In the last 20 years, 2-stage cryocoolers have been found to provide an optimum solution for a wide range of applications like low temperature physics, superconducting cold electronics, cryopumping and superconducting magnets. For a proper design of helium cryostats with significant cold masses connected to the first and second stages of cryocoolers, it is important to have a load map (also called "working field") in order to estimate cool-down and warm-up time periods. Such load maps are either not presented in the open literature sources for "high" temperature ranges, or just given by manufacturing companies for general information but without any guarantee. In the present paper, the load map of a 2-stage Sumitomo 415DP cryocooler in the wide temperature range of 40-400 K is presented.
The Vuilleumier (VM)-type pulse tube cryocooler is a novel kind of cryocooler used to obtain liquid helium temperature, which has been experimentally verified. However, the overall efficiency is not satisfying. Based on previous work on a low pressure ratio system, numerical investigations that explore the effect of high pressure ratios on cooling performance are presented in this paper. The research system is cryogen-free in which a Stirling type pulse tube cryocooler is used to provide the required cooling power for the thermal compressor and makes it adjustable for pre-cooling temperature to achieve optimum efficiency. First, after increasing the displacer swept volume to increase the pressure ratio, the dimensions of the main components were optimized with the lowest no-load temperature as the optimization target. Then the dependence of system performance on average pressure, displacer swept volume, frequency and cold HX temperature were studied considering the heat transfer temperature difference of the thermal bridge. Compared with the previous low efficiency under low pressure ratio, when the heat transfer temperature difference of the thermal bridge is 0 K, a higher relative Carrot efficiency of 1.29% and a cooling power of 250 mW at 4.2 K were predicted with an average pressure of 3 MPa, a frequency of 3 Hz and a pressure ratio of 1.67. Further optimization is underway.
Baby-IAXO is a new helioscope, a demonstration version of the proposed full-size IAXO, the International Axions Observatory. It is currently under design and once installed it will search via the Primakoff effect for axions or axion-like particles (ALPs) originating in the Sun. Axions can transform into photons in the presence of a significant magnetic field, and then be detected. The superconducting magnet for Baby-IAXO comprises two 10 m long racetrack coils, spaced by 0.8 m, operated in a quadrupole configuration and generating an average magnetic field of 2.1 T in the two 700 mm diameter free bores for axion-to-photons decay positioned in between the coils. Cool down and operational cryogenic requirements are handled by a combination of single and double stage cryocoolers. For the cool down of the 18.5 t cold mass within 22 days and for current leads cooling, the use of powerful single stage cryocoolers is of paramount importance. The cooling power is distributed across the cold mass and thermal shield using helium gas flow enforced by cryocirculators. The design of the 10 kA conduction cooled current leads is presented as well, since at 70 K these represent the dominant heat load. The cryogenic system allows for a constant heat load of 1.2 kW at the first stage and 8.5 W at the 4.2 K cold mass. Alternatively, the magnet may be operated in persistent mode, thereby reducing the heat load and the number of cryocoolers. It requires a more complex cooling circuit, implementation of a 10 kA persistent mode switch, and a delicate balance of energizing and operational heat loads.
The new Cryogenic Flux Capacitor (CFC) technology employs nano-porous aerogel composites to store large quantities of fluid molecules in a physisorbed solid-state condition at moderate pressures and cryogenic temperatures. By its design architecture, a CFC device can be "charged" and "discharged" quickly and on demand according to standby/usage requirements. One of three main application areas is the CFC-Life for breathing air or oxygen supply to meet new demands in life support systems. Through the Liquid Oxygen Storage Module (LOXSM) Project, the National Institute for Occupational Safety and Health, and Cryogenics Test Laboratory have partnered to test the feasibility of applying the CFC technology to Closed-Circuit Escape Respirators (CCER), or respirators operating on the closed-circuit principle in general. The envisioned Cryogenic Oxygen Storage Module (COSM) is an innovative concept to store oxygen in solid-state form, according to physisorption processes at any cryogenic temperature, and deliver it as a gas using the CFC as the core storage element. Gaseous oxygen would be admitted into the breathing loop of the CCER by introducing heat into the storage module. Potentially replacing the gaseous or chemical based oxygen supply used in today's closed-circuit respirators, the COSM is a high capacity, conformal, small-size solution for future life support equipment of all kinds. In particular, are the CCER devices that must to be carried on the person, ready to be quickly deployed and used for escape in an emergency. Initial test data for physisorption of oxygen in aerogel materials and CFC core modules are presented. The basic operational parameters for charging and discharging are summarized through prototype testing of the cryogenic oxygen storage module.
With end of year 2018 the LHC has completed its second physics run and started its second two-years long shut down period dedicated to planned consolidation, maintenance and upgrade activities. The run2 - four-year physics operation period started in spring 2015 - was used mainly for luminosity production but also to allow the optimization and adaptability of the cryogenic system capacity to compensate for generated operational heat loads. Several tests and qualifications were studied and applied to the configuration of the available equipment in order to reach a deep understanding of the real operation limits. Dedicated global improvements were implemented in the control system, especially in regards of handling the beam induced dynamic heat load during transitory operational states. Adequate modifications were also applied for the Inner Triplet magnets control system to compensate for dynamic heat load related to secondaries, close to the interaction points of the ATLAS and CMS detectors. This paper will give a general overview of the LHC cryogenics operation with specific information on encountered operational difficulties and applied solutions on the system. Helium inventory management, including process use and leaks, as well as the system overall availability indicators will be presented.
Dewars are used to store and transport cryogens like LNG, LN2, LOX, LHe etc. These comprise two vessels, one placed inside the other and held together either at the "neck" (input/output port) or by support systems, depending on the capacity, the mechanical loads on the vessel and the boil-off characteristic of the stored cryogen. Support system based dewars are more common for real-life and industrial applications. Design of the support system are based on the principles that are used for high temperature pressure vessels. On the other hand, support system to be used for cryogenic fluid storage should also address the heat inleak through the supports along with the imposed mechanical load and thermal contraction-expansion effects. Some safety factors are prescribed in the literature to address these concerns; however, the scientific basis of design strategies available in the open literature so as to give a more scientific basis of design is absent. This would result in reduction in use of excessive dimensions or material thereby reducing the payload and the capital cost. Considerations of mechanical load and thermal heat inleak often lead to diametric conclusions in terms of the diameter/thickness of the support system, leading to paretooptimal solution. Topology optimization (TO) is often used to design structures like bridges, vehicles, robotic arms etc. by a systematic and sequential removal of the mass of the material being used to fabricate the given structure while meeting the constraints in terms of load bearing capacity of the structure and heat inleak. This methodology may be followed to arrive at an optimized geometry for the support system when the designer is unsure of the initial shape to start working. In this work, TO has been tested with various thermal and mechanical boundary conditions to arrive at optimized support geometry.
A high Technology Readiness Level cryocooler with significant cooling in the 2K to 4K regime will enable a variety of missions ranging from large infrared space telescopes to superconducting and quantum applications. The cryocooler for the MIRI instrument on JWST was designed for operation at 6K, and with relatively minor changes this design can achieve significant lift in the 2K to 4K region. This paper provides curves of predicted lift vs. power for a variety of operating temperatures, based on the model anchored by tests of the MIRI cooler. The modifications are described, and their mass impacts are estimated. These mass and performance estimates enable payload and mission planners to explore new mission classes.
The HL-LHC Project currently undertaken by CERN that provides an upgrade to the existing LHC accelerator, is designed to increase the luminosity of the colliding particle bunches by a factor of at least five. Part of this upgrade will require the replacement of the existing groups of three superconducting LHC triplet magnets situated on each side of the ATLAS and CMS detectors with similar groups of four higher field HL-LHC triplet magnets of a new design that exploit coils manufactured with cables in Nb3Sn superconducting alloy. The HL-LHC triplet magnets require dedicated electric current feeders linking their cold masses to their cryostat vacuum vessels, thermo-electrically optimised and specifically designed to separately feed their quench protection, beam tuning and instrumentation systems with electric current. The HL-LHC instrumentation feedthrough system is similar, though containing a larger cable inventory, to that mounted on existing cryo-magnets in the LHC accelerator whereas the quench protection and beam tuning systems, both present new requirements calling for a substantially different design approach. Installed in a highly activated zone of the LHC, all three systems consequently exploit only natural heat convection to prevent the formation of condensation at their warm ends. This paper describes the functional design and thermo-electrical optimisation achieved for each of these electric current feeder systems.
A cryogenic expander for hydrogen liquefier with active magnetic bearings (AMB) has been designed and will be made and tested. The shaft design and strength review are significant factors for the turbine since it affects the performance and safety of the expander significantly. In order to produce lower temperature hydrogen, the liquefier needs a very small and high-speed turbo-expander. However, there are few studies on expander with both active magnetic bearings and eddy current brakes. In this study, the speed of the turbine is up to 100000 rpm. Its cooling power is about 4kW. The inlet pressure is 1MPa, and the outlet pressure is 0.7MPa.Under this condition, the turbine is designed, and the simulation is done. An eddy current brake which can govern the rotational speed quickly is designed and studied as well.
Absolut System has built a 30 K and a 10 K remote Helium cooling loops used as a vibration free cooling source, respectively for IR detectors electro-optical characterization test bench and two-stage optical cryostat. The circulation loops are based on a by-passed flowrate from either a two-stage Gifford–McMahon cryocooler or a two-stage Pulse Tube cryocooler. Dedicated compact and high efficiency tubes & shell heat exchangers have been designed and produced for the recuperators. The paper describes the design and the performances of the vibration free cooling system produced. The current work towards a 4 K low vibration cooling source will be introduced as well.
Fermi National Accelerator Laboratory (FNAL) is developing the international Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) to advance neutrino science. The flagship of the DUNE project consists of a large particle detector constructed one-mile (1.6 km) beneath the surface at the Sanford Underground Research Facility (SURF) in Lead, SD. The SURF detector is the largest of its type ever built and is comprised of four cryostats totaling 70,000 tons of liquid argon (LAr) to record neutrino interactions with unprecedented precision. Each cryostat houses a detector, the first includes 150 Anode Panel Assemblies (APA) submersed within 17,500 tons of LAr. Before installing 150 APA within the SURF detector they will be cryogenically cooled to nominally 90 K at the APA Test Facility (APATF) utilizing nitrogen flows. The APATF cryogenic system is entirely located one-mile underground at the SURF facility and includes nominally 13 kW of refrigeration at 80 K, cryogenic transfer lines, APA test cryostats, a cryogenic control system, and various control and pressure safety elements to ensure performance and safety requirements are achieved. The APATF preliminary design is in progress and major considerations include an efficient, cost-effective mechanism to deliver the required refrigeration to the APATF underground, support of rigid testing intervals to support the DUNE operating schedule, temperature stability of the APA and electronics within cryostats, efficient cryogenic system operation to minimize heat leak and/or liquid nitrogen consumption, thermo-mechanical stability and flexibility of components, and pressure safety of the APATF cryogenic system. Installation and integration of the APATF cryogenic system within the footprint and to adjacent sub-systems is also discussed.
The European Spallation Source (ESS) is a neutron-scattering facility being built with extensive international collaboration in Lund, Sweden. Three cryogenic plants with a vast cryogenic distribution system meet the cooling requirements of the superconducting RF cavities in the accelerator (ACCP), the cold hydrogen moderators in the target (TMCP), a cryomodule test stand and the sample environments for neutron instruments (TICP). The first of the three plants, the TICP has been successfully installed, commissioned and acceptance tested in 2018 by Air Liquide Advanced Technologies. Meanwhile the other two cryoplants (ACCP and TMCP) are under commissioning and testing by Linde Kryotechnik AG. The cryoplants share common helium buffer tanks, safety relief headers and helium recovery system due to historical, economical and architectural reasons. The helium recovery strategy and system configuration will be described in the paper. Resulting challenges, risks and safety relevant events that happened during, especially parallel, commissioning activities will be presented. The measures implemented to mitigate major risk and lessons learned are addressed as well.
The Advanced Photon Source (APS) is in the midst of a major facility upgrade including both a new electron storage ring (SR) and many new insertion devices (IDs) providing x-ray photon beams to a new suite of experimental end stations. Included among the new IDs are four 4.8-meter superconducting undulator (SCU) cryostats, each containing two 1.8-meter planar undulator magnets operating at 4.2 K in either a phase shifted or canted configuration. We describe a new, compact cryocooler-based cryostat design which supports the magnets and associated subsystems and also fits the space constraints of the SR ID straight sections. The design is an evolution of earlier single-magnet 2-meter cryostats, retaining some subsystem commonality while incorporating lessons learned and several features unique to the challenge of supporting two independently operable undulator magnets in a single device.
Future astrophysics missions such as SPICA, Athena or LiteBird will need a cooling below 1 K (until 50 mK) to achieve the detectors' required sensibility. To address such requirements, cooling chains are built coupling several technologies using intermediate temperature cooling, explaining why a high cooling power at 15 K is essential. The CEA-DSBT designed, for lab test purpose, a Pulse Tube cooler system consisting of a heat intercepted single-stage cold finger which is pre-cooled by a Gifford McMahon cryocooler. The cold part of the PT, in particular the regenerator, is critical to the PT cooler performance. Keeping the regenerator material standard (stainless steel mesh), we study here the influence of the cold regenerator mesh geometry on the operation of the cold finger. The wire thickness is varied, which modifies the porosity, the dead volume and the heat surface exchange of the regenerator. Experimental results on different mesh designs are presented here and analysed, showing a significant influence of the mesh geometry on the performance.
Vuilleumier cycle was first patented in 1918. It was usually regard as the thermal-driven Stirling refrigeration cycle, which combined the low-frequency working pattern like Giffod-Mcmahon (GM) cryocooler and the compactness of Stirling-type cryocooler. With the continuous development in the past 100 years, the Vuilleumier-type (VM-type) cryocoolers have to been proved to generate cooling power from ambient temperature to liquid nitrogen temperature and even to liquid helium temperature. In recent decades, some efforts were made on traditional displacer-type VM cryocooler, Vuilleumier hybrid pulse tube cryocooler (VM-HPTC) and the VM-type pulse tube cryocooler (VM-type PTC) to obtain the liquid helium temperature. Successfully, not only the 4 K was obtained, but also the limit temperature of oscillating cryocooler by He4 was hit. This paper presents the progress of the 4 K-class VM-type cryocooler and analyzed the possible applications of 4 K class VM-type cryocooler.
Electrical insulation at cryogenic temperatures is a key technology in the development of superconducting cables and superconducting current limiters. Due to their improved electrical, mechanical and thermal properties, the application of epoxy nanocomposites in high voltage power systems has shown a broad outlook. In this paper, tests were conducted to investigate the electrical tree aging phenomenon in epoxy resin/Al 2 O 3 nanocomposites in liquid nitrogen under AC voltages. The test samples were prepared with six levels of nanofiller content: 0 wt %, 1 wt %, 2 wt %, 3 wt %, 4 wt %, and 5 wt % by weight ratio. Experimental results showed that nano-fillers below 3% are easy to cause the electric field distortion at the needle tip, which reduces the tree inception voltage in the composite sample compared to that in the neat epoxy sample. At low temperature, the effect of electric field distortion on the tree inception voltage is significantly weakened and the tree growth rate decreases sharply with the increase of the content of the nano-filler.
Frequency Loss Induced Quench (FLIQ) system is a novel technique that relies on generating AC losses to uniformly heat a superconducting coil to induce a safe and rapid quench. FLIQ drives an imbalance in the transport current between two or more sections of the magnet. To drive the imbalance, FLIQ uses an H-bridge design with Insulated Gate Bipolar Transistor (IGBT)s, whose gates are controlled based on the current feedback, allowing the system to operate at resonance. Simulation of estimated energy per volume deposited by FLIQ and sensitivity analysis of its parameters are performed and the results presented. Application of FLIQ for protection of high temperature superconducting (HTS) magnet systems is described.
The cryogenic system at the Facility for Rare Isotope Beams (FRIB) supports loads for 2 K refrigeration, 4.5 K refrigeration and liquefaction, and a 35-55 K thermal shield for the linear accelerator consisting of 46 cryomodules, 4 superconducting dipoles and 14 superconducting magnets for the experimental system. The controls system for cryogenics was designed, installed, and commissioned with the goal of high availability, ease of maintenance, and simplicity of operation. The personnel protection system (PPS) is a separate system which monitors for oxygen deficiency hazards (ODH) throughout the cryo-plant and around the cryogenic loads. The system consists of Allen-Bradley programmable logic controllers (PLCs) with local human machine interfaces (HMIs) along with the Experimental Physics and Industrial Controls System (EPICS) for normal operations and data acquisition. Two separate networks are utilized in the cryogenic facility. One is a network cluster that houses EPICS. It is designed with high redundancy and is completely separate from the network used for the rest of the particle accelerator. The second network only includes PLCs and HMIs for faster data transfer between PLCs, increased flexibility for changing operating conditions, and complete system operation in the case of an EPICS network failure. This paper reports on the design choices selected and experiences in integrating and commissioning the FRIB cryogenic control system.
Sorption compressors do not have moving parts and are suitable for driving Joule-Thomson cryocoolers. This allows a complete cryogenic cooling system with the absence of moving parts, which is attractive especially for space applications, as well as for other applications. Sorption compressors are thermally driven, meaning, they operate in heating and cooling cycles. The main drawback of sorption compressors is their low efficiency, relative to mechanical compressors. The compressor efficiency is defined as the PV power divided by the heat which is supplied to the compressor, it is limited by the Carnot efficiency, and practically it is significantly lower. In addition, we define a thermal efficiency of a compressor, by the heat which is transferred to the adsorbent divided by the total heat which is supplied to the compressor. In the frame of our ongoing research on sorption applications we develop a numerical model for the heat and mass transfer in a sorption cell. The model allows investigating the performance of a variety of sorption cell configurations, including different geometries, dimensions, and materials. In the current paper we show preliminary results of sorption compressor efficiencies for different sorption cell designs. An investigation on the heater configuration, general dimensions, and different adsorbents is presented. The results show that a sorption cell configuration, which provides a maximum compressor efficiency, is not necessarily the cell configuration which provides the maximum thermal efficiency
The present paper illustrates a case study in the progress of ongoing research work to develope a 100 litre Helium cryostat with in-situ recondensing facility. The cryostat with a cryocooler sock comprises 46 components assembled in an optimal sequence. Cryostat development involved thermal load estimation, mechanical design, fabrication of components and sub-assemblies. The cryostat deploys a two stage Gifford McMahon cryocooler with appropriate cooling capacities available on 1st and 2ndstage.The thermal load due to the cryostat assembly is estimated as 34 W and 300 mW for 1st and 2ndstage of the cryocooler respectively. Experimental trials are conducted for testing of the cryostat with recondensing cryocooler. The first no load trial in vacuum produced unsatisfactory results. Appropriate modifications are carried out in the assembly which resulted in no load temperatures of 51.95 K on 1ststage and 3.43 K on 2ndstage. At a heater load of 0.448 W, the 2ndstage stabilized at 4.21 K while 1ststage temperature stabilized at 52.47 K without any heater load on 1ststage. Temperature increased from 51.95 K to 52.47 K for 1ststage showing 0.448 W cooling capacity available at 2ndstage for recondensation at 1 bar pressure. The paper highlights these modifications towards successful development of the Helium recondensing cryostat.
