Glow discharge conditioning of the PDX vacuum vessel

Abstract

A glow discharge technique has been developed and 3 applied to the conditioning of the large (38 m) Poloidal Divertor Experiment (PDX) vacuum vessel. The dis charge parameters and working gas (H ?) were chosen to maximize C and 0 removal and minimize metal sputtering. The glow discharge was produced by biasing one or two internal anodes at 400 V to sustain a discharge current of 2^4 A per anode. Purified H. at a pressure of 3 x10 torr was flowed through PDX at "10 t-a/s. The effectiveness oi the glow discharge conditioning was monitored by measuring impurity gas (CH,, C_H., and CO) exhaust rates by mass spectrometry and C and O surface removal rates by in-situ AES and XPS. Initial glow dis charge operation was accompanied by frequent arcing which subsequenty decreased with time. Low Z (= 2) high power discharges were obtained in PDX after 120 hours of glow discharge treatment, during which more than 100 equi valent monolayers of C and 0 were removed from the vessel.

Dependence of composition of stable molecules in N2–H2plasmas on nitrogen gas flow rate ratio measured using a quartz sensor

“…The signal at m/e = 12 can be attributed to carbon (C) atoms, which originate from carbon monoxide (CO) molecules that are degassed from the chamber inner wall. 42) However, the relationship between the increase in the signal intensity of this species at m/e = 12 and the NQO change is not clear because the viscosities and molecular weights of CO (17.49 © 10 ¹6 Pa0s and 28.0, respectively) and N 2 (17.8 © 10 ¹6 Pa0s and 28.0) are similar. 43) Therefore, the effects of these changes on the NQO change should be minor.…”

Extreme ultraviolet resist outgassing and its effect on nearby optics

“…For this reason, we performed glow discharge plasma cleaning of the chamber with an oxygen/argon gas mixture. This method was previously demonstrated for chamber cleaning in synchrotron and fusion experiments [4][5][6]. For this cleaning, a 0-600V power supply was used through a resistor to limit the maximum current.…”

Oxygen removal with D2-ICR cleanings after oxidation experiment in HT-7

“…Baking would be greatly enhanced by simultaneous or subsequent plasma associated conditioning or intentional disruptive discharges [2]. This is done, for example, by running low energy conditioning plasmas such as glow discharge cleaning (GDC) [3,4], but various other methods based on RF techniques at electron cyclotron resonance (ECR) [5] and ion cyclotron resonance (ICR) have been employed with a permanent toroidal magnetic field, such as in Tore Supra [6], Textor [7] and HT-7 [8,9]. Oxidation experiment with hot walls, which admitted abundant oxygen in to in-vessel, were purposed for removal of a long-term accumulation and high fraction tritium retention in the surface or bulk material of plasma facing components in next step fusion devices, such as ITER [1,[10][11][12][13].…”