Getter Pump Research Articles

Flowmeter for very low gas flows of inert gases

Gas flow was measured by using constant volume-variable pressure method. The gas flow is measured by pressure rise method using spinning rotor gauge (SRG). The design is relatively simple and has no precisely movable parts compared to the constant pressure-variable volume method. Due to outgassing effect we used a non-evaporable getter pump in order to diminish the influence of hydrogen outgassing on measured gas flow. Lower limit of pressure rise method is 5×10−10mbarl/s and this is extended to 3×10−12mbarl/s by using constant conductance method. With this flow meter we generated a calibration pressure of Argon in our calibration system in the range from 8×10−13mbar up to 2×10−7mbar.

Identification of V-type nerve agents in vapor samples using a field-portable capillary gas chromatography/membrane-interfaced electron ionization quadrupole mass spectrometry instrument with Tri-Bed concentrator and fluoridating conversion tube.

A field-portable gas chromatography-mass spectrometry (GC-MS) system (Hapsite ER) was evaluated for the detection of nonvolatile V-type nerve agents (VX and Russian VX (RVX)) in the vapor phase. The Hapsite ER system consists of a Tri-Bed concentrator gas sampler, a nonpolar low thermal-mass capillary GC column and a hydrophobic membrane-interfaced electron ionization quadrupole mass spectrometer evacuated by a non-evaporative getter pump. The GC-MS system was attached to a VX-G fluoridating conversion tube containing silver nitrate and potassium fluoride. Sample vapors of VX and RVX were converted into O-ethyl methylphosphonofluoridate (EtGB) and O-isobutyl methylphosphonofluoridate (iBuGB), respectively. These fluoridated derivatives were detected within 10min. No compounds were detected when the VX and RVX samples were analyzed without the conversion tube. A vapor sample of tabun (GA) was analyzed, in which GA and O-ethyl N,N-dimethylphosphoramidofluoridate were detected. The molar recovery percentages of EtGB and iBuGB from VX and RVX vapors varied from 0.3 to 17%, which was attributed to variations in the vaporization efficiency of the glass vapor container. The conversion efficiencies of the VX-G conversion tube for VX and RVX to their phosphonate derivatives were estimated to be 40%. VX and RVX vapors were detected at concentrations as low as 0.3mg m-3 . Gasoline vapor was found to interfere with the analyses of VX and RVX. In the presence of 160mg m-3 gasoline, the detection limits of VX and RVX vapor were increased to 20mg m-3 . Copyright © 2017 John Wiley & Sons, Ltd.

Fivefold enhancement in stability of organic light-emitting diodes with addition of non-evaporable getter pumps

We demonstrate a significant enhancement of the operational stability of organic light-emitting diodes (OLEDs) by fabricating the devices under ultrahigh-vacuum (UHV) conditions in the region of 10−10–10−11 Torr. The UHV condition is achieved by utilizing non-evaporable getter pumps together with regular turbo molecular pumps in an OLED deposition chamber. The short-term stability of the OLEDs is prolonged fivefold because of the removal of detrimental gases, especially water. We suggest that ultra-clean fabrication conditions are indispensable for revealing the true intrinsic degradation mode of OLEDs. Additionally, we analyze the effect of operating residual gas analyzers during the device fabrication.

Helium neutral beam injection into ASDEX Upgrade

ASDEX Upgrade's (AUG) neutral beam injection (NBI) system is primarily designed for deuterium injection and delivers 20MW heating power from two injectors with four beams each at 60 and 93keV, respectively. As opposed to the cryo pumps of the JET NBI, the Ti getter pumps of the AUG NBI with a pumping speed of 3×106ℓ/s for hydrogen do not pump helium at all, leaving only the conventional pumping system with <6×103ℓ/s for He. This imposes constraints on the possible operation in helium.In order to prepare for AUG He plasma campaigns, serious trials to operate the AUG NBI with He began in 2014. It was found that despite the lack of high speed pumping up to two beams per injector could be operated simultaneously at reduced feed gas flow without particular restrictions on the beam-on time. For injector 1 the power per beam was limited to 550kW at 40keV by the required filament current in its arc sources, while for injector 2 the limitation came from the bending magnet's power supply that restricted the beam energy to 68keV and the NBI power to 730kW per beam. Thus the maximum available NBI heating power in He amounts to 2.6MW for 10s, the maximum discharge duration of AUG. Helium neutral beam injection into plasma was first tried out in 2014 for two discharges. In 2015 a dedicated He campaign used He NBI in a total of 44 discharges. As He is almost not pumped in the injectors the neutral gas flow into the torus is comparable with the total He gas puff.

Vacuum system of positron damping ring for SuperKEKB

To satisfy the requirements of high beam quality for positron injection into the SuperKEKB electron-positron collider, a new damping ring (DR) is constructed in an upgraded injector system. The DR has two arc sections and two straight sections. In the arc sections, the beam pipes have beam position monitor blocks, pumping ports, radio-frequency-shielded bellows, and special connection flanges to fit narrow spaces between closely located magnets. The beam pipes have antechambers on both sides of a beam channel to deal with synchrotron radiation (SR) which irradiates both sides of the beam pipes. The antechambers are also effective in reducing the electron cloud in the beam channel. To remove the heat caused by SR irradiation, a water cooling system is also required in the arc sections. In the straight sections on the other hand, an antechamber structure and a water cooling system are not necessary, and the beam pipes are much simpler than those in the arc sections. Required beam lifetime due to residual gas scattering is longer than 1000 s, and the average pressure should be lower than 1 × 10−5 Pa. Nonevaporable getter (NEG) pumps are mainly used with auxiliary ion pumps, and the average effective pumping speed in the arc sections is approximately 0.013 m3 s−1 m−1 (for CO), just after NEG activation. The material of the beam pipes is aluminum alloy. As additional countermeasures against the electron cloud effect, titanium nitride coating and grooved surfacing are adopted. These reduce the secondary electron yield of the inner surfaces of the beam pipes.

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions.

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å-1. The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

Operation of a high-gradient superconducting radio-frequency cavity with a non-evaporable getter pump

The use of non-evaporable getter (NEG) pumps in particle accelerators has increased significantly over the past few years because of their large pumping speed, particularly for hydrogen, compared to the size of the pump. A concern about using such pumps in superconducting radio-frequency (SRF) accelerators is the possibility of shedding particulates which could then migrate into the SRF cavities and produce field emission, therefore degrading the cavity performance. One option to mitigate such issue is to use sintered getter materials which intrinsically offer superior mechanical and particle retention properties. In this article we present the results from cryogenic RF tests of a high-gradient SRF cavity after being evacuated several times with an NEG pump equipped with sintered getter disks and placed in close proximity to the cavity. The results showed that the cavity performance was not affected by the pump up to the quench gradient of 34MV/m. As a result of this study, two such NEG pumps have been installed next to a cryomodule in the CEBAF accelerator to maintain ultra-high vacuum in the SRF cryomodule and two adjacent warm girder sections.

Outgassing analysis of the 14-m-long arc-cell vacuum chambers of the Taiwan Photon Source

An overall outgassing analysis of the large, 14-m-long, ultra-high-vacuum aluminum arc-cell chambers of the Taiwan Photon Source (TPS) was performed using residual gas analyzer (RGA). Pumping primarily by ion pumps (IP) and non-evaporable getter (NEG) pumps, the cells obtained pressures of 6.4 × 10−9 Pa on average, and the main residual gas was H2. The pressure build-up method was adopted to investigate the outgassing of the vacuum chambers. Because active gases (H2, CO, CO2) were primarily pumped by NEG pumps, the increased vacuum pressure here mainly resulted from the inert gas. Therefore, the residual gases measured after switched off the ion pumps were CH4 and Ar. After the ion pumps were baked separately, the outgassing of CH4 was considerably diminished and the lowest achievable vacuum pressure was improved. The outgassing of Ar was primarily responsible for the long-term pressure build-up. Moreover, vacuum pressure measurements and residual gas analyses were performed in situ while a cell chamber was being transported. The vibration of the arc-cell vacuum chamber caused the pressure to rise abruptly; in this case, the outgassing gas measured during transportation was CH4. Once the arc cell was installed, the original level recovered because of the pumping effect of the ion gauges.

Low-cost, high-performance nonevaporable getter pumps using nonevaporable getter pills

Nonevaporable getter (NEG) pumps are widely used for maintaining a clean ultrahigh vacuum (UHV) of ≤10−8 Pa because of their high pumping speeds for hydrogen (H2) and active gases in the UHV region. In addition, they are oil free, evaporation free, sputtering free, sublimation free, magnetic field free, vibration free, economical, compact, lightweight, and energy saving. In the present paper, the authors report a new NEG pump which is composed of commercial 60 NEG pills (ϕ10 × 3 mm; 70 wt. % Zr, 24.6 wt. % V, and 5.4 wt. % Fe), titanium parts, a DN 40 conflat flange, and a tantalum heater. The NEG pills are vertically and radially aligned around the heater to maximize the effective area for pumping. After activation at 400 °C for 30 min, the pumping speeds of the NEG pump were measured with the orifice method. Pumping speeds of 140–130, 200–140, 190–130, and 35–17 l/s were estimated for H2, CO, CO2, and N2 gasses, respectively, in a pumped-quantity range of 0.01–0.1 Pa l. Since the NEG pump is composed of a heating unit and a NEG module, the pumping speeds can be improved by increasing the number of NEG modules. These NEG pumps are favorable alternatives to sputtering ion pumps or titanium sublimation pumps.

A highly miniaturized vacuum package for a trapped ion atomic clock.

We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm(3) in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, it was sealed with a copper pinch-off and was subsequently pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of (171)Y b(+). The fractional frequency stability of the clock was measured to be 2 × 10(-11)/τ(1/2).

Results and problems in the construction phase of the SuperKEKB vacuum system

The SuperKEKB, the upgrade of the KEKB, is an electron–positron collider with asymmetric energies, that is, 7.0 GeV electrons and 4.0 GeV positrons, designed for a luminosity of 8 × 1035 cm−2 s−1. As a key item of the upgrade project, a new vacuum system for the SuperKEKB has been in construction since 2010. Over 1000 beam pipes, vacuum pumps, bellows chambers, and other various vacuum components had almost been fabricated in 2014. All the new beam pipes were baked as a general rule before being installed in the KEKB tunnel. A thin TiN film with a low secondary-electron yield was coated on the inside of the beam pipes for the positron ring as a countermeasure against the electron cloud effect. The performance of the new built-in nonevaporable getter (NEG) pumps and the step-less connection flanges met the expectation. Although several problems such as damage to the bellows chambers due to a large earthquake, cracking of the welding lines of the aluminum beam pipes, and a relatively high air-leak rate at the connection flanges occurred during the construction work, approximately 99% of the beam pipes were successfully installed by the end of October 2015. The activation of the NEG pumps in the tunnel started at the beginning of 2015 and has also been completed in approximately 97% of the ring. The installed beam pipes and the bellows chambers in the tunnel were aligned to their specified positions as the final step of the installation work. The vacuum system was ready in 2015 with the aim of starting the first commissioning in 2016. The various experiences during the construction phase reported here will be a useful reference for the design and construction of other accelerators in the future.

Tritium burning in inertial electrostatic confinement fusion facility

An experiment on tritium burning is conducted to investigate the enhancement in the neutron production rate in an inertial electrostatic confinement fusion (IECF) facility. The facility is designed such that it is shielded from the outside for safety against tritium and a getter pump is used for evacuating the vacuum chamber and feeding the fuel gas. A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used, and its neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. Moreover, the results show good agreement with those of a simplified theoretical estimation of the neutron production rate. After tritium burning, the exhausted fuel gas undergoes a tritium recovery procedure through a water bubbler device. The amount of gaseous tritium released by the developed IECF facility after tritium burning is verified to be much less than the threshold set by regulations.

Vacuum Characteristic of a Chamber Made of Mild Steel

The base pressure and outgassing rate of a mild steel chamber were measured and compared to those of a stainless steel chamber. A combined sputter-ion and non-evaporable getter pump with a nominal pumping speed of 490 l/s generated the base pressure of 2.7×10 ?11 mbar in the mild steel chamber and 1.2×10 ?10 mbar in the stainless steel chamber. The rate-of-rise measurements show that the mild steel has an extremely low outgassing rate of 2.6×10 ?13 mbar l s ?1 cm ?2 , which is about one-order of magnitude smaller than the outgassing rate of the stainless steels. Vacuum annealing of the mild steel at 850oC reduced the outgassing rate further to 8.8×10 ?14 mbar l s ?1 cm ?2 , which was comparable to the outgassing rate of a heat treated stainless steel for extreme-high vacuum use.

Identification of chemical warfare agents from vapor samples using a field-portable capillary gas chromatography/membrane-interfaced electron ionization quadrupole mass spectrometry instrument with Tri-Bed concentrator

A field-portable gas chromatograph–mass spectrometer (Hapsite ER system) was evaluated for the detection of chemical warfare agents (CWAs) in the vapor phase. The system consisted of Tri-Bed concentrator gas sampler (trapping time: 3s−1min), a nonpolar low thermal-mass capillary gas chromatography column capable of raising temperatures up to 200°C, a hydrophobic membrane-interfaced electron ionization quadrupole mass spectrometer evacuated by a non-evaporative getter pump for data acquisition, and a personal computer for data analysis. Sample vapors containing as little as 22μg sarin (GB), 100μg soman (GD), 210μg tabun (GA), 55μg cyclohexylsarin (GF), 4.8μg sulfur mustard, 390μg nitrogen mustard 1, 140μg of nitrogen mustard 2, 130μg nitrogen mustard 3, 120μg of 2-chloroacetophenone and 990μg of chloropicrin per cubic meter could be confirmed after Tri-Bed micro-concentration (for 1min) and automated AMDIS search within 12min. Using manual deconvolution by background subtraction of neighboring regions on the extracted ion chromatograms, the above-mentioned CWAs could be confirmed at lower concentration levels. The memory effects were also examined and we found that blister agents showed significantly more carry-over than nerve agents. Gasoline vapor was found to interfere with the detection of GB and GD, raising the concentration limits for confirmation in the presence of gasoline by both AMDIS search and manual deconvolution; however, GA and GF were not subject to interference by gasoline. Lewisite 1, and o-chlorobenzylidene malononitrile could also be confirmed by gas chromatography, but it was hard to quantify them. Vapors of phosgene, chlorine, and cyanogen chloride could be confirmed by direct mass spectrometric detection at concentration levels higher than 2, 140, and 10mg/m3 respectively, by bypassing the micro-concentration trap and gas chromatographic separation.

Vacuum systems for the TPS accelerator

The Taiwan Photon Source (TPS) is a 3 GeV third generation accelerator light source. The vacuum systems contain an electron storage ring (SR) of 518.4 m in circumference and a concentric booster (BR) of 496.8 m in circumference, linked with the transport lines one from the booster to storage ring (BTS) and the other from the linear accelerator to the booster (LTB). To ensure the highest stability of the electron beam in the storage ring, all the vacuum systems for the SR, BTS, and BR, have been baked to the ultrahigh vacuum (UHV). The aluminum vacuum chambers with the completely oil-free precise manufacturing process provide a lowest surface outgassing rate and lowest broadband impedance for accommodating the beam in stable. The combination of the triode ion pumps and the non-evaporable getter (NEG) pumps provides a superior pumping efficiency and the ultimate pressure < 5 nPa. The 24 arc-cell vacuum systems, each about 14 m in length, have been baked to the UHV and sealed in the laboratory prior to transport to the TPS tunnel for the installation. Other vacuum systems were installed and baked on site in parallel. After completing the installations, commissioning of TPS was started in August 2014.

SuperKEKB 真空機器制御システムと総合試験

SuperKEKB is an upgrade project of KEKB, which is a double ring collider of electron and positron beams. The vacuum control system has also been upgraded. Key changes related to the framework of the system are that Computer Automated Measurement And Control (CAMAC) system as a data logger and VME computer as an Input Output Controller (IOC) of Experimental Physics and Industrial Control System (EPICS) have been replaced with CompactRIO (cRIO) and a Linux CPU module of Programmable Logic Controller (PLC), respectively. As an integrative and practical test, we have executed the final evacuation process, including the baking of sputter ion pumps and the activation of Non-Evaporable Getter (NEG) pumps, in a section between two gate valves in the SuperKEKB main ring. The control system supervised the discharge currents of ion pumps, readings of Cold Cathode Gauges (CCGs), heating power for the activation and so on. The new control system is in preparation for a start of the beam commissioning on fiscal 2015 in Japan.

The Design of the Fixture for the Thin Wall Cone Parts

When turning and grinding the long axis with cone thin-walled, they are clamped to be deformation easily and positioned difficultly. Based on the existing theory of clamping with the conical sleeve, we design a new type of fixture in this paper. The outer cone of the fixture cling to the inner cone of the workpiece, it is sealed hermetically at the both ends. The head of the sleeve stretch out of a cylindrical boss, we can use the three-jaw chuck to position it on the machine tool. Also we use the steady rest to fix the end of the sleeve. The steady rest connect with the shell of a rotary joint. The end of the rotary joint screw with the sleeve, the other end of it is connected with a getter pump. It formatted a vacuum between the sleeve and the workpiece by the use of holes around the circumference of the sleeve. The utility model to the fixture used for thin wall conical parts with long shaft.

Study of the ultra-high-vacuum system of the 14-m-long vacuum chamber of the Taiwan Photon Source using the pressure build-up method

The pressure build-up method was suitable for diagnosing and qualifying the vacuum status in the chamber and thus can be applied to determine the maintenance and recovery of a large vacuum system. The thermal outgassing rate and the pumping speed can be estimated using this method. In its electron storage ring, the Taiwan Photon Source (TPS) contains 24 aluminum arc-cells that are 14 m in length. Each cell was baked ex situ to 150 °C for 24 h in the laboratory to achieve ultra-high-vacuum. The cells reached 6.4 × 10−9 Pa on average, under pumping with primarily ion pumps and non-evaporable getter (NEG) pumps. The thermal outgassing rate, the pumping speed, and the residual gas compositions of a typical cell were analyzed. With all ion pumps turned off for more than 80 h, the vacuum pressure rose to approximately 8 × 10−7 Pa. The measured pumping speed was 6.9 × 10−4 m3∙s−1 on average for most of the cells extractor gauges associated with major inert gases in the 14 m-long cells. An experimental analysis of the emitted residual gases indicated that the gas in the aluminum vacuum chamber was primarily CH4 after the ion pumps were deactivated. Moreover, the one-cell vacuum chamber recovered to UHV status on using the pressure build-up method, including calculation of the outgassing rate and the pumping speed.

Experimental investigation of an optimum configuration for a high-voltage photoemission gun for operation at≥500 kV

We demonstrated the generation of a 500-keV electron beam from a high dc voltage photoemission gun for an energy recovery linac light source [N. Nishimori et al., Appl. Phys. Lett. 102, 234103 (2013)]. This demonstration was achieved by addressing two discharge problems that lead to vacuum breakdown in the dc gun. One is field emission generated from a central stem electrode. We employed a segmented insulator to protect the ceramic insulator surface from the field emission. The other is microdischarge at an anode electrode or a vacuum chamber, which is triggered by microparticle transfer or field emission from a cathode electrode. An experimental investigation revealed that a larger acceleration gap, optimized mainly to reduce the surface electric field of the anode electrode, suppresses the microdischarge events that accompany gas desorption. It was also found that nonevaporable getter pumps placed around the acceleration gap greatly help to suppress those microdischarge events. The applied voltage as a function of the total gas desorption is shown to be a good measure for finding the optimum dc gun configuration.

Magnetic field superimposed cold field emission gun under extreme-high vacuum

A magnetic-field superimposed cold field emission gun (M-FEG) was developed for a 1.2-MV holography transmission electron microscope (TEM). Differential pumping using three nonevaporative getter pumps reduced the pressure of the gun to an extreme-high vacuum of 3 × 10−10 Pa and provided a stable probe current. The 90% decrease time, at which the current falls to 90% of the initial value, was 900 min. The current variation over the course of 8 h was 5.2%. The superimposed magnetic field provided large probe currents ranging from 1 to 170 nA for total currents ranging from 1 to 300 μA. The reduced pressure caused the angular current density to be twice that of a conventional field emission gun operating at 10−8 Pa. This increase can be explained by the difference between current densities emitted from the clean and adsorbed emitter surfaces. These results show that the developed M-FEG can provide the 1.2-MV TEM with a bright and stable emission current.