skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A second generation EMET railgun for secondary arc studies

Abstract

Since 1985 GT-Devices has been operating a pair of railguns with lengths of 0.9 m and 3.6 m respectively. Although velocities up to 5.65 km/s have been obtained with clean plasma armature structures devoid of secondary arcs, performance on most shots is degraded to one degree or another by the formation of parasitic secondary arcs. These experimental results, however, have not been very reproducible, making controlled studies of these secondary arcs difficult. A new second generation railgun is now being constructed to improve straightness, stiffness, sealing, and diagnostic access. The basic design consists of a steel tube with a thin lengthwise slit forming two halves in cross section with bolt preloading. The internal structure consists of split tubular G-10 compression blocks with Glidcop AL-15 rails and polycarbonate insulators formed from 90 degree tube sections. Machining tolerance mismatch is adjusted with compliant layers as required. An adjustable diameter, helical diamond lap is used to produce a finished round bore of nominally 1 cm diameter in the assembled launcher and for bore refurbishment between shots. This paper discusses the design details of the new railgun, injector, and diagnostics and presents some initial experimental results.

Authors:
; ;  [1]
  1. (GT-Devices, Inc., Alexandria, VA (United States))
Publication Date:
OSTI Identifier:
5654988
Report Number(s):
CONF-9004136-
Journal ID: ISSN 0018-9464; CODEN: IEMGA; TRN: 92-009392
Resource Type:
Conference
Resource Relation:
Journal Name: IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers); (United States); Journal Volume: 27:1; Conference: 5. IEEE symposium on electromagnetic launcher technology, Destin, FL (United States), 1-5 Apr 1990
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Fu; 43 PARTICLE ACCELERATORS; RAILGUN ACCELERATORS; FUEL INJECTION SYSTEMS; COMPUTER CODES; DESIGN; ELECTROMAGNETIC RADIATION; PLASMA ACCELERATION; PLASMA DIAGNOSTICS; PLASMA GUNS; POLYCARBONATES; PROJECTILES; ACCELERATION; ACCELERATORS; CARBON COMPOUNDS; CARBONATES; FUEL SYSTEMS; OXYGEN COMPOUNDS; RADIATIONS; 700460* - Fusion Technology- Heating & Fueling Systems; Fuels- (1992); 430300 - Particle Accelerators- Auxiliaries & Components; 430100 - Particle Accelerators- Design, Development, & Operation

Citation Formats

Witherspoon, F.D., Burton, R.L., and Goldstein, S.A. A second generation EMET railgun for secondary arc studies. United States: N. p., 1991. Web.
Witherspoon, F.D., Burton, R.L., & Goldstein, S.A. A second generation EMET railgun for secondary arc studies. United States.
Witherspoon, F.D., Burton, R.L., and Goldstein, S.A. 1991. "A second generation EMET railgun for secondary arc studies". United States. doi:.
@article{osti_5654988,
title = {A second generation EMET railgun for secondary arc studies},
author = {Witherspoon, F.D. and Burton, R.L. and Goldstein, S.A.},
abstractNote = {Since 1985 GT-Devices has been operating a pair of railguns with lengths of 0.9 m and 3.6 m respectively. Although velocities up to 5.65 km/s have been obtained with clean plasma armature structures devoid of secondary arcs, performance on most shots is degraded to one degree or another by the formation of parasitic secondary arcs. These experimental results, however, have not been very reproducible, making controlled studies of these secondary arcs difficult. A new second generation railgun is now being constructed to improve straightness, stiffness, sealing, and diagnostic access. The basic design consists of a steel tube with a thin lengthwise slit forming two halves in cross section with bolt preloading. The internal structure consists of split tubular G-10 compression blocks with Glidcop AL-15 rails and polycarbonate insulators formed from 90 degree tube sections. Machining tolerance mismatch is adjusted with compliant layers as required. An adjustable diameter, helical diamond lap is used to produce a finished round bore of nominally 1 cm diameter in the assembled launcher and for bore refurbishment between shots. This paper discusses the design details of the new railgun, injector, and diagnostics and presents some initial experimental results.},
doi = {},
journal = {IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers); (United States)},
number = ,
volume = 27:1,
place = {United States},
year = 1991,
month = 1
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • This paper reports on the EMET projectile which uses joule heating to accelerate the projectile in a railgun with a predominantly electrothermal driving force. The structure is designed to conduct armature current within a thin annular band around the shank of the large L/D dumbbell-shaped projectile. Current is initiated by a fuse located around the shank, and an impedance of 8 m{Omega} is achieved, compared to the 1-2 m{Omega} observed for EM guns. A supersonic nozzle in the projectile tail section expands and cools the armature plasma to raise its resistivity, prevent secondary arcs and provide additional accelerating thrust. Experimentalmore » data is presented for 9.5 mm diameter, 5 gm projectiles, accelerated to nearly 600 m/sec at 55 kA in a 0.9 m railgun. The armature remains confined in the projectile structure, and 75% of the acceleration is provided electrothermally.« less
  • Construction and function of a modern dust collecting facility for effective control of secondary emissions in a BOF shop will be discussed. Operating results and experience gained relevant to the design and construction of such systems will be presented. Using the blast furnace casthouse dust collecting system as an example, it will be shown how considerable energy can be saved by introducing appropriate design, process and instrumentation measures. These examples serve to illustrate how state of the art dust collecting technology combined with a sound knowledge of the processes of the iron and steel industry can help reduce investment andmore » operating costs considerably.« less
  • In this paper the analytical expression for the force accelerating a current filament in a railgun geometry is derived. The model is extended to develop the force on the primary in the presence of secondary arcs. The correspondence between the physical model and an equivalent circuit is established, and the force is shown to reduce properly in limiting cases.
  • Optical second-harmonic generation (SHG) is sensitive enough to respond to a submonolayer of surface atoms or molecules. It can therefore be used to probe surfaces or interfaces between two centrosymmetric media. The surface-specific nature of this optical method offers some advantages. We have demonstrated in recent experiments that resonant SHG can allow us to obtain spectroscopic data of submonolayers of adsorbed molecules on a surface. The signal was so strong that less than one tenth of a monolayer of dye molecules could be easily detected. The method can be applied to molecules adsorbed at an interface between two dense mediamore » such as a liquid/solid interface. Then, using SHG, adsorption isotherms of adsorbates on substrates can be measured. One is often interested in how large the bulk contribution to SHG is in comparison with the surface contribution. Second-order nonlinear optical processes are forbidden in a medium with inversion symmetry only in the electric-dipole approximation. Could SGH from electric-quadrupole and magnetic-dipole contributions in the bulk be so strong as to mask out the electric-dipole contribution from the surface. We have found that the SH signal from a centrosymmetric substrate can be changed appreciably by the adsorption of a monolayer. This clearly indicates that it is the adsorbate layer rather than the bulk of the substrate which dominates the SHG process. We are, however, also interested in developing the SHG technique for studying bare surfaces, and would like to know the relative bulk and surface contribution to SHG in such cases. We have studied this problem experimentally by measuring the SHG from well-defined faces of a crystalline material.« less
  • Surface second harmonic generation (SHG) is used to monitor adsorption and desorption of molecules on metal and semiconductor surfaces in ultrahigh vacuum. Surface SHG has also been used to study monolayers of molecules at a liquid/air interface. 13 refs., 6 figs. (WRF)