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Plasma Sci. Technol. ›› 2018, Vol. 20 ›› Issue (2): 25404-025404.doi: 10.1088/2058-6272/aa8e3f

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Feedback model of secondary electron emission in DC gas discharge plasmas

  

  • 收稿日期:2017-08-06 出版日期:2018-01-11 发布日期:2017-09-21

Feedback model of secondary electron emission in DC gas discharge plasmas

Saravanan ARUMUGAM1, Prince ALEX and Suraj Kumar SINHA   

  1. Department of Physics, Pondicherrry University, Puducherry, 605 014, India
  • Received:2017-08-06 Online:2018-01-11 Published:2017-09-21

Abstract:

Feedback is said to exist in any amplifier when the fraction of output power in fed back as an input. Similarly, in gaseous discharge ions that incident on the cathode act as a natural feedback element to stabilize and self sustain the discharge. The present investigation is intended to emphasize the feedback nature of ions that emits secondary electrons (SEs) from the cathode surface in DC gas discharges. The average number of SEs emitted per incident ion and non ionic species (energetic neutrals, metastables and photons) which results from ion is defined as effective secondary electron emission coefficient (ESEEC,gE). In this study, we derive an analytic expression that corroborates the relation between gE and power influx by ion to the cathode based on the feedback theory of an amplifier. In addition, experimentally, we confirmed the typical positive feedback nature of SEE from the cathode in argon DC glow discharges. The experiment is done for three different cathode material of same dimension (tungsten (W),copper (Cu) and brass) under identical discharge conditions (pressure: 0.45 mbar, cathode bias: -600 V, discharge gab: 15 cm and operating gas: argon). Further, we found that the ?E value of these cathode material controls the amount of feedback power given by ions. The difference in feedback leads different final output i.e the power carried by ion at cathode (P'i∣C). The experimentally obtained value of P'i∣C is 4.28 W, 6.87 W and 9.26 W respectively for W, Cu and brass. In addition, the present investigation reveals that the amount of feedback power in a DC gas discharges not only affect the fraction of power fed back to the cathode but also the entire characteristics of the discharge.

Key words: feedback, secondary electron emission, DC gas discharges, power influx by ion at cathode, cathode temperature

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