PF-1000 Plasma Focus Facility Research Articles

Influence of intense soft X-ray radiation on the parameters of tracks induced in CR-39 and PM-355 solid state nuclear track detectors

This paper presents the results of the influence of soft X-ray radiation on craters induced in SSNTDs by energetic α particles and protons of energy in the MeV range. We checked two detectors of the PM-355 and CR-39 types in order to verify and compare their resistance to the harsh conditions of high-temperature plasma experiments. To determine this effect some detector samples were first irradiated with α particles emitted from natural α particle sources and protons delivered by a particle accelerator. After that these samples were exposed to soft X ray radiation emitted from an X ray tube and also from the PF-1000 Plasma Focus facility. Doses during X ray irradiations varied from 0 up to tens of kGy. The irradiated samples were then etched in steps and track diameters were determined versus the absorbed dose and etching time and compared with those measured in samples not exposed to X ray radiation.

Study of the fine structure of the plasma current sheath and magnetic fields in the axial region of the PF-1000 facility

Results of measurements of magnetic fields in the plasma pinching region during the compression of the deuterium plasma current sheath (PCS) at the PF-1000 plasma focus facility are presented. The fine structure of the PCS (shock wave-magnetic piston) and its variations in the course of plasma compression toward the facility axis are studied using magnetic probes and laser interferometry. The radial distributions of the plasma density and current in the PCS are compared. It is shown that, in the shock wave region, the electron density of the compressed plasma is on the order of ∼1018 cm−3, whereas the PCS current is almost entirely concentrated in the magnetic piston region—a plasma layer with an electron density of less than 1015 cm−3. Efficient transportation of the current by the PCS into the axial region of the facility in discharges with a high neutron yield (Yn > 1011 neutrons/shot) is detected. It is shown that the total neutron yield is well described by the dependence Yn ≈ (1.5–3) × 1010Ip4, where Ip is the pinch current (in MA) flowing within the region r ≤ 13 mm.

Energy Transformations in Column of Plasma-Focus Discharges With Megaampere Currents

Energy transformations are estimated from experimental results obtained on the PF-1000 plasma focus facility operated with a deuterium gas filling and maximum current of 2 MA, which enabled the neutron yield of >; 1011 to be obtained. Use was made of the laser interferometry images and the recorded signals of hard X-rays (HXRs) and neutrons, as well as voltage, current, and current-derivative waveforms. The calculations of the inductance, derivative of inductance, and resistance of the current sheath enabled the evaluation of energy delivered to the plasma. It was estimated that, during the intensive pulses of the HXRs and neutrons, energy of 3-11 kJ is delivered to the plasma column probably through an anomalous resistance at the time closely before and during pulses of HXR and neutron production. A predominant portion of this energy is effectively used for the acceleration of fast deuterons capable of producing fusion neutrons.

Advantages of the use of solid-state nuclear track detectors in high-temperature plasma experiments

This paper reports on measurements performed with the use of SSNTDs at the PF-1000 Plasma-Focus facility in Warsaw and TEXTOR tokamak in Juelich. Fusion reaction protons were measured within the PF-1000 facility and TEXTOR tokamak.

Application of PM-355 Solid-State Nulear Track Detectors for ion diagnostics in high-temperature plasma experiments

The paper reports on some applications of Solid-State Nuclear Track Detectors, particularly of the PM-355 type, for diagnostics of fusion reaction protons (3 MeV) and other fast ions emitted from high-temperature plasmas. The measurements with the use of these detectors were performed at the PF-1000 Plasma-Focus facility in Warsaw, TEXTOR tokamak in Juelich, and PALS lasersystem in Pargue.

Preliminary neutron experiments with the PF-1000 plasma-focus facility

The paper reports on first neutron-emission experiments carried out with the modernized PF-1000 facility. Current sheath dynamics was investigated by means of high-speed cameras. Based on smear pictures, which were taken through a narrow radial slit, the compression velocity was determined. The total neutron yield and angular distribution anisotropy were measured with four silver-activation counters placed at different angles to the electrode axis. It was found that for each initial D/sub 2/-filling pressure value, with an increase in the charging voltage (V/sub 0/), the neutron yield increases to some maximum and with further increase in V/sub 0/ the neutron emission decreases. The highest neutron yield registered so far has been 2/spl middot/10/sup 11/ per shot. The neutron emission anisotropy seems to be lower than that registered in other plasma-focus experiments. The neutron energy spectra, which were measured by means of a scintillating probe in the upstream direction, have been shifted toward lower energy (2.2-2.3 MeV).

Foam target experiments with the PF-1000 plasma focus facility

This paper describes experiments on foam liners performed with the PF-1000 plasma focus facility. A streak camera has been used to observe interaction of a hydrogen plasma current sheath with a cylindrical foam target. It is shown that a thin foam liner can be uniformly imploded by a plasma focus current sheath.