High-Speed Camera Imaging of the Ignition Process in a Heaterless Hollow Cathode

Zhang, Hai-Guang; Ning, Zhiliang; Ding, Yongjie; Zhu, Xi-Ming; Jiang, Binhao; Yu, Daren

doi:10.1109/tps.2018.2885380

Cited by 7 publications

(4 citation statements)

References 15 publications

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“…The first grid is suspended, the second grid is loaded with a voltage of −24 V for repelling electrons, the third grid is loaded with a linearly varying voltage of 0-140 V at 1 Hz and the fourth grid is loaded with a voltage of −24 V near the collector to suppress secondary electron emission. A high-speed camera [27] was used to shoot the plume area discharge oscillation. The effects of heating on the discharge characteristics of the hollow cathode were analyzed in combination with the various diagnostic means above.…”

Section: Experimental Equipment and Methodsmentioning

confidence: 99%

Influence of heating on the discharge characteristics of a hollow cathode

Hu¹,

Ning

Liu

et al. 2019

Plasma Sci. Technol.

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Hollow cathodes are widely used as electron sources and neutralizers in ion and Hall electric propulsion. Special applications such as commercial aerospace and gravitational wave detection require hollow cathodes with a very wide discharge current range. In this paper, a heater is used to compensate for the temperature drop of the emitter at low current. The self-sustained current can be extended from 0.6 to 0.1 A with a small discharge oscillation and ion energy when the flow rate is constant. This is also beneficial for long-life operation. However, when the discharge current is high (>1 A), heating can cause discharge oscillation, discharge voltage and ion energy to increase. Further, combined with a rapid decline of pressure inside the cathode and an increase in the temperature in the cathode orifice plate, electron emission in the orifice and outside the orifice increases and the plasma density in the orifice decreases. This leads to a change in the cathode discharge mode.

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Section: Experimental Equipment and Methodsmentioning

confidence: 99%

Influence of heating on the discharge characteristics of a hollow cathode

Hu¹,

Ning

Liu

et al. 2019

Plasma Sci. Technol.

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“…To ignite the cathode, the heater was first heated with 7 A current to preheat the emitter above 1650 • C, after which a 210 V voltage was applied to the keeper electrode to initiate gas breakdown within the 1 mm gap. Then the seed plasma would diffuse into the emitter cavity [14] and establish self-sustained thermionic emission enhanced by high-density plasma, under the powered DC discharge between the cathode and the anode plate. After ignition, the keeper electrode was disconnected from the high-voltage supply and kept electrically floating.…”

Section: Hollow Cathodementioning

confidence: 99%

Presence and statistics of a discontinuous potential distribution in the plume of an electric propulsion hollow cathode

Meng

Ning

et al. 2023

Plasma Sources Sci. Technol.

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The extraction voltage of electric propulsion hollow cathode is mainly deposit in its plume region, and is usually believed to be proportional to plasma oscillation amplitude. However, this was not the case in some recent results. To specify the reason, this paper probe measured the potential distribution and oscillation amplitude distribution in the plume of a hollow cathode, and checked whether the two were relevant during the changes in keeper materials and keeper biases. We found a discontinuous potential rise (‘step region’) in the middle of plume, of which the voltage occupied over 40% of the total discharge voltage. The step region was sensitive to exterior electron emission, and could shift its location in a ~18mm range according to increase / decrease of oscillation amplitude. However, its voltage remained almost unchanged, as a result, the total extraction voltage remained still regardless of amplitude changes. Statistics indicated that the step region was related to electon-electron non-equilibrium, with splitting and recombination between EEPF multi-components, each at different flow states and trapping states. It was suspected that shockwaves and streaming instabilities were involved. Because the step region was accompanied by stronger oscillations and higher ion energies, inclusion of this plasma structure should be necessary to promote cathode test accuracy.

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“…Different initiation properties are exhibited when the heater is removed with respect to the conventional hollow cathode. HHC can be ignited in a few tens of microseconds, after which the entire cathode plasma and temperature distribution transitions to a steady state of operation in a few tens of seconds [5]. In this process, the coupling between cathode and plasma strongly governs the ignition and heating of the cathode.…”

Section: Introductionmentioning

confidence: 99%

Temperature measurement and simulation analysis of heaterless hollow cathode during start-up process

Han¹,

An²,

Liu³

et al. 2022

J. Phys. D: Appl. Phys.

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Monochromatic radiation thermometry is used to quantify temperature distribution during the start-up process for a heaterless hollow cathode. A transparent cathode is designed to facilitate the transmission of thermally and spontaneously radiated photons from the interior of the structure and their reception by the detection equipment. The relative radiation intensities can be obtained by the developed measurement equipment, which consists of an sCMOS camera and a 780 nm narrow-band filter, and then transformed into temperature distributions calibrated by a two-color pyrometer. The current and voltage characteristics of the anode and keeper and plasma image captured by the high-speed camera are used to analyze the thermal evolution mechanism. A 2-D extended fluid model coupling with a thermal model is also developed and used to help clarify the thermal deposition variation at different locations. These results provide further support for the hypothesis that thermal deposition of ions and electrons, thermal conduction, and thermal radiation all affect the rate of change in temperature of various components.

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High-Speed Camera Imaging of the Ignition Process in a Heaterless Hollow Cathode

Cited by 7 publications

References 15 publications

Influence of heating on the discharge characteristics of a hollow cathode

Influence of heating on the discharge characteristics of a hollow cathode

Presence and statistics of a discontinuous potential distribution in the plume of an electric propulsion hollow cathode

Temperature measurement and simulation analysis of heaterless hollow cathode during start-up process

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