[en] This paper deals with computer simulation of plasma erosion opening switch (PEOS) operation in the context of short-pulse high power ion beam (HPIB) generation in microsecond store systems. The scaling of PEOS parameters and ion diode characteristics with various operating conditions was determined. The simulations showed the best PEOS characteristics for a hydrogen plasma (i.e., the lowest mass) with a high flow velocity and low density, although for some applications a plasma with A/Z > 1 may be preferable. It was shown that the efficiency of HPIB generation in the diode depends on its location relative to the PEOS, the time delay of anode plasma formation, the use of a spiral electrode in the PEOS region, and the use of an arrangement involving an ion return current bypass through the PEOS region. The optimization of the PEOS and ion diode with coaxial configurations and 100 kJ stored in the 600-kV Marx yielded a 16-percent overall efficiency HPIB generation in the diode, with a diode voltage and power of 4.2 MV and 0.42 TW, respectively

[en] The formation of H^- beams in reflex systems has been studied. The use of charge-exchange method and suppression of the background from protons accelerated from the anode made it possible to determine the concentration of H^- ions in the plasma near the cathode at the level of 0.5--2%. The H^- current density lies in the range 0.25 +- 0.15 A/cm². A significant improvement in measurement accuracy can be achieved by using a deuterated coating on the cathode and by switching to a high accelerator current density

[en] Two new methods are proposed and illustrated for spectroscopic diagnostics of nonthermal electric fields in plasmas. These methods were used to analyse H_α and H_β profiles from a Plasma Opening Switch experiment. copyright 1997 American Institute of Physics

[en] This paper is devoted to experimental studies of a short-pulse ( 80 ns ) inductive system with a coaxial plasma erosion opening switch (PEOS), operating at the 2-5 X 10/sup 10/ W level. Scalings of the PEOS and ion diode characteristics with different parameters (PEOS plasma density and velocity, PEOS electrode geometry, load impedance, type and strength of an external magnetic field) were carried out. It was seen that for the most efficient energy and power switching to the load by the PEOS, the following conditions are preferable: high velocity and low density of the plasma flow, negative polarity of the inner PEOS electrode, coincidence of the switch current and injected plasma flow directions, the absence of an external magnetic field, and the presence of an additional self-field in the PEOS region. Power enhancement of a factor of 3 and pulse shortening by a factor of 2 were obtained under optimal conditions

[en] Experimental results are reported on the production of ion beams in a ribbon ion diode 80 cm long with self-insulation and an ion beam density in the range 20--60 A/cm². The diode operates at 0.25--0.4 of z/sub v/, where z/sub v/ is the vacuum impedance, with an ion beam density which increases in the drift direction. The beginning of the production of the ion beam is correlated with the formation of a magnetized electron sheet. The ion spectrum has a bimodal structure, with a high concentration (> or approx. =30%) of carbon ions. The efficiency of the diode is (27--33)%, in agreement with theoretical predictions. The simplicity of this diode and the good reproducibility of the characteristics of the ion beams which it generates make this diode promising for use in transverse pumping of long active media

[en] Short communication

[en] An experimental study of the production of intense ion beams in a reflex triode with an external plasma source at the anode is reported. The ions had various ratios Z/M. When the anode plasma is produced in a preliminary charging pulse of the accelerator, the plasma density is too low for operation under charge-limited emission conditions. In this case, an ion beam is observed to be produced from the plasma formed by the direct heating of the anode material by oscillating electrons. When an anode plasma resulting from the breakdown of a dielectric insert or of the vacuum gap of a composite andode by an external voltage source is used to produce an ion beam, the reflex triode operating conditions depend on delaying the operation of the accelerator with respect to the external source. The highest efficiency (≅20%) in the production of an ion beam is observed at t/sub d/ = 3--6 μs. In this case, the reflex triode operates under increasing or constant impedance conditions. It was shown in the course of the experiments that the ion beam which is produced is nonuniform. There are three groups of ions: H⁺, C/sup n/⁺, and Cu/sup n/⁺. The energy of the heavy ions depends on the applied anode potential. The different mass components of the ion beam do not appear at the same time. The macroscopic divergence of the beam is 4--6⁰ at the periphery and drops off to approx. <1⁰ at the center. The microscopic divergence of the beam is 3⁰. The total energy of the ion beam which is produced is less than 120 J at an average current ≅2.8 kA

[en] Short communication

[en] The time-dependent magnetic field spatial distribution in a coaxial positive-polarity plasma opening switch (POS) carrying a current congruent 135 kA during congruent 100 ns, was investigated by two methods. In the first, ionic line emission was observed simultaneously for two polarizations to yield the Doppler and Zeeman contributions to the line profiles. In the second method, the axial velocity distribution of ions was determined, giving the magnetic field through the ion equation of motion. This method requires knowledge of the electron density, here obtained from the observed particle ionization times. To this end, a lower bound for the electron kinetic energy was determined using various line intensities and time-dependent collisional-radiative calculations. An important necessity for POS studies is the locality of all measurements in r, z, and θ. This was achieved by using laser evaporation to seed the plasma nonperturbingly with the species desired for the various measurements. The Zeeman splitting and the ion motion showed magnetic field penetration through the 3.5 cm long plasma at a velocity congruent 10⁸ cm/s. The current density was found to be relatively high at the load-side edge of the switch plasma. It is suggested that this may cause plasma acceleration into the vacuum section toward the load, which is supported by charge-collector measurements. The fast magnetic field penetration agrees with estimates based on the Hall-field mechanism. copyright 1995 American Institute of Physics

[en] Short communication