Two-pulse injector experiments with the RIIM electron accelerator

Abstract

The RADLAC-II accelerator foilless diode injector was operated under double-pulse conditions utilizing the RIIM accelerator as the test bed [M. G. Mazarakis, D. L. Smith, R. B. Miller, R. S. Clark, D. E. Hasti, D. L. Johnson, J. W. Poukey, K. R. Prestwich, and S. L. Shope, IEEE Trans. Nucl. Sci. NS-32, 3237 (1985)]. The original RIIM accelerator pulsed-power network was modified to provide for the generation, transmission, and delivery to the foilless diode of two distinct multimegavolt pulses with variable interpulse separation from 0 to 2 ms. The foilless diode successfully produced two 10-kA current pulses with interpulse separations up to 1 μs. For larger separations, the generated plasma and an excessive neutral gas release following the first pulse prevented the diode from producing a second current pulse.

Multi-pulse electron diode development for flash radiography

“…Assuming that the pressure shock wave released from the target propagates towards the cathode with the speed of sound (~340m/sec), achieving a multi-pulse train spread in a one millisecond interval could require a minimum cathodetarget distance of 34 cm. However, estimates of reference [3] suggest a much faster pressure shock velocity of the order of 2.5x10 6 cm/sec. This number may be seriously affected by outgassing of the vacuum vessel since on those experiments a large number of plastic insulators surrounding the diode were present.…”

“…We propose a feasibility study to scientifically evaluate the idea of decoupling the anode converter from the cathode electron emitter, thus making the diode capable of producing more than one pulse. This work will be based on our vast experience in designing and fielding magnetically immersed foilles diodes [1][2][3][4][5][6][7][8][9][10] and specifically on two successful previous works we have accomplished: first, making a very small pencil-like beam in a magnetically immersed foilless diode [1,2,5]; and second, the successful demonstration of two-pulse operation of a foilles diode with the RIIM accelerator [3]. Our approach will combine the above experimentally demonstrated successful work.…”

“…We have designed and built similar diodes for our Recirculating Linear Accelerator (RLA) and a diode version for DARHT I. As mentioned above, the proposed work is based on our 20 plus years experience of magnetically immersed foilless diodes as injectors for the high energy high current pulsed power accelerators of IBEX [4], RIIM [3], and RADLAC I and RADLAC II [7] ( Figures 5-7) where the beam radius sizes were of the order of one centimeter. Additionally, small size foilless diodes were successfully installed at the front end of HERMES III and SABER [10] (Figures 1-4) for mm sizes flash x-ray radiography.…”