A strong magnetic field of 600 kG (60 T) is generated at the center of a 2-mm-diam one-turn coil in which the current is driven by a C0 2 laser. The magnetic field, current, and voltage are measured as functions of the separation distance of the gap where the high voltage is induced by the laser irradiation in the coil loop at a fixed intensity of 1.3 x 10 14 W/cm 2 . These results are analyzed on the basis of hot-electron Ex B drift and plasma expansion inside the gap. The analysis indicates how to design the target and the laser pulse for generation of a magnetic field of a few megagauss.
By combining the benefits of magnetic and inertial fusion, a new fusion scheme is proposed. A plasma with a density of ≳1021 cm−3 is confined by the inertia of a heavy, cannonball-type metallic shell; its heat is insulated by a self-generated magnetic field of ≳100 T. The plasma and the magnetic field are produced by ablation due to direct impact of a laser (or particle) beam on solid fuel which constitutes the coating of the inner surface of the spherical metallic shell. Preliminary experimental and simulation results, using a 100 J CO2 laser on a target of a few millimetre parylene shell, gave nτ ≅ 5 · 1012 cm−3·S, with T ≅ 500 eV. A 1-D spherical hydrodynamic code, HISHO, with the radial heat conductivity reduced by an assumed magnetic field of 103 T, leads to ignition at an absorbed energy of the order of 20 MJ deposited during a confinement time of approximately 100 ns. These results provide supporting evidence for the feasibility of the scheme as a realistic reactor.
Lateral transport of hot electrons on a spherical target irradiated with two beams of CO2 laser (4.8×1014 W/cm2) is studied by spatially resolved Kα x-ray measurements. The hot-electron energy and spatial distribution in the target are found to depend on the method of irradiation: tight and overlapped focusing conditions.
A method is presented for generating a high magnetic field using a CO2 laser pulse. The magnetic field, current and voltage in a one-turn coil were measured as functions of the gap width, where the high voltage was induced by laser irradiation at a fixed intensity of 1.3 × 1014 W/cm2. These results could be explained on the basis of lateral transport by hot-electron E × B motion and an expansion of the critical density plasma in the gap. The maximum magnetic fields are determined and limited by the filling time of the gap with a critical-density plasma. In order to obtain higher magnetic fields, we tested a cylinder-type one-turn coil attached to the optimized gap. The highest magnetic field observed was 400 T.
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