Plasma-induced field emission and the characteristics of high-current relativistic electron flow

Parker, Robert K.; Anderson, Richard E.; Duncan, Charles V.

doi:10.1063/1.1663615

Cited by 203 publications

(47 citation statements)

References 20 publications

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“…The rapid merging of the resultant flares forms a plasma sheath covering the entire cold cathode surface which then moves toward the anode at a constant rate in the range 2-3 cm/gs [23]. Since emission is now taking place from the surface of this plasma, its movement corresponds to a decrease in the effective gap of the diode.…”

Section: Flash X-ray Production Capabilities With 100 Ps Switchingmentioning

confidence: 99%

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Low-Impedance Compact Modulators Capable of Generating Intense Ultra-fast Rising Nanosecond Waveforms

Collins¹,

Davanloo²

2006

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Section: Flash X-ray Production Capabilities With 100 Ps Switchingmentioning

confidence: 99%

“…A self-consistent description of the dominant processes acting within a non-pinching cold-cathode diode at high currents has been provided by others [23].…”

Section: Flash X-ray Production Capabilities With 100 Ps Switchingmentioning

confidence: 99%

Low-Impedance Compact Modulators Capable of Generating Intense Ultra-fast Rising Nanosecond Waveforms

Collins¹,

Davanloo²

2006

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“…The plasma then becomes a virtual cathode that expands toward the anode effectively shortening the gap distance. The closure rate can be as fast as 1-3 cm/lsec [13]. This gap closure rate can slow as the cathode plasma expands through the gap and becomes more tenuous [141.…”

Section: Gap Closurementioning

confidence: 99%

Characterization of carbon fiber flocked cathode materials

Visosky

Advani²,

Bekefi³

et al. 1996

IEEE Conference Record - Abstracts. 1996 IEEE International Conference on Plasma Science

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The pulsed performance of carbon fiber electroflocked cathodes, produced by ESLI, are reported. Performance characteristics include, normalized emittance and normalized brightness of the resultant electron beam, and turn-on field and longevity of the cathodes. The three cathodes tested were made with PAN derived carbon fibers of lengths 0.020", 0.050", and 0.100". The fibers were 7-8 jpm in diameter and were electroflocked on a POCO graphite substrate with a fiber packing density of -60,000 fibers/cm 2 . They were tested using fields ranging from 60 to 110 kV/cm with pulses of -200 ns in duration. These tests were conducted at a vacuum pressure of 4x10 6 torr. Additional longevity tests were conducted with fields of-10 kV/cm, at a repetition rate of -2.5 Hz, and at a pressure of 8x10-5 torr.All three cathodes turned on at a field of <10 kV/cm. The resultant electron beams had emittances ranging from 0.015 to 0.07 (7 cm rad) and brightnesses ranging from 4x10 4 to 3x10 5 A/cm 2 rad 2 . There was no observed loss of performance in either of the two longevity experiments conducted. These results are compared to a POCO graphite cathode that was tested in this experiment, and with velvet cathodes tested in other studies. The PAN fiber cathodes tested have performance comparable to velvet cathodes used in other experiments.

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“…Magnetic insulation in the vacuum section of these systems is critical, given that the electric field generated between the conductors of the transmission line will usually result in the spacecharge-limited (SCL) emission of electrons from the line's cathode electrode [1,2]. Although the cathode in a vacuum line will freely emit electrons under such electric stress, the self-magnetic field of the transmission line's current inhibits the electrons from reaching the anode .…”

Section: Introductionmentioning

confidence: 99%

Tailoring of electron flow current in magnetically insulated transmission lines

Martin

Savage

Pointon

et al. 2009

Phys. Rev. ST Accel. Beams

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It is desirable to optimize (minimizing both the inductance and electron flow) the magnetically insulated vacuum sections of low impedance pulsed-power drivers. The goal of low inductance is understandable from basic efficiency arguments. The goal of low electron flow results from two observations: (1) flowing electrons generally do not deliver energy to (or even reach) most loads, and thus constitute a loss mechanism; (2) energetic electrons deposited in a small area can cause anode damage and anode plasma formation. Low inductance and low electron flow are competing goals; an optimized system requires a balance of the two. While magnetically insulated systems are generally forgiving, there are times when optimization is crucial. For example, in large pulsed-power drivers used to energize high energy density physics loads, the electron flow as a fraction of total current is small, but that flow often reaches the anode in relatively small regions. If the anode temperature becomes high enough to desorb gas, the resulting plasma initiates a gap closure process that can impact system performance. Magnetic-pressure driven (z pinches and material equation of state) loads behave like a fixed inductor for much of the drive pulse. It is clear that neither fixed gap nor constant-impedance transmission lines are optimal for driving inductive loads. This work shows a technique for developing the optimal impedance profile for the magnetically insulated section of a high-current driver. Particle-in-cell calculations are used to validate the impedance profiles developed in a radial disk magnetically insulated transmission line geometry. The input parameters are the spacing and location of the minimum gap, the effective load inductance, and the desired electron flow profile. The radial electron flow profiles from these simulations are in good agreement with theoretical predictions when driven at relatively high voltage (i.e., V ! 2 MV).

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Plasma-induced field emission and the characteristics of high-current relativistic electron flow

Cited by 203 publications

References 20 publications

Low-Impedance Compact Modulators Capable of Generating Intense Ultra-fast Rising Nanosecond Waveforms

Low-Impedance Compact Modulators Capable of Generating Intense Ultra-fast Rising Nanosecond Waveforms

Characterization of carbon fiber flocked cathode materials

Tailoring of electron flow current in magnetically insulated transmission lines

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