Cryogenic Temperature Range Research Articles

Comprehensive Assessment of Avalanche Operating Boundary of SiC Planar/Trench MOSFET in Cryogenic Applications

The avalanche ruggedness of power devices becomes a crucial issue to ensure the safe operation of the power conversion systems, particularly under the extreme temperature conditions. In this article, the avalanche capability of SiC planar/trench MOSFETs is systematically evaluated and analyzed over the temperature range of 90 to 340 K. Importantly, the essential mechanisms and temperature dependence of avalanche failure under cryogenic conditions are further explored by combining many analysis methods such as TCAD simulations, the unclamped inductive switching characterizations, and the transient junction temperature prediction. The highest avalanche energy density of 171.24 mJ/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 90K indicates the great application potential of SiC plannar mosfet in cryogenic electronics. Moreover, the safe avalanche operation boundary (AOB) model is established over the cryogenic temperature range. The relevant analysis method and AOB model can be used to accurately evaluate and quantitatively predict the avalanche capability of SiC planar/trench mosfets for the cryogenic converter design.

Experimental study on operating characteristics of a cryogenic loop heat pipe without additional power consumption

The infrared sensors/detectors in the space infrared detection system are required to be cooled down to a cryogenic temperature range. Cryogenic loop heat pipes (CLHPs) are promising thermal management devices, which could isolate the mechanical vibration and electromagnetic interference from cryocoolers. However, the traditional CLHPs require additional power consumption during the cooling down or even normal operation, which add more burden of cryocoolers. An innovative CLHP with a flexible wick was described in this paper, which could transport cryogenic liquid by capillary effect. Additional power consumption is not required at all for this CLHP during the cooling down and normal operation. In this paper, the cooling down characteristic and operating performance of the CLHP with nitrogen as working fluid were experimentally investigated in detail. The maximum heat transport capacity of the CLHP with 1.31 MPa filling pressure was experimentally examined, which achieved 28 W over a 0.5 m distance. With the increase of filling pressures from 0.42 MPa to 1.28 MPa, the CLHP could realize cooling down process successfully and the total cooling down time decreased significantly from 245 min to 137 min. The CLHP could operate stably with the filling pressure from 1.1 MPa to 1.31 MPa. A minimum thermal resistance of 0.43 K/W was obtained corresponding to 1.1 MPa filling pressure. The CLHP failed to work with a low filling pressure of 0.85 MPa or 1.0 MPa. In addition, the performance optimization of the CLHP was analyzed and experimentally validated.

Utilization of grey Taguchi method to optimize the mechanical properties of hemp and coconut shell powder hybrid composites under liquid nitrogen conditions

Through this work an attempt was made to improve the mechanical properties of composite materials by using a process called Gray-Taguchi. Hand lay-up approach has been adopted for manufacturing. Here, Woven Hemp fiber diameter, Number of hemp layer, coconut shell powder content and cryogenic temperature ranges at different levels were incorporated as result parameter. ASTM specifications were set for the manufactured laminates to perform the mechanical tests. Hemp and coconut shell powder material are exposed to 5 percent NaOH treatment to create the matrix-fiber interface exchange. To optimize composite, the Taguchi method is combined with the Gray relational analysis. The quality targets are set for mechanical properties that include compressive strength, tensile strength, impact strength and flexural strength. This study involved nine experiments on the orthogonal array of the L9 (34) Taguchi method. A combination of the composite, Gray relational analysis was applied to obtain the optimal parameter. The results of optimum parameters were verified using Conformation test. The maximum prescribed parameters are 0.7 mm woven hemp diameter, two hemp layers, 10 percent CSP content weight, and -130°C cryogenic temperature range provides the maximum energy of impact, tensile strength and flexural strength.

Engineering the magnetocaloric properties of PrVO3 epitaxial oxide thin films by strain effects

Combining multiple degrees of freedom in strongly correlated materials such as transition-metal oxides would lead to fascinating magnetic and magnetocaloric features. Herein, the strain effects are used to markedly tailor the magnetic and magnetocaloric properties of PrVO3 thin films. The selection of an appropriate thickness and substrate enables us to dramatically decrease the coercive magnetic field from 2.4 T previously observed in sintered PVO3 bulk to 0.05 T for compressive thin films making from the PrVO3 compound a nearly soft magnet. This is associated with a marked enhancement of the magnetic moment and the magnetocaloric effect that reaches unusual maximum values of roughly 4.86 μB and 56.8 J/kg K with the magnetic field change of 6 T applied in the sample plane in the cryogenic temperature range (3 K), respectively. This work strongly suggests that taking advantage of different degrees of freedom and the exploitation of multiple instabilities in a nanoscale regime is a promising strategy for unveiling unexpected phases accompanied by a large magnetocaloric effect in oxides.

Pushing the Limit of Boltzmann Distribution in Cr3+-Doped CaHfO3 for Cryogenic Thermometry.

Luminescence Boltzmann thermometry is one of the most reliable techniques used to locally probe temperature in a contactless mode. However, to date, there is no report on cryogenic thermometers based on the highly sensitive and reliable Boltzmann-based 4T2 → 4A2/2E → 4A2 emission ratio of Cr3+. On the basis of structural information of the local HfO6 octahedral site we demonstrated the potential of the CaHfO3:Cr3+ system by combining deep theoretical and experimental investigation. The material exhibits simultaneous emission from both the 2E and 4T2 excited states, following the Boltzmann law in a cryogenic temperature range of 40-150 K. The promising thermometric performance corroborates the potential of CaHfO3:Cr3+ as a Boltzmann cryothermometer, being characterized by a high relative sensitivity (∼ 2%·K-1 at 40 K) and exceptional thermal resolution (0.045-0.77 K in the 40-150 K range). Moreover, by exploiting the flexibility of the 4T2-2E energy gap controlled by the crystal field of the local octahedral site, the design proposed herein could be expanded to develop new Cr3+-doped cryogenic thermometers.

Study on the tribological properties of a self-lubricating spherical plain bearing at a cryogenic and wide temperature range

Study on the tribological properties of a self-lubricating spherical plain bearing at a cryogenic and wide temperature range

Compact Si JFET model for cryogenic temperature

Compact Si JFET model for SPICE circuit simulation in the extended temperature range from 373 K down to 73 K (+100 °C…−200 °C) is proposed. It is based on the standard JFET model Level = 3 (Statz model) with the full set of temperature-dependent parameters in the cryogenic temperature range. The universal procedure for model parameter extraction from I-V-characteristic measurement data at low temperature is developed. The simulation error does not exceed 10–15% in the temperature range 373 K…73 K. The JFET Low-T model is implemented in the form of a subcircuit and tested in popular SPICE-like circuit simulators: HSPICE, LTSpice, ADS, and OrCAD.

Design and fabrication of a cryogenic magnetocaloric composite by spark plasma sintering based on the RAl2 laves phases (R = Ho, Er)

We report the design and fabrication of a highly dense (>97%) two-phase magnetocaloric composite operating in the cryogenic temperature range based on the binary Laves phases HoAl2 and ErAl2 with a nearly table-like magnetic entropy change curve ΔSM(T) at 2 T. Such particular ΔSM(T) dependence was obtained, from the individual ΔSM(T) curves of the precursors, for the composition 28 wt% (ErAl2) + 72 wt% (HoAl2). This composition was selected to make a composite by spark plasma sintering from homogeneously mixed melt-spun ribbons of both intermetallic compounds. The calculated and experimental ΔSM(T) curves obtained for the as-sintered composite were found to be similar. Our results highlight the potential of this processing metallurgical technique for producing two-phase active magnetic regenerators with a designed entropy change curve for specific magnetic refrigeration applications.

Fabrication and Characterization of a Novel Si Line Tunneling TFET With High Drive Current

In this paper, an N-type silicon line tunneling TFET (LT-TFET) with an ultra-shallow N + pocket was proposed. The pocket was formed by using the germanium preamorphization implantation (Ge PAI), arsenic ultra-low energy implantation and spike annealing. Due to the Ge PAI, the tunneling probability was improved significantly. As a result, a high on-state current of 40 μA/μm, a minimum subthreshold swing (SS) of 69 mV/decade and an average SS of 80 mV/decade over 5 decades of drain current were achieved with V DS = V GS = 1 V at room temperature. It is shown that once the trap assisted tunneling is suppressed at the low temperature, the band-to-band tunneling becomes dominant. When the temperature decreases from 300 K to 4.9 K, the on-state current only reduces 20% and a minimumpoint SS of 10 mV/decade was obtained. The LT-TFET exhibits improved transconductance efficiency at deep cryogenic temperature range. The proposed structure in this work shows attractive merits in the cryogenic digital and analog application.

Numerical Simulation on the Effects of Component Layout Orientation on the Performance of a Neon-Charged Cryogenic Loop Heat Pipe

As a typically highly efficient two-phase heat transfer under cryogenic temperature range, the operation performances of cryogenic loop heat pipes (CLHPs) might be affected by the relative location of different components. A transient mathematical model is established in present work. The model validation is demonstrated by comparing the simulation results with an auxiliary loop type neon-charged CLHP (Ne-CLHP) experiment data, and a good agreement is achieved. The effect of gravity caused by different layout orientations on the Ne-CLHP operation performances are then investigated numerically. There are three operation modes, namely normal LHP mode (n-LHP), gravity-assisted LHP mode (g-LHP), and gravity thermosyphon mode (GTP), according to different layout orientations and heat loads. Under the gravity resistance condition with a positive layout inclination angle, the Ne-CLHP is operated in n-LHP. The operating temperature increases with the positive layout inclination angle, and the heat transport capacity decreases. Under the gravity assistance condition with a negative layout inclination angle, all three operation modes may occur according mainly to the primary heat load. Only the two LHP modes are simulated in the present study, which located in the range between the transition heat load from GTP to g-LHP and the heat transport capacity. The lager negative layout incline angle, the higher transition heat load and the heat transport capacity, while lower operating temperature. In addition, the gravity-independence of cross-sectional two-phase distribution in the transport lines is discussed in the frame of dominant force analysis. The modeling effort will contribute to the technology research and development, as well as the operation control of CLHPs for space and ground applications.

Numerical and experimental study of end-milling process of titanium alloy with a cryogenic internal coolant supply

Cryogenic machining is an environmentally friendly process; liquid nitrogen (LN2) is sprayed onto cutting tool to reduce cutting temperature, increasing tool life. Cutting temperature and force were numerically predicted during cryogenic assisted milling with an internal coolant-assisted tool holder (internal cryogenic milling) for Ti-6Al-4V alloy. The influence of LN2 on the material temperature throughout the machining was estimated; a numerical model to simulate the initial temperature of work material was discussed by consideration of LN2 injective mechanism. A modified Johnson-Cook model including the cryogenic temperature range was adopted to model material plasticity. The predictive models were validated based on side-milling test. The predicted values captured the trend of experimental result; the minimum and maximum temperature errors were 0.1% and 8.6%, and those for the cutting force were 0.2% and 34.4%. Moreover, comprehensive experimental studies for the cutting temperature, cutting force, chip morphology, and chip composition were performed to understand the effect of cryogenic cooling condition. In internal cryogenic milling, the cutting temperature and force tended to be lower than dry machining. Based on the morphological analysis of the generated chip, the coefficient of sliding friction at tool-chip interface under the internal cooling was reduced by 21.4% as compared to the dry condition.

Lattice Dynamics, Phonon Chirality, and Spin–Phonon Coupling in 2D Itinerant Ferromagnet Fe3GeTe2

AbstractFe3GeTe2 has emerged as one of the most fascinating van der Waals crystals due to its 2D itinerant ferromagnetism, topological nodal lines, and Kondo lattice behavior. However, lattice dynamics, chirality of phonons, and spin–phonon coupling in this material, which set the foundation for these exotic phenomena, have remained unexplored. Here, the first experimental investigation of the phonons and mutual interactions between spin and lattice degrees of freedom in few‐layer Fe3GeTe2 is reported. The results elucidate three prominent Raman modes at room temperature: two A1g(Γ) and one E2g(Γ) phonons. The doubly degenerate E2g(Γ) mode reverses the helicity of incident photons, indicating the pseudoangular momentum and chirality. Through analysis of temperature‐dependent phonon energies and lifetimes, which strongly diverge from the anharmonic model below Curie temperature, the spin–phonon coupling in Fe3GeTe2 is determined. Such interaction between lattice oscillations and spin significantly enhances the Raman susceptibility, allowing to observe two additional Raman modes at the cryogenic temperature range. In addition, laser radiation‐induced degradation of Fe3GeTe2 in ambient conditions and the corresponding Raman fingerprint is revealed. The results provide the first experimental analysis of phonons in this novel 2D itinerant ferromagnet and their applicability for further fundamental studies and application development.

A thermo-mechanically coupled finite strain model for phase-transitioning austenitic steels in ambient to cryogenic temperature range

We present a finite-strain thermo-mechanically coupled continuum theory to model the material response of phase transitioning (metastable) austenitic steels from ambient (room) to cryogenic temperature. We applied our model to 316L stainless steel which shows plastic strain driven transformation from FCC austenite to BCC martensite phase at temperatures below room temperature and calibrated the model parameters using uniaxial tension tests at room and cryogenic temperatures. The constitutive model is able to successfully model the observed second strain-hardening behavior at cryogenic temperature due to formation of harder martensite at large strains. We implemented our coupled thermo-mechanical-phase transition model in the finite element program Abaqus by writing a user material subroutine and validated the model by conducting finite element based tension and compression simulations for a room temperature formed corrugated pipe. Comparisons of mechanical response between our simulation predictions and full-scale tests for the corrugated pipe at both room and cryogenic temperature show good accuracy of our model. We also conducted simulations to investigate the austenite-martensite phase transition near a notch tip in a flat plate geometry.

Influence of temperature on the magnetic properties of nanostructured Fe-49 wt.% Co-2 wt.% V alloy powder synthesized by mechanically milling pre-alloyed gas-atomized powder

Abstract The magnetic properties of nanostructured Fe-49 wt.% Co-2 wt.% V alloy powder, synthesized by mechanically milling pre-alloyed gas-atomized powder, were investigated from cryogenic to high temperatures (60–900 K). At cryogenic temperatures, the as-milled nanostructured alloy powder exhibited stable magnetic properties. The decrease in MS was by a minuscule ∼2 %—from ∼212 ± 1 Am2/kg (at 300 K) to ∼217 ± 2 Am2/kg (at 60 K), and the increase in HCI was by a modest (∼8%)—from ∼6.1 kA/m (at 300 K) to ∼6.6 kA/m (at 60 K). At high temperatures (>300 K), both MS and HCI decreased. Annealing improved the soft-magnetic properties of the as-milled alloy powder. The annealed alloy powders retained their nanostructure—grain size ∼15–30 nm. The as-milled alloy annealed at 900 K showed the highest MS and the lowest HCI among all the other annealing temperatures—MS increased by ∼7%–∼225 ± 1 Am2/kg and the HCI decreased to ∼1.0 kA/m. The annealed nanostructured Fe-49 wt% Co-2 wt.% V alloy powder exhibited magnetic properties comparable to a few annealed nanostructured Fe- Co-based alloys. The annealed nanostructured alloy powder displayed fairly stable magnetic properties over a wide range of cryogenic temperatures. The annealed Fe-49 wt.% Co-2 wt.% V alloy powder is better suited for soft-magnetic applications than the as-milled powder, from ambient to cryogenic temperatures.

Low-Temperature P–T Phase Diagram of the (Mg, Fe)SiO3 Perovskite

The electron spin states of iron in minerals of the Earth’s mantle at high pressures mostly determine the physicochemical properties of deep layers of the Earth and are of great interest not only for geophysics but also for fundamental physics of strongly correlated electron systems. In this work, using Raman and synchrotron Mossbauer nuclear forward scattering (NFS) spectroscopies, iron-containing magnesium–silicate perovskite (Mg, Fe)SiO3 (10% Fe) has been studied in the cryogenic temperature range of 35–300 K and at high pressures up to 48 GPa, which are created in diamond anvil cells. The analysis of NFS spectra has indicated that iron ions are in a nonmagnetic (para- or diamagnetic) state in the entire region of temperatures and pressures and the electronic properties can be controlled by means of the quadrupole splitting parameter. It has been found that an increase in the pressure and a decrease in the temperature are accompanied by a significant increase in the parameter Δ from 2 mm/s to ~4 mm/s, which indicates that the electronic state of Fe2+ ions changes. The maximum Δ value has been observed at P > 20 GPa, but the pressure behavior of a transition strongly depends on the temperature. Possible mechanisms of the transition have been discussed.

Nanoscale polysilicon in sensors of physical values at cryogenic temperatures

Studies of polysilicon in a wide range of concentrations from 2.4 × 1018 to 1.7 × 1020 in temperature range 1.6–300 K and high magnetic fields up to 14Т were carried out in order to predict the characteristics of a material suitable for the creation of microelectronic sensors of physical values based on SemOI-structures. One of the advantages of SemOI-structures is the ability to receive layers with difference in resistivity in a wide range: several orders of magnitude. As it is determined by studies at low temperatures the transfer of charge carriers in polysilicon occurs due to hopping on localized impurities. There have also been found combined mechanisms of current flow at low temperatures, which, depending on the observation temperature, are evident in the transition from the Mott law to the percolation mechanism of Shklovskii-Efros. Those effects can be used to create elements of sensor technology. Sensors of thermal quantities for cryogenic temperatures were developed with TCR = − 9% × K−1 in the range of 4.2–50 K and mechanical quantities for cryogenic temperatures were developed for ultra-sensitivity with coefficient of gauge-factor K = 15500 in the range of 4.2–50 K. Investigation in wide range of cryogenic temperatures was conducted with the purpose of optimizing the geometry of the sensor membrane (its thickness and surface area) in order to obtain optimal stresses and deformations in the membrane. This process is essential for the sensor to be able to provide a sufficient amount of the output signal while maintaining the strength of the membrane and the sensor structure as a whole.

Incoherent Photon Echo in an Inhomogeneous Ensemble of Semiconductor Colloidal Quantum Dots at Low Temperatures

A simple and effective technique for fabricating homogeneous films of colloidal quantum dots is developed. Incoherent photon echo signals in the prepared thin films of quantum dots are detected and studied in a wide range of cryogenic temperatures (from 4.5 to 50 K). The temperature dependence of the inverse optical dephasing time is constructed and possible mechanisms of ultrafast dephasing are analyzed in the indicated temperature range.

YAG:Yb3+ crystal as a potential material for optical temperature sensors

The possibilities are discussed of Y3Al5O12:Yb3+ crystal as a material for an optical temperature sensor (OTS) based on the temperature dependences of the more intense spectral emission lines and on the ratio of the absorption coefficients from the ground and first excited Stark sublevels. The operating temperature and average sensitivity for OTSs are determined. It is shown that the former is an effective method for an OTS in a cryogenic temperature range (40–130 K) and the latter in a high temperature range (500–1000 K).

Theoretical analysis and coating thickness determination of a dual layer metal coated FBG sensor for sensitivity enhancement at cryogenic temperatures

Use of Fiber Bragg Grating (FBG) sensor is very appealing for sensing low temperature and strain in superconducting magnets because of their miniature size and the possibility of accommodating many sensors in a single fiber. The main drawback is their low intrinsic thermal sensitivity at low temperatures below 120 K. Approaching cryogenic temperatures, temperature changes lower than a few degrees Kelvin cannot be resolved, since they do not cause an appreciable shift of the wavelength diffracted by a bare FBG sensor. To improve the thermal sensitivity and thermal inertia below 77 K, the Bare FBG (BFBG) sensor can be coated with high thermal expansion coefficient materials. In this work, different metal were considered for coating the FBG sensor. For theoretical investigation, a double layered circular thick wall tube model has been considered to study the effect on sensitivity due to the mechanical properties like Young’s modulus, Thermal expansion coefficient, Poisson’s ratio of selected materials at a various cryogenic temperatures. The primary and the secondary coating thickness for a dual layer metal coated FBG sensor have been determined from the above study. The sensor was then fabricated and tested at cryogenic temperature range from 4-300 K. The cryogenic temperature characteristics of the tested sensors are reported.

The critical electric field of gas mixtures over the extended range of cryogenic operating conditions

In this study, we provide the critical electric field and dielectric strength of cryogenic gas mixtures over an extended cryogenic temperature and pressure range that covers most of the operating conditions of superconducting applications. For gas-cooled cryogenic systems, condensation must not occur during operation. To prevent condensation, we determine the maximum allowed mole fractions of gas species consisting cryogenic gas mixtures by accounting for the operating conditions of cryogenic applications. Subsequently, we estimate the dielectric strength of the gas mixtures in terms of the density-reduced critical electric field ((E/N)cr), obtained by solving the Boltzmann equation with the two-term approximation method. Using the values of (E/N)cr, we calculate the critical electric field (Ecr) over the extended cryogenic operation range of 10–100 K at pressures between 1.0 and 2.0 MPa. The results show that the dielectric strength of cryogenic gas mixtures varies as a function of temperature at a constant operating pressure and reaches its minimum at the condensation point of each gas mixture. The results also suggest that (E/N)cr cannot accurately represent the maximum achievable dielectric strength of a gas mixture unless the maximum allowed mole fractions of gas species have been taken into account. Hence, we discuss (E/N)cr values that are derived from the regulated concentration of gas constituents, which will prevent the components of gas mixtures from condensing. This study provides useful recommendations on the suitability of the gas mixtures and useful reference data for the dielectric design of superconducting and cryogenic applications.