Mixed double planar wire arrays on Michigan's Ltd generator
Résumé
Double Planar Wire Arrays (DPWA), which consist of two parallel rows of wires, have previously demonstrated high radiation efficiency, compact size, and usefulness for various applications in experiments on a University-scale high-impedance Z-pinch generator1. Recently, we successfully performed two experimental campaigns with PWAs on the University of Michigan's low-impedance MAIZE (Linear Transformer Driver (LTD)-driven generator, 0.1ohm, 0.5-1 MA, 100-180 ns) in collaboration with the UM team. The details and the analysis of the results of the first experimental campaign can be found in Ref. [2]. The second experimental campaign was focused on studying the implosion and radiative characteristics of DPWAs using a diagnostic set similar to the first campaign, including: filtered X-ray diodes, X-ray spectrographs and pinhole cameras, and a new four-frame shadowgraphy system with 2-ns, 532 nm frequency doubled Nd:YAG laser. Here we present the results of four, mixed-DPWA shots with the load consisting of one plane with 6 Al wires of 10¿¿m diameter and another plane of 6 stainless steel wires of 5.1 ¿¿m diameter. The rise-time of the current varies between 175 and 225 ns and shadowgraphy images cover the broad span of time from as early as 116 ns to as late as 304 ns. The shadowgraphy images show ablating and imploding mixed DPWAs that are very different from the images of uniform DPWAs. There is a clearly observed asymmetry of implosions of two wire array planes dependent on the material of each plane, (early time images in particular), captured also by X-ray pinhole images. WADM is used for the analysis of shadowgraphy images. X-ray spectra display both K-shell Al and L-shell Fe features analyzed with non-LTE modeling. Advantages of using mixed wire arrays are discussed. [1] V. L. Kantsyrev et al, Phys. Plasmas 15, 030704 (2008). [2] A.S. Safronova, V.L. Kantsyrev, M.E. Weller, V.V. Shlyaptseva, I.K. Shrestha, M. Lorance, M. Schmidt-Petersen, A. Stafford. M. Cooper, A.M. Steiner, D.A. Yager-Elorriaga, S.G. Patel, N.M. Jordan, R.M. Gilgenbach, A.S. Chuvatin, IEEE TPS, Special Issue on Plenary and Invited papers from ICOPS 2015, to be published, April 2016. * This work was supported by NNSA under DOE Cooperative Agreement DE-NA0001984.