Pulse Tube Cryocooler Research Articles

CFD analysis of an inertance pulse tube refrigerator: exploring the influence of tapered pulse tube and regenerator design

CFD analysis of an inertance pulse tube refrigerator: exploring the influence of tapered pulse tube and regenerator design

Two Stage Pulse Tube Cryocooler with Intermediate Heat Exchanger for accessing Regenerator Cooling Capacity

Conventional operation of closed-cycle two-stage GM-type Pulse Tube Cryocoolers (PTCs) usually relies on utilizing the cooling power of both the 1st and the 2nd stage. While the 1st stage is required to precool the 2nd stage to reach the lowest accessible temperature below 4K, it usually also provides enough cooling power to cool additional cryostat elements such as radiation shieldings. However, current applications in quantum physics have highlighted the need to additionally access heat sinks with intermediate temperatures and cooling powers, e.g. for cooling of superconducting wires. Here we will demonstrate a cooler configuration, where a third cooling stage is incorporated into the 2nd stage regenerator. This third intermediate cooling stage allows to extract 4-5 W of cooling power at temperatures between 8 K and 9 K for a standard two-stage PTC with a cooling capacity of 1.6 W at 4.2 K. Most importantly, this approach does not reduce the performance of the main stage but the added intermediate regenerator stage instead allows to tap into hidden cooling power of the PTC.

Experimental study of a gas-coupled pulse tube cold finger with both active piston and cold inertance tube as phase shifters for 8 K applications

Stirling-type pulse tube cryocoolers (SPTCs) working at temperatures below 8 K represent advantages in very long wave infrared detection, terahertz detection, etc. It is essential for SPTCs to obtain reasonable distribution of impedance to achieve good cooling performance. However, adjusting the distribution of impedance to an optimal value is hard as temperature decreases. It is critical for muti-stage SPTCs working at temperatures below 8 K to arrange appropriate phase shifter at each stage. This paper introduces a gas-coupled pulse tube cold finger with active piston and cold inertance tube as phase shifters for 8 K applications. The cold finger consists of pulse tube 1 (PT1) which works at liquid hydrogen temperatures and pulse tube 2 (PT2) which operates at liquid helium temperatures. Active piston is the phase shifter of PT1. It could adjust the impedance to any value theoretically and make the cold finger highly adaptable. The phase shifter of PT2 is cold inertance tube and gas reservoir. Cold inertance tube and gas reservoir has simple structure which makes it suitable for space applications. The impact of frequency and operating parameters of active piston on no-load temperature is investigated by experiments. A lowest no-load temperature of 5.16 K is achieved in experiments. The effect of temperature distribution of cold finger on cooling capacity at 8 K is also researched. A cooling capacity of 74 mW at 8 K can be obtained with the electric input power of 177.5 W and a pre-cooling capacity of 9.1 W/70 K.

Investigation of heat leakage calculations and experiments for a wide-mouth liquid nitrogen tank

ABSTRACT With the continuous development of biomedicine, the long-term low-temperature storage of biological samples has become essential. In order to meet the demand for long-term storage of liquid nitrogen to keep samples safe, a study on the evaporated gas recycling storage of liquid nitrogen tanks will be carried out. This research utilizes new approach to accurately calculate the heat leakage of the liquid nitrogen tank. The experimental results show that the theoretical heat leakage is 6.16 W, and the actual heat leakage is 7.07 W. By incorporating the insulating plug, the actual heat leakage was reduced by 61.2%, decreasing to 2.74 W, and the calculated heat leakage is 2.47 W. The error margin in both cases was approximately 10%. Furthermore, in contrast to existing investigations, this experiment with the 8W@77K pulse tube cryocooler for recovering nitrogen is conducted under environmental pressure rather than overpressure, and it also takes into account the sensible heat issues caused by ambient pressure. The ratio of 1.81 W of sensible heat to 2.74 W of latent heat is 2:3, indicating that under ambient pressure conditions, the impact of sensible heat cannot be ignored. The key improvement methods are given to improve the success rate of the experiment. The research results provide a useful reference for the re-cycling and storage of liquid nitrogen.

Active phase and amplitude temperature control method for cryostat: A case in the thermodynamic temperature international comparison system

Achieving highly stable temperature control is essential for cryostats. However, the cryocooler used in cryostats, such as the pulse tube cryocooler, produces regular sinusoidal temperature fluctuations due to its inherent working principles. To establish a highly stable temperature environment, an active phase and amplitude control method for suppressing temperature fluctuation is proposed in this paper, by which the optimal phase and amplitude can be predicted in theory. To validate this approach, a thermal response model was developed based on experiments conducted in the thermodynamic temperature international comparison cryostat at approximately 3.7 K. Based on this model, we conducted both single-stage and multi-stage active temperature control experiments. The results demonstrate that the temperature control effect is the best when the active temperature control current is added at the second cold head, the fluctuation of the comparison copper block from 3.3mK to 0.166mK with 94.9 % suppression rate. The multi-stage joint temperature control reduced the temperature fluctuation with an attenuation rate of 95.4 %. These findings offer significant potential for improving temperature stability in future thermodynamic temperature comparison experiments.

Study on the refrigeration performance of a miniature pulse tube cryocooler driven by a gas bearing compressor

Recent advancements in long-term space exploration, maintenance-free miniature-satellites and drone infrared detections have created a large demand for highly reliable and miniaturized cryocoolers working at 77–150 K. The pulse tube cryocooler (PTC) has no moving part at the cold end, and if driven by a gas bearing linear compressor which has no mechanical fatigue risk, a refrigeration system with high reliability and compactness will be generated. However, very few researches on the cooling performance of PTC driven by gas bearing linear compressor have been reported. In this study, a miniature PTC and gas bearing compressor are developed, with a weight of the whole refrigeration system about 0.97 kg. The maximum cooling capacity reaches 1.73 W at 77 K with input electric power of 66 W. The cooling capacity per unit weight for this cryocooler is 1.78 W/kg at 77 K, which is the highest compared to those of the existing typical miniature cryocoolers, showing its remarkable lower mass for refrigeration. In addition, the influence of the hot end heat dissipation temperature on the cooling performance is studied. It is found that the heat dissipation temperature of the hot end has a significant effect on the cooling performance. For every 10 K decrease in the hot end temperature, the maximum cooling capacity at 77 K increases by 3.45 % to 13.28 %, the relative Carnot efficiency rises by 4.38 % to 12.59 %. Besides, in the miniature PTC, the cooling performance is very sensitive to the length of the inertance tube, even a small change of 10–20 mm on the length of the inertance tube will lead to obvious effect on the optimum frequency and cooling performance of the system. These results will be helpful for the further research and development of the miniature pulse tube cryocoolers.

The thermal performance model of a 105 mW@4.41 K 4He Joule-Thomson cryocooler designed for space applications

The 4He Joule-Thomson cryocooler (JTC) ensures the operation of space detectors working within the 4 K temperature range, such as the Block Impurity Band Infrared Detector (BIBID). In addition, the 4He JTC is one of the essential components of the 300 K to 50 mK space cryochain. It can precool sub-Kelvin refrigerators, such as the adiabatic demagnetization refrigerator (ADR) and the dilution refrigerator (DR). With the development of space science, the need for cooling power at the 4 K temperature range is growing. Thus, a thermal performance model of the 4He JTC precooled by a two-stage thermally coupled pulse tube cryocooler (PTC) is designed, manufactured, and tested with an eye toward space applications. A four-stage compression system with a high operating frequency and large pistons is designed and used to drive the JT cycle. This 4He JTC has a total mass of 55 kg and can provide a cooling capacity of 105 mW at 4.41 K with a total input electric power of 548 W.

Essential improvement of the JT cryocooler working at liquid helium temperature for space: Efficient and lightweight

Due to long lifetime, low level vibration and negligible electromagnetic interference, the Joule-Thomson (JT) cryocooler working at liquid helium temperature has been used in space. However, its cooling capacity and thermodynamic efficiency still need to be further improved under a certain mass limit, which is an essential improvement for space-efficient application of the JT cryocooler. Therefore, in this study, optimization design is carried out for a JT cryocooler working at liquid helium temperature. Based on the modification of Stirling cryocooler, pulse tube cryocooler and JT compressor, the developed JT cryocooler can provide a cooling capacity of 0.36 W at 4.18 K while the total input power and the total mass (without cryostat) are 1157 W and 26.8 kg, respectively. Compared with the literature research, it can be found that the developed JT cryocooler is suitable for space applications.

A Vibration Decoupling System for TES Operation in the COSINUS Dry Dilution Refrigerator

COSINUS will be among the first underground experiments to operate Transition Edge Sensors in a dry dilution refrigerator, measuring temperature changes on the order of μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}K. A pulse tube cryocooler is used to cool down to 3K, trading simplified handling, by not using liquid noble gases, for an increased vibration noise level in the acoustic frequency range. As the signals measured with a TES are in the same frequency region, it is necessary to decouple the detectors from all possible noise sources. In COSINUS, a two-level passive decoupling system was developed and tested using piezo-based accelerometers. At the first level, the refrigerator is mechanically isolated from all external noise sources. For the second level an internal spring-based system was developed and tested on a mockup system. On the first level a reduction of the vibrational background up to a factor 4 below 10 Hz could be measured. On the second level a resonance frequency of 1.2 Hz with damping of higher frequencies was achieved.

Numerical simulation and experimental verification of dynamic cooling and temperature control of the optical cavity in a CO2 isotope analyzer

Accurate measurement of CO2 generated from different emission sources is the basis for controlling CO2 emissions and mitigating global warming. With advantages of high accuracy and rapid response, isotope analyzers using spectroscopic techniques, particularly those using cavity ring-down spectroscopy, have been widely used for CO2 emissions monitoring. However, these analyzers often face challenges such as spectral interference from impurity gases and unstable temperature control within the optical cavity in isotope analyzers. To address these challenges, this paper proposes a low-temperature optical cavity scheme utilizing a split Stirling-type pulse tube cryocooler. Combining thermal boundary conditions with particle swarm optimization, a dynamic cooling and temperature control model of the optical cavity was established in MATLAB. The model subsequently analyzed the cooling process, temperature control, and stability of the optical cavity. After 120 h, the simulations showed that the central part of the optical cavity had cooled to 126.4 K with a heat leakage of 8.90 W, in agreement with the experimental results that stabilized at 126.8 K. The temperature fluctuations remained within 0.1 K/h while controlling an overall temperature of 170 K with a temperature difference of ± 5 K. Changes in the electrical input power of cryocooler had no influence on the temperature distribution. This advancement not only lowers the operating temperature of the optical cavity to minimize spectral interference but also enhances the precision and efficiency of temperature control.

Numerical and experimental investigation of 12 W/60 K high-efficiency coaxial pulse tube cryocooler

Maintaining a low-temperature environment is paramount in pursuing reliable operation for infrared detectors. To address the rising demand for long-wave infrared detectors functioning in low-temperature environments around 60 K, this study investigates the enhanced efficiency of a 60 K coaxial pulse tube cryocooler (PTC) through both simulation analysis and experimental methods. A PTC model was developed using Sage software to optimize parameters such as cold finger size. Analysis of the internal flow field highlighted that variations in cold head temperature, frequency, and input power significantly impact phase angle distribution within the regenerator. Experimental results yielded the same conclusion and confirmed how these critical factors affect the PTC’s performance. Through systematic optimization of simulations and experiments, a cooling performance of 12.7 W/60 K was achieved with an input power of 300 W. Furthermore, when the input power of the PTC was 200 W, a cooling capacity of 9.2 W/60 K was achieved, demonstrating a relative Carnot efficiency of 18.3 %.

Thermal Performance of a 4 K High-frequency Pulse Tube Cryocooler with Different Working Fluids

Thermal Performance of a 4 K High-frequency Pulse Tube Cryocooler with Different Working Fluids

Nanoscale thermal imaging of hot electrons by cryogenic terahertz scanning noise microscopy.

Nanoscale thermal imaging and temperature detection are of fundamental importance in diverse scientific and technological realms. Most nanoscale thermometry techniques focus on probing the temperature of lattice or phonons and are insensitive to nonequilibrium electrons, commonly referred to as "hot electrons." While terahertz scanning noise microscopy (SNoiM) has been demonstrated to be powerful in the thermal imaging of hot electrons, prior studies have been limited to room temperature. In this work, we report the development of a cryogenic SNoiM (Cryo-SNoiM) tailored for quantitative hot electron temperature detection at low temperatures. The microscope features a special two-chamber design where the sensitive terahertz detector, housed in a vacuum chamber, is efficiently cooled to ∼5K using a pulse tube cryocooler. In a separate chamber, the atomic force microscope and the sample can be maintained at room temperature under ambient/vacuum conditions or cooled to ∼110K via liquid nitrogen. This unique dual-chamber cooling system design enhances the efficacy of SNoiM measurements at low temperatures. It not only facilitates the pre-selection of tips at room temperature before cooling but also enables the quantitative derivation of local electron temperature without reliance on any adjustable parameters. The performance of Cryo-SNoiM is demonstrated through imaging the distribution of hot electrons in a cold, self-heated narrow metal wire. This instrumental innovation holds great promise for applications in imaging low-temperature hot electron dynamics and nonequilibrium transport phenomena across various material systems.

Experimental investigation of displacer type pulse tube refrigerator with inertance tube or orifice

Displacer type pulse tube refrigerator (DPTR) can get high efficiency with strong phase shifting and acoustic work recovery to advantages. However, the optimal match of gas driving displacer can only be reached at one point, while the linear motor driving displacer has a complex structure. And for two-stage DPTR, more parameters need to be optimized such as step ratio. A well-matched displacer costs a lot and asks high quality manufacturing. In this work, an orifice and an inertance tube were added to the single-stage DPTR and two-stage DPTR as an additional adjustment parameter. For single stage DPTR, the experimental results indicate that the lowest temperature decreases from 44.7 K to 42.1 K after a suitable inertance tube was added. The cooling power can be increased with almost same efficiency by adding an orifice with appropriate opening turn. After adding an additional inertance tube of the two-stage DPTR, the lowest temperature of 15.6 K was achieved, while the lowest temperature of 15.7 K was achieved by installing an orifice to the two-stage DPTR.

Design and Optimization of a High Frequency Miniature Pulse Tube Cryocooler

A micro coaxial pulse tube cryocooler has been developed for infrared detection. This paper presents the experimental data of performance and describes the optimization process of a pulse tube cryocooler in detail. With a tiny size and high frequency, this cryocooler is driven by the linear compressor. The combination of inertance tube and buffer is adopted as phase shifter. The effect of the structure and operating parameters on cooling performance are investigated through experiments. As a result, the regenerator has a dimension of 40 mm length, and the optimal frequency is 175 Hz. It can provide a cooling power of 0.5 W at 80 K with a 30 W input electric power and 0.8 W at 150 K with a 10 W input electric power.

Development of a 5 W/4.2 K two-stage pulse tube cryocooler

The 2.7 W/4.2 K two-stage pulse tube cryocooler (Model PT425) was developed and introduced by Cryomech, Inc. in 2021, which, at the time, was the largest, commercially available, 4 K pulse tube cryocooler. Our newest model, the PT450, has been successfully developed, providing a minimum of 5.0 W at 4.2 K on the 2nd stage with 65 W at 45 K on the 1st stage simultaneously, operating on either 60 or 50 Hz power. The PT450 answers the market’s need for the continuing development of large cryogen-free dilution refrigerators, superconducting magnets, helium liquefiers and other applications requiring large cooling capacities at 4 K.In addition, a new helium compressor (Cryomech CPA3027) has also been developed to provide sufficient helium flow for the PT450 and other large cooling power cryocoolers. This new model also allows multiple cryocoolers to operate on one compressor. The CPA3027 is the largest commercially available helium compressor for the Gifford-McMahon and pulse tube cryocooler market.The system configuration and main cooling performance of the PT450 cold head will be presented in this paper.

Cooling power analysis of a small scale 4 K pulse tube cryocooler driven by an oil-free low input power Helium compressor

Here we report the performance of a small scale 4 K pulse tube cryocooler operating with a low input power reaching a minimum temperature of 2.2 K, as well as a cooling capacity of over 240 mW at 4.2 K. The compressor is air cooled and can be supplied by single phase power sockets. With an input power of about 1.3 kW the coefficient of performance reaches values of up to 185 mW/kW, which is among the highest currently reported values for small to medium power pulse tubes. The combination of an oil-free Helium compressor and low maintenance pulse tube cryocooler provides a unique miniaturized, energy efficient and mobile cooling tool for applications at 4 K and below.

High Efficiency Operation of a 4K-Gifford-McMahon Cryocooler without Rotary Valve with a Metal Bellows Compressor

Traditional Gifford-McMahon cryocoolers are operated with an integrated rotary valve which regulates the compressed Helium supply and return into and from the cold head. Theory predicts that about 50% of the input energy is lost in this rotary valve [1]. In this work we removed the rotary valve from a Sumitomo RDK-101G cold head and drove the Gifford-McMahon cryocooler in Stirling-mode directly with a slow-moving metal bellows compressor at around 1.2Hz. We could demonstrate that the energy efficiency of the cryocooler system improves by almost 50%. As a result, we were able to operate this cold head with 650W of total electrical input power with a cooling power of 140mW at 4.2K on the second stage and no-load temperatures of below 40K on the first stage. This corresponds to a COP of 215mW/1000W which one of the highest COPs reached for small and medium size 4K GM and pulse tube cryocoolers.

Ball Modular Advanced Cryocooler Control Electronics (MACCE)

To support the application of heritage aerospace coolers and modern tactical coolers to future mission architectures, Ball has developed the Modular Advanced Cryocooler Control Electronics (MACCE). This entirely new cryocooler electronics architecture is based on modularity and scalability in performance supporting a wide range of cryocoolers including 4K Hybrid Systems (J-T + Pre-Cooler), Pulse Tube Cryocoolers, and Stirling Cryocoolers. The MACCE design includes the primary CCE box and an Accelerometer Pre-Amp (APA) box that can be remote mounted. The MACCE architecture includes four high power drive channels and two low power channels supporting >500W of output power, three independent accelerometer feedback control loops for vibration cancellation, high efficiency using GaN FET technology, and a combination of six thermistors and six precision RTD circuits for telemetry. Operational modes include constant power, constant temperature, or open loop. An engineering model of MACCE has been completed and is currently going through qualification. Performance data is presented from box level testing.

The simulation and experiments of a high frequency single stage pulse tube cryocooler with two cooled thermal sinks

In the application of infrared detectors, pulse tube cryocoolers are required to provide cooling power at different temperature ranges simultaneously with light weight and compact construction. In this paper, a single stage pulse tube cryocooler was designed to provide cooling power at different temperature ranges with an extra cooled thermal sink placed in the middle of the regenerator. The axial distribution of volume flow and pressure wave of cryocooler with middle heat exchanger and without middle heat exchanger were compared theoretically. To verify the simulation results, a series of experiments were carried out. As a result, the cooling power of cryocoolers with middle heat exchanger was decreased at 80 K, and 0.5 W @ 88.5 K & 0.5 W @ 195.8 K of cooling power was obtained simultaneously at 45 W input power.