CBM Experiment local and global implications

The research area of the compressed baryonic matter - CBM experiment (FAIR/GSI in Darmstadt) is sub-nuclear physics, thus hadron-baryon and quark-gluon, and the essence of phase transitions in the area of hot nuclear matter, and dense strongly interacting matter. Our interest in this paper are mainly considerations on the impact of such large infrastructural experiments and possibilities they give to local, smaller but very active, university based research groups and communities. Research and technical input from such groups is depicted on the background of the CBM detector infrastructure and electronic instrumentation just under design and test fabrication for this experiment. An essential input to this research originates from Poland via the agreed  in-kind contribution. The areas of expertise of these groups are: superconductivity, structural large scale cabling, precision machined parts, RF and microwave technology, analog and advanced digital electronics, distributed measurement and control systems, etc

Zero-Suppression Trigger Mode for GEM detector measurement system

A novel approach to a trigger mode in the GasElectron Multiplier (GEM) detector readout system is presented.The system is already installed at WEST tokamak. The articlebriefly describes the architecture of the GEM detector and themeasurement system. Currently the system can work in twotrigger modes: Global Trigger and Local Trigger. All trigger processingblocks are parts of the Charge Signal Sequencer modulewhich is responsible for transferring data to the PC. Therefore,the article presents structure of the Sequencer with details aboutbasic blocks, theirs functionality and output data configuration.The Sequencer with the trigger algorithms is implemented inan FPGA chip from Xilinx. Global Trigger, which is a defaultmode for the system, is not efficient and has limitations due tostoring much data without any information. Local trigger whichis under tests, removes data redundancy and is constructed tosend only valid data, but the rest of the software, especially on thePC side, is still under development. Therefore authors proposethe trigger mode which combines functionality of two existingmodes. The proposed trigger, called Zero Suppression Trigger, iscompatible with the existing interfaces of the PC software, butis also capable to verify and filter incoming signals and transferonly recognized events. The results of the implementation andsimulation are presented

Design of soft-X-ray tomographic system in WEST using GEM detectors

In metallic tokamaks, the interplay between particle transport and MagnetoHydroDynamic (MHD) activity might lead to impurities accumulation and finally to disruption. Studying such phenomena is thus essential if stationary discharges are to be achieved. Measuring the soft X-ray (SXR) radiation ([0.1 keV; 20 keV]) of magnetic fusion plasmas is a standard way of accessing valuable information on particle transport and MHD. Generally, like at Tore Supra (TS), the analysis is performed with a 2D tomographic system composed of several cameras equipped with silicon barrier diodes (SBD). On WEST the installation of an upper divertor masks many of the actual TS vertical diodes so that no proper tomography is possible. This paper presents the design of a new SXR diagnostic for the WEST project developed in collaboration with IPPLM (Poland) and the Warsaw University of Technology, based on a triple gas electron multiplier (GEM) detector. Preliminary simulations performed to size and position the detector and its electronics inside the vertical thimble are also presented, in particular estimation of magnetic field and temperature variation affecting GEM spatial resolution and signal quality. As a conclusion, perspectives about tomographic capabilities of the new system for studying impurity transport are given

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)