Production of ultrahigh vacuum by helium glow discharge cleaning in an unbaked vacuum chamber

Akaishi, K.; Ezaki, Kazuhiro; Motojima, O.; Nakasuga, M.

doi:10.1016/s0042-207x(97)00041-9

Cited by 5 publications

(3 citation statements)

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“…To improve the surface wettability, we developed an in situ pretreatment using a GDC that was performed at a pressure of 2.8 × 10 −2 Torr for 1 h. This cleaning step dissociates water molecules, forming OH radicals and H atoms [28,29]. The OH radicals remain on the surface in a strongly bound state, and only the hydrogen molecules are desorbed to the gas phase and pumped out of the chamber.…”

Section: Nanoparticle-covered Substratesmentioning

confidence: 99%

Homogeneous large-scale crystalline nanoparticle-covered substrate with high SERS performance

et al. 2015

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This article details the surface-enhanced Raman scattering (SERS) performance of plasmonic substrates fabricated by a physical metal evaporation technique that uses no precursor or intermediate coating. We outline a cost-effective nanofabrication protocol that uses common laboratory equipment to produce homogeneously covered crystalline nanoparticle substrates. Our fabrication yields a homogeneous SERS response over the whole surface. The platform is tested with methylene blue diluted at various concentrations to estimate the sensitivity, homogeneity, and reproducibility of the process. The capacity of the substrates is also confirmed with spectroscopic investigations of human microsomal cytochrome b5.

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Section: Nanoparticle-covered Substratesmentioning

confidence: 99%

Homogeneous large-scale crystalline nanoparticle-covered substrate with high SERS performance

et al. 2015

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“…Helium is chosen as the working gas since He-GDC is commonly used in tokamak devices [20,21]. Three particles, such as an electron, e, a positive ion, He + , and an excited helium atom are included.…”

Section: Governing Equations and Boundary Conditionsmentioning

confidence: 99%

Validity of the similarity law for the glow discharges in non-plane-parallel gaps

Luo

Zou

et al. 2014

Plasma Sources Sci. Technol.

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The glow discharges in the gaps geometrically similar to that used in glow discharge cleaning of the International Thermonuclear Experimental Reactor (ITER) were numerically simulated based on a two-dimensional fluid model in which the linear dimensions of gap A are two times that of gap B and the pressure of gap A is half that of gap B. Under an applied voltage of 1000 V, the physical parameters at the corresponding point pz in these two gaps were compared. It was found that the electric potential U (pz), the reduced field E(pz)/p and the electron temperature T e (pz) are equal in values for these two gaps, but the electron density n e (pz) and ion density n i (pz) for gap B are four times that of gap A. All these parameter ratios are the same as that defined by similarity law, which confirmed that the similarity law is valid for the glow discharges in non-plane-parallel gaps.

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“…Akaishi 1997 [9] experimentally investigated the effect of helium glow discharge cleaning as a wall conditioning technique for the production of ultrahigh vacuum in an unbaked vacuum system. A test chamber made of 304 stainless steel was constructed.…”

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confidence: 99%

Removal of water from unbaked vacuum system

Pal

Yadav

Akhter

et al. 2012

J. Phys.: Conf. Ser.

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The water vapour contained in the atmosphere contaminates a vacuum systems, when it is exposed to air. The degree of contamination will depend on the surface characteristics, treatment of the system walls, the relative humidity and the turbulence of air, the amount of time the system is opened to the atmosphere, etc. If the temperature of the exposed surface is low, possibility of water condensing on the surface exists. In order to study the effect and optimise procedure for achieving high vacuum in a vacuum chamber initially containing water, a vacuum chamber has been fabricated. Pump down time has been measured for different amount of water placed in the vacuum chamber with varying pumping speeds. The paper presents a review of similar activities and results of the experimental study. Introduction:The beam chamber of VEC superconducting cyclotron [1] has a number of penetrations in the median plane in between the upper and lower superconducting coils to accommodate extraction components and beam diagnostic components. Because of the compact structure, adequate space was not available at the penetrations for placing a thermal shield. The temperature at these penetrations is quite low. It is observed that moisture from air condenses there and considerable time is taken to achieve good vacuum, specially, in monsoon. In the case of water leakage in the system, considerable amount of water gets accumulated in the beam chamber. Because of the complex geometry of the cyclotron, it is quite difficult to remove water from the restricted areas. It is also not possible to bake the acceleration chamber to enhance the rate of moisture removal.An experimental set-up has been fabricated to study the pump down characteristics in the presence of water in a vacuum enclosure. The paper presents a literature survey on work carried out on similar lines and results of experiments carried out. Review of similar activitiesChan 2010 [2] examined the effect of environment humidity on the rate of thermal outgassing from an aluminium chamber. An aluminium glove box and an air shower, which provided dehumidified environments with water vapor concentrations of 0.1 ppm and 5 ppm respectively, were utilized to assess the effect of environmental humidity on the rate of thermal outgassing. Chan observed that only 4 h of evacuation was required to yield a small rate of the order of 1 x 10 -13 mbar L s -1 cm 2 of thermal outgassing upon filling with super-dry nitrogen without baking. A smaller rate of thermal outgassing was obtained using a drier venting gas, or by exposure to a drier environment. A thermal outgassing rate of the order of 1 x 10 -11 mbar L s -1 cm 2 was achieved by venting the glove box with super-dry nitrogen inside and controlling of environmental humidity at 0.1 ppm.Yamazaki 2010 [3] carried out control of water vapor in a nitrogen gas purge line in addition to surface treatments of chambers using buff polishing and electrolytic polishing, followed by

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Production of ultrahigh vacuum by helium glow discharge cleaning in an unbaked vacuum chamber

Cited by 5 publications

References 0 publications

Homogeneous large-scale crystalline nanoparticle-covered substrate with high SERS performance

Homogeneous large-scale crystalline nanoparticle-covered substrate with high SERS performance

Validity of the similarity law for the glow discharges in non-plane-parallel gaps

Removal of water from unbaked vacuum system

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