A. Y. Shashkov

Time of Neutron Production on Z‐Pinch and Plasma Focus Devices

In this paper we present the results obtained on the plasma focus PF‐1000 in IPPLM Warsaw and on the z‐pinch S‐300 in RRC Kurchatov Institute in Moscow using a deuterium load. On the PF‐1000 plasma‐focus device with deuterium filling gas the energy of neutrons and time of their generation are determined by time‐of‐flight method from seven scintillation detectors positioned in the axial direction. The neutron signals (total yield ∼1011 neutrons per shot) correlate with hard x‐rays and their maximum occur ∼150–200 ns after the pinch phase. The initial portion of neutron pulse has beam‐target origin with downstream energies up to 2.8–3.2 MeV and the final portion of neutrons has isotropic distribution of energies in the range of 2.2–2.7 MeV. The z‐pinch experiments were performed on the S‐300 generator with the load formed from a deuterated CD2 fibre in the axis of a tungsten wire array. The energy of neutrons and time of their generation are determined by time‐of‐flight method from 5 scintillation detectors...

Energy transformation in Z-pinch and plasma focus discharges with wire and wire-in-liner loads

The results of the study of the Z-pinch and plasma-focus plasmas at presence of the axial C, Al, or Cu wires of sufficient high diameter are discused in this paper. The wire was positioned on the top of the inner electrode of the PF 1000 plasma focus (1.8 MA, IPPLM Warsaw), or at the axis with or without the tungsten or alumine wire array load at the S-300 facility (3 MA, RRC Kurchatov Institute, Moscow), and at the axis of the small Z-pinch Z-150 (50 kA, CTU Prague). The plasma corona around the wire was generated both by the current going through the wires and by the implosion of the wire array or of the current sheath. The experiments showed interesting results often observed in some shots of Z-pinch type discharges - existence of helical structures, two relatively long and stable pinch phases, oscillation of pinch diameter, and back return of the plasma exploding from the pinch. All these observed phenomena can be evolved by spontaneous self-generation and transformation of the axial magnetic field in the pinch during the plasma implosion and explosion. A configuration of axial and azimuthal magnetic field confines the plasma and later transforms or dissipates during a few tens or hundreds ns. A fast transformation of internal magnetic fields can induce a sufficiently high electric field for generation of keV particles and radiation.

Laser diagnostics of the plasma in the S-300 pulsed power generator

The second harmonic (SH) YAG:Nd laser diagnostic setup has been described. Pulses of the electro-optic Q-switch TEM00 YAG:Nd master oscillator have been compressed in CCl4 cell in the course of SBS. After amplification, the Stokes pulse passed a train of the SH generators with nonlinear crystals, deflectors of the SH beams, optic delay lines for SH beams and YAG:Nd amplifiers. Thus laser diagnostic setup produced five beams with the wavelength of 532 nm, energy of 3-5 mJ, pulse duration of 0.3ns and intervals between the pulses 10ns. Series of shadow photographs of plasmas of different wire arrays have been obtained. Causes of image formation have been discussed. The magnitude of the plasma density has been estimated. Velocities of the imploding plasma have been measured.

Experiments aimed at the “Baikal” program

On the S-300 pulsed power generator (4.5 MA, 70 ns, 0.15 Ohm), within the frames of ICF program based on fast high-current Z-pinches, experiments are being carried out studying promising schemes of output units. In particular, a nanosecond-range plasma flow switch is being investigated aimed at sharpening the pulse. As a result, the switching rate as high as 2.5 MA / 2.5 ns has been achieved. The numerical simulation of such a device has been carried out. The results of experiments on the extrinsic magnetic field influence on high-impedance plasma opening switch (POS) operation are reported. It has been demonstrated that the POS output voltage could be increased by the factor of 1.5 compared to the POS free of an extrinsic field. Also the possibility of the expansion of POS conduction phase duration up to 40 µs has been presented. The development of more new laser and nuclear diagnostic methods will definitely contribute to attain new data which could help in understanding the POS operation physics.

Concept of the high-energy photon emission from the wire array Z-pinch

Z-pinches are the laboratory sources of x-rays offering a large variety of diverse applications. As a discharge load, the liners and the fibers are often used.