimized data dispatchers and processing algorithms has also been implemented. Various tests of the system with isotope sources and X-ray tubes has been performed to verify the system data processing path and performance.

Download one page abstract

Receipt of papers:

February 29th, 2020

Notification of acceptance:

April 25th, 2020

Registration opening:

April 30th, 2020

Final paper versions:

May 15th, 2020