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In this paper, we present the giant magnetocaloric effect exhibited by the Mn1-x(Ti0.5V0.5)xAs compound with x=0.1. The ordering temperature decreases from 318 K in the case of MnAs (x=0) to 266 K in the case of Mn0.9Ti0.05V0.05As (x=0.1). A large magnetic entropy change -ΔSm attributed to a first order magnetic transition has been observed. For Mn0.9Ti0.05V0.05As, the maximum of -ΔSm occurs near TC=266 K and is about 30 J/kg K for an applied field change of 2 T, a value very close to that (∼31 J/kg K) measured in MnAs. For materials with a first order transition at TC, the observed magnetocaloric effect enhancement can be explained by magnetoelastic effects which are due to structural changes. A model based on the phenomenological approach of Bean and Rodbell [Phys. Rev. 126, 104 (1962)] has been developed in order to describe such a behavior. In this paper we apply this model to describe the giant magnetocaloric effect exhibited by Mn1-x(Ti0.5V0.5)xAs (x=0, 0.1) materials. [ABSTRACT FROM AUTHOR]

In this paper we describe the results of a parameter survey of a 16 segmented Halbach cylinder in three dimensions in which the parameters internal radius, rin, external radius, rex, and length, L, have been varied. Optimal values of rex and L were found for a Halbach cylinder with the least possible volume of magnets with a given mean flux density in the cylinder bore. The volume of the cylinder bore could also be significantly increased by only slightly increasing the volume of the magnets, for a fixed mean flux density. Placing additional blocks of magnets on the end faces of the Halbach cylinder also improved the mean flux density in the cylinder bore, especially so for short Halbach cylinders with large rex. Moreover, magnetic cooling as an application for Halbach cylinders was considered. A magnetic cooling quality parameter, Λcool, was introduced and results showed that this parameter was optimal for long Halbach cylinders with small rex. Using the previously mentioned additional blocks of magnets can improve the parameter by as much as 15% as well as improve the homogeneity of the field in the cylinder bore. [ABSTRACT FROM AUTHOR]

• A two-stage adiabatic demagnetization refrigerator is built with GGG as the first stage and CPA as the second stage. • A 3D printed PEEK suspension system is used at the second stage. • A no-load lowest temperature of 66.1 mK is achieved at the second stage when starting from 1 K@4 T. • Simulations estimate each PEEK suspension has a 1.10 μW thermal leak between 4 K and 0.3 K and a further reduction with a 1 K heat sink in the middle. • Experiments validate the effectiveness of 1 K heat sink. The salt pill suspensions play a critical role in determining the performance of adiabatic demagnetization refrigerators (ADR). Kevlar suspensions are commonly used to hold the salt pill in place and to minimize the thermal leak. However, traditional solutions such as tensioning the Kevlar and fixing it on mechanical frame with the help of epoxy or running it around a pulley are quite challenging. This paper presents an innovative suspension using 3D printing technology and a polyether ether ketone (PEEK) multi-ring suspension has been designed and tested. Numerical analysis shows that a single piece of the suspension may contribute about 1.10 μW thermal leak between 4 K and 0.3 K. To test its performance, a two-stage ADR is built with Gadolinium Gallium Garnet (GGG) as the first stage and chromium potassium alum (CPA) salt pill as the second stage which is supported by the PEEK suspension. The GGG stage is mainly used to provide an initial temperature for CPA stage. Typically, starting from 1 K@4 T, a no-load lowest temperature of 66.1 mK is achieved at a demagnetization rate of 0.005 T/s in the experiments. The thermal leak of the PEEK suspension with and without 1 K heat sink has been analyzed and compared, with the former one showing a big reduction of the thermal leak. This paper confirms the feasibility of PEEK as an ADR suspension material and provides a potential 3D printing method for complex suspension designs. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for feature extraction of a new fault indicator focused on detecting demagnetization faults in a surface-mounted permanent-magnet synchronous motors operating under nonstationary conditions. Preprocessing of transient-current signals is performed by applying Choi–Williams distribution to highlight the salient features of this demagnetization fault. In this paper, fractal dimension calculation based on the computation of the box-counting method is performed to extract the optimal features for diagnosis purposes. It must be noted that the applied feature-extraction process is autotuned, so it does not depend on the severity of the fault and is applicable to a wide range of operating conditions of the motor. The performance of the proposed system is validated experimentally. According to the obtained results, the proposed methodology is reliable and feasible for diagnosing demagnetization faults in industrial applications. [ABSTRACT FROM AUTHOR]

The production of a stochastic background of relic gravitational waves is well known in various works in the literature, where, by using the so called adiabatically-amplified zero-point fluctuations process, it has been shown how the standard inflationary scenario for the early universe can in principle provide a distinctive spectrum of relic gravitational waves. In this paper, it is shown that, in general, f( R) theories of gravity produce a third massive polarization of gravitational waves and the primordial production of this polarization is analyzed adapting the adiabatically-amplified zero-point fluctuations process at this case. In this way, previous results, where only particular cases of f( R) theories have been analyzed, will be generalized. The presence of the mass could also have important applications in cosmology, because the fact that gravitational waves can have mass could give a contribution to the dark matter of the Universe. An upper bound for these relic gravitational waves, which arises from the WMAP constrains, is also mentioned. At the end of the paper, the potential detection of such massive gravitational waves using interferometers like Virgo and LIGO is discussed. [ABSTRACT FROM AUTHOR]

This paper discusses the role of media damping for a perpendicular recording system that uses a realistic head field and media parameters in a micromagnetic model based on the Landau-Lifshitz-Gilbert formulation for the magnetization dynamics. The modeling approach uses pulsed write fields of varying pulse duration to record footprints of the head on the media. Using a criterion that 95% of the grains are reversed in the footprints, we calculate the field needed to record as a function of pulse duration, i.e., the dynamic coercivity. As shown in a previous paper, we find two distinct regions in the dynamic coercivity plots. The thermally dominated (long time) region can be described by appropriately including the demagnetization effects in the thermal stability factor Ku V/kBT. The short time (dynamic) behavior shows a precipitous increase in the required recording field accompanied by an increase in the erase width. The latter effect causes the recording performance to degrade, especially in the short time dynamic regime. The onset of dynamic effects strongly depends on the media damping. In order to achieve high data and high areal density, we need to optimize damping in the recording heads and media. [ABSTRACT FROM AUTHOR]

In this paper, we construct a phase-space surface hopping algorithm for use in systems that exhibit strong nonadiabatic coupling. The algorithm is derived from a representation of the electronic basis which is a function of the nuclear phase-space coordinates rather than the nuclear position coordinates. This phase-space adiabatic basis can be understood in the context of Berry’s superadiabatic basis formalism as the first-order superadiabatic correction to the conventional position-space adiabatic basis. This superadiabatic representation leads to nuclear dynamics described not by Newton’s equations of motion but by generalized Hamilton’s equations of motion. The phase-space surface hopping algorithm captures physical effects that cannot be described by traditional algorithms. For a simple model problem, we show that phase-space surface hopping is more accurate than position-space surface hopping, especially when the nonadiabatic coupling is strong. [ABSTRACT FROM AUTHOR]

We present a synergetic experimental/theoretical study of hydrated hexafluorobenzene anions. Experimentally, we measured the anion photoelectron spectra of the anions, C6F6-(H2O)n (n=0–2). The spectra show broad peaks, which shift to successively higher electron binding energies with the addition of each water molecule to the hexafluorobenzene anion. Complementing these results, we also conducted density functional calculations which link adiabatic electron affinities to the optimized geometric structures of the negatively charged species and their neutral counterparts. Neutral hexafluorobenzene-water complexes are not thought to be hydrogen bonded. In the case of C6F6-(H2O)1, however, its water molecule was found to lie in the plane of the hexafluorobenzene anion, bound by two O–H...F ionic hydrogen bonds. Whereas in the case of C6F6-(H2O)2, both water molecules also lie in the plane of and are hydrogen bonded to the hexafluorobenzene anion but on opposite ends. This study and that of Schneider et al. [J. Chem. Phys. 127, 114311 (2007), preceding paper] are in agreement regarding the geometry of C6F6-(H2O)1. [ABSTRACT FROM AUTHOR]

In studying ultrafast electron transfer from a dye molecule to a nanosized semiconductor particle, pump-probe experiments are commonly used. In this system the electron transfer (ET) rate is faster than vibrational relaxation so that the ET rate should be described by a single-level rate constant and the probing signal (often in the form of time-resolved spectra) contains the contribution from the dynamics of both population and coherence (i.e., wave packet). In this paper, we shall present the theoretical treatments for femtosecond time-resolved pump-probe experiment and the dynamics of population and coherence by the density matrix method, and the calculation of single-level ET rate constant involved in a pump-probe experiment. As an application, we show the theoretical results using parameters extracted from experiments on a specific dye/semiconductor system. [ABSTRACT FROM AUTHOR]

Dilution and adiabatic demagnetization refrigerators based on pulse tube cryocoolers are nowadays used in many low temperature physics experiments, such as atomic force and scanning tunneling microscopy, quantum computing, radiation detectors, and many others. A pulse tube refrigerator greatly simplifies the laboratory activities being a cryogen-free system. The major disadvantage of a pulse tube cooler is the high level of mechanical vibrations at the warm and cold interfaces that could substantially affect the performance of very sensitive cryogenic instruments. In this paper, we describe the performance of a very simple mechanical attenuation system used to eliminate the pulse-tube-induced low frequency noise of the superconducting transition-edge sensors under development for the instruments of the next generation of infra-red and X-ray space observatories. [ABSTRACT FROM AUTHOR]

In this paper, we study behavior of the correlations, both quantum and classical, under adiabatic demagnetization process in systems of nuclear spins with dipole–dipole interactions in an external magnetic field and in the temperature range including positive and negative temperatures. For a two-spin system, analytical expressions for the quantum and classical correlations are obtained. It is revealed that the field dependences of the quantum and classical correlations at positive and negative temperatures are substantially different. This difference most clearly appears in the case of zero magnetic field: at negative temperature, the measures of quantum correlations tend to the maximum values with a temperature increase. At positive temperature, these quantities tend to zero at a decrease of magnetic field. It is also found that, for the nearest-neighboring spins in the same field, the values of concurrence and discord are larger at negative temperatures than at positive ones. [ABSTRACT FROM AUTHOR]

The traditional method for producing polymer-based products is the use of moulding technologies such as injection moulding. CNC machining methods are predominantly used for metal part manufacture. The use of CNC machining methods for direct machining of polymers has been discussed in previous studies, particularly for hard polymers such as polypropylene. The CNC machining of soft elastomers, such as ethylene vinyl acetate (EVA), even at significantly reduced temperatures presents a number of challenges, with one being the formation of a machining phenomenon termed adiabatic shear bands, which can lead to increased part surface roughness and reduced part quality. The adiabatic shear band is an area on a chip where the ductile properties of the material being machined have been exceeded and the heat generated does not have sufficient time to be removed. This can lead to permanent material damage resulting in reduced fatigue resistance. The adiabatic shear formation has the potential to be even more evident with the machining of elastomers, leading to rapid material degradation, poor surface finish characteristics, and reduced material attenuation. In this paper the state of the art in cryogenic manufacturing is described and the concept of cryogenic CNC machining of elastomers is discussed. The experimental work consists of machining EVA and Neoprene utilizing the described cryogenic CNC machining facility. Sample chips are taken from the experimental testing and analysed using a scanning electron microscope to illustrate the adiabatic shear band formation in some cases. It is observed that in order to reduce this effect, correct machining parameters corresponding to the elasticity values need to be used and the glass transition temperature needs to be maintained. [ABSTRACT FROM PUBLISHER]

Although interior permanent magnet synchronous machines and their cooling are designed to match the rated power, power demands other than rated may arise. One may keep the same machine dimensions and basic electromagnetic design, but increase the cooling for different operating conditions. Modifications of the cooling system can compensate for the increase in machine losses in the windings, magnets, or iron. Increasing the allowed stator current affects the machine performance in other ways as well. These include demagnetization of the magnets, and hence, shrinking of the speed range to avoid this. In this paper, these effects are studied for a baseline machine, as well as for machines with the same stator but modified rotor design. A cross-saturated model is developed and shown to be more accurate than the classic one. To account for higher stator current with higher temperatures, the effects on efficiency, torque, and speed range by changing the magnet material from the more commonly used NdFeB to SmCo are also studied and discussed. [ABSTRACT FROM AUTHOR]

Flux-reversal machine (FRM) is a new doubly salient stator-permanent magnet (PM) machine with flux linkage reversal in the stator concentrated windings. It can operate in both motoring and generating modes. Its simple structure makes it cost effective and suitable for mass production. However, there is notable permanent magnet flux leakage which deteriorates the torque ability of the FRM. In this paper, a novel design to improve the performance of an FRM is proposed. The proposed FRM has permanent magnets parallel to the stator magnet flux lines and thus is much more difficult to demagnetize. To analyze the characteristics of the proposed FRM, a two-dimensional finite-element method (2-D FEM) is used. The prototype FRM is also built to prove the advantage of the new design method. From the analysis and experimental results, it is shown that the proposed FRM has an improved performance. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present a new model for the demagnetization problem in a permanent magnet machine having a reversed structure. The permeance network approach and superposition theorem have been used to check out the semi-analytical model. In order to validate the model, a two-dimensional finite element method analysis has been carried out. The obtained results are encouraging to continue the modeling process and this will open several prospects particularly in the diagnostics areas of the permanent magnet machines. [ABSTRACT FROM AUTHOR]

In this paper we study the magnetocaloric effect in transition metals based compounds. For this purpose, we use a microscopical model, based on the band theory of magnetism, where the magnetic lattice is coupled with the crystalline lattice and with the external magnetic field. We apply the model to calculate the magnetocaloric effect in the compound MnAs, which undergoes a first order magnetic phase transition. The theoretically calculated isothermal entropy changes and the adiabatic temperature changes upon magnetic field variation exhibit a good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

We consider the solitary wave solutions of a Korteweg–de Vries equation, where the coefficients in the equation vary with time over a certain region. When these coefficients vary rapidly compared with the solitary wave, then it is well known that the solitary wave may fission into two or more solitary waves. On the other hand, when these coefficients vary slowly, the solitary wave deforms adiabatically with the production of a trailing shelf. In this paper we re-examine this latter case, and show that the trailing shelf, on a very long time-scale, can lead to the generation of small secondary solitary waves. This result thus provides a connection between the adiabatic deformation regime and the fission regime. [ABSTRACT FROM AUTHOR]

Titanium alloys (Ti6Al4V) have been widely applied in modern aerospace industry as structural components due to their excellent mechanical and physical properties. Meanwhile, the drilling process is essential for machining the assembly holes of Ti6Al4V. However, Ti6Al4V is also a difficult-to-cut material owing to their low thermal conductivity and high chemical reactivity with many tool materials during machining, which easily lead to rapid tool wear, premature tool failure, and poor machining quality. This has attracted wide attention of researchers. In recent years, the rotary ultrasonic-assisted drilling (RUAD) technology, as a novel machining method, has been found to be very effective in the machining of difficult-to-cut materials like nickel alloys and titanium alloys. This paper first introduced an 8-facet drill tool and combined the advantages of RUAD to carry out a study on the drilling of Ti6Al4V under no cooling condition. The experimental results indicated that compared with the common drilling (CD) of Ti6Al4V, in RUAD process with the vibration amplitude of 10 μm, the thrust force, torque, cutting temperature near the drilled hole exit, surface roughness of drilled hole, expansion increment of hole diameter, and burr height of drilled hole exit decreased by 16.79 to 20.2 %, 31.5 to 33.6 %, 18.54 to 21.68 %, 24.87 to 25.36 %, 46.75 to 57.63 %, and 82.27 to 89.18 %, respectively; the excellent chip breakability and removal effect of chip evacuation, superior surface integrity of drilled hole, enhanced tool cutting ability, and prolonged tool life were obtained in RUAD. Furthermore, the experimental results also proved that the drilling technology of RUAD of Ti6Al4V using the 8-facet drill was feasible and the cutting effects were superior. [ABSTRACT FROM AUTHOR]

• A low-cost copper-foam based salt pill is designed and manufactured. • A test from 4.3 K @ 4 T with a demagnetization rate of 0.0025 T/s leads to a no-load temperature of 176.5 mK. • Eddy current loss may be an issue with a high demagnetization rate. • Selection of the copper form parameters needs more investigation. Hydrated paramagnetic salt pills are important components in an adiabatic demagnetization refrigerator (ADR) for temperatures below 500 mK. To improve the heat transfer performance between salt crystals and external thermal links, thermal buses are commonly employed inside the salt pill. Common forms of thermal buses are either thin copper pillars made from electric discharge machining (EDM) or wire bundles, both of which generally involve considerable machining or labor. This paper introduces a novel design and fabrication of a simple foam copper-based paramagnetic salt pill. The foam copper has 30 pores per inch (PPI), a porosity of 98 %, 0.005 m2/g specific surface area, and an estimated pore diameter of 0.82 mm. The complete design, assembling process, and growth of the foam copper-based chromium potassium alum (CPA) salt pill (40 mm in length and 23 mm in diameter) are introduced. A single-stage ADR is built based on this salt pill to test its performance, while another salt pill with the wire thermal bus has also been tested for comparison. A typical cool-down from 4.3 K @ 4 T with a demagnetization rate of 0.0025 T/s led to a no-load temperature of 176.5 mK, slightly better than that using a wire thermal bus. In terms of cooling power per gram of salt, the cooling capacities at 600 mK of both salt pills have also been measured and both have shown similar performance. This preliminary study has shown the potential of the foam copper-based salt pill though more research is required to optimize its performance. [ABSTRACT FROM AUTHOR]

The evolution of the elastic moduli (Young modulus-E; adiabatic bulk modulus-BS and shear modulus-G and Poisson’s ratio-ν) in the temperature range T∈[300;1000] K or T/Tm∈[0.2;0.65] of isotropic polycrystalline beryllium samples was investigated using an ultrasonic method. The key point is to perform the relevant and consistent analysis of the complete set of elastic data taking account of the specific low values of ν (at ambient and at high temperature). The evolution of the elastic moduli is shown to be governed by the density evolution through the thermal expansion coefficient. Then, the elastic moduli versus temperature are accurately discussed and are at variance with the only known experimental data from 1972 [W. D. Rowland, J. Phys. F: Met. Phys. 2, 231 (1972)]. The analysis is completed by a comparison with computations performed by first-principle calculations [G. Robert et al. (unpublished)]. [ABSTRACT FROM AUTHOR]

In this paper we present a new measurement setup, where a transition-edge sensor detector array is used to detect X-rays in particle induced X-ray emission (PIXE) measurements with a 2 MeV proton beam. Transition-edge sensors offer orders of magnitude improvement in energy resolution compared to conventional silicon or germanium detectors, making it possible to recognize spectral lines in materials analysis that have previously been impossible to resolve, and to get chemical information from the elements. Our sensors are cooled to the operation temperature ( $$\sim $$ 65 mK) with a cryogen-free adiabatic demagnetization refrigerator, which houses a specially designed X-ray snout that has a vacuum tight window to couple in the radiation. For the best pixel, the measured instrumental energy resolution was 3.06 eV full width at half maximum at 5.9 keV. We discuss the current status of the project, benefits of transition-edge sensors when used in PIXE spectroscopy, and the results from the first measurements. [ABSTRACT FROM AUTHOR]

Heat switches are key elements in the cyclic operation of Adiabatic Demagnetization Refrigerators (ADRs). Several of the types of heat switches that have been used for ADRs are described in this paper. Key elements in selection and design of these switches include not only ON/OFF switching ratio, but also method of actuation, size, weight, and structural soundness. Some of the trade-off are detailed in this paper. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report some practical aspects concerning the application of La(Fe, Co)13−x Si x based materials in the magnetic cooling technology. For this purpose, two blocks of La(Fe, Co)13−x Si x with different Curie temperature were considered for this study. Before implementing the new refrigerants in the magnetic cooling machine, we have measured directly their magnetocaloric properties in practical conditions around room temperature. The obtained magnetocaloric effect values were corrected taking into account the demagnetization effect. The influence of the demagnetization field on the magnetocaloric performances of La(Fe, Co)13−x Si x is analyzed and discussed. A composite material based on La(Fe, Co)13−x Si x compounds was tested directly in our recently developed magnetic cooling system and a comparison with the gadolinium was made. Encouraging results were obtained showing the high potential of the studied materials in magnetic cooling application. In addition, the poor corrosion resistance of the intermetallics can compromise the potential of these materials. In this paper, we also present the corrosion tests performed on different samples of La(Fe, Co)13−x Si x using several heat transfer fluids. [Copyright &y& Elsevier]

The present paper proposes an analytical magnetic charges equivalence procedure for computing the magnetic field created by the lifting magnets in a non-vertical levitation structure. The proposed method avoids the repetitive solving of the problem needed by any numerical analyse package in order to reach the balance of forces at the equilibrium point. Demagnetization in open-loop of the used NdFeB magnets is taken into account by determining their operating point on the BH-curve. The equilibrium point location is calculated and its stability is checked through the stability discriminants. Several horizontal and an inclined structures are computed and the results are compared with the ones obtained with the professional field computation package RADIA. Finally, the calculation results are validated in comparison with experimental results. [ABSTRACT FROM AUTHOR]

Highlights • The mechanism of multi-bypass was numerical studied. • Multi-bypass has the functions of orifice and double-inlet, making it like two-stage cryocooler. • A minimum no-load temperature 3.7 K was obtained, and the cooling power was 14 mW@4.2 K. • New mK cooling chain for HUBS satellite was proposed and analyzed. Abstract The Vuilleumier (VM) type pulse tube cryocooler (VPTC) is a new kind of 4 K cryocooler which had been experimentally verified. This paper presents the recent advances on a 4 K VPTC in our laboratory. First, the mechanism of multi-bypass was numerically studied using Sage software. The results showed that the function of the multi-bypass is not only similar to a double-inlet, but also to an orifice, which makes the VPTC work like a two-stage cryocooler. Based on the simulation results, the performance of VPTC was experimentally studied. Under its optimal operating conditions, a no-load temperature of 3.7 K has been obtained, which is the first demonstration of a single-stage VPTC obtaining temperatures below 4 K. It can supply about 14mW cooling power at 4.2 K and about 100 mW cooling power at 35 K simultaneously, which has potential application as the pre-cooler for an adiabatic demagnetization refrigerator (ADR). Finally, based on this VPTC, a new mK cooling chain for HUBS (Hot Universe Baryon Surveyor) satellite is proposed and its prospect has also been theoretically analyzed. [ABSTRACT FROM AUTHOR]

This paper proposes an automatic test bench, based on a rigorous and repeatable measurement procedure, for the analysis of a position sensor linear variable differential transformer (LVDT). The test bench allows complete characterization of an LVDT sensor working in an interfering magnetic field by evaluating the uncertainty and nonlinearity of the sensor. This issue is addressed in neither the sensor datasheet nor the scientific literature. The potential of the method and the performance of the automated test bench are proven by measuring the main sensor characteristics such as nonlinearity and uncertainty, and the error of a position reading due to external magnetic interference on two commercial LVDTs. The sensors are based on two different reading techniques, and both are analyzed using current and voltage excitations. In fact, the test bench permits to study the robustness of the sensor with respect to external magnetic fields by comparing position drifts due to interference at varying source excitations and reading techniques. [ABSTRACT FROM AUTHOR]

In this paper, the effects of Prandtl number on the steady magneto-convection around a centrally located adiabatic body inside a square enclosure are numerically investigated. Two-dimensional nonlinear governing equations are discretized using the control volume method and hybrid scheme. The equations are solved using SIMPLER algorithm. The results are displayed in the form of streamlines and isotherms when the Rayleigh number varies between 10 and 10, the Hartmann number changes between 0 and 100 and the Prandtl number ranges between 0.005 and 0.1. The ratio of the buoyancy force to the Lorentz force ( Ra/ Ha) is introduced as an index to compare the contribution of natural convection and magnetic field strength on heat transfer. The results obtained from numerical modeling show that the Prandtl number has not considerable effect on heat transfer at low Rayleigh numbers. The effect of magnetic field strength on convection is increased by increasing Prandtl number. The effect of Prandtl number on the average Nusselt number in the presence of a magnetic field is less than the case without a magnetic field. [ABSTRACT FROM AUTHOR]

A two-dimensional quench simulation model was developed for the Superconducting Electromagnetic Iron Separator (SEIS) system, which is designed to separate small pieces of ferromagnetic materials, such as detonators, from coal to achieve high purity and good yield. The SEIS coil adopted passive quench protection system with four-sectioned arrangement, each shunted with four diodes. The aluminum slices, with 99.99% purity and 0.5 mm x 12 mm cross section dimension, working as quench propagator, were clothed on the inner and the outer surfaces of the coil. The minimum quench energy, the temporal variations of current, voltage and hot spot temperature rise of the coil were analysed. Furthermore, the coil stress during winding, cool-down, charging and quench process was also included in this paper. The simulation results demonstrated that the existing protection system could guarantee the SEIS magnet experience no fatal damage during quench. [ABSTRACT FROM AUTHOR]

The paper describes how Born-Oppenheimer breakdown parameters for the rotational constants of diatomic molecules can be determined via quantum-chemical computations. The deviations from the Born-Oppenheimer equilibrium values are accounted for by considering the adiabatic correction to the equilibrium bond distances, the electronic contribution to the rotational constant via the rotational g tensor, and the so-called Dunham correction, which can be computed directly from a polynomial expansion of the potential curve around the equilibrium distance. Calculations for HCl, SiS, and HF demonstrate the accuracy that can be achieved in the theoretical treatment of the considered Born-Oppenheimer breakdown parameters and the usefulness of such calculations is illustrated for highly accurate spectroscopic measurements in the field of rotational spectroscopy. [ABSTRACT FROM AUTHOR]

The paper treats recent experiments measuring the endpoint region of tritium β-decay with high resolution, sensitivity and background rejection, using an electrostatic filter with adiabatic magnetic collimation. The spectra are analysed with respect to the neutrino mass. These results form the primary source for the present upper limit of the neutrino mass mv < 2 eV quoted by the particle data group. Particular attention is paid to the decisive influence which atomic and molecular physics effects take on the results. A brief outlook on future experiments is given. [ABSTRACT FROM AUTHOR]

For a permanent magnet dipole to produce fields higher than the remnant induction of the magnetic materials, Halbach and Stelter array are commonly used structures. This paper presents a novel design for strong field permanent magnet dipole. We analyzed the structure using current sheet method. We then used BEA software to simulate the structure. A prototype dipole was built. The field from the prototype dipole was measured and compared to the analytical and BEA results. The actual field matches the calculation very well. There is no visible demagnetizing effect. [ABSTRACT FROM AUTHOR]

Gd5Si2Ge2 is known for its giant magnetocaloric effect (GMCE), but also for its associated large hysteretic losses. These losses result in a significant reduction in the net cooling capacity of this material when it is used for magnetic cooling. Attempts have been made to reduce these losses by adding other elements, like iron. Individual Ge and Si substitutions have been reported, but in this paper we focus on the system where both elements were substituted simultaneously with different amounts of Fe, with an additional interest in the new Gd5 (Si,Ge)3 phase that appears after the substitution. We found that when substituting iron in small quantities the MCE and the hysteresis losses remain high, with a small decrease in the Curie temperature, and the low-temperature XRD revealed that the structural transformation is still present. However, with an increasing amount of Fe the MCE was drastically reduced because of the newly formed Gd5 (Si,Ge)3 phase. The magnetic transition temperature of this newly formed phase was investigated in all three substituted systems: Si, Ge and Si and Ge. This transition temperature was strongly affected by the type and the amount of substitution; however, the changes could not be directly related to the composition of the phases. [ABSTRACT FROM AUTHOR]

In many space sciences project cryogenic detectors are essential for the accomplishment of the scientific objectives, offering unique advantages and unmatched performance. In addition several other components such as the optics can benefit from a cryogenic cooling which reduces the radiative loading. The Service des Basses Températures (SBT) of CEA Grenoble has been involved in space cryogenics for over 20 years now and features a dedicated laboratory, the Cryocoolers and Space Cryogenics group. Various cryocoolers have been developed in the past and our fields of activity focus now on four main technologies: sorption coolers, multistage pulse tubes, adiabatic demagnetization refrigerators (ADR), and cryogenic loop heat pipes. In addition work on two new concepts for ground based dilution refrigerators is also ongoing. Finally developments on various key technologies such as the heat switches, the suspension or structural systems are also carried out. These developments are mainly funded by the European Space Agency (ESA) or by the Centre National d'Études Spatiales (CNES). In this paper we mostly give an overview of the developments carried out at SBT along with several examples of other relevant systems. We use space cryogenics as a thread. However these coolers or techniques can be used on ground, particularly on remote locations where liquid cryogen are unavailable and/or where maintenance must be limited to a strict minimum. In this case they can be simplified and take advantage of on ground resources, and their cost can be significantly reduced. For most of these systems the common feature is the absence of any moving parts or any friction, which guarantees a very good reliability and make them very good candidates for space borne instruments requiring cryogenic temperatures. [ABSTRACT FROM AUTHOR]

In view of the second law of thermodynamics, the idealized process is usually so selected as to be one of minimum available energy degradation. A measure of departure from this ideal process is the entropy generation rate. In this paper, we shall investigate this aspect concerning an adiabatic peristaltic pump. Our analysis also exhibits the general features of a flow in a contracting tube. It is shown that the dynamics of the system can be reduced to that of a classical Hagen-Poiseuille flow with a source term in the continuity equation and an additional induced force in the momentum equation. In reference to exergy, the analysis reveals that peristaltic pumps generate more entropy than steady walled tubes and are not, from this point of view, competitive devices. The reason for this high-energy degradation is found in the dynamic behavior. The flow rate is not constant along the tube, but increases as sections downstream are reached. This results in high velocity gradients and therefore in strong dynamic irreversibility, which is the prime entropy source of the system. For the classical Hagen–Poiseuille flow, the entropy is mainly generated by heat diffusion. [ABSTRACT FROM AUTHOR]

Abstract  In this paper, unsteady heat transfer and fluid flow characteristics in an enclosure are investigated. The enclosure consists of two vertical wavy and two horizontal straight walls. The top and the bottom walls are considered adiabatic. Two wavy walls are kept isothermal and their boundaries are approximated by a cosine function. Governing equations including continuity, momentum and energy were discretized using the finite-volume method and solved by SIMPLE method in curvilinear coordinate. Simulation was carried out for a range of Grashof number Gr = 103–106, Prandtl number Pr = 0.5–4.0, wave ratio A (defined by amplitude/wavelength) 0.0–0.35 and aspect ratio W (defined by average width/wavelength) 0.5–1.0. Streamlines and isothermal lines are presented to corresponding flow and thermal fields. Local and average Nusselt number distributions are presented. The obtained results are in good agreement with available numerical and experimental data. [ABSTRACT FROM AUTHOR]

In the stably stratified interior of the ocean, mesoscale eddies transport materials by quasi-adiabatic isopycnal stirring. Resolving or parameterizing these effects is important for modeling the oceanic general circulation and climate. Near the bottom and near the surface, however, microscale boundary layer turbulence overcomes the adiabatic, isopycnal constraints for the mesoscale transport. In this paper a formalism is presented for representing this transition from adiabatic, isopycnally oriented mesoscale fluxes in the interior to the diabatic, along-boundary mesoscale fluxes near the boundaries. A simple parameterization form is proposed that illustrates its consequences in an idealized flow. The transition is not confined to the turbulent boundary layers, but extends into the partially diabatic transition layers on their interiorward edge. A transition layer occurs because of the mesoscale variability in the boundary layer and the associated mesoscale–microscale dynamical coupling. [ABSTRACT FROM AUTHOR]

Abstract-The MICE focusing solenoids have three 4 K coolers (two for the superconducting magnet and one for the liquid absorber) and four HTS leads that feed the current to the focusing coils. The focusing solenoids produce large radial external fields when they operate with the polarity of the two coils in opposition (the gradient or flip mode). When the MICE focusing coils operate at the same polarity (the solenoid or non-flip mode), the fields are much smaller and parallel to the axis of the solenoid. The worst-case magnetic field affects the selection of the cooler and the HTS leads. This magnetic field can also determine the height of the service towers that house the three coolers and the four HTS leads. This paper shows the criteria used for Cooler selection, HTS lead selection, and the position of both the cooler and leads with respect to the solenoid axis of rotation. [ABSTRACT FROM AUTHOR]

This paper presents the results of work, experimental and simulation, performed on an YBCO pancake coil to develop a detect-and-activate-the-heater (DAH) protection technique. In this DAH protection technique a "protection heater" (PH) is activated, upon the detection of a quench zone in a coil, to create an additional normal zone to absorb the stored magnetic energy sufficient to keep the initially quenched zone (hot spot) from overheating. It is computed that a protection heater for most coils needs to cover only a fraction of the winding to keep the quenched zone from overheating. The pancake coil used in the experiment, 100-mm i.d., 190-mm 04., and 4.3-mm height, is dry-wound with copper plated YBCO tape, 4.3-mm wide, 96.3-μm thick, 100-m long, and is turn-to-turn insulated with 38-μm thick Nomex spacer. The pancake stores a magnetic energy of 30 J at an operating current of 80 A at 65 K. Because the smaller the magnet size, the less applicable the assumption of adiabatic conditions is and also the more beneficial NZP becomes that would otherwise be negligible in "large" magnets, the hot spot temperature observed in the experiment with this "small" test coil was much less than that computed based on the assumptions of adiabatic conditions and no NZP. To validate the basic concept and consequences of DAH protection technique either a test coil has to be large or if the same coil is to be used, it should be tested at the temperature range close to 20-30 K so that the coil can carry a large current and thus store a large magnetic energy. [ABSTRACT FROM AUTHOR]

Abstract   The development of adiabatic demagnetization refrigerators (ADR) over the last decade has resulted in significant improvements in performance and ease of use, including continuous operation, relatively high cooling power (30–35 μW at 100 mK), and cryogen-free operation. ADR systems are small, efficient, and require no auxiliary pumps or gas-handling systems. Consequently they are compact, convenient, low-cost options for ground-based research and instrument development. This paper presents an assessment of state-of-the-art ADRs in terms of temperature and cooling power capabilities, with emphasis on their applicability to quantum fluids and solids research. [ABSTRACT FROM AUTHOR]

This paper presents the mathematical analysis of a single stage absorption cycle using heat rejected from thermoelectric modules to drive the cycle. The absorption cycle uses LiBr/H2 O solution as the working pair with thermoelectric modules sandwiched between the generator and absorber. The results of the analysis show that thermoelectric modules would provide the heat required to drive the absorption cycle and the overall coefficient of performance (COP) of the integrated system could be higher than unity. [ABSTRACT FROM AUTHOR]

Abstract: The noise-flatness-induced hypersensitive transport of overdamped Brownian particles in a tilted periodic sawtooth potential driven by a multiplicative nonequilibrium three-level noise and additive white noise is considered. The study is a follow-up of one of our earlier papers on trichotomous-noise-induced hypersensitive transport [Mankin et al., Phys. Rev. E 68 (2003) 011105]. In the current paper the exact formula for the stationary current is presented. All the physical results discussed are computed by means of the exact formula. It is demonstrated that (i) at low temperatures the enhancement of current is hypersensitive to the applied small static tilting force, (ii) the stationary macroscopic current has a bell-shaped dependence on the parameters, correlation time and flatness, of multiplicative noise which occurs even in the case of large (compared to the ultrasmall DC signal) additive thermal noise, and (iii) at low temperatures and small values of the switching rate, the differential mobility as a function of the tilting force has local minima in a finite range of the force. Implications of the case of multiplicative trichotomous noise are compared with the results of a deterministic square-wave stimulus. [Copyright &y& Elsevier]

The ATLAS B0 model coil has been extensively tested, reproducing the operational conditions of the final ATLAS Barrel Toroid coils [1]. Two test campaigns have taken place on B0, at the CERN facility where the individual BT coils are about to be tested. The first campaign aimed to test the cool-down, warm-up phases and to commission the coil up to its nominal current of 20.5 kA, reproducing Lorentz forces similar to the ones on the BT coil. The second campaign aimed to evaluate the margins above the nominal conditions. The B0 was tested up to 24 kA and specific tests were performed to assess: the coil temperature margin with respect to the design value, the performance of the double pancake internal joints, static and dynamic heat loads, behavior of the coil under quench conditions. The paper reviews the overall test program with emphasis on second campaign results not covered before. [ABSTRACT FROM AUTHOR]

ASTRO-H was an X-ray astronomy satellite that the Japan Aerospace Exploration Agency (JAXA) developed to study the evolution of the universe and physical phenomena yet to be discovered. The primary scientific instrument of ASTRO-H was the Soft X-ray Spectrometer (SXS). Its detectors were to be cooled to 50 m K using a complex cryogenic system with a multistage adiabatic demagnetization refrigerator (ADR) developed by the National Aeronautics and Space Administration (NASA), and a cryogenic system developed by Sumitomo Heavy Industries, Ltd. (SHI). SHI’s cryogenic system was required to cool the ADR’s heatsink to 1.3 K or less in orbit for three years or longer. To meet these requirements, SHI developed a hybrid cryogenic system consisting of a liquid helium tank, a 4 K Joule-Thomson cooler, and two two-stage Stirling coolers. ASTRO-H was launched from Tanegashima Space Center on February 17, 2016. The initial operation of the SXS cryogenic system in orbit was completed successfully. The cooling performance was as expected and could have exceeded the lifetime requirement of three years. This paper describes results of ground tests, results of top-off filling of superfluid liquid helium just before launch, and cooling performance in orbit. [ABSTRACT FROM AUTHOR]

Reducing the contribution of all sources of microwave loss is important for increasing coherence times in superconducting qubits. In this paper we investigate reducing the loss by systematically removing Si substrate material from the gap region in titanium nitride coplanar waveguides fabricated on intrinsic Si substrates. By exploiting the radial dependence of the etch rate in a parallel plate reactive ion etcher, otherwise identical coplanar waveguides with only the Si gaps etched to varying depth, i.e., trenched, were created in a single TiN film within a single processing step. Measurements at these multiple depths permit the study of the loss reduction in isolation to the unintentional effects caused by any single processing step. When comparing the loss from all trench depths we found that the high power loss was similar, but in the single photon limit the loss was reduced by a factor of two for deeper trenches in agreement with predictions from finite element analysis. [ABSTRACT FROM AUTHOR]