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Title: Contribution of the backstreaming ions to the self-magnetic pinch (SMP) diode current

Abstract

The results presented here were obtained with a self-magnetic pinch (SMP) diode mounted at the front high voltage end of the RITS accelerator. RITS is a Self-Magnetically Insulated Transmission Line (MITL) voltage adder that adds the voltage pulse of six 1.3 MV inductively insulated cavities. The RITS driver together with the SMP diode has produced x-ray spots of the order of 1 mm in diameter and doses adequate for the radiographic imaging of high area density objects. Although, through the years, a number of different types of radiographic electron diodes have been utilized with SABER, HERMES III and RITS accelerators, the SMP diode appears to be the most successful and simplest diode for the radiographic investigation of various objects. Our experiments had two objectives: first to measure the contribution of the back-streaming ion currents emitted from the anode target and second to try to evaluate the energy of those ions and hence the Anode-Cathode (A-K) gap actual voltage. In any very high voltage inductive voltage adder utilizing MITLs to transmit the power to the diode load, the precise knowledge of the accelerating voltage applied on the A-K gap is problematic. This is even more difficult in an SMP diode wheremore » the A-K gap is very small (~1 cm) and the diode region very hostile. The accelerating voltage quoted in the literature is from estimates based on the measurements of the anode and cathode currents of the MITL far upstream from the diode and utilizing the para-potential flow theories and inductive corrections. Thus, it would be interesting to have another independent measurement to evaluate the A-K voltage. The diode's anode is made of a number of high-Z metals in order to produce copious and energetic flash x-rays. It was established experimentally that the back-streaming ion currents are a strong function of the anode materials and their stage of cleanness. We have measured the back-streaming ion currents emitted from the anode and propagating through a hollow cathode tip for various diode configurations and different techniques of target cleaning treatment: namely, heating at very high temperatures with DC and pulsed current, with RF plasma cleaning, and with both plasma cleaning and heating. In conclusion, we have also evaluated the A-K gap voltage by energy filtering technique. Experimental results in comparison with LSP simulations are presented.« less

Authors:
 [1]; ORCiD logo [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]; ORCiD logo [1];  [1];  [1];  [1];  [2];  [2];  [2];  [2];  [3]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  2. National Security Technologies, LLC, Las Vegas, NV (United States)
  3. Voss Scientific, LLC, Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1464185
Report Number(s):
SAND-2017-9070J
Journal ID: ISSN 1070-664X; 656496
Grant/Contract Number:  
AC04-94AL85000; NA0003525
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 4; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Mazarakis, Michael G., Bennett, Nichelle, Cuneo, Michael E., Fournier, Sean D., Johnston, Mark D., Kiefer, Mark L., Leckbee, Joshua J., Nielsen, Dan S., Oliver, Bryan V., Sceiford, Matthew E., Simpson, Sean C., Renk, Timothy J., Ruiz, Carlos L., Webb, Timothy J., Ziska, Derek, Droemer, Darryl W., Gignac, Raymond E., Obregon, Robert J., Wilkins, Frank L., and Welch, Dale R. Contribution of the backstreaming ions to the self-magnetic pinch (SMP) diode current. United States: N. p., 2018. Web. doi:10.1063/1.5009014.
Mazarakis, Michael G., Bennett, Nichelle, Cuneo, Michael E., Fournier, Sean D., Johnston, Mark D., Kiefer, Mark L., Leckbee, Joshua J., Nielsen, Dan S., Oliver, Bryan V., Sceiford, Matthew E., Simpson, Sean C., Renk, Timothy J., Ruiz, Carlos L., Webb, Timothy J., Ziska, Derek, Droemer, Darryl W., Gignac, Raymond E., Obregon, Robert J., Wilkins, Frank L., & Welch, Dale R. Contribution of the backstreaming ions to the self-magnetic pinch (SMP) diode current. United States. doi:10.1063/1.5009014.
Mazarakis, Michael G., Bennett, Nichelle, Cuneo, Michael E., Fournier, Sean D., Johnston, Mark D., Kiefer, Mark L., Leckbee, Joshua J., Nielsen, Dan S., Oliver, Bryan V., Sceiford, Matthew E., Simpson, Sean C., Renk, Timothy J., Ruiz, Carlos L., Webb, Timothy J., Ziska, Derek, Droemer, Darryl W., Gignac, Raymond E., Obregon, Robert J., Wilkins, Frank L., and Welch, Dale R. Wed . "Contribution of the backstreaming ions to the self-magnetic pinch (SMP) diode current". United States. doi:10.1063/1.5009014. https://www.osti.gov/servlets/purl/1464185.
@article{osti_1464185,
title = {Contribution of the backstreaming ions to the self-magnetic pinch (SMP) diode current},
author = {Mazarakis, Michael G. and Bennett, Nichelle and Cuneo, Michael E. and Fournier, Sean D. and Johnston, Mark D. and Kiefer, Mark L. and Leckbee, Joshua J. and Nielsen, Dan S. and Oliver, Bryan V. and Sceiford, Matthew E. and Simpson, Sean C. and Renk, Timothy J. and Ruiz, Carlos L. and Webb, Timothy J. and Ziska, Derek and Droemer, Darryl W. and Gignac, Raymond E. and Obregon, Robert J. and Wilkins, Frank L. and Welch, Dale R.},
abstractNote = {The results presented here were obtained with a self-magnetic pinch (SMP) diode mounted at the front high voltage end of the RITS accelerator. RITS is a Self-Magnetically Insulated Transmission Line (MITL) voltage adder that adds the voltage pulse of six 1.3 MV inductively insulated cavities. The RITS driver together with the SMP diode has produced x-ray spots of the order of 1 mm in diameter and doses adequate for the radiographic imaging of high area density objects. Although, through the years, a number of different types of radiographic electron diodes have been utilized with SABER, HERMES III and RITS accelerators, the SMP diode appears to be the most successful and simplest diode for the radiographic investigation of various objects. Our experiments had two objectives: first to measure the contribution of the back-streaming ion currents emitted from the anode target and second to try to evaluate the energy of those ions and hence the Anode-Cathode (A-K) gap actual voltage. In any very high voltage inductive voltage adder utilizing MITLs to transmit the power to the diode load, the precise knowledge of the accelerating voltage applied on the A-K gap is problematic. This is even more difficult in an SMP diode where the A-K gap is very small (~1 cm) and the diode region very hostile. The accelerating voltage quoted in the literature is from estimates based on the measurements of the anode and cathode currents of the MITL far upstream from the diode and utilizing the para-potential flow theories and inductive corrections. Thus, it would be interesting to have another independent measurement to evaluate the A-K voltage. The diode's anode is made of a number of high-Z metals in order to produce copious and energetic flash x-rays. It was established experimentally that the back-streaming ion currents are a strong function of the anode materials and their stage of cleanness. We have measured the back-streaming ion currents emitted from the anode and propagating through a hollow cathode tip for various diode configurations and different techniques of target cleaning treatment: namely, heating at very high temperatures with DC and pulsed current, with RF plasma cleaning, and with both plasma cleaning and heating. In conclusion, we have also evaluated the A-K gap voltage by energy filtering technique. Experimental results in comparison with LSP simulations are presented.},
doi = {10.1063/1.5009014},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 4,
volume = 25,
place = {United States},
year = {2018},
month = {4}
}

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