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Title: Note: Infrared laser diagnostics for deuterium gas puff Z pinches

Authors:
ORCiD logo; ; ; ; ORCiD logo;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1372413
Grant/Contract Number:
SC0016500; NA0002075; AC52-06NA25946
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 88; Journal Issue: 7; Related Information: CHORUS Timestamp: 2018-02-14 19:33:08; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English

Citation Formats

Ivanov, V. V., McKee, E. S., Hammel, B. D., Darling, T. W., Swanson, K. J., and Covington, A. M.. Note: Infrared laser diagnostics for deuterium gas puff Z pinches. United States: N. p., 2017. Web. doi:10.1063/1.4995416.
Ivanov, V. V., McKee, E. S., Hammel, B. D., Darling, T. W., Swanson, K. J., & Covington, A. M.. Note: Infrared laser diagnostics for deuterium gas puff Z pinches. United States. doi:10.1063/1.4995416.
Ivanov, V. V., McKee, E. S., Hammel, B. D., Darling, T. W., Swanson, K. J., and Covington, A. M.. Sat . "Note: Infrared laser diagnostics for deuterium gas puff Z pinches". United States. doi:10.1063/1.4995416.
@article{osti_1372413,
title = {Note: Infrared laser diagnostics for deuterium gas puff Z pinches},
author = {Ivanov, V. V. and McKee, E. S. and Hammel, B. D. and Darling, T. W. and Swanson, K. J. and Covington, A. M.},
abstractNote = {},
doi = {10.1063/1.4995416},
journal = {Review of Scientific Instruments},
number = 7,
volume = 88,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on July 24, 2018
Publisher's Accepted Manuscript

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  • A multicolor, time-gated, soft x-ray pinhole imaging instrument is fielded as part of the core diagnostic set on the 25 MA Z machine [M. E. Savage et al., in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, New York, 2007), p. 979] for studying intense wire array and gas puff Z-pinch soft x-ray sources. Pinhole images are reflected from a planar multilayer mirror, passing 277 eV photons with <10 eV bandwidth. An adjacent pinhole camera uses filtration alone to view 1-10 keV photons simultaneously. Overlaying these data provides composite images that contain both spectral as well as spatial information,more » allowing for the study of radiation production in dense Z-pinch plasmas. Cu wire arrays at 20 MA on Z show the implosion of a colder cloud of material onto a hot dense core where K-shell photons are excited. A 528 eV imaging configuration has been developed on the 8 MA Saturn generator [R. B. Spielman et al., and A. I. P. Conf, Proc. 195, 3 (1989)] for imaging a bright Li-like Ar L-shell line. Ar gas puff Z pinches show an intense K-shell emission from a zippering stagnation front with L-shell emission dominating as the plasma cools.« less
  • Double-shell Ar gas puff implosions driven by 16.5±0.5 MA on the Z generator at Sandia National Laboratories are very effective emitters of Ar K-shell radiation (photon energy >3 keV), producing yields of 330 ± 9% kJ (B. Jones et al., Phys. Plasmas, 22, 020706, 2015). In addition, previous simulations and experiments have reported dramatic increases in K-shell yields when adding an on-axis jet to double shell gas puffs for some configurations.
  • Results obtained with the University of California, Irvine gas-puff Z-pinch experiment are described for deuterium and deuterium-argon mixtures. This experiment utilizes a hollow cylindrical gas puff injected between electrodes driven by a 4.8-kJ capacitor bank. Various gas compositions have been tested, including pure deuterium, 90% D/sub 2/-10% Ar, and up to 10% D/sub 2/-90% Ar. We have observed the stages of collapse and its rate, electron density at the pinch, neutron yield, and the time dependence of x-ray and neutron emission. When a 90% D/sub 2/-10% Ar mixture is injected, the plasma annulus is observed to separate into two columnsmore » which implode concentrically.« less
  • The Proto-II accelerator has been used to implode krypton and xenon annular gas puffs. A significant fraction of the machine electrical energy was converted first to plasma kinetic energy and then to x rays when the plasma pinched on axis. Quantitative measurements using time-resolved bolometers have shown as much as 10% of the total radiation yield near 1 keV in Xe and 2 keV in Kr. We have compared this radiation yield to the predictions from one-dimensional magnetohydrodynamic code calculations. The implosions were also observed with both time-integrated pinhole cameras and spectrographs. No hard x-ray (E>10 keV) output was observed.
  • There is strong interest in many laboratories worldwide in utilizing less expensive, longer rise-time (> 200 ns) pulsed power to drive x-ray producing z-pinches. Based on the idea of a magnetically-driven annular implosion, the emission of K-shell photons requires high energy per ion (implosion velocity above 43 cm/{mu}s for argon) to strip the atoms to the helium-like and hydrogen-like states. This high velocity must be combined with high density in the final hot plasma to produce significant x-ray yield. To first order, implosion velocity correlates with the initial diameter of the z-pinch load in proportion to the implosion time. Thusmore » some effort has been made in the last few years to develop larger diameter z-pinch loads suitable for use with the longer rise-time drivers. Advancing from the <4 cm diameter loads (used for 100 ns implosions) of a decade ago, progress with 8 cm loads was reported at the last DZP meeting. Here we review further progress with 12 cm loads as used to date at peak currents of 3.5 MA to almost 6 MA with >200 ns implosion times. The most interesting result is that implosions from 12 cm diameter have not proven hopelessly unstable. High quality pinches with few millimeter K-shell emitting diameters, <5 ns pulse widths, electron temperatures above 1.7 keV and ion densities >4*1019/cm{sup 3} have been achieved. The observed argon K yield has equaled simple scaling estimates that ignore the expected increase in instabilities for large initial diameters. This more stable result probably occurs because we are using radial mass distributions that are 'snowplow' stabilized, i.e., they are not shell-like but rather have smoothly varying mass with the radial density gradient, d{rho}/dr small or negative over much of the gas flow. Data on yield as a function of the radial distribution suggest that a near or on-axis peak in the initial gas density is probably optimal. Work remains to be done to establish the details of the 'best' mass distribution.« less