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The energy absorption of 1-1.6 kJ gain-switched CO2 laser pulses focused by an approximately f/22 mirror to a spot of innermost diameter 300 mu m (FWHM) on 0.5 and 1 mm suspended cubes of polyethylene has been measured to be 75+or-13%. For plane targets the absorption was also encouragingly high, 71+or-10%. The relative insensitivity of refraction and other losses to pellet size (vis-a-vis previous short-pulse Nd laser experiments) are fully consistent with the ruby laser shadowgram and interferogram observations made towards the end of the 1.5 mu s CO2 pulse, which reveal dense cold material expanding almost randomly at velocities of approximately 0.5 mm mu s-1.

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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