Effect of coating morphology on the electron stimulated desorption from Ti–Zr–Hf–V nonevaporable-getter-coated stainless steel

Malyshev, O.B.; Valizadeh, Reza; Jones, R.M.A.; Hannah, Adrian

doi:10.1016/j.vacuum.2012.04.033

Cited by 25 publications

(24 citation statements)

References 8 publications

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“…Table I in the present work and Table 1 in Ref. 18). The latter result can be explained by the variations in pumping properties present between samples.…”

Section: Discussionsupporting

confidence: 65%

“…17 However, the lowest electron-stimulated gas desorption (ESD) yields were achieved with a quaternary Ti-Zr-Hf-V film with a dense structure deposited from an alloy target. 18,19 This is due to the nature of the dense film as a superior barrier for hydrogen diffusion from the vacuum chamber material into the vacuum. By combining the low ESD yield of the dense film and the highest pumping properties of the columnar film, one may be able to achieve an even lower gas density.…”

Section: Introductionmentioning

confidence: 99%

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Pumping and electron-stimulated desorption properties of a dual-layer nonevaporable getter

Malyshev¹,

Valizadeh²,

Hannah³

2016

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

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Citation: OB Malyshev, R Valizadeh and AN Hannah. "Pumping and electronstimulated desorption properties of a dual-layer nonevaporable getter".The ASTeC Vacuum Science Group has an ongoing study for the improvement of the nonevaporable getter (NEG) coatings currently used in many accelerators around the world. The main advantages of using NEG coatings are evenly distributed pumping speed, low thermal outgassing rates, and low photon-stimulated gas desorption and electron-stimulated gas desorption (ESD). Previously, it was shown that the dense NEG coating provides lower ESD compared to that of a columnar film, but its pumping properties are reduced. This paper describes the results for a dual layer of NEG where a dense layer was deposited first and a columnar layer was then deposited on top. In such a dual-layer NEG coating, the dense layer acted as a barrier for hydrogen diffusion and the columnar layer further reduced the ESD of hydrogen and provided improved pumping properties. An alloy target of Ti-Zr-Hf-V was used to deposit a 0.5 lm-thick layer of the dense NEG followed by a 1 lm-thick columnar structure of NEG onto the inner surface of a 50-cm long stainless steel tube. The composition and the structure of the dual layer were determined by energy dispersive x-ray spectroscopy and scanning electron microscopy, respectively. The NEG vacuum performance was tested using the ESD and pumping properties, which were measured on a dedicated in-house designed facility.

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“…Table I in the present work and Table 1 in Ref. 18). The latter result can be explained by the variations in pumping properties present between samples.…”

Section: Discussionsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Pumping and electron-stimulated desorption properties of a dual-layer nonevaporable getter

Malyshev¹,

Valizadeh²,

Hannah³

2016

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

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“…18 The values for the ESD yields are significantly (2-20 times) lower than the data from our previous study, which, at the time, demonstrated the lowest ESD yields obtained prior to the experiments reported in this paper. 18 The values for the ESD yields are significantly (2-20 times) lower than the data from our previous study, which, at the time, demonstrated the lowest ESD yields obtained prior to the experiments reported in this paper.…”

Section: Resultscontrasting

confidence: 72%

“…In other words, unlike the thermal outgassing, the ESD and PSD are more sensitive to the hydrogen concentration in the bulk than to the surface condition, which is responsible for H 2 recombination. 18 It was demonstrated that H 2 ESD yield as a function of electron dose initially reduced with dose, but after reaching a certain dose (which varied between 3 Â 10 21 and 7 Â 10 23 e À /m 2 depending on the sample and the conditions of the experiment), it no longer reduced and eventually increased. To reduce these yields even further, one has to determine where the hydrogen is coming from.…”

Section: Introductionmentioning

confidence: 99%

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Electron-stimulated desorption from polished and vacuum fired 316LN stainless steel coated with Ti-Zr-Hf-V

Malyshev

Valizadeh

Hogan

et al. 2014

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

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Articles you may be interested inEffect of surface polishing and vacuum firing on electron stimulated desorption from 316LN stainless steel Electron stimulated desorption from bare and nonevaporable getter coated stainless steelsIn this study, two identical 316LN stainless steel tubular samples, which had previously been polished and vacuum-fired and then used for the electron-stimulated desorption (ESD) experiments, were coated with Ti-Zr-Hf-V with different morphologies: columnar and dense. ESD measurement results after nonevaporable getter (NEG) activation to 150, 180, 250, and 350 C indicated that the values for the ESD yields are significantly (2-20 times) lower than the data from our previous study with similar coatings on nonvacuum-fired samples. Based on these results, the lowest pressure and best long-term performance in particle accelerators will be achieved with a vacuum-fired vacuum chamber coated with dense Ti-Zr-Hf-V coating activated at 180 C. This is likely due to the following facts: after NEG activation, the hydrogen concentration inside the NEG was lower than in the bulk stainless steel substrate; the NEG coating created a barrier for gas diffusion from the sample bulk to vacuum; the dense NEG coating performed better as a barrier than the columnar NEG coating.

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Non‐evaporable Getter ( NEG )‐Coated Vacuum Chamber

Malyshev

2019

Vacuum in Particle Accelerators

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Effect of coating morphology on the electron stimulated desorption from Ti–Zr–Hf–V nonevaporable-getter-coated stainless steel

Cited by 25 publications

References 8 publications

Pumping and electron-stimulated desorption properties of a dual-layer nonevaporable getter

Pumping and electron-stimulated desorption properties of a dual-layer nonevaporable getter

Electron-stimulated desorption from polished and vacuum fired 316LN stainless steel coated with Ti-Zr-Hf-V

Non‐evaporable Getter ( NEG )‐Coated Vacuum Chamber

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