Planck Blackbody Radiation Research Articles

Minimally-intrusive, dual-band, fiber-optic sensing system for high-enthalpy exhaust plumes

<abstract> <p>The propulsion research lab at Utah State University has developed a minimally-intrusive optical sensing system for high-temperature/high-velocity gas-generator exhaust plumes. For this application glass fiber-optic cables, acting as radiation conduits, are inserted through the combustion chamber or nozzle wall and look directly into the flow core. The cable transmits data from the flame zone to externally-mounted spectrometers. In order to capture the full-optical spectrum, a blended dual-spectrum system was employed, with one spectrometer system tuned for best-response across the visible-light and near-infrared spectrum, and one spectrometer tuned for best-response in the near- and mid-infrared spectrum. The dual-band sensors are radiometrically-calibrated and the sensed-spectra are spliced together using an optimal Wiener filtering algorithm to perform the deconvolution. The merged spectrum is subsequently curve-fit to Planck's black-body radiation law, and flame temperature is calculated from associated curve maxima (Wien's law). The presented fiber-optic sensing systems performs a function that is analogous to Raman spectroscopy. The system non-contact, high-temperature measurement, and does not interfere with the heat transfer processes. In this report data collected from a lab-scale (200 N) hybrid rocket system are analyzed using the described method. Optically-sensed flame-temperatures are correlated to analytical predictions, and shown to generally agree within a few degrees. Additionally, local maxima in the optical spectra are shown to correspond to emission frequencies of atomic and molecular oxygen, water vapor, and molecular nitrogen; all species known to exist in the hybrid combustion plume. Presented data demonstrate that selected fiber-optics can survive temperature greater than 3000 ℃, for durations of up to 25 seconds.</p> </abstract>

Illuminating a bacterial adaptation mechanism: Infrared-driven cell division in deep-sea hydrothermal vent environments

<p>Based on Planck's black-body radiation law, deep-sea hydrothermal vent chimneys emit light, predominantly infrared light, which potentially supports bacterial photosynthesis in this ecosystem independently of the solar energy. To investigate the impact of this geothermal light on bacterial growth, we collected samples from the Southwest Indian Ridge and demonstrated that infrared light alone promotes bacterial growth and alters population composition. The mechanism of infrared stimulated growth was analyzed by monitoring cell wall synthesis using the <i>Tepidibacter hydrothermalis</i> strain SWIR-1, which was isolated from cultures enriched through infrared irradiation. The results showed that the elevated hydrostatic pressure inhibited septal peptidoglycan synthesis and cell division, but had less effect on cell elongation, chromosome replication and segregation. The dominant cell shape was filaments with some swelling and inertness in cell wall synthesis depending on the level of pressure applied. Interestingly, irradiation with 880 nm infrared light effectively initiated septal synthesis and alleviated the obstruction. This revelation uncovers a novel adaptation mechanism involving infrared light for bacteria dwelling in deep-sea environments, and sheds light on the potential of infrared-mediated photobiomodulation.</p>

Experimental Determination of Absolute Spectral Radiance and Emissivity of a Photonic Crystal Filament

A recent discovery of super-Planckian radiation in the far-field has attracted a great deal of interest in thermal radiation control using photonic crystals (PC) architecture. The finding is based on a careful comparison of radiation intensity emitted from a PC nano-filament and a blackbody at the same temperature and same wavelength at λ∼1.7 μm. Extending that finding, we determined the absolute spectral radiance of such a PC filament at λ∼1.7 μm at elevated temperature, T = 445–723 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> °</sup> K, and compared its value to that predicted by Planck's blackbody radiation law. Our data confirmed that the PC spectral radiance surpassed that of a blackbody by an order-of-magnitude. We also determined the spectral emissivity of our PC filament and showed that its value far exceeded unity at resonance and fell below unity away from resonance. The observation of non-equality between absorptivity and emissivity suggests that a strong optical non-reciprocity takes place in our PC nano-filament.

An improved mathematical prediction of the time evolution of the Covid-19 pandemic in Italy, with a Monte Carlo simulation and error analyses

We present an improved mathematical analysis of the time evolution of the Covid-19 pandemic in Italy and a statistical error analyses of its evolution, including a Monte Carlo simulation with a very large number of runs to evaluate the uncertainties in its evolution. A previous analysis was based on the assumption that the number of nasopharyngeal swabs would be constant. However, the number of daily swabs is now more than five times what it was when we did our previous analysis. Therefore, here we consider the time evolution of the ratio of the new daily cases to number of swabs, which is more representative of the evolution of the pandemic when the number of swabs is increasing or changing in time. We consider a number of possible distributions representing the evolution of the pandemic in Italy, and we test their prediction capability over a period of up to 6 weeks. The results show that a distribution of the type of Planck black body radiation law provides very good forecasting. The use of different distributions provides an independent possible estimate of the uncertainty. We then consider five possible trajectories for the number of daily swabs and we estimate the potential dates of a substantial reduction in the number of new daily cases. We then estimate the spread in a substantial reduction, below a certain threshold, of the daily cases per swab among the Italian regions. We finally perform a Monte Carlo simulation with 25,000 runs to evaluate a random uncertainty in the prediction of the date of a substantial reduction in the number of diagnosed daily cases per swab.

High-performance near-field thermophotovoltaic device with CaF&lt;sub&gt;2&lt;/sub&gt;/W multilayer hyperbolic metamaterial emitter

Thermophotovoltaic (TPV) device is a thermoelectric conversion method with great application prospects. In the far-field regime, the thermoelectric power is usually small due to the Planck blackbody radiation limit, but can be substantially enhanced in the near-field regime where evanescent waves will participate in the heat transfer by tunneling. In this aspect, the surface optical density of state is a key factor that will determine the transfer conversion of thermal photons. Plasmonic or phononic resonance materials have been discussed in the literature to acquire large heat flux. Besides, metamaterial is another way to pursue the design freedoms for the same purpose. In this work, we propose a [CaF&lt;sub&gt;2&lt;/sub&gt;/W]&lt;i&gt;&lt;sub&gt;n&lt;/sub&gt;&lt;/i&gt; multilayer based infrared hyperbolic metamaterial (HMM) with high surface density of states as an emitter of a high-performance TPV cell made of an InSb p-n junction (energy bandgap = 0.17 eV). The effective medium theory (EMT) is utilized to describe the electromagnetic behavior of the HMM. The near-field heat flux is calculated based on electrodynamic wave theory and Green's function method, and the photocurrent of thermophotovoltaic device is derived using diffusion equation for semiconductor. For comparison, we design three different radiators, i.e. tungsten film (W), [GaF&lt;sub&gt;2&lt;/sub&gt;/W]&lt;i&gt;&lt;sub&gt;n&lt;/sub&gt;&lt;/i&gt; multilayer hyperbolic metamaterial (HMM), and tungsten-grounded HMM (WHMM). Compared with the pure tungsten radiator, the artificial structure exhibits the hyperbolic dispersion characteristic in a wide frequency range, which gives rise to a higher local density of states, in particular in the hyperbolic-to-elliptic spectral transition region. As a result, the radiation power and the energy conversion efficiency are greatly enhanced, which are more easily realized by a matched emission band achieved by the structural design. We find that the thermophotovoltaic device with WHMM radiator has a similar power and conversion efficiency to that with the HMM radiator. The influence of the substrate can be ignored when the hyperbolic metamaterial is thicker than 140 nm, very beneficial to the actual fabrication of the device. By our system, with multilayer hyperbolic metamaterial (HMM) radiator, a high electric power &gt;1 W/m&lt;sup&gt;2&lt;/sup&gt; and a conversion efficiency about 11% can be obtained at a bias temperature of 200 K and a 100 nm vacuum gap. Compared with nanowire arrays or natural hyperbolic material, the multilayer structure proposed in this paper has obvious advantages in bandwidth and manufacturing and may find important applications in near-field thermophotovoltaic device and other relevant areas.

Evolution of quasi-history of the Planck blackbody radiation equation in a physics textbook

In physics textbooks, the emphasis is normally placed on the physics. In order to give the subject a deeper dimension, the inclusion of history and persons involved in the development has been increasing. However, the actual historical development does not always follow a linear progression, which is the way the physics is presented in textbooks. In order to study how the inclusion of “history” has influenced the presentation, a study of the development of a well-known history in different editions of a physics textbook is done. The gradual development of a quasi-history is observed and possible explanations for this are investigated.

Identifying spasticity during gait by surface electromyography

This work presents experimental results of swirling pulverized coal flames from a 60kWth combustion chamber based on spectrometric (UV–VIS) measurements comparing conventional air-fuel and oxy-fuel conditions. Radiation of the flames investigated was collected by two different optical systems: first, by a non-intrusive narrow-angle optical system providing integrated line-of-sight radiation data, and second, by an intrusive cold-background optical probe that collects radiation from integrated line-of-sight radiation within a reduced measurement volume. The collected spectra were processed and fitted to the Planck black body radiation function in order to estimate solid particle temperatures and relative radiant fluxes. Atomic and molecular emission lines observed are also identified and compared between the flames studied. The data obtained provide valuable insight to the different flames investigated and helpful explanations of the significant observed differences between the flames. As expected, oxidant composition was found to have a major impact on flame radiation and measured temperatures. Experimental validation data from this type of configuration and flame conditions are scarce, thus, the data may serve as validation data for numerical models.

Experimental investigation of pulverized coal flames in CO2/O2- and N2/O2-atmospheres: Comparison of solid particle radiative characteristics

This work presents experimental results of swirling pulverized coal flames from a 60kWth combustion chamber based on spectrometric (UV–VIS) measurements comparing conventional air-fuel and oxy-fuel conditions. Radiation of the flames investigated was collected by two different optical systems: first, by a non-intrusive narrow-angle optical system providing integrated line-of-sight radiation data, and second, by an intrusive cold-background optical probe that collects radiation from integrated line-of-sight radiation within a reduced measurement volume. The collected spectra were processed and fitted to the Planck black body radiation function in order to estimate solid particle temperatures and relative radiant fluxes. Atomic and molecular emission lines observed are also identified and compared between the flames studied. The data obtained provide valuable insight to the different flames investigated and helpful explanations of the significant observed differences between the flames. As expected, oxidant composition was found to have a major impact on flame radiation and measured temperatures. Experimental validation data from this type of configuration and flame conditions are scarce, thus, the data may serve as validation data for numerical models.

Search for the Cosmic Neutrino Background

One expects three Cosmic Backgrounds: (1) The Cosmic Microwave Background (CMB) originated 380000 years after the Big Bang (BB). (2) The Neutrino Background decoupled about one second after the BB, while (3) the Cosmic Gravitational Wave Background created by the inflationary expansion decoupled directly after the BB. Only the Cosmic Microwave Background (CMB) has been detected and is well studied. Its spectrum follows Planck's black body radiation formula and shows a remarkable constant temperature of T0γ ≈ 2.7 K independent of the direction. The present photon density is about 370 photons per cm3. The size of the hot spots, which deviates only in the fifth decimal of the temperature from the average value, tells us, that the universe is flat. About 380 000 years after the Big Bang at a temperature of T0γ = 3000 K already in the matter dominated era the electrons combine with the protons and 4He and the photons move freely in the neutral universe and form the CMB. So the temperature and distribution of the photons give us information of the universe 380 000 years after the Big Bang. The Cosmic Neutrino Background (CνB) decoupled from matter already one second after the BB at a temperature of about 1010 K. Today their temperature is ~ 1.95 K and the average density is 56 electron-neutrinos and the total density of all neutrinos about 336 per cm3. Measurement of these neutrinos is an extremely challenging experimental problem which can hardly be solved with the present technologies. On the other hand it represents a tempting opportunity to check one of the key elements of the Big Bang Cosmology and to probe the early stages of the universe. The search for the CνB with the induced beta decay νe+3H → 3He + e− using KATRIN (KArlsruhe TRItium Neutrino experiment) is the topic of this contribution.

Nobel Prizes in Physics and Chemistry 2014: Celebrating the International Year of Light 2015, commemorating the Old Quantum Theory

2015 is the International Year of Light and Light-based Technologies (IYL), while the physics and chemistry Nobel Prizes 2014 are both about light. The work leading to the two prizes share the same basic theoretical foundation: when an electron jumps from a higher energy level to a lower energy level, the energy difference is transformed into a photon. This basic way of light generation is a key part of the Old Quantum Theory. Interestingly, the date of announcing the 2014 Nobel Prize for physics coincided with the birthdays of Niels Bohr and, especially, of Planck's blackbody radiation formula. In connection with the two 2014 Nobel Prizes, we recall the development of the Old Quantum Theory by Planck, Einstein and Bohr.

Symmetry and the order of events in time: the thermodynamics of blackbodies composed of positive or negative mass

I have previously proposed a discrete symmetry called CPM (charge-parity-mass) symmetry that defines matter as having positive mass and antimatter as having negative mass-both being involved in processes that proceed forward in time. I have generalized the second law of thermodynamics to describe and predict the order of events in time that take place in reversible thermodynamic systems composed of positive or negative mass. Here I extend the CPM symmetry to irreversible thermo-optical radiation systems characterized by the Stefan-Boltzmann law, Planck's blackbody radiation law, and Einstein's law of specific heat. The laws of radiation analyzed in terms of CPM symmetry may provide a fresh way of understanding old topics such as the photon and entropy and new topics such as the nonluminous substances in the universe known as dark matter.

Measurements of Temperature of a pilot lamp and the Planck's constant by Use of Planck Blackbody Radiation and Wien's Displacement Formula

Measurements of Temperature of a pilot lamp and the Planck's constant by Use of Planck Blackbody Radiation and Wien's Displacement Formula

Beta Decay and the Cosmic Neutrino Background

In 1964 Penzias and Wilson detected the Cosmic Microwave Background (CMB). Its spectrum follows Planck's black body radiation formula and shows a remark- able constant temperature of T0γ ≈ 2.7 K independent of the direction. The present photon density is about 370 photons per cm 3 . The size of the hot spots, which deviates only in the fifth decimal of the temperature from the average value, tells us, that the uni- verse is flat. About 380 000 years after the Big Bang at a temperature of T0γ = 3000 K already in the matter dominated era the electrons combine with the protons and the 4 He and the photons move freely in the neutral universe. So the temperature and distribution of the photons give us information of the universe 380 000 years after the Big Bang. Information about earlier times can, in principle, be derived from the Cosmic Neutrino Background (CνB). The neutrinos decouple already 1 second after the Big Bang at a tem- perature of about 10 10 K. Today their temperature is ∼ 1.95 K and the average density is 56 electron-neutrinos per cm 3 . Registration of these neutrinos is an extremely challenging experimental problem which can hardly be solved with the present technologies. On the other hand it represents a tempting opportunity to check one of the key element of the Big Bang cosmology and to probe the early stages of the universe evolution. The search for the CνB with the induced beta decay νe + 3 H → 3 He+ e − is the topic of this contribution. The signal would show up by a peak in the electron spectrum with an energy of the neu- trino mass above the Q value. We discuss the prospects of this approach and argue that it is able to set limits on the CνB density in our vicinity. We also discuss critically ways to increase with modifications of the present KATRIN spectrometer the source intensity by a factor 100, which would yield about 170 counts of relic neutrino captures per year. This would make the detection of the Cosmic Neutrino Background possible. Presently such an increase seems not to be possible. But one should be able to find an upper limit for the local density of the relic neutrinos (Cosmic Neutrino Background) in our galaxy.

Regularization of fluctuations near the sonic horizon due to the quantum potential and its influence on Hawking radiation

We consider dynamics of fluctuations in transonically accelerating Bose-Einstein condensates and/or luminous fluids using the hydrodynamic approach. It is known that neglecting the quantum potential (QP) leads to a singular behavior of quantum and classical fluctuations in the vicinity of the Mach (sonic) horizon, which in turn gives rise to Hawking radiation. The neglect of the QP is well founded at not too small distances $|x|\ensuremath{\gg}{l}_{h}$ from the horizon, where ${l}_{h}$ is the healing length. Taking the QP into account, we show that a second characteristic length ${l}_{r}&gt;{l}_{h}$ exists, such that the linear fluctuation modes become regularized for $|x|\ensuremath{\ll}{l}_{r}$. At $|x|\ensuremath{\gg}{l}_{r}$ the modes keep their singular behavior, which, however, is influenced by the QP. As a result we find a deviation of the high frequency tail of the spectrum of Hawking radiation from Planck's black-body radiation distribution, which can be described by an effective Hawking temperature decreasing with increasing frequency.

Bose-Einstein condensation of photons in a 'white-wall' photon box

Bose-Einstein condensation, the macroscopic ground state occupation of a system of bosonic particles below a critical temperature, has been observed in cold atomic gases and solid-state physics quasiparticles. In contrast, photons do not show this phase transition usually, because in Planck's blackbody radiation the particle number is not conserved and at low temperature the photons disappear in the walls of the system. Here we report on the realization of a photon Bose-Einstein condensate in a dye-filled optical microcavity, which acts as a "white-wall" photon box. The cavity mirrors provide a trapping potential and a non-vanishing effective photon mass, making the system formally equivalent to a two-dimensional gas of trapped massive bosons. Thermalization of the photon gas is reached in a number conserving way by multiple scattering off the dye molecules. Signatures for a BEC upon increased photon density are: a spectral distribution that shows Bose-Einstein distributed photon energies with a macroscopically populated peak on top of a broad thermal wing, the observed threshold of the phase transition showing the predicted absolute value and scaling with resonator geometry, and condensation appearing at the trap centre even for a spatially displaced pump spot.

Space-resolved Spectrometric Measurements of the Cutting Front

The most important factor influencing the maximum cutting speed is the absorbed laser power distribution. As the polarization of the cutting laser beam influences the local absorption, the temperature of the cutting front varies using differently polarized laser beams. To determine the local temperature the emission spectra of cuts with a radially polarized CO2-laser were measured and compared with emission spectra of cuts with a circularly polarized beam. The spectra were used to determine the space resolved temperature by fitting with the Planck black-body radiation in the case of predominantly continuum emission and with the spectral lines of Fe I in the case of spectra dominated by line emission.

Double layer 반사방지막 구조에 대한 태양전지 표면 반사율 simulation

In this paper, we conducted MATLAB simulation using the reflectance formula and the Planck's black body radiation principle, for the purpose of identifying the opimum material and thickness of anti-reflective coating from double layered structures. We found that the optimum condition was obtained when refractive index of upper layer is 1.44 and that of lower layer is 2.29. As materials close to these refractive indices, as the upper layer and , ZnS, as the lower layer were suggested. The best result in an average reflectance of 2.759% was obtained from a double layered structure of 94 nm/ZnS 55 nm.

Surface Phonon Polaritons Mediated Energy Transfer between Nanoscale Gaps

Surface phonon polaritons are electromagnetic waves that propagate along the interfaces of polar dielectrics and exhibit a large local-field enhancement near the interfaces at infrared frequencies. Theoretical calculations show that such surface waves can lead to breakdown of the Planck's blackbody radiation law in the near field. Here, we experimentally demonstrate that surface phonon polaritons dramatically enhance energy transfer between two surfaces at small gaps by measuring radiation heat transfer between a microsphere and a flat surface down to 30 nm separation. The corresponding heat transfer coefficients at nanoscale gaps are 3 orders of magnitude larger than that of the blackbody radiation limit. The high energy flux can be exploited to develop new radiative cooling and thermophotovoltaic technologies.

Breakdown of the Planck blackbody radiation law at nanoscale gaps

The Planck theory of blackbody radiation imposes a limit on the maximum radiative transfer between two objects at given temperatures. When the two objects are close enough, near-field effects due to tunneling of evanescent waves lead to enhancement of radiative transfer above the Planck limit. When the objects can support electromagnetic surface polaritons, the enhancement can be a few orders-of-magnitude larger than the blackbody limit. In this paper, we summarize our recent measurements of radiative transfer between two parallel silica surfaces and between a silica microsphere and a flat silica surface that show unambiguous evidence of enhancement of radiative transfer due to near-field effects above the Planck limit.

Near-field radiative heat transfer between a sphere and a substrate

Near-field force and energy exchange between two objects due to quantum electrodynamic fluctuations give rise to interesting phenomena such as Casimir and van der Waals forces and thermal radiative transfer exceeding Planck's theory of blackbody radiation. Although significant progress has been made in the past on the precise measurement of Casimir force related to zero-point energy, experimental demonstration of near-field enhancement of radiative heat transfer is difficult. In this work, we present a sensitive technique of measuring near-field radiative transfer between a microsphere and a substrate using a bimaterial atomic force microscope cantilever, resulting in ``heat transfer-distance'' curves. Measurements of radiative transfer between a sphere and a flat substrate show the presence of strong near-field effects resulting in enhancement of heat transfer over the predictions of the Planck blackbody radiation theory.