At the GOL-3 facility, experiments on the interaction of powerful hot electron streams with various materials have been performed. For energy densities of the hot electron stream above 10 MJ/m2 an explosive-like erosion was observed, which at energy densities of 30 MJ/m2 reaches 500 mu m for fine grain graphite and 200 mu m for tungsten. Under these conditions, the corona of the carbon vapour cloud has temperatures below 1.2 eV and densities up to 1017 cm-3. It propagates along the magnetic field lines with maximum velocities of 2.1*106 cm/s. The longitudinal and transverse (along and across magnetic field lines) vapour velocities of the colder bulk plasma are about 106 cm/s. A model for explosive-like erosion was developed and tested against the GOL-3 results. For graphite the destruction threshold is 10 kJ/g. This value is considerably lower than the vaporization enthalpy of 20.5 kJ/g for three atomic vaporization. The validated model was applied to a numerical analysis of the occurrence of explosive-like erosion for ITER disruptions and runaway electrons. If the energy density of the runaways remains below 30 MJ/m2, explosive-like erosion of graphite occurs for electron energies below 20 MeV. For the energetic tail of Maxwellian plasma electrons with temperatures up to 20 keV and power densities of 10 MW/cm2 without any angular spread, explosive-like erasion becomes comparable to erosion by vaporization

The authors consider the possibility of a self-sustaining thermonuclear reaction in a dense plasma (n ≳ 1016 cm3). The pressure of the plasma is contained by walls and the magnetic field only serves to reduce thermal conductivity in a transverse direction. A solution is obtained for the plasma balance equation that makes allowance for radiation losses along the magnetic field, and it is shown that there is no satisfactory solution across a uniform magnetic field. The authors discuss the possibility of a steady-state thermonuclear reaction with a non-uniform magnetic field.

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The longitudinal confinement of a plasma in a pulsed multi-mirror fusion reactor is investigated. It is shown that the initial plasma energy W p per unit of reactor cross-section and the initial plasma temperature T o serve as similarity parameters. One-dimensional numerical calculations of plasma flow along the reactor axis were performed for various W p and T o and were used to determine the plasma gain function QE(W P , T o ). The region of maximum values of QE lies near T o = 5 keV for all W p . Plasma heating by a-particles becomes substantial for values of Q exceeding unity. At W p = 20 MJcm" 2 , QE calculated with plasma heating by a-particles exceeds QE as calculated without including such heating by a factor of five. If the mirror ratio is increased by enlarging the cross-section towards the reactor ends, Q is further increased by a factor of two. A value of QE = 1 is achieved at an initial plasma energy of W p « 5 MJ-cm" 2 , and QE = 10 is achieved for W p «12MJ-cm" 2 .

Strong radial forces are experienced by the particle beam that drives the wakefield in plasma-based accelerators. These forces may destroy the beam although, under proper arrangements, they can also keep it in radial equilibrium which allows the beam to maintain the wakefield over a large distance and to provide high energy gain for the accelerated particles. This paper demonstrates the existence of acceptable equilibria for the prebunched beams and addresses the issue of optimum bunch spacing, with implications for forthcoming experiments.