Effect of surface oxide layers on deuterium permeation through stainless steels with reference to outgassing reduction in ultra- to extremely high vacuum

Ishikawa, Yoshihiro; Yoshimura, Toshihiko; Arai, Masatsugu

doi:10.1016/0042-207x(95)00251-0

Cited by 20 publications

(5 citation statements)

References 30 publications

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“…The reduction in outgassing rate due to the the low temperature bake. Similar behavior seen elsewhere [58,80,81] is postulated to be a result of an oxide-layer diffusion barrier that forms after venting, evacuation and baking. The outgassing rate following the 250 C bake increased to 2.79(0.05)  10 -13 Torr L s -1 cm -2 , higher than the rate following either the 400 C or the 150 C bake.…”

Section: Bare Stainless Steelsupporting

confidence: 62%

Thin film studies toward improving the performance of accelerator electron sources

Mamun

2016

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Future electron accelerators require DC high voltage photoguns to operate beyond the present state of the art to conduct new experiments that require ultra-bright electron beams with high average current and higher bunch charge. To meet these demands, the accelerators must demonstrate improvements in a number of photogun areas including vacuum, field emission elimination in high voltage electrodes, and photocathodes. This dissertation illustrates how these improvements can be achieved by the application of suitable thin-films to the photogun structure for producing ultra-bright electron beams.This work is composed of three complementary studies. First, the outgassing rates of three nominally identical 304L stainless steel vacuum chambers were studied to determine the effects of chamber coatings (silicon and titanium nitride) and heat treatments. For an uncoated stainless steel chamber, the diffusion limited outgassing was taken over by the recombination limited process as soon as a low outgassing rate of ~1.79(0.05)  10 -13 Torr L s -1 cm -2 was achieved. An amorphous silicon coating on the stainless steel chambers exhibited recombination limited behavior and any heat treatment became ineffective in reducing the outgassing rate. A TiN coated chamber yielded the smallest apparent outgassing rate of all the chambers: 6.44(0.05)  10 -13 Torr L s -1 cm -2 following an initial 90 °C bake and 2(20)  10 -16 Torr L s -1 cm -2 following the final bake in the series. This perceived low outgassing rate was attributed to the small pumping nature of TiN coating itself.Second, the high voltage performance of three TiN-coated aluminum electrodes, before and after gas conditioning with helium, were compared to that of bare aluminum electrodes and electrodes manufactured from titanium alloy (Ti-6Al-4V). This study suggests that aluminum electrodes, coated with TiN, could simplify the task of implementing photocathode cooling, which is required for future high current electron beam applications. The best performing TiNcoated aluminum electrode demonstrated less than 15 pA of field emission current at -175 kV for a 10 mm cathode/anode gap, which corresponds to a field strength of 22.5 MV/m. Third, the effect of antimony thickness on the performance of bialkali-antimonide photocathodes was studied. The high-capacity effusion source enabled us to successfully manufacture photocathodes having a maximum QE around 10% and extended low voltage 1/e lifetime (> 90 days) at 532 nm via the co-deposition method, with relatively thick layers of antimony (≥ 300 nm). We speculate that alkali co-deposition provides optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali.In summary, this research examined the effectiveness of thin films applied on photogun chamber components to achieve an extremely high vacuum, to eliminate high voltage induced field emission from electrodes, and to generate photocurrent with high quantum yield with an extended operational lifetime. Simult...

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Section: Bare Stainless Steelsupporting

confidence: 62%

Thin film studies toward improving the performance of accelerator electron sources

Mamun

2016

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“…The reduction in outgassing rate due to the 150 °C bake is larger than would be expected due to hydrogen depletion through diffusion during the low temperature bake. Similar behavior seen elsewhere 13,35,36 is postulated to be a result of an oxide-layer diffusion barrier that forms after venting, evacuation and baking. The outgassing rate following the 250 °C bake increased to 2.79(±0.05)×10 -13 Torr L s -1 cm -2 , higher than the rate following either the 400 °C or the 150 °C bake.…”

Section: A Bare Stainless Steelmentioning

confidence: 65%

Effect of heat treatments and coatings on the outgassing rate of stainless steel chambers

Mamun¹,

Elmustafa²,

Stutzman

et al. 2013

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The outgassing rates of three nominally identical 304L stainless steel vacuum chambers were measured to determine the effect of chamber coatings and heat treatments. One chamber was coated with titanium nitride (TiN) and one with amorphous silicon (a-Si) immediately following fabrication. The last chamber was first tested without any coating, and then coated with a-Si following a series of heat treatments. The outgassing rate of each chamber was measured at room temperatures between 15 and 30 °C following bakes at temperatures between 90 and 400 °C. Measurements for bare steel showed a significant reduction in the outgassing rate by nearly a factor of 20 after a 400 °C heat treatment-12 Torr L s -1 cm -2 prior to heat treatment, reduced to 1.7×10 -13 Torr L s -1 cm -2 following heat treatment). The chambers that were coated with a-Si showed minimal change in outgassing rates with heat treatment, though an outgassing rate reduced by heat treatments prior to a-Si coating was successfully preserved throughout a series of bakes.The TiN coated chamber exhibited remarkably low outgassing rates, up to four orders of magnitude lower than the uncoated stainless steel, but the uncertainty in these rates is 2 large due to the sensitivity limitations of the spinning rotor gauge accumulation measurement and the possibility of a small pump speed due to inhomogeneity in the TiN coating. The outgassing results are discussed in terms of diffusion-limited versus recombination-limited processes.3

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“…4, the PRFs at 598 K of the corrosion layer formed under Ar + 0.1% H2 gas flow condition were estimated to be 25 (data1) and 20 (data2), while those under Ar + 1.0% H2 condition were 45 (data1) and 50 (data2). The obtained PRFs were much higher than those of the thin Fe2O3/Cr2O3 oxidized layers formed on stainless steels by oxidation (PRF: 2-3) [40]. The high PRF values of the corrosion layers can be explained by not only the thickness but also the dense microstructure of the corrosion product compared to that formed by oxidation as observed in Fig.…”

Section: Discussionmentioning

confidence: 78%

Hydrogen permeation from F82H wall of ceramic breeder pebble bed: The effect of surface corrosion

Mukai

Kenjo

Iwamatsu

et al. 2022

International Journal of Hydrogen Energy

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Effect of surface oxide layers on deuterium permeation through stainless steels with reference to outgassing reduction in ultra- to extremely high vacuum

Cited by 20 publications

References 30 publications

Thin film studies toward improving the performance of accelerator electron sources

Thin film studies toward improving the performance of accelerator electron sources

Effect of heat treatments and coatings on the outgassing rate of stainless steel chambers

Hydrogen permeation from F82H wall of ceramic breeder pebble bed: The effect of surface corrosion

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