Vacuum properties of TiZrV non-evaporable getter films

Benvenuti, C.; Chiggiato, Paolo; Pinto, P. Costa; Santana, Antonio; Hedley, T; Mongelluzzo, A.; Ruzinov, V.L.; Wevers, I.

doi:10.1016/s0042-207x(00)00246-3

Cited by 168 publications

(103 citation statements)

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“…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 .…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

Lowering the activation temperature of TiZrV non-evaporable getter films

Prodromides

Scheuerlein

Taborelli

2001

Vacuum

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“…In order to face these issues, the chamber consists of a cylindrical copper tube which is coated with non-evaporable getter (NEG) alloy. Even though the NEG coating technology, originally developed at CERN (Benvenuti et al, 2001), has already been applied on a large scale to insertion device chambers (Kersevan & Hahn, 2006) as well as to straight vessels in synchrotron radiation sources [about 56% of the SOLEIL chambers are NEG coated (Herbeaux et al, 1998)], the MAX IV 3 GeV storage ring will be the first light-source storage ring to be close to 100% NEG coated, including straight sections as well as dipole (bent) chambers. The coating of such narrow tubes, particularly the chambers which are used for extraction of the insertion device radiation, presents a significant engineering challenge.…”

Section: Vacuummentioning

confidence: 99%

The MAX IV storage ring project

et al. 2014

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The MAX IV facility, currently under construction in Lund, Sweden, features two electron storage rings operated at 3 GeV and 1.5 GeV and optimized for the hard X-ray and soft X-ray/VUV spectral ranges, respectively. A 3 GeV linear accelerator serves as a full-energy injector into both rings as well as a driver for a short-pulse facility, in which undulators produce X-ray pulses as short as 100 fs. The 3 GeV ring employs a multibend achromat (MBA) lattice to achieve, in a relatively short circumference of 528 m, a bare lattice emittance of 0.33 nm rad, which reduces to 0.2 nm rad as insertion devices are added. The engineering implementation of the MBA lattice raises several technological problems. The large number of strong magnets per achromat calls for a compact design featuring small-gap combined-function magnets grouped into cells and sharing a common iron yoke. The small apertures lead to a low-conductance vacuum chamber design that relies on the chamber itself as a distributed copper absorber for the heat deposited by synchrotron radiation, while non-evaporable getter (NEG) coating provides for reduced photodesorption yields and distributed pumping. Finally, a low main frequency (100 MHz) is chosen for the RF system yielding long bunches, which are further elongated by passively operated thirdharmonic Landau cavities, thus alleviating collective effects, both coherent (e.g. resistive wall instabilities) and incoherent (intrabeam scattering). In this paper, we focus on the MAX IV 3 GeV ring and present the lattice design as well as the engineering solutions to the challenges inherent to such a design. As the first realisation of a light source based on the MBA concept, the MAX IV 3 GeV ring offers an opportunity for validation of concepts that are likely to be essential ingredients of future diffraction-limited light sources.

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“…NEGs were used for the first time to provide the large and linear pumping required for accelerators in the Large Electron Positron collider at CERN [3]. To cope with the requirements of the subsequent CERN accelerator (the Large Hadron Collider), NEG thin film coatings were developed [4], a technology covered by CERN patents and widely used in other projects since. The getter used for the panel consists of a thin film deposited on both sides of an aluminium foil by means of a dedicated sputtering system, which may produce about 150 m 2 of coated foil per week.…”

Section: Vacuum Considerationsmentioning

confidence: 99%

The SRB solar thermal panel

Benvenuti¹

2013

Europhysics News

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tHe srB solar tHerMal paNel Features 16T he mechanical design of the panel [1] is shown schematically in Fig. 1. It consists of a metal frame sealed on both sides by glass windows, allowing solar radiation to enter at either side. The resulting box contains blackened copper heat absorbers which capture the solar energy. The absorbers are laser welded to stainless steel pipes which allow the heat to be extracted by circulating a fluid. These features are common to any flat solar thermal panel. The distinctive feature of the SRB panel is that it is under vacuum. Evacuated flat-plate panels were not produced so far because a vacuum-tight connection between large glass windows and the metal structure of the panel presents an (almost) insurmountable difficulty. The SRB solution to this problem consists of a plasma-sprayed metal coating on the glass perimeter, on which a metal joint may then be fixed by soft soldering. When the panel is under vacuum, the atmospheric pressure applies a force of 10 N/cm -2 on the panel windows, resulting in a weight of many tons for a medium-size panel. This force would lead to implosion of the panel if not properly supported. The spacing between the supports depends on the glass type and thickness. The SRB panel makes use of tempered glass 5 mm thick and longitudinal supports spaced by 14 cm, resulting in an implosion pressure of 2.5 bar.The absorbers are coated with a selective coating, to efficiently absorb the incident sunlight while providing low emission in the infrared range (see optical characteristics). High vacuum is maintained throughout the panel life of 30 years by a getter pump driven by solar energy (see vacuum considerations). Optical characteristicsBoth the pump and the absorbers are blackened electrolytically with a layer of Cr oxide which provides an absorption coefficient of about 0.9 and an infrared emissivity at 300°C below 0.07. This coating is stable when Vacuum considerationsVacuum is the best thermal insulator provided by nature. In a traditional thermal solar panel, conduction and convection through the ambient air results in large thermal losses, which limits the panel temperature and the range of applications. By evacuating the panel, thermal losses are reduced dramatically, thus increasing the panel efficiency.When an SRB panel is exposed to sun light while being in vacuum, its temperature is limited only by emission losses through infrared radiation. If the pressure is progressively increased, the temperature does not change until about 10 -4 mbar, and then it drops quickly due to molecular conduction and becomes constant after reaching 10 -1 mbar. Therefore, the pressure inside the solar panel must be kept below about 10 -4 mbar during the lifetime of the panel to keep the molecular conduction losses negligible with respect to the radiation losses. In any sealed device, after initial evacuation of the atmospheric air, vacuum must be maintained by pumping the gases desorbing from the device components. Since about a century this is done by getters, which...

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Vacuum properties of TiZrV non-evaporable getter films

Cited by 168 publications

References 9 publications

Lowering the activation temperature of TiZrV non-evaporable getter films

Lowering the activation temperature of TiZrV non-evaporable getter films

The MAX IV storage ring project

The SRB solar thermal panel

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