Measurement of electron energy deposition necessary to form an anode plasma in Ta, Ti, and C for coaxial bremsstrahlung diodes

Sanford, T. W. L.; Halbleib, J.A.; Poukey, J. W.; Pregenzer, Arian L.; Pate, Ronald C.; Heath, C.E.; Mock, R. C.; Mastin, Gary A.; Ghiglia, Dennis C.; Roemer, Timothy John; Spence, P.; Proulx, G. A.

doi:10.1063/1.343913

Cited by 87 publications

(31 citation statements)

References 18 publications

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“…The model assumes SCL emission of ions (H þ ) directly from surfaces for which the local temperature has increased by 400 K. This threshold condition for anode ion emission is based on experimental evidence from high-power, charged-particle diode experiments (see, for example, Refs. [26,27]). …”

Section: Simulation Modelmentioning

confidence: 99%

Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

Rose

Madrid

Welch

et al. 2015

Phys. Rev. ST Accel. Beams

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Numerical simulations of a vacuum post-hole convolute driven by magnetically insulated vacuum transmission lines (MITLs) are used to study current losses due to charged particle emission from the MITL-convolute-system electrodes. This work builds on the results of a previous study [E. A. Madrid et al. Phys. Rev. ST Accel. Beams 16, 120401 (2013)] and adds realistic power pulses, Ohmic heating of anode surfaces, and a model for the formation and evolution of cathode plasmas. The simulations suggest that modestly larger anode-cathode gaps in the MITLs upstream of the convolute result in significantly less current loss. In addition, longer pulse durations lead to somewhat greater current loss due to cathodeplasma expansion. These results can be applied to the design of future MITL-convolute systems for high-current pulsed-power systems.

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Section: Simulation Modelmentioning

confidence: 99%

Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

Rose

Madrid

Welch

et al. 2015

Phys. Rev. ST Accel. Beams

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“…Often, this results in areas of high current density on the anode which heats the anode surface. When the anode surface temperature is raised about 400 °C it is observed that a plasma forms on the anode surface which becomes a strong emitter of ions [3], a process called thermal ion emission.…”

Section: Emission Processes In High-power Cross-field Vacuum Devicesmentioning

confidence: 99%

A megavolt test stand for measuring cathode and anode emissions with nanosecond pulses

Allen¹,

Hinshelwood²,

Schumer³

et al. 2014

2014 IEEE 41st International Conference on Plasma Sciences (ICOPS) Held With 2014 IEEE International Conference on High-Power P

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“…Blaugrund [47] observed this with electron beam pinches when the anode temperature reaches 400 °C. Sanford [48] observed that anode plasma forms on metals at about 400 °C. For most shots it was possible to get a good fit at 400 °C if the incident beam radius was expanded by ~1 mm.…”

Section: Large Gapsmentioning

confidence: 99%

Suppression of electron emission from metal electrodes : LDRD 28771 final report.

Stygar¹,

Savage²,

Ives³

et al. 2003

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This research consisted of testing surface treatment processes for stainless steel and aluminum for the purpose of suppressing electron emission over large surface areas to improve the pulsed high voltage hold-off capabilities of these metals. Improvements to hold-off would be beneficial to the operation of the vacuum-insulator grading rings and final self-magnetically insulated transmission line on the ZR-upgrade machine and other pulsed power applications such as flash radiograph and pulsed-microwave machines. The treatments tested for stainless steel include the Z-protocol (chemical polish, HVFF, and gold coating), pulsed E-beam surface treatments by IHCE, Russia, and chromium oxide coatings. Treatments for aluminum were anodized and polymer coatings. Breakdown thresholds also were measured for a range of surface finishes and gap distances. The study found that: 1.) Electrical conditioning and solvent cleaning in a filtered air environment each improve HV hold-off 30%. 2.) Anodized coatings on aluminum give a factor of two improvement in high voltage hold-off. However, anodized aluminum loses this improvement when the damage is severe. Chromium oxide coatings on stainless steel give a 40% and 20% improvement in hold-off before and after damage from many arcs. 3.) Bare aluminum gives similar hold-off for surface roughness, R a , ranging from 0.08 to 3.2 µm. 4.) The various EBEST surfaces tested give high voltage hold-off a factor of two better than typical machined and similar to R a = 0.05 µm polished stainless steel surfaces. 5.) For gaps > 2 mm the hold-off voltage increases as the square root of the gap for bare metal surfaces. This is inconsistent with the accepted model for metals that involves E-field induced electron emission from dielectric inclusions. Micro-particles accelerated across the gap during the voltage pulse give the observed voltage dependence. However the similarity in observed breakdown times for large and small gaps places a requirement that the particles be of molecular size. This makes accelerated micro-particle induced breakdown seem improbable also. 4

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Measurement of electron energy deposition necessary to form an anode plasma in Ta, Ti, and C for coaxial bremsstrahlung diodes

Cited by 87 publications

References 18 publications

Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

A megavolt test stand for measuring cathode and anode emissions with nanosecond pulses

Suppression of electron emission from metal electrodes : LDRD 28771 final report.

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