Paolo Manini

An x-ray photoemission spectroscopy investigation of thermal activation induced changes in surface composition and chemical bonds of two gettering alloys : Zr2Fe versus Zr57V36Fe7

We report comparative XPS (hν=1253.6 eV) core level (Zr 3d; C 1s; O 1s; Fe 2p; V 2p) results from two relevant gettering alloys: Zr2Fe and Zr57V36Fe7. The samples were studied as‐received (after in‐air fracturing of bulk ingots) and after different annealing treatments (up to 700 °C) performed in ultrahigh vacuum. With increasing temperature both alloys show a progressive dissolution of Zr oxides, an increase in the metallic character of the surface, the gradual loss of C based adsorbates, and a progressive increase in the surface Zr content and at the expense of the C concentration. At temperatures in the range 300–550 °C a fraction of the C atoms form metallic carbides. OH‐based groups are depleted from the surface at low temperatures (200 °C), resulting in a sizable decrease of the near surface O content, while a nearly constant O concentration is found at intermediate and high temperatures. Only minor changes are observed for the near surface concentrations of Fe in Zr2Fe and Fe and V in Zr57V36Fe7 as...

Combination of compact nonevaporable getter and small ion pumps for ultrahigh vacuum systemsa)

The rapid pumpdown of ultrahigh vacuum (UHV) systems, achieved with a very short and low temperature baking or even without baking, is appealing in a variety of research and industrial applications. The use of small volume, compact pumps delivering very high pumping speed is also attractive since it allows minimizing the overall size and weight of the vacuum system, simplifying its design. In the present article, the authors report the results of the pumping experiments carried out on a vacuum chamber pumped by a compact nonevaporable getter (NEG) pump (Capacitorr D 400-2® model, SAES Getters SpA, Italy) and by a small sputter ion pump (SIP). To measure the effective contribution of the NEG to the overall pumping, vacuum tests were carried out in a wide range of situations, with/without NEG pump, with/without baking, and changing the pumping speed of the SIP from 60 to 10 l/s (N2). Significantly lower pressures and faster pumping could be achieved using the NEG pump. Base pressures of low 10−11 mbar could...

Design and characterization of high capacity nonevaporable getter pumps embedded inside the interaction regions of DAΦNE

The DAΦNE Φ-factory is a twin-ring 510 MeV e+e- collider facility under commissioning at INFN-LNF in Frascati. With a stored beam current of 5.3 A, a mean pressure of 1.3×10−9 mbar is required in each ring. For the KLOE interaction region, where a mean pressure of the order of 1.3×10−10 mbar is required, an embedded nonevaporable getter (NEG) pump with a CapaciTorr®-type structure was chosen mainly because of the unavailability of room for the installation of lumped pumps and to take maximum advantage of the sorption capability of the NEG pump for CO in the UHV operating conditions of the machine. A NEG pumping system of the kind discussed in this article seemed to be particularly suitable for the KLOE experiment, where limited servicing and high reliability is required. In this article we report on the design and characterization of both the first pump prototype, fitted with St-172 NEG alloy and the final pump version, where St-185 NEG alloy was used.

Near-surface chemistry in Zr2Fe and ZrVFe studied by means of x-ray photoemission spectroscopy: A temperature-dependent study

The near-surface atomic composition and the character of chemical bond in two nonevaporable gettering alloys have been investigated via core level (Zr 3d, Fe 2p, V 2p, O 1s, C 1s) photoemission. The samples have been measured in UHV after in-air fracturing and various annealing steps (up to 850 °C). For T>400 °C a progressive and sizeable decrease of the near surface C content along with an increase in the Zr concentration is observed in both alloys. An annealing induced Zr enrichment at the surface is found, the metallic atomic concentrations being significantly far from the nominal bulk stoichiometry. The annealing induces a strong evolution in the chemical bonds, the metallic species being completely oxidized in in-air fractured samples while a metallic character progressively emerges at increasing temperatures. Surface metallization proceeds faster in Zr2Fe than in the V-containing getter.The near-surface atomic composition and the character of chemical bond in two nonevaporable gettering alloys have been investigated via core level (Zr 3d, Fe 2p, V 2p, O 1s, C 1s) photoemission. The samples have been measured in UHV after in-air fracturing and various annealing steps (up to 850 °C). For T>400 °C a progressive and sizeable decrease of the near surface C content along with an increase in the Zr concentration is observed in both alloys. An annealing induced Zr enrichment at the surface is found, the metallic atomic concentrations being significantly far from the nominal bulk stoichiometry. The annealing induces a strong evolution in the chemical bonds, the metallic species being completely oxidized in in-air fractured samples while a metallic character progressively emerges at increasing temperatures. Surface metallization proceeds faster in Zr2Fe than in the V-containing getter.

The Transmission Factor Method: in‐situ Characterization of Getter Coated Pipes

Particle accelerators and synchrotron light source need low residual pressure during operating conditions. In specific applications like narrow‐gap insertion devices, NEG coating has proved to be very effective. ASTM F798‐82 standard is the common characterization method for the sorption performance of getters. In the case of getter coated pipes, the measurement is conducted “offline” on a sample (coupon), suitably positioned inside the chamber to be coated and removed after the process. Although this approach is suitable to guarantee the control of the process, in‐situ characterization should be useful to evaluate residual pressure during the operating conditions. A different measurement technique (Transmission Factor Method) is here described. It is based on the measurement of pressures ratio at the inlet and the outlet of a coated pipe, under a flow of test gas. A calibration curve is calculated using a modellistic approach and permits to evaluate sticking probability of the coated surface from the pressure ratio. Preliminary experimental results about the characterization of this getter will be shown. Keywords: Getter sorption measurement.

Recent Developments in the Open Cell Foam-Filled Vacuum Insulated Panels for Appliances Applications

Polyurethane foam is the preferred insulator material in a wide range of appliances such as refrigerators and freezers. The recent phase out of CFC-11 has however decreased its insulation performance due to the need to adopt environmentally more benign blowing agents, such as HCFCs and hydrocarbons, all having higher gas thermal conductivity. This represents a serious drawback since specific regulations to reduce the energy consumption in refrigerators have been issued in recent years, and even more demanding reductions are under debate and expected to be applied worldwide by the turn of the century. In response to these requirements, Vacuum Insulated Panels (VIPs) technology has been studied and developed. Suitable components, filler, bag and a getter to maintain the necessary vacuum, have to be selected to ensure the high super-insulation properties which can be exhibited by VIPs. Among various core materials for VIPs, open cell foams present specific advantages in terms of performance, weight, processability and cost. In the present paper, the recent developments in the VIP technology are reviewed and discussed focusing the attention on the open cell polyurethane. The various gas sources deteriorating the vacuum during the panel life have been experimentally determined and evaluated by means of outgassing, permeation and gas analysis measurements on VIP components and finished devices. A suitable getter system able to cope with the gas load and to ensure vacuum performance and reliability is also described.

Non Evaporable Getter (NEG) Pumps: a Route to UHV‐XHV

Non Evaporable Getter (NEG) technology has been developed in the 1970’s and since then adopted by industry, R&D labs, research centres and in large physics projects like accelerators, synchrotrons and fusion reactors. NEG pumps are very compact and vibration‐free devices able to deliver very high pumping with minimal power requirement and electromagnetic interference. In the present paper, main features and performances of getter pumps are reviewed and discussed with a special focus to photocathode gun application, where UHV or XHV conditions are mandatory to ensure adequate gun life. NEG coating and future challenges for NEG technology are also discussed.

NEG (Non Evaporable Getter) pumps for organic compounds and water removal in EUVL tools

One of present EUVL challenges is to reduce as much as possible the organic compounds and water partial pressures during the lithographic process. These gases can in fact interact with sensitive surfaces and, in the presence of EUV radiation, decompose to generate carbon-based films and oxides, which are detrimental to the optics, reducing its performance, lifetime and significantly increasing the equipment total cost of ownership. With this respect, use of Non Evaporable Getter (NEG) pumps seems particularly attractive. Getter pumps are very clean, vibration-free, compact, able to deliver large pumping speed for all active gases, including water and hydrogen. In the present paper, we report for the first time the results of specific tests aimed at measuring the pumping speed for some selected organic compounds, namely toluene and decane (n-decane). The study shows that getter pumps can effectively sorb these large organic molecules with high speed and capacity. Speed and capacity increases when operating the getter cartridge at moderate temperature (e.g. 150-200°C), however remarkable sorption is achieved, even at room temperature, without any power applied. When coupled with turbo-molecular pumps NEG pumps have therefore the potential to improve the ultimate vacuum and mitigate the carbon/oxygen contamination in a UHV lithographic system.

Use of non evaporable getter pumps to ensure long term performances of high quantum efficiency photocathodes

High quantum efficiency photocathodes are routinely used as laser triggered emitters in the advanced high brightness electron sources based on radio frequency guns. The sensitivity of “semiconductor” type photocathodes to vacuum levels and gas composition requires special care during preparation and handling. This paper will discuss the results obtained using a novel pumping approach based on coupling a 20 l s−1 sputter ion getter pump with a CapaciTorr® D100 non evaporable getter (NEG) pump. A pressure of 8⋅10−8 Pa was achieved using only a sputter ion pump after a 6 day bake-out. With the addition of a NEG pump, a pressure of 2⋅10−9 Pa was achieved after a 2 day bake-out. These pressure values were maintained without power due to the ability of the NEG to pump gases by chemical reaction. Long term monitoring of cathodes quantum efficiencies was also carried out at different photon wavelengths for more than two years, showing no degradation of the photoemissive film properties.

Non Evaporable Getter (NEG) Coatings for Vacuum Systems in Synchrotron Radiation Facilities

Non evaporable Getter (NEG) films, sputter deposited onto the internal surfaces of vacuum chambers, have been proposed by CERN to substantially reduce the gas pressure in UHV‐XHV systems. The NEG film acts as a conductance‐free distributed pump inside a chamber. Being a barrier for gases it also reduces thermal out‐gassing, thus allowing the achievement of very demanding pressure conditions. These features are ideal for very narrow, conductance limited chambers, like Insertion Devices, which cannot be always efficiently pumped by ordinary means. Recent investigations have also shown that NEG coatings do present additional interesting features, like low secondary electron yield and low gas de‐sorption rates under ions, electrons and photons bombardment, compared to traditional technical surfaces. Experimental tests, carried out in several high energy machines and synchrotron radiations facilities have so far confirmed the benefits of NEG films in term of better vacuum, longer beam life time and stability, ...