Vacuum Flanges Research Articles

Design and performance of indium seals for size-constrained tunable laser spectrometers.

Indium seals have been used extensively in ultra-high vacuum and cryogenic applications. Typically, these seals use indium alongside or in place of other metal gaskets in stainless-steel vacuum flanges, with some custom applications for flanges sealing directly with glass (optics or tubes). Here, we present the design and performance of three pressed indium seals (99.99% In) between aluminum and 0.5 in. diameter sapphire optics and aluminum and gold coated Kovar semiconductor packages (TO-66 and TO-39). Test fixtures were designed to mimic those of future tunable diode laser spectrometers for Earth, planetary, and manned spaceflight environmental monitoring applications. Successful high-hermeticity seals [<10-10 atm cc/s (He)] were achieved for all seals formed with sufficient pressure applied to allow indium to flow between mating surfaces. The hermeticity of the seals was maintained after temperature cycling (-10 to +80 °C, 20 cycles), with the optical seals surviving extended duration tests (-55 to +85 °C, per MIL-STD-883). Semiconductor packages (TO-39) subjected to these extended tests saw a moderate increase in leak rate [∼5 × 10-9 atm cc/s (He)]; however, further testing showed that either the glass-metal package seals or the indium were affected (the sample size was too small to draw firm conclusions for future applications). Overall, these results suggest long-term survivability of indium seals for Kovar-aluminum and sapphire-aluminum interfaces [>10 years at 10-10 atm cc/s (He)], where the coefficient of thermal expansion differs by approximately four times.

Validation Experiments for In Situ Ne Isotope Analysis on Mars: Gas Separation Flange Assembly Using Polyimide Membrane and Metal Seal

The Martian atmospheric Ne may reflect recent gas supply from its mantle via volcanic degassing, due to its short (∼100 Myr) escape timescale. The isotopic ratio of the Martian atmospheric Ne would therefore provide insights into that of the Martian mantle, further suggesting the origin of Mars volatiles during planetary formation. Mass spectrometric analysis of the Martian atmospheric Ne, however, has faced challenges from interference between 20Ne+ and 40Ar++. Previous studies using a polyimide membrane for 20Ne/40Ar separation were limited by the drawbacks of elastomeric O-rings to support the membrane, such as low-temperature intolerance, outgassing, and the need to endure environmental conditions during the launch and before/after landing on Mars. This study proposes a new method employing a metal C-ring to secure a 100 μm polyimide sheet within vacuum flanges. Environmental tests, including vibration, shock, extreme temperatures, and radiation exposure, were conducted on the gas separation flanges. Pre- and post-test analyses for He, Ne, and Ar demonstrated the membrane-flange system’s resilience. Gas permeation measurements using terrestrial air effectively permeated 4He and 20Ne, while reducing 40Ar by more than six orders of magnitude. This study achieved a <3% accuracy in determining the 20Ne/22Ne ratio, sufficient for assessing the origins of Ne in the Martian mantle. Furthermore, experiments with a 590 Pa gas mixture simulating the Martian atmosphere achieved a 10% accuracy for the 20Ne/22Ne isotope ratio, with gas abundances consistent with numerical predictions based on individual partial pressures. These results validate the suitability of the developed polyimide membrane assembly for in situ Martian Ne analyses.

Novel C-Shaped Shape Memory Alloy Connectors for Vacuum Flanges: Modeling and Tests

Shape memory alloy (SMA)-based fasteners and connectors represent a class of successful SMA components that are increasingly used especially in marine or aerospace applications. The present paper aims to investigate novel C-Shaped SMA connectors for room-temperature vacuum pipes within particle accelerators. The proposed connectors exhibit the two-way shape memory effect (TW-SME), so they can generate significant axial recovery forces and they can be dismounted by temperature variations. Proper thermo-mechanical training procedures were performed to tune the mechanical and functional response of the connectors to make them suitable for the investigated application. The thermo-mechanical and functional response of the SMA fasteners in both free and constrained recovery conditions were assessed by strain gauge and extensometer tests as well as by finite element analyses based on a constitutive model, recently developed by the authors, accounting for TW-SME and plasticity. Comparison between experimental and numerical results validates the proposed model. Moreover, results give useful, important information in terms of SMA transformation temperatures, generated recovery forces as well as shape recovery capabilities.

Material Plasma Exposure eXperiment (MPEX) High Heat Flux Bellows for Component Alignment in High Microwave Environment

The Material Plasma Exposure eXperiment (MPEX) device is a linear plasma device developed to perform plasma material interaction experiments under the conditions prototypic of a fusion reactor divertor. MPEX has multiple systems that must be precisely aligned to the plasma axis, including an electron cyclotron heating system that emits up to 400 kW of microwave power into the vacuum vessel. Five distinct systems require precise alignment on the MPEX device, thus requiring four bellows, all of which are adjacent to the plasma at a relatively high heat flux of approximately 47 kW/m2 and microwave power regions. The MPEX high heat flux bellows (HHFB) is designed to deliver 6 degrees of freedom positioning. The HHFB includes titanium–zirconium–molybdenum (TZM) inserts that are brazed into a Glidcop AL-15 body using a high-temperature braze alloy, thus blocking direct line of sight to an edge-welded bellows from the plasma and microwave screen to block microwaves from the bellows. A custom ConFlat knife edge is machined into the Glidcop AL-15, so the vacuum flanges do not need a braze or weld joint on the vacuum interface. Fingerstock or copper mesh is used to restrict microwave power from entering the interstitial space between the water-cooled Glidcop AL-15 body and edge-welded bellows. Glidcop AL-15 was selected as the material of choice for the water-cooled body because it can maintain mechanical integrity at elevated temperatures, and it also allows for a high-temperature braze. TZM was selected for its machinability and compatibility with vacuum and plasma requirements. A test article is also being considered for a similarly shaped component, the MPEX limiter, that will demonstrate the integrity of the braze joint under high thermal load. Results from this testing will be extrapolated to deduce the lifetime and integrity of the HHFB design.

Photoacoustic optical absorption measurement of aerosols

Atmospheric optical absorption, including the contribution from aerosols, is important in modeling propagation of laser beams and for climate research. Photoacoustic methods have been used in the past for this purpose, as they directly measure absorption, rather than the sum of absorption and scattering. Acoustic operating frequency determines the sensed aerosol size range. The design of a windowless double-Helmholtz photoacoustic aerosol sensing system, operating at an acoustic frequency near 150 Hz, with the capability to measure an optical absorption with a 1/e length of 1 Mm, will be presented. In this design, environmental noise limits the instrument sensitivity. To improve immunity to environmental noise with an open resonator, an aluminum acoustic enclosure was built around the system, with welded vacuum flanges for inputs and outputs. Inlet and outlet acoustic mufflers were designed to limit the in-band noise entering the measurement system. A modulated 10 W 1064 nm fiber laser was used as the excitation source, and a high-sensitivity microphone placed within the open-cell cavity was used to measure the internal photoacoustic pressure fluctuations. The system was modeled using various computational tools, including MATLAB, Simulink, and ANSYS, and then was constructed and tested. Lab measurement results will be presented.

Optical Boundary Reconstruction With Visible Camera in the EXL-50 Spherical Tokamak

Plasma position and shape parameters are essential for equilibrium control and physics analysis in a tokamak. Such information is often obtained via optical boundary analysis. In this study, a new analysis of the visible image histogram of a high-speed high-resolution camera is presented which can effectively distinguish between the foreground information (showing the plasma of interest) and the background information (showing the inside views of the vacuum vessel wall and flanges, and so on). Using this method, we can obtain a reasonable approximation to the plasma boundary close to the last closed flux surface (LCFS) where plasma brightness contrast is greatest. The reliability and accuracy of this method are checked by comparing it favorably with other algorithms for different plasma shapes. The method is successfully tested also when the outboard plasma boundary oscillates in time with a magnitude of 10%.

High Temperature Compatible Conflat Cell with Adjustable Stack Pressure for In-Situ and Operando X-Ray Studies of Lithium-Ion Battery Materials

Lithium-ion batteries have emerged as the dominant energy storage technology for electronic devices, vehicles, and grid-scale applications [1,2]. Further improvements of cell design, components, and materials depend heavily on reproducible characterization. The challenge is to replicate real-world battery operation conditions in laboratory measurements, which makes designing robust in-situ / operando cells a challenging task. Cell materials should be as close as possible to those used in production cells (e.g. steel, aluminum, copper, nickel) [3] and lithium should only react with the test electrode, not with the cell components or the test environment. In addition, a controlled but significant mechanical pressure (0.1 - 1 MPa) should be applied to the electrochemically active material, and in some cases, the cell must operate over a wide temperature range. While existing in-situ and operando electrochemical cell designs meet many of these criteria, no design meets all of them.We have developed a Сonflat in-situ cell for X-ray diffraction studies based on Conflat vacuum flanges and electrical feedthroughs. This cell design is based on readily available components and can provide an ultra-high vacuum compatible seal and controllable and commercially relevant stack pressure over a wide temperature range [4]. Cell sealing is accomplished using knife edges impinging on a copper gasket. Conflat cells have a potential to meet all of the criteria for a robust and reproducible in-situ / operando cell. The challenge lies in properly incorporating an X-ray transparent window for X-ray measurements. While Beryllium windows can be attached to the Conflat flange using metal bonding techniques, such bonding can be cost prohibitive for many laboratories (e.g. thousands of dollars per flange). In our design, we used a readily available steel reinforced epoxy to attach the Beryllium window to the Conflat flange, making it an inexpensive and high quality alternative even for long-term in-situ and operando measurements. In-situ and operando X-ray powder diffraction results from Graphite and Aluminum electrodes cycled at 30℃ and 120℃, respectively, are provided in Fig. 1. Diffraction patterns were combined and plotted as a logarithmic-scale colormap together with the measured cell potential in Fig. 1a) for Graphite and Fig.1b) for Aluminum electrodes [5]. For the C-Li system in Fig.1a), only the C-Li peaks of interest are shown in the ranges of 20°-30° and 75°-85° scattering angle. From the voltage profile in Fig.1a), four intercalation stages can be discerned, as has been extensively reported before, and are marked with dashed red lines. Al-Li phases can be well defined both from the voltage profile and the diffraction pattern. In Fig.1b), the solid vertical lines that do not change their intensity with time, at approximately 42°, 52° and 71° are the peaks from the Beryllium window. The rest of the peaks that change their intensity and position with time can be attributed to the various phases of the Al-Li system that have been reported in our previous ex-situ studies [6]. Phase formation is reversible for both Graphite and Aluminum electrodes and a pure Graphite and Aluminum metal could be recovered when the cell was completely charged again. In both in-situ experiments, the cell performed very well and high quality data was obtained. We will present and discuss the X-ray diffraction data and all of the phases of the C-Li and Al-Li systems in more detail as well as results from the rigorous testing of the cell to assess its superior sealing and longevity [5].[1] M. Li et al., Advanced Materials 30 (33) 1800561 (2018).[2] H. C. Hesse et al., Energies, 10 (12) 2107 (2017).[3] M. Zwicker et al., Journal of Advanced Joining Processes 1 100017 (2020).[4] M.D. Fleischauer et al., Journal of The Electrochemical Society, 166 (2) A398-A402 (2019).[5] O. Sendetskyi et al., Journal of Applied Crystallography, In preparation (2021).[6] M. Ghavidel et al., Journal of The Electrochemical Society, 166 (16) A4034-A4040 (2019).Figure 1. Voltage profiles and operando X-ray diffraction patterns plotted as a log-scale intensity colormap for a) Graphite electrode measured at 30℃ and b) freestanding Aluminum foil electrode measured at 120℃ [5]. Figure 1

Beam measurement of the high frequency impedance sources with long bunches in the CERN Super Proton Synchrotron

Microwave instability in the Super Proton Synchrotron (SPS) at CERN is one of the main limitations to reach the requirements for the High Luminosity-LHC project (increased beam intensity by a factor 2). To identify the impedance source responsible of the instability, beam measurements were carried out to probe the SPS impedance. The method presented in this paper relies on measurements of the unstable spectra of single bunches, injected in the SPS with the rf voltage switched off. The modulation of the bunch profile gives information about the main impedance sources driving microwave instability, and is compared to particle simulations using the SPS impedance model to identify the most important contributions. This allowed us to identify the vacuum flanges as the main impedance source for microwave instability in the SPS, and to evaluate possible missing impedance sources.

Note: Development of target changeable palm-top pyroelectric x-ray tube

A target changeable palm-top size x-ray tube was realized using pyroelectric crystal and detachable vacuum flanges. The target metals can be exchanged easily by attaching them on the brass stage with carbon tape. When silver and titanium palates (area: 10 mm(2)) were used as targets, silver Lα and titanium K lines were clearly observed by bombarding electrons on the targets for 90 s. The intensities were the same or higher than those of previously reported pyroelectric x-ray tubes. Chromium, iron, nickel, copper, and zinc K lines in the x-ray tube (stainless steel and brass) disappeared by replacing the brass stage and the stainless steel vacuum flange with a carbon stage and a glass tube, respectively.

Safely mounting glass viewports to elastomer sealed vacuum flanges

Elastomer sealed vacuum flanges rely on especially sized elastomer O-rings and corresponding grooves to make an air-tight seal. Depending on the materials being sealed to one another, the O-ring/groove sealing mechanism may be designed for a specific percentage compression of the O-ring at the point of flange-to-flange contact. In the case of a glass viewport being sealed to a metal flange, however, direct contact between the glass and a mating metallic flange may produce stresses in the glass that can lead to failure during system evacuation or while the system is under vacuum. In this article, the authors first review fundamentals of safe O-ring seal construction that the reader will find useful when designing or inspecting viewports meant for vacuum systems. We then discuss an especially constructed adapter flange that allows the safe sealing of a 20 cm diameter glass viewport to an aluminum O-ring flange that was originally designed for a typical metal flange-to-metal flange seal. Factors affecting the strength of glass are discussed, and calculations for maximum deflection under load and safe glass window thickness are presented.

Canceling evanescent waves in high-energy superconducting rf linacs

Many future projects plan using high-current, high-energy, multipass energy-recovery linacs that are based on superconducting rf (SRF) cavities. The necessity of ensuring the transverse stability of the beam in such accelerators imposes strict limits on the high order modes (HOMs) impedances, and demands effective HOM damping. The latter requirement often precludes achieving a high real-estate accelerating gradient in such structures. The modular structure of long SRF linacs also requires incorporating vacuum flanges; however, these flanges have surface contacts and cannot tolerate strong rf fields. Locating them in the low-field areas of the linac structure may involve considerably elongating the intermodular interfaces, a change that would reduce the linac’s real-estate accelerating gradient. In this paper, I propose a novel method to resolve this issue, using compact interconnects between the SRF cavities wherein to locate effective HOM dampers and vacuum flanges.

Development of copper-alloy Matsumoto–Ohtsuka-type vacuum flanges and its application to accelerator beam pipes

The possibility of employing copper-alloy Matsumoto–Ohtsuka-type flanges in a vacuum beam pipes with complicated apertures for a particle accelerator is experimentally studied. Copper-alloy flanges can mitigate the heating problems arising as a result of high-intensity beams more efficiently than stainless-steel flanges. Baking of beam pipes up to a temperature of 200 °C was acceptable with copper-alloy flanges. Moreover, direct electron-beam welding to a copper beam pipe became available, which made the manufacturing easy. In this study, several beam pipes with copper-alloy flanges were installed in the KEKB B-factory positron ring, and the performance was investigated using the high-intensity beams.

真空用フランジおよび配管継手類に関する国際・国内規格の概要と相関

To keep flexibility on construction of vacuum system, understanding of standardization scheme for demountable sealing system consisting of flanges and metal gasket or elastomer O-ring is highly beneficial for both suppliers and users of vacuum equipments. Here we present main contents of international and national standards of flange sealing systems and their correlation, along with some commentaries on states of conformity with standards of commercially available vacuum flanges. Outlines of standards of vacuum fittings, and recent activities for revision and establishment of standards are also reported.

Construction and assembly of the neutron radiography and tomography facility ANTARES at FRM II

In 2003, the components for the neutron radiography and tomography facility ANTARES were constructed and assembled at the beam line SR4B in the northeast corner of the experimental hall at FRM II (J. Radiat. Isotopes (2002), accepted for publication). ANTARES consists of an external beam shutter, flight tube, radiation shielding and measurement blockhouse. The shielding elements are constructed as steel casings filled with heavy concrete. Many harsh constrains in space, accessibility and other conditions (such as a very limited area accessible by the hall crane and restricted space due to surrounding instruments) made it necessary to develop special technical solutions for every step of the construction of the facility. From filling up shielding elements with heavy concrete in winter conditions (temperature below 0 °C) to the development of an hydraulics driven external shutter and collimator positioning system, new convex-shaped nearly one meter diameter vacuum flanges and windows, the development of a movable 30-ton wall on rails as blockhouse door, upto the assembly and exact positioning of heavy components (upto 50 tons) using air cushions, ball casters and a special small truck-mounted telescopic crane.

Summary of quick disconnect vacuum flanges

In accelerator environments, especially proton machines, high background radiation necessitates the need for quick disconnect vacuum flanges. The use of quick disconnect vacuum flanges significantly reduces the dose of radiation received by workers when installing or removing vacuum chambers in the accelerator. Over the course of many years there have been many designs used for these flanges at Brookhaven National Laboratory for such machines as the Alternating Gradient Synchrotron (AGS), the AGS Booster, and the Relativistic Heavy Ion Collider. Several different flanges with apertures as large as 14 in. in diameter were also evaluated for use in the Spallation Neutron Source project. A summary of various quick connect flanges as well as some commercially available flanges and the evaluation results are presented.

Internally shielded beam transport and support system (abstract)

Due to environmental concerns, the Advanced Photon Source has a policy that disallows any exposed lead within the facility. This creates a real problem for the beam transport system, not so much for the pipe but for the flexible coupling (bellows) sections. A complete internally shielded x-ray transport system, consisting of long transport lines joined by flexible coupling sections, has been designed for CARS sector 14 to operate either at high vacuum or as a helium flight tube. It can effectively shield against air scattering of wiggler or undulator white beam with proper placement of apertures, collimators, and masks for direct beam control. The system makes use of male- and female-style fittings that create a labyrinth allowing for continuous shielding through the flexible coupling sections. These parts are precision machined from a ternary hypereutectic lead alloy (cast under 15 inches of head pressure to assure a pinhole-free casting) then pressed into either end (rotatable vacuum flanges) of the bellows assembly. The transport pipe itself consists of a four part construction using a stepped transition ring (Z-ring) to connect an inner tube to the vacuum flange and also to a protective and supportive outer tube. The inner tube is wrapped with 1/16″ pure lead sheet to a predetermined thickness following the shape of the stepped transition ring for continuous shielding. This design has been prototyped and radiation tested.

High sensitivity He desorption leak detection method

A new high sensitivity leak detection method has been developed for the superconducting radio-frequency (SRF) acceleration cavities for the CEBAF linacs. The vacuum integrity of the SRF cavity pairs and the associated indium-sealed vacuum flanges is essential for the successful operation of the accelerator. These SRF cavity pairs are immersed in superfluid helium to minimize rf heat load to the cryogenic system. Conventional leak detection techniques are not appropriate to leak check these cavity pairs at superfluid helium temperature (2 K), since He will be adsorbed onto the cavity surfaces. Further, the sensitivity of the conventional leak detectors is limited to 10−11 atm cm3 s−1 at 293 K. In this article, the details of the He desorption leak detection procedure and the results with production cavity pairs are presented.

The straight vacuum chambers of the SRRC 1.3 GeV electron storage ring

The straight vacuum chambers (S-chamber) of the SRRC 1.3 GeV electron storage ring are designed, fabricated and tested. Vacuum pipes, bellows, flanges, pumping ports and most of the other components are made of aluminum. The S-chambers are designed to have the function of reducing radio-frequency ( rf) impedance and removing the heat created by synchrotron radiation. A stringent tungsten-inert gas (TIG) welding process is performed to minimize the deformations in both longitudinal and transverse directions. In order to achieve uhv, in situ bakeout by tape heaters is adopted. The testing results showed that the designs for removing the baking-related problems work well.

Identifying type 304 stainless steel flange defects using scanning Auger microscopy (SAM)

AbstractAn unusual number of large stringer defects were found in cross‐forged type 304 austenitic stainless steel ultrahigh vacuum (UHV) flanges. These defects are cosmetically displeasing, they can affect the material's machinability and they can also affect the vacuum integrity of a UHV system. In this study, scanning Auger microscopy was used to identify accurately the defects as ferritic inclusions. This information was used to justify a change in forging and heat‐treating procedures, resulting in the reduction of large ferrite segregants and creating a more homogeneous microstructure. Subsequently, the rejection rate was reduced more than 50‐fold.

JET Remote Maintenance during Active Operation

As Joint European Torus (JET) is used more and more with deuterium and tritium plasmas, the machine will be irradiated by high-energy neutrons to a level that prohibits approach by human beings. All modifications and maintenance will then be carried out by remotely controlled equipment and no further attempt will be made to do hands-on work either directly or through local shielding.The remote handling equipment will comprise a series of special transporters carrying end-effectors and tools. One important transporter is a large articulated boom (arm) with nine axes of motion capable of carrying 1 tonne into the tokamak vacuum vessel and positioning it within a few millimetres. Another is the high-precision 150-tonne crane used during JET construction. These and other transporters will give access to all parts of the machine.The various end-effectors are special motorized attachments to the transporters, enabling them to carry and manipulate heavy components. An important end-effector is the (Mascot-type) force-feedback servomanipulator by which very dexterous operations can be performed and special tools placed and held in position. Most identified remote handling tasks require the combination of dexterity and load carrying provided by the manipulators in conjunction with the transporters.A range of tools, many specially designed because of space and access restrictions and the need for meticulous cleanliness, will include cutting and welding tools, largely automatic and in some cases self-propelling. Many design features have been used on JET to make remote handling possible or easier. For example, ultra-high vacuum-welded joints are made between 2-mm-thick Inconel lips, and bolted vacuum flanges have been specially developed.Remote operations will be viewed through a system of closed circuit television, some cameras being stationary and others carried on transporters. All operations will be controlled from a special central control room. A NORD 100 computer (one of JET’s main array) will interconnect the control circuits between equipment and consoles and between cameras and displays. Eventually, it will also provide high-level control input to enhance operator control.Some of the remote handling equipment has been used successfully in support of hands-on work and much more will have been used and proven by the end of 1986 when the tokamak is shut down. Full remote handling will become necessary during 1990.