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Topological materials have shown promising potential in the spintronics application due to their conspicuous efficiency of charge-to-spin conversion. Our research investigates the temperature-dependent spin–orbit torque (SOT) from sputtered WTex. We reveal a strong temperature dependence of SOT and realize the current-induced SOT switching of WTex with perpendicular magnetic anisotropy structure under a wide range of 12 K to room temperature. Our findings reveal the temperature dependence of sputtered WTex and may pave the way for the spintronics application of semimetals under cryogenic temperature. [ABSTRACT FROM AUTHOR]

The bond dissociation energy of FeCr+ is measured using resonance enhanced photodissociation spectroscopy in a cryogenic ion trap. The onset for FeCr+ → Fe + Cr+ photodissociation occurs well above the lowest Cr+(6S, 3d5) + Fe(5D, 3d64s2) dissociation limit. In contrast, the higher energy FeCr+ → Fe+ + Cr photodissociation process exhibits an abrupt onset at the energy of the Cr(7S, 3d54s1) + Fe+(6D, 3d64s1) limit, enabling accurate dissociation energies to be extracted: D(Fe–Cr+) = 1.655 ± 0.006 eV and D(Fe+–Cr) = 2.791 ± 0.006 eV. The measured D(Fe–Cr+) bond energy is 10%–20% larger than predictions from accompanying CAM (Coulomb Attenuated Method)-B3LYP and NEVPT2 and coupled cluster singles, doubles, and perturbative triples electronic structure calculations, which give D(Fe–Cr+) = 1.48, 1.40, and 1.35 eV, respectively. The study emphasizes that an abrupt increase in the photodissociation yield at threshold requires that the molecule possesses a dense manifold of optically accessible, coupled electronic states adjacent to the dissociation asymptote. This condition is not met for the lowest Cr+(6S, 3d5) + Fe(5D, 3d64s2) dissociation limit of FeCr+ but is satisfied for the higher energy Cr(7S, 3d54s1) + Fe+(6D, 3d64s1) dissociation limit. [ABSTRACT FROM AUTHOR]

Luminescence thermometry is the most versatile remote temperature sensing technique and can be employed from living cells to large surfaces and from cryogenic temperatures to the melting points of metals. Ongoing research aims to optimize the sensitivity of the ratio between the emission intensity from two coupled excited states. However, this approach is inherently limited to temperature-dependent processes involving only the excited states. Here, we develop a novel measurement technique, called luminescence intensity ratio squared (LIR2) for the Yb3+/Er3+ pair, that combines the temperature sensitivity of ground- and excited-state populations. We use Y3Al5O12:Er3+,Yb3+ nanoparticles as a promising model system with both visible and infrared emissions. To apply our method, we record two luminescence spectra at different excitation wavelengths and determine the LIR2 using one emission in each of the two spectra. The LIR2 testing with Y3Al5O12 nanoparticles showed a sensitivity increase of 70% in the visible region and an impressive 230% increase in the NIR region compared to the conventional LIR method. This enhances the measurement precision by a factor of 1.5–2.5. The LIR2 based on the visible upconversion emission is particularly useful for measurements of high temperatures, while the LIR2 based on the downshifted ∼1.5 μm emission may revolutionize temperature measurements of biological samples in the range of physiological temperatures. [ABSTRACT FROM AUTHOR]

Naphthalene and azulene are isomeric polycyclic aromatic hydrocarbons (PAHs) and are topical in the context of astrochemistry due to the recent discovery of substituted naphthalenes in the Taurus Molecular Cloud-1 (TMC-1). Here, the thermal- and photo-induced isomerization, dissociation, and radiative cooling dynamics of energized (vibrationally hot) naphthalene (Np+) and azulene (Az+) radical cations, occurring over the microsecond to seconds timescale, are investigated using a cryogenic electrostatic ion storage ring, affording "molecular cloud in a box" conditions. Measurement of the cooling dynamics and kinetic energy release distributions for neutrals formed through dissociation, until several seconds after hot ion formation, are consistent with the establishment of a rapid (sub-microsecond) Np+ ⇌ Az+ quasi-equilibrium. Consequently, dissociation by C2H2-elimination proceeds predominantly through common Az+ decomposition pathways. Simulation of the isomerization, dissociation, recurrent fluorescence, and infrared cooling dynamics using a coupled master equation combined with high-level potential energy surface calculations [CCSD(T)/cc-pVTZ], reproduce the trends in the measurements. The data show that radiative cooling via recurrent fluorescence, predominately through the Np+ D0 ← D2 transition, efficiently quenches dissociation for vibrational energies up to ≈1 eV above dissociation thresholds. Our measurements support the suggestion that small cations, such as naphthalene, may be more abundant in space than previously thought. The strategy presented in this work could be extended to fingerprint the cooling dynamics of other PAH ions for which isomerization is predicted to precede dissociation. [ABSTRACT FROM AUTHOR]

Recombination of vibrationally cold N 2 + ions with electrons was studied in the temperature range of 140–250 K. A cryogenic stationary afterglow apparatus equipped with cavity ring-down spectrometer and microwave diagnostics was utilized to probe in situ the time evolutions of number densities of particular rotational and vibrational states of N 2 + ions and of electrons. The obtained value of the recombination rate coefficient for the recombination of the vibrational ground state of N 2 + with electrons is αv=0 = (2.95 ± 0.50) × 10−7(300/T)(0.28±0.07) cm3 s−1, while that for the first vibrationally excited state was inferred as αv=1 = (4 ± 4) × 10−8 cm3 s−1 at 250 K. [ABSTRACT FROM AUTHOR]

Rare-earth-based oxides are gradually becoming a new research hotspot in cryogenic magnetic refrigeration due to their advantages in bulk preparation and application. Magnetic transition from AFM to FM in EuTiO 3 provides an effective strategy for modulating magnetism and enhancing magnetocaloric effect (MCE) in this magnetic system. Herein the structure, magnetism, and MCE of a series of Ta-doped EuTiO 3 perovskites were investigated in detail. A significant lattice expansion was achieved by partially substituting Ta for B-site Ti without altering the crystal configuration, which tailors the cryogenic magnetism and MCEs of these compounds. Lattice expansion enhances ferromagnetic coupling, weakens antiferromagnetic super-exchange, and promotes the AFM-FM transition in EuTiO 3 , which enhances the low-field MCEs. The phase transition temperature of the compound increases from 5.5 K to about 9.5 K with increasing Ta doping. The values of − Δ S M max and RC of EuTi 0.9375 Ta 0.0625 O 3 are 15.9 J kg−1 K−1and 67.8 J kg−1 under magnetic field change of 0–1 T, which are enhanced by 44.5% and 105.5% over EuTiO 3 , respectively. Although a decrease in the magnetic entropy change occurs with increasing Ta doping, the refrigerating capacity is improved due to the broadened temperature range. This work not only provides a strategy for tailoring magnetic phase transition and MCE of magnetocaloric materials, but also offers effective candidates for magnetic refrigeration over a wide temperature range. [ABSTRACT FROM AUTHOR]

The authors present the results of laboratory tests analysing the impact of selected cutting data and tool geometry on surface quality, chip type and cutting forces in the process of orthogonal turning of sintered cobalt. The selected cutting data are cutting speed and feed rate. During the experiments, the cutting speed was varied in the range of vc = 50–200 m/min and the feed rate in the range of f = 0.077–0.173 mm/rev. In order to measure and acquire cutting force values, a measuring setup was assembled. It consisted of a Kistler 2825A-02 piezoelectric dynamometer with a single-position tool holder, a Kistler 5070 signal amplifier and a PC with DynoWare software (Version 2825A, Kistler Group, Winterthur, Switzerland)). The measured surface quality parameters were Ra and Rz. The components of the cutting forces obtained in the experiment varied depending on the feed rate and cutting speed. The obtained test results will make it possible to determine the optimal parameters for machining and tool geometry in order to reduce the machine operating time and increase the life of the cutting insert during the turning of sintered cobalt, which will contribute to sustainable technology. [ABSTRACT FROM AUTHOR]

We have utilised the 4,6-di-tert-butyl resorcinol bis(diphenylphosphinite) (POCOP) ligand for exploring its coordination ability towards group 11 metal centres. The treatment of the bidentate ligand 1 with various coinage metal precursors afforded a wide range of structurally diverse complexes 2–12, depending upon the metal precursors used. This furnishes several multinuclear Cu(I) complexes with dimeric (2) and tetrameric cores (3, 4, and 5). The tetrameric stairstep complex 4 shows thermochromic behaviour, whereas the dimeric complex 2 and tetrameric complex 3 show luminescence properties at cryogenic temperatures. Interestingly, the halide substitution reaction of the dimeric complex 2 with KPPh2 produces a unique mixed phosphine-based tetrameric Cu(I) complex, 5. Treatment of the POCOP ligand with [CuBF4(CH3CN)4] in the presence of 2,2′-bipyridine afforded heteroleptic complex 6, consisting of tri- and tetra-coordinated cationic Cu(I) centres. Furthermore, we could also isolate cubane (8) and stairstep (9) complexes of Ag(I). The cationic Au(I) complex (12) was obtained from the dinuclear Au(I) complex of POCOP, 11. Complex 12 revealed the presence of a strong intramolecular aurophilic interaction with an Au⋯Au bond distance of 3.1143(9) Å. Subsequently, the photophysical properties of these complexes have been studied. All the complexes were characterised by single-crystal X-ray diffraction studies, routine NMR techniques, and mass spectroscopy. [ABSTRACT FROM AUTHOR]

Source–drain contacts seriously affect low frequency noise (LFN) in amorphous IZO (a-IZO) thin-film transistors with bilayer ITO/Mo electrodes at cryogenic temperatures. In the range of 7–300 K, electrical and LFN performances of devices are measured, and the temperature dependence of channel resistances (Rch) and contact resistances (Rsd) is also analyzed. The carrier transport transition both occurs in a-IZO channels at 80 K and in ITO/Mo electrodes at 100 K, which causes the variation in Rsd and Rch. Below 80 K, the variable range hopping conduction dominates in the channels and contacts with Rsd/Rch ratio > 1. The LFN measured results indicate that the noise is contact-dominated. At higher temperatures above 120 K, the band conduction dominates in the channel, with Rsd/Rch ratio < 1, and the noise is channel-dominated. The main mechanism of noise transfers from the mobility fluctuation to the carrier number fluctuation. We consider that the contribution of contact noise to total LFN is determined by the Rsd/Rch ratio. This work provides comments for the selection of electrode materials in devices applied to cryogenic integration circuits. [ABSTRACT FROM AUTHOR]

In this study, we systematically investigate the magnetic domain structure of Fe4GeTe2 single crystals, employing a cryogenic vector-field magnetic force microscope to probe its temperature and magnetic field dependencies. The material undergoes a spin-reversal transition at around 110 K, leading to a gradual magnetization reorientation from in-plane to out-of-plane as temperature decreases. Our observations reveal a complex domain structure featuring striped shapes enclosed by wavy closed loops, exhibiting limited sensitivity to temperature variations without an external magnetic field. When subject to an out-of-plane magnetic field, the domain structure transforms into micrometric elongated striped shapes, gradually evolving into a more irregular pattern. Conversely, in in-plane measurements, the system displays an inhomogeneous distribution of micrometric bubble-like domains, progressively interconnecting into striped shapes. These distinctive responses are attributed to the interplay between small uniaxial and shape anisotropies within the material. Our findings contribute to a deeper understanding of the magnetic domain dynamics in van der Waals ferromagnetic materials, laying the groundwork for further investigations and potential applications in electronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] Specific alkaline cation effects control the area per headgroup of alkylester sulphates, which modifies the spontaneous packing of the surfactants. The resulting effective packing minimizes the total bending energy frustration and results in a Boltzmann distribution of coexisting pseudo-phases. These pseudo-phases constitute of micelles and other structures of complex morphology: cylindrical sections, end-caps, branching points, and bilayers, all in dynamic equilibrium. According to our model, excess of end-caps or excess of branching points lead to low viscosity, whereas comparable amounts of both structures lead to viscosity maxima. Relative occurrence of branching points and end-caps is the molecular mechanism at the origin of the salt-sensitive viscosity peak in the "salt-curve" (viscosity against salt concentration at fixed surfactant concentration). Up to now, and as indicated in former papers, this has been a pure model without microscopic verification. In this work, we introduce explicit counting of the number of coexisting pseudo-phases as observed by state-of-the-art cryogenic transmission electron microscopy (cryo-TEM). The model system used, i.e., sodium laurylethersulfate (SLES)/salt/water, is very common as part of cosmetic formulations. As added salts, we used Li+, Na+, K+, and Cs+ chlorides. In parallel to imaging, we measured the macroscopic viscosities of the different solutions. With cryogenic transmission electron microscopy (cryo-TEM), we imaged a variety of morphologies (pseudo-phases) in the different aqueous surfactant/salt solutions: cylindrical micelles with end-caps, discs surrounded by "rims", entangled thread-like micelles with branching points, networks with gliding branching points, and bilayers. The relative chemical potentials of these morphologies could be approximated simply by counting the relative proportion of their occurrence. This simple multi-scale approach avoids any ad-hoc "specificity" assumption of ions, and is based on the bending energy model in an extended version of the Benedek "ladder model". It is capable of explaining and even quantifying the location of all viscosity peaks in the "salt-curves" for the different cations investigated, thus confirming the previously proposed model experimentally, and – thanks to cryo-TEM – for the first time on a microscopic scale. Moreover, this approach can also be applied when the added cations lead to newly observed pseudo-phases, such as discs and vesicles. To the best of our knowledge, this is the first time that cryo-TEM is used, together with a mesoscopic model, to describe a macroscopic property such as viscosity and specific ion effects on it, without any a priori assumption about these effects. So, in total, we could a) confirm the predictions of the previously developed model, b) use cryo-TEM imaging and viscosity measurements to predict and find unusual morphologies when varying the cations of the added salt, and c) count the pseudo-phases in cryo-TEM micrographs to quantitatively explain the different nanostructures. [ABSTRACT FROM AUTHOR]

There is interest in exporting carbon-neutral liquid hydrogen (LH2) as a replacement for fossil fuels. However, transporting LH2 for maritime export is made difficult by the requirement for high performance insulation to reduce pressure rise and cargo losses through venting. One method to reduce boil-off losses is to allow the tank to self-pressurise along the journey and delay venting by increasing the tank maximum allowable working pressure (MAWP). To assess this, an analytical model was developed, in Matlab, to predict pressure rise and boil-off gas (BOG) generation. Perlite insulation was modelled using analytical expressions for temperature-dependent specific heat capacity and thermal conductivity. The model was tuned over a range of data, including for pressure and boil-off rate. This model was used to assess an LH2 carrier carrying four 40,000 m3 spherical tanks insulated with evacuated perlite. At atmospheric pressure, a loss rate of 0.04 % per day was predicted for the laden voyage. Over a voyage duration of 15 days the model predicts that boil-off can be reduced by 31 % when the tank is allowed to self-pressurise to 5 kPaG. This is primarily due to a reduced rate of boil-off as the liquid transitions from a subcooled to a saturated state. At higher pressures, the delay in venting was observed to be a major contributor to reduction in boil-off, with a reduction of 91 % in losses at MAWP of 60 kPaG. Pressure rise was observed to be significantly greater than a saturated liquid model would suggest, particularly at high fill levels. Finally, an empirical equation for the pressure rise was fitted to 27 data points from the literature, allowing for quick estimates of the pressure rise based on the fill level, the Rayleigh number and the surface to volume ratio in the ullage. This study suggests very low loss storage of LH2 can be achieved in large double-wall tanks over a sufficiently short journey, with only marginal pressurisation. Additional investigations on the effect of ship motion on phase change within the tank will be required to fully understand design considerations for LH2 storage tanks. • New analytical model of pressurised cryogenic storage for boil-off prediction. • Effect of venting pressure on boil-off is investigated for periods of up to 15 days. • Allowing pressurisation to 60kPaG reduced losses by 91% at high fill levels. • Empirical correlation developed for pressure rise. [ABSTRACT FROM AUTHOR]

In a cooling system for radio astronomy receivers, maintaining cold heads and compressors is essential for consistent performance. This project focuses on monitoring the power currents of the cold head's motor to address potential mechanical deterioration, which could jeopardize the overall functionality of the system. Using Hall effect sensors, a microcontroller-based electronic board, and artificial intelligence, the system detects and predicts anomalies. The model operates using an unsupervised approach based on incremental clustering. Since potential fault scenarios can be multiple and often challenging to simulate or identify during training, the system is initially trained using known operational categories. Over time, the system adapts and evolves by incorporating new data, which can be assigned to existing categories or, in the case of new anomalies, form new categories. This incremental approach enables the system to enhance its performance over the years, adapting to new anomaly scenarios and ensuring precise and reliable monitoring of the cold head's health. [ABSTRACT FROM AUTHOR]

In 1998, the Hefei National Synchrotron Radiation Laboratory completed the 6 T superconducting Wiggler magnets system. The consumption of liquid helium increases year by year during long operations. In order to upgrade the cryogenic system and remove the use of liquid helium, GM cryocoolers are introduced as the cooling source. The liquid nitrogen and radiation-proof cold screen of the original cryogenic system were removed, and the original copper current leads were replaced with high-temperature superconducting current leads. The total heat load of the cryogenic system is 2.33 W at 4.2 K and 108 W at 60 K. Three GM cryocoolers are selected as the cryogenic source. They can provide 3.75 W at 4.2 K and 210 W at 60 K. In the absence of an external precooling source, the final cryogenic system was successfully cooled and produced liquid helium at a liquefaction rate of 12 L/day at 1.1 bar (inflationary pressure) and had an excess cooling capacity of more than 1.05 W at 4.1 K. [ABSTRACT FROM AUTHOR]

This article discusses the effect of machining assistance on the machinability and surface integrity of titanium and nickel-based alloys for turning operations. The presented results are based on a literature review of the principal experimental work published by the French research laboratories within the framework of the Manufacturing 21 group. The work presented focuses on the assistances the most studied by the research group: cryogenic assistance and high-pressure assistance. This paper specifically addresses the experimental approaches used to determine the effect of the assistant on the cutting force, tool wear, chip formation, microstructural changes, and residual stresses generated on the workpiece machined surface. This literature review is completed by new results comparing machining tests on the Ti6Al4V titanium alloy using high pressure and cryogenic assistances. The results show that the assistances increase the tool life, as well as improve the surface integrity of the parts. However, these gains are not identical from one material to another. In particular, titanium alloys and nickel alloys show how a very different gains for a fixed assistance. The conclusions presented highlight current trends and research needs. [ABSTRACT FROM AUTHOR]

We, the QUARTET Collaboration, propose an experiment to measure the nuclear charge radii of light elements with up to 20 times higher accuracy. These are essential both for understanding nuclear physics at low energies, and for experimental and theoretical applications in simple atomic systems. Such comparisons advance the understanding of bound-state quantum electrodynamics and are useful for searching for new physics beyond the Standard Model. The energy levels of muonic atoms are highly susceptible to nuclear structure, especially to the mean square charge radius. The radii of the lightest nuclei (with the atomic number, Z = 1 , 2 ) have been determined with high accuracy using laser spectroscopy in muonic atoms, while those of medium mass and above were determined using X-ray spectroscopy with semiconductor detectors. In this communication, we present a new experiment, aiming to obtain precision measurements of the radii of light nuclei 3 ≤ Z ≤ 10 using single-photon energy measurements with cryogenic microcalorimeters; a quantum-sensing technology capable of high efficiency with outstanding resolution for low-energy X-rays. [ABSTRACT FROM AUTHOR]

We describe the design principles, fabrication, and characterization of a precision AC resonant capacitance bridge (RCB) sensor, based on a resonant differential planar printed circuit board transformer with a solid (ungapped) MnZn ferrite core, demonstrating a short-term sensitivity at 293 K of 0.225 ± 0.005 aF/√Hz at around 120 kHz resonance frequency and 1 Hz Fourier measurement frequency. At 120 K, the RCB short term noise sensitivity is 0.118 ± 0.005 aF/√Hz. We compare the ungapped configuration to five different RCBs: three with a core gap of 65 μm and two with a core gap of 130 μm. Their average room temperature short term noise sensitivities are 0.30 ± 0.01 and 0.45 ± 0.01 aF/√Hz, while the cryogenic operation of these transformers at 120 K resulted in averaged sensitivities of 0.23 ± 0.01 and 0.36 ± 0.01 aF/√Hz, respectively. Multi-hour room temperature runs, with one core of each of the three gap types, proved the stability of their long-term sensitivities of 0.234 ± 0.005, 0.338 ± 0.009, and 0.435 ± 0.010 aF/√Hz for the ungapped (40-h duration) and the 65 and 130 μm (28-h duration) cores, respectively. At 0.1 mHz, a critical frequency for space gravitational wave detectors, the respective sensitivities are 0.25 ± 0.02, 0.35 ± 0.02, and 0.53 ± 0.07 aF/√Hz. Measurements with the ungapped transformer configuration for temperatures from 325 to 349 K further validate the dependence of the noise model on temperature and permeability. The performance of our RCB with an ungapped core matches the calculated performance value and shows an improvement in signal-to-noise ratio of two or more compared with capacitance bridges developed for similar applications. A further factor of about two noise reductions is achieved by cooling to 120 K. [ABSTRACT FROM AUTHOR]

Hydrogen can become a prevalent renewable fuel in the future green economy, but technical and economic hurdles associated with handling hydrogen must be overcome. To store and transport hydrogen in an energy-dense liquid form, very cold temperatures, around 20 K, are required. Evaporation affects the achievable mass flow rate during the high-speed transfer of hydrogen at large pressure differentials, and accurate prediction of this process is important for the practical design of hydrogen transfer systems. Computational fluid dynamics modeling of two-phase hydrogen flow is carried out in the present study using the volume-of-fluid method and the Lee relaxation model for the phase change. Suitable values of the relaxation time parameter are determined by comparing numerical results with test data for high-speed two-phase hydrogen flows in a configuration involving a tube with sudden expansion, which is common in practical systems. Simulations using a variable outlet pressure are conducted to demonstrate the dependence of flow rates on the driving pressure differential, including the attainment of the critical flow regime. Also shown are computational results for flows with various inlet conditions and a fixed outlet state. Field distributions of the pressure, velocity, and vapor fractions are presented for several flow regimes. [ABSTRACT FROM AUTHOR]

The current work presents a 3D numerical investigation of heat transfer characteristics of twin heaters exposed to cooling. The liquid nitrogen is considered as the fluid medium for heat rejection. Six distinct heater configurations are taken into account and the impact of heater configuration on flow and heat transfer pattern is demonstrated. The heaters provide heat at a steady rate (W/m3). The velocity and temperature contours, average Nusselt number ( Nu Avg ) , the maximum vertical velocity of fluid flow, and average velocity of fluid flow is plotted for all the six heater configurations for the comparative study. Moreover, another parametric study has been done to find the optimum spacing between two heaters for the best heat transfer rate. The reliance on average Nusselt number, average fluid flow velocity, entropy generation as a function of heat generation rate for various heater configurations are outlined graphically. The after-effects of this study show that heater configurations can impressively influence the heat transfer rate, fluid flow characteristics, and entropy generation under the same heat generation rate in the heater. The most noteworthy Nu Avg on the heater surface is acquired when heater configuration is circular. In each one of the heater configurations, the value of Bejan number is under 0.5. Henceforth, it may be expressed that irreversibility because of fluid friction prevails over irreversibility because of heat transfer. [ABSTRACT FROM AUTHOR]

Covalently‐linked chromophore‐radical systems with their unique optical and magnetic properties are useful for applications in, e. g., quantum information science. To expand the catalog of molecular systems, we synthesized and characterized six novel chromophore–radical and radical‐chromophore‐radical systems employing derivatives of perylene diimide (PDI) as the chromophore and trityl as the radical. The EPR properties of these compounds were evaluated in solution at cryogenic and room temperatures. In addition, the electron spin‐spin coupling in the two bistrityl systems was investigated using DQC measurements. The presented results serve as a basis for further spectroscopic investigations under photoexcitation of the PDI core. [ABSTRACT FROM AUTHOR]

Narrow bandgap materials have garnered significant attention within the field of broadband photodetection. However, the performance is impeded by diminished absorption near the bandgap, resulting in a rapid decline in photoresponsivity within the mid‐wave infrared (MWIR) and long‐wave infrared (LWIR) regions. Furthermore, they mostly worked in cryogenic temperature. Here, without the assistance of any complex structure and special environment, it is realized high responsivity covering ultra‐broadband wavelength range (Ultraviolet (UV) to LWIR) in a single quasi‐1D pseudogap (PG) system (TaSe4)2I nanoribbon, especially high responsivity (From 23.9 to 8.31 A W−1) within MWIR and LWIR region at room temperature (RT). Through direct probing the carrier relaxation process with broadband time‐resolved transient absorption spectrum measurement, the underlying mechanism of majorly photoconductive effect is revealed, which causes an increased spectral weight extended to PG region. This work paves the way for realizing high‐performance uncooled MWIR and LWIR detection by using quasi‐1D PG materials. [ABSTRACT FROM AUTHOR]

Recent advances reveal that due to the cross‐relaxation restriction, impressive upconversion (UC) enhancement (≈100‐folds) can be achieved in cryogenic Er3+‐rich core‐inert shell nanostructures (e.g., NaErF4@NaYF4), which opens up exciting opportunities in diverse frontier applications. However, further promotion of UC intensity is still highly desired, in which the rational design of nanostructures can play a key role. Herein, it is demonstrated that adopting an active shell design will constantly benefit the UC within a wide temperature range (40–300 K). Specifically, through constructing the luminescent core@active shell@inert shell sandwich nanostructure (e.g., NaErF4@NaYbF4@NaYF4), 8.3–73‐folds UC enhancement will be achieved (taking the corresponding core@inert shell structures as competitors). Moreover, from spectral‐domain and time‐domain spectroscopic experiments, the relevant UC enhancement is convincingly attributed to a temperature‐dependent energy injection process (from the active shell to the luminescent core). More interestingly, the unique property of the material makes a temperature‐induced high‐level encryption application possible, which is obtained by employing the nanomaterials on a quick response (QR) code. These results not only deepen the UC mechanism in multi‐layer nanostructures, but also introduce an expanded dimension (via low temperatures) in information security. [ABSTRACT FROM AUTHOR]

Cryogenic detectors can detect the smallest energy depositions via the scattering of the incoming particle with the detector material. The deposited energy leads to minimal temperature rises of a few μK , read out via transition edge sensors and SQUIDs. Using scintillating crystals as detector material offers the possibility of discriminating between nuclear recoils from dark matter scattering and electromagnetic background events. The CRESST experiment pioneered this technology and is still among the most sensitive experiments searching for sub-GeV dark matter particles. The technology is now also used by other experiments for dark matter searches (COSINUS) and for measuring coherent elastic neutrino-nucleus scattering (NUCLEUS). We discuss cryogenic detectors' detection principle and their application. We present the latest dark matter results from CRESST, a new type of background, and the status of the COSINUS and NUCLEUS experiments. This article is part of the theme issue 'The particle-gravity frontier'. [ABSTRACT FROM AUTHOR]

We present the requirements, design, and evaluation of the cryogenic continuously rotating half-wave plate (CHWP) for the Simons Observatory (SO). SO is a cosmic microwave background polarization experiment at Parque Astronómico de Atacama in northern Chile that covers a wide range of angular scales using both small (⌀ 0.42 m) and large (⌀ 6 m) aperture telescopes. In particular, the small aperture telescopes (SATs) focus on large angular scales for primordial B-mode polarization. To this end, the SATs employ a CHWP to modulate the polarization of the incident light at 8 Hz, suppressing atmospheric 1/f noise and mitigating systematic uncertainties that would otherwise arise due to the differential response of detectors sensitive to orthogonal polarizations. The CHWP consists of a 505 mm diameter achromatic sapphire HWP and a cryogenic rotation mechanism, both of which are cooled down to ∼50 K to reduce detector thermal loading. Under normal operation, the HWP is suspended by a superconducting magnetic bearing and rotates with a constant 2 Hz frequency, controlled by an electromagnetic synchronous motor. We find that the number of superconductors and the number of magnets that make up the superconducting magnetic bearing are important design parameters, especially for the rotation mechanism's vibration performance. The rotation angle is detected through an angular encoder with a noise level of 0.07 μrad s . During a cooldown process, the rotor is held in place by a grip-and-release mechanism that serves as both an alignment device and a thermal path. In this paper, we provide an overview of the SO SAT CHWP: its requirements, hardware design, and laboratory performance. [ABSTRACT FROM AUTHOR]

In 2014, we introduced a new experimental approach to study the UV photo-processing of cryogenic ices of astrophysical interest using laser ablation in a combination of ionization and time-of-flight mass spectrometry (ToF-MS). The setup, Mass Analytical Tool to Research Interstellar ICES, allowed us to detect newly formed species at low abundances. However, we found that with the increase in molecular complexity over the years, the detection of larger photoproducts was hindered by the dynamic range of detectors used. Here, we introduce a method to overcome this issue that we expect to be useful for similar applications in other research fields. The concept is based on a precisely controlled high-energy pulser that regulates the voltage across the deflection plates of the ToF-MS instrument to deflect the most abundant species and prevent them from reaching the detector. In this way, the detector sensitivity can be increased from an operating voltage of 2500 V up to 3000 V. The applicability is first illustrated in the simple case of an argon matrix, where 40Ar+ ions are deflected to increase the detection sensitivity for 40Ar2+ at m/z = 20 and 40 A r 2 + at m/z = 80 by a factor 30. Similarly, it is shown that substantially larger complex organic molecules, an important species in astrochemical reaction networks, can be measured for UV irradiated methanol ice. [ABSTRACT FROM AUTHOR]

To search for dark matter candidates with masses below O (MeV), the SPLENDOR (Search for Particles of Light dark mattEr with Narrow-gap semiconDuctORs) experiment is developing novel narrow-bandgap semiconductors with electronic bandgaps on the order of 1–100 meV. In order to detect the charge signal produced by scattering or absorption events, SPLENDOR has designed a two-stage cryogenic HEMT-based amplifier with an estimated charge resolution approaching the single-electron level. A low-capacitance (∼ 1.6 pF) HEMT is used as a buffer stage at T = 10 mK to mitigate effects of stray capacitance at the input. The buffered signal is then amplified by a higher-capacitance (∼ 200 pF) HEMT amplifier stage at T = 4 K. Importantly, the design of this amplifier makes it usable with any insulating material—allowing for rapid prototyping of a variety of novel detector materials. We present the two-stage cryogenic amplifier design, preliminary voltage noise performance, and estimated charge resolution of 7.2 electrons. [ABSTRACT FROM AUTHOR]

We are developing the Cryogenic AntiCoincidence detector (CryoAC) of the ATHENA X-IFU spectrometer. It is a TES-based particle detector aimed to reduce the background of the instrument. Here, we present the result obtained with the last CryoAC single-pixel prototype. It is based on a 1 cm2 silicon absorber sensed by a single 2 mm × 1 mm Ir/Au TES, featuring an on-chip heater for calibration and diagnostic purposes. We have illuminated the sample with 55Fe (6 keV line) and 241Am (60 keV line) radioactive sources, thus studying the detector response and the heater calibration accuracy at low energy. Furthermore, we have operated the sample in combination with a past-generation CryoAC prototype. Here, by analyzing the coincident detections between the two detectors, we have been able to characterize the background spectrum of the laboratory environment and disentangle the primary (i.e. cosmic muons) and secondaries (mostly secondary photons and electrons) signatures in the spectral shape. [ABSTRACT FROM AUTHOR]

We have developed a cryogenic characterization platform for ultrafast photodiodes, whose time domain responses are extracted by electro-optic sampling using femtosecond laser pulses in a pump-probe configuration. The excitation of the photodiodes with the pump beam and the electro-optic sampling crystals with the probe beam are realized in a fully fiber-coupled manner. This allows us to use the characterization platform at different temperatures, ranging from cryogenic to room temperature. As an application example, we characterize the time-domain response of commercial p-i-n photodiodes with a nominal bandwidth of 20 GHz and 60 GHz at temperatures of 4 K and 300 K and in a large parameter range of photocurrent and reverse bias. For these photodiodes, we detect frequency components up to approximately 250 GHz, while the theoretical bandwidth of our sampling method exceeds 1 THz. Our measurements demonstrate a significant excitation power and temperature dependence of the photodiodes' ultrafast time responses, reflecting, most likely, changes in carrier mobilities and electric field screening. Since our system is an ideal tool to characterize and optimize the response of fast photodiodes at cryogenic temperatures, it has a direct impact on applications in superconducting quantum technology such as the enhancement of optical links to superconducting qubits and quantum-accurate waveform generators. [ABSTRACT FROM AUTHOR]

Tokamak fusion reactors produce energetic He ions that penetrate surfaces less than 20 μm and neutrons that spread throughout the reactor. Experiments with similar swift He ions in heavy metals show that the vibronic coupling of nonlinear lattice excitations creates mobile lattice excitations, called quodons. These are decoupled from phonons, move ballistically at near sonic speed, and propagate easily in metals and insulators. They can couple to and transport electric charge, which allows their observation in experiments. They rapidly disperse heat throughout a fusion reactor and carry charge through electrical insulators. In this article, an experimental design is presented that separates quodon current and conduction current and therefore makes it possible to measure the former. Also, the time‐of‐flight experiments are presented that lead to an estimation of quodon speed which is of the order of the sound velocity and therefore much faster than the drift of electrons or holes in conduction currents. Herein, results are presented on quodon current in tungsten, a material widely used in nuclear fusion technology, showing that many quodons are produced in fusion reactors. It is predicted that at high output powers, quodons created by He ions and neutrons may adversely impact on cryogenic systems. [ABSTRACT FROM AUTHOR]

Remarkable enhancement in green and red upconversion (UC) emissions by 124 and 88 %, respectively was achieved whereas down‐conversion (DC) luminescence in NIR‐II region (~1540 nm) was improved by 20 % in Th4+ co‐doped YF3 : Yb3+,Er3+ nanocrystalline particles. The same is ascribed to lowering of symmetry via formation of asymmetric Er−F bonds and less symmetric Y3+ sites due to distortions on Th4+ co‐doping. Benefiting from the distinct temperature response of stark sublevels of the 4S3/2 and 4F9/2 states, we have proposed a strategy for luminescence intensity ratios (LIR) based thermometry involving thermally coupled (TCL) stark sub‐levels. This can be promising in more accurate temperature read‐out at cryogenic temperatures (~ −193 °C). Using the same, high Sa and Sr values of 0.0139 K−1 (80 K) and 0.682 % K−1(80 K) were obtained for 4S3/2 (1)/4S3/2 (2)→4I15/2 transitions. Higher Sa and Sr values of 0.226 K−1 (80 K) and 2.627 %K−1(80 K) were obtained for 4F9/2 (1)/4F9/2 (2)→4I15/2 transitions. The high sensitivity values were obtained than that reported for the YF3 host. We believe this work with improved UC luminescence on Th4+ addition will be boon to cryogenic temperature‐sensing. [ABSTRACT FROM AUTHOR]

• We develop a program capable of multi-threading and automatically running REGEN 3.3 software to generate 181,440 regenerator performance data. • We use a simple and novel one-dimensional convolutional neural network model to predict regenerator performance. • This model exhibits excellent performance and high reliability in both fitting and generalization. • This model computes diverse ruleless regenerator parameters, reducing compute time from 2500 min for 1000 data with REGEN 3.3 software to 130 ms. The regenerator is the core component of the regenerative cryogenic refrigerator, for its structure sizes, operating parameters and phase characteristics at the cold and hot ends co-determine the power and efficiency of the refrigerator, and the design parameters of other coupled components. Efficiently predicting the regenerator performance can reduce the design period of cryogenic refrigerators. Addressing the long computational time constraints in the traditional numerical simulation methods, a novel approach based on a one-dimensional convolutional neural network (1D-CNN) was proposed. Initially, a program capable of multi-threading and automatically running the specialized regenerator calculation software REGEN 3.3 was developed. The performance of the regenerators with various parameter combinations at the cold end temperature of 60–120 K were calculated and 181,440 pieces of data were obtained. Subsequently, the architecture and hyperparameters of the model were determined. The trained model exhibits an average relative error of 3.83% for predicting regenerator power, 0.13% for predicting pressure ratio at the hot end, and 1.55% for predicting the coefficient of performance (COP). The model's generalization ability was confirmed by generating data points beyond the original dataset. Additionally, the model allows for the simultaneous calculation of multiple sets of irregular regenerator parameters, and reduces the calculation time from 2500 min for 1000 pieces using REGEN 3.3 software to just 130 ms, representing a decrease by nearly six orders of magnitude. This approach effectively resolves the long computation time associated with traditional numerical simulation methods, and will present a new solution for the rapid and precise design of regenerators. [ABSTRACT FROM AUTHOR]

Cross-sections and rate coefficients for rovibronic excitation of the CH+ ion by electron impact and dissociative recombination of CH+ with electrons are evaluated using a theoretical approach combining an R-matrix method and molecular quantum defect theory. The method has been developed and tested, comparing the theoretical results with the data from the recent Cryogenic Storage Ring experiment. The obtained cross-sections and rate coefficients evaluated for temperatures from 1 to 10 000 K could be used for plasma modelling in the interpretation of astrophysical observations and also in the technological applications where the molecular hydrocarbon plasma is present. [ABSTRACT FROM AUTHOR]

Mutual neutralization of hydronium (H3O+) and hydroxide (OH−) ions is a very fundamental chemical reaction. Yet, there is only limited experimental evidence about the underlying reaction mechanisms. Here, we report three-dimensional imaging of coincident neutral products of mutual-neutralization reactions at low collision energies of cold and isolated ions in the cryogenic double electrostatic ion-beam storage ring (DESIREE). We identified predominant H2O + OH + H and 2OH + H2 product channels and attributed them to an electron-transfer mechanism, whereas a minor contribution of H2O + H2O with high internal excitation was attributed to proton transfer. The reported mechanism-resolved internal product excitation, as well as collision-energy and initial ion-temperature dependence, provide a benchmark for modeling charge-transfer mechanisms. [ABSTRACT FROM AUTHOR]

Hydrogen will likely be stored and transported at high densities to have sufficient hydrogen on-site for efficient distribution. Cryogenic compressed hydrogen (CcH 2) is a high-density hydrogen storage method combining cryogenic temperatures and high pressures. Hydrogen releases from such high-density sources will result in high-momentum jets and jet flames if the jets ignite. This study modelled CcH 2 jet flames for stagnation pressures of 2∼5 bar and stagnation temperatures of 55∼150 K. The numerical models were validated by experimental data from the literature. The results show that the flame length increases with increasing pressure but decreases with increasing temperature. The CcH 2 jet flames are longer than their room-temperature counterparts with the same mass flow rate. Then, the CcH 2 jet flame lengths were correlated with the mass flow rate and stagnation temperature. Correlations were also developed for predicting trajectory temperatures and the radial temperature distributions in the CcH 2 jet flames. The present study provides a scientific basis for developing cryogenic hydrogen safety codes and standards and quantitative risk assessment models. • Cryogenic compressed hydrogen (CcH 2) jet flames were modelled. • The CcH 2 jet flame lengths were correlated with the mass flow rate and stagnation temperature. • The trajectory and radial temperature distributions were analyzed and correlated. [ABSTRACT FROM AUTHOR]

High-pressure or cryogenic conditions relevant to hydrogen applications introduce non-idealities in the property of fluid, which requires using real gas equations of state in numerical simulation. However, intrinsic but non-physical discontinuities exist in the partial derivatives with respect to temperature of the molecular attraction term of popular cubic equations of state. This feature is related to the van der Waals mixing rule and results in non-physical discontinuities in the thermodynamic functions and simulation results. Thermodynamic properties of dry air were used to illustrate the impact of discontinuities on the thermodynamic functions whereas steady detonation simulation and constant volume reactor simulation were performed to discuss the impact of the discontinuities on combustion modeling. We show that the accuracy of the solution can be decreased by up to several percents. In addition, an increase of computation cost is induced in the vicinity of the discontinuities when adaptive time-stepping is adopted in the simulation. A correlation previously proposed in the literature to remove the discontinuity issue was tested and proved efficient to limit the decrease of the time-step. • Discontinuities exist in thermo-properties calculated with some cubic equations of state. • Discontinuous thermo-properties decrease the accuracy of detonation simulation. • Discontinuous thermo-properties increase the computational cost of combustion simulation. [ABSTRACT FROM AUTHOR]

Singlet fission can generate an exchange-coupled quintet triplet pair state 5TT, which could lead to the realization of quantum computing and quantum sensing using entangled multiple qubits even at room temperature. However, the observation of the quantum coherence of 5TT has been limited to cryogenic temperatures, and the fundamental question is what kind of material design will enable its room-temperature quantum coherence. Here, we show that the quantum coherence of singlet fission-derived 5TT in a chromophore-integrated metal-organic framework can be over hundred nanoseconds at room temperature. The suppressed motion of the chromophores in ordered domains within the metal-organic framework leads to the enough fluctuation of the exchange interaction necessary for 5TT generation but, at the same time, does not cause severe 5TT decoherence. Furthermore, the phase and amplitude of quantum beating depend on the molecular motion, opening the way to room-temperature molecular quantum computing based on multiple quantum gate control. [ABSTRACT FROM AUTHOR]

Herein, the ground-state properties of the intermetallic compound NdPd and its magnetic observable curves as well as its magnetocaloric properties have been investigated using a combined Monte Carlo simulation and ab initio calculations. The calculated magnetic moment of Nd atom is 3.11 μB which is in agreement with the experimental one. Furthermore, it was established that the first two exchange couplings for Nd-Nd interactions present positive signs ( J 1 = 1.593 meV and J 2 = 0.358 meV), where both correspond to ferromagnetic interactions. In good agreement with recent experimental works, the simulation results revealed that the NdPd compound orders ferromagnetically at T c =16 K. It was moreover found that the isothermal magnetic entropy around the Curie temperature and the relative cooling power (RCP) in an applied magnetic field of 5 T are acceptable concurrence with those obtained in the laboratory. Besides, the good magnetocaloric properties of NdPd obtained here are quite convincing to predict that NdPd-based magnetic refrigeration can be considered a promising technology for cryogenic cooling systems within the range T < 20 K. [ABSTRACT FROM AUTHOR]

The skin's protective mechanisms, in some cases, are not able to counteract the destructive effects induced by UV radiations, resulting in dermatological diseases, as well as skin aging. Nutlin-3, a potent drug with antiproliferative activity in keratinocytes, can block UV-induced apoptosis by activation of p53. In the present investigation, ethosomes and transethosomes were designed as delivery systems for nutlin-3, with the aim to protect the skin against UV damage. Vesicle size distribution was evaluated by photon correlation spectroscopy and morphology was investigated by cryogenic transmission electron microscopy, while nutlin-3 entrapment capacity was evaluated by ultrafiltration and HPLC. The in vitro diffusion kinetic of nutlin-3 from ethosomes and transethosomes was studied by Franz cell. Moreover, the efficiency of ethosomes and transethosomes in delivering nutlin-3 and its protective role were evaluated in ex vivo skin explants exposed to UV radiations. The results indicate that ethosomes and transethosomes efficaciously entrapped nutlin-3 (0.3% w/w). The ethosome vesicles were spherical and oligolamellar, with a 224 nm mean diameter, while in transethosome the presence of polysorbate 80 resulted in unilamellar vesicles with a 146 nm mean diameter. The fastest nutlin-3 kinetic was detected in the case of transethosomes, with permeability coefficients 7.4-fold higher, with respect to ethosomes and diffusion values 250-fold higher, with respect to the drug in solution. Ex vivo data suggest a better efficacy of transethosomes to promote nutlin-3 delivery within the skin, with respect to ethosomes. Indeed, nutlin-3 loaded transethosomes could prevent UV effect on cutaneous metalloproteinase activation and cell proliferative response. [ABSTRACT FROM AUTHOR]

The fundamental limits of the microwave noise performance of high electron-mobility transistors (HEMTs) are of scientific and practical interest for applications in radio astronomy and quantum computing. Self-heating at cryogenic temperatures has been reported to be a limiting mechanism for the noise, but cryogenic cooling strategies to mitigate it, for instance, using liquid cryogens, have not been evaluated. Here, we report microwave noise measurements of a packaged two-stage amplifier with GaAs metamorphic HEMTs immersed in normal and superfluid 4 He baths and in vacuum from 1.6 to 80 K. We find that these liquid cryogens are unable to mitigate the thermal noise associated with self-heating. Considering this finding, we examine the implications for the lower bounds of cryogenic noise performance in HEMTs. Our analysis supports the general design principle for cryogenic HEMTs of maximizing gain at the lowest possible power. [ABSTRACT FROM AUTHOR]

We measured the solid–liquid–vapor (SLV) equilibrium of binary mixtures during experiments that alternated between cooling the mixture and injecting the more-volatile component into the sample chamber; thus, the composition of the mixture changed (non-isoplethic) throughout the experiment. Four binary mixtures were used in the experiments to represent mixtures with miscible solid phases (N2/CO) and barely miscible solid solutions (N2/C2H6), as well as mixtures with intermediate solid miscibility (N2/CH4 and CO/CH4). We measured new SLV pressure data for the binary mixtures, except for N2/CH4, which are also available in the literature for verification in this work. While these mixtures are of great interest in planetary science and cryogenics, the resulting pressure data are also needed for modeling purposes. We found the results for N2/CH4 to be consistent with the literature. The resulting new SLV curve for CO/CH4 shows similarities to N2/CH4. Both have two density inversion points (bracketing the temperature range where the solid floats). This result is important for places such as Pluto, Triton, and Titan, where these mixtures exist in vapor, liquid, and solid phases. Based on our experiments, the presence of a eutectic is unlikely for the N2/CH4 and CO/CH4 systems. An azeotrope with or without a peritectic is likely, but further investigations are needed to confirm. The N2/CO system does not have a density inversion point, as the ice always sinks in its liquid. For N2/C2H6, new SLV pressure data were measured near each triple point of the pure components. [ABSTRACT FROM AUTHOR]

Particle-in-cell (PIC) simulations are a widely-used tool to model kinetics-dominated plasmas in ultrarelativistic laser-solid interactions (dimensionless vectorpotential a0 > 1). However, interactions approaching subrelativistic laser intensities (a0 ≲ 1) are governed by correlated and collisional plasma physics, calling for benchmarks of available modeling capabilities and the establishment of standardized testbeds. Here, we propose such a testbed to experimentally benchmark PIC simulations of laser-solid interactions using a laser-irradiated micron-sized cryogenic hydrogen-jet target. Time-resolved optical shadowgraphy of the expanding plasma density, complemented by hydrodynamics and ray-tracing simulations, is used to determine the bulk-electron-temperature evolution after laser irradiation. We showcase our testbed by studying isochoric heating of solid hydrogen induced by laser pulses with a dimensionless vectorpotential of a0 ≈ 1. Our testbed reveals that the initial surface-density gradient of the target is decisive to reach quantitative agreement at 1 ps after the interaction, demonstrating its suitability to benchmark controlled parameter scans at subrelativistic laser intensities. Relativistic laser-solid interactions are simulated via particle-in-cell (PIC) approaches, while subrelativistic regimes rely on radiation-hydrodynamics formulations. To validate the methods at the transition from relativistic to subrelativistic laser intensities, the authors propose a testbed to experimentally benchmark PIC simulations. [ABSTRACT FROM AUTHOR]

We introduce a design modification to conventional geometry of the cryogenic three-terminal switch, the nanocryotron (nTron). The conventional geometry of nTrons is modified by including parallel current-carrying channels, an approach aimed at enhancing the device's performance in magnetic field environments. The common challenge in nTron technology is to maintain efficient operation under varying magnetic field conditions. Here, we show that the adaptation of parallel channel configurations leads to an enhanced gate signal sensitivity, an increase in operational gain, and a reduction in the impact of superconducting vortices on nTron operation within magnetic fields up to 1 T. Contrary to traditional designs that are constrained by their effective channel width, the parallel nanowire channels permits larger nTron cross sections, further bolstering the device's magnetic field resilience while improving electro-thermal recovery times due to reduced local inductance. This advancement in nTron design not only augments its functionality in magnetic fields but also broadens its applicability in technological environments, offering a simple design alternative to existing nTron devices. [ABSTRACT FROM AUTHOR]

Titanomagnetite containing up to 0.6–0.7 Ti atoms per formula unit is a primary magnetic mineral phase in submarine basalts and in some terrestrial volcanic rocks. On a geological timescale, it often undergoes alteration, forming new magnetic phases that may acquire (thermo)chemical remanent magnetization. The initial stage of this natural process can be modelled by prolonged laboratory annealing at moderately elevated temperatures. In this study, our goal is to characterize the alteration products resulting from annealing a submarine basalt containing homogeneous titanomagnetite Fe3−x Ti x O4 (x  ≈ 0.46) at temperatures of 355, 500 and 550 °C for up to 375 hr, by examining their magnetic properties over a wide range of temperatures. The effect of extended annealing is most apparent in the low-temperature magnetic properties. In the fresh sample, a magnetic transition is observed at 58 K. Below the transition temperature, the field-cooled (FC) and zero-field-cooled (ZFC) saturation isothermal remanent magnetization (SIRM) curves are separated by a tell-tale triangular-shaped area, characteristic for titanomagnetites of intermediate composition. The room-temperature SIRM (RT-SIRM) cycle to 1.8 K in zero field has a characteristic concave-up shape and is nearly reversible. For the annealed samples, the magnetic transition temperature shifts to lower temperatures, and the shape of the curves above the transition changes from concave-up to concave-down. The shape of the RT-SIRM cycles also progressively changes with increasing annealing time. The SIRM loss after the cycle increases up to ∼30 per cent for the samples annealed for 375 hr at 355 °C, and for 110 hr at 500 and 550 °C. The Curie temperatures of the newly formed magnetic phases exceed the Curie temperature of the fresh sample (205 °C) by up to 350 °C. While this effect is most commonly attributed to extensive single-phase oxidation (maghemitization), the behaviour observed at cryogenic temperatures appears incompatible with the known properties of highly oxidized titanomaghemites. Therefore, we propose that, at least in the initial stage of the 'dry', that is, not involving hydrothermalism, alteration of titanomagnetite, temperature- and time-controlled cation reordering is the primary mechanism driving changes in both low- and high-temperature magnetic properties. [ABSTRACT FROM AUTHOR]

Rigid polyurethane (PUR) foams have been the most effective insulation material used in space launchers since the beginning of cryogenic fuel use, due to their outstanding thermal and mechanical properties. In this study, spray-applied PUR foams using different ratios of amine-based catalysts were produced. Due to climate change, several restrictions have been made regarding the usage of blowing agents used for PUR foam production. Lately, hydrofluoroolefins (HFOs) have been suggested as an alternative for PUR foam production due to their low global warming potential (GWP) and ozone depletion potential (ODP), replacing the hydrofluorocarbons (HFCs) so far used. This change in blowing agents naturally altered the usage of catalysts. Reactive amine-based catalysts are less hazardous because of their low volatility and ability to react successfully with isocyanate or polyols. Spray-applied PUR foams with a potential application for cryogenic insulation were produced and tested for long-term storage, analyzing parameters such as the pH value of polyol composition, foaming kinetics (trise, tcream), etc. Athermal analysis (TG, DSC) was also applied to developed materials, as well as artificial ageing by exposing samples to UV light. It was discovered that PUR foams obtained using reactive amine-based catalysts, such as Polycat 203 and 218, have a higher integral heat capacity, but polyol mixtures containing these catalysts cannot exceed a storage time of more than 4 months. It was also observed from artificial ageing tests of PUR cryogenic insulation by exposure to UV light that the thickness of the degraded layer reached 0.8 mm (after 1000 h), but no significant destruction of cellular structure deeper in the material was observed. [ABSTRACT FROM AUTHOR]

Electromagnetic noise is one of the main external factors decreasing superconducting qubit coherence. Matched coaxial filters can prevent microwave and IR photons' negative influence on superconducting quantum circuits. In this report, we describe the design and fabrication process of matched coaxial filters for noise-sensitive measurements at millikelvin temperatures. A robust transmission coefficient and ultralow reflection loss of −20 dB in the frequency range up to 20 GHz is achieved. Fabricated low-pass filters have linear transmission and reflection characteristics with 3 dB-cutoff frequency of 1.5–2.5 GHz. A method for extracting the propagation constant and filter impedance from scattering parameter measurements is demonstrated. This method is experimentally approved on a filter with a compound of Cu powder and Stycast epoxy resin and a filter filled with ECCOSORB CR-110 epoxy resin. The proposed design and assembly technology are versatile for various compounds and provide highly repeatable geometric and microwave characteristics. Furthermore, we demonstrate that these low-pass coaxial filters can be effectively utilized to improve superconducting qubit relaxation due to suppressing standing waves originating from reflections in control coaxial cables. [ABSTRACT FROM AUTHOR]

We explore the axionic dark matter search sensitivity with a narrow-band detection scheme aimed at the axion-photon conversion by a static electric field inside a cylindrical capacitor. An alternating magnetic field signal is induced by effective currents as the axion dark matter wind flows perpendicularly through the electric field. At low axion masses, such as in a KKLT scenario, front-end narrow band filtering is provided by using LC resonance with a high Q factor, which enhances the detectability of the tiny magnetic field signal and leads to thermal noise as the major background that can be reduced under cryogenic conditions. We demonstrate that high g a γ sensitivity can be achieved by using a strong electric field E ∼ MVm - 1 . The QCD axion theoretical parameter space would require a high E ∼ GVm - 1 field strength. Using the static electric field scheme essentially avoids exposing the sensitive superconducting pickup to an applied laboratory magnetic field. [ABSTRACT FROM AUTHOR]

We have conceived, built, and operated a cryogenic vacuum valve with opening and closing times as short as 50 ms that can be used in strong magnetic fields and across a broad range of duty cycles. It is used to seal a cryogenic Penning trap at liquid-helium temperature for long-term storage of highly charged ions in a vacuum better than 10−15 hPa from a room-temperature ion beamline at vacuum conditions around 10−9 hPa. It will significantly improve any experiment where a volume at the most extreme vacuum conditions must be temporarily connected to a less demanding vacuum during repeated experimental cycles. We describe the design of this valve and show measurements that characterize its main features. [ABSTRACT FROM AUTHOR]

Currently, the world's only source of low-energy antiprotons is the AD/ELENA facility located at CERN. To date, all precision measurements on single antiprotons have been conducted at this facility and provide stringent tests of fundamental interactions and their symmetries. However, magnetic field fluctuations from the facility operation limit the precision of upcoming measurements. To overcome this limitation, we have designed the transportable antiproton trap system BASE-STEP to relocate antiprotons to laboratories with a calm magnetic environment. We anticipate that the transportable antiproton trap will facilitate enhanced tests of charge, parity, and time-reversal invariance with antiprotons and provide new experimental possibilities of using transported antiprotons and other accelerator-produced exotic ions. We present here the technical design of the transportable trap system. This includes the transportable superconducting magnet, the cryogenic inlay consisting of the trap stack and detection systems, and the differential pumping section to suppress the residual gas flow into the cryogenic trap chamber. [ABSTRACT FROM AUTHOR]

This paper reviews the 40-year evolution and application of the magnetic suspension balance (MSB) and discusses some challenging issues of the technique. An MSB, as defined herein, is a magnetic suspension coupling (MSC) connected to an analytical balance. With an MSC, an object can be weighed in a different environment than the balance itself, making it possible for contactless weighing. Over the past 40 years, the MSB has been commonly used in research areas requiring accurate object weighings, notably gas density measurements by MSB-based densimeters and gas adsorption measurements by MSB-based sorption analyzers. More than 15 MSB-based densimeters have been built to date; these are generally called two-sinker densimeter and single-sinker densimeter. They have produced highly accurate density data of many pure fluids and fluid mixtures. These data serve as the basis for the development of reference equations of state, which play an essential role in various industrial and scientific areas. Moreover, such systems are central to the metrology program of many countries. The MSB technique is also very successful in adsorption science: more than 85 MSB-based sorption analyzers have been set up in over 20 countries. The number of new MSB-based sorption analyzers, and peer-reviewed publications resulting from them, are both increasing exponentially since 2004. They have produced highly reliable gas adsorption data at high pressures for many applications, mainly in the energy and environmental sectors. Although further development of innovative instruments based on the MSB is threatened by the proprietary nature of MSB technology, the development will continue, e.g., toward cryogenic measurements and a more compact design. [ABSTRACT FROM AUTHOR]

The Potsdam Arrayed Waveguide Spectrograph (PAWS) is based on an integrated photonic spectrograph designed and developed by innoFSPEC to work in the astronomical H‐band. PAWS demonstrates how a traditional bulk optics spectrograph can be miniaturized and additionally serves as a tool for testing in‐house developed astrophotonical devices. The main element is a second‐generation Arrayed Waveguide Grating (AWG) with unprecedented performance in terms of spectral resolution and throughput that is fiber‐coupled and works as a first dispersive component. The pre‐dispersed light is fed into a free‐space optical system located in a cryostat, where the overlapping spectral orders are separated by cross‐dispersion. The resulting echellogram is recorded by a Teledyne 2k×2k H2RG near‐infrared array. Once the cryogenic cross‐dispersion optics inside the vacuum chamber were appropriately aligned to the AWG coupling optics outside of the chamber, different light sources were used to test the functionality of the complete system. A tunable laser source was used to create an echellogram through frame stacking. Additionally, the cross‐dispersed output of a supercontinuum source was recorded using different input waveguides of the AWG, and first light was achieved with laboratory measurements. PAWS represents a pioneering demonstration of an astronomy‐optimized AWG chip, exhibiting the advantageous capabilities of integrated photonic spectrographs, in particular in the context of space applications. [ABSTRACT FROM AUTHOR]