Low Noise Temperature Research Articles

Modeling of the effect of ionomer volume fraction on water management for proton exchange membrane fuel cell

Proton exchange membrane fuel cell (PEMFC) has been recognized as the most promising energy conversion device due to its outstanding merits, such as high energy efficiency, low pollution, low operating temperature and low noise. Due to the complicated process of water production and transportation in porous media, the water concentration can affect the distribution of species and ionic conductivity, thus, the water management has been regarded as one of the most critical issues for PEMFC. In this paper, a three dimensional multiphase non-isothermal model for the PEMFC performance prediction has been developed to study the effect of ionomer volume fraction on the performance of PEMFC. The numerical results show that the ionomer volume fraction of catalyst layer has an appreciable effect on the performance of PEMFC and water distribution in porous electrodes, the higher ionomer volume fraction in catalyst layer can be helpful to avoid the flooding problem in porous electrodes.

Low-Temperature Noise Performance of SuperSpec and Other Developments on the Path to Deployment

SuperSpec is a compact on-chip spectrometer operating at mm and sub-mm wavelengths which will enable the construction of sensitive multibeam spectrometers. SuperSpec employs a filter bank architecture, consisting of lithographically patterned niobium superconducting microstrip mm-wave resonators. The power admitted by each resonator is detected by a titanium nitride lumped-element kinetic inductance detector (KID) with resonant frequency from 100 to 200 MHz. We present a characterization of the detector noise performance down to 10 mK measured in a dark setting. We report a device NEP of $$2.7 \times 10^{-18}\, \hbox {W Hz}^{-1/2}$$ at 210 mK, which is below the expected photon noise level at high-altitude ground-based observatories. The NEP decreases to a constant value of approximately $$7.0 \times 10^{-19}\, \hbox {W Hz}^{-1/2}$$ below 130 mK. The white noise is well modeled by thermal generation–recombination noise (GR noise) down to 130 mK and a noise floor at low temperatures. Moreover, the addition of low-pass coaxial filters further reduces the noise floor to achieve an NEP of $$5.7 \times 10^{-19} \,\hbox {W Hz}^{-1/2}$$ below 100 mK. We discuss a photolithographic technique to adjust KID resonances that results in an $$f_{0}$$ designed versus measured scatter of $$1.7 \times 10^{-5}$$ , which will allow a significant reduction in resonators lost to clashes in full-scale designs. Finally, we present a demonstration of a new ROACH-2-based readout system operating below 500 MHz and show preliminary data indicating the suitability of this system for future highly multiplexed KID arrays.

Does a Standalone, “Cold” (Low-Thermal-Noise), Linear Resistor Exist Without Cooling?

Classical ways of cooling require some of these elements: phase transition, compressor, nonlinearity, valve and/or switch. A recent example is the 2018 patent of Linear Technology Corporation; they utilize the shot noise of a diode to produce a standalone nonlinear resistor that has [Formula: see text]/2 noise temperature (about 150[Formula: see text]K). While such “resistor” can cool its environment when it is AC coupled to a resistor, the thermal cooling effect is only academically interesting. The importance of the invention is of another nature: In low-noise electronics, it is essential to have resistors with low-noise temperature to improve the signal-to-noise ratio. A natural question is raised: can we use a linear system with feedback to cool and, most importantly, to show reduced noise temperature? Exploring this problem, we were able to produce standalone linear resistors showing strongly reduced thermal noise. Our must successful test shows [Formula: see text]/100 (about 3[Formula: see text]K) noise temperature, as if the resistor would have been immersed in liquid helium. We also found that there is an old solution offering similar results utilizing the virtual ground of an inverting amplifier at negative feedback. There, the “cold” resistor is generated at the input of an amplifier. On the other hand, our system generates the “cold” resistance at the output, which can have practical advantages.

Wide-Aperture, Low-Temperature Noise Generators for Calibration of the Radio Telescopes of Two-Element Radio Interferometer with Very Long Baseline

A complex of wide-aperture, low-temperature noise generators developed and certified at the All-Russia Research Institute of Physicotechnical and Radio Measurements (VNIIFTRI) and intended for metrological assurance of the RT-13 radio telescopes of a two-element radio interferometer with very long baseline is described. The results of studies and calibration of standard and working wide-aperture, low-temperature noise generators needed for metrological assurance of instruments used in the measurement of radio brightness and noise temperatures in the microwave region of the spectrum from 2 to 40 GHz are presented.

Measurements of Noise Temperatures of Radio Telescope Receiver System of a Two-Element Radio Interferometer with Very Long Baseline

The results of experimental investigations of the noise temperatures of the RT-13 radio telescope receiver system of a two-element radio interferometer with a very long baseline in the 2.2–2.6, 7.0–9.5, and 28–34 GHz frequency range are presented. The measurements were taken by wide-aperture low-temperature noise generators developed and certified on the standard baseline of VNIIFTRI. The error of measuring the noise temperatures of the radio telescope receiver system was determined. The confidence limits of the measurement error (for fiducial probability P = 0.95) were not more than 3.7 K.

<inline-formula> <tex-math notation="LaTeX">$E$ </tex-math> </inline-formula>-Band Mixer With IP1dB Design Consideration for Radio Astronomical Instrumentation

A lower sideband E-band mixer for radio astronomy is designed with consideration of the power compression. An E-band receiver for astronomy is analyzed to derive the power linearity specification of the mixer. The theory of noise-temperature error due to the power compression is derived. The analysis reveal that receiver with very low noise temperature is much more sensitive to the power saturation. Based on the analysis, the power compression of the mixer is set to less than 2% (0.088 dB), thus the mixer IP1dB should be at least 11 dB higher than the input power to meet the requirement of the receiver with 30–60-K noise temperature. The transistor sizes were explored in the design of the modified cascode mixer to provide sufficient IP1dB and conversion gain. The designed broadband mixer is with IP1dB higher than 3 dBm. This performance is suitable for the E-band astronomical heterodyne receiver applications.

SQUID amplifiers for axion search experiments

In the experiments for dark-matter QCD-axion searches, very weak microwave signals from a low-temperature High-Q resonant cavity should be detected using the highest sensitivity. The best commercial low-noise cryogenic semiconductor amplifiers based on high electron mobility transistors have a lowest noise temperature above 1.0 K, even if they are cooled well below 1 K. Superconducting quantum interference devices can work as microwave amplifiers with temperature noise close to the standard quantum limit. Previous SQUID-based RF amplifiers designed for axion search experiments have a microstrip resonant input coil and are thus called micro-strip SQUID amplifiers or MSAs. Due to the resonant input coupling they usually have narrow bandwidth. In this paper we report on a SQUID-based wideband microwave amplifier fabricated using sub-micron size Josephson junctions with very low capacitance. A single amplifier can be used in a frequency range of approximately 1–5 GHz.

Wideband Cryogenic Receiver for Very Long Baseline Interferometry Applications

One of the critical points concerning radio-astronomy applications regards the power received by the radio telescope, most often extremely faint. Beyond approaches aimed at increasing the collecting area of the radio telescope (at microwave frequencies almost always a reflector antenna), such as for example the use of very long baseline interferometry (VLBI) techniques, a key point is the installation of cryogenic receivers to reduce the system noise temperature. To achieve the lowest noise temperature, it is desirable to cryogenically cool also the feed of the reflector antenna. This is achieved by enclosing the feed in a Dewar to provide the required thermal isolation between the feed and the external environment. However, this enclosure inevitably affects the radiation properties of the feed. This letter presents the development of a cryogenic receiver, composed of a 2–14 GHz quad ridge flared horn and a Dewar, for a notable case where the Dewar is designed to be as compact as possible to minimize not only the thermal and mechanical load, but also the illumination blockage. Indeed, the receiver is intended to be installed on a 12 m reflector antenna for VLBI applications, whose optics require an installation of the feed itself very close to the subreflector. A prototype of the cryogenic receiver has been fabricated and measured, discussing the impact of the Dewar on the feed radiation patterns, input matching, isolation, antenna efficiency, and showing the overall system noise temperature.

Wide-aperture low-temperature noise generators for calibration radio telescope of two-elements radio interferometer with very long baseline

Wide-aperture low-temperature noise generators for calibration radio telescope of two-elements radio interferometer with very long baseline

Water Vapor Radiometer: Measuring Instrument of Atmospheric Brightness Temperature

Results are presented for pilot studies of the error in measuring atmospheric brightness temperature at frequencies 20.7 and 31.4 GHz in the vicinity of water vapor emission lines. The accuracy of atmospheric brightness temperature measurements was evaluated using the water vapor radiometer at the Zelenchukskaya observatory. Measurements were made using the PNShI200 wide-aperture low-temperature noise generator, a working standard for the unit of equivalent noise temperature. The requirements for radiophysical characteristics and accuracy of reproduction of a unit of noise temperature were formulated for prospective reference wide-aperture low-temperature noise generators.

Advanced Terahertz Sensing and Imaging Systems Based on Integrated III-V Interband Tunneling Devices

Owing to the unprecedented development in terahertz (THz) sources and detectors in the last decade, technologists and researchers have intensified their efforts to develop advanced THz sensing and imaging systems with superior performance and unique functionalities. One of the key elements to realize such systems is the ability to monolithically integrate high-performance semiconductor devices with THz antennas and other passive structures. In recent years, devices based on interband tunneling in III-V heterostructures have emerged as promising candidates for THz detection that offer extremely high nonlinearity, high sensitivity, low noise, fast response, and room temperature operation. In this paper, we first review the development of heterostructure backward tunnel diodes (HBDs) in the InAs/AlSb/AlGaSb material system that have been demonstrated with detection sensitivity that outperforms the current state of the art (e.g., the fundamental limit of Schottky diodes) and with noise-equivalent power (NEP) below 0.2 pW/Hz½. We then present the monolithic integration of HBDs with planar folded dipole antennas (FDAs) using submicrometer-scale airbridges to achieve optimized impedance matching for high-performance and compact THz detectors and focal-plane array (FPA) imaging systems. In addition, the potential of using HBDs for realizing THz systems with advanced functionalities such as spectroscopic FPAs (using frequency-tunable THz antennas) and polariametric detection/imaging systems will be discussed. Finally, the integration of HBDs into waveguides for more advanced THz sensing and imaging (e.g., a six-port reflectometer for near-field imaging) will be discussed.

Remote Temperature Distribution Sensing Using Permanent Magnets

Remote temperature sensing is essential for applications in enclosed vessels, where feedthroughs or optical access points are not possible. A unique sensing method for measuring the temperature of multiple closely spaced points is proposed using permanent magnets and several three-axis magnetic field sensors. The magnetic field theory for multiple magnets is discussed and a solution technique is presented. Experimental calibration procedures, solution inversion considerations, and methods for optimizing the magnet orientations are described in order to obtain low-noise temperature estimates. The experimental setup and the properties of permanent magnets are shown. Finally, experiments were conducted to determine the temperature of nine magnets in different configurations over a temperature range of 5 °C to 60 °C and for a sensor-to-magnet distance of up to 35 mm. To show the possible applications of this sensing system for measuring temperatures through metal walls, additional experiments were conducted inside an opaque 304 stainless steel cylinder.

Understanding Coulomb Scattering Mechanism in Monolayer MoS2 Channel in the Presence of h-BN Buffer Layer

As the thickness becomes thinner, the importance of Coulomb scattering in two-dimensional layered materials increases because of the close proximity between channel and interfacial layer and the reduced screening effects. The Coulomb scattering in the channel is usually obscured mainly by the Schottky barrier at the contact in the noise measurements. Here, we report low-temperature (T) noise measurements to understand the Coulomb scattering mechanism in the MoS2 channel in the presence of h-BN buffer layer on the silicon dioxide (SiO2) insulating layer. One essential measure in the noise analysis is the Coulomb scattering parameter (αSC) which is different for channel materials and electron excess doping concentrations. This was extracted exclusively from a 4-probe method by eliminating the Schottky contact effect. We found that the presence of h-BN on SiO2 provides the suppression of αSC twice, the reduction of interfacial traps density by 100 times, and the lowered Schottky barrier noise by 50 times compared to those on SiO2 at T = 25 K. These improvements enable us to successfully identify the main noise source in the channel, which is the trapping-detrapping process at gate dielectrics rather than the charged impurities localized at the channel, as confirmed by fitting the noise features to the carrier number and correlated mobility fluctuation model. Further, the reduction in contact noise at low temperature in our system is attributed to inhomogeneous distributed Schottky barrier height distribution in the metal-MoS2 contact region.

Noise analysis in distributed amplifiers with feedback‐active load

This study presents the noise analysis of amplifiers when the input line termination is implemented via an active load. The noise figure (NF) of distributed amplifiers is analysed to determine the effect of the gate and drain terminations. The noise of a transistor configured as a one-port device has been analysed and a lower noise temperature has been achieved as compared with a conventional resistor. In order to improve the noise performance of the overall amplifier, a parallel feedback has been added to the active load, and its effects are analysed in terms of noise. A distributed amplifier has been designed as a test vehicle of the analysis and characterised with a resistor as input line termination and with an active load to demonstrate the improvement in NF at frequencies below 2 GHz. The resulting amplifier exhibits 10.9 dB of small signal gain from 1 to 5 GHz, with a reduction of 0.6 dB in NF below 2 GHz when the input line termination is replaced by an active load.

A comparative study on simulation and experiment of oil-air lubrication unit for high speed bearing

Purpose The purpose of this paper is to design an oil-air lubrication system with low temperature rise, vibration and noise simplifies the spindle configuration. The oil-air lubrication unit is a key component for high-speed grinding machine tools. The development of oil-air lubrication unit suitable for high/ultrahigh rotational speed is a daunting task owing to the lubrication challenges. Design/methodology/approach This paper emphasizes three main issues: the analysis of oil-air two-phase flow for tradition oil-air lubrication unit with the simulation method; the design of new oil-air lubrication unit for the high/ultrahigh-speed grinding machine tools and the comparative experiment research of tradition and new oil-air lubrication unit. The optimum structure parameters that create the optimum flow pattern and operating conditions resulting in low temperature increase, vibration and noise of oil-air lubricated spindle can be achieved by the simulation method and experiments. Findings The simulation and experimental results show that new oil-air lubrication unit lubricating a high speed electric spindle has a better performance with a small temperature increase and vibration, which means that our proposed method is an effective design method for oil-air lubrication system. Originality/value A design method suitable for high-speed oil-air lubrication unit is proposed. New oil-air lubrication unit is expected to apply for high/ultrahigh rotational speed grinding machine tools.

Dissipative extension of the Ghirardi-Rimini-Weber model

In this paper, we present an extension of the Ghirardi-Rimini-Weber model for the spontaneous collapse of the wave function. Through the inclusion of dissipation, we avoid the divergence of the energy on the long-time scale, which affects the original model. In particular, we define jump operators, which depend on the momentum of the system and lead to an exponential relaxation of the energy to a finite value. The finite asymptotic energy is naturally associated to a collapse noise with a finite temperature, which is a basic realistic feature of our extended model. Remarkably, even in the presence of a low-temperature noise, the collapse model is effective. The action of the jump operators still localizes the wave function and the relevance of the localization increases with the size of the system, according to the so-called amplification mechanism, which guarantees a unified description of the evolution of microscopic and macroscopic systems. We study in detail the features of our model, at the level of both the trajectories in the Hilbert space and the master equation for the average state of the system. In addition, we show that the dissipative Ghirardi-Rimini-Weber model, as well as the original one, can be fully characterized in a compact way by means of a proper stochastic differential equation.

MicroPMT–A New Photodetector for Gamma Spectrometry and Fast Timing?

Hamamatsu recently announced the launch of a new type of a photodetector, a micro photomultiplier (microPMT or μPMT). This detector works like a classic photomultiplier but the whole device is made directly in a silicon wafer sandwiched between two glass layers. A microPMT has dimensions of only 13×10×2mm and its photocathode has size of 3×1mm. According to the producers, this newly developed photodetector keeps all the advantages of a classic photomultiplier such as high gain, high sensitivity, low noise, high speed, and low temperature dependence. The aim of the work is to verify usefulness of a microPMT in gamma spectrometry with scintillators and fast timing. In the first part of the study analysis of the energy resolution obtained with 3×3×1mm LSO, BGO and CsI(Tl) scintillators is made. The light pulse shapes of a single photoelectron and scintillation signal of LSO are also showed. The important part of the study are measurements of the number of photoelectrons and estimation of the excess noise factor. In the second part, measurements of the time jitter and timing resolution with LSO crystal for 511keV annihilation quanta are reported. All the results are compared with data obtained with classic PMTs.

Time Crystals in Ultracold Matter

We consider the formation of time crystals in a gas of laser-cooled atoms. We show that the phonon frequency is shifted inside a time crystal, and the phonon backscattering resulting from a temporal Bragg diffraction can be observed. A quantum-field description allows us to demonstrate that these effects are accompanied by emission of the phonon pairs from vacuum. The same description can be used for the dynamical Casimir effect, which, in some sense, is as a special case of the time crystal with similar quantum vacuum properties. Due to its low temperature and low noise level, a gas of ultracold atoms seems promising for experimental studies in quantum vacuum phenomena, such as those associated with time crystals.

Development of a water calorimeter as the absorbed dose-to-water primary standard for China

K. Wang , S. Jin , X. Yang , J. Zhang , M. McEwen , C. Cojocaru , C. Ross . National Institute of Metrology (NIM), China; National Research Council of Canada (NRC), Canada In collaboration with the National Research Council Canada (NRC), the National Institute of Metrology, China (NIM) is developing a new primary standard for absorbed dose to water at radiotherapy dose levels. The standard is based on a water calorimeter and is designed to operate in Co60 and megavoltage photon beams from a linear accelerator. The main features of the calorimeter are as follows: i) operation at 4 oC to eliminate the problems associatedwith convection in water phantoms at room temperature; ii) a low-noise temperature measurement circuit able to resolve temperature differences at the mK level; iii) capability to investigate different water purities and determine the heat defect due to dissolved gases; iv) potential extension to determination of absorbed dose in high-energy electron beams and HDR brachytherapy; v) determination of absorbed dose to water with a standard uncertainty of better than 0.4 %. Commissioning of the calorimeter involved a comparison with the present NIM standard of absorbed dose and a comparison with the NRC primary standard water calorimeter. Other investigations carried out included: the effect of environmental changes on the temperature control; repeatability of the system over the course of several weeks; stability of thermistor calibrations to determine the radiation-induced temperature rise; capability of the linac to deliver consistent doses (suitable for primary standards measurements) over the course of a day and determination of correction factors for beam uniformity for a range of detector geometries. A full uncertainty analysis indicates that the target uncertainty specification can be achieved. This new standard will significantly reduce the uncertainty of ion chamber calibrations for Chinese radiotherapy centres and open up new areas of research for the NIM.

Application of Environmental Protection and Safety Bituminous Mixture in Tunnel

Based on the special performance of the tunnel, a low temperature, flame-retardant and safety environmental noise reduction asphalt mixtures was developed. The result of paving the experimental road section showed that environmental protection and safety bituminous mixture compared with ordinary hot mix asphalt mixture has low temperature, fire-retardant, noise reduction characteristics. Keywords: road tunnel; viscous and environment asphalt; Mixture design; Pavement performance;test road