Confinement studies on a plasma generated by CO₂laser irradiation of dislocated D₂pellets within the CLEO stellarator

Abstract

A highly ionised deuterium plasma having an energy content of >or approximately=370 J has been produced in the CLEO stellarator, using a single CO2 laser pulse of approximately 2 mu s duration. The free-falling deuterium target contained typically 5*1018 atoms and was intercepted with a reliability of approximately 40% at. fields of 1.3 T. (At zero field the intercept rate approached 99%.) The subsequent trapping efficiency was shown to increase with rotational transform t, reaching approximately 50% for t>0.6. The energy and particle confinement times of the trapped plasma were both approximately 0.6-1.4 ms. This containment is several orders of magnitude less than the neoclassical value and approximately 1/5 of that in subsequent ohmically-heated afterglow and microwave-heating experiments. (The latter, however, produced rather higher temperatures than the peak value of Te approximately 28 eV observed here.) The rapid energy loss is attributed to charge exchange on a localised neutral background having a measured density of <or approximately=5*1016 m-3 (corresponding to <1% of the injected pellet inventory). Means for reducing the charge-exchange losses and wall recycling in subsequent work are suggested.

Construction and vacuum-magnetic-surface measurement of modular-coil torsatron/heliotron device, SHATLET-M

“…In SHATLET-M experiments, plasma is produced by high-power CO2 laser light which is irradiated on an isolated deutrium pellet dropped almost freely from above. This is an attractive technique for producing currentless plasma independently of the magnetic field strength (SATO et al, 1977;BRAUMHACKER et al, 1980;WALKER et al, 1981 ; SAITO et al, 1981).…”