Advanced real-time evaluation and data quality monitoring model integration with FPGAs for tokamak high-performance soft X-ray diagnostic system

Based on the publications regarding new or recent measurement systems for the tokamak plasma experiments, it can be found that the monitoring and quality validation of input signals for the computation stage is done in different, often simple, ways. In the paper is described the unique approach to implement the novel evaluation and data quality monitoring (EDQM) model for use in various measurement systems. The adaptation of the model is made for the GEM-based soft X-ray measurement system FPGA-based. The EDQM elements has been connected to the base firmware using PCI-E DMA real-time data streaming with minimal modification. As additional storage, on-board DDR3 memory has been used. Description of implemented elements is provided, along with designed data processing tools and advanced simulation environment based on Questa software

Feasibility of FPGA to HPC computation migration of plasma impurities diagnostic algorithms

We present a feasibility study of fast events parameters estimation algorithms regarding their execution time. It is the first stage of procedure used on data gathered from gas electron multiplier (GEM) detector for diagnostic of plasma impurities. Measured execution times are estimates of achievable times for future and more complex algorithms. The work covers usage of Intel Xeon and Intel Xeon Phi - high-performance computing (HPC) devices as a possible replacement for FPGA with highlighted advantages and disadvantages. Results show that less than 10 ms feedback loop can be obtained with the usage of 25% hardware resources in Intel Xeon or 10% resources in Intel Xeon Phi which leaves space for future increase of algorithms complexity. Moreover, this work contains a simplified overview of basic problems in actual measurement systems for diagnostic of plasma impurities, and emerging trends in developed solutions

Measurement capabilities upgrade of GEM soft X-ray measurement system for hot plasma diagnostics

The paper presents improvements of the developed system for hot plasma radiation measurement in the soft X-ray range based on a Gas Electron Multiplier (GEM) detector. Scope of work consists of a new solution for handling hardware time-synchronization with tokamak systems needed for better synchronization with other diagnostics and measurement quality. The paper describes the support of new modes of triggering on PC-side. There are communication and data path overview in the system. The new API is described, which provide separate channels for data and control and is more robust than the earlier solution. Work concentrates on stability and usability improvements of the implemented device providing better usage for end-user

Soft X-ray diagnostic system upgrades and data quality monitoring features for tokamak usage

The validation of the measurements quality after on-site diagnostic system installation is necessary in order to provide reliable data and output results. This topic is often neglected or not discussed in detail regarding measurement systems. In the paper recently installed system for soft X-ray measurements is described in introduction. The system is based on multichannel GEM detector and the data is collected and sent in special format to PC unit for further postprocessing. The unique feature of the system is the ability to compute final data based on raw data only. The raw data is selected upon algorithms by FPGA units. The FPGAs are connected to the analog front-end of the system and able to register all of the signals and collect the useful data. The interface used for data streaming is PCIe Gen2 x4 for each FPGA, therefore high throughput of the system is ensured. The paper then discusses the properties of the installation environment of the system and basic functionality mode. New features are described, both in theoretical and practical approach. New modes correspond to the data quality monitoring features implemented for the system, that provide extra information to the postprocessing stage and final algorithms. In the article is described also additional mode to perform hardware simulation of signals in a tokamak-like environment using FPGAs. The summary describes the implemented features of the data quality monitoring features and additional modes of the system

WPROWADZENIE DO ZAGADNIENIA TOMOGRAFII W ALGORYTMACH POSTPROCESSINGU DLA REAKTORÓW TYPU TOKAMAK

The collaboration of authors led to implementing advanced and fast systems for diagnostics of plasma content in tokamaks. During the development of systems it is planned to add new functionalities, in particular, the algorithms of tomographic reconstruction to obtain  information on three dimensional distribution of plasma impurities. In the article the idea of tomographic reconstruction is introduced and issues of performance and adequate hardware selection are presented.Wieloletnia współpraca autorów przyczyniła się do powstania zaawansowanych, szybkich mechanizmów diagnostyki składu gorącej plazmy tokamakowej. W ramach rozbudowy systemów zamierza wprowadzić się szereg nowych funkcjonalności, w tym algorytmy rekonstrukcji tomograficznej. Pozwoli to na uzyskanie informacji o przestrzennym rozkładzie nieczystości plazmy w reaktorze. Praca przedstawia koncepcję tomografii tego typu oraz przeprowadzona jest dyskusja nad zagadnieniami wydajności i doboru sprzętu

Effect of charging-up and regular usage on performance of the triple GEM detector to be employed for plasma radiation monitoring

After the problem of high-temperature plasma confinement, construction of diagnostics that is able to identify plasma contamination with impurities and to determine impurity distribution is another critically important issue. Solution of this problem would enable progress towards the success in controlled thermonuclear fusion. A new diagnostics, based on Gas Electron Multiplier (GEM) technology, has been recently developed for poloidal tomography focused on radiation of the metal impurities by monitoring in Soft X-Ray (SXR) region. GEM based detectors would undergo much less damage by neutrons than standard semiconductor diodes which results in better operational stability. This paper emphasizes the results of the latest examination of this type of detectors, showing influence of the charging-up effect on the detector performance and its physical properties for expected plasma radiation intensity. In addition, an undesired influence of aging of the detector window’s material on the performance of the GEM detector is also shown: regular (moderate or active) usage could lead to changes of material’s morphology as well as its composition. This study confirms the importance of further research into material’s optimization of GEM detectors used as a base for SXR tomographic diagnostics aimed to work under different plasma radiation conditions

High-Performance Lightweight HLS Generator Module of Normally Distributed Random Numbers in FPGAs

This paper focuses on the problem of high-performance streaming random number generation in the range of uniform and normal distributions in FPGAs. Our work is focused on lightweight implementation, suitable for a wide range of FPGAs. First, we review the existing types of random generation modules. Next, in this paper we present the construction of the designed generator. We divide it into two sections: Stream Uniform Numbers Generator Implementation and Cumulative Distribution-Based Stream Gaussian Generator. Each design step was verified in the scope of the quality of the output data, especially regarding the produced distributions. The results obtained are compared with existing solutions. We mainly consider resource utilization and throughput. We also add our quality factor, which is an effective utilization of FPGAs. Despite quality results, our modules were implemented using a high-level synthesis language (C/C++), contrary to typical hardware description level (HDL) approaches. It provides the opportunity to implement the proposed algorithms on CPUs. It was tested with positive results, thus highlighting the versatility of the solution that is unavailable in terms of HDL implementations. Our designed generators were confirmed to stand out for their satisfactory performance while occupying low logical resources

GEM detector charge signals sequencer implementation for WEST experiment

This paper focuses on implementation of the charge signal sequencer in FPGA chip dedicated for GEM detector. First is described structure of GEM detector for WEST experiment developed by IPPLM and Warsaw University of Technology. Then the article explains why signal sequencer is needed in the new system and shortly presents how it works. It collects data from all detector channels and sends it out in unambiguous order to PC. It plays a big role in a data pipeline. Proper order of data improves parameters of the system, decreases the latency and simplifies computations on PC side. The article explains technical aspects of the implementation like architecture, blocks, dataflow or configuration features. In the end, there are presented results of the implementation

New directions in the construction of tokamak plasma impurity diagnostics systems

Thermonuclear fusion will be a promising energy source soon. Sophisticated systems are called tokamaks (toroidal chambers with magnetic coils) to generate hot plasma. Currently, the fusion process is not yet fully controlled. To better understand it, scientists use diagnostic systems that record plasma behavior. A particular group of diagnostic systems is responsible for the analysis of plasma impurities. The article briefly discusses the method of producing energy from a controlled nuclear fusion. Then, it presents groups of diagnostic systems in terms of their functions and focuses on systems dedicated to monitoring and analyzing plasma impurities. Parameters and limitations of representative currently used diagnostics systems for plasma impurities are described. In the end, the functional and technical requirements of plasma diagnostic systems designed for new tokamaks such as ITER and DEMO are discussed

Design and development of soft x-ray diagnostics based on GEM detectors at IPPLM

The search for new technologies in the field of plasma diagnostics entails the increasing demands on the radiative stability of the used materials due to development and usage of fusion facilities, where the study of processes occurring during the interaction of radiation with matter has become particularly important. Currently, a new X-ray imaging detection technology is required for tokamaks such as ITER. X-ray detectors that are being used in existing equipment may rapidly degrade due to large neutron fluxes characteristic for the tokamak environment. Despite the relatively wide use of semiconductor detectors to record SXR radiation (generally ionizing radiation), gas detectors are promising candidates that are suited much better for use in future fusion reactors given their resistance to neutron radiation. The most promising representative of the new gas detector class is the so called Gas Electron Multiplier (GEM), which is characterized by high amplification factor of the primary charge that is originated from photon absorption. Its main advantages are the compactness of the detector, good temporal and spatial resolutions, the ability to discriminate against photon energy and better neutron resistance compared to existing systems. All this makes such a detection system a potentially better candidate for soft X-ray measurements in the ITER and DEMO reactors. In this work, a new type of detection system based on GEM technology was proposed for soft X-ray measurements in the ITER reactor-oriented research, which is being developed at IPPLM