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Title: Ion-Kinetic-Energy Measurements and Energy Balance in a Z-Pinch Plasma at Stagnation

Abstract

The ion-kinetic energy throughout K emission in a stagnating plasma was determined from the Doppler contribution to the shapes of optically thin lines. X-ray spectroscopy with a remarkably high spectral resolution, together with simultaneous imaging along the pinch, was employed. Over the emission period, a drop of the ion-kinetic energy down to the electron thermal energy was seen. Axially resolved time-dependent electron-density measurements and absolute intensities of line and continuum allowed for investigating, for the first time, each segment of the pinch, the balance between the ion-kinetic energy at the stagnating plasma, and the total radiation emitted. Within the experimental uncertainties, the ion-kinetic energy is shown to account for the total radiation.

Authors:
; ; ; ; ; ; ; ; ;  [1];  [2];  [3];  [4]
  1. Weizmann Institute of Science, Rehovot 76100 (Israel)
  2. (Germany)
  3. (Israel)
  4. (United States)
Publication Date:
OSTI Identifier:
20957753
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 11; Other Information: DOI: 10.1103/PhysRevLett.98.115001; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ELECTRON DENSITY; ELECTRON EMISSION; ELECTRONS; ENERGY BALANCE; IONS; KINETIC ENERGY; LINEAR Z PINCH DEVICES; PLASMA; RESOLUTION; TIME DEPENDENCE; X-RAY SPECTROSCOPY

Citation Formats

Kroupp, E., Osin, D., Starobinets, A., Fisher, V., Bernshtam, V., Maron, Y., Uschmann, I., Foerster, E., Fisher, A., Deeney, C., Friedrich-Schiller University, Jena, Faculty of Physics, Technion-Israeli Institute of Technology, Haifa, and Sandia National Laboratories, Albuquerque, New Mexico. Ion-Kinetic-Energy Measurements and Energy Balance in a Z-Pinch Plasma at Stagnation. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.115001.
Kroupp, E., Osin, D., Starobinets, A., Fisher, V., Bernshtam, V., Maron, Y., Uschmann, I., Foerster, E., Fisher, A., Deeney, C., Friedrich-Schiller University, Jena, Faculty of Physics, Technion-Israeli Institute of Technology, Haifa, & Sandia National Laboratories, Albuquerque, New Mexico. Ion-Kinetic-Energy Measurements and Energy Balance in a Z-Pinch Plasma at Stagnation. United States. doi:10.1103/PHYSREVLETT.98.115001.
Kroupp, E., Osin, D., Starobinets, A., Fisher, V., Bernshtam, V., Maron, Y., Uschmann, I., Foerster, E., Fisher, A., Deeney, C., Friedrich-Schiller University, Jena, Faculty of Physics, Technion-Israeli Institute of Technology, Haifa, and Sandia National Laboratories, Albuquerque, New Mexico. Fri . "Ion-Kinetic-Energy Measurements and Energy Balance in a Z-Pinch Plasma at Stagnation". United States. doi:10.1103/PHYSREVLETT.98.115001.
@article{osti_20957753,
title = {Ion-Kinetic-Energy Measurements and Energy Balance in a Z-Pinch Plasma at Stagnation},
author = {Kroupp, E. and Osin, D. and Starobinets, A. and Fisher, V. and Bernshtam, V. and Maron, Y. and Uschmann, I. and Foerster, E. and Fisher, A. and Deeney, C. and Friedrich-Schiller University, Jena and Faculty of Physics, Technion-Israeli Institute of Technology, Haifa and Sandia National Laboratories, Albuquerque, New Mexico},
abstractNote = {The ion-kinetic energy throughout K emission in a stagnating plasma was determined from the Doppler contribution to the shapes of optically thin lines. X-ray spectroscopy with a remarkably high spectral resolution, together with simultaneous imaging along the pinch, was employed. Over the emission period, a drop of the ion-kinetic energy down to the electron thermal energy was seen. Axially resolved time-dependent electron-density measurements and absolute intensities of line and continuum allowed for investigating, for the first time, each segment of the pinch, the balance between the ion-kinetic energy at the stagnating plasma, and the total radiation emitted. Within the experimental uncertainties, the ion-kinetic energy is shown to account for the total radiation.},
doi = {10.1103/PHYSREVLETT.98.115001},
journal = {Physical Review Letters},
number = 11,
volume = 98,
place = {United States},
year = {Fri Mar 16 00:00:00 EDT 2007},
month = {Fri Mar 16 00:00:00 EDT 2007}
}
  • The time history of the local ion kinetic energy in a stagnating plasma was determined from Doppler-dominated line shapes. Using independent determination of the plasma properties for the same plasma region, the data allowed for inferring the time-dependent ion temperature, and for discriminating the temperature from the total ion kinetic energy. It is found that throughout most of the stagnation period the ion thermal energy constitutes a small fraction of the total ion kinetic energy; the latter is dominated by hydrodynamic motion. Both the ion hydrodynamic and thermal energies are observed to decrease to the electron thermal energy by themore » end of the stagnation period. It is confirmed that the total ion kinetic energy available at the stagnating plasma and the total radiation emitted are in balance, as obtained in our previous experiment. The dissipation time of the hydrodynamic energy thus appears to determine the duration (and power) of the K emission.« less
  • In order to benchmark and improve current 2D radiation magnetohydrodynamic (MHD) models of Z-pinch plasmas, we have performed experiments which characterize the plasma conditions at stagnation. In the experiments the SATURN pulsed power facility at Sandia National Laboratory was used to create an imploding Ar-Ne plasma. An absolutely calibrated, high resolution space- and time-resolving Johann crystal spectrometer was used to infer the electron temperature T{sub e} from the slope of the hydrogenlike Ne free-bound continuum, and the ion density n{sub i} from the Stark broadening of the Ar heliumlike Rydberg series. 2D electron temperature profiles of the plasma are obtainedmore » from a set of imaging crystals also focused on the Ne free-bound continuum. We shot two types of gas nozzles in the experiment, annular and uniform fill, which varies the amount of mass in the plasma. 2D local thermodynamic equilibrium (LTE) and non-LTE MHD models predict a radiating region denser and cooler than measured. {copyright} {ital 1997 American Institute of Physics.}« less
  • The Z-pinch phase of a dense plasma focus (DPF) emits multiple-MeV ions in a ∼cm length. The mechanisms through which these physically simple devices generate such high energy beams in a relatively short distance are not fully understood. We are exploring the origins of these large gradients using measurements of an ion probe beam injected into a DPF during the pinch phase and the first kinetic simulations of a DPF Z-pinch. To probe the accelerating fields in our table top experiment, we inject a 4 MeV deuteron beam along the z-axis and then sample the beam energy distribution after itmore » passes through the pinch region. Using this technique, we have directly measured for the first time the acceleration of an injected ion beam. Our particle-in-cell simulations have been benchmarked on both a kJ-scale DPF and a MJ-scale DPF. They have reproduced experimentally measured neutron yields as well as ion beams and EM oscillations which fluid simulations do not exhibit. Direct comparisons between the experiment and simulations enhance our understanding of these plasmas and provide predictive design capability for accelerator and neutron source applications.« less
  • The difference between the ion thermal and effective temperatures is investigated through simulations of the Ne gas puff z-pinch reported by Kroupp et al. [Phys. Rev. Lett. 107, 105001 (2011)]. Calculations are performed using a 2D, radiation-magnetohydrodynamic code with Tabular Collisional-Radiative Equilibrium, namely Mach2-TCRE [Thornhill et al., Phys. Plasmas 8, 3480 (2001)]. The extensive data set of imaging and K-shell spectroscopy from the experiments provides a challenging validation test for z-pinch simulations. Synthetic visible images of the implosion phase match the observed large scale structure if the breakdown occurs at the density corresponding to the Paschen minimum. At the beginningmore » of stagnation (−4 ns), computed plasma conditions change rapidly showing a rising electron density and a peak in the ion thermal temperature of ∼1.8 keV. This is larger than the ion thermal temperature (<400 eV) inferred from the experiment. By the time of peak K-shell power (0 ns), the calculated electron density is similar to the data and the electron and ion thermal temperatures are equilibrated, as is observed. Effective ion temperatures are obtained from calculated emission line widths accounting for thermal broadening and Doppler velocity shifts. The observed, large effective ion temperatures (∼4 keV) early in the stagnation of this Ne pinch can be explained solely as a combination of compressional ion heating and steep radial velocity gradients near the axis. Approximations in the modeling are discussed in regard to the higher ion thermal temperature and lower electron density early in the stagnation compared to the experimental results.« less