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Thermal link is an important carrier used to transfer the cooling capacity and suppress the temperature fluctuation in cryostat. To balance these two points, it is usually necessary to find the optimum thermal link parameters. This paper establishes a model for the cryocooler cold head-thermal link-second flange based on a cryostat. Utilizing the response surface method, response equations correlating thermal link parameters with the temperature and its fluctuations of the second stage flange are developed at the lowest temperature of cryocooler. Through dual-objective optimization of cooling capacity transfer and temperature fluctuations at the second flange, the optimal thermal link parameters are determined and experimentally validated based on predicted results. The experimental and predicted values show good agreement with an error of 2 %. The optimized thermal link led a minor temperature increase and a significant temperature fluctuation reduction, decreasing from 230mK at the cold head to 2.900mK at the second flange, achieving a 98.74 % reduction. Furthermore, compared with non-optimization structure, the optimization one has further lowered the temperature fluctuation at the second flange from 4.000mK to 2.900mK with 27.5 % improvement. These results show that the present methods are reliable and useful to help to realize highly stable low-temperature environment in cryostat. [ABSTRACT FROM AUTHOR]

The Leighton Chajnantor Telescope (LCT) is an international collaborative program among Caltech, Shanghai Normal University (ShNU), and Universidad de Concepción (UdeC), aiming at the refurbishment and relocation of the Caltech Submillimeter Observatory (CSO) telescope from Mauna Kea, Hawaii, to the Chajnantor Plateau, northern Chile. A suite of excellent-sensitivity heterodyne superconductor–insulator–superconductor (SIS) receivers will be deployed to the telescope as the first set of instrumentations for high-resolution spectral observation. However, the current refrigeration technology for this receiver utilizes liquid helium (LHe), which greatly increases the cost of cooling and labor. To address this problem, a new LHe-free cryostat for the LCT heterodyne SIS receiver has been designed, fabricated, and tested. Mechanical and thermal analyses were performed to ensure that the cryostat meets the requirements of the telescope pointing accuracy and the SIS junction working environment, respectively. The experiment testing results are in good agreement with the calculation and analysis, indicating that the proposed LHe-free cryostat meets the operational requirements of the telescope at the new site. [ABSTRACT FROM AUTHOR]

Treatment with hydrostatic pressure of 10 MPa for 5 min stimulates the accelerated germination of lettuce seeds. Treatment with liquid oxygen has a depressing effect on seeds. In contrast, treatment of the same duration in liquid argon stimulates seed germination. The delay between seed treatment and germination has a negative impact on their sowing quality. Raising the temperature of seed storage enhances this effect. [ABSTRACT FROM AUTHOR]

As a specific device for light production, undulators have been researched and developed since the third generation of synchrotron photon sources. Nowadays, superconducting undulators become a research hotspot. However, the cryostat, which is used to create a liquid helium temperature environment, often causes the failure of the superconducting undulator. In this paper, a cryostat for a superconducting undulator is designed and investigated. First, a new refrigeration distribution is proposed that can provide more excess cooling capacity at 4.2 K temperature. For the cooling of the superconducting magnet, a liquid helium circulation loop based on the thermosiphon effect is designed, which has no pump or any other moving parts. Next, based on high-temperature superconducting technology, six binary current leads are used to decrease the heat load. The beam chamber is cooled below 20 K to reduce possible effect on the magnet. In addition, for the tubes that connect the 4.2 K helium tank to the room temperature component, the thermoacoustic oscillation is studied. In the experiment, the superconducting magnet could be cooled and maintained at 4.2 K depending on the thermosiphon loop. No helium was discharged when the magnet went through a quench which generated large heat in a short time. There was no liquid helium consumption and the excess cooling capacity reached 2.2 W. The maximum magnet current is as high as 470 A. This study can provide a valuable reference for the development of superconducting undulator cryostats. [ABSTRACT FROM AUTHOR]

CUPID is a next-generation tonne-scale bolometric neutrinoless double beta decay experiment that will probe the Majorana nature of neutrinos and discover lepton number violation in case of observation of this singular process. CUPID will be built on experience, expertise and lessons learned in CUORE and will be installed in the current CUORE infra-structure in the Gran Sasso underground laboratory. The CUPID detector technology, successfully tested in the CUPID-Mo experiment, is based on scintillating bolometers of Li2MoO4 enriched in the isotope of interest 100Mo. In order to achieve its ambitious science goals, the CUPID collaboration aims to reduce the backgrounds in the region of interest by a factor 100 with respect to CUORE. This performance will be achieved by introducing the high efficient α/β discrimination demonstrated by the CUPID-0 and CUPID-Mo experiments, and using a high transition energy double beta decay nucleus such as 100Mo to minimize the impact of the gamma background. CUPID will consist of about 1500 hybrid heat-light detectors for a total isotope mass of 250 kg. The CUPID scientific reach is supported by a detailed and safe background model based on CUORE, CUPID-Mo and CUPID-0 results. The required performances have already been demonstrated and will be presented.

Superconducting undulators (SCUs) can offer a much higher on-axis undulator field than state-of-the-art cryogenic permanent-magnet undulators with the same period and vacuum gap. The development of shorter-period and high-field SCUs would allow the free-electron laser and synchrotron radiation source community to reduce both the length of undulators and the dimensions of the accelerator. Magnetic measurements are essential for characterizing the magnetic field quality of undulators for operation in a modern light source. Hall probe scanning is so far the most mature technique for local field characterization of undulators. This article focuses on the systematic error caused by thermal contraction that influences Hall probe measurements carried out in a liquid helium cryostat. A novel procedure, based on the redundant measurement of the magnetic field using multiple Hall probes at known relative distance, is introduced for the correction of such systematic error.

Superconducting undulators (SCUs) can offer a much higher on-axis undulator field than state-of-the-art cryogenic permanent-magnet undulators with the same period and vacuum gap. The development of shorter-period and high-field SCUs would allow the free-electron laser and synchrotron radiation source community to reduce both the length of undulators and the dimensions of the accelerator. Magnetic measurements are essential for characterizing the magnetic field quality of undulators for operation in a modern light source. Hall probe scanning is so far the most mature technique for local field characterization of undulators. This article focuses on the systematic error caused by thermal contraction that influences Hall probe measurements carried out in a liquid helium cryostat. A novel procedure, based on the redundant measurement of the magnetic field using multiple Hall probes at known relative distance, is introduced for the correction of such systematic error. [ABSTRACT FROM AUTHOR]

Dysprosium(III)-containing single-molecule magnets (SMMs) show blocking of the molecular magnetization and hysteresis effects in one molecule. They belong to the class of the best performing SMMs at present. Here, we present first results of 161Dy-Nuclear Resonance Vibrational Spectroscopy (NRVS) experiments on the dysprosium(III) complex [Dy(H2dapp)(NO3)2](NO3) with H2dapp being 2,6-bis((E)-1-(2-(pyridine-2-yl)-hydrazineylidene)ethyl)pyridine. For the 161Dy-NRVS experiments a compact novel He flow cryostat was used at the Advanced Photon Source, Argonne National Laboratories, which enables low temperature NRVS experiments in helium vapour circumventing the often-observed difference between sensor read and "real" sample temperature in mostly used LHe and/or closed cycle cryostats with the NRVS sample being in vacuum. To explore the vibrational modes of the molecule simulations based on first density functional theory (DFT) calculations are presented. [ABSTRACT FROM AUTHOR]

Purpose: The precision of the dose delivery in radiation therapy with high-field MR-linacs is challenging due to the substantial variation in the beam attenuation of the patient positioning system (PPS) (the couch and coils) as a function of the gantry angle. This work aimed to compare the attenuation of two PPSs located at two different MR-linac sites through measurements and calculations in the treatment planning system (TPS). Methods: Attenuation measurements were performed at every 1° gantry angle at the two sites with a cylindrical water phantom with a Farmer chamber inserted along the rotational axis of the phantom. The phantom was positioned with the chamber reference point (CRP) at the MR-linac isocentre. A compensation strategy was applied to minimise sinusoidal measurement errors due to, e.g. air cavity or setup. A series of tests were performed to assess the sensitivity to measurement uncertainties. The dose to a model of the cylindrical water phantom with the PPS added was calculated in the TPS (Monaco v5.4 as well as in a development version Dev of an upcoming release), for the same gantry angles as for the measurements. The TPS PPS model dependency of the dose calculation voxelisation resolution was also investigated. Results: A comparison of the measured attenuation of the two PPSs yielded differences of less than 0.5% for most gantry angles. The maximum deviation between the attenuation measurements for the two different PPSs exceeded ±1% at two specific gantry angles 115° and 245°, where the beam traverses the most complex PPS structures. The attenuation increases from 0% to 25% in 15° intervals around these angles. The measured and calculated attenuation, as calculated in v5.4, was generally within 1-2% with a systematic overestimation of the attenuation for gantry angles around 180°, as well as a maximum error of 4-5% for a few discrete angles in 10° gantry angle intervals around the complex PPS structures. The PPS modelling was improved compared to v5.4 in Dev, especially around 180°, and the results of those calculations were within ±1%, but with a similar 4% maximum deviation for the most complex PPS structures. Conclusions: Generally, the two tested PPS structures exhibit very similar attenuation as a function of the gantry angle, including the angles with a steep change in attenuation. Both TPS versions, v5.4 and Dev delivered clinically acceptable accuracy of the calculated dose, as the differences in the measurements were overall better than ±2%. Additionally, Dev improved the accuracy of the dose calculation to ±1% for gantry angles around 180°.

The precision of the dose delivery in radiation therapy with high-field MR-linacs is challenging due to the substantial variation in the beam attenuation of the patient positioning system (PPS) (the couch and coils) as a function of the gantry angle. This work aimed to compare the attenuation of two PPSs located at two different MR-linac sites through measurements and calculations in the treatment planning system (TPS). Attenuation measurements were performed at every 1° gantry angle at the two sites with a cylindrical water phantom with a Farmer chamber inserted along the rotational axis of the phantom. The phantom was positioned with the chamber reference point (CRP) at the MR-linac isocentre. A compensation strategy was applied to minimise sinusoidal measurement errors due to, e.g. air cavity or setup. A series of tests were performed to assess the sensitivity to measurement uncertainties. The dose to a model of the cylindrical water phantom with the PPS added was calculated in the TPS (Monaco v5.4 as well as in a development version Dev of an upcoming release), for the same gantry angles as for the measurements. The TPS PPS model dependency of the dose calculation voxelisation resolution was also investigated. A comparison of the measured attenuation of the two PPSs yielded differences of less than 0.5% for most gantry angles. The maximum deviation between the attenuation measurements for the two different PPSs exceeded ±1% at two specific gantry angles 115° and 245°, where the beam traverses the most complex PPS structures. The attenuation increases from 0% to 25% in 15° intervals around these angles. The measured and calculated attenuation, as calculated in v5.4, was generally within 1-2% with a systematic overestimation of the attenuation for gantry angles around 180°, as well as a maximum error of 4-5% for a few discrete angles in 10° gantry angle intervals around the complex PPS structures. The PPS modelling was improved compared to v5.4 in Dev, especially around 180°, and the results of those calculations were within ±1%, but with a similar 4% maximum deviation for the most complex PPS structures. Generally, the two tested PPS structures exhibit very similar attenuation as a function of the gantry angle, including the angles with a steep change in attenuation. Both TPS versions, v5.4 and Dev delivered clinically acceptable accuracy of the calculated dose, as the differences in the measurements were overall better than ±2%. Additionally, Dev improved the accuracy of the dose calculation to ±1% for gantry angles around 180°. [ABSTRACT FROM AUTHOR]

The main devices for generating synchrotron radiation at the SKIF synchrotron light facility under construction will be superconducting wigglers and undulators created at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. This report presents the rationale for the choice of operating parameters, the main characteristics and design features of these devices, and their current development status. [ABSTRACT FROM AUTHOR]

Irradiation of a cooled matrix photodetector by parasitic radiation in a cryostat for different shapes and designs of a cold diaphragm is numerically simulated. It is found that the optimal shape of a cold diaphragm is a cylinder with two internal optics diaphragms (additional diaphragms). Irradiation of the matrix photodetector by parasitic radiation is about W cm with an uneven distribution over the area of about 3 . [ABSTRACT FROM AUTHOR]

The microwave SQUID multiplexer (μ MUX) is a high channel-count multiplexer that, when coupled to low-temperature detectors such as Transition Edge Sensor (TES) Bolometers, has applications across astronomy and physics. Our primary application is for the Simons Observatory, an array of CMB polarimeters utilizing over 70,000 μ MUX readout channels, located in the Atacama Desert. To facilitate the delivery of high-quality multiplexers to the project, we have developed a high-throughput microwave SQUID screening measurement system, capable of measuring microwave devices operating over the frequency range of 4–8 GHz. Here, we present the hardware design comprised of a cryogen-free 100 mK 2-stage Adiabatic Demagnetization Refrigerator (ADR) cryostat, microwave packages which hold μ MUX chips, and the microwave readout chain necessary to do these measurements. In addition, we describe the screening protocols and show example results. [ABSTRACT FROM AUTHOR]

A new technology for replenishing daily nitrogen losses (200 g/day) in the atmosphere of the Russian segment of the International Space Station and for cooling the on-board electronic devices is proposed. This technology can be used to create systems for solid nitrogen storage and for release of gaseous nitrogen to create an atmosphere in the living compartments at space stations and, in the future, at the Lunar Station. [ABSTRACT FROM AUTHOR]

Crystalline optical cavities operating at cryogenic temperatures provide a promising route for realizing the next generation of ultrastable lasers with extremely low thermal noise floor. However, it remains challenging to realize a closed-cycle cryostat for cooling a relatively long cavity to very low temperatures. Here we report on the design and experimental realization of a cryostat operating continuously at 3.1 K for an ultrastable 10-cm silicon cavity. Based on a combination of active temperature control and passive thermal damping, we realize at 3.1 K a two-second temperature instability of 6 × 10−8 K for the cavity. By implementing separate supporting structures for the cryocooler and the sample chamber, we realize vibration control on the 1 × 10−7g level at one second in each spatial direction, where g is the gravitational acceleration. With all these features, our cryostat can support an ultrastable silicon cavity with instability near its fundamental thermal noise floor at averaging time of 1–50 s. With proper upgrading, our platform holds promise for realizing ultrastable lasers with 3 × 10−17 or better frequency stability, which will in turn enable numerous studies on precision metrology and quantum many-body physics.

Recently, there has been growing interest in using lightwave-driven scanning probe microscopy (LD-SPM) to break through the Abbe diffraction limit of focusing, yielding insight into various energy couplings and conversion processes and revealing the internal information of matter. We describe a compact and efficient optical cryostat designed for LD-SPM testing under magnetic fields. The exceptional multilayer radiation shielding insert (MRSI) forms an excellent temperature gradient when filled with heat conducting gas, which removes the requirement to install an optical window in the liquid helium cooling shell. This not only critically avoids the vibration and thermal drift caused by solid heat conduction but also minimizes light transmission loss. The application of gate valves and bellows allows a simpler and more effective replacement of the sample and working cell in the test cavity. ANSYS software is used for steady-state thermal analysis of the MRSI to obtain the temperature distribution and heat transfer rate, and the necessity of the flexible copper shielding strips is illustrated by the simulations. The topography and magnetic domain images of 45 nm-thick La0.67Ca0.33MnO3 thin films on NdGaO3(001) substrates under a magnetic field were obtained by a self-made lightwave-driven magnetic force microscope in this cryostat. The resolution and noise spectra during imaging reveal temperature stability and low vibration throughout the cryostat. The experience acquired during the development of this cryostat will help to establish cryostats of similar types for a variety of optic applications requiring the use of cryogenic temperatures. [ABSTRACT FROM AUTHOR]

Objective: The primary goal of the intraoperative Frozen Section biopsy in a clinically suspected Central Nervous System (CNS) neoplasm is to evaluate the submitted tissue for rapid diagnosis, which helps in proper management during open craniotomy. In this study, the accuracy of frozen section in the diagnosis of CNS neoplasms and discrepancies in diagnosis were analyzed. Material & Methods: Ninety cases of CNS neoplasms were examined over a period of one year. All the cases were open biopsies performed at Neurosurgery Department &intra-operative frozen section (by cryostat) was performed & reported in the Histopathology section of a referral center in Eastern Odisha. The diagnoses given on FS were compared with the final diagnosis given on permanent paraffin embedded tissue sections. Results: In all cases, cryostat sections were prepared and a provisional diagnosis was given. Final histopathological diagnosis was given by studying the Hematoxylin & Eosin (H&E) section. Out of these 90 cases, 81 cases (90.0 %) were concordant, 9 cases (10.0 %) were discrepant. The discrepancies occur in mainly differentiating astrocytomas from oligodendrogliomas & schwannoma from meningioma along with few over-grading of glioma cases. Conclusion: Our results showed a reasonably high percentage of accuracy in the intraoperative diagnosis of CNS lesions. However, freezing artifact, obscuring cytological detail, heterogenous features of gliomas and lack of proper clinical inputs were the major causes for discrepancies. [ABSTRACT FROM AUTHOR]

Detection of the magnetic signature of ships can be avoided by using a degaussing system; a set of on-board copper coils that compensates for the magnetic signature. High temperature superconductors (HTS) are currently investigated as a replacement for copper degaussing coils. By using HTS, we have to deal with higher currents and therefore with higher power supply losses. Also, large current leads are needed which introduces extra losses. This paper investigates different possible solutions to minimize these losses. Four H-bridge-based MOSFET topologies are presented that were designed to reduce the power supply and current lead losses. The first topology uses an H-bridge configuration so that the degaussing current can freewheel through the low-resistance MOSFETs. The second topology places the H-bridge inside the cryostat so that the current leads can be made smaller. The third topology includes a smoothing capacitor in the cryostat so that the current leads and input current are even smaller. The fourth topology uses a transformer so that the current leads can be eliminated. Measurements were done to determine the MOSFETs and capacitor performance in liquid nitrogen. The simulated losses of the four topologies are compared to determine the most energy-efficient option for supplying current to the HTS coils. It was found that by submerging multiple parallel MOSFETs in liquid nitrogen, the on-state resistance is decreased and the current supply can be made more efficient. Also, by placing a smoothing capacitor inside the cryostat, the current lead losses can be minimized significantly. The benefits of using a transformer do not outweigh the transformer losses.

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The Einstein Telescope is Europe's next generation gravitational-wave detector. To develop all necessary technology, four research facilities have emerged across Europe: The Amaldi Research Center (ARC) in Rome (Italy), ETpathfinder in Maastricht (The Netherlands), SarGrav in the Sos Enattos mines on Sardinia (Italy) and E-TEST in Liége (Belgium) and its surroundings. The ARC pursues the investigation of a large cryostat, equipped with dedicated low-vibration cooling lines, to test full-scale cryogenic payloads. The installation will be gradual and interlaced with the payload development. ETpathfinder aims to provide a low-noise facility that allows the testing of full interferometer configurations and the interplay of their subsystems in an ET-like environment. ETpathfinder will focus amongst others on cryogenic technologies, silicon mirrors, lasers and optics at 1550 and 2090 nm and advanced quantum noise reduction schemes. The SarGrav laboratory has a surface lab and an underground operation. On the surface, the Archimedes experiment investigates the interaction of vacuum fluctuations with gravity and is developing (tilt) sensor technology for the Einstein Telescope. In an underground laboratory, seismic characterisation campaigns are undertaken for the Sardinian site characterisation. Lastly, the Einstein Telecope Euregio meuse-rhine Site & Technology (E-TEST) is a single cryogenic suspension of an ET-sized silicon mirror. Additionally, E-TEST investigates the Belgian–Dutch–German border region that is the other candidate site for Einstein Telescope using boreholes and seismic arrays and hydrogeological characterisation. In this article, we describe the Einstein Telescope, the low-frequency part of its science case and the four research facilities. [ABSTRACT FROM AUTHOR]

Partially high-temperature superconducting generators (PHTSGs) feature large magnetic air gaps imposed by using cryostats for HTS field windings. This increased air gap significantly affects end winding inductance and can lead to elevated fault torque levels. This study investigates the influence of magnetic air gap variation on generator design and end winding inductance and its implications for short-circuit faults in PHTSGs. Through a combination of numerical simulations and analytical analysis, the study explores how changes in the magnetic air gap affect end winding inductance and subsequently influence short-circuit fault behavior. The results reveal a direct correlation between magnetic air gap length, end winding inductance, and key short-circuit parameters such as stator current, field currents, and electromagnetic torque. Notably, an increase in the magnetic air gap is observed to elevate stator and field currents and electromagnetic torque during short-circuit events. These insights underscore the importance of considering magnetic air gap variation and its impact on end winding inductance and its relationship with short circuit characteristics in the design and operation of PHTSGs, providing valuable insights for enhancing the resilience and performance of high-temperature superconductor-based generator systems. [ABSTRACT FROM AUTHOR]

• Automated sample exchange cryostat with low background mounted on SANS at CSNS. • The sample changer system holds four samples simultaneously and exchanges samples automatically. • The system has accurate temperature control performance ranging from 10 ∼ 500 K. The Small-angle Neutron Spectrometer at China Spallation Neutron Source (SANS_CSNS) is a functional apparatus utilized for the examination of structures and inhomogeneities within the size range of 1 to 100 nm. The development of sample environments for in situ experiments at low temperatures at SANS_CSNS is urgent in order to address the increasing demands of users. The CSNS Sample Environment Group has successfully designed and constructed an automated sample exchange cryostat for SANS experiments, capable of operating in a temperature range of 10 ∼ 500 K. This cryostat has been specifically engineered to accommodate up to four samples simultaneously and exchange samples automatically in order to optimize the utilization of neutron beams by minimizing the downtime associated with manual sample handling. The results of simulation and temperature measurement proved that sample temperature could be accurately controlled from 10 K to 500 K through the incorporation of a 4 K GM cryocooler and a heater. Furthermore, neutron scattering studies conducted on SANS_CSNS proved that this cryostat exhibits commendable temperature control capabilities and minimal background interference. This automated sample exchange cryostat will be available to researchers of SANS_CSNS in the following user programs. [ABSTRACT FROM AUTHOR]

The theory of these temperature effects on phonons is complicated [[9], [63]], but can be summarized as follows: An optical phonon has a finite lifetime on the order of a few 10 SP -12 sp s. Through an anharmonic perturbation of the Hamiltonian I H i SB 0 sb with self-energy , long-wavelength optical phonons can decay into two or more acoustic phonons. While the redshift of the main absorption peak of Ni at 4.8 eV with increasing temperature is similar to Si, Ge, and many other semiconductors, the temperature dependence of the broadening of this peak shows a very unusual behavior, see Figure 11. For metals and doped semiconductors, the temperature dependence of the Drude term is therefore dominated by the broadening parameter, which increases with temperature, similar to the broadening of band gaps and phonons shown in Figures 8 and 14. Keywords: cryostat; dielectric function; electron-phonon interaction; spectroscopic ellipsometry; temperature; windows EN cryostat dielectric function electron-phonon interaction spectroscopic ellipsometry temperature windows 117 135 19 08/09/22 20220501 NES 220501 1 Introduction Spectroscopic ellipsometry [[1]], [[2]], [[3]] is an optical reflection technique based on the polarization of electromagnetic waves. Cardona and S. Gopalan, "Temperature dependence of the band structure of semiconductors: electron-phonon interaction", in Progress in Electron Properties of Solids. [Extracted from the article]

The optimal design of a cooled infrared flip-chip photodetector for installation in a cryostat was determined for configurations that either maintain the ability to bend during cooling or have rigid attachment to the platform through a sapphire wafer. A radially symmetric composite photodetector model: GaAs (first layer)–In (ring structures)–Si–GaAs (second layer) with a diameter of 10 mm is numerically calculated. The maximum deformation loads in the edge indium ring for composites with different thicknesses (0 to 700 m) are determined when the photodetector is cooled to 77 K. For the photodetector model that is able to bend when mounted on a cryostat platform the optimal design is determined: GaAs(1) and Si wafers with a thickness of about 50 m and without GaAs(2); the maximum deformation loads in the edge indium ring (with a width of 15 m and thickness of 5 m) were about 427 MPa. When the model is rigidly mounted on the cryostat platform, the optimal design is 50 m-thick GaAs(1) and Si wafers and a 100 m-thick GaAs(2) compensation layer; the maximum deformation loads in the edge indium ring under these conditions were 600 MPa. [ABSTRACT FROM AUTHOR]

JT-60SA is the superconducting tokamak that will be operated at the Naka Fusion Institute of QST (the National Institutes for Quantum and Radiological Science and Technology) in Japan. The project is being developed under the framework of the Broader Approach Agreement between the EU and Japan (started in 2007) for an early realization of the fusion energy, aimed at conducting supportive and complementary work for the ITER experimental program towards DEMO. The assembly of the tokamak components as well as the related equipment was completed last year and the device is currently undergoing the integrated commissioning phase.Within the European contribution, Spain was one of the stakeholders that committed it, as a Voluntary Contributor, to design and manufacture one of the main components of the device: the cryostat. The cryostat is a large stainless steel vacuum vessel, 14 m diameter, 16 m high, which encloses the tokamak and provides the vacuum boundary (10−3 Pa) necessary to limit the heat loads on the magnets operated at cryogenic temperatures. The component is made up of the Cryostat Base (CB), the Cryostat Vessel Body Cylindrical Section (CVBCS), both designed and fabricated in Spain (through the National Fusion Laboratory at Ciemat), as well as the cryostat top lid (CTL) designed and procured by Japan (through QST).Within the manufacturing phases of the CB and CVBCS an extensive test program was carried out at Ciemat that focussed on the characterization of the welding processes selected for the manufacturing before their final approval. The aim of this paper is to present the results of the mechanical and microstructural tests performed on the welded joints.

The conceptual project of the construction of the cryostat and vacuum chamber was prepared, which are two of the main components of the compact tokamak with reactor technologies. The main technical solutions of the construction were decided, such as its configuration, technical characteristics, and operating regimes of its components. Conceptually, the cryostat is a single-wall cylindrical vacuum chamber made from austenitic stainless still that contains the superconducting electromagnetic system, the vacuum chamber, and the thermal protection of the cryostat and the vacuum chamber. The maximum diameter of the cryostat is of 12 m, its height is of 11 m, and its mass is of 317 t. In the cryostat, vacuum of 1 × 10–4 Pa can be established. The vacuum chamber is an all-welded double-wall construction made from austenitic stainless still. Its inner and outer shells are connected by a set of toroidal and poloidal stiffening ribs, in the space between which borated water is circulating. The sickness of the shells and of the stiffening ribs is of 25 mm. The outer diameter of the chamber is of 6.64 m and its height is of 3.85 m. [ABSTRACT FROM AUTHOR]

Abstract The use of high temperature superconducting (HTS) radio frequency (RF) coils in Magnetic Resonance Imaging (MRI) greatly improves the signal-to-noise ratio (SNR) in many biomedical applications and particularly in micro-MRI. However, a detailed understanding of the electrical behavior of HTS coils is important in order to optimize their performance through MR experiments. This paper presents a simple and versatile cryogen-free cryostat designed to characterize the RF properties of HTS coils prior to their use in MRI. The cryostat can be used at temperatures from 50 K to 300 K, with a control precision of approximately 3 mK at 70 K, and can measure the RF electrical power transmitted to an HTS coil over a range from 1 μW to 10 W. The quality factor and resonance frequency of the tested HTS coil are determined as a function of the temperature and the power it dissipates. This cryostat also permits the dynamic adjustment of the coil resonance frequency via temperature control. Finally, this study demonstrates that the HTS coil takes less than 12 μs to transit from the superconducting to the dissipative state, which is compatible with MRI requirements.

Recently, there has been growing interest in using lightwave-driven scanning probe microscopy (LD-SPM) to break through the Abbe diffraction limit of focusing, yielding insight into various energy couplings and conversion processes and revealing the internal information of matter. We describe a compact and efficient optical cryostat designed for LD-SPM testing under magnetic fields. The exceptional multilayer radiation shielding insert (MRSI) forms an excellent temperature gradient when filled with heat conducting gas, which removes the requirement to install an optical window in the liquid helium cooling shell. This not only critically avoids the vibration and thermal drift caused by solid heat conduction but also minimizes light transmission loss. The application of gate valves and bellows allows a simpler and more effective replacement of the sample and working cell in the test cavity. ANSYS software is used for steady-state thermal analysis of the MRSI to obtain the temperature distribution and heat transfer rate, and the necessity of the flexible copper shielding strips is illustrated by the simulations. The topography and magnetic domain images of 45 nm-thick La0.67Ca0.33MnO3 thin films on NdGaO3(001) substrates under a magnetic field were obtained by a self-made lightwave-driven magnetic force microscope in this cryostat. The resolution and noise spectra during imaging reveal temperature stability and low vibration throughout the cryostat. The experience acquired during the development of this cryostat will help to establish cryostats of similar types for a variety of optic applications requiring the use of cryogenic temperatures.

A key component in superconducting magnetic energy storage (SMES) system design is the cooling system. A well-designed cooling apparatus allows a SMES to work with higher critical currents, have less AC losses and work in a stable way. Acknowledging the importance of cooling systems in a SMES and that there have been many different designs presented in the bibliography, we hereby analyze various thermal designs that utilize cryocoolers, and we estimate the total volume of the superconducting coils used in their experiments. This review article focuses on recent high temperature superconducting (HTS) materials, and presents the cooling methods employed to cool the coil in conjunction with other important characteristics, such as the coil geometry, the operating temperature of the magnet, the thermal insulation temperature and the cooling power of the cryocoolers. From the presented analysis, the authors propose a procedure to devise a proper cooling scheme for a SMES design. Additionally, a qualitative comparative assessment of the analyzed designs in literature, in eight assessment criteria, is presented. [ABSTRACT FROM AUTHOR]

BackgroundSuperconducting undulator (SCU) prototype with small magnet gap of 5 mm, long magnet length of 4 m and high magnet field of 1.58 T was being developed at Shanghai High Repetition rate XFEL and Extreme light facility (SHINE). Compared to any other superconducting undulator, there is no cryocooler being installed on the cryostat in this SCU prototype.PurposeThis study aims at the cooling design for the binary current leads for SCU's normal operating.MethodsBinary current leads composed of normal conductive copper leads and high temperature superconducting current leads (HTS) were adopted for SCU to connect superconducting coils inside the cryostat and outer cables. Low-temperature helium gas was used to transport independent refrigerator system to the cooling tubes inside the prototype, hence the binary current leads were cooled. Thermal conduction components installed on the middle of the thermal shield were employed to transfer heat load of normal conductive copper leads, and heat load of copper leads was optimized by simulation. Auxiliary superconducting rods were designed for connecting cold ends of HTS in the cryostat test.ResultsThe temperature difference between hot ends of HTS and low-temperature helium gas is less than 20 K from the result of cryostat test, all binary current leads is operating normally with full current.ConclusionsIt is practicable to use cooling tubes with low-temperature helium gas to cool binary current leads of the SCU prototype by thermal conduction, which is different from cooling solution for current leads in any other SCU being developed presently.

In the scope of the Future Circular electron positron Collider study (FCC-ee), the IDEA detector is developed. It comprises a superconducting solenoid with free bore of 4 m, 6 m long and a central magnetic field of 2 T. The positioning of the magnet between the inner tracker and the electronic calorimeter heavily constrains the magnet design, as it is required to have the lowest possible radiation length, so minimum thickness and lowest density material. With respect to the classical solution of a solenoid enclosing the calorimeters, a cost reduction of about 50% is expected due to size reduction. An optimization of the different components of the magnet system has been carried out, resulting in the development of a new composite high-strength conductor that can be used to build a 30 mm thin solenoid. The quench analysis of the solenoid will be presented as it is of critical importance given the high energy density in the magnet of 21 kJ/kg. A cryostat made of concentric aluminium shells would account for about 50% of the radiation length of the magnet and most of this material is used in the outer vacuum shell of the cryostat to prevent buckling. In order to further reduce the radiation length, two fundamentally different approaches are being analysed. The first method focuses on reducing drastically the outer shell thickness. This leads to use honeycomb composites, reinforcing bars and corrugated shells for the outer shell of the cryostat. The second approach consists of supporting very thin cryostat shells directly on the solenoid cold mass using proper support. This can be achieved by replacing the thick walls and MLI insulation by a material that can sustain 1 atm while having low radiation length and low thermal conductivity. Cryogel Z has shown promising properties and its suitability for this project is being analysed. This novel approach has never been used so far for superconducting magnets. [ABSTRACT FROM AUTHOR]

Reflection of infrared radiation by coatings of diaphragms in photodetectors of thermal imaging devices (black polymeric dyes, anodic oxides, etched kovar, suspended graphite or titanium oxide in a cryogen-resistant varnish, etc.) is studied. The spectra and integral coefficients of reflection by diaphragm coatings in the wavelength range of m at radiation incidence angles of 15 and 45 are found. In addition, levels of reflected infrared radiation are studied in the spectral ranges of and m in a wide range of angles from 0 to 80 at the incidence angle of about 15 . Based on the research findings, it is found that the coating of suspended graphite in a cryogen-resistant varnish (developed in the Design and Technology Institute of Applied Microelectronics, Novosibirsk) has the lowest level of IR radiation reflection. The integral reflection coefficients for this coating were equal to 3.98 (in the spectral range of m) and 5.69 (in the range of m). [ABSTRACT FROM AUTHOR]

Key message: Distributions of water- and air-filled conduits can be distinguished by observing a xylem cross-section of frozen conifer stem. This method is applicable to field observation in cold winter. Xylem embolism resulting from summer drought and frost drought is one of the critical stresses responsible for the dieback of stems and individuals of subalpine evergreen conifers. The occurrence of xylem embolism in conifers depends not only on the species but also on the plant microhabitats, causing difficulties in understanding possible adaptive strategies against xylem embolism. This study examines a simple method of using a digital camera to photograph the xylem water distribution (CXW method) in cross-sections of frozen stems. Light is transmitted through the water-filled tracheid lumen but reflects and scatters at the surface of embolized tracheids, resulting in contrast in wood color between darker (water-filled tracheids) and lighter (air-filled tracheids) colored regions. The CXW method was effective in detecting water distribution in conifers, although the colored xylem in latewood and reaction wood decreased the color contrast between air- and water-filled regions. By cutting the frozen stem with a cryostat, sequential changes in the water distribution of stem xylem were easily monitored. In the cold winter of the subalpine region, the spatial distribution of embolized conduits can be detected when a branch is collected. If a cryostat is available, this method is applicable to other tracheid-bearing wood collected in any season and does not require additional instruments or time-consuming intensive labor in the field. Information about the hydraulics of conifers growing in extreme environments contributes to the understanding of their adaptive strategy and facilitates accurate prediction of forest dynamics under future climatic conditions. [ABSTRACT FROM AUTHOR]