Development and Testing of a High-Gain Magnetic Flux Compression Generator

Parker, J.V.; Cavazos, T.; Roth, Charles E.; Degnan, J.H.; Kiuttu, G.F.; Lehr, F.M.

doi:10.1109/megaguss.2006.4530687

Cited by 9 publications

(6 citation statements)

References 3 publications

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“…Electrical insulation of the FCG winding would limit electrical contact between the initial plasma and the FCG stator, and correspondingly would avoid the development of plasma formation. Nevertheless, research reports [1], [4] present puzzling evidence that even heavy insulation of windings of FCG stators does not help to solve the problem.…”

Section: Imaging Of Electric-field-free Gas Breakdownmentioning

confidence: 99%

Imaging of Electric-Field-Free Gas Breakdown

Shkuratov

Baird

Talantsev

et al. 2011

IEEE Trans. Plasma Sci.

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Images of electric-field-free gas breakdown are presented. Possible mechanism of the breakdown is proposed.Index Terms-Explosions, electric breakdown, shock waves. G AS BREAKDOWN and gas discharge have been detected in magnetic flux compressor generators (FCGs) since 1960s [1]. Recently [2], we have reported that gas breakdown in an FCG can occur without electric field. In this paper, we present a series of high-speed images of this type of gas breakdown and discuss a possible mechanism of the plasma initiation.In these studies, we used a loop flux compression generator (LFCG) [3]. The operation of an LFCG is similar to that of other types of FCGs, and it is based on magnetic flux compression inside a stator due to the explosively driven expansion of metallic armature. The unique feature of an LFCG is the opportunity to observe the processes that occur inside the generator from the very beginning until the final stage of its operation. To avoid any shock-induced glow in the atmosphere around the LFCG, we put the generator in a wooden box purged with helium to prevent afterglow from shocked nitrogen in the air. We used a Cordin 10A high-speed framing camera at 500 000 frames per second. Other experimental details are given in [2].A schematic diagram of LFCG is shown in Fig. 1. An external seed source generated the initial current of 2.6 kA before the explosive operation of the LFCG. The two detonators of the LFCG were initiated at t = 0, and one can see the light coming from the detonation of the C-4 high explosives (HE) inside a cylindrical aluminum armature of the LFCG [ Fig. 1 (t = 0 µs)]. As the LFCG armature started its expansion [a dark contour in Fig. 1 (t = 2 µs)], gas breakdown occurred within the LFCG and plasma appeared in the gap between the armature and the crowbar. Based on high-speed photograph images, the speed of the expansion of the armature was 1.6 ± 0.1 mm/µs at the initial stage and 2.9 ± 0.1 mm/µs at the Manuscript final stage. The electric field strength between the armature and the crowbar contacts was negligible during operation of the system; it did not exceed 7 V/mm. This electric field was not high enough to initiate gas breakdown and form plasma. Further expansion of the armature in Fig. 1 (t = 4 µs) was accompanied by the generation of intense plasma that filled the gap between the armature and the stator. The plasma front propagated along the inner perimeter of the stator [ Fig. 1 (6 µs) and Fig. 1 (8 µs)].The formation of plasma and the propagation of a plasma front with no electric field can cause the development of intense electric discharges in gas within the generators, even at low intensity of electric field. Electrical insulation of the FCG winding would limit electrical contact between the initial plasma and the FCG stator, and correspondingly would avoid the development of plasma formation. Nevertheless, research reports [1], [4] present puzzling evidence that even heavy insulation of windings of FCG stators does not help to solve the problem.One can better understand the pr...

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Section: Imaging Of Electric-field-free Gas Breakdownmentioning

confidence: 99%

Imaging of Electric-Field-Free Gas Breakdown

Shkuratov

Baird

Talantsev

et al. 2011

IEEE Trans. Plasma Sci.

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“…Although compression and heating of the gas will occur, at least for SF 6 these conditions should still allow a breakdown strength higher than the electric fields experienced by the gas. At elevated temperatures, SF 6 dissociates, but the dissociated molecules, SF 5 and SF 4 , are even better insulators than SF 6 (we have not addressed the issue of photoionization here).…”

Section: Technical Issuesmentioning

confidence: 99%

Interoperability Issues in Noncombatant Evacuation Operations

Marcellus¹,

Paul²

2008

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“…The output of SAM is coupled through a parallel-plate transmission line to a single turn loop wrapped around the stator winding of the second stage. The second stage generator, designated JILL, has been described previously as a stand-alone device [3].…”

Section: Introductionmentioning

confidence: 99%

Performance of a compact, cascade FCG system

Parker

Roth

Coffey

et al. 2009

2009 IEEE Pulsed Power Conference

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A system of two FCG's coupled via "flux-trapping" is described. The driver FCG, designated SAM, was custom-designed for this application. The output of SAM is a single-turn loop that is tightly coupled to the first winding section of a larger FCG, designated JILL. The single-turn driver loop, coupled to 35 turns of the input winding of JILL, provides a calculated flux gain of 28.For the first experimental test of the SAM/JILL system, the SAM generator was seeded with 1.0 kA (flux 0.29 Wb) and produced a current of 472 kA (flux 0.10 Wb) in the coupling loop at crowbar time of the JILL generator. Based on the calculated mutual inductance of 5.95 H, the JILL generator began operation with a seed flux of 2.81 Wb. With this seed flux, the expected output current for JILL driving a 0.8 H load is 1.8 MA. The measured output current was 884 kA, roughly one half of the expected current. Analysis of the I-dot data from the test shows that this low performance was due to multiple electrical breakdowns in the JILL generator during the interval when the armature-stator contact point was underneath the coupling loop.Subsequent analysis suggests that the electrical breakdowns were the result of flux compression in the coupling loop. Details of the experiment and analysis will be presented. A modification to the SAM/JILL apparatus is proposed to eliminate electrical breakdown. 9781-4244-4065-8/09/$25.00 ©2009 IEEE

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Development and Testing of a High-Gain Magnetic Flux Compression Generator

Cited by 9 publications

References 3 publications

Imaging of Electric-Field-Free Gas Breakdown

Imaging of Electric-Field-Free Gas Breakdown

Interoperability Issues in Noncombatant Evacuation Operations

Performance of a compact, cascade FCG system

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