Ron A. Nemirovsky

EFFECT OF NEUTRAL ATOMS ON A CAPILLARY-DISCHARGE Z PINCH

We study the effect of neutral atoms on the dynamics of a capillary discharge Z-pinch, in a regime for which a large soft-x-ray amplification has been demonstrated. We extended the commonly used one-fluid magneto-hydrodynamics (MHD) model by separating out the neutral atoms as a second fluid. Numerical calculations using this extended model yield new predictions for the dynamics of the pinch collapse, and better agreement with known measured data.

Parametric investigation of capillary discharge experiment for collisional excitation x-ray lasers

The dynamics of a capillary discharge experiment for collisional excitation x-ray laser in Ne-like Argon is investigated. Time resolved hard XUV radiation measurement (E > 80 eV) show fast rise time (approximately 5 ns) of the emitted radiation. The XUV radiation peak time, relative to the beginning of the current pulse, was measured for various initial Argon pressures and main current pulses. The measured data is in good agreement with our 1D-MHD code. XUV spectra from our fast capillary discharge indicate that high ionization stages of Ar ions are presented in the plasma (Ar6+ - Ar11+) and that the Ar ionization abundance can be controlled by the main current pulse magnitude. The measured lines intensifies as a function of the main current pulse amplitude indicates that 40 - 50 kA (t1/4 equals 51 ns) are needed for achieving maximum abundance of Ar(IX) in a 4 mm diameter Polyimid capillary with initial Ar pressure of 600 mT.

The effects of the prepulse on capillary discharge extreme ultraviolet laser

In the past few years collisionally pumped extreme ultraviolet (XUV) lasers utilizing a capillary discharge were demonstrated. An intense current pulse is applied to a gas-filled capillary, inducing magnetic collapse (Z pinch) and formation of a highly ionized plasma column. Usually, a small current pulse (prepulse) is applied to the gas in order to preionize it prior to the onset of the main current pulse. In this paper we investigate the effects of the prepulse on a capillary discharge Ne-like Ar XUV laser (46.9nm). The importance of the prepulse in achieving suitable initial conditions of the gas column and preventing instabilities during the collapse is demonstrated. Furthermore, measurements of the amplified spontaneous emission (ASE) properties (intensity and duration) in different prepulse currents revealed unexpected sensitivity. Increasing the prepulse current by a factor of 2 caused the ASE intensity to decrease by an order of magnitude and to nearly disappear. This effect is accompanied by a sl...

Neutral atoms influence on the dynamics of Z-pinch capillary discharge X-ray laser

We investigate the dynamics of Z-pinch Ar plasma using a one-dimensional magneto-hydrodynamics (MHD) code, in a regime for which a large soft-X-ray amplification has been observed and reported. While some of the models numerical results are in good agreement with the experimental data, other features are not. Achieving better agreement with the experimental data requires some major adjustments in the plasma parameters relative to their classical values (as has been reported in previous works). We attribute some of the discrepancies to the high percentage of neutral atoms in the plasma. Therefore we suggest to extend the standard MHD model, by introducing a neutral-species fluid, in addition to the charged-species fluid (ions and electrons).