A systematic experimental study is conducted in order to measure the density and configuration of the plasma by holographic interferometry, and the ion temperature and level of turbulence by cooperative laser scattering. The two measurements are done in various phases of the plasma, before, during, and after the filament breakup. Suprathermal scattering during the filament phase and the successive development of an ionizing wave are evidenced for the first time. The anisotropy of the neutron emission is found to exist in all regimes by the simultaneous measurement of the energy spectra in two directions. A possible explanation of the neutron emission is given. It is concluded that nonthermal processes play an essential role in the plasma focus.

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A transmission grating streaked spectrograph (SPARTUVIX) has been developed at the Centre d’Etudes de Limeil-Valenton for measuring the temporal evolution of soft-x-ray spectra in laser-produced plasmas. In this article the ideas behind the instrument are described as well as a description of the actual working diagnostic and its relevant components. This diagnostic has been used to look at the time behavior of x-ray laser emission, and a number of very interesting results have been obtained. A representative sample of these results will also be shown.

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On étudie le plasma de l'expérience Focus par la diffusion Thomson d'un faisceau laser. Pour mesurer sa température ionique pendant l'émission neutronique, on a dû réduire l'angle d'observation de la diffusion par rapport à l'onde incidente de 90° à 7°. Les spectres obtenus sont comparés aux résultats théoriques de Salpeter