Journal of Radio Electronics. eISSN 1684-1719. 2025. ¹11

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DOI: https://doi.org/10.30898/1684-1719.2025.11.19

17th International Conference

Gas Discharge Plasmas and Their Applications

Ekaterinburg, Russia, 8-12 September 2025

 

 

 

Dimensions of near-cathode plasma regions –

sources of runaway electrons –

under conditions of a sharply inhomogeneous

electric field

 

N.M. Zubarev 1,2, O.V. Zubareva 1, M.I. Yalandin 1,2

 

1 Institute of Electrophysics UB RAS, 620016, Russia, Yekaterinburg, Amundsen str., 106

2 P.N. Lebedev Physical Institute RAS, 119991, Russia, Moscow, Leninskii av., 53

 

The paper was received October 2, 2025.

 

Abstract. We analyzed experimental results on electron runaway conditions in air diodes with weakly and strongly inhomogeneous electric field distributions, caused by the use of graphite cathodes of various shapes: a cone with an opening angle of ~100° and thin needles. To interpret the data on threshold voltages for runaway electron generation, it was necessary to assume that the main electron flow is emitted from the outer boundary of the forming near-cathode plasma region. Estimates were made for the dimensions of this region, which, as it turns out, correlate with the observed transverse scales of magnetized runaway electron beams at the anode. For a conical cathode, the size is tens of micrometers, while for needle cathodes, it is an order of magnitude larger–hundreds of micrometers. Such a significant difference is explained by the different nature of the plasma regions. For a cone, i.e., in a relatively weakly inhomogeneous field, the appearance of plasma is due to the development of Townsend avalanches of thermal electrons. For needles, i.e., in a sharply inhomogeneous field, the appearance of a substantially more extended plasma layer can be associated with “incomplete” electron runaway. They begin to run away near the cathode tip at the leading edge of the voltage pulse–long before reaching its peak–but then lose energy and turn into thermal electrons at some distance from the cathode, thereby initiating plasma formation.

Key words: air diode, runaway electrons, cone- and needle-shaped cathodes, near-cathode plasma.

Corresponding author: Zubareva Olga Vladimirovna, olga@iep.uran.ru

 

References

1. Wilson C.T.R. The electric field of a thundercloud and some of its effects // Proceedings of the Physical Society of London. – 1924. – V. 37. – ¹ 1. – P. 32D. https://doi.org/10.1088/1478-7814/37/1/314

2. Dreicer H. Electron and ion runaway in a fully ionized gas. I // Physical Review. – 1959. – V. 115. – ¹ 2. – P. 238. https://doi.org/10.1103/PhysRev.115.238

3. Gurevich A.V. On the theory of runaway electrons // Sov. Phys. JETP. – 1961. – V. 12. – ¹ 5. – P. 904-912.

4. Stankevich Y.L., Kalinin V.G. Fast electrons and X-ray radiation during the initial stage of growth of a pulsed spark discharge in air // Soviet Physics Doklady. – 1968. – V. 12. – P. 1042.

5. Mesyats G.A., Bychkov Y.I., Kremnev V.V. Pulsed nanosecond electric discharges in gases // Soviet Physics Uspekhi. – 1972. – V. 15. – ¹ 3. – P. 282. https://doi.org/10.1070/PU1972v015n03ABEH004969

6. Dwyer J.R., Smith D.M., Cummer S.A. High-energy atmospheric physics: Terrestrial gamma-ray flashes and related phenomena // Space Science Reviews. – 2012. – V. 173. – ¹ 1. – P. 133-196. https://doi.org/10.1007/s11214-012-9894-0

7. Babich L.P., Loĭko T.V., Tsukerman V.A. High-voltage nanosecond discharge in a dense gas at a high overvoltage with runaway electrons // Soviet Physics Uspekhi. – 1990. – V. 33. – ¹ 7. – P. 521. https://doi.org/10.1070/PU1990v033n07ABEH002606

8. Babich L.P. High-energy phenomena in electric discharges in dense gases: Theory, experiment, and natural phenomena. – Futurepast Incorporated, 2003.

9. Zubarev N.M., Mesyats G.A., Yalandin M.I. Conditions for runaway electrons in a gas diode with a strongly nonuniform electric field // JETP Letters. – 2017. – V. 105. – ¹ 8. – P. 537-541. https://doi.org/10.1134/S002136401708015X

10. Zubarev N.M., Zubareva O.V., Yalandin M.I. Specific Features of Electron Runaway in a Gas Gap with a Conical Cathode // Doklady Physics. – Moscow : Pleiades Publishing, 2023. – V. 68. – ¹ 9. – P. 279-283. https://doi.org/10.1134/S1028335823090070

11. Kozyrev A.V. et al. Local and nonlocal conditions for electron runaway in a gas gap with a conical cathode with a variable opening angle // Physics of Plasmas. – 2024. – V. 31. – ¹ 10. – P. 103109. https://doi.org/10.1063/5.0225881

12. Zubarev N.M., Mesyats G.A., Yalandin M.I. Conditions for the generation of runaway electrons in an air gap with an inhomogeneous electric field: theory and experiment // Physics–Uspekhi. – 2024. – V. 67. – ¹ 8. – P. 803-813. https://doi.org/10.3367/UFNe.2023.11.039608

13. Belomyttsev S.Y. et al. Initial stage of gas discharge in an inhomogeneous electric field // Technical Physics Letters. – 2008. – V. 34. – ¹ 5. – P. 367-369. https://doi.org/10.1134/S1063785008050027

14. Levko D. et al. Numerical simulations of runaway electron generation in pressurized gases // Journal of Applied Physics. – 2012. – V. 111. – ¹ 1. – P. 013303. https://doi.org/10.1063/1.3675527

15. Mesyats G.A. et al. How short is the runaway electron flow in an air electrode gap? // Applied Physics Letters. – 2020. – V. 116. – ¹ 6. – P. 063501. https://doi.org/10.1063/1.5143486

16. Zubarev N.M. et al. Mechanism and dynamics of picosecond radial breakdown of a gas-filled coaxial line // Plasma Sources Science and Technology. – 2020. – V. 29. – ¹ 12. – P. 125008. https://doi.org/10.1088/1361-6595/abc414

17. Yalandin M.I. et al. High peak power and high average power subnanosecond modulator operating at a repetition frequency of 3.5 kHz // IEEE Transactions on Plasma Science. – 2002. – V. 30. – ¹ 5. – P. 1700-1704. https://doi.org/10.1109/TPS.2002.805383

18. Shpak V.G., Shunailov S.A., Yalandin M.I. The 40 years to RADAN – compact multi-purposed sources for various pulsed power investigations // J. Phys.: Conf. Ser. – 2021. – V. 2064. – P. 012002. https://doi.org/10.1088/1742-6596/2064/1/012002

19. Tarakanov V.P. Code KARAT in simulations of power microwave sources including Cherenkov plasma devices, vircators, orotron, E-field sensor, calorimeter etc // EPJ Web of Conferences. – EDP Sciences. – 2017. – V. 149. – P. 04024. https://doi.org/10.1051/epjconf/201714904024

20. Yalandin M.I. et al. Picosecond resolution collector sensor for diagnostics of subrelativistic electron bunches // IEEE Transactions on Instrumentation and Measurement. – 2023. – V. 72. – P. 1008808. https://doi.org/10.1109/TIM.2023.3307183

21. Taylor G.I. Disintegration of water drops in an electric field // Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. – 1964. – V. 280. – ¹ 1382. – P. 383-397. https://doi.org/10.1098/rspa.1964.0151

22. Zubarev N.M. The effect of viscosity on the self-similar growth of conic cusps on the surface of a conducting liquid in an electric field: Limiting cone angle // Physics of Fluids. – 2024. – V. 36. – ¹ 4. – P. 042102. https://doi.org/10.1063/5.0200820

23. Tiunov M.A., Fomel B.M., Yakovlev V.P. SAM–An interactive code for electron gun evaluation // Technical Report ¹ INP-89-159. – 1989.

24. Bethe H. Zur theorie des durchgangs schneller korpuskularstrahlen durch materie // Annalen der Physik. – 1930. – V. 397. – ¹ 3. – P. 325-400. https://doi.org/10.1002/andp.19303970303

25. Peterson L.R., Green A.E.S. The relation between ionization yields, cross sections and loss functions // Journal of Physics B: Atomic and Molecular Physics. – 1968. – V. 1. – ¹ 6. – P. 1131. https://doi.org/10.1088/0022-3700/1/6/317

26. Mesyats G.A. Similarity laws for pulsed gas discharges // Physics–Uspekhi. – 2006. – V. 49. – ¹ 10. – P. 1045. https://doi.org/10.1070/PU2006v049n10ABEH006118

27. Mamontov Y.I., Yalandin M.I., Zubarev N.M. Simulation of runaway electron kinetics in magnetized gas diodes with a strongly inhomogeneous electric field // Physics of Plasmas. – 2025. – V. 32. – ¹ 5. – P. 053502. https://doi.org/10.1063/5.0273887

For citation:

Zubarev N.M., Zubareva O.V., Yalandin M.I. Dimensions of near-cathode plasma regions – sources of runaway electrons – under conditions of a sharply inhomogeneous electric field // Journal of Radio Electronics. – 2025. – ¹. 11. https://doi.org/10.30898/1684-1719.2025.11.19 (In Russian)