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The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., “Considerations of rod-pinch diode operation in negative polarity for radiography,” in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975–978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., “Theoretical modeling and experimental characterization of a rod-pinch diode,” Phys. Plasmas 8(10), 4618–4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., “Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,” IEEE Trans. Plasma Sci. 32(5), 2004–2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567–570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., “Negative polarity rod pinch diode experiments on the ASTERIX generator,” in Conference Records–Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most comprehensive characterization of the diode, both optical and x-ray diagnostics were used, including high speed multi-image ICCD (intensified CCD) cameras, streak camera, dosimeters, spot size measurements, and pinhole cameras. A set of new results have been obtained through this study. The plasma emission from the anode and cathode surfaces and its expansion appear to be critical for the diode functioning. Also, for the first time, potential sources of diode instability were identified. Finally, an optimal and stable diode configuration was found with the following parameters: 52 rad at 1 m (in Al) and 2.2 mm spot size.

During the interaction of a high-intensity picosecond laser pulse with a plasma, a large amount of relativistic electrons are accelerated. If these electrons interact with a high-Z solid target, Bremsstrahlung photons are generated. This multi-MeV x-ray source may be used in various applications including radiography and photonuclear studies. The characteristics of such sources, produced with a petawatt laser interacting with different targets, are investigated numerically, using laser-plasma interaction and transport codes to model the relativistic electron acceleration and their transport in the conversion target, respectively. If the laser pulse interacts with a preplasma in front of a solid target, the on-axis dose first increases with preplasma scale-length, but then saturates and fluctuates, due to strong filamentation of the petawatt pulse. In an ionized gas jet, laser hosing reduces the electron emission along the propagation direction and thus the dose. For a capillary tube filled with plasma, th...

The selective heating near the ion cyclotron resonance (ICR) in order to separate isotopes by the plasma separation process is investigated both experimentally and theoretically on the ERIC device. The electromagnetic field induced by a half‐turn heliocoidal antenna is calculated for a uniform hot and collisional plasma. The axial wave number kz spectrum of the rotating electric field E+ exhibit the presence of two waves which characteristics determine the heating. The motion equation of the ions is resolved in the approximation of the guiding center hypothesis, so that the final heating can be directly obtained; also the comparison with the experiment is satisfactory.

When high intensity (≥1019 W cm−2) laser light interacts with matter, multi-MeV electrons are produced. These electrons can be utilized to generate a MeV bremsstrahlung x-ray emission spectrum as they propagate into a high-Z solid target positioned behind the interaction area. The short duration (

Electron Cyclotron Resonance plasma heating as well as Ion Cyclotron Resonance are successfully applied on the ERIC stable isotope separation device, in operation at CEN‐Saclay. In this experiment, the plasma is created in the flaring magnetic field zone of a superconducting coil by ionizing the vapour issued from a sputtering plate (or a Joule oven), by electron cyclotron heating using 10, 18 or 29 GHz, 1.5 kW klystrons. A three‐fluid model has been developed in order to describe the plasma source. In a first step, the values of the absorbed HF power, appearing in the equation of electrons energy conservation have to be determined. For this purpose, a ray tracing model is used. The preliminary results of the calculation are presented in this paper. The electron distribution function is assumed to be Maxwellian. The temperature effects are taken into account in the dielectric tensor. The polarization is also determined at any point of the wave propagation in the plasma.

Laser blow-off impurity injection in PLT yields conspicuous modifications of the soft and ultrasoft X-ray signals. the 2 omega CE signal giving temperature fluctuations is unaffected. A transport code is used to deduce transport coefficient as functions of time and radius. The significance of the results for MHD behaviour is discussed.

Experimental absolute and relative line radiances of heavy impurities in the X-ray and VUV regions of the spectrum from low-density TFR plasmas are interpreted in terms of ionisation, recombination and diffusion. The authors conclude that it is necessary to use as adjustable parameters both diffusion terms and atomic rate coefficients (namely, the S/ alpha ratios). Fractional abundance curves have been calculated using the adjusted S/ alpha ratios for iron, and compared with theoretical IE calculations.

A collisional-radiative model constituted by statistical equilibrium equations has been built up, the considered atomic levels of U I and U II being coupled by the elementary processes; while the electronic temperature Te and density ne are fixed with Te or=1010 cm-3. It is assumed that the plasma is stationary, optically thin and that the electrons are Maxwellian. Absolute oscillator strengths of U I and U II transitions are derived using the published radiative lifetimes and branching ratio values obtained mainly by the laser induced fluorescence (LIF) method. It is found that the previously published U II gf values are underestimated by a mean factor of 2.8. The results derived by the model against Te and ne are the relative populations of the U I and U II fundamental and metastable levels, the relative densities of the atomic and ionic species U I, U II and U III, the excitation temperatures of U I and U II and the radiative power loss.