Multiple reflections of electrons and the possibility of intense positive-ion flow in high ν/γ diodes

Prono, D. S.; Creedon, J.; Smith, I.; Bergstrom, N.

doi:10.1063/1.322056

Cited by 53 publications

(14 citation statements)

References 24 publications

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“…For injection into vacuum Torr) and low pressure hydrogen gas with an applied magnetic field our results indicate that the beam electrons undergo multiple reflections through the anode foil while the beam space charge remains unneutralised. This reflexing process shows up as a severe modification to the normal diode voltage traces (Prono et a1 1975). We observe similar changes when monitoring the applied voltage in these experiments (Kerslick 1982).…”

Section: Discussion Of Resultssupporting

confidence: 75%

Observations of ion acceleration by a relativistic electron beam

Kerslick

Dymoke‐Bradshaw

Dangor

1983

J. Phys. D: Appl. Phys.

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Experimental evidence is presented for the collective acceleration of ions by a 350 keV, 50 kA, 100 ns electron beam. Accelerated ions are observed for vacuum injection, and at hydrogen fill-pressures below 50 m Torr. Measurements with different anode foils indicate that thicker foils reduce the number of ions accelerated. An applied magnetic field is found to increase the energy spread of the ions while leaving the total number accelerated unchanged. The total number of ions accelerated is approximately 1012, with peak currents of 7 A.

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Section: Discussion Of Resultssupporting

confidence: 75%

Observations of ion acceleration by a relativistic electron beam

Kerslick

Dymoke‐Bradshaw

Dangor

1983

J. Phys. D: Appl. Phys.

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“…With thinner, lower-mass shells, net energy gain would occur at lower energy and power levels, and higher voltage [26] could be used. Reduction in electron penetration depth and/or enhancement of specific power deposited could occur because of magnetic stopping [27][28][29][30]; return-current heating [31 ]; scattering from micro-magnetic turbulence [32]; electrostatic reflexing [33][34][35]; beam stagnation [36]; or slowing-down processes [37][38][39] at the elevated temperatures and reduced densities expected in the ablator, which differ from those associated with cold, neutral matter. Experiments performed so far have, however, demonstrated enhanced deposition only in low-density regimes similar to those existing in exploding-pusher targets and not in ablatively-driven electron targets.…”

Section: Discussion Of Deposition Physicsmentioning

confidence: 99%

High-gain, low-intensity ICF targets for a charged-particle beam fusion driver

Sweeney¹,

Farnsworth²

1981

Nucl. Fusion

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A class of high-gain ICF targets driven by electrons or light ions is discussed. The targets are characterized by a low-beam-intensity requirement and large size. A magnetic field provides thermal insulation of pre-heated, low-density fuel. The addition of a cryogenic fuel layer increases the gain without requiring significantly increased beam power and intensity. The higher fuel adiabat and reduced fuel losses produce ignition and burn for lower implosion velocities and at lower power and intensity than conventional ablative designs. Gains of 20 to 40 are expected for intensities of ⪅ 80 TW·cm−2, initial magnetic fields of ⪆ 30–60 kG, an initial fuel radius of 0.2–0.4 cm, and irradiation uniformities of 6–7%. Driver requirements are ⪅ 45 TW·cm−2 if the initial magnetic field is ⪆ 300–600 kG, sufficient for alpha trapping in the compressed low-density fuel. Voltage shaping increases fuel burn-up and target ρr and lowers power and intensity levels by an additional factor of about 0.6.

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“…This puts an extraordinary demand on the ion source and although present-day ion diodes and pulsed-power machines (see, e.g. Refs [18][19][20]) are capable of providing this amount of ion charge per pulse, particular care must be exercised to optimize the injection ' efficiency. Employing a 1-TW pulsed-power machine, GAMBLE II, at the Naval Research Laboratory, Kapetanakos et al [21 ] were successful in creating a transient (~ 30 ns) field reversal by injecting a pulse of ions through a magnetic cusp.…”

Section: Introduction 1historical Introductionmentioning

confidence: 99%

Field-reversed configurations with a component of energetic particles

Finn¹,

Sudan²

1982

Nucl. Fusion

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This review is concerned with the physics of field-reversed configurations created by energetic particles of large orbits, of which the earliest example is the Astron. The Astron concept has evolved into the Ion Ring Compressor in which a low-energy ring of ions is magnetically compressed to high energy for heating the confined plasma to thermonuclear ignition. A third version is the hybrid in which field reversal is created both by plasma currents as in a θ-pinch or a spheromak and a component of energetic large orbit ions to provide heating energy as well as improved stability. This paper treats first the injection, trapping, and formation of electron and ion rings from a theoretical standpoint as well as presenting the principal experimental results. The equilibria and the characteristics of the particle orbits are discussed in some detail including conditions under which the orbits cease to be integrable and pass to a stochastic description. The theory of magnetic compression of rings and the classical transport of heat and particles of the plasma confined in the closed-poloidal-field-line region is presented. The bulk of the review is concerned with low-frequency stability of such configurations by means of a generalized energy principle for treating the large-orbit particles in the Vlasov limit. The pathology of all possible unstable modes is discussed at some length. We conclude with an exhaustive survey of microinstabilities driven by the energetic particle current for a special model and conclude that most of them are stabilized by strong gradients in density and magnetic field. A brief discussion on drift modes follows. Our present theoretical understanding of these systems, although still incomplete in some respects, nevertheless leads to the view that the promise of the very favourable features of fusion reactors based on these concepts is a sufficient impetus for their continued experimental and theoretical study.

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Multiple reflections of electrons and the possibility of intense positive-ion flow in high ν/γ diodes

Cited by 53 publications

References 24 publications

Observations of ion acceleration by a relativistic electron beam

Observations of ion acceleration by a relativistic electron beam

High-gain, low-intensity ICF targets for a charged-particle beam fusion driver

Field-reversed configurations with a component of energetic particles

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