Karol Malinowski

Application of intense plasma-ion streams emitted from powerful PF-type discharges for material engineering

This paper concerns various applications of powerful ion- and plasma-streams generated by high-current pulse discharges realized within different plasma-focus (PF) facilities. General characteristics of the emitted plasma-ion streams are summarized. The possibility of application of special arrangements, e.g. cryogenic targets, CD2 or metal wires, hydrogen or deuterium getters, special alloy targets, etc, is described. The paper presents results of different experiments oriented on the interaction of the pulsed plasma-ion streams with various material targets placed inside PF-360 device (at IPJ in Swierk) and PF-1000 facility (at IPPLM in Warsaw). Attention is paid to plasma–target interactions and influence of the material targets on emission characteristics of the PF-type discharges. The diagnostics includes current and voltage measurements, optical photography and spectroscopy, x-ray emission observations and fast-neutron measurements (from deuterium discharges). Particular attention is paid to time-resolved spectroscopic studies. The use of pulsed ion- and plasma-streams for modifications of different materials, e.g. those of particular interest for the construction of nuclear fusion reactors, is described.

Investigation of interactions of intense plasma streams with tungsten and carbon fibre composite targets in the PF-1000 facility

This paper presents the results of research on interactions of pulsed plasma streams, as generated by the PF-1000 facility, with solid targets made of tungsten or carbon fibre composite. The device was equipped with a modified inner electrode with a central tungsten insert of 50mm in diameter. The PF-1000 experimental chamber was filled with pure deuterium at p0 = 1.47hPa. At the charging voltage U0 = 24kV, the maximum current amounted to 1.8MA in about 5.5µs after the discharge initiation. The investigated targets were located on the z-axis, at a distance of 9cm from the inner electrode end. For plasma diagnostics, optical emission spectroscopy, 16-frame laser interferometry and a soft x-ray measuring system of four silicon pin diodes were used. It was observed that plasma streams reached the target about 100ns after the maximum compression and generated a plasma pillow at the sample surface, as proved from time-resolved optical spectra.

The cluster charge identification in the GEM detector for fusion plasma imaging by soft X-ray diagnostics

The measurement system based on gas electron multiplier detector is developed for soft X-ray diagnostics of tokamak plasmas. The multi-channel setup is designed for estimation of the energy and the position distribution of an X-ray source. The focal measuring issue is the charge cluster identification by its value and position estimation. The fast and accurate mode of the serial data acquisition is applied for the dynamic plasma diagnostics. The charge clusters are counted in the space determined by 2D position, charge value, and time intervals. Radiation source characteristics are presented by histograms for a selected range of position, time intervals, and cluster charge values corresponding to the energy spectra.

GEM detector development for tokamak plasma radiation diagnostics: SXR poloidal tomography

An increased attention to tungsten material is related to a fact that it became a main candidate for the plasma facing material in ITER and future fusion reactor. The proposed work refers to the studies of W influence on the plasma performances by developing new detectors based on Gas Electron Multiplier GEM) technology for tomographic studies of tungsten transport in ITER-oriented tokamaks, e.g. WEST project. It presents current stage of design and developing of cylindrically bent SXR GEM detector construction for horizontal port implementation. Concept to overcome an influence of constraints on vertical port has been also presented. It is expected that the detecting unit under development, when implemented, will add to the safe operation of tokamak bringing creation of sustainable nuclear fusion reactors a step closer.

Mass- and energy-analyses of ions from plasma by means of a miniature Thomson spectrometer

The paper presents an improved version of a miniature mass-spectrometer of the Thomson-type, which has been adopted for ion analysis near the dense plasma region inside a vacuum chamber. Problems connected with the separation of ions from plasma streams are considered. Input diaphragms and pumping systems, needed to ensure good vacuum inside the analyzing region, are described. The application of the miniature Thomson-type analyzer is illustrated by ion parabolas recorded in plasma-focus facility and rod plasma injector experiment. A quantitative analysis of the recorded ion parabolas is presented. Factors influencing accuracy of the ion analysis are discussed and methods of the spectrometer calibration are described.

On coating adhesion during impulse plasma deposition

The impulse plasma deposition (IPD) technique is the only method of plasma surface engineering (among plasma-based technologies) that allows a synthesis of layers upon a cold unheated substrate and which ensures a good adhesion. This paper presents a study of plasma impacts upon a copper substrate surface during the IPD process. The substrate was exposed to pulsed N2/Al plasma streams during the synthesis of AlN layers. For plasma–material interaction diagnostics, the optical emission spectroscopy method was used. Our results show that interactions of plasma lead to sputtering of the substrate material. It seems that the obtained adhesion of the layers is the result of a complex surface mechanism combined with the effects of pulsed plasma energy impacts upon the unheated substrate. An example of such a result is the value of the critical load for the Al2O3 layer, which was measured by the scratch-test method to be above 40 N.

Development of a diagnostic technique based on Cherenkov effect for measurements of fast electrons in fusion devices

A diagnostic technique based on the Cherenkov effect is proposed for detection and characterization of fast (super-thermal and runaway) electrons in fusion devices. The detectors of Cherenkov radiation have been specially designed for measurements in the ISTTOK tokamak. Properties of several materials have been studied to determine the most appropriate one to be used as a radiator of Cherenkov emission in the detector. This technique has enabled the detection of energetic electrons (70 keV and higher) and the determination of their spatial and temporal variations in the ISTTOK discharges. Measurement of hard x-ray emission has also been carried out in experiments for validation of the measuring capabilities of the Cherenkov-type detector and a high correlation was found between the data of both diagnostics. A reasonable agreement was found between experimental data and the results of numerical modeling of the runaway electron generation in ISTTOK.

Characteristics of four-channel Cherenkov-type detector for measurements of runaway electrons in the ISTTOK tokamak.

A diagnostics capable of characterizing the runaway and superthermal electrons has been developing on the ISTTOK tokamak. In previous paper, a use of single-channel Cherenkov-type detector with titanium filter for runaway electron studies in ISTTOK was reported. To measure fast electron populations with different energies, a prototype of a four-channel detector with molybdenum filters was designed. Test-stand studies of filters with different thicknesses (1, 3, 7, 10, 20, 50, and 100 μm) have shown that they should allow the detection of electrons with energies higher than 69, 75, 87, 95, 120, 181, and 260 keV, respectively. First results of measurements with the four-channel detector revealed the possibility to measure reliably different fast electrons populations simultaneously.

Measurements of ion micro-beams in RPI-type discharges and fusion protons in PF-1000 experiments

The paper reports on experimental investigation of micro-beams of fast ions emitted from high-current pulse discharges within the RPI-IBIS (Rod Plasma Injector) device in Swierk and the PF-1000 (Plasma-Focus) facility in Warsaw. Time-integrated ion measurements were performed with pinhole cameras equipped with solid-state nuclear track detectors (SSNTDs). Before expositions the SSNTDs were calibrated by means of mono-energetic ion beams and/or Thomson-type parabolas recorded on the detector samples. The ion-pinhole cameras were placed at different angles to the symmetry axes of the investigated facilities. In order to record fast (>3 MeV) protons, which originated from D‐D nuclear fusion reactions in the PF-1000 facility, the SSNTDs were covered with appropriate Al filters. Time-integrated measurements of the fusion protons were performed for chosen series of PF discharges. The paper presents for the first time detailed maps of the fast proton fluxes, which makes it possible to draw conclusions regarding the spatial distribution of the fusion-proton sources.

Evaluation of FPGA to PC feedback loop

The paper presents the evaluation study of the performance of the data transmission subsystem which can be used in High Energy Physics (HEP) and other High-Performance Computing (HPC) systems. The test environment consisted of Xilinx Artix-7 FPGA and server-grade PC connected via the PCIe 4xGen2 bus. The DMA engine was based on the Xilinx DMA for PCI Express Subsystem1 controlled by the modified Xilinx XDMA kernel driver.2 The research is focused on the influence of the system configuration on achievable throughput and latency of data transfer.