Gifford-McMahon Cryocooler Research Articles

Attenuation of Gifford-McMahon cryocooler induced vibration using mechanical vibration isolators

Aiming to attenuate the vibration that is induced by a Gifford-McMahon (G-M) cryocooler, a method attenuating the vibration with mechanical vibration isolators (MVIs) is proposed. A scheme supporting the G-M cryocooler with one kind of supporting system that mainly comprises the MVIs is presented. The vibration response of the supporting system caused by the vibration of the G-M cryocooler are studied, and the effects of the structural parameters of the MVIs are investigated. The results show that reciprocating moving modes of the MVIs induce the modal characteristics of the supporting system, which further formed the vibration response of the supporting system under the excitation of the G-M cryocooler vibration. Structural parameters of stiffness and installation sites of the MVIs affect the reciprocating moving mode of the MVIs, through which the modal characteristics and the vibration response of the supporting system are affected. Through optimizing the installation sites of the MVIs, the vibration response of the supporting system is attenuated. It demonstrates that the method proposed in this paper is available for attenuating the cryocooler-induced vibration in the field of cryogenics and refrigeration.

Long term operation of the superconducting triplet quadrupoles with cryocoolers

Superconducting triplet quadrupoles (STQs) with cryocoolers characterize the BigRIPS in-flight separator and radioactive isotope (RI) beam delivery lines in the RIKEN RIBF (Radioactive Isotope Beam Factory) project. The STQ magnet is a large-aperture superferric quadrupole triplet cooled by liquid helium bath cooling method in a single cryostat. The STQ cryostat is designed to be operated continuously with a Gifford-McMahon (GM)/Joule-Thomson (JT) cryocooler and a GM cryocooler. We operate 22 STQ systems for more than twelve years without warm-up the magnets. We report operational experiences, such as degradation of cooling capacity and failures of compressors, in the long-term operation of the STQ systems. Replacement of ageing cryocooler unit is discussed to improve the cooling capacity.

Multi-metallic conduction cooled superconducting radio-frequency cavity with high thermal stability

Superconducting radio-frequency cavities are commonly used in modern particle accelerators for applied and fundamental research. Such cavities are typically made of high-purity, bulk Nb and with cooling by a liquid helium bath at a temperature of ∼2 K. The size, cost and complexity of operating a particle accelerator with a liquid helium refrigerator make the current cavity technology not favorable for use in industrial-type accelerators. We have developed a multi-metallic 1.495 GHz elliptical cavity conductively cooled by a cryocooler. The cavity has a ∼2 µm thick layer of Nb3Sn on the inner surface, exposed to the rf field, deposited on a ∼3 mm thick bulk Nb shell and a bulk Cu shell, of thickness mm deposited on the outer surface by electroplating. A bolt-on Cu plate 1.27 cm thick was used to thermally connect the cavity equator to the second stage of a Gifford-McMahon cryocooler with a nominal capacity of 2 W at 4.2 K. The cavity was tested initially in liquid helium at 4.3 K and reached a peak surface magnetic field of ∼36 mT with a quality factor of 2 × 109. The cavity cooled by the cryocooler achieved a peak surface magnetic field of ∼29 mT, equivalent to an accelerating gradient of 6.5 MV m–1. The conduction-cooled cavity could be operated in continuous-wave with as high as 5 W dissipation in the cavity for 1 h without any thermal breakdown, because of the Cu outer layer with high thermal conductivity. This result represents a paradigm shift in the technology of superconducting accelerator cavities.

Heat-Transfer Characteristics of a Cryogenic Loop Heat Pipe for Space Applications

Infrared detectors on satellites and spacecraft require cooling to increase their measurement sensitivity. To efficiently cool infrared detectors in a zero gravity environment and in limited spaces, a cryogenic loop heat pipe (CLHP) can be used to transfer heat over a certain distance by the capillary forces generated from porous wicks without a mechanical power source. The CLHP presented in this study transfers the heat load to a condenser 0.5 m away from an evaporator at temperatures below −150 °C. The CLHP with two evaporators includes a subloop for initial start-up, and uses a pressure reduction reservoir (PRR) for the supercritical start-up from room to cryogenic temperature. Nitrogen is used as the working fluid to verify the thermal behavior of the CLHP, and the heat-transfer capacity according to the nitrogen charging pressure of the PRR is investigated. To simulate a cryogenic environment, the CLHP is installed inside a space environment simulator, including a single-stage GM (Gifford McMahon) cryocooler to cool the condenser. The CLHP is horizontally installed to simulate zero gravity. The heat-transfer characteristics are experimentally evaluated through the loop circulation of the CLHP.

Numerical Thermal Analysis and 2-D CFD Evaluation Model for An Ideal Cryogenic Regenerator.

Regenerative cryocoolers such as Stirling, Gifford–McMahon, and pulse tube cryocoolers possess great merits such as small size, low cost, high reliability, and good cooling capacity. These merits led them to meet many IR and superconducting based application requirements. The regenerator is a vital element in these closed-cycle cryocoolers, but the overall performance depends strongly on the effectiveness of the regenerator. This paper presents a one-dimensional numerical analysis for the idealized thermal equations of the matrix and the working gas inside the regenerator. The algorithm predicts the temperature profiles for the gas during the heating and cooling periods, along with the matrix nodal temperatures. It examines the effect of the regenerator’s length and diameter, the matrix’s geometric parameters, the number of heat transfer units, and the volumetric flow rate, on the performance of an ideal regenerator. This paper proposes a 2D axisymmetric CFD model to evaluate the ideal regenerator model and to validate its findings.

Design and Evaluation of Prototype High-Tc Superconducting Linear Synchronous Motor for High-Speed Transportation

We developed a prototype of a high-Tc superconducting (HTS) linear synchronous motor (LSM) and evaluated its operational performances to obtain the preliminary design data for a test vehicle having a speed of 518.4 km/h. The HTS electromagnet was fabricated using a non-insulated (NI) GdBCO HTS coil, which was designed to produce a magnetomotive force of 300 kA-turns at a cooling temperature of 20 K. A two-stage Gifford-McMahon cryocooler was used to cool the electromagnet. The prototype was tested up to 2.7 kN sufficient to the required thrust of the test vehicle. The thrust characteristics shown by changing the operating conditions were also consistent with the simulation results. The HTS electromagnet was successfully operated during the test, and there was no fault in the NI HTS coils. Finally, we confirmed the design feasibility of HTS LSM for a test vehicle.

Quench Phenomena in a Conduction-Cooled Fast-Ramping High Temperature Superconducting Magnet

A conduction-cooled HTS magnet was tested to produce an AC magnetic field up to 4 T for an adiabatic demagnetization refrigerator (ADR). Quench detection was conducted by measuring the voltages in the conductor, and the protection system was constructed with an external dump resistor. The magnet, which is equipped with extensive copper thermal drains, was conduction-cooled by a two-stage Gifford-McMahon cryocooler to approximately 6 K. The magnet succeeded to stably generate an alternating magnetic field between 0 and 3.5 T at a ramp rate of 229 mT/s without any pre-quench signs; however, in the case of a maximum 4 T experiment, a quench occurred, and the magnet was permanently damaged. The quench location was identified as the place where the highest perpendicular field from the magnet was generated. It is speculated that the already-formed normal zone before quench grows very fast during the dump process, and part of the magnetic energy is dissipated in this normal zone, causing the excessive temperature rise of the conductor. The detailed experimental results are presented and discussed.

Drive force optimization of a pneumatically-driven Gifford-McMahon cryocooler by numerical modeling

Pneumatically-driven displacer mechanisms are widely used in Gifford-McMahon (G-M) cryocoolers. Particularly for large size G-M cryocoolers, this type of drive is preferable compared to the scotch yoke-type, as only a small motor is required for driving the rotary valve and, therefore, the entire cryocooler can be very compact. Though various numerical models of G-M cryocoolers have been presented in the past, modeling of the pneumatically-driven type and optimization of the driving force have rarely been done. This work presents a one-dimensional numerical model of a pneumatically-driven single stage G-M cryocooler running at 80 K and related studies. The transient model predicts the movement of the displacer and simulates the cryocooler performance simultaneously. An optimization of the drive force is implemented for the defined cryocooler operating at various speeds. It discovers that the driving force reshapes the P-V diagram effectively and has to be well designed according to the frequency to maximize the cooling capacity per mass flow rate.

30 K to 2 K vibration free remote cooling systems

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.

Recent Advances in Gifford-McMahon Cryocoolers

Cryocoolers are devices which produce the required refrigeration at a specific low temperature, and they can replace the normal cryogenic fluids. Cryogenic fluids give refrigeration only at a specific temperature whereas cryocooler can produce refrigeration at varying low temperatures. There are many types of cryocoolers like Pulse tube, Stirling, Joule-Thomson, Gifford-McMahon (GM) etc. Many advances have occurred over the years in these cryocoolers. For obtaining very low temperatures along with large cooling powers GM and Pulse tube cryocoolers are found to be better among the others. Hence, this article focuses the advances in GM cryocoolers. This article discusses the working of GM cryocooler, importance of regenerator material and how one can use special regenerator materials to reach very low temperatures. Further, the advances in these cryocoolers such as the use of Labyrinth finish regenerators to obtain higher cooling powers etc. are also discussed. It is presumed that the reader obtains a basic understanding of the GM cryocooler, latest developments and the possible future areas for research from this article.

Excitation Test of Superconducting Magnet in 230-MeV Isochronous Cyclotron for Proton Therapy

We develop a superconducting isochronous cyclotron for proton therapy with a yoke weight of approximately 65 tons, which is less than one-third of the Sumitomo's normal-conducting 230 MeV cyclotron. Two NbTi superconducting coils with an axial gap are conduction-cooled by four 4 K Gifford-McMahon cryocoolers. The average field designed is 3.9 T at the extraction radius. Since superconducting magnets for treatment devices are required to have sufficient margin for critical temperature and to recover early from quenching, they were evaluated through excitation and quench tests. We achieved the maximum magnetic field generation without quenching, and measured the actual current dependence of inductance, which is in agreement with the computational results. A forced quench test was performed to test the protection circuit. The magnet was successfully protected, and the recovery time of the magnetic field generation was 17 hours.

Thermopneumatic analysis of single stage gifford-mcmahon cryocooler

Thermopneumatic analysis of single stage gifford-mcmahon cryocooler

Design of a Continuous Pellet Fueling System for Wendelstein 7-X

A continuous pellet fueling system (CPFS) is currently being designed at the Oak Ridge National Laboratory (ORNL) for the long pulse operation of the Wendelstein 7-X (W7-X) stellarator. The purpose of the CPFS is to provide deep continuous fueling for feedback-controlled high-density operation and mitigation of predicted hollow density profiles. The system will provide the capability to inject cylindrical pellets of solid hydrogen or deuterium into the plasma core, with flexibility to vary the pellet size, velocity, and injection frequency. Pellets are nominally of 3 mm in diameter and have a length between 1 and 4 mm. The heart of the CPFS is a vertically oriented, twin-screw extruder, cooled by three Gifford-McMahon cryocoolers in parallel, designed to form a continuous filament of hydrogen or deuterium. The filament width, which determines the pellet length, can be adjusted by means of a variable nozzle driven by a linear actuator at the base of the extruder. Coupled to the nozzle is a solenoid-operated gas gun and cutter assembly. A pneumatic propellant valve pulses a burst of ~60 bar helium to accelerate the cut pellet into W7-X. Three gaps in the guide tubes provide pumping locations to remove the helium propellant before it reaches the plasma. The maximum velocity of the pellet is limited by its ability to survive navigating the guide tube trajectory intact. A microwave cavity located within the guide tube provides the capability to measure the pellet size and velocity. The mechanical and thermal designs of the W7-X extruder, adjustable nozzle, and gun and cutter assembly design are described. A guide tube design and experimental pellet survivability test results are presented.

Superconducting Nanowire Single Photon Detector With Efficiency Over 60% for 2-μm-Wavelength

We demonstrate superconducting nanowire single photon detector (SNSPD) for the wavelength at around 2 μm. The linewidth of the NbN nanowire is squeezed to 56 nm to increase the intrinsic response efficiencies at longer wavelengths such as 2 μm. Serially connecting avalanche architecture is applied to increase the signal-to-noise ratio (SNR) of the response signal. Further, the optical cavity is optimized to improve the absorption of the device. A silica single-mode fiber is adopted to introduce photons to the SNSPD at a temperature of 2.25 K using a Gifford–McMahon cryocooler. The SNSPD exhibits detection efficiencies of 58%, 67%, and 63% at wavelengths of 1550, 1700, and 2000 nm, respectively, with dark count rate of ∼12 kcps, which is reduced to 2 cps when the attached fiber pigtail is all placed inside the 40-K cryostat. The detection efficiency at 2000 nm is 2.5 times greater than that of the best previously developed detector with an efficiency of 25%. Our SNSPD is promising for practical applications in molecular science and earth meteorology.

Designing and Basic Experimental Validation of the World's First MW-Class Direct-Drive Superconducting Wind Turbine Generator

High temperature superconducting (HTS) technologies are expected to be a key enabler for lightweight and cost-effective direct-drive (DD) trains for large wind turbines. This paper reports the designing and basic experimental validation of the world's first full-scale DD HTS generator demonstrated on a commercial wind turbine. The HTS generator has its rotor with an HTS field winding working below 30 K, which is achieved by using off-the-shelf Gifford-McMahon cryocoolers. The stator of the generator is essentially conventional, except that the armature winding has four segments to limit fault torques in case of sudden short circuits due to converter failures. Compared to an existing DD permanent magnet generator on the turbine, the air gap shearing stress of the HTS generator is doubled, and the weight is reduced by 24%. The overall design requirements from the turbine integration perspective, as well as the topological considerations, are first described in this paper. The electromagnetic and cryogenic designs are then presented, followed by performance testing of HTS coils. The basic experimental validation shows that the cryogenic design is satisfactory and the measured no-load voltage matches the finite element calculation very well.

Superconducting nanowire single photon detectors operating at temperature from 4 to 7 K.

We experimentally investigate the performance of NbTiN superconducting nanowire single photon detectors above the base temperature of a conventional Gifford-McMahon cryocooler (2.5 K). By tailoring design and thickness (8 - 13 nm) of the detectors, high performance, high operating temperature, single-photon detection from the visible to telecom wavelengths are demonstrated. At 4.3 K, a detection efficiency of 82 % at 785 nm wavelength and a timing jitter of 30 ± 0.3 ps are achieved. In addition, for 1550 nm and similar operating temperature we measured a detection efficiency as high as 64 %. Finally, we show that at temperatures up to 7 K, unity internal efficiency is maintained for the visible spectrum. Our work is particularly important to allow for the large scale implementation of superconducting single photon detectors in combination with heat sources such as free-space optical windows, cryogenic electronics, microwave sources and active optical components for complex quantum optical experiments and bio-imaging.

Demonstration of a Superconducting Nanowire Single-Photon Detector using Adiabatic Quantum-Flux-Parametron Logic in a 0.1-W Gifford-McMahon Cryocooler

Superconducting nanowire single-photon detectors (SSPDs or SNSPDs) have superior performance and are thus used for many applications, such as quantum information and laser communications. Lately, much effort has been spent on the development of multi-pixel SSPD arrays to achieve single-photon-level imaging. SSPD arrays require efficient readout schemes that reduce the number of coaxial cables for reading out the SSPD pixels. In a previous study, we proposed a readout interface using adiabatic quantum-flux-parametron (AQFP) logic, which digitizes the information of an SSPD at cryogenic temperature. In this study, we show the first demonstration of an SSPD that is read out by the AQFP readout interface placed in the same 0.1-W Gifford-McMahon cryocooler. The measurement results show that the AQFP readout interface reads out the SSPD with low error rates. Also, it is found that the temperature of the sample stage does not change even after the AQFP readout interface is turned on, which indicates that the power and current required for the AQFP readout interface are sufficiently low for the implementation using a compact cryocooler.

Study on Superconducting Levitation System for Gravity Measurement

A high precision superconducting levitation system for gravity measurement has been developed, which used the levitation of a superconducting sphere by the magnetic field of two superconducting coils. The magnetic levitation is designed to provide independent adjustment of the levitating force and the force gradient. A Gifford-McMahon (GM) cryocooler is employed to cool down the system. This paper reviews the construction and operating characteristics of the system. The test results show that the earth tide signal was detected by the system.

Single-Flux-Quantum Based Event-Driven Encoder for Large-Pixel Superconducting Nanowire Single-Photon Detector Array

We propose a single-flux-quantum (SFQ) based event-driven encoder for a large-pixel superconducting nanowire single-photon detector (SSPD) array with a row-column readout architecture. The designed SFQ encoder can acquire time-tagged address data with a high time resolution. To apply 32 × 32 pixel SSPD system with a row-column architecture, the SFQ encoder is equipped with two 32-channel input ports among which one is for positive pulses, whereas the other is for negative pulses. The number of Josephson junctions (JJs) in the designed circuit is 2780. The power dissipation and required total bias current are 0.21 mW and 170 mA, respectively, owing to the reductions in critical currents of the JJs and bias resistors. The circuit generates time-tagged address data by applying electrical pulses at room temperature not only in liquid helium but also in a 0.1-W Gifford-McMahon (GM) cryocooler.

Influence of the Properties of Regenerative Heat Exchanger Packing Material on the Efficiency of a Gifford–Mcmahon Cryocooler

The influence of the packing material and porosity in a lower stage of a regenerative heat exchanger on the operating efficiency of a GM cryocooler has been studied. Experiments were used to quantify the decrease in cooling capacity when replacing lead by tin. It is found that reduction in the porosity of the material leads to a decrease in cooling capacity of the cryocooler.