Photon Heat Research Articles

The role of soft photon injection and heating in 21 cm cosmology

ABSTRACT The ARCADE radio excess and EDGES measurement remain puzzling. A link between the two has been previously considered, however, in this work we highlight an important related effect that was not analysed in detail before. By performing cosmological thermalization calculations with soft photon injection using cosmotherm, we show that for the 21 cm signal generation, the interplay between enhanced radio spectral distortions and the associated heating can hide a significant radio excess before the reionization era. We illustrate this effect for a simple power-law soft photon source in decaying particle scenarios. Even if simplistic, the uncovered link between CMB spectral distortions and 21 cm cosmology should apply to a much broader range of scenarios. This could significantly affect the constraints derived from existing and future 21 cm observations on the evolution of the ambient radio background. In particular, scenarios that would be ruled out by existing data without heating could become viable solutions once the heating is accounted for in the modelling. Our calculations furthermore highlight the importance of global 21 cm observations reaching into the dark ages, where various scenarios can potentially be distinguished.

Unveiling the underlying mechanism of unusual thermal conductivity behavior in multicomponent high-entropy (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xCex)2O7 ceramics

Previously, the research on thermal conductivity of ceramic thermal barrier coatings mainly focused on phonon and photon thermal conductivity (thermal radiation effect). However, electrical conductivity is remarkable in some systems. Hence, the contribution of phonon, photon and electronic heat conduction to thermal conductivity of high-entropy systems was evaluated in this study. The (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xCex)2O7 (x = 0–0.5) high-entropy ceramics with single defective fluorite structure were successfully prepared via a solid reaction method. Below 600 °C, the thermal conductivities decrease with increasing temperature for x = 0.1–0.5 components, then reveal a drastic temperature dependent increase. Moreover, the composition dependent thermal conductivities are also unusual based on the conventional phonon thermal conduction mechanism. The increased electronic thermal conductivity, improved photon thermal conductivity (at high temperatures) and reduced phonon-grain boundary scattering should be responsible for the unusual thermal conductivity behavior. This can be verified by the significantly increased electrical conductivity, optical transmittance and grain size, as well as reduced emissivity for (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xCex)2O7 high-entropy ceramics. The present study also broadens the way to investigate the thermal conductivity of ceramic thermal barrier coatings, and is helpful to design thermal barrier coatings with low thermal conductivity.

Scalable and dynamically passive thermal regulation over solar wavelengths enabled by phase-transition metamaterials

About 20% of all energy utilized worldwide is allocated to regulate the temperature of buildings through heating and cooling in response to seasonal changes. Numerous cutting-edge, low-carbon-footprint innovations have recently been demonstrated to assist resolve this issue, including passive radiative cooling and sun heating. Their accessibility is nevertheless constrained to particular seasons or climate zones by the steady and one-sided control of temperature. Here, taking advantage of recent breakthroughs in photonic manipulation and radiative heat transfer technology, we propose phase-transition metamaterials with dynamically passive and radiative thermal regulation capability for temperature control that can be scaled up for application in buildings. At a critical temperature, the sun absorptance of this metafilm can self-modulate from 0.9 to 0.18 as a result of temperature changes. This metafilm is made of reflective silver (Ag) thin film on top of polyethylene (PE) film with vanadium dioxide (VO2) nanoparticles embedded in it. By varying the volume percentages of the VO2 nanoparticles and the PE matrix thickness, this metafilm’s optical performance can be tailored. We model the inactive dynamic thermal regulator’s equilibrium temperature response to diurnal temperature swings. The industrial film extrusion approach has the potential to produce the nanoparticles embedded into the polymer structure, and the physical vapor deposition method can deposit the Ag thin film scalably, both of which are encouraging for scale-up deployment. This passive radiative heat thermal management technology can be potentially applied to regions with extreme annual temperature fluctuations.

Near-Field Thermophotovoltaic Energy Conversion: Progress and Opportunities

Thermophotovoltaic (TPV) energy conversion is a promising power-generation technology for converting heat to electricity. Recent studies have explored TPV devices featuring nanoscale gaps, which take advantage of near-field effects that enable much larger radiative fluxes and power density. The authors review the physics of near-field thermal radiation, and assess theoretical and experimental advances in predicting and validating near-field enhancements of power output and efficiency in TPV devices. Their discussion of the near-field photonic heat engines presented here will help to guide future engineering solutions in developing practical near-field energy-conversion devices.

Photonic heat transport from weak to strong coupling

Superconducting circuits provide a favorable platform for quantum thermodynamic experiments. An important component for such experiments is a heat valve, i.e., a device which allows one to control the heat power flowing through the system. Here we theoretically study the heat valve based on a superconducting quantum interference device (SQUID) coupled to two heat baths via two resonators. The heat current in such a system can be tuned by magnetic flux. We investigate how the heat current modulation depends on the coupling strength $g$ between the SQUID and the resonators. In the weak coupling regime the heat current modulation grows as ${g}^{2}$, but, surprisingly, at the intermediate coupling it can be strongly suppressed. This effect is linked to the resonant nature of the heat transport at weak coupling, where the heat current dependence on the magnetic flux is a periodic set of narrow peaks. At the intermediate coupling the peaks become broader and overlap, thus reducing the heat modulation. At very strong coupling the heat modulation grows again and finally saturates at a constant value.

Dose voxel resolution determination for Monte Carlo electron beam simulation in thin targets.

Monte Carlo particle simulation has become the primary tool for designing low-energy miniature x-ray tubes due to the difficulties of physically prototyping these devices and characterizing their radiation fields. Accurate simulation of electronic interactions within their targets is necessary for modelling both photon production and heat transfer. Voxel-averaging can conceal hot spots in the target heat deposition profile that can threaten the integrity of the tube. This research seeks a computationally-efficient method of estimating voxel-averaging error in energy deposition simulations of electron beams penetrating thin targets to inform the appropriate scoring resolution for a desired accuracy level. An analytical model to estimate voxel-averaging along the target depth was developed and compared to results from Geant4 via its wrapper, TOPAS. A 200 keV planar electron beam was simulated to impinge tungsten targets of thicknesses between 1.5- and 12.5- . For each target, the model was used to calculate the energy deposition ratio between voxels of varying sizes centered on the longitudinal midpoint of the target. Model-calculated ratios were compared to simulation outputs to gauge the model's accuracy. Then, the model was used to approximate the error between the point value of electron energy deposition and a voxel-based measurement. The model underestimates error to within 5% for targets less than 7.5- in thickness with increasing error for greater thicknesses. For the 1.5- target, calculations of the point-vs.-voxel energy deposition show an 11% averaging effect between the midpoint and a 1.5- voxel. Energy deposition profiles along the target depth were also calculated in the Monte Carlo for reference. A simple analytical model was developed with reasonable accuracy to guide Monte Carlo users in estimating the appropriate depth-voxel size for thin-target x-ray tube simulations. This methodology can be adapted for other radiological contexts to increase robustness in point-value estimations. This article is protected by copyright. All rights reserved.

Reconsidering Photonic Quantum Heat Engine Efficiency

A device — referred to as a photonic quantum heat engine — was reported in Nature Photonics [J. Kim, S. Oh, D. Yang, J. Kim, M. Lee and K. An, A photonic quantum engine driven by superradiance, Nat. Photon. 16 (2022) 707–711] with an efficiency of [Formula: see text]%. Moreover, in a related News & Views contribution in the same issue [M. Kim, M. Scully and A. Svidzinsky, A supercharged photonic quantum heat engine, Nat. Photon. 16 (2022) 669–670], this device was reported to exceed the Carnot limit, an extraordinary claim. As Carl Sagan once remarked, “Extraordinary claims require extraordinary evidence.” Here, we outline the fundamental lack of empirical evidence that would be required to support such a claim, show that the actual efficiency of the device is [Formula: see text] 0% and bring to attention critical aspects of the operating physics of the device.

Moving media as photonic heat engine and pump

A system consisting of two slabs with different temperatures can exhibit a non-equilibrium lateral Casimir force on either one of the slabs when Lorentz reciprocity is broken in at least one of the slabs. This system constitutes a photonic heat engine that converts radiative heat into work done by the non-equilibrium lateral Casimir force. Reversely, by sliding two slabs at a sufficiently high relative velocity, heat is pumped from the slab at a lower temperature to the other one at a higher temperature. Hence the system operates as a photonic heat pump. In this work, we study the thermodynamic performance of such a photonic heat engine and pump via the fluctuational electrodynamics formalism. The propulsion force due to the non-reciprocity and the drag force due to the Doppler effect was revealed as the physical mechanism behind the heat engine. We also show that in the case of the heat pump, the use of nonreciprocal materials can help reduce the required velocity. We present an ideal material dispersion to reach the Carnot efficiency limit. Furthermore, we derive a relativistic version of the thermodynamic efficiency for our heat engine and prove that it is bounded by the Carnot efficiency that is independent of the frame of reference. Our work serves as a conceptual guide for the realization of photonic heat engines based on fluctuating electromagnetic fields and relativistic thermodynamics and shows the important role of electromagnetic non-reciprocity in operating them.

Exploring the increasing behavior of thermal conductivity for high-entropy zirconates at high temperatures

Up to present, the discussion on the increase of thermal conductivity at high temperatures for thermal barrier coatings is not comprehensive enough. The present study systematically explored the increased behavior of high temperature thermal conductivity for (La0.2Gd0.2Y0.2Yb0.2Er0.2)2(Zr1-xTix)2O7 high-entropy ceramics. Above 600 ℃, the thermal conductivities of x = 0.1–0.5 components increase with composition and temperature. The significantly reduced emissivity and improved transmittance imply that the reason for the increase of high temperature thermal conductivity is the remarkable improvement of photon thermal conductivity. Importantly, this study provides a route to explore the different behavior of high temperature thermal conductivity by investigating phonon, photon and electronic heat conduction behaviors, which is also conducive to design and develop advanced thermal barrier coatings with low thermal conductivity.

Electromagnetic simulation and microwave circuit approach of heat transport in superconducting qubits

The study of quantum heat transport in superconducting circuits is significant for further understanding the connection between quantum mechanics and thermodynamics, and for possible applications for quantum information. The first experimental realisations of devices demonstrating photonic heat transport mediated by a qubit have already been designed and measured. Motivated by the analysis of such experimental results, and for future experimental designs, we numerically evaluate the photonic heat transport of qubit-resonator devices in the linear circuit regime through electromagnetic simulations using Sonnet software, and compare with microwave circuit theory. We show that the method is a powerful tool to calculate heat transport and predict unwanted parasitic resonances and background.

Comparison of Low-Redshift Lyman-α Forest Observations to Hydrodynamical Simulations with Dark Photon Dark Matter.

Recent work has suggested that an additional ≲6.9 eV per baryon of heating in the intergalactic medium is needed to reconcile hydrodynamical simulations with Lyman-α forest absorption line widths at redshift z≃0.1. Resonant conversion of dark photon dark matter into low frequency photons is a viable source of such heating. We perform the first hydrodynamical simulations including dark photon heating and show that dark photons with mass m_{A^{'}}∼8×10^{-14} eV c^{-2} and kinetic mixing ε∼5×10^{-15} can alleviate the heating excess. A prediction of this model is a nonstandard thermal history for underdense gas at z≳3.

On-the-fly energy release per fission model in STREAM with explicit neutron and photon heating

The on-the-fly energy release per fission (OTFK) model is implemented in STREAM to continuously update the Kappa values during the depletion calculation. The explicit neutron and photon energy distribution, which has not been considered in previous STREAM versions, is incorporated into the existing on-the-fly model. The impacts of the modified OTFK model with explicit neutron and photon heating in STREAM on the power distribution, fuel temperature, and other core parameters during depletion with feedback calculations are studied using several problems from the VERA benchmark suit. Overall, the explicit heating calculation provides a better power map for the feedback calculations particularly when strong gamma emitters are present. Generally, the fuel temperature decreases when neutron and photon heating is employed because fission neutrons and gamma rays are transported away from their points of generation. This energy release model in STREAM indicates that gamma energy accounts for approximately 9.5%–10% of the total energy released, and approximately 2.4%–2.6% of the total energy released will be deposited in the coolant for the VERA 5, NuScale, and Yonggwang Unit 3 2D cores.

Unique sandwich design of high-efficiency heat-conducting phosphor-in-glass film for high-quality laser-driven white lighting

Multi-color phosphor-in-glass (PiG) film has been considered as a promising color converter in high-quality laser lighting owing to its outstanding merits of phosphor versatility, tunable luminescence, and simple preparation. However, the opto-thermal properties of PiG film are severely affected by the photon reabsorption and backward scattering of phosphor structure and the heat conduction of substrate. Herein, a unique sandwich design of phosphor structure was introduced in the multi-color PiG film for high-quality laser lighting. By elaborately synthesizing the borosilicate glass with low glass transition temperature (Tg), similar expansion coefficient, and high refractive index (RI), the sandwiched PiGs were prepared by sintering (~600 °C) broadband green and red phosphor glass films on the double sides of sapphire. The green and red PiG films were tightly coated on the sapphire with no delamination and maintained higher luminescence intensity than raw phosphors at high temperatures. By simultaneously coupling photon reabsorption and backward scattering, the sandwiched green PiG film—sapphire—red PiG film (G—S—R PiG) yields a high-quality white light with a high luminous efficacy of 163 lm/W and an excellent color rendering index (CRI) of 85.4 under a laser power of 2.4 W, which are the best comprehensive results yet reported. Benefiting from the ingenious sandwich design with heat-conducting sapphire and thin PiG films, the G—S—R PiG displays low working temperatures (< 200 °C) under high-power laser excitation. This work reveals the role of sandwiched phosphor structure in photon loss and heat dissipation, which provides a new strategy to design PiG films for high-quality laser lighting.

A supercharged photonic quantum heat engine

A supercharged photonic quantum heat engine

Shot noise of photonic heat transport through an oscillation device modulated by Majorana fermions

The photonic heat transport through an oscillation device under the modulation of Majorana bound states (MBSs) is investigated by using nonequilibrium Green’s function method. The photonic heat current correlation and shot noise formulas are derived. The overall behavior of heat shot noise is governed by terminal temperatures, while its detailed construction is modulated by the attached MBSs and oscillation device. The maximum values of heat current and shot noise are located at integer n times quantum flux Φ0, while they are modulated to zero at half integer of quantum flux (n+12)Φ0 due to changing magnetic flux. The Fano factor presents explicit nonlinear behavior by decreasing firstly to the minimum value and then increasing as the increase of temperature difference. The minimum value of Fano factor is raised up, while its position shifts towards zero temperature difference due to increasing terminal photon frequency. The monotonous enhancement of Fano factor valley is presented due to increasing the coupling constant λ between oscillation device and MBSs, while nonmonotonous variation of Fano factor valley is generated by adjusting the coupling energy ɛM of MBSs.

Photonic heat transport in three terminal superconducting circuit

We report an experimental realization of a three-terminal photonic heat transport device based on a superconducting quantum circuit. The central element of the device is a flux qubit made of a superconducting loop containing three Josephson junctions, which can be tuned by magnetic flux. It is connected to three resonators terminated by resistors. By heating one of the resistors and monitoring the temperatures of the other two, we determine photonic heat currents in the system and demonstrate their tunability by magnetic field at the level of 1 aW. We determine system parameters by performing microwave transmission measurements on a separate nominally identical sample and, in this way, demonstrate clear correlation between the level splitting of the qubit and the heat currents flowing through it. Our experiment is an important step towards realization of heat transistors, heat amplifiers, masers pumped by heat and other quantum heat transport devices.

Laser-Induced Morphological and Structural Changes of Cesium Lead Bromide Nanocrystals.

Metal halide perovskite nanocrystals, an emerging class of materials for advanced photonic and optoelectronic applications, are mainly fabricated with colloidal chemistry routes. On the quest for new properties according to application needs, new perovskite systems of various morphologies and levels of doping and alloying have been developed, often also involving post-synthesis reactions. Recently, laser irradiation in liquids has been utilized as a fast method to synthesize or transform materials and interesting laser-induced transformations on nanocrystals were induced. These studies in general have been limited to small nanocrystals (~15 nm). In the case of halide perovskites, fragmentation or anion exchange have been observed in such laser-based processes, but no crystal structure transformations were actually observed or deliberately studied. Nanocrystals are more sensitive to light exposure compared to the corresponding bulk crystals. Additional factors, such as size, morphology, the presence of impurities, and others, can intricately affect the photon absorption and heat dissipation in nanocrystal suspensions during laser irradiation. All these factors can play an important role in the final morphologies and in the time required for these transformations to unfold. In the present work, we have employed a 513 nm femtosecond (fs) laser to induce different transformations in large nanocrystals, in which two phases coexist in the same particle (Cs4PbBr6/CsPbBr3 nanohexagons of ~100 nm), dispersed in dichlorobenzene. These transformations include: (i) the exfoliation of the primary nanohexagons and partial anion exchange; (ii) fragmentation in smaller nanocubes and partial anion exchange; (iii) side-by-side-oriented attachment, fusion, and formation of nanoplatelets and complete anion exchange; (iv) side-by-side attachment, fusion, and formation of nanosheets. Partial or complete Br-Cl anion exchange in the above transformations was triggered by the partial degradation of dichlorobenzene. In addition to the detailed analysis of the various nanocrystal morphologies observed in the various transformations, the structure–photoluminescence relationships for the different samples were analyzed and discussed.

Photothermal phenomenon: Extended ideas for thermophysical properties characterization

The photothermal phenomenon involves material photon heating in the form of continuous waves, modulated waves, or pulses. The resulting temperature rise carries very rich information about the material's structures and thermophysical properties. This review is constructed to cover some of the extended ideas of the photothermal phenomenon for measuring a material's thermophysical properties and interface thermal conductance/resistance. For frequency-domain photothermal phenomena, the photoacoustic (PA) and photothermal radiation (PT) techniques provide great ways to measure coatings and suspended samples, which can also be measured using the laser flash and time-domain thermoreflectance (TDTR) techniques. Thermal probing based on electrical thermal sensing is successfully implemented in the transient photo-electro-thermal (TPET) and pulsed laser-assisted thermal relaxation (PLTR) techniques, which significantly extend the capability of laser flash technique to micro/nanoscale 1D structures. The energy transport state-resolved Raman (ET-Raman) is distinct from traditional techniques in its material-specific thermal sensing capability and integral way of ultrafast thermal sensing. Detailed physics discussions are provided for all these techniques, including their advantages and limitations. Still, large development rooms exist for the relatively new techniques, including TPET, PLTR, and ET-Raman. These include measurements under extreme situations, sensitivity improvement, and distinguishing conjugated physical processes.

Analysis of several VERA benchmark problems with the photon transport capability of STREAM

STREAM - a lattice transport calculation code with method of characteristics for the purpose of light water reactor analysis - has been developed by the Computational Reactor Physics and Experiment laboratory (CORE) of the Ulsan National Institute of Science and Technology (UNIST). Recently, efforts have been taken to develop a photon module in STREAM to assess photon heating and the influence of gamma photon transport on power distributions, as only neutron transport was considered in previous STREAM versions. A multi-group photon library is produced for STREAM based on the ENDF/B-VII.1 library with the use of the library-processing code NJOY. The developed photon solver for the computation of 2D and 3D distributions of photon flux and energy deposition is based on the method of characteristics like the neutron solver. The photon library and photon module produced and implemented for STREAM are verified on VERA pin and assembly problems by comparison with the Monte Carlo code MCS – also developed at UNIST. A short analysis of the impact of photon transport during depletion and thermal hydraulics feedback is presented for a 2D core also from the VERA benchmark.

Oscillations of photonic heat current through parallel-coupled double circular mesoscopic Josephson junction devices

Oscillations of photonic heat current through parallel-coupled double circular mesoscopic Josephson junction devices