Research on soft x-rays in high-current plasma-focus discharges and estimation of plasma electron temperature (original) (raw)
Related papers
Peculiar Features of Plasma-Focus Discharges Within PF360 Facility
Czechoslovak Journal of Physics, 2004
The paper reports on recent studies of plasma-focus (PF) discharge dynamics and fusion neutron emission, which were performed with the PF-360 device at the energy level of about 120 kJ and the maximum current of 1.85 MA. Using the high-speed multi-frame imaging system, the behavior of a current-sheath layer during the radial compression phase and of a plasma column during the pinch phase has been investigated. Dynamics of the pinch phase was studied in the visible radiation and soft X-rays simultaneously. Characteristics of the neutron emission from PF discharges, which were carried out with and without the use of planar D2O-ice target, were studied experimentally. In particular, the anisotropy coefficient, defined as a ratio of the fusion-neutron yield to that measured at 90° to the z-axis, i.e. Y n(θ)/Y n (90°), was investigated under different experimental conditions. Various structures of the time-resolved neutron signals were recorded and interpreted, e.g. as a result of a double pinch. Possible mechanisms of the fusion neutron production have also been discussed.
Physica Scripta, 2006
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, CD 2 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.
Czechoslovak Journal of Physics, 2006
The paper reports spectroscopic studies of high-current PF-type discharges. Experiments within the large PF-1000 facility (operated at IPPLM in Warsaw) were aimed on temporal and spatial measurements of the plasma electron density by spectroscopic methods. To study visible-radiation (VR) emission characteristics of various PF-discharges a MECHELLE 900-type spectrometer was used. Measurements were performed at different distances from the electrode outlet. The linear Stark-broadening of deuterium Balmer lines, and particularly that of the D β (486 nm) line, was used to estimate the electronconcentration during and after the PF-pinch phase. Particular attention was paid to a dense-pinch portion at a distance of 8 cm from the electrode ends. The formation of this dense plasma region was also confirmed by images taken with fast X-ray-and VRcameras.
The main issues of research on dense magnetized plasmas in PF discharges
Plasma Sources Science and Technology, 2008
This invited lecture presents the main physical problems met during studies of dense (>10 16 cm −3) plasma influenced by strong magnetic fields, i.e. when ion cyclotron motions are weakly disturbed by electron-ion collisions. Examples of high-current pulsed discharges of the Z-pinch and plasma-focus (PF) type, which can produce dense magnetized plasma (DMP) are presented. The paper concerns mainly PF-type discharges. Particular attention is paid to different phases of such discharges. The breakdown and formation of a dense plasma layer (current sheath), its axial acceleration and the final radial collapse phase are analyzed. The most important physical phenomena are identified, and some theoretical models are described. The main issues of experimental and theoretical studies of DMP in PF-type facilities are shown.
Influence of gas conditions on electron temperature inside a pinch column of plasma-focus discharge
Journal of Physics: Conference Series
The paper reports on soft x-ray emission from high-current discharges in PF-1000U facility operated at 170 kJ. The discharges at static conditions were performed with pure deuterium (D 2) and a mixture of D 2 and neon (Ne). In shots with the gas-puffing 1 cm 3 of D 2 or a (D 2 +Ne) mixture was injected 2 ms before the discharge initiation. Time-integrated x-ray images from a Be-filtered pinhole camera showed that the pinch microstructure depends strongly on gas conditions. In shots with the D 2-, (D 2 +Ne)-or He-puffing distinct "filaments" and "hot-spots" were observed. Time-resolved x-ray pulses were recorded with 4 filtered PINdiodes which recorded signals from 2 regions of 3 cm in diameter (at z = 3 cm and 6 cm from the anode). From a ratio of x-ray pulses, measured behind different filters, it was estimated that at the static D 2-filling electron temperatures (T e) were from 90 eV to 200 eV. At the D 2-filling and-puffing additional x-ray spikes were emitted from "hot-spots" with T e twice higher. In shots at the (D 2 +10%Ne)-filling T e was 4 keV. In shots with the (D 2 +Ne)-mixture puffing intense "hot-spots" were formed, and T e reached 2.2-7.5 keV. At the same conditions "filaments" were reproducible macroscopically, but "hot-spots" were irreproducible.
The Channel-Spark Discharge as a Pulsed, Intense Electron and X-Ray Source
2008
This work is focused on the characteristics of the pulsed electron beam produced in a channel-spark discharge. The beam measurements were made using the self-biasing method of a Faraday cup. We studied also the X-ray emission produced at the electron beam interaction with a target. The dependence of the beam current and energy and of the X-ray intensity on working gas pressure and external capacitor value has been investigated. The pulsed electron beam is polyenergetic and the mean energy of electrons is decreasing in time during the pulse. The information concerning the electron beam characteristics is directly related to an efficient ablation of targets and thus to the growth of high quality thin films. The X-ray emission characteristics prove the feasibility of a compact, pulsed X-ray source, of low energy photons (less than about 10 keV), based on the channel-spark discharge.
Plasma Physics and Controlled Fusion, 2020
The differences in performance of a 1.9 kJ plasma-focus device PACO assembled with three different cathode configurations are experimentally qualified. In particular, the current sheath kinetics and the neutron yield operating with deuterium gas are systematically studied for the whole range of neutron-producing pressures, and the measurements are analyzed searching for relations between relevant physical magnitudes. The pinching time was found correlated with the dimensionless driver parameter, and this feature was found statistically independent of the cathode. The variation of the inductance jump associated with the radial collapse stage is used to estimate the effective pinch length, () 7.3 1.6 mm, and radius, () 3.6 2.1 mm. The maximum production in a single shot was registered for the smallest cathode radius, 41 mm, whereas the intermediate cathode radius, 45 mm, scored better in average. In all configurations, the neutrons per deuteron pair correlates fairly well with an estimation of the effective equilibrium temperature of the pinch, which suggests a prevalence of thermonuclear neutrons measured perpendicularly to the focus axis.