Specific features of implosion of metallized fiber arrays
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MA DYNAMICS
Specific Features of Implosion of Metallized Fiber Arrays K. N. Mitrofanov*, V. V. Aleksandrov, A. N. Gritsuk, E. V. Grabovski, I. N. Frolov, Ya. N. Laukhin, and S. S. Breshkov Troitsk Institute for Innovation and Fusion Research, Troitsk, Moscow, 142190 Russia *e-mail: [email protected] Received January 14, 2016; in final form, April 16, 2016
Abstract―Implosion of metallized fiber arrays was studied experimentally at the Angara-5-1 facility. The use of such arrays makes it possible to investigate the production and implosion dynamics of plasmas of various metals (such as tin, indium, and bismuth) that were previously unavailable for such studies. The plasma production rates m (in μg/(cm2 ns)) for different metals were determined and quantitatively compared. Varying the thickness of the metal layer deposited on kapron fibers (the total linear mass of the metal coating being maintained at the level of 220 μg/cm), the current and velocity of the plasma precursor were studied as functions of the thickness of the metal coating. The strong difference in the rates of plasma production from the metal coating and kapron fibers results in the redistribution of the discharge current between the Z-pinch and the trailing fiber plasma. The outer boundary of the plasma produced from the metal coating is found to be stable against instabilities typical of the final stage of implosion of conventional wire arrays. DOI: 10.1134/S1063780X17020106
1. INTRODUCTION Within the program of inertial confinement fusion (ICF) research, fundamental studies are being carried out at high-power electrophysical facilities. At such facilities, wire arrays are used as most promising sources of soft X-ray (SXR) emission (hν > 100 eV) required to compress ICF targets. The experiments carried out at the Z facility (Sandia Laboratory, USA) showed that the SXR power and energy of 280 TW and 1.8 MJ, respectively, can be achieved during the implosion of tungsten wire arrays at a discharge current of 18 MA [1]. After the Z facility was upgraded to the ZR facility (I = 26 MA, Δt = 100 ns), SXR pulses with a duration of 100 eV. The radial (in the middle) and axial (on the bottom) streak images (negatives) are synchronized with the above time dependences. The widths of the slits of the radial streak cameras installed at heights of H1 = 0.7 cm and Н2 = 1.2 cm above the cathode are 200 μm. The width of the slit of the axial streak camera oriented along the axis of the fiber array is 100 μm. Here, time Tn corresponds to the end of plasma production from the metal coating, time Tf corresponds to the beginning of the final compression of the metal coating plasma, time Tk corresponds to the end of fiber plasma production; and time Tn–k corresponds to the collision between the fiber and metal coating plasmas.
i.e., later than plasma production from the metal coating, which terminates at time Tn. As follows from the radial streak image, after that, the Z-pinch plasma begins to expand toward the imploding fiber plasma (time Tn–k) and, then, their combin
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