Nonevaporable getter films for ultrahigh vacuum applications

Benvenuti, C.; Chiggiato, Paolo; Cicoira, Fabio; L’Aminot, Y.

doi:10.1116/1.580963

Cited by 91 publications

(39 citation statements)

References 11 publications

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“…The initially adopted sputtering system makes use of a composite cathode obtained by twisting together wires of different materials 1 . However, this configuration limits the range of achievable elemental compositions.…”

Section: Coating Deposition Methodsmentioning

confidence: 99%

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Lowering the activation temperature of TiZrV non-evaporable getter films

Prodromides

Scheuerlein

Taborelli

2001

Vacuum

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In order to reduce the activation temperature of the TiZrV alloy, thin films of various compositions were produced by three-cathode magnetron sputtering on stainless steel substrates. For the characterisation of the activation behaviour the surface chemical composition has been monitored by Auger Electron Spectroscopy (AES) during specific in situ thermal cycles. The volume elemental composition of the film has been measured by Energy Dispersive X-ray spectroscopy (EDX) and the morphology (crystal structure and size of the crystallites) has been investigated by X-ray diffraction (XRD). The criteria indicating the sample quality and its dependence on film structure and chemical composition are presented and discussed.Keywords: getter, activation, NEG, titanium alloy, vanadium alloy, zirconium alloy, ternary alloys, thin film Paper presented at the 6th European Vacuum Conference University Lyon 1, Campus La Doua/IPNL, Lyon, France 7-10 December 1999 To be published in "Vacuum" Geneva, SwitzerlandDécembre 1999 -2 - INTRODUCTIONIn the context of the technical developments for the construction of the Large Hadron Collider (LHC) at CERN, a systematic study has been undertaken in order to produce suitable non-evaporable getter films (NEG). Many coatings composed of various elements have been produced and tested, which all exhibited activation temperature below 400 °C 1,2 . The lowest activation temperature, 200 qC for a 24-hour heating, has been obtained with a TiZrV alloy thin film 3 . A complete review of the results obtained with this coating is presented separately at this conference 4 .In the present study, thin films of titanium-zirconium-vanadium ternaries with various compositions have been produced and characterised by structural and chemical analyses in order to possibly further decrease the activation temperature. Characterisation by surface analytical techniques has been chosen, namely Auger Electron Spectroscopy (AES). It was preferred to other techniques because it results in faster sample production and characterisation. EXPERIMENTAL Coating deposition methodNEG thin films are produced by sputtering, because this deposition method provides an easy way to deposit an uniform coating on complex and narrow access chambers, and it can be applied to most metals and their alloys. The initially adopted sputtering system makes use of a composite cathode obtained by twisting together wires of different materials 1 . However, this configuration limits the range of achievable elemental compositions. In order to have a wider choice of compositions a three magnetron sputtering system has been adopted, in which the three cathodes are independently supplied. All our samples have been produced using the same parameters: a total base pressure after bake-out in the 10 -7 Pa range, an argon discharge pressure of 7 x 10 -1 Pa, non heated substrates (T d 90 qC), water cooled cathodes, constant magnetic fields due to two SmCo magnets (a central Sm 2 Co 17 circular magnet surrounded by a SmCo 5 toroidal magnet).The powe...

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Section: Coating Deposition Methodsmentioning

confidence: 99%

“…Many coatings composed of various elements have been produced and tested, which all exhibited activation temperature below 400 °C 1,2 . The lowest activation temperature, 200 qC for a 24-hour heating, has been obtained with a TiZrV alloy thin film 3 .…”

Section: Introductionmentioning

confidence: 99%

Lowering the activation temperature of TiZrV non-evaporable getter films

Prodromides

Scheuerlein

Taborelli

2001

Vacuum

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“…The WL irradiation ͑10 16 10 17 photons͞mm 2 ͒ partially cleans the dirty surface of the as-received sample, but does not clean it completely since the resulting spectrum is somewhat different from that exhibited by the essentially clean Cu surface, obtained by argon sputtering of the Cu sample. Ar ion sputtering (estimated dose 8 3 10…”

Section: Photoemission With Monochromatic Light: Cumentioning

confidence: 99%

“…III B, suggest strongly that the WL spectra of the as-received and conditioned samples, presented in the previous sections, were subject to modifications due to the significant irradiation dose of WL during their acquisition (10 16 …”

Section: G Generation Of Low Dose Wl Spectramentioning

confidence: 99%

“…A family of candidate materials for the LHC vacuum chambers are nonevaporable getters (NEGs) since they provide an elegant solution for distributed pumping in conductance limited vacuum systems [16]. In particular these materials are being proposed in the warm sections of the machine and in the experimental beam pipes.…”

Section: Photemission With Monochromatic Light: Tizrmentioning

confidence: 99%

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VUV photoemission studies of candidate Large Hadron Collider vacuum chamber materials

Cimino

Collins

Baglin

1999

Phys. Rev. ST Accel. Beams

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In the context of future accelerators and, in particular, the beam vacuum of the Large Hadron Collider (LHC), a 27 km circumference proton collider to be built at CERN, VUV synchrotron radiation (SR) has been used to study both qualitatively and quantitatively candidate vacuum chamber materials. Emphasis is given to show that angle and energy resolved photoemission is an extremely powerful tool to address important issues relevant to the LHC, such as the emission of electrons that contributes to the creation of an electron cloud which may cause serious beam instabilities and unmanageable heat loads on the cryogenic system. Here we present not only the measured photoelectron yields from the proposed materials, prepared on an industrial scale, but also the energy and in some cases the angular dependence of the emitted electrons when excited with either a white light (WL) spectrum, simulating that in the arcs of the LHC, or monochromatic light in the photon energy range of interest. The effects on the materials examined of WL irradiation and /or ion sputtering, simulating the SR and ion bombardment expected in the LHC, were investigated. The studied samples exhibited significant modifications, in terms of electron emission, when exposed to the WL spectrum from the BESSY Toroidal Grating Monochromator beam line. Moreover, annealing and ion bombardment also induce substantial changes to the surface thereby indicating that such surfaces would not have a constant electron emission during machine operation. Such characteristics may be an important issue to define the surface properties of the LHC vacuum chamber material and are presented in detail for the various samples analyzed. It should be noted that all the measurements presented here were recorded at room temperature, whereas the majority of the LHC vacuum system will be maintained at temperatures below 20 K. The results cannot therefore be directly applied to these sections of the machine until measurements at cryogenic temperatures, i.e., in the presence of cryosorbed gas layers, are obtained. However, these results are directly relevant to all the warm regions of the LHC vacuum system, such as the experimental vacuum chambers and warm element vacuum chambers in the insertion regions. [S1098-4402(99)

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XPS analysis of the activation process in non-evaporable getter thin films

Lozano

Fraxedas

2000

Surf. Interface Anal.

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Nonevaporable getter films for ultrahigh vacuum applications

Cited by 91 publications

References 11 publications

Lowering the activation temperature of TiZrV non-evaporable getter films

Lowering the activation temperature of TiZrV non-evaporable getter films

VUV photoemission studies of candidate Large Hadron Collider vacuum chamber materials

XPS analysis of the activation process in non-evaporable getter thin films

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