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Title: Immersed-Bz Diode Research on RITS at Sandia.

Abstract

Abstract not provided.

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Laboratories,, Washington, D.C.
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1148157
Report Number(s):
SAND2007-4011C
522563
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Proposed for presentation at the 2007 IEEE Pulsed Power & Plasma Science Conference held June 17-22, 2007 in Albuquerque, NM.
Country of Publication:
United States
Language:
English

Citation Formats

Rovang, Dean C., Johnston, Mark D., Maenchen, John E., Oliver, Bryan Velten, Portillo, Salvador, Madrid, Elizabeth Ann, Bruner, Nichelle, Rose, David V., Welch, Dale Robert, Cooper, Graham M., and McLean, John. Immersed-Bz Diode Research on RITS at Sandia.. United States: N. p., 2007. Web.
Rovang, Dean C., Johnston, Mark D., Maenchen, John E., Oliver, Bryan Velten, Portillo, Salvador, Madrid, Elizabeth Ann, Bruner, Nichelle, Rose, David V., Welch, Dale Robert, Cooper, Graham M., & McLean, John. Immersed-Bz Diode Research on RITS at Sandia.. United States.
Rovang, Dean C., Johnston, Mark D., Maenchen, John E., Oliver, Bryan Velten, Portillo, Salvador, Madrid, Elizabeth Ann, Bruner, Nichelle, Rose, David V., Welch, Dale Robert, Cooper, Graham M., and McLean, John. Fri . "Immersed-Bz Diode Research on RITS at Sandia.". United States. doi:. https://www.osti.gov/servlets/purl/1148157.
@article{osti_1148157,
title = {Immersed-Bz Diode Research on RITS at Sandia.},
author = {Rovang, Dean C. and Johnston, Mark D. and Maenchen, John E. and Oliver, Bryan Velten and Portillo, Salvador and Madrid, Elizabeth Ann and Bruner, Nichelle and Rose, David V. and Welch, Dale Robert and Cooper, Graham M. and McLean, John},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}

Conference:
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  • The immersed-B{sub z} diode is being developed as a high-brightness, flash x-ray radiography source. This diode is a foil-less electron-beam diode with a long, thin, needle-like cathode inserted into the bore of a solenoid. The solenoidal magnetic field guides the electron beam emitted from the cathode to the anode while maintaining a small beam radius. The electron beam strikes a thin, high-atomic-number anode and produces bremsstrahlung. We report on an extensive series of experiments where an immersed-B{sub z} diode was fielded on the RITS-3 pulsed power accelerator, a 3-cell inductive voltage generator that produced peak voltages between 4 and 5more » MV, {approx}140 kA of total current, and power pulse widths of {approx}50 ns. The diode is a high impedance device that, for these parameters, nominally conducts {approx}30 kA of electron beam current. Diode operating characteristics are presented and two broadly characterized operating regimes are identified: a nominal operating regime where the total diode current is characterized as classically bipolar and an anomalous impedance collapse regime where the total diode current is in excess of the bipolar limit and up to the full accelerator current. The operating regimes are approximately separated by cathode diameters greater than {approx}3 mm for the nominal regime and less than {approx} 3 mm for the anomalous impedance collapse regime. This report represents a compilation of data taken on RITS-3. Results from key parameter variations are presented in the main body of the report and include cathode diameter, anode-cathode gap, and anode material. Results from supporting parameter variations are presented in the appendices and include magnetic field strength, prepulse, pressure and accelerator variations.« less
  • Recent experiments (1) have adapted existing magne-tically insulated induction voltage adders (Sabre, Hermes III) to drive a 10 MV diode immersed in magnetic fields as high as 50 T. In such a diode, an electron beam of tens of kA can be confined by the magnetic field to a diameter of about 1 mm, and when it strikes a high-Z anode it can create a bremsstrahlung x-ray source intense enough to radiograph massive objects with high resolution. RITS is an adder system designed specially to drive such diodes, and it will be used to develop and exploit them. As inmore » other adder-based pulsers such as Sabre, Hermes III, and Kalif-Heliq the induction cells have amorphous- iron cores, and the pulse-forming system consists of water dielectric pulse lines and self-closing water switches that are pulse-charged from Marx-charged intermediate water capacitors through laser-triggered Rimfire switches. An oil prepulse switch in series with each pulse line is designed to reduce cathode prepulse to less than ┬▒ 5 kV, and a means is provided to bias the cathode and avoid negative prepulse entirely. The RITS pulse-forming system consists of two modules. Each module has one Marx that charges two 3 MV intermediate stores, each of which charges three 7.8 ohm pulselines, making six pulselines per module. The two modules in concert can supply 1.35 MV, 50 ns pulses to a twelve-cell adder and thus drive a 16 MV diode with a single pulse. The 1.35 MV induction cells each have a single-point feed, from which a single, slotted azimuthal oil transmission line distributes energy uniformly around the cell. The modules can also be pulsed separately at different times, either to power two 8 MV adders that each drive one of two closely-spaced cathodes immersed in a common magnetic field, or to provide two separate pulses to a common six- cell adder and a single 8 NIV diode; in these two-pulse modes, the spacing of the two 50 ns pulses may be chosen to be anything from a few hundred ns upward. The use of only one pulse line per cell has been shown to increase the extent to which the cell voltages can vary with the timing of closure of the water switches. This and all other functions of RITS have been simulated in detail, and a conservative electrical design has been developed. This will be illustrated, along with the conceptual design of a pulse-sorting network that can couple two pulselines efilciently to one cell when the two RITS modules drive a common adder in two-pulse mode.« less
  • No abstract prepared.
  • Abstract not provided.
  • Sandia National Laboratories is investigating and developing high-dose, high-brightness flash radiographic sources. The immersed-B{sub z} diode employs large-bore, high-field solenoid magnets to help guide and confine an intense electron beam from a needle-like cathode 'immersed' in the axial field of the magnet. The electron beam is focused onto a high-atomic-number target/anode to generate an intense source of bremsstrahlung X-rays. Historically, these diodes have been unable to achieve high dose (> 500 rad {at} m) from a small spot (< 3 mm diameter). It is believed that this limitation is due in part to undesirable effects associated with the interaction ofmore » the electron beam with plasmas formed at either the anode or the cathode. Previous research concentrated on characterizing the behavior of diodes, which used untreated, room temperature (RT) anodes. Research is now focused on improving the diode performance by modifying the diode behavior by using cryogenic anodes that are coated in-situ with frozen gases. The objective of these cryogenically treated anodes is to control and limit the ion species of the anode plasma formed and hence the species of the counter-streaming ions that can interact with the electron beam. Recent progress in the development, testing and fielding of the cryogenically cooled immersed diodes at Sandia is described.« less