[en] We describe an apparatus for producing a magnetized column of nonneutral electron plasma which is many Debye lengths in radius. The plasma exhibits the linear and nonlinear electron-wave effects observed in neutralized plasmas

[en] The difference in the operation of extraction geometry versus radial geometry Applied-B ion diodes is explained through the use of a general magnetic insulation condition for cylindrically symmetric ion diodes which is expressed in terms of the magnetic stream function. We find that Applied-B extraction geometries attempted so far have suffered from a magnetic field configuration defect which explains their rather poor performance. We present solutions to the extraction Applied-B ion diode problem, as well as 2D, electromagnetic particle-in-cell simulations of an example solution

[en] Abstract only

[en] A serious problem for RF guns with thermionic guns is the back-bombardment effect, which makes the operation of the RF guns unstable owing to the instability of the cathode temperature. To find out how to solve the problem, we tried to evaluate the effect of back-bombardment. We have measured the temperature of cathode surface by an infrared radiation thermometer during the generation of electron beams from our S-band thermionic RF gun with 4.5 cavities. As a consequence, it was found that the temperature of cathode surface increased about 15 deg. C while the beam was on. This implies that current density on cathode surface tends to be unstable because the back-streaming electrons give energy to the cathode. We calculated the amount of the energy transfer by means of an energy-balance equation of thermal transport. Then we compared the result with the total energy of back-streaming electrons calculated by a 2-D particle simulation code KUBLAI. By comparison of two results, we could roughly estimate the energy transfer from the back-streaming electrons within experimental error

[en] A model of a plasma ion source has been developed that approximates the system of Poisson and Boltzman-Vlasov equations normally used to describe ion sources by an external electric field, a collective electric field due to the charge column, and the starting boundary conditions. The equations of this model can be used directly in the Lorentz force equation to calculate trajectories without iteration

[en] As the plasma sources of the plasma injection type pulsed ion diodes, a set of flash-boards are operated to improve the characteristics. The produced plasma flows are measured with a biased ion collector. The main experimental results obtained here are as follows. There is an optimum gap length of the flash-boards to get maximum flux of the produced plasma, though the effect is not so remarkable. To obtain the better characteristics of the boards, it is effective to apply the voltage pulse with the shorter rise time and to use separate capacitors which can fix the respective electrode potential at the ground level. The plasma flux is increased with the capacitance of the source capacitor in the driver circuit, and also with the charged voltage. On the contrary, the capacitance of the peaking capacitor affects weakly the plasma flux

[en] Steady state MHD flows in coaxial channels, namely, nozzles with a plasma injection through a ring slot, are considered. The global characteristics of the flows are studied for different slot positions. It is shown that a deviation of the magnetic field profile in the slot from that corresponding to the dependence ∼1/r does not change the geometrical parameters of the jet. The results obtained can be useful for the development of two-section quasisteady plasma accelerators (QSPA)

[en] Electromagnetic PIC simulations of a B_r magnetically insulated ion diode in an extraction geometry have been performed to investigate time-dependent diode characteristics, ion beam transport, and beam quality. Various magnetic field geometries and electron sources have been studied so that total ion throughput may be optimized. Calculational results are compared with data from the authors ion beam experiment. Comparisons are also drawn between the simulations and magnetic insulation theory

[en] The equilibria bifurcations of the biparametric version of the classical Pierce diode, a one-dimensional plasma-filled device, are analyzed in detail. Our investigation reveals that this spatiotemporal model is not structurally stable in relation to a second control parameter, the ratio of the plasma ion density to the injected electron beam density. For the first time, we relate the existence of one-fluid chaotic regions with specific biparametric equilibria bifurcations, identifying the restricted regions in the parametric plane where they occur. We show that the system presents several biparametric scenarios involving codimension-two transcritical bifurcations. Finally, we provide the spatial profile of the stable and unstable one-fluid equilibria in order to describe their metamorphoses.

[en] The physical understanding of the ion beam enhancement and divergence in magnetically insulated ion sources, B_appl-diodes, for pulsed power generators is still lacking. The authors propose a phenomenological analytical model for the open-quotes stableclose quotes regime of operation of B_appl-diodes. The effect of rippled anode-plasma surfaces on the focusing properties of the diode is analysed. Conditions for the experimentally observed value of the micro-divergence Θ_i≅ 10-20 mrad are obtained. The effect of scattering of the electrons in the disturbed electrical fields is calculated. Its effect on the electron distribution in the magnetically insulated vacuum gap is estimated: A low level ≤1% of excitations for the open-quotes slowclose quotes and open-quotes fastclose quotes fluctuations generates enough broadening of the electron distribution. Work is in progress to incorporate the model into the computer code BFCPIC to be used in computer experiments for designing high brightness diodes. This is a useful tool in the process of optimizing B_appl-diodes for good focusing properties. The first results on the effect of moving plasma boundaries are reported