Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

Journal Article · Sat Sep 15 00:00:00 EDT 2012 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4750047· OSTI ID:22086157

Etchessahar, Bertrand; Bicrel, Beatrice; Cassany, Bruno; Desanlis, Thierry; Voisin, Luc; Hebert, David ^[1]; Bernigaud, Virgile; Magnin, Laurent; Nicolas, Remi; Poulet, Frederic; Tailleur, Yaeel ^[2]; Caron, Michel; Cartier, Frederic; Cartier, Stephanie; Hourdin, Laurent; Rosol, Rodolphe; Toury, Martial; Delbos, Christophe; Garrigues, Alain; Soleilhavoup, Isabelle ^[3] ; others, and

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1. CEA, DAM, CESTA, F-33114 Le Barp (France)
2. CEA, DAM, VALDUC, F-21120 Is sur Tille (France)
3. CEA, DAM, GRAMAT, F-46500 Gramat (France)

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.

• OSTI ID: 22086157
• Journal Information: Physics of Plasmas, Vol. 19, Issue 9; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CAPACITORS
CATHODES
CHARGE-COUPLED DEVICES
COMPUTERIZED SIMULATION
CYLINDRICAL CONFIGURATION
DOSEMETERS
ELECTRIC POTENTIAL
ELECTRONIC EQUIPMENT
OPTIMIZATION
PINCH EFFECT
PLASMA DIAGNOSTICS
RADIATION EFFECTS
RESOLUTION
STREAK CAMERAS
THERMIONIC DIODES
X-RAY EMISSION ANALYSIS
X-RAY SOURCES