Eight beams of 0.35-microm laser with pulse duration of about 1.0 ns and energy of 260 J per beam were injected into a cylindrical cavity to generate intense x-ray radiation on the Shengguang II high power laser facility. Plastic foils with a thickness in the range of about 3.0-45 microm were attached on the diagnostic hole of the cavity and ablated by the intense x-ray radiation. The radiative energy transport through plastic foils with different thicknesses has been studied experimentally. The burn-through time of the plastic foils has been obtained. For comparison, we also simulated the experimental results with Planckian and non-Planckian x-ray spectrum source, respectively. It is shown that for thick plastic foil the simulation with non-Planckian x-ray spectrum source is in good agreement with the experiment.

For indirect laser fusion, the implosion is driven by the fusion capsule-absorbed radiation energy emitted by laser-produced plasma. However, the absorbed energy could hardly be directly measured experimentally and usually would require numerical simulation. This paper puts forward a method by which the capsule-absorbed radiation energy can be inferred from the measured time-dependent radiation temperature. In the method, the capusle-absorbed radiation energy is seen as an effective radiation energy loss and should be reflected in the experimental radiation temperature. Furthermore, it is not necessary to know what materials the capsule is made of or how it is constructed.

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Institute of applied physics and computational mathematics P.0.Boz 8009, Beijing 10088, P.R.China Good radiation drive symmetry is crucial for forming "hot core" in inertid confioement fusion. In practice in hohlraum x-ray flux is asymmetrical. So it is necessary to optimize the parameters of hohlraum for forming better x-ray drive symmetry. Using 2 0 numerical code LARED-I, a series of results of asymmetrical compression are obtained with variation of length of hohlraum.In experiments on ShenGuang I1 laser facility, by x-ray imaging of the sell-emission from the compressed dense core, asymmetrical implosion is diagnosed. X-ray imaging of the distorted core of capsule provides a picture that can be compared with theoretical modeling. On the other hand, asymmetry of implosion decreases DD neutron yield. ~~2 7Temperature and Density Measurement b y using a Double P r o b e of Pseudospark Discharge Plasma JetWe have been doing research on the new type of plasma jet. Plasma jet is device that makes high temperature and hgh-density plasma flow at high speed In this research, we investigate the a p plication of pseudospark discharge (PSD) to high power plasma jet in particular. PSD is low-pressure gas discharge. Electrodes have a hole on the center axis of parallel plane electrode and cathode has cylindrical hollow cavity behind the circular hole. Characteristics of PSD are as follows. When discharge is formed by using this hollow cathode and on the condition in the lowpressure region on the left hand side of the lowest point of a Paschen's curve, discharge current becomes large because breakdown voltage is high. Moreover in this low-pressure region, since discharge dose not formed along the short discharge path but the long one, discharge path passes through the center hole from reverse side of electrodes. As a result, the points of the discharge to the cathode spread to the back surface in the hollow cathode. Due to the hollow cathode effect, discharge is kept on the glow mode at the high current discharge, resulting that damage on electrode will be small. To spout the high temperature and high-density plasma in PSD, geometric structure of electrode of PSD is modified. Due to the modification of the PSD electrodes, plasma is spouted from anode hole by the power of the Lorentz power. Characteristics of this plasma jet are as follows.Since discharge current is large, high temperature plasma is casily generable., During the discharge, strong self-magnetic field occurs at the electrode holes.Power of plasma jet is as large as that of the magnet&" dynamic (MPD) arc jet.Due to the pinch effect, density of plasma jet will be high. Device can use for long time because PSD discharge is like glow mode.In this research, electronic temperature and density of a plasma jet were measured using the double probe, which has floated in potential. The experiment used hydrogen and discharge current is about 10[kAl. On the downstream of 22(mml from the anode hole, it turns out that electronic temperature is about 20 [eV] and electron dens...

A one-dimensional model describing the radiation-driven implosion in cylindrical hohlraums is proposed in this article. For the model, the radiation flux boundary condition is composed of both the equilibrium and the nonequilibrium parts by means of the experimentally measured radiation temperature and the nonequilibrium x-ray spectra emitted from laser spots. The correctness of the model is guaranteed by a criterion, the capsule-absorbed radiation energy inferred from the hohlraum radiation theory, which is independent of any implosion simulation [Chang et al., Phys. Plasmas 11, 4286 (2004)]. In this article the model is applied to the implosion experiments performed at the Shenguang II laser facility [Zunqi et al., Chin. J. Lasers, B10, 6 (2001)], and the neutron yields are consistent with the experimental data if the hydrodynamic instability is appropriately considered.