Non-evaporable Getter Pumps Research Articles

Construction of SuperKEKB vacuum control system and its eight years operation experience

SuperKEKB has two main rings (MRs), namely low- and high-energy rings, with circumferences of 3 km; beam transport (BT) lines; and a positron damping ring (PDR). We upgraded the MRs and BT line vacuum control systems and designed a new PDR vacuum control system for upgrading KEKB to SuperKEKB.Here, we describe the basic configuration of the vacuum control system, which includes the interlock logic (gate valve open/closed control, non-evaporable getter pump activation, and beam abortion). We subsequently present the collimator driving system and the cooling water control system for the beam pipe of the final focusing superconducting quadrupole magnet as examples of special SuperKEKB vacuum control systems. Examples of problems in the SuperKEKB vacuum control system, including the discharge at the high-voltage connector of the ion pump, stoppage of the cooling water pump for the vacuum system, and failure of the collimator position measurement device are described.

Design and implementation of intelligent control system for non-evaporable getter pumps

Abstract An intelligent control system for Non-Evaporable Getter (NEG) pumps was designed and developed. The main functions of the system include remote monitoring and remote control of key parameters of the NEG power supply, intelligent control of NEG working status according to NEG saturation status and vacuum chamber status, especially intelligent warning and protection of NEG from vacuum leaks and NEG supersaturation. The intelligent control system is proven stable and reliable, which provides a feasible logic architecture and control design for NEG pump application in future fusion devices.

First results of non-evaporable getter pump studies for the application in the EAST tokamak

Enhanced particle exhaust is pivotal in optimizing fuel recycling and bolstering plasma performance within fusion reactors. Non-Evaporable Getter (NEG) pumps, renowned for their robust high-temperature tolerance, high pumping speeds and large adsorption capabilities, emerge as highly promising candidates for augmenting the particle exhaust efficiency of tokamaks. Rigorous evaluations have been undertaken to ascertain their pumping efficacy within a vacuum testing setup and the EAST tokamak environment. Experimental data have consistently demonstrated that NEG pumps maintain stable operation across a broad temperature range, from ambient conditions to 200 °C, with a notable direct correlation observed between the pumping speed and the ambient temperature. Their performance surpasses that of conventional cryopumps, especially at D2 gas pressures exceeding 0.1 Pa. Additionally, the application of nitrogen passivation has been validated as an effective method to modulate the pumping speed and to mitigate the risk of hydrogen embrittlement and oxygen and carbon contaminations. Despite exposure to the extreme operational demands, including 30 h of plasma exposure, and lithium processing, atmospheric conditions, and water leaks, the NEG pumps preserved approximately 70 % of their initial pumping capacity. These results underscore the compatibility of NEG pumps with the challenging environments of plasma operations, positioning them as a viable and promising solution for particle exhaust in the next-generation fusion reactors.

Characterization of a NEG cartridge under high pressure conditions

The development of advanced sintered pumping elements based on the ZAO® alloy, characterized by a high affinity towards hydrogen and its isotopes, make Non Evaporable Getter (NEG) pumps particularly appealing for applications in fusion research, which typically deal with large fluxes of these gaseous species. NEG getters show high pumping speeds and capacity, excellent reliability with ability to withstand a high number of loading and unloading cycles without showing any type of failure, ease of integration within a complex system (such as a fusion reactor) because of their high specific properties and the simplicity of the mechanism that regulates its operation. These properties make NEG technology particularly suitable for the development of compact, efficient and easily scalable solutions, which are also very safe, since the release of absorbed hydrogen is prevented in the case of power outage or subsystem failures, as it can occur only by providing an adequate amount of heat to the getter material. This paper reports the results of an experimental campaign conducted on a new type of NEG pump, aimed to obtaining an accurate characterization in response to different operating conditions. Hydrogen pumping speed was investigated in a range of pressures of particular interest for the activities of the Divertor Tokamak Test facility (between 0.1 and 10 Pa). The influence of nitrogen absorption and getter material operating temperature on the pumping performances of the NEG pump were also examined. Finally, numerical simulations have been performed to estimate the nominal pumping speed of the NEG pump, that is, the one acting at the absorbing surface, stripped of the effects of the conductance of the paths from the pump NEG to the pressure gauges.

Design of a large nonevaporable getter pump for the full size ITER beam source prototype

An improvement for the vacuum system of the multidriver radio frequency (RF) prototype negative ion source SPIDER has been developed, to allow operating at high RF power, while minimizing the breakdown probability on the outside of the plasma source. A first-of-its-kind large nonevaporable getter (NEG) pump, based on a modular design of 384 cartridges totaling about 350 kg of ZAO® alloy (composed by Zr-Ti-V-Al) with an installed pumping speed at a room temperature of 330 m3/s for hydrogen, will complement the existing pumping system, based on eight cryogenic pumps and four turbomolecular pumps totaling about 90 m3/s in hydrogen. The vessel pressure during absorption is expected to be between 20 and 40 mPa, while during the getter regeneration, the peak operating pressure will be around 2 Pa. The NEG pump will use an additional vessel module, with integrated thermal shields to protect the in-vessel components during activation and regeneration of the pump, to be carried out at temperatures in the range of 550–600 °C. Integrated thermal analyses were carried out to verify the low heat load on pre-existing in-vessel components with a low limit of acceptable temperature, and to provide boundary conditions for the mechanical verifications of the pump structure. The scenario of cyclic hydrogen load was calculated considering the SPIDER operation modes, the expected gas throughput, and the cumulated load to the pump, to determine the regeneration temperature and auxiliary pumping necessary to make the regeneration duration compatible with the high availability of the system. The upgrade of the auxiliary pumping system is also described, as well as the mitigation of air or water exposure risk during regeneration of the NEG pump.

Zero-length conflat fin-type nonevaporable getter pump deposited with oxygen-free palladium/titanium

A zero-length conflat fin-type nonevaporable getter (NEG) pump deposited with oxygen-free palladium/titanium (Pd/Ti) has been developed. The NEG pump was activated by baking and its pumping speeds were measured as a function of baking time and baking temperature. The NEG pump can be fully activated by baking at 150 °C for 12 h and exhibits initial pumping speeds of 2340 L s−1 for H2, and 1440 L s−1 for CO. The initial pumping speeds of the oxygen-free Pd/Ti thin film after baking at 150 °C were estimated to be 3.2 L s−1 cm−2 for H2 and 7.6 L s−1 cm−2 for CO. The morphologies of oxygen-free Pd/Ti thin films on the partition plates and the bottom were examined by scanning electron microscopy, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The Ti thin film was completely coated with Pd on the bottom, whereas the partition plates were covered by Pd/Ti nanostructures. The present NEG pump is ideal for maintaining ultrahigh vacuum below 10−8 Pa, because its pumping speeds for H2 and CO are quite large, and because it can be fully activated by baking at 150 °C for 12 h.

Conceptual design of the Gas Injection and Vacuum System for DTT NBI

The Divertor Tokamak Test (DTT) is a new experimental facility whose construction is starting in Frascati, Rome, Italy; its main goals are improving the understanding of plasma-wall interactions and supporting the development of ITER and DEMO. DTT will be equipped with a Neutral Beam Injector (NBI) based on negative deuterium ions, designed to inject 10 MW of power to the tokamak.A fundamental system for the good operations of the DTT NBI will be its Gas injection and Vacuum System (GVS). Indeed, the efficiency of the entire NBI strongly depends on the good performance of its GVS.The GVS for DTT NBI will be composed of two systems working in parallel: a grounded section connected to the main vacuum vessel, and a high voltage part connected to the ion source vessel and working at −510 kV voltage. The grounded part will feature a fore vacuum system (given by screw and roots pumps) plus a high vacuum system based on turbo-molecular pumps located on the side walls of the vessel and Non-Evaporable Getter (NEG) pumps located inside the vessel on the upper and lower surfaces. On the other hand, the high voltage part will feature a fore vacuum system (given by two compact screw pumps mounted on the external surface for the ion source vessel) plus a high vacuum system based on turbo-molecular pumps also located on the sidewalls of the ion source vessel. A dedicated deuterium gas injection will feed the process gas to the ion source and the neutralizer.This paper gives a description of the conceptual design of the GVS for DTT NBI, and of the procedure followed to optimize this system considering the operational requirements and the other constraints of the DTT NBI.

A power-free vacuum suitcase for sample transfer and cryogenic optical characterization of sensitive 2D materials

Although some of the 2D layered materials like graphene and h-BN are stable in ambient condition, many other ones like the magnetic metal halogens CrI3 might degrade quickly in air due to oxidation or hydrolyzation that drastically affect the intrinsic properties of the pristine samples. Thus, a clean environment is highly demanded for such sensitive 2D materials during storage or transferring between synthesis and characterization setups. Additionally, variable sample temperature is crucial for characterization as well. Here, we demonstrate a specially designed vacuum suitcase that meet these challenges. It utilizes power-free non-evaporable getter pump to provide the ultra-clean vacuum environment for up to 5 samples, which could be maintained at 10−8 mbar level for 5 h and 10−7 mbar level for more 20 days. One of the samples is stored on a liquid nitrogen cooled (∼80 K–300 K) cryogenic stage, which is optimized for optical characterizations (Raman spectroscopy etc.) through a glass window. Such power-free vacuum suitcases would facilitate the clean environment sample transfer and variable temperature optical characterization of as grown sensitive 2D materials.

Nonevaporable getter-MEMS for generating UHV conditions in small volumina

The industrial use of quantum sensors requires further miniaturization of the experimental peripherals, i.e., the high vacuum chamber, laser technology, and control electronics. A central part of the high vacuum chamber is the maintenance of vacuum conditions. For this purpose, a prototype of a compact, i.e., miniaturized, ultrahigh vacuum pump in the form of a nonevaporable getter (NEG) pump at a wafer level (MEMS), is developed within the scope of this work. With regard to the basic conditions of the functionality of the NEG, a miniaturized heating plate with temperature sensors is analytically and numerically developed, constructed, and characterized in an ultrahigh vacuum test stand. This is followed by the integration of the NEG into the existing system, which, in connection with the characterization of material-specific parameters, enables a first correlation of heat input and pumping power. Thus, performance data of the getter-MEMS under high-vacuum confinement confirm its usability for quantum sensors. In addition, optimization potentials are shown with regard to all partial aspects of the MEMS.

Focus on software, data acquisition, and instrumentation

Focus on software, data acquisition, and instrumentation

Development of an EPU vacuum system using lumped NEG-ion combination pumps

A vacuum design based on five lumped ZAO® non-evaporable getter (NEG) pumps (CapaciTorr® Z 200 × 2 and NEXTorr® Z 200 × 3) was developed to construct a vacuum system of elliptically polarized undulator (EPU). The vacuum tests, including measurements of the base pressure and the sorption capacity of CO, and the pressure-rise test on turning off the ion pumps, were performed to evaluate the vacuum performance of this design. Two such EPU vacuum systems were installed in the storage ring of Taiwan Photon Source (TPS) in 2020 and were conditioned with synchrotron radiation, but without baking. The experimental results show that their dynamic pressures achieved less than 3 × 10−12 mbar mA−1 after an accumulated beam dose 100 A h.

Improved vacuum system for high-power proton beam operation of the rapid cycling synchrotron

The vacuum system in the rapid-cycling synchrotron of the Japan Proton Accelerator Research Complex has been operated for more than 10 years. It becomes evident that the high-power beam operation has more powerful effects on the vacuum system than expected at the time of the design. Those effects of the high-power beam are categorized into two types of events, the malfunction of vacuum equipment and the large pressure rise. A specific example of the former event is the failure of the turbomolecular pump (TMP) controller by the full loss of a single-shot high-intensity beam. The TMP itself is also damaged by a bearing crush due to a touch down without braking the rotor. We have developed a TMP controller that can connect with long power and control cables of more than 200 m lengths. This length makes the controller be installed in a control room where there is no radiation influence. The TMP with high-strength bearing has been also developed. The TMP system becomes tolerant to a large loss of the high-intensity beam by using such a controller and a TMP. The latter event is an extreme pressure rise with increasing the beam power. The dynamic pressure behaviors during the beam operations are investigated to understand the outgassing mechanism by the beam. It is indicated that the pressure rise mechanism is a result of the ion-stimulated gas desorption. The analytical calculation based on the ion-stimulated gas desorption model well reproduces the measured dynamic pressure. The calculation also shows that, among the parameters, a larger pumping speed per unit length $s$ and a smaller initial surface density of the adsorbed molecules ${q}_{0}$ are required to suppress the extreme pressure rise. The nonevaporable getter (NEG) pumps are additionally installed to obtain the larger $s$ and smaller ${q}_{0}$. It is confirmed by simulating the beam line pressure distribution that the additional NEG pumps are effective to obtain the larger $s$ in every position along the beam line. The ability of the NEG pump to keep a low pressure during the vacuum system shutdown, which can contribute to maintain the small ${q}_{0}$, is examined by the buildup test. It is finally confirmed that the dynamic pressure during the high-power beam is effectually suppressed.

Robustness of ZAO based NEG pump solutions for fusion applications

Non Evaporable Getter (NEG) technology has been studied as an alternative pumping solution in facilities for fusion research since the 80 s. The recent development of a new generation of Zr-V-Ti-Al (ZAO®) getter alloys with improved features makes NEG technology an attractive option in several fusion applications, including in particular, Neutral Beam Injectors (NBI). The main advantages of ZAO® NEG pumps are related to the high pumping speed for H2, the high capacity that results into a very promising availability, the ease of integration and the low power consumption. From the vacuum point of view, research fusion facilities are in the high vacuum pressure range (e.g. 1∙10−6 ÷1∙10-5 Pa background pressure) and may present leaks and significant outgassing from internal components. Specific activities have been devoted to test the NEG pump robustness, i.e. the ability to maintain adequate performances in conditions very far from UHV. In particular, the effects of carbon oxides and hydrocarbon adsorption have been investigated, as well as the outgassing from materials like polyimide or even fluorinated polymers as PTFE. The results show that the ZAO® getter material is intrinsically robust, able to perform repeated H2 adsorption/desorption cycles with stable performances, and recover most of the original pumping speed even after significant exposure to hydrocarbons and fluorine species. These outcomes give promising indications for the future use of NEG solutions in real fusion facilities.

Non-evaporable getter pump operations in the TCV tokamak

A non-evaporable getter pump using the ZAO alloy was installed on TCV and operated during the 2019 experimental campaign. The pump performance, determined from in-situ pumping speed measurements, indicates that current getter pump technologies are well suited to tokamak operations with high power exhaust plasmas, and provide an interesting alternative for applications in fusion experiments.

Enhanced observation time of magneto-optical traps using micro-machined non-evaporable getter pumps

We show that micro-machined non-evaporable getter pumps (NEGs) can extend the time over which laser cooled atoms can be produced in a magneto-optical trap (MOT), in the absence of other vacuum pumping mechanisms. In a first study, we incorporate a silicon-glass microfabricated ultra-high vacuum (UHV) cell with silicon etched NEG cavities and alumino–silicate glass (ASG) windows and demonstrate the observation of a repeatedly-loading MOT over a 10 min period with a single laser-activated NEG. In a second study, the capacity of passive pumping with laser activated NEG materials is further investigated in a borosilicate glass-blown cuvette cell containing five NEG tablets. In this cell, the MOT remained visible for over 4 days without any external active pumping system. This MOT observation time exceeds the one obtained in the no-NEG scenario by almost five orders of magnitude. The cell scalability and potential vacuum longevity made possible with NEG materials may enable in the future the development of miniaturized cold-atom instruments.

Reduction of waveguide vacuum trips in CEBAF accelerating cavities with a combination ion pump and non-evaporable getter pump

Pressure spikes in the fundamental power coupler waveguide are a significant source of trips during the operation of both original and refurbished superconducting radio-frequency cavities installed in the CEBAF accelerator. In its original configuration, two waveguides from a cavity-pair are connected to a single 32 l/s ion pump. In 2017 a new cavity-pair was installed in a refurbished cryomodule in which a NEXTorr®D200-5 combination ion pump and non-evaporable getter pump was installed for each waveguide. It is shown that hydrogen is the dominant residual gas in the waveguide and simulations with Molflow+ indicated that the new pumping scheme allows reducing the pressure at the end of the waveguide by a factor of ∼5, compared to the original configuration. The new cavity-pair has been operating in CEBAF for a total of 431 days and it only had a total of 3 trips due to vacuum spikes in the waveguide.

Development of highly efficient NEG pumping system for EBIS.

Ultrahigh vacuum inside the ion trap volume is crucial for stable and reliable operation of an Electron Beam Ion Source (EBIS). We have developed and tested a compact linear pumping system based on the ZAO Non-Evaporable Getter (NEG) module with high pumping speed and enhanced sorption capacity for all active gases. Due to its minimal transverse dimensions, the system can be mounted adjacent to the ion trap inside a superconducting solenoid bore and will provide a pumping speed of the order of 1000 l/s for all active gases in that area. An externally supplied current (100 A DC) is used to heat the ZAO NEG up to 650 °C for more than 1 h, which is required for pump activation and/or reactivation cycles. The pumping system is being developed for use in the Extended EBIS Upgrade which is presently in progress at BNL. The design of the system and results of multiple tests are presented and discussed.

Commissioning of vacuum system for SuperKEKB positron damping ring

The first stage commissioning of the new positron damping ring, which was constructed in the upgraded injector system of the SuperKEKB, was carried out from February to July 2018. Vacuum scrubbing in the arc sections, which occupy most of the ring, progressed smoothly, and a beam lifetime of 1000 s was obtained with a stored beam current of 10 mA and a beam dose of 0.7 A h. However, the beam lifetime did not increase with subsequent vacuum scrubbing because the beam lifetime was primarily determined by the Touschek effect. The residual gas composition during beam operation was typical of what would be expected for a vacuum system pumped by nonevaporable getter pumps. Rough Molflow+-based estimates of the photon-stimulated desorption yields of the beam pipe at the arc sections revealed that they decreased to 1.4 × 10−4 molec. photon−1 for H2 and to 2.3 × 10−5 molec. photon−1 for CO at a beam dose of 2 A h, which corresponds to a photon dose of 1 × 1023 photons m−1.

New installation of in-vessel Non Evaporable Getter (NEG) pumps for the divertor pump in the LHD

A case of the application of Non Evaporable Getter (NEG) pumps to fusion devices is discussed. Compared with other pumping technologies used in fusion devices, the NEG pumps have advantages in terms of operation temperature at 100–200 °C (in which there is a high tolerance of the temperature increase due to a plasma radiation and/or an unexpected heat load from heating devices), low power consumption and compactness. Moreover, in the case of a power outage getters continue pumping and do not release hydrogen and its isotopes. The NEG pumps have been installed as an in-vessel pump into the divertor region in the Large Helical Device (LHD) for the first time. The pumping performance test shows that the effective pumping speed is 10 m3/s in hydrogen, which is close to the target value. In addition, the exposure of the NEG pumps to boronization and glow discharge treatments have been tested. While the boronization and glow discharge under noble gases do not show effect on the pumping performances of the NEG pumps, the establishment of an operational scenario including hydrogen and deuterium glow discharges consistent with other pumping facilities is still an aspect to be refined. However, the use of NEG pumps in LHD divertor is a milestone for the possibility of using this technology in future fusion devices.

Characterization of ZAO® sintered getter material for use in fusion applications

The use of non-evaporable getter (NEG) pumps is common in many UHV applications, and the properties of the new sintered getters based on the ZAO®alloy make them appealing for applications dealing with large fluxes of hydrogen and its isotopes, as typically occurs in fusion research. In particular, the use of NEG pumps is interesting for the vacuum system of negative ion-based neutral beam injectors, which require huge deuterium gas throughputs for long durations. The key advantages of a NEG pumping solution are the high specific pumping speed and capacity, the ability to withstand a large number of absorption/desorption cycles, the ease of integration. In addition, NEG do not release hydrogen unless power is supplied to heat them, addressing an important safety issue related to uncontrolled release in case of power outage or subsystem failures.This paper reports the experimental characterization of ZAO®sintered getters, in pressure regimes and sorption amounts relevant for the use in the next generation NBI. Single discs and complete pumps were characterized in different conditions of H2/D2 pressure between 10−4 and 10-1Pa and operating temperatures up to 150°C. In particular, the feasibility of getter regeneration within time windows compatible with current NBI operation scenarios was demonstrated.