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Title: The search for a 100MA RancheroS magnetic flux compression generator

Abstract

The Eulerian AMR rad-hydro-MHD code Roxane was used to investigate modifications to existing designs of the new RancheroS class of Magnetic Flux Compression Generators (FCGs) which might allow some members of this FCG family to exceed 100 MA driving a 10 nH static load. This report details the results of that study and proposes a specific generator modification which seems to satisfy both the peak current and desired risetime for the current pulse into the load. The details of the study and necessary modifications are presented. For details of the LA43S RancheroS FCG design and predictions for the first use of the generator refer to the relevant publications.

Authors:
 [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1321696
Report Number(s):
LA-UR-16-26685
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; Magnetic Flux Compression Generator

Citation Formats

Watt, Robert Gregory. The search for a 100MA RancheroS magnetic flux compression generator. United States: N. p., 2016. Web. doi:10.2172/1321696.
Watt, Robert Gregory. The search for a 100MA RancheroS magnetic flux compression generator. United States. doi:10.2172/1321696.
Watt, Robert Gregory. 2016. "The search for a 100MA RancheroS magnetic flux compression generator". United States. doi:10.2172/1321696. https://www.osti.gov/servlets/purl/1321696.
@article{osti_1321696,
title = {The search for a 100MA RancheroS magnetic flux compression generator},
author = {Watt, Robert Gregory},
abstractNote = {The Eulerian AMR rad-hydro-MHD code Roxane was used to investigate modifications to existing designs of the new RancheroS class of Magnetic Flux Compression Generators (FCGs) which might allow some members of this FCG family to exceed 100 MA driving a 10 nH static load. This report details the results of that study and proposes a specific generator modification which seems to satisfy both the peak current and desired risetime for the current pulse into the load. The details of the study and necessary modifications are presented. For details of the LA43S RancheroS FCG design and predictions for the first use of the generator refer to the relevant publications.},
doi = {10.2172/1321696},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

Technical Report:

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  • An introduction to the concept of a propellant-driven magnetic flux compression generator is presented, together with the theory of its operation. The principles of operation of the propellant flux compression generator combine generator principles, derived from lumped parameter circuit theory, and interior ballistic principles.
  • Three magnetic flux compression generator (FCG) geometries are reviewed and compared for their suitability as high-current, high-power drivers for z-pinch implosion programs at Los Alamos. They are the inside-out coaxial FCG, the disk FCG, and the outside-in coaxial FCG. A wide range of issues is discussed for each type FCG including current-carrying capability current densities, robustness, explosive mass and shape, initiation schemes, efficiency, operating times, complexity, and expense associated with development and fabrication. Equations are derived and used in simple scaling studies. The results of these studies are supported by MHD calculations and references to relevant experiments both here andmore » in Russia. The inside-out coaxial FCG is shown to be suitable, both for the very high current applications and for anticipated future Trailmaster concepts. Based upon this analysis and results reported in the Russian literature, the inside-out coaxial FCG is more suitable than the disk FCG for the high-current applications considered, and the two are roughly equivalent when applied to lower-current Trailmaster concepts. The outside-in coaxial FCG is unsuitable for either application because of its limited current-carrying capability and the large investment required for initial development.« less
  • Three magnetic flux compression generator (FCG) geometries are reviewed and compared for their suitability as high-current, high-power drivers for z-pinch implosion programs at Los Alamos. They are the inside-out coaxial FCG, the disk FCG, and the outside-in coaxial FCG. A wide range of issues is discussed for each type FCG including current-carrying capability current densities, robustness, explosive mass and shape, initiation schemes, efficiency, operating times, complexity, and expense associated with development and fabrication. Equations are derived and used in simple scaling studies. The results of these studies are supported by MHD calculations and references to relevant experiments both here andmore » in Russia. The inside-out coaxial FCG is shown to be suitable, both for the very high current applications and for anticipated future Trailmaster concepts. Based upon this analysis and results reported in the Russian literature, the inside-out coaxial FCG is more suitable than the disk FCG for the high-current applications considered, and the two are roughly equivalent when applied to lower-current Trailmaster concepts. The outside-in coaxial FCG is unsuitable for either application because of its limited current-carrying capability and the large investment required for initial development.« less
  • The Ranchero Magnetic Flux Compression Generator (FCG) has been used to create current pulses in the 10-­100 MA range for driving both “static” low inductance (0.5 nH) loads1 for generator demonstration purposes and high inductance (10-­20 nH) imploding liner loads2 for ultimate use in physics experiments at very high energy density. Simulations of the standard Ranchero generator have recently shown that it had a design issue that could lead to flux trapping in the generator, and a non-­ robust predictability in its use in high energy density experiments. A re-­examination of the design concept for the standard Ranchero generator, promptedmore » by the possible appearance of an aneurism at the output glide plane, has led to a new generation of Ranchero generators designated the RancheroS (for swooped). This generator has removed the problematic output glide plane and replaced it with a region of constantly increasing diameter in the output end of the FCG cavity in which the armature is driven outward under the influence of an additional HE load not present in the original Ranchero. The resultant RancheroS generator, to be tested in LA43S-­L13, probably in early FY17, has a significantly increased initial inductance and may be able to drive a somewhat higher load inductance than the standard Ranchero. This report will use the Eulerian AMR code Roxane to study the ability of the new design to drive static loads, with a goal of providing a database corresponding to the load inductances for which the generator might be used and the anticipated peak currents such loads might produce in physics experiments. Such a database, combined with a simple analytic model of an ideal generator, where d(LI)/dt = 0, and supplemented by earlier estimates of losses in actual use of the standard Ranchero, scaled to estimate the increase in losses due to the longer current carrying perimeter in the RancheroS, can then be used to bound the expectations for the current drive one may apply to any load assembly in future experiments.« less
  • A very successful series of three flux compression generator (FCG) experiments and one hydro-only test, designed to quantify the performance capabilities and limitations of high-current, high-field, high-power coaxial FCGs, is reported. In the last test, the CN-III FCG produced a peak current of >150 MA with a final doubling time of <10{mu}s into a 2-nH inductive load. Experimental results are in excellent agreement with extensive preshot and postshot one-dimensional (1D) and two-dimensional (2D) magnetohydrodynamic (MHD) calculations.