SAES Getters Research Articles

Experimental Characterization of an NEG Pump of Novel Size—A Major Step toward Its Application in DEMO Neutral Beam Injectors

A future nuclear fusion plant DEMO needs neutral beam injection (NBI) systems requiring a vacuum pumping system with a very high pumping speed, in the order of several 1000 m3/s. Large customized cryopumps are actually used to meet the requirements. A promising concept for future NBI systems is based on high capacity getter materials. The ZAO® alloy, developed by SAES Getters, Italy, provides a drastically improved performance for the pumping of hydrogen compared to conventional getter materials. This paper describes the experimental characterization of a large pump of scalable size with 15 kg of ZAO® and the achieved results, in particular the systematic investigation of sorption characteristics and regeneration behaviors. Major findings include a very good repeatability of the sorption performance, a reduced pumping speed at higher pressures only above the NBI relevant level, an improved performance (+20%) with elevated getter temperature and an isotope independent sticking coefficient for hydrogen. Furthermore, improved operation experience and regeneration prediction tools have been developed. Employing the experimental results, a simulation task was performed and the sticking factor of the getter cartridge was determined with 7%.

A Study of the Gettering Characteristics of Getter Pumps for Different Gases

The gettering characteristics of Ti–Zr–Al getter pumps with internal and external heaters have been measured for Н2 and CO. The results are compared to the measured similar characteristics of an NEX‑Torr D 100-05 combined pump from SAES Getters and a titanium sublimation film at temperatures of 300 and 77 K.

New active packaging for improving the shelf life and quality of tomato

Packaging materials play an important role in the quality preservation during postharvest storage and shelf life of fruits and vegetables. The properties of film can affect the gas composition and indirectly the physiology of the products. Nowadays, several additives can be used for improving the film permeability or reducing certain gases such as ethylene. The Group Research Labs of SAES Getters S.p.A. have developed, in collaboration with its affiliate company SAES Coated Films S.p.A. a highly selective packaging system for ethylene, including an integrated absorber in the form of a coating (1-2 µm), with good transparency and an additional anti-fog function, which can be deposited on various plastic films. The objective of the work was the evaluation of this new active packaging on 'cherry' type tomato berries (Solanum lycopersicum L.) during storage. The control consisted of a macro-perforated polypropylene film used for flow-pack packaging. Two experimental tests were conducted, the first during cold storage (10 ± 2 ° C) and the second at room temperature (22 ± 2 ° C). The analyses carried out included visual appearance, weight loss, gas exchanges, relative humidity, volatile organic compounds (VOC), colour, titratable acidity, refractometric index (° Brix) and the concentration of lycopene and β-carotene. The use of the innovative packaging did not alter the main quality indicators of the tomato (° Brix, acidity, colour). In general, the parameter that had the greatest impact on the product metabolism was the storage temperature. The VOC concentration was influenced by packaging film, with a greater accumulation in the samples packed with active packaging compared to the control. Moreover, the same material determined a reduction in weight loss, a greater accumulation of CO2 and a significant reduction in O2, especially at 22 °C. At the end of the storage, the berries stored in the active packaging showed higher levels of lycopene, compared to controls, and a reduction in β-carotene, indicating an active role of the packaging in modulating the content of bioactive compounds in the fruits. It can be concluded that the use of this innovative material can represent an effective tool for improving the postharvest management of tomato berries.

Balancing actions for radical and incremental innovations in SAES Getters

In a context of limited resources, in terms of time, competencies and money, companies face the problem of being ambidextrous, i.e. to manage and achieve both radical and incremental innovation, by adopting both technology push and market pull approaches. The paper tries to enrich the empirical evidence on the topic, with the practical experience of a company, SAES Getters, which defined a set of actions that could help in finding and maintaining a sustainable balance between incremental and radical innovation. Organisational and cultural actions are implemented by SAES to manage ambidexterity: the definition of an organisation structure able to capture simultaneously technology push and market pull forces, a leadership and a decision making structure able to enable the coordination of such forces, the development of a new language for innovation.

Balancing actions for radical and incremental innovations in SAES Getters

Balancing actions for radical and incremental innovations in SAES Getters

Effects of getters on hermetically sealed micromachined cesium–neon cells for atomic clocks

The wafer-level integration technique of PageWafer® (SAES Getters’ solution for getter film integration into wafer to wafer bonded devices) has been tested in hermetically sealed miniature glass-Si-glass cells filled with Cs and Ne, e.g. for microelectromechanical systems (MEMS) atomic clock applications. Getter effects on the cell atmosphere are analyzed by quadruple mass spectroscopy and coherent population trapping (CPT) spectroscopy. The quadruple mass spectroscopy revealed that the residual gases (H2, O2, N2 and CO2) that are attributed to anodic bonding process are drastically reduced by the getter films while desirable gases such as Ne seem to remain unaffected. The impurity pressure in the getter-integrated cells was measured to be less than 4 × 10−2 mbar, i.e. pressure 50 times lower than the one measured in the cells without getter (2 mbar). Consequently, the atmosphere of the getter-integrated cells is much more pure than that of the getter-free cells. CPT signals obtained from the getter-integrated cells are stable and are, in addition, similar to each other within a cell batch, suggesting the strong potential of applications of this getter film and especially for its wafer-level integration to MEMS atomic clocks and magnetometers.

Development of First European Chip-scale Atomic Clocks:Technologies, Assembling and Metrology

This contribution concerns the results of the European Collaborative Project MAC-TFC (MEMS Atomic Clocks for Timing, Frequency Control & Communications) aiming the developments of the European version of MEMS atomic clock presenting a short-term stability of 5x10-11 over 1 hour. MAC-TFC proposal (website: www.mac-tfc.eu) is bringing together a consortium made of five major academic institutions (University of Besancon, University of Neuchâtel, EPFL-Lausanne, Technological University of Wroclaw, University of Ulm); two research institutes (VTT and CEA/Leti) and three industrial partners (SAES Getters, SWATCH R&D and Oscilloquartz). The goal is to develop and demonstrate all the necessary technologies to achieve an ultra-miniaturised, low-power caesium (Cs) atomic clock, using the principle of Coherent Population Trapping (CPT).

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

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 be obtained in the authors’ experimental system with the compact NEG assisted by the 10 l/s SIPs after a 48 h bake-out. The results also show that the system with NEG reached 10−11 mbar after a very short (few hours) bake-out. The base pressure was 1×10−10 mbar with 60 l/s SIP alone after a 48 h bake-out, whereas it was 7.9×10−11 mbar when combined with the NEG, a better result after only 2 h bake-out. This is quite a remarkable decrease in the bake-out time of a UHV system. It is worthwhile to note that UHV could also be achieved with the NEG even in a fully unbaked system. The pressure of 8×10−9 mbar reached with the SIP alone dropped to 3.9×10−10 mbar after adding the NEG. The other interesting result of the NEG-based system is that the pressure increase is much slower when the SIP is switched off. This is also a good characteristic, required for portable vacuum devices, such as UHV suitcases and more generally for systems hosting sensitive materials or components, which can be affected by the pressure increase following a power interruption.

SmartFlex® NiTi Wires for Shape Memory Actuators

Shape memory alloys (SMAs) are active metallic materials classified nowadays as “smart” or “intelligent” materials. One of their main areas of interest is that of actuators. The use of SMAs in actuators offers the opportunity to develop robust, simple, and lightweight elements that can represent an alternative to electro-magnetic actuators commonly used in several fields of industrial applications, such as automotive, appliances, etc. SAES Getters S.p.A. thanks to its vertically integrated process and to the scientific and quality approach, developed a NiTi-based wires family which can represent a solution for shape memory actuators. In this paper, the mechanical, thermal, and electrical response of these shape memory wires, with diameters ranging from 20 to 500 μm, will be examined and discussed, with particular focus on the design of the actuator. The thermo-mechanical properties have been investigated and measured by several methods. The most common and useful tests for these commercially available wires will be also described.

Embedding of Superelastic SMA Wires into Composite Structures: Evaluation of Impact Properties

Shape memory alloy (SMA) represents the most versatile way to realize smart materials with sensing, controlling, and actuating functions. Due to their unique mechanical and thermodynamic properties and to the possibility to obtain SMA wires with very small diameters, they are used as smart components embedded into the conventional resins or composites, obtaining active abilities, tunable properties, self-healing properties, and damping capacity. Moreover, superelastic SMAs are used to increase the impact resistance properties of composite materials. In this study, the influence of the integration of thin superelastic wires to suppress propagating damage of composite structures has been investigated. Superelastic SMAs have very high strain to failure and recoverable elastic strain, due to a stress-induced martensitic phase transition creating a plateau region in the stress-strain curve. NiTi superelastic wires (A f = −15 °C fully annealed) of 0.10 mm in diameter have been produced and characterized by SAES Getters. The straight annealed wire shows the typical flag stress-strain behavior. The measured loading plateau is about 450 MPa at ambient temperature with a recoverable elastic strain of more than 6%. For these reasons superelastic SMA fibers can absorb much more strain energy than other fibers before their failure, partly with a constant stress level. In this paper, the improvement of composite laminates impact properties by embedding SMA wires is evaluated and indications for design and manufacturing of SMA composites with high-impact properties are also given.

Determination of the sticking probability of a Zr–V–Fe nonevaporable getter strip

The Karlsruhe Tritium Neutrino experiment is an ambitious experiment to determine the electron neutrino mass with a sensitivity of 0.2eV. To achieve this extremely high precision, stringent UHV pressures below 10−11mbar in two large spectrometer vessels are requested. This will be achieved by several kilometers of nonevaporable Zr–V–Fe alloy getter (NEG) strips (type St707, manufactured by SAES Getters) which are to be integrated into robust cylindrical cartridges. The knowledge of the sticking probability is essential because the interference between the strips has to be taken into account in order to optimize the interior NEG pump geometry. In this article, the authors will use the Monte Carlo simulation approach to derive the sticking probability of the St707 NEG strip from the experimental data. The derived sticking probability is 0.0290(4), which is about 25% higher than the value estimated by the one-dimensional approximation, used by the standard procedure of the analytical method. Based on this value, different geometrical configurations of the pump setup are discussed. It is shown that the pumping speed of the resulting NEG pump with 1km St707 NEG strips is about 337m3∕s for H2 at 15°C.

New getter pump for ultrahigh vacuum systems and transportable enclosure

We have developed a new type of nonevaporable getter (NEG) pump. It is based on the getter strip St707, produced by SAES getters S.p.A, fitted into a CF-flanged container. The pump is activated at 400°C for 1 h and its pumping behavior is studied for H2, CO, and N2. The pumping speed is about 500 liters/s for H2, 230 liters/ for CO, and 130 liters/s for N2, which is in good agreement with our theoretical pumping model. While its performance is similar to those of commercial NEG pumps, it is definitely more compact, inexpensive, and easy to use. When coupled with single-penning cell, our NEG pump can replace conventional ion pumps in the design of compact ultrahigh vacuum (UHV) systems. Its first application will be as an efficient and compact pumping device for portable UHV enclosure.

SAES Getters and Aeronex Settle

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Electron stimulated molecular desorption of a non-evaporable Zr–V–Fe alloy getter at room temperature

Electron stimulated molecular desorption (ESD) from a non-evaporable getters (NEG) St 707 ® (SAES Getters ™) sample after conditioning and after saturation with isotopic carbon monoxide (cf. nomenclature in Handbook of Chemistry and Physics, CRC Press, 1994), 13C 18O, has been studied on a laboratory setup. Measurements were performed using an electron beam of 300 eV kinetic energy, with an average electron intensity of 1.6×10 15 electrons s −1. The electrons were impinging on the 15 cm 2 target surface at perpendicular incidence. It is found that the desorption yields η (molecules/electron) of the characteristic gases in an UHV system (hydrogen, methane, water, carbon monoxide, carbon dioxide) for a fully activated NEG as well as for a NEG fully saturated with 13C 18O are lower than for OFHC copper baked at 120 °C. A small fraction only of the gas which is required to saturate the getter surface can be re-desorbed and thus appears to be accessible to ESD.

Potassium adsorption on hydrogen- and oxygen-terminated diamond(100) surfaces

Abstract The adsorption of K at 298 K is a route for the titration of surface groups like O and OH. The experiments were performed on a semi-conducting natural diamond (100) surface cleaned by a 480-W microwave hydrogen plasma at 750°C and a hydrogen pressure of 20 mbar, resulting in a very clean, ordered (2×1) surface. A second type of C(100) surface was prepared by ex situ oxidation, using a mixture of hydrochloric and nitric acids. The adsorption experiments were carried out in a UHV system equipped with facilities for photoelectron spectroscopy (XPS and UPS). K deposition was achieved using a dispenser source from the SAES Getters Company. The K uptake of H-terminated C(100) at room temperature is marginal, with a sticking coefficient of

Phenomenological Model of Non-Evaporated Getter for Micro-electromechanical Systems (MEMS) Applications

ABSTRACTThere has been increasing interest in the development and use of micro-electromechanical systems (MEMS) for various applications. Some MEM devices such as gyroscopes, accelerometers and bolometers, must be sealed under vacuum, at pressures below 10 millitorr, for efficient operation. A gas absorbing material (getter) is placed in the packages of these devices, to help maintain vacuum levels over service lives of many years. Heating under vacuum, just prior to sealing the package, activates getter, of this type. This study was undertaken to develop a model that could be used to estimate the quantity of getter needed as well as optimize the activation process subject to process constraints on time and temperature.The material studied was a titanium and zirconium-based alloy (7:3 by weight) non-evaporable getter in the form of strips produced by SAES Getters. The zirconium alloy consisted of zirconium (70.0%), vanadium (24.6%) and iron (5.4%) by weight. The getter was analyzed under different ambient conditions of temperature, time and atmospheric pressure. Auger electron spectroscopy (AES) depth profiling was used to analyze the diffusion depth of the contaminant gases absorbed by the getter material under each condition. The data acquired from the depth profiles were fit to a simple diffusion model. This model is currently being validated, by activating the getter material under various ambient conditions, and measuring pressures and gas compositions inside packages using a residual gas analyzer (RGA). The utility of this model for optimization of getter activation and estimating package vacuum levels over time will be discussed.

Microstructure and bulk reactivity of the nonevaporable getter Zr57V36Fe7

We report on a structural investigation of the zirconium-based ternary alloy getter “St 707” (from SAES Getters, Milan, Italy) based on in situ x-ray diffraction (XRD) measurements at high temperature in inert gas atmosphere accompanied by scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX) and thermal analysis by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) investigations. The XRD together with SEM-EDX confirms that the getter is biphasic before as well as after activation. Hexagonal Zr and the cubic Laves phase Zr(V1−xFex)2 with a narrow compositional range (0.16⩽×⩽0.18) coexist in this material. Upon heating, the in situ XRD shows a gradual decrease in the crystallinity of the Laves phase, which is attributed to its disintegration into small particles. DSC measurements under moist Ar exhibit an exothermic irreversible transition at ≈ 675 K which is associated with chemical bulk reactions and indicative of the gettering process. The operation of the gettering process during activation was verified by TGA measurements. It is concluded that the gettering process is correlated with the disintegration of the Laves phase. The sorption kinetics of water vapor were studied at 355 K over a pressure range of 101–102 Pa using a barometric technique. A change in the rate determining step is detected from an initial diffusion-controlled step to surface adsorption after some sorption cycles.

Design and pumping characteristics of a compact titanium–vanadium non-evaporable getter pump

A compact non-evaporable getter (NEG) pump is made by stacking sintered titanium–vanadium blades recently available from SAES Getters as St185. The 50 blades are stacked between copper spacers on a stainless steel tube, and are activated by a removable heater cartridge inserted into the tube. The room temperature pumping speeds for CO and N2 are measured as a function of sorbed gas quantities at various activation temperatures and with different NEG disk spacing, in order to optimize the pump design and operation. The study shows that there is a threshold of activation at a temperature of about 340 °C and optimal pumping speed and pumping capacity can be achieved with activation temperature around 550 °C. Linear pumping speeds of about 2200 l/s m and 1300 l/s m can be achieved for CO and N2, respectively, with activation at temperatures of 500 °C for 1 h. A direct comparison shows a much higher pumping speed for the St185 than that for the St707 (Zr–V–Fe alloy, also by SAES Getters). The low activation temperature of the St185 NEG and the compact design make the NEG pump cartridge particularly attractive for situations with tight space and with components sensitive to high temperature.

Zirconium Based Alloy Reactor Beds for Tritiated Water Handling

This paper addresses an important consideration in the application of a Zirconium based alloy reactor bed for tritiated water handling, namely the nature and extent of variation of the water vapour conversion rate of alloy during its use. Experimental results obtained from four different investigations are presented to summarily view the water vapour reduction behaviour and hydrogen isotope release by the alloy during the conversion. The ternary getter alloy -[Zr(V0.5Fe0.5)2], commercially known as St 737 (SAES Getters), is found to have good sorption properties for water vapour even at moderate temperatures (400 °C and less), and attractive sorption – desorption characteristics for hydrogen over a large and convenient working pressure range (up to ≈ 4 kPa). The four different conversion experiments performed, namely, (i) by “Fill” method, where the interaction occurred between a defined water vapour quantity and the getter alloy in the absence of any flow; (ii) under continuous water vapour “Flow” conditions; (iii) by subjecting the alloy to high concentrations of oxygen up-take (“Poisoning”) under water vapour flow conditions, with periodic regeneration; and (iv) over nearly the “Full Usage” of alloy where both the conversion and interposed relaxation durations extended up to a few thousand hours, showed that the functional characteristics of the Zr-V-Fe alloy are relevant to “batch” as well as “continuous” handling modes of a reactor operation.

Tritium Process Applications Using SAES Getters for Purification and Collection from Inert Gas Streams

A zirconium alloy getter-based tritium monitoring and collection system has been designed, built, and subsequently operated for three years at the Idaho National Engineering Laboratory. The system is automated to provide separation of tritium from {sup 41}Ar, collection of tritium on an hourly basis, unloading of getters for on-line tritium measurement via an ion chamber, and recollection of tritium on removable getters for daily assay in the laboratory. Three different SAES Getters alloys are employed to purify the gas stream (St 909), and separate the tritium from {sup 41}Ar and collect the tritium for measurement (St 727 and St 707). This system has demonstrated on-line tritium measurements as low as 20 {mu}Ci per sample with typical decontamination factors from {sup 41}Ar of 10{sup 7}. In addition, laboratory studies aimed at the recovery of tritium from graphitic targets have demonstrated further process applications for these getters. Prototypical gas cooled reactor targets, containing encapsulated {sup 6}Li, were irradiated at the Advanced Test Reactor at this laboratory. Samples were then heated to high temperatures to allow diffusive release of the tritium into a flowing helium stream. St 909 purifier and St 727 collector getters have been employed to demonstrate an efficient tritium recoverymore » process. 14 refs., 4 figs., 1 tab.« less