Light Emission From CsI-Coated Carbon Velvet Cathodes Under Varied Conditions

Lynn, C.; Neuber, A.; Walter, J.; Dickens, J.; Kristiansen, M.

doi:10.1109/tps.2012.2218624

Cited by 15 publications

(7 citation statements)

References 12 publications

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“…Over recent years, research into these diodes has focused on various cathode materials [1]- [5] and geometries [6]- [8] in order to optimize the electron beam uniformity. Carbon fiber cathodes have shown many favorable characteristics, including low electric field threshold for the onset of electron emission, excellent emission uniformity, minimal plasma expansion velocity, and lifetimes exceeding 10 6 shots [1]- [5].…”

Section: Introductionmentioning

confidence: 99%

Anode Materials for High-Average-Power Operation in Vacuum at Gigawatt Instantaneous Power Levels

Lynn

Parson

Scott

et al. 2015

IEEE Trans. Electron Devices

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The thermal behavior of several electrically conducting solids under high incident electron fluence in high vacuum was evaluated. At electron energies of up to ∼200 keV, the depth-dose relationship for electron penetration into the materials was considered, and the resulting energy deposition profile from the surface was revealed to extend to a maximum of ∼175 µm below the surface depending on the anode material. Black body radiation is considered as the major mechanism that balances the power deposited in the material on the timescales of interest. Comparing the radiated power density at the sublimation temperature for different materials, metallic/nonmetallic, revealed that pyrolytic graphite anodes may radiate over 20 times more power than metallic anodes before failure due to sublimation. In addition, transparent pyrolytic graphite anodes (with a thickness on the order of several tens of micrometer) potentially radiate up to 40 times that of metallic anodes, since heating by the electron beam is approximately uniform throughout the thickness of the material, thus radiation is emitted from both sides. Experimental results obtained from titanium and pyrolytic graphite anodes validate the thermal analysis.

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Section: Introductionmentioning

confidence: 99%

Anode Materials for High-Average-Power Operation in Vacuum at Gigawatt Instantaneous Power Levels

Lynn

Parson

Scott

et al. 2015

IEEE Trans. Electron Devices

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“…Cathode imaging has been performed to characterize the cathode physics on a number of diodes that can be separated into two categories: the first being diodes with < 1.6 and < 0.78 and A-K gaps ranging from 0.8-5 cm [15][16][17][18][19] and the second are relativistic diodes with > 4.9 and > 0.98 with A-K gaps > 8 cm [20,21]. Refs.…”

Section: Introductionmentioning

confidence: 99%

“…Refs. [15][16][17][18][19] characterize the emission properties, uniformity and outgassing of cathodes in short A-K gaps where the electrons are terminated into a solid anode and an anode plasma is present. The relativistic diodes are used to produce intense electron beams that are accelerated through a hollow anode and transported into a linear induction accelerator.…”

Section: Introductionmentioning

confidence: 99%

Characterizing the photon spectrum in the DARHT Axis-I diode

Coleman¹,

Johnson²,

McCuistian³

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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An array of photon diagnostics have been deployed on a high power relativistic electron beam diode. Surface flashover of a carbon fiber velvet cathode generates a discharge from which electrons are accelerated through a 17.8 cm diode. This discharge is assumed to be a hydrocarbon mixture. A small portion of the off energy electrons (1-3 MeV) accelerated during the rise and fall of the 80 ns FWHM pulse impact the beam pipe and generate a Bremsstrahlung spectrum of 0.1-3 MeV photons. The principal objective of these experiments is to quantify the dynamics of the hard X-ray and -ray flux generated in the diode region, in addition to quantifying dynamics of the visible photons generated, and the ion species of the surface discharge on the velvet cathode. A qualitative comparison of different diagnostic results are presented, which include time resolved measurements with X-ray PIN diodes, a PMT, and CCD images. In addition initial visible spectroscopy measurements will also be presented.

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“…Cs-I doped carbon velvet has been explored by refs. [2,9] to mitigate gap closure, in relatively small diodes (~8 mm) with voltages >100 kV and currents >2 kA. Gap closure measurements have been performed on the KALI 5000, 3 cm diode with voltages up to 430 kV and currents of 17 kA [10].…”

Section: Introductionmentioning

confidence: 99%

“…DARHT Axis-1 is unique for these studies because it has a relatively large A-K gap and does not have a solid or perforated anode as refs [2,9,10,12,13], reducing the contribution of the anode plasma to the gap closure velocity. Initial estimates indicate the closure velocity for this relativistic diode is ~ 10 cm/µs.…”

Section: Introductionmentioning

confidence: 99%

Explosive emission and gap closure from a relativistic electron beam diode

Coleman

Moir

Ekdahl

et al. 2013

2013 19th IEEE Pulsed Power Conference (PPC)

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Explosive emission cathode studies are currently being conducted on a high power relativistic electron beam diode. A black velvet cathode is driven with a 75 Ohm graded transmission line, which provides a 3.8 MV, 80 ns (FWHM) pulse across a fixed A-K gap of 17.8 cm. Cathode sizes range from 1.9 -7 cm with space-charge limited currents of 0.26 -3 kA. The principal objective of these experiments is to quantify the current emission limits and the dynamics of the gap closure process. A qualitative comparison of experimental and calculated results are presented, which included the I-V relationship, impedance and perveance curves, plasma expansion velocity, and the time-resolved light emission on the surface of the cathode.

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Light Emission From CsI-Coated Carbon Velvet Cathodes Under Varied Conditions

Cited by 15 publications

References 12 publications

Anode Materials for High-Average-Power Operation in Vacuum at Gigawatt Instantaneous Power Levels

Anode Materials for High-Average-Power Operation in Vacuum at Gigawatt Instantaneous Power Levels

Characterizing the photon spectrum in the DARHT Axis-I diode

Explosive emission and gap closure from a relativistic electron beam diode

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