Evaluating the Performance of a Carbon-Epoxy Capillary Cathode and Carbon Fiber Cathode in a Sealed-Tube Vircator Under UHV Conditions

Rocha, E.; Kelly, P.M.; Parson, Jonathan M.; Lynn, C.; Dickens, J.; Neuber, A.; Mańkowski, J.; Queller, T.; Gleizer, J. Z.; Krasik, Yakov E.

doi:10.1109/tps.2015.2439680

Cited by 16 publications

(4 citation statements)

References 17 publications

(28 reference statements)

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“…The meshed model was imported into the Pegasus software [29]. In the simulation, a non-evaporable getter (NEG) [30,31] with a pumping speed of 180 L/s was set at the diode port, and a gas source with a constant gas flow rate of 10 21 molecules/s.m 2 was set on the cathode surface. This gas flow rate N w corresponded to the experimental pressure.…”

Section: Proposed Dynamic Pumping Modelmentioning

confidence: 99%

A Dynamic Pumping Model for a Vacuum-Sealed Gigawatt Repetitively Operated High-Power Microwave Source

et al. 2022

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In this study, a dynamic pumping model was established for a vacuum-sealed, gigawatt-class, repetitively operated transit-time oscillator (TTO) based on the direct-simulation Monte Carlo (DSMC) method, and the pressure distribution of the model at different times and locations was analyzed. The simulation results showed that the maximum pressure at the diode was an order of magnitude larger than the equilibrium pressure, and the pressure recovery time was three times the duration of a single pulse. To verify the accuracy of the simulation results, experiments were conducted in a vacuum-sealed hard-tube TTO structure with a repetition rate of 10 Hz and the pressure was monitored at the vacuum diode. The diode voltage was about 500 kV and the beam current was 8 kA. Further, the average microwave power was 1 GW with a pulse width of 40 ns. The experimental results revealed that the equilibrium pressure at the vacuum diode was 4.0 × 10−3 Pa, and the pressure recovery time was three times the duration of a single pulse. These results were consistent with the simulation results, which indicates that the proposed model can provide technical support for subsequent vacuum-maintenance experiments.

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Section: Proposed Dynamic Pumping Modelmentioning

confidence: 99%

A Dynamic Pumping Model for a Vacuum-Sealed Gigawatt Repetitively Operated High-Power Microwave Source

et al. 2022

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“…Researchers have studied vircators to improve their low efficiency, analyze the modulation characteristics of the output frequency, and enhance the output power. Various types of vircators, such as the axial vircator, reflex triode vircator, and coaxial vircator, have been studied to improve the shortcomings of vircators [5][6][7][8]. In addition to studying the various types of vircators, reflectors, resonators, and various cathode structures have been studied by utilizing resonant mechanisms and varying the electron emission to increase vircator efficiency [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Investigation of an Axial Virtual Cathode Oscillator with an Open-Ended Coaxial Cathode

Kim

Lee

Kim

et al. 2022

J Electromagn Eng Sci

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A cathode with an open-ended coaxial structure is experimentally investigated using an axial virtual cathode oscillator (vircator). To enhance the microwave power output, an open-ended coaxial cathode is installed in the axial vircator. The proposed cathode is designed based on the reciprocating frequency of the vircator. The operation features of an axial vircator with a solid cathode, an annular cathode, and an open-ended coaxial cathode are comparatively analyzed through simulations and experiments. Three cathodes are machined using graphite. A stainless steel mesh with a transparency of 70% is used as an anode. The anode-to-cathode gap is fixed to 6 mm. The vircator is driven using a 10-stage PFN-Marx generator with a characteristic impedance of 31 Ω. The PFN-Marx generator applies -150 kV voltage pulses with a 170–200 ns pulse width into the vircator. The microwave power from the solid and annular cathodes is 11.22 MW and 11.27 MW, respectively. The proposed cathode generates a microwave with a power of 12.65 MW while enhancing the microwave power by 13% compared with the solid and annular cathodes. The proposed cathode shows a frequency shift to 3.4 GHz, which is a much lower frequency than that of the solid cathode at 6.34 GHz.

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“…However, the vircator has relatively low efficiencies (typically ≈5%) compared with other HPM devices. A vircator is widely investigated in academic fields to improve its low efficiencies and modulate its output frequency by installing additional structures and changing the cathode and anode materials [8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Operation Features of a Coaxial Virtual Cathode Oscillator Emitting Electrons in the Outer Radial Direction

et al. 2021

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The operation features of the coaxial virtual cathode oscillator emitting electrons in the outer radial direction were investigated through simulations and experiments. A coaxial vircator was compared with an axial vircator when the anode to cathode distance of both vircators was 6 mm. The proposed coaxial vircator was operated when the anode to cathode distance was 5 mm, 6 mm, and 7 mm. The peak power and frequency of the microwave generated from the proposed coaxial vircator when the anode to cathode distance was 6 mm were 20.18 MW and 6.17 GHz, respectively. The simulations and experiments show that the proposed coaxial vircator generates 80% more microwave power than the axial vircator with the same anode to cathode distance. According to the simulations and experiments, the proposed coaxial vircator tends to generate a higher power average when the anode to cathode distance was larger than 5 mm. The frequency of the proposed coaxial vircator when the anode to cathode distance was 5 mm and 7 mm was approximately 8 GHz and 5 GHz, respectively. The geometric factor of the proposed coaxial vircator was considered to be the reason for the greater microwave power generation than the axial vircator. The frequency of the proposed coaxial vircator decreases inversely proportional with the anode to cathode distance as observed in the axial and basic coaxial vircators.

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Evaluating the Performance of a Carbon-Epoxy Capillary Cathode and Carbon Fiber Cathode in a Sealed-Tube Vircator Under UHV Conditions

Cited by 16 publications

References 17 publications

A Dynamic Pumping Model for a Vacuum-Sealed Gigawatt Repetitively Operated High-Power Microwave Source

A Dynamic Pumping Model for a Vacuum-Sealed Gigawatt Repetitively Operated High-Power Microwave Source

Investigation of an Axial Virtual Cathode Oscillator with an Open-Ended Coaxial Cathode

Operation Features of a Coaxial Virtual Cathode Oscillator Emitting Electrons in the Outer Radial Direction

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