Development and characterisation of self pinch and rod pinch diodes at 1.9 MEV

Summary form only given. Angelixl is a CEA flash X-ray facility witch consist of a 1.6 MV Marx generator, a 2 switches transmission line and a self magnetically pinched (SMP) diode2. In order to improve its radiographic performances, the Angelix generator has been upgraded to deliver a 1.9 MV diode peak voltage. Capacitors have been added into the Marx tank, using new insulators, and the main switch has been adapted. The geometric parameters of the SMP diode have been optimized from several flashes to produce the highest dose and the lowest spot size. This experimental campaign has shown that the factor of merits (FOM = dose/spot_size2) has been increased by 70 % for this SMP diode. Moreover, by an inversion of the Marx charge voltage polarity, a positive polarity rod pinch (RP) diode2 has been set up, replacing the SMP diode. The RP diode consists of a small diameter (less than 2 mm) cylindrical anode extending through a thin annular cathode. This diode has shown good radiographic performances at 1 to 2.3 MeV3. Its main interest is a spot size reduced to about 1 mm. Actually many flashes have been carried out in order to better understand the RP diode physics and to find the configuration delivering the best FOM. Several geometric parameters have been varied including: anode and cathode radii, rod length and position relative to the cathode, anode/cathode and power flow gaps. Different materials have been tested for the rod (W, Ta, Au, AL) with different surface conditions. More thanl rad at lm with a 1 mm spot size was obtained. Diagnostics used for theses experiments were electrical diagnostics (Bdot probes and resistive divisors), rolled edge and radiographic films (spot size), FLi dosimeters, PIN diodes, pinhole cameras and a high speed CCD camera.