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Experimental study of the reduction of field emission by gas injection in vacuum for accelerator applications

Abstract : Field emission current from surfaces under vacuum and at high field strengths can be reduced by the injection of gas into the evacuated volume. In this paper, the effects of H 2 , He, N 2 , and Ar on this "dark" current emitted from a tungsten carbide point cathode for 2 cm gap distance is studied. Exposure to any of these gases at pressures on the order of 10 −3 –10 −2 Pa was found to reduce the emission current by up to 90% with a time constant on the order of ∼1 minute as compared to the current at 10 −6 Pa. The effect was strongly dependent on the gas nature, with Ar and N 2 having larger effects at lower pressures than He and H 2 . The reduction was reversible, with the current increasing to near its original value with a time constant on the order of ∼1–10 minutes after pumping down. The effect of the gas remained in the absence of electric field, whatever the gas pressure. Mechanisms for these and related phenomena are discussed.
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Submitted on : Tuesday, October 28, 2014 - 10:47:04 AM
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K Almaksour, Michael Kirkpatrick, Ph Dessante, E. Odic, A Simonin, et al.. Experimental study of the reduction of field emission by gas injection in vacuum for accelerator applications. Physical Review Special Topics - Accelerators and Beams, 2014, 17, pp.103502. ⟨10.1103/PhysRevSTAB.17.103502⟩. ⟨hal-01078131⟩

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