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The implosion of a solid deuterium gas-puff Z-pinch was studied on the S-300 pulsed power generator [A. S. Chernenko, et al., Proceedings of 11th Int. Conf. on High Power Particle Beams, 154 (1996)]. The peak neutron yield above [10.sup.10] was achieved on the current level of 2 MA. The fusion neutrons were generated at about 150 ns after the current onset, i.e., during the stagnation and at the beginning of the expansion of a plasma column. The neutron emission lasted on average 25 ns. The neutron energy distribution function was reconstructed from 12 neutron time-of-flight signals by the Monte Carlo simulation. The side-on neutron energy spectra peaked at 2.42 [+ or -] 0.04 MeV with about 450-keV FWHM. In the downstream direction (i.e., the direction of the current flow from the anode toward the cathode), the peak neutron energy and the width of a neutron spectrum were 2.6 [+ or -] 0.1 MeV and 400 keV, respectively. The average kinetic energy of fast deuterons, which produced fusion neutrons, was about 100 keV. The generalized beam-target model probably fits best to the obtained experimental data. Index Terms--Deuterium, fusion reaction, gas puff, Monte Carlo reconstruction, neutron energy spectra, neutrons, Z-pinch.

Fast neutrons from deuteron-deuteron fusion reactions were used for a study of fast deuterons in the PF-1000 plasma-focus device. The energy spectrum of neutrons was determined by the time-of-flight method using ten scintillation detectors positioned downstream, upstream, and side-on the experimental facility. Neutron energy-distribution functions enabled the determination of axial and radial components of energy of deuterons producing the fusion neutrons, as well as a rough evaluation of the total energy distribution of all fast deuterons in the pinch. It was found that the total deuteron energy-distribution function decreases with the deuteron energy more slowly than the tail of the Maxwellian distribution for 1-2-keV deuterons. Index Terms--Energy spectrum of fast deuterons, neutron production, plasma diagnostics, plasma focus (PF).

In the PF 1000 plasma-focus device, deuterium is used as a filling gas for the study of fast neutrons (originated from D-D fusion reactions) and X-rays. The X-ray signals have two peaks. The first peak corresponds to the time of the minimum diameter of the pinch phase, as recorded by the visible frames. The second peak has its maximum 150 to 200 ns later. The electrons with energy above a few hundreds of kiloelectronvolts are registered mostly at the first peak in both axial directions. Upstream and downstream electrons differ in their intensity (ratio 3:1), temporal profile, and time of their maximum. The energy of the neutrons and the time of their generation are determined by the time-of-flight method using six or seven scintillation detectors positioned in the axial direction. Each neutron pulse has a dominant portion of beam-target origin with downstream energies up to 3.2 MeV and the final portion of the neutrons with energies in the range of 2.2 to 2.7 MeV. The evolution of the neutron pulses correlates with the visible frames. The first pulse correlates with the fast downstream motion of the intense radiating axis layer of the pinch and with the forming and existence of the radiating bail-shaped structure at the bottom of the dilating plasma sheath. The second neutron pulse correlates with the exploding of the plasma after the second pinching, and with the forming and existence of the structure of the dense plasma at the bottom of the dilating current sheath, which is similar to the first pulse. Index Terms--Neutron production, plasma diagnostics, plasma focus (PF), X-ray radiation.

Z-pinch experiments, which are formed from a 15-[micro]m diameter carbon fiber in a vacuum, were conducted using a simple capacitor bank. After the breakdown, a low-density coronal plasma was formed while the fiber diameter remained almost unchanged. This low-density corona (ion density of about [10.sup.16] [cm.sup.-3]) was carrying almost all the current of the order of 10 kA. When the current had built up, i.e., after about 150 ns, the implosion of the corona onto the central fiber occurred. The implosion velocity approached the value of 2 x [10.sup.5] m/s. When the imploded corona had reached the fiber, the dip in dI/dt, a voltage peak up to 10 kV and an extreme-ultraviolet (XUV) pulse of a 10-30-ns width were observed. XUV radiation was emitted from several bright spots, which corresponded to the interaction of m = 0 instability necks with the dense core. The electron temperature and density were approximately 80 eV and [10.sup.19] [cm.sup.-3], respectively. Although the presence of a fiber did not significantly suppress MHD instabilities, they were not disruptive. After the fiber ablation, i.e., after 500 ns, the material evaporated from the electrodes started to play a dominant role. When MHD instabilities had developed in the imploding plasma column, XUV, soft X-ray, and hard X-ray pulses were emitted from several bright spots, particularly near the anode. At that time, the voltage peak of up to 30 kV was detected. The measurement of voltage and current enabled the determination of a plasma resistance and the energetics of the Z-pinch. Index Terms--Bright spots, carbon, Extreme ultraviolet (XUV) radiation, fiber Z-pinch, implosion, plasma diagnostics.

The evolution of a neon implosion of low energy discharge (4 kJ, 40 kV, 150 kA, 1.1 [micro]s) was studied using X-ray, schlieren, and high speed electrooptical visible gated quadro camera diagnostics. The geometry, an helical structure of pinched column, two steps of pinching, and X-ray emission have been studied. The hypothesis of an axial component of magnetic field generation, the helical shape of the magnetic and electric field lines, and the release of magnetic energy during the second pinching of the column are discussed. Index Terms - Charged couple device camera, p-i-n structure, X-ray and short ultraviolet radiation.

Emission of several tens of mA/cm^2 currents carried by MeV-protons is reported for plasmas produced by a beam of the 3-TW kJ-class Prague Asterix Laser System (PALS) focused onto foil targets of various thicknesses. The maximum proton energy of 4.2 MeV is observed at a modest irradiance (I\lambda^2\sim 2\times 10^16~W~cm^-2\mum^2). According to the maximum ion energy scaling EM\sim (I{\lambda}^{2})^{0.4} found for picosecond lasers such a value should be reached at I\lambda^2\sim 3\times 10^18~W~cm^-2~\mum^2. Enhancement of the maximum proton energy can be explained by nonlinear interaction of the PALS laser beam with the generated plasma. Nonlinear effects also result in enhancement in the yield of fusion neutrons from CD2 plasma. The obtained yield of 4\times 10^5 DD-neutrons per laser energy is comparable to those obtained by the use of ps- and fs-lasers irradiating targets with I\lambda^2\sim 10^19~W~cm^-2~\mum^2. [ABSTRACT FROM AUTHOR]

This paper describes the investigation of the influence of target material atomic number ( Z) on the laser-produced plasma pressure. For this reason, several target materials representing a wide range of atomic numbers ( Z = 3.5 - 73), i.e. plastic ( CH), Al, Cu, Ag, and Ta, were used. The results presented show that the plasma pressure decreases with growing atomic number but in a limited range of Z only. For higher Z, starting approximately from Z = 47 (Ag), the plasma pressure becomes constant, as confirmed by interferometric measurements and x-ray plasma imaging. [ABSTRACT FROM AUTHOR]

A plasma column generated in the PF-1000 device working in deuterium gas at a current level of 1 MA was investigated with interferometric diagnostics and scintillation detectors. The beam of diagnostic laser of 527-nm wavelength was optically split into 16 beams with a time delay in the range from 0 to 220 ns. This diagnostic tool makes possible the imaging of the evolution of pinch geometry, the axial and radial distributions of plasma density in the column at the stagnation phase, and their comparison with the evolution of X-ray and neutron production. The evolution of dense structure is described with respect to its importance for fusion processes. [ABSTRACT FROM AUTHOR]