Mitigation of magneto-Rayleigh-Taylor instability growth in a triple-nozzle, neutron-producing gas-puff <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Z</mml:mi></mml:math> pinch

Abstract

The gas-puff $Z$-pinch is a well-known source of x-rays and/or neutrons, but it is highly susceptible to the magneto-Rayleigh-Taylor instability (MRTI). Approaches to MRTI mitigation include density profile tailoring, in which nozzles are added or modified to alter the acceleration trajectory, and axial pre-magnetization, in which perturbations are smoothed out via magnetic field line tension. Here, we present two-dimensional magnetohydrodynamic simulations of loads driven by an 850 kA, 160 ns driver that suggest these mitigation strategies can be additive. The initial axial magnetic field, ${B}_{z0}$, to stabilize a 2.5-cm-radius Ne gas liner imploding onto an on-axis deuterium target can be reduced from 0.7 T to 0.3 T by adding a second liner with a radius of 1.25 cm. Because MRTI mitigation tends to increasingly lower yield with higher ${B}_{z0}$, the use of a lower field is advantageous. Here, we predict a reduction in yield penalty from $&gt;100\ifmmode\times\else\texttimes\fi{}$ with the single liner to $&lt;10\ifmmode\times\else\texttimes\fi{}$ with a double liner. A premagnetized, triple nozzle gas puff could therefore be an attractive source for intense neutrons or other fusion applications.