Emission properties of different cathodes at E⩽105 V/cm

Krasik, Ya. E.; Dunaevsky, A.; Krokhmal, A.; Felsteiner, J.; Gunin, A. V.; Pegel, I. V.; Korovin, S. D.

doi:10.1063/1.1337924

Cited by 163 publications

(72 citation statements)

References 23 publications

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“…Thus, this outgassing phenomenon deteriorates the vacuum in diode chamber and shortens the effective diode gap, which represented natural limits for cathode lifetime ( 10 5 shots), pulse duration ( 10 À6 s), and maximum pulse repetition rate. 16,17 Surface coating with cesium iodide (CsI) on polymer velvet cathode is an alternative and effective strategy to reduce outgassing levels and decrease plasma expansion velocity, due to the low ionization potential and high mass of cesium. 9,18,19 However, the hygroscopicity and oxidizability of CsI in the atmosphere, 20,21 especially in the humid environment, restricted its wide application.…”

Section: Introductionmentioning

confidence: 99%

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

et al. 2013

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The effect of surface Mo coating on the high-current electron emission performances for polymer velvet cathode has been investigated in a diode with A-K gap of 11.5 cm by the combination of time-resolved electrical diagnostic and temporal pressure variation. Compared with uncoated polymer velvet cathode under the single-pulsed emission mode, the Mo-coated one shows lower outgassing levels ($0.40 Pa L), slower cathode plasma expansion velocity ($2.30 cm/ls), and higher emission stability as evidences by the change in cathode current, temporal pressure variation, and diode perveance. Moreover, after Mo coating, the emission consistency of the polymer velvet cathode between two adjacent pulses is significantly improved in double-pulsed emission mode with $500 ns interval between two pulses, which further confirms the effectiveness of Mo coating for enhancement of electron emission performance of polymer velvet cathodes. These results should be of interest to the high-repetitive high-power microwave systems with cold cathodes. V C 2013 AIP Publishing LLC. [http://dx.

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Section: Introductionmentioning

confidence: 99%

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

et al. 2013

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“…31 Furthermore, many experiments have been carried out to investigate the temporal and spatial variations of the cathode plasma by using the imaging methods. 13,30 However, in the previous studies, most documents provided only a qualitative and phenomenological pattern of the luminosity of the diode process. More accurate and valuable information about the dynamics of the cathode plasma could be acquired by utilizing digital image processing methods.…”

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confidence: 95%

“…26,27 However, the model should be modified according to real conditions. 16,20,[28][29][30] Additionally, the spatial distribution difference of the cathode plasma was neglected in the perveance model. 31 Furthermore, many experiments have been carried out to investigate the temporal and spatial variations of the cathode plasma by using the imaging methods.…”

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confidence: 99%

Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes

Yang

Shu

Yang

2013

Journal of Applied Physics

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Time-and-space resolved comparison of the expansion velocities of plasmas in the planar diode with cathodes made of carbon velvet and polymer velvet has been performed. The diode was powered by a 200 kV, 110 ns pulse, and the peak current density was nearly 477 A/cm2. A four-channel high speed framing camera (HSFC) was used to observe the formation and subsequent movement of the cathode plasmas. More accurate and valuable information about the two-dimensional (radial and axial) velocity components of the cathode plasmas was also acquired by utilizing the digital image processing methods. Additionally, the perveance model based on the Child-Langmuir law was used to calculate the expansion velocities of the diode plasmas from voltage and current profiles. Results from the two diagnostics were compared. Comparing the average values of the radial and axial velocity components indicated that the former was much larger than the latter during the initial period of the current. It was also found that the radial velocity of the carbon velvet cathode (190 cm/μs) was much larger than that (90 cm/μs) of the polymer velvet cathode. Moreover, the average values of both the radial and axial velocity components of the carbon velvet cathode were typically in the range of 2.5 ± 1.5 cm/μs, which were smaller than that of the polymer velvet cathode during the current flattop. These results, together with the comparison of calculated values from the perveance model, indicated that the diode with carbon velvet cathode was more robust as compared with the polymer velvet cathode for the same electron current densities.

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“…Velvet is one of the materials for explosive electron emission (EEE) in intense electron beam sources [1][2][3]. The velvet cathode generates uniform cathode plasma during the emission process under pulsed high voltage.…”

Section: Introductionmentioning

confidence: 99%

Plasma-induced field emission study of carbon nanotube cathode

Shen

Xia

Zhang

et al. 2011

Phys. Rev. ST Accel. Beams

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An investigation on the plasma-induced field emission (PFE) properties of a large area carbon nanotube (CNT) cathode on a 2 MeV linear induction accelerator injector is presented. Experimental results show that the cathode is able to emit intense electron beams. Intense electron beams of 14:9-127:8 A=cm 2 are obtained from the cathode. The CNT cathode desorbs gases from the CNTs during the PFE process. The fast cathode plasma expansion affects the diode perveance. The amount of outgassing is estimated to be 0:06-0:49 Pa Á L, and the ratio of outgassing and electron are roughly calculated to be within the range of 170-350 atoms per electron. The effect of the outgassing is analyzed, and the outgassing mass spectrum of the CNT cathode has been studied during the PFE. There is a significant desorption of CO 2 , N 2 ðCOÞ, and H 2 gases, which plays an important role during the PFE process. All the experiments demonstrate that the outgassing plays an important role in the formation of the cathode plasma. Moreover, the characteristic turn-on time of the CNT cathode was measured to be 39 ns.

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Emission properties of different cathodes at E⩽105 V/cm

Cited by 163 publications

References 23 publications

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes

Plasma-induced field emission study of carbon nanotube cathode

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