Cryogenic Temperature Sensors Research Articles

Ultra-sensitive low-temperature luminescent thermometry based on Boltzmann behavior of the Stark sub-levels of Pr3+

The cryogenic sensor is critical for numerous applications such as cryobiology, aerospace space probes, and solid-state superconducting quantum technology. However, it is still a challenge to operate at temperatures below 100 K using luminescent intensity ratio (LIR) thermometers with typical thermal coupling levels based on the Boltzmann mechanism. In this work, a sensitive low-temperature luminescence thermometry approach has been developed utilizing Boltzmann behavior of the Stark sub-levels of Pr3+. Spectral Stark-splitting feature of the 1D2 multiplet of Pr3+ was observed in CaNb2O6: Pr3+ phosphor, and the luminescence intensity ratio (LIR) of high state (Stark sub-level (2)) and low state (Stark sub-level (0)) of 1D2 was employed for temperature sensing, resulting in a notable relative sensitivity (Sr) of 11.3 % K−1 at 60 K. In addition, the intervalence charge transfer (IVCT)-based strategy improves the temperature sensitivity above room temperature with maximum Sr up to 1.54 % K−1 at 420 K. This work consistently demonstrate high sensitivity at low temperature, indicating potential applications in cryogenic temperature sensor. These results provide a route to the development of luminescent thermometers with a high sensitivity at low temperatures and a wide range of operating temperatures.

Processing calibration data of low-temperature thermometer based on clustering algorithm.

The scarcity of cryogenic thermometers often stems from their high cost and lengthy lead times for calibration. Establishing an in-lab temperature calibration system is necessary to quickly make use of uncalibrated sensors or self-made sensors. This paper introduces a straightforward and high-accuracy thermometer calibration system. By employing copper screws as thermal links between the sensor platform and the cryogen-free refrigerator, temperature oscillation on the sensor platform is suppressed to a few millikelvins. In addition, this paper presents a data processing model based on clustering algorithms. These algorithms sort and group data based on distance, which is similar to human visual judgment of data. This paper discusses the parameter optimization process of the clustering algorithm to interpret the automated data process. The cryogenic temperature sensors calibrated by this system exhibited high accuracy, with relative errors of less than 1% compared to standard thermometers. Moreover, automatically processing calibration data from two uncalibrated thermometers takes just over 10min, highlighting the effectiveness of this calibration system.

Interfacial compatible PolyMOF membranes as ratiometric fluorescence temperature sensors

Cryogenic temperature sensors play significant roles in manufacturing, metallurgy, and aerospace. Metal-organic frameworks (MOFs) as emerging crystal materials exhibited inherent advantages as fluorescence temperature sensors and researchers have shifted their focus toward incorporating MOFs materials into mixed matrix membranes (MMMs) for broader practical applications. However, the poor interfacial compatibility between MOFs particles and the polymer matrix would cause aggregation-induced fluorescence quenching and reduced energy transfer efficiency, thereby compromising temperature sensing performances. Herein, we adopt a post-synthetic copolymerization strategy to realize an interfacial-compatible membranous ratiometric luminescent thermometer based on the emissions of ligands and lanthanide ions. Benefiting from the controllable covalent cross-linking structures, the designed polyMOF membrane exhibited excellent interfacial compatibility and avoided MOFs irregular morphology agglomeration and phase separation, which contributed to outstanding fluorescence temperature sensing performance with excellent sensitivity ranging from 0.300 to 0.745 %·K−1 within the temperature range of 80–300 K, superior to recent reported MOFs-based thermometers. This research presents a promising approach for the design and fabrication of interfacial compatible MOFs-based membranes with excellent fluorescence temperature sensing properties, advancing the understanding of structure-property relationships and accelerating the practical applications.

Diamond with Sp2-Sp3 composite phase for thermometry at Millikelvin temperatures

Temperature is one of the seven fundamental physical quantities. The ability to measure temperatures approaching absolute zero has driven numerous advances in low-temperature physics and quantum physics. Currently, millikelvin temperatures and below are measured through the characterization of a certain thermal state of the system as there is no traditional thermometer capable of measuring temperatures at such low levels. In this study, we develop a kind of diamond with sp2-sp3 composite phase to tackle this problem. The synthesized composite phase diamond (CPD) exhibits a negative temperature coefficient, providing an excellent fit across a broad temperature range, and reaching a temperature measurement limit of 1 mK. Additionally, the CPD demonstrates low magnetic field sensitivity and excellent thermal stability, and can be fabricated into probes down to 1 micron in diameter, making it a promising candidate for the manufacture of next-generation cryogenic temperature sensors. This development is significant for the low-temperature physics researches, and can help facilitate the transition of quantum computing, quantum simulation, and other related technologies from research to practical applications.

High precision temperature measurement for cryogenic temperature sensors based on deep learning technology

Nonlinear error compensation is a significant factor that affects the measurement accuracy of temperature sensors. Cryogenic temperature sensors require a precise calibration technique to achieve accurate temperature measurements. BP (Back Propagation) neural networks are not suitable for sensor temperature prediction due to slow convergence and poor learning ability. In this study, a Chebyshev polynomial-based BiLSTM (Bi-directional Long Short-Term Memory) algorithm (C-BiLSTM) is proposed to improve the accuracy of measurement. Firstly, we demonstrate vacuum packaged temperature sensors based on zirconium oxynitride (ZrOxNy) thin films with ultra-high sensitivity at cryogenic temperatures. Secondly, a dataset consisting of sensor resistance and temperature values was obtained from five above-mentioned sensors, which contains 29 calibration points in the temperature range of 16 K-300 K measured by the Calibration System. Then, the dataset was divided into two temperature ranges (16 K-54.358 K and 40 K-300 K). In the range 16–54.358 K, 14 set-points are selected as training set and 3 set-points as testing set. In the range 40–300 K, 12 set-points are selected as training set and 2 set-points as testing set. Thirdly, a neural network model was built and trained using the TensorFlow framework. By comparing C-BiLSTM we proposed with the BP neural network and BiLSTM, the results show that the C-BiLSTM model converges faster and greatly improves the prediction accuracy after adding Chebyshev polynomial features. The fitting error and prediction error are less than 1 mK in the temperature range of 16 K-40 K. They can also keep less than 10 mK even at the wide temperature range of 40 K-300 K, which is a significant improvement respect to improving the accuracy of temperature measurement.

Development of an Indigenous Cryogenic Temperature Sensors Calibration Facility for Cryogenic and Semicryogenic Rocket Engines

Development of an Indigenous Cryogenic Temperature Sensors Calibration Facility for Cryogenic and Semicryogenic Rocket Engines

Cernox thermometer under hydrostatic pressure for enhanced temperature accuracy

Sensors that can be used in a pressurized environment are few. Thus, it is generally considered that the accuracy of temperature measurements decreases in experiments carried out under pressure. Based on a commercially available cryogenic temperature sensor, Cernox from Lake Shore Cryotronics, Inc., we developed and tested an enclosure that enables Cernox to be directly used inside a cylindrical pressure cell, next to the specimen under investigation. To isolate the Cernox thermometer from the pressurized medium inside the pressure cell, we combined the principles of an encapsulated Pt sensor and a cylindrical clamped piston cell. The encapsulated Cernox allows for precise measurement and control of the specimen’s temperature. It is also beneficial for accurately determining small changes in physical properties, such as temperature, or measuring the amount of hysteresis in the first-order phase transition. It would also be useful for accurately controlling the sample’s temperature when the sample approaches the transition temperature from one side.

Stability of Cernox® temperature sensors stored at room temperature over a 29-year period

Many cryogenic applications critically depend upon accurate temperature measurement for success. In certain applications, including aerospace missions, temperature sensor components are procured years in advance of the mission’s launch date in order to accommodate installation and ground-based testing. Once installed there is little opportunity for recalibration, so the stability of the sensor stored at room temperature over extended time periods becomes vitally important. One of the most common cryogenic temperature sensor types used in aerospace applications is the Cernox Resistance Temperature Sensor manufactured by Lake Shore Cryotronics, Inc., and has been commercially available since 1993. For 29 years a set of 35 sensors manufactured from two of the initial production wafers has been stored at room temperature in ambient atmosphere. These sensors have been periodically recalibrated over the 1.4 K to 325 K or 4 K to 325 K temperature range as appropriate to provide an estimate of the long-term stability of these sensors when stored at room temperature. Data for each temperature sensor were analyzed in terms of equivalent temperature shift between each subsequent calibration and its initial calibration in 1992. The data show that the overall 29-year average stability for devices from these two Cernox wafers roughly follows a stability of ±10 mK for temperatures below 10 K and 0.07% of temperature for temperatures above 10 K. Data for an additional nine Cernox devices from an actual JWST production build lot showed they all exhibited stabilities better than ±8 mK for T < 10 K and (ΔT/T) < ±0.075% for T > 10 K.

High Sensitivity Cryogenic Temperature Sensors Based on Arc-Induced Long-Period Fiber Gratings.

In this paper, we investigated the evolution of the dispersion curves of long-period fiber gratings (LPFGs) from room temperature down to 0 K. We considered gratings arc-induced in the SMF28 fiber and in two B/Ge co-doped fibers. Computer simulations were performed based on previously published experimental data. We found that the dispersion curves belonging to the lowest-order cladding modes are the most affected by the temperature changes, but those changes are minute when considering cladding modes with dispersion turning points (DTP) in the telecommunication windows. The temperature sensitivity is higher for gratings inscribed in the B/Ge co-doped fibers near DTP and the optimum grating period can be chosen at room temperature. A temperature sensitivity as high as −850 pm/K can be obtained in the 100–200 K temperature range, while a value of −170 pm/K is reachable at 20 K.

Ultrasensitive Cryogenic Temperature Sensor Based on a Metalized Optical Fiber Fabry-Perot Interferometer

Cryogenic technologies are becoming essential in future applications in aerospace, quantum computing, cryogenic computing, and superconducting research. A highly sensitive temperature sensor is critical for such cryogenic applications. In this paper, we propose an extrinsic Fabry–Perot interferometer (EFPI) for cryogenic temperature measurement, leveraging the high thermal deformation of the copper sleeve to overcome the sensitivity drop issue in temperatures below 50 K for conventional cryogenic temperature sensors. Experimental results exhibit a temperature sensitivity of 2.836 nm/K throughout a temperature range of 5 K-50 K with a 15.82 μm long EFPI cavity, which is over three orders higher than the recently reported metal-coated FBG. The high sensitivity holds for the entire temperature range from 5 K to 295 K with excellent sensing repeatability. Our device, featuring a compact structure, and capability for multiplexing, is with great promise in cryogenic applications.

Thermometry in dual quantum dot setup with staircase ground state configuration

We propose and investigate thermometry of a setup employing dual quantum dots with staircase ground state configuration. The stair-case ground state configuration actuates thermally controlled inelastic tunnelling, which translates into a temperature sensitive conductance, thereby inducing thermometry. The performance of the set-up is then analyzed employing quantum master equation (QME) for such systems in the sequential tunnelling regime. In particular, it is demonstrated that the system performance, in terms of temperature sensitivity and efficiency, is maximum in the regime of low temperature, making such system suitable for cryogenic thermometry. The proposed set-up can pave the path towards realization of high performance cryogenic nano temperature sensors.

Fluorescence optimization and ratiometric thermometry of near-infrared emission in erbium/oxygen-doped crystalline silicon

Crystalline Si (c-Si) implanted with rare-earth erbium (Er) might offer a solution to the development of silicon-based optical amplifiers and lasers at communication wavelengths for integrated silicon photonics. However, Er doped (often with oxygen) c-Si traditionally suffers from a strong thermal quenching effect in luminescence, resulting in extremely low luminous efficiency. We recently adopted a deep cooling process to treat Er/O co-doped c-Si samples. After the treatment, the thermal quenching effect is suppressed and the room-temperature photoluminescence (PL) is improved by two orders of magnitude. In this work, we report the PL optimization by tuning parameters including annealing temperature and time, deep cooling rate, O and Er concentration, and their ratio. It was found that the PL performance is maximized at O:Er concentration ratio of ∼2.5 and annealing temperature of 950 °C for 5 min followed by a cooling rate as fast as −500 °C s−1. In addition, the Er/O emission has two spectrally-resolved peaks at 6472 cm−1 and 6510 cm−1 and their intensity ratio is independent of excitation power but a linear function of temperature. This unique property, likely originated from the physics of Er, Si, and O chemical composites formed in the deep cooling process, allows us to develop reliable cryogenic temperature sensors with an accuracy of ±1.0 K in the 4–200 K range.

Design, development, and qualification tests of prototype two-channel cryogenic temperature transmitter

A two-channel prototype cryogenic temperature transmitter is developed using an ARM Cortex-M3 series precision analog microcontroller using a rapid prototyping method for use in indigenous developments. The developed prototype utilizes an Arduino compatible baseboard equipped with interfaces for programming/debugging. Additional circuits are fabricated, and embedded application software is developed and tested. The input circuit consists of a low-value high accuracy precision current source to excite the cryogenic temperature sensors of Resistance Temperature Detector (RTD) type and employs a standard four-wire ratiometric measurement technique for accurate resistance measurement. The ratiometric measurement eliminates measurement errors due to current uncertainty. The precision microcontroller is equipped with internal programmable gain amplifiers to accurately scale low-level analog signals from cryogenic temperature sensors. The developed transmitter can interface with two cryogenic RTDs (Cernox® and PT-100 types) and can accurately measure resistance over its calibrated range (300–4 K). The cubic spline interpolation method is employed in application software for converting the measured resistance to temperature. The measured temperature is transmitted to a programmable logic device (via 4–20 mA signals) using the pulse width modulation technique. The developed transmitter is tested for its performance against commercially available transmitters at the liquid nitrogen temperature, liquid helium temperature, and over the entire measurement range using Gifford–McMahon type cryocoolers. The developed transmitter was utilized to assess the impact of the thermal resistance of the cryogenic sensors at the lowest temperature of the cryocooler (∼2.6 K). This paper outlines design details, application software development, experimental setup, measurement uncertainties, and test results.

Cryogenic temperature sensing based on the temperature dependence of color centers in optical fibers.

A cryogenic temperature sensor based on the temperature dependence of stable color centers in a commercial single-mode optical fiber is proposed. The radiation induced attenuation spectra at different temperatures are measured and decomposed by Ge-NBOHC and Ge(X) color centers. The configurational coordinate model is used to explain the temperature properties of the color centers. A series of experiments are conducted to evaluate its performance in the temperature range from 10°C to -196°C, and the results suggest that the temperature sensitivity is ∼0.17 dB/km/°C with a resolution of 0.034°C, and the nonlinearity and repeatability error are ±3.8% and 1.4%, respectively.

Micrometer Sized Hexagonal Chromium Selenide Flakes for Cryogenic Temperature Sensors.

Nanoscale thermometers with high sensitivity are needed in domains which study quantum and classical effects at cryogenic temperatures. Here, we present a micrometer sized and nanometer thick chromium selenide cryogenic temperature sensor capable of measuring a large domain of cryogenic temperatures down to tenths of K. Hexagonal Cr-Se flakes were obtained by a simple physical vapor transport method and investigated using scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy measurements. The flakes were transferred onto Au contacts using a dry transfer method and resistivity measurements were performed in a temperature range from 7 K to 300 K. The collected data have been fitted by exponential functions. The excellent fit quality allowed for the further extrapolation of resistivity values down to tenths of K. It has been shown that the logarithmic sensitivity of the sensor computed over a large domain of cryogenic temperature is higher than the sensitivity of thermometers commonly used in industry and research. This study opens the way to produce Cr-Se sensors for classical and quantum cryogenic measurements.

Magnetoelastic resonance of magnetic amorphous alloys at cryogenic temperatures

We report on the low temperature (T = 10 K) magnetoelastic resonance in ribbons of magnetic amorphous alloys, with the goal of assessing their potential for cryogenic temperature sensors. The resonance frequency was found to be nearly temperature independent below T≈150 K, while the amplitude continues to increase upon cooling over the entire temperature range. Furthermore, the magnetic field dependence of the resonant frequency at low (10 K) and high temperatures (300 K) are very similar, suggesting great potential for developing sensors with high stability level over a broad temperature range, especially in the cryogenic regime.

Study of fiber Bragg gratings with TiN-coated for cryogenic temperature measurement

In this study, single metal-coated Fiber Bragg grating (FBG) sensors and bare FBG sensors were placed in an aluminum alloy mold, which were in turn packaged in a thermal insulation container to monitor the temperature response, and used as cryogenic temperature sensors. Specifically, the performance of titanium nitride (TiN)-coated FBG sensors in cryogenic temperature environments was evaluated. Using an optical spectrum analyzer (OSA), the reflection spectra of the TiN-coated FBG sensors were measured and compared with those of bare FBG for temperatures ranging from 25 to −195 °C. The results showed that the TiN-coated FBG exhibited a temperature sensitivity of 10.713 pm/°C and R-squared value of 0.995. The TiN-coated on the FBG altered the non-linear characteristics of the thermo-optic and thermal expansion coefficients of the FBG. Through this research to get thermo-optic coefficient (ξ = 5.12 × 10−6) and thermal expansion coefficient (α = 1.81 × 10−6) and resulted in more precise measurements at cryogenic temperature.

Magnetoresistance Behavior of Cryogenic Temperature Sensors Based on Single-Walled Carbon Nanotubes

We report on the experimental investigation of the magnetoresistance behavior of cryogenic temperature sensors based on single-walled carbon nanotubes (SWCNTs) as a function of temperature and magnetic flux density; one sensor was based on layers/networks of unsorted SWCNT of various chiralities, and one on SWCNTs layers of (7,6) chirality. SWCNT-based sensors were fabricated according to a straightforward method, and the electrical properties were measured from room temperature down to 2 K using a Quantum Design Physical Property Measurement System (PPMS). The two sensors present different magneto-transport behavior, with the magnetoresistance dependence on the magnetic field being a sum of two terms with positive and negative contributions respectively. The expression for magnetoresistance is derived together with its experimentally determined coefficients. For both sensors, the electrical resistance dependence on temperature below the 80 K mark is explained by Mott's law of variable-range hopping. The experimentally obtained hopping dimension d values of 2.67 for the system comprised of purified (7,6) chirality SWCNTs and 2.97 for the system comprised of unsorted SWCNTs are in good agreement with the theory. As a second step, the magnetic field was kept constant and at different values, while the temperature was scanned over the investigated domain.

Study of Calorimetric Self-Field AC Loss Measurement of HTS Stacks Using FBG Sensors

AC loss plays an important role in the design of the device employing HTS magnet. Therefore, it is important to measure the AC loss in HTS magnet. In this work, we studied the calorimetric self-field AC loss measurement of a four-tape HTS stacks using Fiber Bragg Grating (FBG) sensors. Three cryogenic FBG temperature sensors with different coating and installation were selected for the AC loss measurement. The calibration between power loss and wavelength shift was carried out by a resistance heater before the AC loss measurement. With the calibrated FBG sensors, the AC loss measurement was measured at 67 Hz and 89 Hz. These measurements were carried out at 77 K through conduction cooling by sealing the sample in a thermal insulator. The measured loss results were verified through comparison with the Norris models as well as the electrical measurements of AC loss. Finally, the magnetic strain effect on loss measurement was evaluated experimentally. The results in our paper shows that the calorimetric method based on the proposed FBG sensor can be used for the AC loss measurement of a four-tape HTS stack, and the magnetic strain of a four-tape stack has no effect on the AC loss measurement, which provides the possibility of using FBG sensors for ac loss measurement on HTS stacks.

Study of optical fiber cryogenic temperature sensor for quench detection of high temperature superconductors.

In this study, a new processing design of an optical fiber cryogenic temperature sensor (OFCTS) is presented. The sensing unit is constituted by NaYF4:Yb3+, Er3+@NaYF4 core-shell upconversion nanocrystals-polymethyl methacrylate (UCNCs-PMMA) nanocomposites. The coupling is achieved by fiber fusion in the embodiment. The relative sensitivity of the OFCTS can reach the maximal value 13.241×10-3 K-1 at 80 K in a cryogenic environment, and stability is good with a standard deviation of 0.012. Research results show that the proposed OFCTS has good temperature responses at the cryogenic environment, and has a great potential of the superconducting application for generator, transmission line, maglev train and quantum interferometer.