[en] Poly(methyl methacrylate) sheet exposed to electron radiation at a very high dose rate (10⁹ rad/sec) under atmospheric pressure using a 300 KV electron accelerator resulted in main chain scission, side chain cleavage, reduction in material strength, yellow color formation, micro fracturing, production of white bubbles upon heating, and increased solubility in special solvent developers. In general the decrease in number average and weight average molecular weight of PMMA is linear with the logarithm of electron radiation dose. A significant increase in heterogeneity and a bimodal distribution of molecular weight where detected when PMMA was electron irradiated above 40 Mrads. The chain scission efficiency (G-value) of PMMA was determined to be 0.46 breaks/100 eV

[en] A novel advanced accelerator is proposed. The counterstreaming electron beam accelerator relies on the same physical mechanism as that of the plasma accelerator but replaces the stationary plasma in the plasma accelerator with as magnetized relativistic electron beam, drifting antiparallel to the driving source and the driven particles, as the wave supporting medium. The plasma wave in a counterstreaming electron beam can be excited either by a density-ramped driving electron beam or by properly beating two laser beams. The fundamental advantages of the counterstreaming electron beam accelerator over the plasma accelerator are a loner and tunable plasma wavelength, a longer pump depleting length or a larger transformer ratio, and easier pulse shaping for the driving source and the driven beam. Therefore, the energy gain of the driven particles can be greatly enhanced whereas the trapping threshold can be dramatically reduced, thus admitting the possibility for proton acceleration

[en] In the University of Maryland electron beam transport experiment, a 5 kV, 0.2 A electron beam from a thermionic electron source (cathode radius r_c=1.27 cm and cathode temperature kT=0.12 eV) is injected into a periodic focusing channel consisting of 38 solenoid lenses with period length S=13.6 cm. The magnetic focusing fields of the channel, and hence the phase advance without space charge, can be varied over a wide range. We report emittance measurements and results of the effects of beam mismatch, misalignments and nonlinear lens forces on beam transpfort and emittance growth. (orig.)

[en] The authors describe a simple self-breaking 2 MV gas master switch for a 2 MV general purpose relativistic electron beam (REB) accelerator. The switch cavity has been hollowed out in a 17.8 cm-thick acrylic slab. The switch gap is 3.55 cm. At 2 MV the maximum field at the cathode is 740 kV cm^-1 and the maximum envelope field is 172 kV cm^-1. The maximum measured switching voltage is 1.90 +-0.1 MV (10 bar abs). The minimum switching voltage is 1.1 mV (4.3 bar abs). The operating characteristics break away from the 89 kV/(cm atm) DC breakdown strength of SF₆ at 5.5 bar abs. The authors discuss how the electrical and mechanical design as well as quality control during assembly and operation have resulted in reliable and reproducible operation

[en] The authors conducted plasma opening switch (POS) experiments on Sandia National Laboratories' new Particle Beam Fusin Accelerator II (PBFA II) (12 MV, 100 TW, 50 ns), on the Supermite accelerator (2 MV, 2 TW, 50 ns) and on the Naval Research Laboratory's Gamble II accelerator (1.8 MV, 1.6 TW, 70 ns). The POS systems on the PBFA II and Supermite accelerators use a newly developed flashboard plasma source to provide the plasma necessary to conduct the large (> 1 MA) currents produced byu these accelerators. In the Supermite experiments, the plasma opening switch conducted currents up to 1 MA before opening in less than 10 ns into an electron beam load. These experiments achieved significant voltage gain relative to the voltage across a matched load. In experiments on Gamble II, power gains of up to 1.7 were achieved using a POS in a strongly coaxial geometry (r/sub outer//r/sub inner/ = 2) with a large magnetic field at the cathode. The POS system on PBFA II is unique because of its size and voltage. This POS system is designed to conduct over 6 MA before opening. In present experiments it has conducted currents of 4-5 MA for over 50 ns

[en] The paper summarizes the progress registered in the field of inertial confinement fusion, as derived from the works of the 10th International Conference on Plasma Physics and Controlled Nuclear Fusion Research (London, 1985)

[en] The RADLAC-II accelerator foilless diode injector was operated under double-pulse conditions utilizing the RIIM accelerator as the test bed [M. G. Mazarakis, D. L. Smith, R. B. Miller, R. S. Clark, D. E. Hasti, D. L. Johnson, J. W. Poukey, K. R. Prestwich, and S. L. Shope, IEEE Trans. Nucl. Sci. NS-32, 3237 (1985)]. The original RIIM accelerator pulsed-power network was modified to provide for the generation, transmission, and delivery to the foilless diode of two distinct multimegavolt pulses with variable interpulse separation from 0 to 2 ms. The foilless diode successfully produced two 10-kA current pulses with interpulse separations up to 1 μs. For larger separations, the generated plasma and an excessive neutral gas release following the first pulse prevented the diode from producing a second current pulse

[en] The relativistic electron beam fusion accelerator is capable of delivering up to 5 x 10⁵ joules in a single 4 x 10¹³ watt peak power pulse (which will provide a factor of 25 times more power than any e-beam accelerator at a similar voltage now in existence) and will be used in the expanded electron beam research program directed at achieving significant thermonuclear yields by heating and compressing deutetium-tritium fuel. The direct radiation is mostly attenuated by the self-shielding design of the machine and the shield adequately stops all radiation, direct and sky shine. The operational health physics problems will include 1) induced reactions from 10¹⁴ 14 Mev neutrons in the machine components, shielding materials, and air; 2) the problems related to a possible tritium release in the loading of the target pellets; 3) electron beam exposure; and 4) unloading, and cleanup of the machine

[en] Four monitoring techniques that can determine peak voltage (V_p) to a precision of ∼5% for high-intensity, pulsed electron accelerators operating in the 10 to 20 MV range are discussed and applied to the 14-TW HERMES III accelerator. The techniques utilize parapotential flow theory, the range of H^- ions, the bremsstrahlung from electron interactions with an electron target, and the photoneutron fluence from neutrons generated in a bremsstrahlung target. Application of these techniques to HERMES III shows that when the accelerator is operating under nominal conditions, V_p=(18.7±0.7) MV

[en] Experimental data on filamentation of high-current relativistic electron beam in Kalmar-1 generator of relativistic electron beam (REB) are presented and possible mechanism of this phenomenon is considered theoretically. It is shown that experimentally observed multiplicity of REB division into filaments may be explained by current azimuth heterogeneit y, occurring in the cathodic plasma due to Rayleigh-Taylor electron instability