Multichannel gas electron multiplier based soft x-ray field-programmable gate array measurement system for W-Environment in Steady-state Tokamak (WEST): Hardware, installation, and first plasma acquisition

Abstract

The work describes a novel approach to the design of a fast, multichannel measurement system for plasma diagnostics [A. Wojenski et al., Fusion Eng. Des. 123, 727 (2016)]. Its main scope is to provide measurements of soft X-ray (SXR) emission during plasma phenomena at the W-Environment in Steady-state Tokamak (WEST), especially for monitoring and tracing tungsten impurities. This paper describes the vertical Gas Electron Multiplier (GEM) camera installed at the WEST [M. Chernyshova et al., J. Instrument. 10, P10022 (2015)]. The designed GEM detector readout board has more than 100 channels, resulting in high-performance requirements for the data acquisition and processing system. The novel system construction approach is that the unit works on the raw signals providing a high quality of the data, especially in the scope of pileup effect analysis. In the case of doubtful results, the source data can be easily reviewed offline. The data selection and transmission are done in Field-Programmable Gate Arrays (FPGAs) on the custom boards with the custom Peripheral Component Interconnect (PCI)-Express Gen2 switch that allows us to register signals from multiple FPGAs and then process the data by complex algorithms [G. Kasprowicz et al., J. Fusion Energy 38, 480 (2019)]. The firmware is replaceable and different working modes can be applied (some under verification): global trigger mode, high-speed data serialization, and extended signal registration. Low level optimized central processing unit software for data readout was also designed [P. Linczuk et al., J. Instrum. 14, C05001 (2019)]. The installation of the system is described due to complex system components’ distribution. The first results of the successful acquisition of the plasma at the WEST are discussed. The corresponding SXR energy and topology spectra were computed. Those are the first technical measurements of the system to ensure verification of data quality.

High-Performance FPGA Streaming Data Concentrator for GEM Electronic Measurement System for WEST Tokamak

“…The developed system and firmware were prepared and designed to meet the mentioned requirements. The detector developed for the WEST experiment can be classified as a second-revision detector and was successfully installed on the WEST tokamak [21]. The first revision was designed for the JET experiment.…”

“…The installed system is the second generation of the SXR diagnostics that were first committed to the Joint European Torus (JET) tokamak as a part of the KX1 spectrometer [20]. Its main advantage is the simplified construction combined with radiation-hard design, effective data processing, and ability to register raw analog pulses (corresponding to each photon registered by the GEM detector) during each plasma reaction (for more details, see, e.g., [21]).…”

Soft real-time data processing solutions in measurement systems on example of small-scale GEM based x-ray spectrometer

“…Various examples provided here are related to X-ray spectroscopy and hot plasma diagnostics in the tokamaks -area with the use of a Gas Electron Multiplier (GEM) detector, which is being developed for a while by our group [1,2,3].…”

International Journal of Electronics and Telecommunications

“…ECENTLY installed soft X-ray measurement system for plasma impurities monitoring was used during plasma campaign measurements in 2019 year [1]. At the moment, the vertical GEM camera is working, the most difficult one for the installation due to direct in-port detector placement [2]. The system consists of 103 Line-Of-Sights, thus allowing a large angle of tokamak vessel view, especially the divertor part.…”

“…Therefore, it is especially valuable to design various Data Quality Monitoring (DQM) tools implemented in FPGAs to provide detailed overview of system behaviour during measurements. The system is already working in global trigger mode [2] for GEM diagnostic stage. There are also ongoing laboratory tests of local/serialized triggering mode [8], [9], in order to achieve several times higher data compression.…”