Comparison of Blackbody Sources for Low-Temperature IR Calibration

NASA Astrophysics Data System (ADS)

Ljungblad, S.; Holmsten, M.; Josefson, L. E.; Klason, P.

2015-12-01

Radiation thermometers are traditionally mostly used in high-temperature applications. They are, however, becoming more common in different applications at room temperature or below, in applications such as monitoring frozen food and evaluating heat leakage in buildings. To measure temperature accurately with a pyrometer, calibration is essential. A problem with traditional, commercially available, blackbody sources is that ice is often formed on the surface when measuring temperatures below 0°C. This is due to the humidity of the surrounding air and, as ice does not have the same emissivity as the blackbody source, it biases the measurements. An alternative to a traditional blackbody source has been tested by SP Technical Research Institute of Sweden. The objective is to find a cost-efficient method of calibrating pyrometers by comparison at the level of accuracy required for the intended use. A disc-shaped blackbody with a surface pyramid pattern is placed in a climatic chamber with an opening for field of view of the pyrometer. The temperature of the climatic chamber is measured with two platinum resistance thermometers in the air in the vicinity of the disc. As a rule, frost will form only if the deposition surface is colder than the surrounding air, and, as this is not the case when the air of the climatic chamber is cooled, there should be no frost or ice formed on the blackbody surface. To test the disc-shaped blackbody source, a blackbody cavity immersed in a conventional stirred liquid bath was used as a reference blackbody source. Two different pyrometers were calibrated by comparison using the two different blackbody sources, and the results were compared. The results of the measurements show that the disc works as intended and is suitable as a blackbody radiation source.

A history of slide rules for blackbody radiation computations

NASA Astrophysics Data System (ADS)

Johnson, R. Barry; Stewart, Sean M.

2012-10-01

During the Second World War the importance of utilizing detection devices capable of operating in the infrared portion of the electromagnetic spectrum was firmly established. Up until that time, laboriously constructed tables for blackbody radiation needed to be used in calculations involving the amount of radiation radiated within a given spectral region or for other related radiometric quantities. To rapidly achieve reasonably accurate calculations of such radiometric quantities, a blackbody radiation calculator was devised in slide rule form first in Germany in 1944 and soon after in England and the United States. In the immediate decades after its introduction, the radiation slide rule was widely adopted and recognized as a useful and important tool for engineers and scientists working in the infrared field. It reached its pinnacle in the United States in 1970 in a rule introduced by Electro Optical Industries, Inc. With the onset in the latter half of the 1970s of affordable, hand-held electronic calculators, the impending demise of the radiation slide rule was evident. No longer the calculational device of choice, the radiation slide rule all but disappeared within a few short years. Although today blackbody radiation calculations can be readily accomplished using anything from a programmable pocket calculator upwards, with each device making use of a wide variety of numerical approximations to the integral of Planck's function, radiation slide rules were in the early decades of infrared technology the definitive "workhorse" for those involved in infrared systems design and engineering. This paper presents a historical development of radiation slide rules with many versions being discussed.

Comics in Modern Physics: Learning Blackbody Radiation through Quasi-History of Physics

ERIC Educational Resources Information Center

Ozdemir, Ertugrul

2017-01-01

The purpose of this study is to create a short comic story about historical emergence of Planck's explanation of blackbody radiation and to investigate what students learn from it and what they think about the usage of comics in modern physics course. The participants are a small group of undergraduate students studying at department of science…

New blackbody calibration source for low temperatures from -20 C to +350 C

NASA Astrophysics Data System (ADS)

Mester, Ulrich; Winter, Peter

2001-03-01

Calibration procedures for infrared thermometers and thermal imaging systems require radiation sources of precisely known radiation properties. In the physical absence of an ideal Planck's radiator, the German Committee VDI/VDE-GMA FA 2.51, 'Applied Radiation Thermometry', agreed upon desirable specifications and limiting parameters for a blackbody calibration source with a temperature range from -20 degree(s)C to +350 degree(s)C, a spectral range from 2 to 15 microns, an emissivity greater than 0.999 and a useful source aperture of 60 mm, among others. As a result of the subsequent design and development performed with the support of the laboratory '7.31 Thermometry' of the German national institute of natural and engineering sciences (PTB), the Mester ME20 Blackbody Calibration Source is presented. The ME20 meets or exceeds all of the specifications formulated by the VDI/VDE committee.

Research on H500-Type High-Precision Vacuum Blackbody as a Calibration Standard for Infrared Remote Sensing

NASA Astrophysics Data System (ADS)

Hao, X. P.; Sun, J. P.; Gong, L. Y.; Song, J.; Gu, J. M.; Ding, L.

2018-04-01

Based on the calibration requirements of vacuum low background aerospace infrared remote sensing radiance temperature, a high-precision vacuum blackbody (H500 type) is developed for the temperature range from - 93 °C to + 220 °C at the National Institute of Metrology, China. In this paper, the structure and the temperature control system of H500 are introduced, and its performance, such as heating rate and stabilization of temperature control, is tested under the vacuum and low-background condition (liquid-nitrogen-cooled shroud). At room temperature and atmospheric environment, the major technical parameters of this blackbody, such as emissivity and uniformity, are measured. The measurement principle of blackbody emissivity is based on the control of surrounding radiation. Temperature uniformity at the cavity bottom is measured using a standard infrared radiation thermometer. When the heating rate is 1 °C min-1, the time required for the temperature to stabilize is less than 50 min, and within 10 min, the variation in temperature is less than 0.01 °C. The emissivity value of the blackbody is higher than 0.996. Temperature uniformity at the bottom of the blackbody cavity is less than 0.03 °C. The uncertainty is less than 0.1 °C ( k = 2) over the temperature range from - 93 °C to + 67 °C.

Thermodynamic limits to the conversion of blackbody radiation by quantum systems. [with application to solar energy conversion devices

NASA Technical Reports Server (NTRS)

Buoncristiani, A. M.; Smith, B. T.; Byvik, C. E.

1982-01-01

Using general thermodynamic arguments, we analyze the conversion of the energy contained in the radiation from a blackbody to useful work by a quantum system. We show that the energy available for conversion is bounded above by the change in free energy in the incident and reradiated fields and that this free energy change depends upon the temperature of the receiving device. Universal efficiency curves giving the ultimate thermodynamic conversion efficiency of the quantum system are presented in terms of the blackbody temperature and the temperature and threshold energy of the quantum system. Application of these results is made to a variety of systems including biological photosynthetic, photovoltaic, and photoelectrochemical systems.

Local thermodynamic equilibrium in a laser-induced plasma evidenced by blackbody radiation

NASA Astrophysics Data System (ADS)

Hermann, Jörg; Grojo, David; Axente, Emanuel; Craciun, Valentin

2018-06-01

We show that the plasma produced by laser ablation of solid materials in specific conditions has an emission spectrum that is characterized by the saturation of the most intense spectral lines at the blackbody radiance. The blackbody temperature equals the excitation temperature of atoms and ions, proving directly and unambiguously a plasma in local thermodynamic equilibrium. The present investigations take benefit from the very rich and intense emission spectrum generated by ablation of a nickel-chromium-molybdenum alloy. This alternative and direct proof of the plasma equilibrium state re-opens the perspectives of quantitative material analyses via calibration-free laser-induced breakdown spectroscopy. Moreover, the unique properties of this laser-produced plasma promote its use as radiation standard for intensity calibration of spectroscopic instruments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ojanen, M.; Hahtela, O. M.; Heinonen, M.

MIKES is developing a measurement set-up for calibrating thermocouples in the temperature range 960 °C - 1500 °C. The calibration method is based on direct comparison of thermocouples and radiation thermometers. We have designed a graphite blackbody comparator cell, which is operated in a horizontal single-zone tube furnace. The cell includes two blackbody cavities for radiation temperature measurements. The cavities have openings on opposite sides of the cell, allowing simultaneous measurement with two radiation thermometers. The design of the comparator allows three thermocouples to be calibrated simultaneously. The thermocouples to be calibrated are inserted in thermometer wells around one ofmore » the measurement cavities. We characterize the blackbody comparator in terms of repeatability, temperature distribution and emissivity. Finally, we validate the uncertainty analysis by comparing calibration results obtained for type B and S thermocouples to the calibration results reported by Technical Research Institute of Sweden (SP), and MIKES. The agreement in the temperature range 1000 °C - 1500 °C is within 0.90 °C, the average deviation being 0.17 °C.« less

Radiative transitions from Rydberg states of lithium atoms in a blackbody radiation environment

NASA Astrophysics Data System (ADS)

Glukhov, I. L.; Ovsiannikov, V. D.

2012-05-01

The radiative widths induced by blackbody radiation (BBR) were investigated for Rydberg states with principal quantum number up to n = 1000 in S-, P- and D-series of the neutral lithium atom at temperatures T = 100-3000 K. The rates of BBR-induced decays and excitations were compared with the rates of spontaneous decays. Simple analytical approximations are proposed for accurate estimations of the ratio of thermally induced decay (excitation) rates to spontaneous decay rates in wide ranges of states and temperatures.

Blackbody Radiation from an Incandescent Lamp

ERIC Educational Resources Information Center

Ribeiro, C. I.

2014-01-01

In this article we propose an activity aimed at introductory students to help them understand the Stefan-Boltzmann and Wien's displacement laws. It only requires simple materials that are available at any school: an incandescent lamp, a variable dc energy supply, and a computer to run an interactive simulation of the blackbody spectrum.…

Two-Step Calibration of a Multiwavelength Pyrometer for High Temperature Measurement Using a Quartz Lamp

NASA Technical Reports Server (NTRS)

Ng, Daniel

2001-01-01

There is no theoretical upper temperature limit for pyrometer application in temperature measurements. NASA Glenn's multiwavelength pyrometer can make measurements over wide temperature ranges. However, the radiation spectral response of the pyrometer's detector must be calibrated before any temperature measurement is attempted, and it is recommended that calibration be done at temperatures close to those for which measurements will be made. Calibration is a determination of the constants of proportionality at all wavelengths between the detector's output (voltage) and its input signals (usually from a blackbody radiation source) in order to convert detector output into radiation intensity. To measure high temperatures, the detectors are chosen to be sensitive in the spectral range from 0.4 to 2.5 micrometers. A blackbody furnace equilibrated at around 1000 C is often used for this calibration. Though the detector may respond sensitively to short wavelengths radiation, a blackbody furnace at 1000 C emits only feebly at very short wavelengths. As a consequence, the calibration constants that result may not be the most accurate. For pyrometry calibration, a radiation source emitting strongly at the short wavelengths is preferred. We have chosen a quartz halogen lamp for this purpose.

Enhancement radiative cooling performance of nanoparticle crystal via oxidation

NASA Astrophysics Data System (ADS)

Jia, Zi-Xun; Shuai, Yong; Li, Meng; Guo, Yanmin; Tan, He-ping

2018-03-01

Nanoparticle-crystal is a promising candidate for large scale metamaterial fabrication. However, in radiative cooling application, the maximum blackbody radiation wavelength locates far from metal's plasmon wavelength. In this paper, it will be shown if the metallic nanoparticle crystal can be properly oxidized, the absorption performance within room temperature blackbody radiation spectrum can be improved. Magnetic polariton and surface plasmon polariton have been explained for the mechanism of absorption improvement. Three different oxidation patterns have been investigated in this paper, and the results show they share a similar enhancing mechanism.

Measurement and Analysis of the Temperature Gradient of Blackbody Cavities, for Use in Radiation Thermometry

NASA Astrophysics Data System (ADS)

De Lucas, Javier; Segovia, José Juan

2018-05-01

Blackbody cavities are the standard radiation sources widely used in the fields of radiometry and radiation thermometry. Its effective emissivity and uncertainty depend to a large extent on the temperature gradient. An experimental procedure based on the radiometric method for measuring the gradient is followed. Results are applied to particular blackbody configurations where gradients can be thermometrically estimated by contact thermometers and where the relationship between both basic methods can be established. The proposed procedure may be applied to commercial blackbodies if they are modified allowing secondary contact temperature measurement. In addition, the established systematic may be incorporated as part of the actions for quality assurance in routine calibrations of radiation thermometers, by using the secondary contact temperature measurement for detecting departures from the real radiometrically obtained gradient and the effect on the uncertainty. On the other hand, a theoretical model is proposed to evaluate the effect of temperature variations on effective emissivity and associated uncertainty. This model is based on a gradient sample chosen following plausible criteria. The model is consistent with the Monte Carlo method for calculating the uncertainty of effective emissivity and complements others published in the literature where uncertainty is calculated taking into account only geometrical variables and intrinsic emissivity. The mathematical model and experimental procedure are applied and validated using a commercial type three-zone furnace, with a blackbody cavity modified to enable a secondary contact temperature measurement, in the range between 400 °C and 1000 °C.

High temperature blackbody BB2000/40 for calibration of radiation thermometers and thermocouple

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogarev, S. A.; Khlevnoy, B. B.; Samoylov, M. L.

2013-09-11

The cavity-type high temperature blackbody (HTBB) models of BB3200/3500 series are the most spread among metrological institutes worldwide as sources for radiometry and radiation thermometry, due to their ultra high working temperatures, high emissivity and stability. The materials of radiating cavities are graphite, pyrolytic graphite (PG) and their combination. The paper describes BB2000/40 blackbody with graphite-tube cavity that was developed for calibration of radiation thermometers at SCEI (Singapore). The peculiarity of BB2000/40 is a possibility to use it, besides calibration of pyrometers, as an instrument for thermocouples calibration. Operating within the temperature range from 900 °C to 2000 °C, themore » blackbody has a wide cavity opening of 40 mm. Emissivity of the cavity, with PG heater rings replaced partly by graphite elements, was estimated as 0.998 ± 0.0015 in the spectral range from 350 nm to 2000 nm. The uniformity along the cavity axis, accounting for 10 °C, was measured using a B-type thermocouple at 1500 °C. The BB2000/40, if necessary, can be easily modified, by replacing the graphite radiator with a set of PG rings, to be able to reach temperatures as high as 3200 °C. The HTBB utilizes an optical feedback system which allows temperature stabilization within 0.1 °C. This rear-view feedback allows the whole HTBB aperture to be used for measurements.« less

Time resolved analysis of Fermi gamma-ray bursts with fast-and slow-cooled synchrotron photon models

DOE PAGES

Burgess, J. M.; Preece, R. D.; Connaughton, V.; ...

2014-02-27

Time-resolved spectroscopy is performed on eight bright, long gamma-ray bursts (GRBs) dominated by single emission pulses that were observed with the Fermi Gamma-Ray Space Telescope. Fitting the prompt radiation of GRBs by empirical spectral forms such as the Band function leads to ambiguous conclusions about the physical model for the prompt radiation. Moreover, the Band function is often inadequate to fit the data. Therefore, the GRB spectrum is modeled with two emission components consisting of optically thin non-thermal synchrotron radiation from relativistic electrons and, when significant, thermal emission from a jet photosphere, which is represented by a blackbody spectrum. Inmore » order to produce an acceptable fit, the addition of a blackbody component is required in five out of the eight cases. We also find that the low-energy spectral index α is consistent with a synchrotron component with α = –0.81 ± 0.1. This value lies between the limiting values of α = –2/3 and α = –3/2 for electrons in the slow- and fast-cooling regimes, respectively, suggesting ongoing acceleration at the emission site. The blackbody component can be more significant when using a physical synchrotron model instead of the Band function, illustrating that the Band function does not serve as a good proxy for a non-thermal synchrotron emission component. The temperature and characteristic emission-region size of the blackbody component are found to, respectively, decrease and increase as power laws with time during the prompt phase. Additionally, we find that the blackbody and non-thermal components have separate temporal behaviors as far as their respective flux and spectral evolutions.« less

Fresnel Lens Solar Concentrator Design Based on Geometric Optics and Blackbody Radiation Equations

NASA Technical Reports Server (NTRS)

Watson, Michael D.; Jayroe, Robert, Jr.

1999-01-01

Fresnel lenses have been used for years as solar concentrators in a variety of applications. Several variables effect the final design of these lenses including: lens diameter, image spot distance from the lens, and bandwidth focused in the image spot. Defining the image spot as the geometrical optics circle of least confusion and applying blackbody radiation equations the spot energy distribution can be determined. These equations are used to design a fresnel lens to produce maximum flux for a given spot size, lens diameter, and image distance. This approach results in significant increases in solar efficiency over traditional single wavelength designs.

Studies of CW lasing action in CO2-CO, N2O-CO, CO2-H2O, and N2O-H2O mixtures pumped by blackbody radiation

NASA Technical Reports Server (NTRS)

Abel, Robert W.; Christiansen, Walter H.; Li, Jian-Guo

1988-01-01

A proof of principle experiment to evaluate the efficacy of CO and H2O in increasing the power output for N2O and CO2 lasing mixtures has been conducted and theoretically analyzed for a blackbody radiation-pumped laser. The results for N2O-CO, CO2-CO, N2O-H2O and CO2-H2O mixtures are presented. Additions of CO to the N2O lasant increased power up to 28 percent for N2O laser mixtures, whereas additions of CO to the CO2 lasant, and the addition of H2O to both the CO2 and N2O lasants, resulted in decreased output power.

High speed infrared radiation thermometer, system, and method

DOEpatents

Markham, James R.

2002-01-01

The high-speed radiation thermometer has an infrared measurement wavelength band that is matched to the infrared wavelength band of near-blackbody emittance of ceramic components and ceramic thermal barrier coatings used in turbine engines. It is comprised of a long wavelength infrared detector, a signal amplifier, an analog-to-digital converter, an optical system to collect radiation from the target, an optical filter, and an integral reference signal to maintain a calibrated response. A megahertz range electronic data acquisition system is connected to the radiation detector to operate on raw data obtained. Because the thermometer operates optimally at 8 to 12 .mu.m, where emittance is near-blackbody for ceramics, interferences to measurements performed in turbine engines are minimized. The method and apparatus are optimized to enable mapping of surface temperatures on fast moving ceramic elements, and the thermometer can provide microsecond response, with inherent self-diagnostic and calibration-correction features.

External inverse-Compton emission from jetted tidal disruption events

NASA Astrophysics Data System (ADS)

Lu, Wenbin; Kumar, Pawan

2016-05-01

The recent discoveries of Sw J1644+57 and Sw J2058+05 show that tidal disruption events (TDEs) can launch relativistic jets. Super-Eddington accretion produces a strong radiation field of order Eddington luminosity. In a jetted TDE, electrons in the jet will inverse-Compton scatter the photons from the accretion disc and wind (external radiation field). Motivated by observations of thermal optical-UV spectra in Sw J2058+05 and several other TDEs, we assume the spectrum of the external radiation field intercepted by the relativistic jet to be blackbody. Hot electrons in the jet scatter this thermal radiation and produce luminosities 1045-1048 erg s- 1 in the X/γ-ray band. This model of thermal plus inverse-Compton radiation is applied to Sw J2058+05. First, we show that the blackbody component in the optical-UV spectrum most likely has its origin in the super-Eddington wind from the disc. Then, using the observed blackbody component as the external radiation field, we show that the X-ray luminosity and spectrum are consistent with the inverse-Compton emission, under the following conditions: (1) the jet Lorentz factor is Γ ≃ 5-10; (2) electrons in the jet have a power-law distribution dN_e/dγ _e ∝ γ _e^{-p} with γmin ˜ 1 and p = 2.4; (3) the wind is mildly relativistic (Lorentz factor ≳ 1.5) and has isotropic-equivalent mass-loss rate ˜ 5 M⊙ yr- 1. We describe the implications for jet composition and the radius where jet energy is converted to radiation.

On Blackbody Radiation.

ERIC Educational Resources Information Center

Jain, Pushpendra K.

1991-01-01

The interrelationship between the various forms of the Planck radiation equation is discussed. A differential equation that gives intensity or energy density of radiation per unit wavelength or per unit frequency is emphasized. The Stefan-Boltzmann Law and the change in the glow of a hot body with temperature are also discussed. (KR)

Upconversion luminescence and blackbody radiation in tetragonal YSZ co-doped with Tm(3+) and Yb(3+).

PubMed

Soares, M R N; Ferro, M; Costa, F M; Monteiro, T

2015-12-21

Lanthanide doped inorganic nanoparticles with upconversion luminescence are of utmost importance for biomedical applications, solid state lighting and photovoltaics. In this work we studied the downshifted luminescence, upconversion luminescence (UCL) and blackbody radiation of tetragonal yttrium stabilized zirconia co-doped with Tm(3+) and Yb(3+) single crystals and nanoparticles produced by laser floating zone and laser ablation in liquids, respectively. The photoluminescence (PL) and PL excitation (PLE) were investigated at room temperature (RT). PL spectra exhibit the characteristic lines in UV, blue/green, red and NIR regions of the Tm(3+) (4f(12)) under resonant excitation into the high energy (2S+1)LJ multiplets. Under NIR excitation (980 nm), the samples placed in air display an intense NIR at ∼800 nm due to the (1)G4→(3)H5/(3)H4→(3)H6 transitions. Additionally, red, blue/green and ultraviolet UCL is observed arising from higher excited (1)G4 and (1)D2 multiplets. The power excitation dependence of the UCL intensity indicated that 2-3 low energy absorbed photons are involved in the UCL for low power levels, while for high powers, the identified saturation is dependent on the material size with a enhanced effect on the NPs. The temperature dependence of the UCL was investigated for single crystals and targets used in the ablation. An overall increase of the integrated intensity was found to occur between 12 K and the RT. The thermally activated process is described by activation energies of 10 meV and 30 meV for single crystals and targets, respectively. For the NPs, the UCL was found to be strongly sensitive to pressure conditions. Under vacuum conditions, instead of the narrow lines of the Tm(3+), a wide blackbody radiation was detected, responsible for the change in the emission colour from blue to orange. This phenomenon is totally reversible when the NPs are placed at ambient pressure. The UCL/blackbody radiation in the nanosized material exhibits non-contact pressure colour-based sensor characteristics. Moreover, tuning the color of the blackbody radiation in the nanoparticles by harvesting the low energy photons into the visible spectral region was found to be possible by adjusting the excitation power, paving the way for further developments of these nanoparticles for lighting and photovoltaic applications.

A new concept for solar pumped lasers

NASA Technical Reports Server (NTRS)

Christiansen, W. H.

1978-01-01

A new approach is proposed in which an intermediate body heated by sunlight is used as the pumping source for IR systems, i.e., concentration solar radiation is absorbed and reradiated via an intermediate blackbody. This body is heated by focused sunlight to a high temperature and its heat losses are engineered to be small. The cooled laser tube (or tubes) is placed within the cavity and is pumped by it. The advantage is that the radiation spectrum is like a blackbody at the intermediate temperature and the laser medium selectively absorbs this light. Focusing requirements, heat losses, and absorption bandwidths of laser media are examined, along with energy balance and potential efficiency. The results indicate that for lasers pumped through an IR absorption spectrum, the use of an intermediate blackbody offers substantial and important advantages. The loss in radiative intensity for optical pumping by a lower-temperature body is partly compensated by the increased solid angle of exposure to the radiative environment.

Anisotropy of the cosmic blackbody radiation

NASA Technical Reports Server (NTRS)

Wilkinson, D. T.

1986-01-01

The universe is filled with thermal radiation having a current temperature of 2.75 K. Originating in the very early universe, this radiation furnishes strong evidence that the Big Bang cosmology best describes our expanding universe from an incredibly hot, compacted early stage until now. The model can be used to extrapolate our physics backward in time to predict events whose effects might be observable in the 2.75 K radiation today. The spectrum and isotropy are being studied with sophisticated microwave radiometers on the ground, in balloons, and in satellites. The results are as predicted by the simple theory: the spectrum is that of a blackbody (to a few percent) and the radiation is isotropic (to 0.01 percent) except for a local effect due to our motion through the radiation. However, a problem is emerging. Primordial fluctuations in the mass density, which later became the great clusters of galaxies that we see today, should have left an imprint on the 2.75 K radiation - bumpiness on the sky at angular scales of about 10 arc minutes. They have not been seen.

Quasiclassical calculations of blackbody-radiation-induced depopulation rates and effective lifetimes of Rydberg nS, nP, and nD alkali-metal atoms with n{<=}80

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beterov, I. I.; Ryabtsev, I. I.; Tretyakov, D. B.

2009-05-15

Rates of depopulation by blackbody radiation (BBR) and effective lifetimes of alkali-metal nS, nP, and nD Rydberg states have been calculated in a wide range of principal quantum numbers n{<=}80 at the ambient temperatures of 77, 300, and 600 K. Quasiclassical formulas were used to calculate the radial matrix elements of the dipole transitions from Rydberg states. Good agreement of our numerical results with the available theoretical and experimental data has been found. We have also obtained simple analytical formulas for estimates of effective lifetimes and BBR-induced depopulation rates, which well agree with the numerical data.

Anisotropy of the cosmic blackbody radiation.

PubMed

Wilkinson, D T

1986-06-20

The universe is filled with thermal radiation having a current temperature of 2.75 K. Originating in the very early universe, this radiation furnishes strong evidence that the Big Bang cosmology best describes our expanding universe from an incredibly hot, compacted early stage until now. The model can be used to extrapolate our physics backward in time to predict events whose effects might be observable in the 2.75 K radiation today. The spectrum and isotropy are being studied with sophisticated microwave radiometers on the ground, in balloons, and in satellites. The results are as predicted by the simple theory: the spectrum is that of a blackbody (to a few percent) and the radiation is isotropic (to 0.01 percent) except for a local effect due to our motion through the radiation. However, a problem is emerging. Primordial fluctuations in the mass density, which later became the great clusters of galaxies that we see today, should have left an imprint on the 2.75 K radiation-bumpiness on the sky at angular scales of about 10 arc minutes. They have not yet been seen.

Using Stellar Spectra to Illustrate Thermal Radiation Laws

ERIC Educational Resources Information Center

Kaltcheva, N. T.; Pritzl, B. J.

2018-01-01

Stars are point-source emitters that are the closest to the definition of a blackbody in comparison to all other similar sources of radiation found in nature. Existing libraries on stellar spectra are thus a valuable resource that can be used to introduce the laws of thermal radiation in a classroom setting. In this article we briefly describe…

Solar pumped continuous wave carbon dioxide laser

NASA Technical Reports Server (NTRS)

Yesil, O.; Christiansen, W. H.

1978-01-01

In an effort to demonstrate the feasibility of a solar pumped laser concept, gain has been measured in a CO2-He laser medium optically pumped by blackbody radiation. Various gas mixtures of CO2 and He have been pumped by blackbody radiation emitted from an electrically heated oven. Using a CO2 laser as a probe, an optical gain coefficient of 1.8 x 10 to the -3rd/cm has been measured at 10.6 microns for a 9:1 CO2-He mixture at an oven temperature of about 1500 K, a gas temperature of about 400 K and a pressure of about 1 torr. This corresponds to a small signal gain coefficient when allowance is made for saturation effects due to the probe beam, in reasonable agreement with a theoretical value.

Tunability of the circadian action of tetrachromatic solid-state light sources

NASA Astrophysics Data System (ADS)

Žukauskas, A.; Vaicekauskas, R.

2015-01-01

An approach to the optimization of the spectral power distribution of solid-state light sources with the tunable non-image forming photobiological effect on the human circadian rhythm is proposed. For tetrachromatic clusters of model narrow-band (direct-emission) light-emitting diodes (LEDs), the limiting tunability of the circadian action factor (CAF), which is the ratio of the circadian efficacy to luminous efficacy of radiation, was established as a function of constraining color fidelity and luminous efficacy of radiation. For constant correlated color temperatures (CCTs), the CAF of the LED clusters can be tuned above and below that of the corresponding blackbody radiators, whereas for variable CCT, the clusters can have circadian tunability covering that of a temperature-tunable blackbody radiator.

Some considerations for a method that simultaneously measures the temperature and emissivity of a metal in a high temperature furnace

NASA Astrophysics Data System (ADS)

Iuchi, Tohru; Furukawa, Tohru

2004-12-01

This article describes some considerations for designing a practical radiation thermometry system for a glossy metal moving through a high temperature furnace, such as a continuous annealing furnace. In order to accomplish this task, two problems must be solved. The emissivity compensation of an object must be calculated and the furnace's background radiation noise must be eliminated. The authors have proposed a method that uses the radiance's polarized directional properties to simultaneously measure the emissivity and temperature to solve the first problem and a technique using a pseudo-blackbody installed in the furnace to solve the second problem. During heating, there is a one-to-one correspondence between the emissivity and the ratio of p- and s-polarized radiances for metals. This characteristic has successfully led to the development of a method for simultaneously measuring the emissivity and temperature of metals regardless of a potential large change in emissivity. Introducing a pseudo-blackbody radiator into a furnace removes the background radiation noise. Moreover, the blackbody radiator supplies a constant reference radiance. This reference plays an important role in maintaining the principle of emissivity-compensated radiation thermometry inside the furnace. Experimental results have simultaneously measured the emissivity and temperature of stainless steel at 1300 K with errors of 12% and 0.96%, respectively. These values were attained even though the s-polarized emissivities change from 0.25 to 0.75 at a wavelength of 0.9 μm. These errors can be achieved by designing the apparatus to have a solid angle, the aperture of the pseudo-blackbody subtended by a measuring point of the specimen, of more than 0.02π steradians. The accuracy of this method is heavily dependent upon the specimen's surface roughness. The maximum surface roughness that allows for the successful utilization of this method is Ra=0.12 μm.

A preliminary measurement of the cosmic microwave background spectrum by the Cosmic Background Explorer (COBE) satellite

NASA Technical Reports Server (NTRS)

Mather, J. C.; Cheng, E. S.; Shafer, R. A.; Bennett, C. L.; Boggess, N. W.; Dwek, E.; Hauser, M. G.; Kelsall, T.; Moseley, S. H., Jr.; Silverberg, R. F.

1990-01-01

A preliminary spectrum is presented of the background radiation between 1 and 20/cm from regions near the north Galactic pole, as observed by the FIRAS instrument on the COBE satellite. The spectral resolution is 1/cm. The spectrum is well fitted by a blackbody with a temperature of 2.735 + or - 0.06 K, and the deviation from a blackbody is less than 1 percent of the peak intensity over the range 1-20/cm. These new data show no evidence for the submillimeter excess previously reported by Matsumoto et al. (1988) in the cosmic microwave background. Further analysis and additional data are expected to improve the sensitivity to deviations from a blackbody spectrum by an order of magnitude.

The hottest planet.

PubMed

Harrington, Joseph; Luszcz, Statia; Seager, Sara; Deming, Drake; Richardson, L Jeremy

2007-06-07

Of the over 200 known extrasolar planets, just 14 pass in front of and behind their parent stars as seen from Earth. This fortuitous geometry allows direct determination of many planetary properties. Previous reports of planetary thermal emission give fluxes that are roughly consistent with predictions based on thermal equilibrium with the planets' received radiation, assuming a Bond albedo of approximately 0.3. Here we report direct detection of thermal emission from the smallest known transiting planet, HD 149026b, that indicates a brightness temperature (an expression of flux) of 2,300 +/- 200 K at 8 microm. The planet's predicted temperature for uniform, spherical, blackbody emission and zero albedo (unprecedented for planets) is 1,741 K. As models with non-zero albedo are cooler, this essentially eliminates uniform blackbody models, and may also require an albedo lower than any measured for a planet, very strong 8 microm emission, strong temporal variability, or a heat source other than stellar radiation. On the other hand, an instantaneous re-emission blackbody model, in which each patch of surface area instantly re-emits all received light, matches the data. This planet is known to be enriched in heavy elements, which may give rise to novel atmospheric properties yet to be investigated.

Single-fiber multi-color pyrometry

DOEpatents

Small, IV, Ward; Celliers, Peter

2004-01-27

This invention is a fiber-based multi-color pyrometry set-up for real-time non-contact temperature and emissivity measurement. The system includes a single optical fiber to collect radiation emitted by a target, a reflective rotating chopper to split the collected radiation into two or more paths while modulating the radiation for lock-in amplification (i.e., phase-sensitive detection), at least two detectors possibly of different spectral bandwidths with or without filters to limit the wavelength regions detected and optics to direct and focus the radiation onto the sensitive areas of the detectors. A computer algorithm is used to calculate the true temperature and emissivity of a target based on blackbody calibrations. The system components are enclosed in a light-tight housing, with provision for the fiber to extend outside to collect the radiation. Radiation emitted by the target is transmitted through the fiber to the reflective chopper, which either allows the radiation to pass straight through or reflects the radiation into one or more separate paths. Each path includes a detector with or without filters and corresponding optics to direct and focus the radiation onto the active area of the detector. The signals are recovered using lock-in amplification. Calibration formulas for the signals obtained using a blackbody of known temperature are used to compute the true temperature and emissivity of the target. The temperature range of the pyrometer system is determined by the spectral characteristics of the optical components.

Cosmological implication of a new measurement of the submillimeter background radiation

NASA Technical Reports Server (NTRS)

Hayakawa, Satio; Matsumoto, Toshio; Matsuo, Hiroshi; Murakami, Hiroshi; Sato, Shinji

1987-01-01

A new submillimeter measurement of the cosmic background radiation (T. Matsumoto et al., 1988) reveals excess brightness between 1000 and 300 microns. The excess corresponds to about 10 percent of the undistorted blackbody radiation. The observed excess is consistent with thermal emission from dust with a relative density of 0.0001-0.00001, if the dust is heated at a redshift z of about 10-40.

Variable Temperature Blackbodies via Variable Conductance: Thermal Design, Modelling and Testing

NASA Astrophysics Data System (ADS)

Melzack, N.; Jones, E.; Peters, D. M.; Hurley, J. G.; Watkins, R. E. J.; Fok, S.; Sawyer, C.; Marchetaux, G.; Acreman, A.; Winkler, R.; Lowe, D.; Theocharous, T.; Montag, V.; Gibbs, D.; Pearce, A. B.; Bishop, G.; Newman, E.; Keen, S.; Stokes, J.; Pearce, A.; Stamper, R.; Cantell-Hynes, A.

2017-02-01

This paper presents the overall design for large (˜ 400 mm aperture) reference blackbody cavities currently under development at the Science and Technology Facilities Council Rutherford Appleton Laboratory Space Department (STFC RAL Space), in collaboration with the National Physical Laboratory (NPL). These blackbodies are designed to operate in vacuum over a temperature range from 160 K to 370 K, with an additional capability to operate at ˜ 100 K as a point of near-zero radiance. This is a challenging problem for a single blackbody. The novel thermal design presented in this paper enables one target that can physically achieve and operate successfully at both thermal extremes, whilst also meeting stringent temperature gradient requirements. The overall blackbody design is based upon a helium gas-gap heat switch and modified to allow for variable thermal conductance. The blackbody design consists of three main concentric cylinder components—an inner cavity (aluminium alloy), a radiation shield (aluminium) and an outer liquid nitrogen (LN2) jacket (stainless steel). The internal surface of the cavity is the effective radiating surface. There is a helium gas interspace surrounding the radiation shield and enclosed by the LN2 jacket and the inner cavity. The blackbodies are now at a mature stage of development. In this paper, the overall design, focusing upon the thermal design solution, is detailed. This paper will also concern the full-scale prototype breadboard model, for which results on thermal stability, spatial gradients and other sensitivities will be presented.

Two carrier temperatures non-equilibrium generalized Planck law for semiconductors

NASA Astrophysics Data System (ADS)

Gibelli, François; Lombez, Laurent; Guillemoles, Jean-François

2016-10-01

Planck's law of radiation describes the light emitted by a blackbody. This law has been generalized in the past for the case of a non-blackbody material having a quasi Fermi-level splitting: the lattice of the material and the carriers are then considered in an isothermal regime. Hot carrier spectroscopy deals with carriers out of the isothermal regime, as their respective temperatures (THe ≠ THh) are considered to be different than that of the lattice (TL). Here we show that Fermi-Dirac distribution temperature for each type of carrier still determine an effective radiation temperature: an explicit relationship is given involving the effective masses. Moreover, we show how to determine, in principle with an additional approximation, the carrier temperatures (THe, THh) and the corresponding absolute electrochemical potentials from photoluminescence measurements.

Temporal intensity interferometry for characterization of very narrow spectral lines

NASA Astrophysics Data System (ADS)

Tan, P. K.; Kurtsiefer, C.

2017-08-01

Some stellar objects exhibit very narrow spectral lines in the visible range additional to their blackbody radiation. Natural lasing has been suggested as a mechanism to explain narrow lines in Wolf-Rayet stars. However, the spectral resolution of conventional astronomical spectrographs is still about two orders of magnitude too low to test this hypothesis. We want to resolve the linewidth of narrow spectral emissions in starlight. A combination of spectral filtering with single-photon-level temporal correlation measurements breaks the resolution limit of wavelength-dispersing spectrographs by moving the linewidth measurement into the time domain. We demonstrate in a laboratory experiment that temporal intensity interferometry can determine a 20-MHz-wide linewidth of Doppler-broadened laser light and identify a coherent laser light contribution in a blackbody radiation background.

Protection layers on a superconducting microwave resonator toward a hybrid quantum system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jongmin, E-mail: jongmin.lee@sandia.gov; Sandia National Laboratories, Albuquerque, New Mexico 87123; Park, Dong Hun, E-mail: leomac@umd.edu

2015-10-07

We propose a protection scheme of a superconducting microwave resonator to realize a hybrid quantum system, where cold neutral atoms are coupled with a single microwave photon through magnetic dipole interaction at an interface inductor. The evanescent field atom trap, such as a waveguide/nanofiber atom trap, brings both surface-scattered photons and absorption-induced broadband blackbody radiation which result in quasiparticles and a low quality factor at the resonator. A proposed multiband protection layer consists of pairs of two dielectric layers and a thin nanogrid conductive dielectric layer above the interface inductor. We show numerical simulations of quality factors and reflection/absorption spectra,more » indicating that the proposed multilayer structure can protect a lumped-element microwave resonator from optical photons and blackbody radiation while maintaining a reasonably high quality factor.« less

Single-fiber multi-color pyrometry

DOEpatents

Small, IV, Ward; Celliers, Peter

2000-01-01

This invention is a fiber-based multi-color pyrometry set-up for real-time non-contact temperature and emissivity measurement. The system includes a single optical fiber to collect radiation emitted by a target, a reflective rotating chopper to split the collected radiation into two or more paths while modulating the radiation for lock-in amplification (i.e., phase-sensitive detection), at least two detectors possibly of different spectral bandwidths with or without filters to limit the wavelength regions detected and optics to direct and focus the radiation onto the sensitive areas of the detectors. A computer algorithm is used to calculate the true temperature and emissivity of a target based on blackbody calibrations. The system components are enclosed in a light-tight housing, with provision for the fiber to extend outside to collect the radiation. Radiation emitted by the target is transmitted through the fiber to the reflective chopper, which either allows the radiation to pass straight through or reflects the radiation into one or more separate paths. Each path includes a detector with or without filters and corresponding optics to direct and focus the radiation onto the active area of the detector. The signals are recovered using lock-in amplification. Calibration formulas for the signals obtained using a blackbody of known temperature are used to compute the true temperature and emissivity of the target. The temperature range of the pyrometer system is determined by the spectral characteristics of the optical components.

Just How Bright Is a Laser?

ERIC Educational Resources Information Center

Van Baak, David A.

1995-01-01

Attempts to quantify the subjective sensation of brightness of the spot projected by a helium-neon laser and compares this with conventional sources of light. Provides an exercise in using the blackbody radiation formulas. (JRH)

Using stellar spectra to illustrate thermal radiation laws

NASA Astrophysics Data System (ADS)

Kaltcheva, N. T.; Pritzl, B. J.

2018-05-01

Stars are point-source emitters that are the closest to the definition of a blackbody in comparison to all other similar sources of radiation found in nature. Existing libraries on stellar spectra are thus a valuable resource that can be used to introduce the laws of thermal radiation in a classroom setting. In this article we briefly describe some of the opportunities that available databases on stellar spectra provide for students to gain a deeper understanding on thermal radiation and spectral line characteristics.

Fabrication of a Cryogenic Terahertz Emitter for Bolometer Focal Plane Calibrations

NASA Technical Reports Server (NTRS)

Chervenak, James; Brown, Ari; Wollack, Edward

2012-01-01

A fabrication process is reported for prototype emitters of THz radiation, which operate cryogenically, and should provide a fast, stable blackbody source suitable for characterization of THz devices. The fabrication has been demonstrated and, at the time of this reporting, testing was underway. The emitter is similar to a monolithic silicon bolometer in design, using both a low-noise thermometer and a heater element on a thermally isolated stage. An impedance-matched, high-emissivity coat ing is also integrated to tune the blackbody properties. This emitter is designed to emit a precise amount of power as a blackbody spectrum centered on terahertz frequencies. The emission is a function of the blackbody temperature. An integrated resistive heater and thermometer system can control the temperature of the blackbody with greater precision than previous incarnations of calibration sources that relied on blackbody emission. The emitter is fabricated using a silicon- on-insulator substrate wafer. The buried oxide is chosen to be less than 1 micron thick, and the silicon device thickness is 1-2 microns. Layers of phosphorus compensated with boron are implanted into and diffused throughout the full thickness of the silicon device layer to create the thermometer and heater components. Degenerately doped wiring is implanted to connect the devices to wire-bondable contact pads at the edge of the emitter chip. Then the device is micromachined to remove the thick-handle silicon behind the thermometer and heater components, and to thermally isolate it on a silicon membrane. An impedance- matched emissive coating (ion assisted evaporated Bi) is applied to the back of the membrane to enable high-efficiency emission of the blackbody spectrum.

Coherence properties of blackbody radiation and application to energy harvesting and imaging with nanoscale rectennas

NASA Astrophysics Data System (ADS)

Lerner, Peter B.; Cutler, Paul H.; Miskovsky, Nicholas M.

2015-01-01

Modern technology allows the fabrication of antennas with a characteristic size comparable to the electromagnetic wavelength in the optical region. This has led to the development of new technologies using nanoscale rectifying antennas (rectennas) for solar energy conversion and sensing of terahertz, infrared, and visible radiation. For example, a rectenna array can collect incident radiation from an emitting source and the resulting conversion efficiency and operating characteristics of the device will depend on the spatial and temporal coherence properties of the absorbed radiation. For solar radiation, the intercepted radiation by a micro- or nanoscale array of devices has a relatively narrow spatial and angular distribution. Using the Van Cittert-Zernike theorem, we show that the coherence length (or radius) of solar radiation on an antenna array is, or can be, tens of times larger than the characteristic wavelength of the solar spectrum, i.e., the thermal wavelength, λT=2πℏc/(kBT), which for T=5000 K is about 3 μm. Such an effect is advantageous, making possible the rectification of solar radiation with nanoscale rectenna arrays, whose size is commensurate with the coherence length. Furthermore, we examine the blackbody radiation emitted from an array of antennas at temperature T, which can be quasicoherent and lead to a modified self-image, analogous to the Talbot-Lau self-imaging process but with thermal rather than monochromatic radiation. The self-emitted thermal radiation may be important as a nondestructive means for quality control of the array.

High temperature spectral emissivity measurement using integral blackbody method

NASA Astrophysics Data System (ADS)

Pan, Yijie; Dong, Wei; Lin, Hong; Yuan, Zundong; Bloembergen, Pieter

2016-10-01

Spectral emissivity is a critical material's thermos-physical property for heat design and radiation thermometry. A prototype instrument based upon an integral blackbody method was developed to measure material's spectral emissivity above 1000 °. The system was implemented with an optimized commercial variable-high-temperature blackbody, a high speed linear actuator, a linear pyrometer, and an in-house designed synchronization circuit. A sample was placed in a crucible at the bottom of the blackbody furnace, by which the sample and the tube formed a simulated blackbody which had an effective total emissivity greater than 0.985. During the measurement, the sample was pushed to the end opening of the tube by a graphite rod which was actuated through a pneumatic cylinder. A linear pyrometer was used to monitor the brightness temperature of the sample surface through the measurement. The corresponding opto-converted voltage signal was fed and recorded by a digital multi-meter. A physical model was proposed to numerically evaluate the temperature drop along the process. Tube was discretized as several isothermal cylindrical rings, and the temperature profile of the tube was measurement. View factors between sample and rings were calculated and updated along the whole pushing process. The actual surface temperature of the sample at the end opening was obtained. Taking advantages of the above measured voltage profile and the calculated true temperature, spectral emissivity under this temperature point was calculated.

Calibration of High Heat Flux Sensors at NIST

PubMed Central

Murthy, A. V.; Tsai, B. K.; Gibson, C. E.

1997-01-01

An ongoing program at the National Institute of Standards and Technology (NIST) is aimed at improving and standardizing heat-flux sensor calibration methods. The current calibration needs of U.S. science and industry exceed the current NIST capability of 40 kW/m2 irradiance. In achieving this goal, as well as meeting lower-level non-radiative heat flux calibration needs of science and industry, three different types of calibration facilities currently are under development at NIST: convection, conduction, and radiation. This paper describes the research activities associated with the NIST Radiation Calibration Facility. Two different techniques, transfer and absolute, are presented. The transfer calibration technique employs a transfer standard calibrated with reference to a radiometric standard for calibrating the sensors using a graphite tube blackbody. Plans for an absolute calibration facility include the use of a spherical blackbody and a cooled aperture and sensor-housing assembly to calibrate the sensors in a low convective environment. PMID:27805156

Localizing high-lying Rydberg wave packets with two-color laser fields

NASA Astrophysics Data System (ADS)

Larimian, Seyedreza; Lemell, Christoph; Stummer, Vinzenz; Geng, Ji-Wei; Roither, Stefan; Kartashov, Daniil; Zhang, Li; Wang, Mu-Xue; Gong, Qihuang; Peng, Liang-You; Yoshida, Shuhei; Burgdörfer, Joachim; Baltuška, Andrius; Kitzler, Markus; Xie, Xinhua

2017-08-01

We demonstrate control over the localization of high-lying Rydberg wave packets in argon atoms with phase-locked orthogonally polarized two-color laser fields. With a reaction microscope, we measure ionization signals of high-lying Rydberg states induced by a weak dc field and blackbody radiation as a function of the relative phase between the two-color fields. We find that the dc-field-ionization yield of high-lying Rydberg argon atoms oscillates with the relative two-color phase with a period of 2 π while the photoionization signal by blackbody radiation shows a period of π . Accompanying simulations show that these observations are a clear signature of the asymmetric localization of electrons recaptured into very elongated (low angular momentum) high-lying Rydberg states after conclusion of the laser pulse. Our findings thus open an effective pathway to control the localization of high-lying Rydberg wave packets.

A short history of nomograms and tables used for thermal radiation calculations

NASA Astrophysics Data System (ADS)

Stewart, Seán. M.; Johnson, R. Barry

2016-09-01

The theoretical concept of a perfect thermal radiator, the blackbody, was first introduced by the German physicist Gustav Robert Kirchhoff in 1860. By the latter half of the nineteenth century it had become the object of intense theoretical and experimental investigation. While an attempt at trying to theoretically understand the behavior of radiation emitted from a blackbody was undertaken by many eminent physicists of the day, its solution was not found until 1900 when Max Planck put forward his now famous law for thermal radiation. Today, of course, understanding blackbody behavior is vitally important to many fields including infrared systems, illumination, pyrometry, spectroscopy, astronomy, thermal engineering, cryogenics, and meteorology. Mathematically, the form Planck's law takes is rather cumbersome meaning calculations made with it before the advent of modern computers were rather tedious, dramatically slowing the process of computation. Fortunately, during those early days of the twentieth century researchers quickly realized Planck's equation, and the various functions closely related to it, readily lend themselves to being given a graphical, mechanical, or numerically tabulated form for their evaluation. The first of these computational aids to appear were tables. These arose shortly after Planck introduced his equation, were produced in the greatest number, and remained unsurpassed in their level of accuracy compared to all other aids made. It was also not long before nomograms designed to aid thermal radiation calculations appeared. Essentially a printed chart and requiring nothing more than a straightedge to use, nomograms were cheap and extremely easy to use. Facilitating instant answers to a range of quantities relating to thermal radiation, a number were produced and the inventiveness displayed in some was quite remarkable. In this paper we consider the historical development of many of the nomograms and tables developed and used by generations of scientists and engineers before their sudden and irrevocable decline shortly after the arrival of affordable digital computers and hand-held electronic calculators during the mid-1970s. This work represents a continuation of our earlier work on a number of radiation slide rules developed and used for thermal radiation calculations, with all three of these computational aids being the subject of a forthcoming book.

Radiation calibration for LWIR Hyperspectral Imager Spectrometer

NASA Astrophysics Data System (ADS)

Yang, Zhixiong; Yu, Chunchao; Zheng, Wei-jian; Lei, Zhenggang; Yan, Min; Yuan, Xiaochun; Zhang, Peizhong

2014-11-01

The radiometric calibration of LWIR Hyperspectral imager Spectrometer is presented. The lab has been developed to LWIR Interferometric Hyperspectral imager Spectrometer Prototype(CHIPED-I) to study Lab Radiation Calibration, Two-point linear calibration is carried out for the spectrometer by using blackbody respectively. Firstly, calibration measured relative intensity is converted to the absolute radiation lightness of the object. Then, radiation lightness of the object is is converted the brightness temperature spectrum by the method of brightness temperature. The result indicated †that this method of Radiation Calibration calibration was very good.

Fresnel Lens Solar Concentrator Design Based on Geometric Optics and Blackbody Radiation Equations

NASA Technical Reports Server (NTRS)

Watson, Michael D.; Jayroe, Robert

1998-01-01

Fresnel lenses have been used for years as solar concentrators in a variety of applications. Several variables effect the final design of these lenses including: lens diameter, image spot distance from the lens, and bandwidth focused in the image spot. Defining the image spot as the geometrical optics circle of least confusion, a set of design equations has been derived to define the groove angles for each groove on the lens. These equations allow the distribution of light by wavelength within the image spot to be calculated. Combining these equations with the blackbody radiation equations, energy distribution, power, and flux within the image spot can be calculated. In addition, equations have been derived to design a lens to produce maximum flux in a given spot size. Using these equations, a lens may be designed to optimize the spot energy concentration for given energy source.

Scientific results from COBE

NASA Technical Reports Server (NTRS)

Bennett, C. L.; Boggess, N. W.; Cheng, E. S.; Hauser, M. G.; Kelsall, T.; Mather, J. C.; Moseley, S. H., Jr.; Murdock, T. L.; Shafer, R. A.; Silverberg, R. F.

1993-01-01

NASA's Cosmic Background Explorer (COBE) carries three scientific instruments to make precise measurements of the spectrum and anisotropy of the cosmic microwave background (CMB) radiation on angular scales greater than 7 deg and to conduct a search for a diffuse cosmic infrared background (CIB) radiation with 0.7 deg angular resolution. Data from the Far-Infrared Absolute Spectrophotometer (FIRAS) show that the spectrum of the CMB is that of a blackbody of temperature T = 2.73 +/- 0.06 K, with no deviation from a blackbody spectrum greater than 0.25% of the peak brightness. The first year of data from the Differential Microwave Radiometers (DMR) show statistically significant CMB anisotropy. The anisotropy is consistent with a scale invariant primordial density fluctuation spectrum. Infrared sky brightness measurements from the Diffuse Infrared Background Experiment (DIRBE) provide new conservative upper limits to the CIB. Extensive modeling of solar system and galactic infrared foregrounds is required for further improvement in the CIB limits.

Radiation thermometry at NIST: An update of services and research activities

NASA Technical Reports Server (NTRS)

Hillard, G. Barry

1989-01-01

An overview of activities at the National Institute of Standards and Terminology (NIST) in radiation thermometry and related temperature scale research is presented. An expansion of calibration services for pyrometers will be described as well as efforts to develop calibration services for blackbody simulators. Research relevant to the realization of the new international temperature scale (ITS 90) will be discussed.

A spatially resolved pyrometer for measuring the blackbody temperature of a warm dense plasma

DOE PAGES

Coleman, Joshua Eugene

2016-12-30

A pyrometer has been developed to spatially resolve the blackbody temperature of a radiatively cooling warm dense plasma. The pyrometer is composed of a lens coupled fiber array, Czerny-Turner visible spectrometer, and an intensified gated CCD for the detector. The radiatively cooling warm dense plasma is generated by a ~100-ns-long intense relativistic electron bunch with an energy of 19.1 MeV and a current of 0.2 kA interacting with 100-μm-thick low-Z foils. The continuum spectrum is measured over 250 nm with a low groove density grating. These plasmas emit visible light or blackbody radiation on relatively long time scales (~0.1 tomore » 100 μs). Finally, we presented the diagnostic layout, calibration, and proof-of-principle measurement of a radiatively cooling aluminum plasma, which includes a spatially resolved temperature gradient and the ability to temporally resolve it also.« less

Infrared Surface Temperature Measurements in the Presence of Reflected Radiation

DTIC Science & Technology

1990-08-01

33 11. Photograph of l-in. Blackbody Radiator .................................. 34 12. Radiosity (B...amount of radiation reaching the detector will be proportional to the radiosity (B) of the target, and will be a function of the optical path, target...emissivity, and geometry of the instrument. The radiosity is the rate at which energy streams away from the target surface and is the sum of the

Plasma channel optical pumping device and method

DOEpatents

Judd, O.P.

1983-06-28

A device and method are disclosed for optically pumping a gaseous laser using blackbody radiation produced by a plasma channel which is formed from an electrical discharge between two electrodes spaced at opposite longitudinal ends of the laser. A preionization device which can comprise a laser or electron beam accelerator produces a preionization beam which is sufficient to cause an electrical discharge between the electrodes to initiate the plasma channel along the preionization path. The optical pumping energy is supplied by a high voltage power supply rather than by the preionization beam. High output optical intensities are produced by the laser due to the high temperature blackbody radiation produced by the plasma channel, in the same manner as an exploding wire type laser. However, unlike the exploding wire type laser, the disclosed invention can be operated in a repetitive manner by utilizing a repetitive pulsed preionization device. 5 figs.

Broadband infrared vibrational nano-spectroscopy using thermal blackbody radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Callahan, Brian T.; Lewis, William E.; Möbius, Silke

Infrared vibrational nano-spectroscopy based on scattering scanning near-field optical microscopy (s-SNOM) provides intrinsic chemical specificity with nanometer spatial resolution. Here we use incoherent infrared radiation from a 1400 K thermal blackbody emitter for broadband infrared (IR) nano-spectroscopy.With optimized interferometric heterodyne signal amplification we achieve few-monolayer sensitivity in phonon polariton spectroscopy and attomolar molecular vibrational spectroscopy. Near-field localization and nanoscale spatial resolution is demonstrated in imaging flakes of hexagonal boron nitride (hBN) and determination of its phonon polariton dispersion relation. The signal-to-noise ratio calculations and analysis for different samples and illumination sources provide a reference for irradiance requirements and the attainablemore » near-field signal levels in s-SNOM in general. As a result, the use of a thermal emitter as an IR source thus opens s-SNOM for routine chemical FTIR nano-spectroscopy.« less

Broadband infrared vibrational nano-spectroscopy using thermal blackbody radiation

DOE PAGES

O’Callahan, Brian T.; Lewis, William E.; Möbius, Silke; ...

2015-12-03

Infrared vibrational nano-spectroscopy based on scattering scanning near-field optical microscopy (s-SNOM) provides intrinsic chemical specificity with nanometer spatial resolution. Here we use incoherent infrared radiation from a 1400 K thermal blackbody emitter for broadband infrared (IR) nano-spectroscopy.With optimized interferometric heterodyne signal amplification we achieve few-monolayer sensitivity in phonon polariton spectroscopy and attomolar molecular vibrational spectroscopy. Near-field localization and nanoscale spatial resolution is demonstrated in imaging flakes of hexagonal boron nitride (hBN) and determination of its phonon polariton dispersion relation. The signal-to-noise ratio calculations and analysis for different samples and illumination sources provide a reference for irradiance requirements and the attainablemore » near-field signal levels in s-SNOM in general. As a result, the use of a thermal emitter as an IR source thus opens s-SNOM for routine chemical FTIR nano-spectroscopy.« less

Radiative characteristics of the Chelyabinsk superbolide

NASA Astrophysics Data System (ADS)

Yanagisawa, Masahisa

2015-12-01

On Feb. 15, 2013, a meteoroid with a size of about 19 m plunged into the terrestrial atmosphere at 19 km s-1 and burst at an altitude of about 30 km over the city of Chelyabinsk, Russia. Here we present light curves for the bolide in the red, green, and blue color bands, derived from an analysis of a video that was recorded by a dashboard camera and released on the Internet. Our results demonstrate that the bolide was blue-green in color, which is inconsistent with the Planck spectrum before the meteoroid began to fragment. Fragmentation triggered a flare-up of the bolide and 90% of its radiation energy at optical wavelengths was released within a period of about 2 s after that. During the same period, the brightness ratios among the three bands became consistent with 4000 K blackbody radiation. Based on the peak luminosity, a surface area of several square kilometers would be required for a 4000 K blackbody. It is considered that the radiation source of the bolide was an elongated cloud of vapor and debris produced through severe fragmentation of the meteoroid.

Relativistic Transformations of Light Power.

ERIC Educational Resources Information Center

McKinley, John M.

1979-01-01

Using a photon-counting technique, finds the angular distribution of emitted and detected power and the total radiated power of an arbitrary moving source, and uses the technique to verify the predicted effect of the earth's motion through the cosmic blackbody radiation. (Author/GA)

Radiative and convective properties of 316L Stainless Steel fabricated using the Laser Engineered Net Shaping process

NASA Astrophysics Data System (ADS)

Knopp, Jonathan

Temperature evolution of metallic materials during the additive manufacturing process has direct influence in determining the materials microstructure and resultant characteristics. Through the power of Infrared (IR) thermography it is now possible to monitor thermal trends in a build structure, giving the power to adjust building parameters in real time. The IR camera views radiation in the IR wavelengths and determines temperature of an object by the amount of radiation emitted from the object in those wavelengths. Determining the amount of radiation emitted from the material, known as a materials emissivity, can be difficult in that emissivity is affected by both temperature and surface finish. It has been shown that the use of a micro-blackbody cavity can be used as an accurate reference temperature when the sample is held at thermal equilibrium. A micro-blackbody cavity was created in a sample of 316L Stainless Steel after being fabricated during using the Laser Engineered Net Shaping (LENS) process. Holding the sample at thermal equilibrium and using the micro-blackbody cavity as a reference and thermocouple as a second reference emissivity values were able to be obtained. IR thermography was also used to observe the manufacturing of these samples. When observing the IR thermography, patterns in the thermal history of the build were shown to be present as well as distinct cooling rates of the material. This information can be used to find true temperatures of 316L Stainless Steel during the LENS process for better control of desired material properties as well as future work in determining complete energy balance.

Activities of NIST (National Inst. of Standards and Technology)

NASA Technical Reports Server (NTRS)

1992-01-01

The Radiometric Physics Division of the NIST is responsible for the national standards in radiation thermometry, spectroradiometry, photometry, and spectrophotometry; dissemination of these standards by providing measurement services to customers requiring calibrations of the highest accuracy; and conducting fundamental and applied research to develop the scientific basis for future measurement services. Its relevance to EOS/TIR calibration includes calibrating unknown blackbody for radiance using a well-characterized NIST blackbody source by matching the radiant fluxes with an IR radiometer. The TIR Round Robin is used to verify the calibration of the sources that are used for the absolute radiometric calibration of the individual EOS sensors.

Total spectral distributions from Hawking radiation

NASA Astrophysics Data System (ADS)

Broda, Bogusław

2017-11-01

Taking into account the time dependence of the Hawking temperature and finite evaporation time of the black hole, the total spectral distributions of the radiant energy and of the number of particles have been explicitly calculated and compared to their temporary (initial) blackbody counterparts (spectral exitances).

Calibration of Radiation Thermometers up to : Effective Emissivity of the Source

NASA Astrophysics Data System (ADS)

Kozlova, O.; Briaudeau, S.; Rongione, L.; Bourson, F.; Guimier, S.; Kosmalski, S.; Sadli, M.

2015-08-01

The growing demand of industry for traceable temperature measurements up to encourages improvement of calibration techniques for industrial-type radiation thermometers in this temperature range. High-temperature fixed points can be used at such high temperatures, but due to the small diameter of apertures of their cavities (3 mm), they are not adapted for the large field-of-views commonly featured by this kind of radiation thermometers. At LNE-Cnam, a Thermo Gauge furnace of 25.4 mm source aperture diameter is used as a comparison source to calibrate customers' instruments against a reference radiation thermometer calibrated according to the ITS-90 with the lowest uncertainties achievable in the Laboratory. But the furnace blackbody radiator exhibits a large temperature gradient that degrades its effective emissivity, and increases the calibration uncertainty due to the lack of information on the working spectral band of the industrial radiation thermometer. In order to estimate the corrections to apply, the temperature distribution (radial and on-axis) of the Thermo Gauge furnace blackbody radiator was characterized and the effective emissivity of the Thermo Gauge cavity was determined by three different methods. Because of this investigation, the corrections due to different fields of view and due to the different spectral bands of the reference pyrometer and the customer's pyrometer were obtained and the uncertainties on these corrections were evaluated.

Cryogenic Blackbody-Radiation Calibration Source

NASA Technical Reports Server (NTRS)

Burkett, Cecil G., Jr.; Daryabeigi, Kamran

1993-01-01

Operating temperatures range from ambient down to minus 100 degrees C. V-grooved front face of source body blackened and recessed in black sleeve. Semiairtight chamber that houses source purged with dry nitrogen gas to prevent formation of dew or frost at low operating temperature.

Response of a piezoelectric pressure transducer to IR laser beam impingement

NASA Technical Reports Server (NTRS)

Smith, William C.; Leiweke, Robert J.; Beeson, Harold

1992-01-01

The non-pressure response of a PCB Model 113A transducer to a far infrared radiation impulse from a carbon dioxide laser was investigated. Incident radiation was applied both to the bare transducer diaphragm and to coated diaphragms. Coatings included two common ablative materials and a reflective gold coating. High-flux radiation impulses induced an immediate brief negative output followed by a longer-duration positive output. Both timing and amplitude of the responses will be discussed, and the effects of coatings will be compared. Bursts of blackbody radiation from a 1500 K source produced qualitatively similar responses.

Relationship between Hawking radiation and gravitational anomalies.

PubMed

Robinson, Sean P; Wilczek, Frank

2005-07-01

We show that in order to avoid a breakdown of general covariance at the quantum level the total flux in each outgoing partial wave of a quantum field in a black hole background must be equal to that of a (1+1)-dimensional blackbody at the Hawking temperature.

Dual-Mode Operation of an Optical Lattice Clock Using Strontium and Ytterbium Atoms.

PubMed

Akamatsu, Daisuke; Kobayashi, Takumi; Hisai, Yusuke; Tanabe, Takehiko; Hosaka, Kazumoto; Yasuda, Masami; Hong, Feng-Lei

2018-06-01

We have developed an optical lattice clock that can operate in dual modes: a strontium (Sr) clock mode and an ytterbium (Yb) clock mode. Dual-mode operation of the Sr-Yb optical lattice clock is achieved by alternately cooling and trapping 87 Sr and 171 Yb atoms inside the vacuum chamber of the clock. Optical lattices for Sr and Yb atoms were arranged with horizontal and vertical configurations, respectively, resulting in a small distance of the order of between the trapped Sr and Yb atoms. The 1 S 0 - 3 P 0 clock transitions in the trapped atoms were interrogated in turn and the clock lasers were stabilized to the transitions. We demonstrated the frequency ratio measurement of the Sr and Yb clock transitions by using the dual-mode operation of the Sr-Yb optical lattice clock. The dual-mode operation can reduce the uncertainty of the blackbody radiation shift in the frequency ratio measurement, because both Sr and Yb atoms share the same blackbody radiation.

The Kelvin and Temperature Measurements

PubMed Central

Mangum, B. W.; Furukawa, G. T.; Kreider, K. G.; Meyer, C. W.; Ripple, D. C.; Strouse, G. F.; Tew, W. L.; Moldover, M. R.; Johnson, B. Carol; Yoon, H. W.; Gibson, C. E.; Saunders, R. D.

2001-01-01

The International Temperature Scale of 1990 (ITS-90) is defined from 0.65 K upwards to the highest temperature measurable by spectral radiation thermometry, the radiation thermometry being based on the Planck radiation law. When it was developed, the ITS-90 represented thermodynamic temperatures as closely as possible. Part I of this paper describes the realization of contact thermometry up to 1234.93 K, the temperature range in which the ITS-90 is defined in terms of calibration of thermometers at 15 fixed points and vapor pressure/temperature relations which are phase equilibrium states of pure substances. The realization is accomplished by using fixed-point devices, containing samples of the highest available purity, and suitable temperature-controlled environments. All components are constructed to achieve the defining equilibrium states of the samples for the calibration of thermometers. The high quality of the temperature realization and measurements is well documented. Various research efforts are described, including research to improve the uncertainty in thermodynamic temperatures by measuring the velocity of sound in gas up to 800 K, research in applying noise thermometry techniques, and research on thermocouples. Thermometer calibration services and high-purity samples and devices suitable for “on-site” thermometer calibration that are available to the thermometry community are described. Part II of the paper describes the realization of temperature above 1234.93 K for which the ITS-90 is defined in terms of the calibration of spectroradiometers using reference blackbody sources that are at the temperature of the equilibrium liquid-solid phase transition of pure silver, gold, or copper. The realization of temperature from absolute spectral or total radiometry over the temperature range from about 60 K to 3000 K is also described. The dissemination of the temperature scale using radiation thermometry from NIST to the customer is achieved by calibration of blackbody sources, tungsten-strip lamps, and pyrometers. As an example of the research efforts in absolute radiometry, which impacts the NIST spectral irradiance and radiance scales, results with filter radiometers and a high-temperature blackbody are summarized. PMID:27500019

Regularized minimum I-divergence methods for the inverse blackbody radiation problem

NASA Astrophysics Data System (ADS)

Choi, Kerkil; Lanterman, Aaron D.; Shin, Jaemin

2006-08-01

This paper proposes iterative methods for estimating the area temperature distribution of a blackbody from its total radiated power spectrum measurements. This is called the inverse blackbody radiation problem. This problem is inherently ill-posed due to the characteristics of the kernel in the underlying integral equation given by Planck's law. The functions involved in the problem are all non-negative. Csiszár's I-divergence is an information-theoretic discrepancy measure between two non-negative functions. We derive iterative methods for minimizing Csiszár's I-divergence between the measured power spectrum and the power spectrum arising from the estimate according to the integral equation. Due to the ill-posedness of the problem, unconstrained algorithms often produce poor estimates, especially when the measurements are corrupted by noise. To alleviate this difficulty, we apply regularization methods to our algorithms. Penalties based on Shannon's entropy, the L1-norm and Good's roughness are chosen to suppress the undesirable artefacts. When a penalty is applied, the pertinent optimization that needs to be performed at each iteration is no longer trivial. In particular, Good's roughness causes couplings between estimate components. To handle this issue, we adapt Green's one-step-late method. This choice is based on the important fact that our minimum I-divergence algorithms can be interpreted as asymptotic forms of certain expectation-maximization algorithms. The effectiveness of our methods is illustrated via various numerical experiments.

Entropy/information flux in Hawking radiation

NASA Astrophysics Data System (ADS)

Alonso-Serrano, Ana; Visser, Matt

2018-01-01

Blackbody radiation contains (on average) an entropy of 3.9 ± 2.5 bits per photon. If the emission process is unitary, then this entropy is exactly compensated by "hidden information" in the correlations. We extend this argument to the Hawking radiation from GR black holes, demonstrating that the assumption of unitarity leads to a perfectly reasonable entropy/information budget. The key technical aspect of our calculation is a variant of the "average subsystem" approach developed by Page, which we extend beyond bipartite pure systems, to a tripartite pure system that considers the influence of the environment.

Thermodynamic Temperature of High-Temperature Fixed Points Traceable to Blackbody Radiation and Synchrotron Radiation

NASA Astrophysics Data System (ADS)

Wähmer, M.; Anhalt, K.; Hollandt, J.; Klein, R.; Taubert, R. D.; Thornagel, R.; Ulm, G.; Gavrilov, V.; Grigoryeva, I.; Khlevnoy, B.; Sapritsky, V.

2017-10-01

Absolute spectral radiometry is currently the only established primary thermometric method for the temperature range above 1300 K. Up to now, the ongoing improvements of high-temperature fixed points and their formal implementation into an improved temperature scale with the mise en pratique for the definition of the kelvin, rely solely on single-wavelength absolute radiometry traceable to the cryogenic radiometer. Two alternative primary thermometric methods, yielding comparable or possibly even smaller uncertainties, have been proposed in the literature. They use ratios of irradiances to determine the thermodynamic temperature traceable to blackbody radiation and synchrotron radiation. At PTB, a project has been established in cooperation with VNIIOFI to use, for the first time, all three methods simultaneously for the determination of the phase transition temperatures of high-temperature fixed points. For this, a dedicated four-wavelengths ratio filter radiometer was developed. With all three thermometric methods performed independently and in parallel, we aim to compare the potential and practical limitations of all three methods, disclose possibly undetected systematic effects of each method and thereby confirm or improve the previous measurements traceable to the cryogenic radiometer. This will give further and independent confidence in the thermodynamic temperature determination of the high-temperature fixed point's phase transitions.

The diffuse galactic gamma radiation: The Compton contribution and component separation by energy interval and galactic coordinates

NASA Technical Reports Server (NTRS)

Kniffen, D. A.; Fichtel, C.

1981-01-01

The radiation to be expected from cosmic ray interactions with matter and photons was examined. Particular emphasis is placed on the Compton emission. Both the photon density in and near the visible region and that in the region are deduced from the estimates of the emission functions throughout the Galaxy. The blackbody radiation is also included in the estimate of the total Compton emission. The result suggests that the gamma ray Compton radiation from cosmic ray ineractions with galactic visible and infrared photons is substantially larger than previously believed.

Blackbody for metrological control of ear thermometers

NASA Astrophysics Data System (ADS)

Cárdenas-García, D.; Méndez-Lango, E.

2013-09-01

Body temperature is an important parameter in medical practice, and most of health diagnoses are made based upon measured temperature values. Non-contact measurements are attractive to both patients and physicians, and ear thermometers (ET) are part of the set of infrared thermometers for medical applications. ETs sense the tympanic membrane temperature which best represents body temperature. They take advantage of the natural high effective emissivity cavity that is formed as radiation source. To calibrate or to check the performance of ETs, we designed a high-emissivity spherical cavity as a blackbody source which can be placed in a dry block oven. Although the blackbody cavity can have any shape, we decided to build it spherical because its effective emissivity can be easily calculated in a closed form. The cavity is made of Aluminum to take advantage of its high thermal conductivity while its inner side is covered with a black paint to increase the cavity effective emissivity. Based on paint emissivity measurements and the geometrical shape, we calculated that the cavity has an effective emissivity higher than 0.999. Blackbody temperature is measured with a calibrated contact thermometer placed inside the bottom wall of the cavity. We present the design of the cavity, the experimental setup, and results of three commercial ETs compared with this cavity.

Cryogenic fountain development at NIST and INRIM: preliminary characterization.

PubMed

Levi, Filippo; Calosso, Claudio; Calonico, Davide; Lorini, Luca; Bertacco, Elio K; Godone, Aldo; Costanzo, Giovanni A; Mongino, Barbara; Jefferts, Steven R; Heavner, Thomas P; Donley, Elizabeth A

2010-03-01

This paper describes the new twin laser-cooled Cs fountain primary frequency standards NIST-F2 and ITCsF2, and presents some of their design features. Most significant is a cryogenic microwave interrogation region which dramatically reduces the blackbody radiation shift. We also present a preliminary accuracy evaluation of IT-CsF2.

Smoot Cosmology Group

Science.gov Websites

History of COBE project Structure in the COBE differential microwave radiometer first-year maps. Smoot, et (Wilkinson Microwave Anisotropy Probe) CMB satellite 5 year data papers Introduction NASA's COBE (Cosmic compare the spectrum of the cosmic microwave background radiation with that from a precise blackbody. Data

Crucial Experiments in Quantum Physics.

ERIC Educational Resources Information Center

Trigg, George L.

The six experiments included in this monography are titled Blackbody Radiation, Collision of Electrons with Atoms, The Photoelectric Effect, Magnetic Properties of Atoms, The Scattering of X-Rays, and Diffraction of Electrons by a Crystal Lattice. The discussion provides historical background by giving description of the original experiments and…

Measurement of high-temperature spectral emissivity using integral blackbody approach

NASA Astrophysics Data System (ADS)

Pan, Yijie; Dong, Wei; Lin, Hong; Yuan, Zundong; Bloembergen, Pieter

2016-11-01

Spectral emissivity is one of the most critical thermophysical properties of a material for heat design and analysis. Especially in the traditional radiation thermometry, normal spectral emissivity is very important. We developed a prototype instrument based upon an integral blackbody method to measure material's spectral emissivity at elevated temperatures. An optimized commercial variable-high-temperature blackbody, a high speed linear actuator, a linear pyrometer, and an in-house designed synchronization circuit was used to implemented the system. A sample was placed in a crucible at the bottom of the blackbody furnace, by which the sample and the tube formed a simulated reference blackbody which had an effective total emissivity greater than 0.985. During the measurement, a pneumatic cylinder pushed a graphite rode and then the sample crucible to the cold opening within hundreds of microseconds. The linear pyrometer was used to monitor the brightness temperature of the sample surface, and the corresponding opto-converted voltage was fed and recorded by a digital multimeter. To evaluate the temperature drop of the sample along the pushing process, a physical model was proposed. The tube was discretized into several isothermal cylindrical rings, and the temperature of each ring was measurement. View factors between sample and rings were utilized. Then, the actual surface temperature of the sample at the end opening was obtained. Taking advantages of the above measured voltage signal and the calculated actual temperature, normal spectral emissivity under the that temperature point was obtained. Graphite sample at 1300°C was measured to prove the validity of the method.

Principal Component Noise Filtering for NAST-I Radiometric Calibration

NASA Technical Reports Server (NTRS)

Tian, Jialin; Smith, William L., Sr.

2011-01-01

The National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed- Interferometer (NAST-I) instrument is a high-resolution scanning interferometer that measures emitted thermal radiation between 3.3 and 18 microns. The NAST-I radiometric calibration is achieved using internal blackbody calibration references at ambient and hot temperatures. In this paper, we introduce a refined calibration technique that utilizes a principal component (PC) noise filter to compensate for instrument distortions and artifacts, therefore, further improve the absolute radiometric calibration accuracy. To test the procedure and estimate the PC filter noise performance, we form dependent and independent test samples using odd and even sets of blackbody spectra. To determine the optimal number of eigenvectors, the PC filter algorithm is applied to both dependent and independent blackbody spectra with a varying number of eigenvectors. The optimal number of PCs is selected so that the total root-mean-square (RMS) error is minimized. To estimate the filter noise performance, we examine four different scenarios: apply PC filtering to both dependent and independent datasets, apply PC filtering to dependent calibration data only, apply PC filtering to independent data only, and no PC filters. The independent blackbody radiances are predicted for each case and comparisons are made. The results show significant reduction in noise in the final calibrated radiances with the implementation of the PC filtering algorithm.

Precision blackbody sources for radiometric standards.

PubMed

Sapritsky, V I; Khlevnoy, B B; Khromchenko, V B; Lisiansky, B E; Mekhontsev, S N; Melenevsky, U A; Morozova, S P; Prokhorov, A V; Samoilov, L N; Shapoval, V I; Sudarev, K A; Zelener, M F

1997-08-01

The precision blackbody sources developed at the All-Russian Institute for Optical and Physical Measurements (Moscow, Russia) and their characteristics are analyzed. The precision high-temperature graphite blackbody BB22p, large-area high-temperature pyrolytic graphite blackbody BB3200pg, middle-temperature graphite blackbody BB2000, low-temperature blackbody BB300, and gallium fixed-point blackbody BB29gl and their characteristics are described.

Clearing the Air

ERIC Educational Resources Information Center

Staehling, Erica

2015-01-01

This article describes a lesson on the greenhouse effect in which students explore blackbody radiation and Wien's law. The lesson, which has been tested in a variety of high school physics classrooms, uses probeware and online simulations and combines two well-established instructional strategies: the 5E Learning Cycle (Bybee et al. 2006) and the…

A Physically Based Algorithm for Non-Blackbody Correction of Cloud-Top Temperature and Application to Convection Study

NASA Technical Reports Server (NTRS)

Wang, Chunpeng; Lou, Zhengzhao Johnny; Chen, Xiuhong; Zeng, Xiping; Tao, Wei-Kuo; Huang, Xianglei

2014-01-01

Cloud-top temperature (CTT) is an important parameter for convective clouds and is usually different from the 11-micrometers brightness temperature due to non-blackbody effects. This paper presents an algorithm for estimating convective CTT by using simultaneous passive [Moderate Resolution Imaging Spectroradiometer (MODIS)] and active [CloudSat 1 Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)] measurements of clouds to correct for the non-blackbody effect. To do this, a weighting function of the MODIS 11-micrometers band is explicitly calculated by feeding cloud hydrometer profiles from CloudSat and CALIPSO retrievals and temperature and humidity profiles based on ECMWF analyses into a radiation transfer model.Among 16 837 tropical deep convective clouds observed by CloudSat in 2008, the averaged effective emission level (EEL) of the 11-mm channel is located at optical depth; approximately 0.72, with a standard deviation of 0.3. The distance between the EEL and cloud-top height determined by CloudSat is shown to be related to a parameter called cloud-top fuzziness (CTF), defined as the vertical separation between 230 and 10 dBZ of CloudSat radar reflectivity. On the basis of these findings a relationship is then developed between the CTF and the difference between MODIS 11-micrometers brightness temperature and physical CTT, the latter being the non-blackbody correction of CTT. Correction of the non-blackbody effect of CTT is applied to analyze convective cloud-top buoyancy. With this correction, about 70% of the convective cores observed by CloudSat in the height range of 6-10 km have positive buoyancy near cloud top, meaning clouds are still growing vertically, although their final fate cannot be determined by snapshot observations.

Frequency selective infrared optical filters for micro-bolometers

NASA Astrophysics Data System (ADS)

Creazzo, Timothy A.; Zablocki, Mathew J.; Zaman, Lenin; Sharkawy, Ahmed; Mirotznik, Mark S.; Prather, Dennis W.

2017-05-01

Current micro-bolometers are broadband detectors and tend to absorb a broad window of the IR spectrum for thermal imaging. Such systems are limited due to their lack of sensitivity to blackbody radiation, as well as the inability to spectrally discern multiple wavelengths in the field of view for hyperspectral imaging (HSI). As a result, many important applications such as low concentration chemical detection cannot be performed. One solution to this problem is to employ a system with thermoelectrically cooled or liquid nitrogen cooled sensors, which can lead to higher sensitivity in detection. However, one major drawback of these systems is the size, weight and power (SWaP) issue as they tend to be rather bulky and cumbersome, which largely challenges their use in unmanned aerial vehicles. Further, spectral filtering is commonly performed with large hardware and moving gratings, greatly increasing the SWaP of the system. To this point, Lumilant's effort is to develop wavelength selective uncooled IR filters that can be integrated onto a microbolometer, to exceed the sensitivity imposed by the blackbody radiation limit. We have demonstrated narrowband absorbers and electrically tunable filters addressing the need for low-SWaP platforms.

High-temperature-superconducting magnetic susceptibility bolometer

NASA Technical Reports Server (NTRS)

Brasunas, J.; Lakew, B.; Lee, C.

1992-01-01

An infrared detector called the magnetic susceptibility bolometer is introduced which is based on the tmperature dependence of the diamagnetic screening of a high-Tc superconductor film near Tc. Results are reported for the response of a prototype model to modulated blackbody radiation. Possible improvements are discussed as is the potential sensitivity of an improved device.

COBE looks back to the Big Bang

NASA Technical Reports Server (NTRS)

Mather, John C.

1993-01-01

An overview is presented of NASA-Goddard's Cosmic Background Explorer (COBE), the first NASA satellite designed to observe the primeval explosion of the universe. The spacecraft carries three extremely sensitive IR and microwave instruments designed to measure the faint residual radiation from the Big Bang and to search for the formation of the first galaxies. COBE's far IR absolute spectrophotometer has shown that the Big Bang radiation has a blackbody spectrum, proving that there was no large energy release after the explosion.

Search for Linear Polarization of the Cosmic Background Radiation

DOE R&D Accomplishments Database

Lubin, P. M.; Smoot, G. F.

1978-10-01

We present preliminary measurements of the linear polarization of the cosmic microwave background (3 deg K blackbody) radiation. These ground-based measurements are made at 9 mm wavelength. We find no evidence for linear polarization, and set an upper limit for a polarized component of 0.8 m deg K with a 95% confidence level. This implies that the present rate of expansion of the Universe is isotropic to one part in 10{sup 6}, assuming no re-ionization of the primordial plasma after recombination

Optically pumped carbon dioxide laser mixtures. [using solar radiation

NASA Technical Reports Server (NTRS)

Yesil, O.; Christiansen, W. H.

1979-01-01

This work explores the concept of blackbody radiation pumping of CO2 gas as a step toward utilization of solar radiation as a pumping source for laser action. To demonstrate this concept, an experiment was performed in which laser gas mixtures were exposed to 1500 K thermal radiation for brief periods of time. A gain of 2.8 x 10 to the -3rd reciprocal centimeters has been measured at 10.6 microns in a CO2-He gas mixture of 1 Torr pressure. A simple analytical model is used to describe the rate of change of energy of the vibrational modes of CO2 and to predict the gain. Agreement between the prediction and experiment is good.

Apparatus for accurately measuring high temperatures

DOEpatents

Smith, D.D.

The present invention is a thermometer used for measuring furnace temperatures in the range of about 1800/sup 0/ to 2700/sup 0/C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.

Enhancing radiative energy transfer through thermal extraction

NASA Astrophysics Data System (ADS)

Tan, Yixuan; Liu, Baoan; Shen, Sheng; Yu, Zongfu

2016-06-01

Thermal radiation plays an increasingly important role in many emerging energy technologies, such as thermophotovoltaics, passive radiative cooling and wearable cooling clothes [1]. One of the fundamental constraints in thermal radiation is the Stefan-Boltzmann law, which limits the maximum power of far-field radiation to P0 = σT4S, where σ is the Boltzmann constant, S and T are the area and the temperature of the emitter, respectively (Fig. 1a). In order to overcome this limit, it has been shown that near-field radiations could have an energy density that is orders of magnitude greater than the Stefan-Boltzmann law [2-7]. Unfortunately, such near-field radiation transfer is spatially confined and cannot carry radiative heat to the far field. Recently, a new concept of thermal extraction was proposed [8] to enhance far-field thermal emission, which, conceptually, operates on a principle similar to oil immersion lenses and light extraction in light-emitting diodes using solid immersion lens to increase light output [62].Thermal extraction allows a blackbody to radiate more energy to the far field than the apparent limit of the Stefan-Boltzmann law without breaking the second law of thermodynamics. Thermal extraction works by using a specially designed thermal extractor to convert and guide the near-field energy to the far field, as shown in Fig. 1b. The same blackbody as shown in Fig. 1a is placed closely below the thermal extractor with a spacing smaller than the thermal wavelength. The near-field coupling transfers radiative energy with a density greater than σT4. The thermal extractor, made from transparent and high-index or structured materials, does not emit or absorb any radiation. It transforms the near-field energy and sends it toward the far field. As a result, the total amount of far-field radiative heat dissipated by the same blackbody is greatly enhanced above SσT4, where S is the area of the emitter. This paper will review the progress in thermal extraction. It is organized as follows. In Section 1, we will discuss the theory of thermal extraction [8]. In Section 2, we review an experimental implementation based on natural materials as the thermal extractor [8]. Lastly, in Section 3, we review the experiment that uses structured metamaterials as thermal extractors to enhance optical density of states and far-field emission [9].

Design and Evaluation of Large-Aperture Gallium Fixed-Point Blackbody

NASA Astrophysics Data System (ADS)

Khromchenko, V. B.; Mekhontsev, S. N.; Hanssen, L. M.

2009-02-01

To complement existing water bath blackbodies that now serve as NIST primary standard sources in the temperature range from 15 °C to 75 °C, a gallium fixed-point blackbody has been recently built. The main objectives of the project included creating an extended-area radiation source with a target emissivity of 0.9999 capable of operating either inside a cryo-vacuum chamber or in a standard laboratory environment. A minimum aperture diameter of 45 mm is necessary for the calibration of radiometers with a collimated input geometry or large spot size. This article describes the design and performance evaluation of the gallium fixed-point blackbody, including the calculation and measurements of directional effective emissivity, estimates of uncertainty due to the temperature drop across the interface between the pure metal and radiating surfaces, as well as the radiometrically obtained spatial uniformity of the radiance temperature and the melting plateau stability. Another important test is the measurement of the cavity reflectance, which was achieved by using total integrated scatter measurements at a laser wavelength of 10.6 μm. The result allows one to predict the performance under the low-background conditions of a cryo-chamber. Finally, results of the spectral radiance comparison with the NIST water-bath blackbody are provided. The experimental results are in good agreement with predicted values and demonstrate the potential of our approach. It is anticipated that, after completion of the characterization, a similar source operating at the water triple point will be constructed.

The Cosmic Background Explorer

NASA Technical Reports Server (NTRS)

Gulkis, Samuel; Lubin, Philip M.; Meyer, Stephan S.; Silverberg, Robert F.

1990-01-01

The Cosmic Background Explorer (CBE), NASA's cosmological satellite which will observe a radiative relic of the big bang, is discussed. The major questions connected to the big bang theory which may be clarified using the CBE are reviewed. The satellite instruments and experiments are described, including the Differential Microwave Radiometer, which measures the difference between microwave radiation emitted from two points on the sky, the Far-Infrared Absolute Spectrophotometer, which compares the spectrum of radiation from the sky at wavelengths from 100 microns to one cm with that from an internal blackbody, and the Diffuse Infrared Background Experiment, which searches for the radiation from the earliest generation of stars.

Apparatus for accurately measuring high temperatures

DOEpatents

Smith, Douglas D.

1985-01-01

The present invention is a thermometer used for measuring furnace temperaes in the range of about 1800.degree. to 2700.degree. C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.

Equilibrium properties of blackbody radiation with an ultraviolet energy cut-off

NASA Astrophysics Data System (ADS)

Mishra, Dheeraj Kumar; Chandra, Nitin; Vaibhav, Vinay

2017-10-01

We study various equilibrium thermodynamic properties of blackbody radiation (i.e. a photon gas) with an ultraviolet energy cut-off. We find that the energy density, specific heat etc. follow usual acoustic phonon dynamics as have been well studied by Debye. Other thermodynamic quantities like pressure, entropy etc. have also been calculated. The usual Stefan-Boltzmann law gets modified. We observe that the values of the thermodynamic quantities with the energy cut-off is lower than the corresponding values in the theory without any such scale. The phase-space measure is also expected to get modified for an exotic spacetime appearing at Planck scale, which in turn leads to the modification of Planck energy density distribution and the Wien's displacement law. We found that the non-perturbative nature of the thermodynamic quantities in the SR limit (for both unmodified and modified cases), due to nonanalyticity of the leading term, is a general feature of the theory accompanied with an ultraviolet energy cut-off. We have also discussed the possible modification in the case of Big Bang and the Stellar objects and have suggested a table top experiment for verification in effective low energy case.

Laser Pyrometer For Spot Temperature Measurements

NASA Technical Reports Server (NTRS)

Elleman, D. D.; Allen, J. L.; Lee, M. C.

1988-01-01

Laser pyrometer makes temperature map by scanning measuring spot across target. Scanning laser pyrometer passively measures radiation emitted by scanned spot on target and calibrated by similar passive measurement on blackbody of known temperature. Laser beam turned on for active measurements of reflectances of target spot and reflectance standard. From measurements, temperature of target spot inferred. Pyrometer useful for non-contact measurement of temperature distributions in processing of materials.

Soft X-ray spectral fits of Geminga with model neutron star atmospheres

NASA Technical Reports Server (NTRS)

Meyer, R. D.; Pavlov, G. G.; Meszaros, P.

1994-01-01

The spectrum of the soft X-ray pulsar Geminga consists of two components, a softer one which can be interpreted as thermal-like radiation from the surface of the neutron star, and a harder one interpreted as radiation from a polar cap heated by relativistic particles. We have fitted the soft spectrum using a detailed magnetized hydrogen atmosphere model. The fitting parameters are the hydrogen column density, the effective temperature T(sub eff), the gravitational redshift z, and the distance to radius ratio, for different values of the magnetic field B. The best fits for this model are obtained when B less than or approximately 1 x 10(exp 12) G and z lies on the upper boundary of the explored range (z = 0.45). The values of T(sub eff) approximately = (2-3) x 10(exp 5) K are a factor of 2-3 times lower than the value of T(sub eff) obtained for blackbody fits with the same z. The lower T(sub eff) increases the compatibility with some proposed schemes for fast neutrino cooling of neutron stars (NSs) by the direct Urca process or by exotic matter, but conventional cooling cannot be excluded. The hydrogen atmosphere fits also imply a smaller distance to Geminga than that inferred from a blackbody fit. An accurate evaluation of the distance would require a better knowledge of the ROSAT Position Sensitive Proportional Counter (PSPC) response to the low-energy region of the incident spectrum. Our modeling of the soft component with a cooler magnetized atmosphere also implies that the hard-component fit requires a characteristic temperature which is higher (by a factor of approximately 2-3) and a surface area which is smaller (by a factor of 10(exp 3), compared to previous blackbody fits.

Biparametric complexities and generalized Planck radiation law

NASA Astrophysics Data System (ADS)

Puertas-Centeno, David; Toranzo, I. V.; Dehesa, J. S.

2017-12-01

Complexity theory embodies some of the hardest, most fundamental and most challenging open problems in modern science. The very term complexity is very elusive, so the main goal of this theory is to find meaningful quantifiers for it. In fact, we need various measures to take into account the multiple facets of this term. Here, some biparametric Crámer-Rao and Heisenberg-Rényi measures of complexity of continuous probability distributions are defined and discussed. Then, they are applied to blackbody radiation at temperature T in a d-dimensional universe. It is found that these dimensionless quantities do not depend on T nor on any physical constants. So, they have a universal character in the sense that they only depend on spatial dimensionality. To determine these complexity quantifiers, we have calculated their dispersion (typical deviations) and entropy (Rényi entropies and the generalized Fisher information) constituents. They are found to have a temperature-dependent behavior similar to the celebrated Wien’s displacement law of the dominant frequency ν_max at which the spectrum reaches its maximum. Moreover, they allow us to gain insights into new aspects of the d-dimensional blackbody spectrum and the quantification of quantum effects associated with space dimensionality.

Isotropic blackbody cosmic microwave background radiation as evidence for a homogeneous universe.

PubMed

Clifton, Timothy; Clarkson, Chris; Bull, Philip

2012-08-03

The question of whether the Universe is spatially homogeneous and isotropic on the largest scales is of fundamental importance to cosmology but has not yet been answered decisively. Surprisingly, neither an isotropic primary cosmic microwave background (CMB) nor combined observations of luminosity distances and galaxy number counts are sufficient to establish such a result. The inclusion of the Sunyaev-Zel'dovich effect in CMB observations, however, dramatically improves this situation. We show that even a solitary observer who sees an isotropic blackbody CMB can conclude that the Universe is homogeneous and isotropic in their causal past when the Sunyaev-Zel'dovich effect is present. Critically, however, the CMB must either be viewed for an extended period of time, or CMB photons that have scattered more than once must be detected. This result provides a theoretical underpinning for testing the cosmological principle with observations of the CMB alone.

Atmospheric Longwave Irradiance Uncertainty: Pyrgeometers Compared to an Absolute Sky-Scanning Radiometer, Atmospheric Emitted Radiance Interferometer, and Radiative Transfer Model Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Philipona, J. R.; Dutton, Ellsworth G.; Stoffel, T.

2001-06-04

Because atmospheric longwave radiation is one of the most fundamental elements of an expected climate change, there has been a strong interest in improving measurements and model calculations in recent years. Important questions are how reliable and consistent are atmospheric longwave radiation measurements and calculations and what are the uncertainties? The First International Pyrgeometer and Absolute Sky-scanning Radiometer Comparison, which was held at the Atmospheric Radiation Measurement program's Souther Great Plains site in Oklahoma, answers these questions at least for midlatitude summer conditions and reflects the state of the art for atmospheric longwave radiation measurements and calculations. The 15 participatingmore » pyrgeometers were all calibration-traced standard instruments chosen from a broad international community. Two new chopped pyrgeometers also took part in the comparison. And absolute sky-scanning radiometer (ASR), which includes a pyroelectric detector and a reference blackbody source, was used for the first time as a reference standard instrument to field calibrate pyrgeometers during clear-sky nighttime measurements. Owner-provided and uniformly determined blackbody calibration factors were compared. Remarkable improvements and higher pyrgeometer precision were achieved with field calibration factors. Results of nighttime and daytime pyrgeometer precision and absolute uncertainty are presented for eight consecutive days of measurements, during which period downward longwave irradiance varied between 260 and 420 W m-2. Comparisons between pyrgeometers and the absolute ASR, the atmospheric emitted radiance interferometer, and radiative transfer models LBLRTM and MODTRAN show a surprisingly good agreement of <2 W m-2 for nighttime atmospheric longwave irradiance measurements and calculations.« less

Investigation of the normal spectral band emissivity characteristic within 7.5 to 13 μm for Molybdenum between 100 and 500 °C

NASA Astrophysics Data System (ADS)

Zhang, Yan; Zhang, Yuzhong; Lu, Rongsheng; Shu, Shuangbao; Lang, Xianli; Yang, Lei

2018-01-01

Molybdenum (Mo) is an important material to construct the first wall for the Experimental Advanced Superconducting Tokamak (EAST). The real-time monitoring of temperature distribution of the first wall based on radiation thermometry is essential to guarantee the stable operation of EAST. So, it is especially important for the acquisition of emissivity property of Mo. In this work, a self-designed emissivity measurement apparatus is developed, and the relationship between the normal infrared spectral band (7.5-13 μm) emissivity of Mo against the temperature and surface roughness of material samples is experimentally investigated under the vacuum condition over the temperature ranging from 100 °C to 500 °C. Moreover, the dependence of spectral band emissivity of Mo exposed to air on the heating-duration time at a given elevated temperature is also studied. The emissivity measurement apparatus is mainly composed of a high temperature furnace and a radiation thermometer as well as a benchmark blackbody furnace. The radiation thermometer is firstly calibrated against the blackbody furnace by means of the multi-temperature methods. And then the temperature of the sample is simultaneously measured by the two highly accurate S-type thermocouples and the radiation thermometer. Finally the emissivity value of the sample is calculated based on the direct radiometric method. The developed emissivity measurement method and experimental results obtained in this work may be helpful to understand the work state the EAST and to use of Mo as an emissivity reference.

Numerical simulations of stripping effects in high-intensity hydrogen ion linacs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carneiro, J.-P.; /Fermilab; Mustapha, B.

2008-12-01

Numerical simulations of H{sup -} stripping losses from blackbody radiation, electromagnetic fields, and residual gas have been implemented into the beam dynamics code TRACK. Estimates of the stripping losses along two high-intensity H{sup -} linacs are presented: the Spallation Neutron Source linac currently being operated at Oak Ridge National Laboratory and an 8 GeV superconducting linac currently being designed at Fermi National Accelerator Laboratory.

Fluctuations in the electron system of a superconductor exposed to a photon flux

PubMed Central

de Visser, P. J.; Baselmans, J. J. A.; Bueno, J.; Llombart, N.; Klapwijk, T. M.

2014-01-01

In a superconductor, in which electrons are paired, the density of unpaired electrons should become zero when approaching zero temperature. Therefore, radiation detectors based on breaking of pairs promise supreme sensitivity, which we demonstrate using an aluminium superconducting microwave resonator. Here we show that the resonator also enables the study of the response of the electron system of the superconductor to pair-breaking photons, microwave photons and varying temperatures. A large range in radiation power (at 1.54 THz) can be chosen by carefully filtering the radiation from a blackbody source. We identify two regimes. At high radiation power, fluctuations in the electron system caused by the random arrival rate of the photons are resolved, giving a straightforward measure of the optical efficiency (48±8%) and showing an unprecedented detector sensitivity. At low radiation power, fluctuations are dominated by excess quasiparticles, the number of which is measured through their recombination lifetime. PMID:24496036

Hawking radiation from charged black holes via gauge and gravitational anomalies.

PubMed

Iso, Satoshi; Umetsu, Hiroshi; Wilczek, Frank

2006-04-21

Extending the method of Robinson and Wolczek, we show that in order to avoid a breakdown of general covariance and gauge invariance at the quantum level the total flux of charge and energy in each outgoing partial wave of a charged quantum field in a Reissner-Nordström black hole background must be equal to that of a (1 + 1)-dimensional blackbody at the Hawking temperature with the appropriate chemical potential.

Detectability of Cold Rocket Plumes.

DTIC Science & Technology

1979-10-11

blackbody temperature measurements (after Fetterman et al., Ref.9). 41 DIRECTION 118-8-1457i01 OF MAXIMUM Z RADIATION 1*I y CORERRELECOR. QU--MASRE...34 Aspen Int. Conf. on Fourier Spectroscopy, (1970), p. 19, DDC AD-724 100. 9. H. R. Fetterman , P. E. Tannenwald, B. J. Clifton, C. D. Parker, W. D...A. Blumberg, H. R. Fetterman , D. D. Peck, and P. F. Goldsmith, "Tunable Submillimeter Sources Applied to the Excited State Rotational Spectro- scopy

Uncertainty Estimates for SIRS, SKYRAD, & GNDRAD Data and Reprocessing the Pyrgeometer Data (Presentation)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reda, Ibrahim; Stoffel, Tom; Habte, Aron

2014-03-01

The National Renewable Energy Laboratory (NREL) and the Atmospheric Radiation Measurement (ARM) Climate Research Facility work together in providing data from strategically located in situ measurement observatories around the world. Both work together in improving and developing new technologies that assist in acquiring high quality radiometric data. In this presentation we summarize the uncertainty estimates of the ARM data collected at the ARM Solar Infrared Radiation Station (SIRS), Sky Radiometers on Stand for Downwelling Radiation (SKYRAD), and Ground Radiometers on Stand for Upwelling Radiation (GNDRAD), which ultimately improve the existing radiometric data. Three studies are also included to show themore » difference between calibrating pyrgeometers (e.g., Eppley PIR) using the manufacturer blackbody versus the interim World Infrared Standard Group (WISG), a pyrgeometer aging study, and the sampling rate effect of correcting historical data.« less

Fiber-optical method of pyrometric measurement of melts temperature

NASA Astrophysics Data System (ADS)

Zakharenko, V. A.; Veprikova, Ya R.

2018-01-01

There is a scientific problem of non-contact measurement of the temperature of metal melts now. The problem is related to the need to achieve the specified measurement errors in conditions of uncertainty of the blackness coefficients of the radiating surfaces. The aim of this work is to substantiate the new method of measurement in which the influence of the blackness coefficient is eliminated. The task consisted in calculating the design and material of special crucible placed in the molten metal, which is an emitter in the form of blackbody (BB). The methods are based on the classical concepts of thermal radiation and calculations based on the Planck function. To solve the problem, the geometry of the crucible was calculated on the basis of the Goofy method which forms the emitter of a blackbody at the immersed in the melt. The paper describes the pyrometric device based on fiber optic pyrometer for temperature measurement of melts, which implements the proposed method of measurement using a special crucible. The emitter is formed by the melt in this crucible, the temperature within which is measured by means of fiber optic pyrometer. Based on the results of experimental studies, the radiation coefficient ε‧ > 0.999, which confirms the theoretical and computational justification is given in the article

Sources of background light on space based laser communications links

NASA Astrophysics Data System (ADS)

Farrell, Thomas C.

2018-05-01

We discuss the sources and levels of background light that should be expected on space based laser communication (lasercom) crosslinks and uplinks, as well as on downlinks to ground stations. The analyses are valid for both Earth orbiting satellites and inter-planetary links. Fundamental equations are derived suitable for first order system engineering analyses of potential lasercom systems. These divide sources of background light into two general categories: extended sources which fill the field of view of a receiver's optics, and point sources which cannot be resolved by the optics. Specific sources of background light are discussed, and expected power levels are estimated. For uplinks, reflected sunlight and blackbody radiation from the Earth dominates. For crosslinks, depending on specific link geometry, sources of background light may include the Sun in the field of view (FOV), reflected sunlight and blackbody radiation from planets and other bodies in the solar system, individual bright stars in the FOV, the amalgam of dim stars in the FOV, zodiacal light, and reflected sunlight off of the transmitting spacecraft. For downlinks, all of these potentially come into play, and the effects of the atmosphere, including turbulence, scattering, and absorption contribute as well. Methods for accounting for each of these are presented. Specific examples are presented to illustrate the relative contributions of each source for various link geometries.

Infrared radiation scene generation of stars and planets in celestial background

NASA Astrophysics Data System (ADS)

Guo, Feng; Hong, Yaohui; Xu, Xiaojian

2014-10-01

An infrared (IR) radiation generation model of stars and planets in celestial background is proposed in this paper. Cohen's spectral template1 is modified for high spectral resolution and accuracy. Based on the improved spectral template for stars and the blackbody assumption for planets, an IR radiation model is developed which is able to generate the celestial IR background for stars and planets appearing in sensor's field of view (FOV) for specified observing date and time, location, viewpoint and spectral band over 1.2μm ~ 35μm. In the current model, the initial locations of stars are calculated based on midcourse space experiment (MSX) IR astronomical catalogue (MSX-IRAC) 2 , while the initial locations of planets are calculated using secular variations of the planetary orbits (VSOP) theory. Simulation results show that the new IR radiation model has higher resolution and accuracy than common model.

A new one-dimensional radiative equilibrium model for investigating atmospheric radiation entropy flux.

PubMed

Wu, Wei; Liu, Yangang

2010-05-12

A new one-dimensional radiative equilibrium model is built to analytically evaluate the vertical profile of the Earth's atmospheric radiation entropy flux under the assumption that atmospheric longwave radiation emission behaves as a greybody and shortwave radiation as a diluted blackbody. Results show that both the atmospheric shortwave and net longwave radiation entropy fluxes increase with altitude, and the latter is about one order in magnitude greater than the former. The vertical profile of the atmospheric net radiation entropy flux follows approximately that of the atmospheric net longwave radiation entropy flux. Sensitivity study further reveals that a 'darker' atmosphere with a larger overall atmospheric longwave optical depth exhibits a smaller net radiation entropy flux at all altitudes, suggesting an intrinsic connection between the atmospheric net radiation entropy flux and the overall atmospheric longwave optical depth. These results indicate that the overall strength of the atmospheric irreversible processes at all altitudes as determined by the corresponding atmospheric net entropy flux is closely related to the amount of greenhouse gases in the atmosphere.

The Big Bang, COBE, and the Relic Radiation of Creation (LBNL Science at the Theater)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smoot, George

Berkeley Lab's George Smoot won the 2006 Physics Nobel Prize, together with John Mather of NASA Goddard Space Flight Center, for "the discovery of the blackbody form and anisotropy of the cosmic microwave background radiation." The anisotropy showed as small variations in the map of the early universe. This research looks back into the infant universe and provides a better understanding of the origin of galaxies and stars. The cosmic background radiation is a tool to understand the structure and history of the universe and the structure of space-time. These observations have provided increased support for the big bang theorymore » of the universe's origin. The Cosmic Background Explorer (COBE) NASA satellite, launched in 1989, carries instruments that measured various aspects of cosmic microwave background radiation, and produced the data for these compelling scientific results, which opened up a field that continues very actively today.« less

Q and A with Nobelist George Smoot - 2009 BCCP Cosmology Workshop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smoot, George

2010-01-01

July 2009: What happens when dark matter and anti-dark mattter collide? If you were in a gravity free environment, what would happen to time? At the annual Cosmology Workshop at Lawrence Berkeley Lab, Nobelist George Smoot answers these questions and more from high school students and teachers. Dr. Smoot was co-awarded the 2006 Nobel Prize in Physics for the discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.

Q and A with Nobelist George Smoot - 2009 BCCP Cosmology Workshop

ScienceCinema

Smoot, George

2018-01-24

July 2009: What happens when dark matter and anti-dark mattter collide? If you were in a gravity free environment, what would happen to time? At the annual Cosmology Workshop at Lawrence Berkeley Lab, Nobelist George Smoot answers these questions and more from high school students and teachers. Dr. Smoot was co-awarded the 2006 Nobel Prize in Physics for the discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.

Hardware-in-the-loop tow missile system simulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waldman, G.S.; Wootton, J.R.; Hobson, G.L.

1993-07-06

A missile system simulator is described for use in training people for target acquisition, missile launch, and missile guidance under simulated battlefield conditions comprising: simulating means for producing a digital signal representing a simulated battlefield environment including at least one target movable therewithin, the simulating means generating an infrared map representing the field-of-view and the target; interface means for converting said digital signals to an infrared image; missile system hardware including the missile acquisition, tracking, and guidance portions thereof, said hardware sensing the infrared image to determine the location of the target in a field-of-view; and, image means for generatingmore » an infrared image of a missile launched at the target and guided thereto, the image means imposing the missile image onto the field-of-view for the missile hardware to acquire the image of the missile in addition to that of the target, and to generate guidance signals to guide the missile image to the target image, wherein the interfacing means is responsive to a guidance signal from the hardware to simulate, in real-time, the response of the missile to the guidance signal, the image means including a blackbody, laser means for irradiating the blackbody to heat it to a temperature at which it emits infrared radiation, and optic means for integrating the radiant image produced by heating the blackbody into the infrared map.« less

Q&A with Nobelist George Smoot - 2009 BCCP Cosmology Workshop

ScienceCinema

George Smoot

2017-12-09

July 2009: What happens when dark matter and anti-dark mattter collide? If you were in a gravity free environment, what would happen to time? At the annual Cosmology Workshop at Lawrence Berkeley Lab, Nobelist George Smoot answers these questions and more from high school students and teachers. Dr. Smoot was co-awarded the 2006 Nobel Prize in Physics for the discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.

H- photodetachment and radiative attachment for astrophysical applications

NASA Astrophysics Data System (ADS)

McLaughlin, B. M.; Stancil, P. C.; Sadeghpour, H. R.; Forrey, R. C.

2017-06-01

We combine R-matrix calculations, asymptotic relations, and comparison to available experimental data to construct an H- photodetachment cross section reliable over a large range of photon energies and take into account the series of auto-detaching shape and Feshbach resonances between 10.92 and 14.35 eV. The accuracy of the cross section is controlled by ensuring that it satisfies all known oscillator strength sum rules, including contributions from the resonances and single-photon double-electron photodetachment. From the resulting recommended cross section, spontaneous and stimulated radiative attachment rate coefficients are obtained. Photodetachment rates are also computed for the standard interstellar radiation field, in diffuse and dense interstellar clouds, for blackbody radiation, and for high redshift distortion photons in the recombination epoch. Implications are investigated for these astrophysical radiation fields and epochs.

Diffusive, Supersonic X-ray Transport in Foam Cylinders

NASA Astrophysics Data System (ADS)

Back, Christina A.

1999-11-01

Diffusive supersonic radiation transport, where the ratio of the diffusive radiation front velocity to the material sound speed >2 has been studied in a series of laboratory experiments on low density foams. This work is of interest for radiation transport in basic science and astrophysics. The Marshak radiation wave transport is studied for both low and high Z foam materials and for different length foams in a novel hohlraum geometry that allows direct comparisons with 2-dimensional analytic models and code simulations. The radiation wave is created by a ~ 80 eV near blackbody 12-ns long drive or a ~ 200 eV 1.2-2.4 ns long drive generated by laser-heated Au hohlraums. The targets are SiO2 and Ta2O5 aerogel foams of varying lengths which span 10 to 50 mg/cc densities. Clean signatures of radiation breakout were observed by radially resolved face-on transmission measurements of the radiation flux at a photon energy of 250 eV or 550 eV. The high quality data provides new detailed information on the importance of both the fill and wall material opacities and heat capacities in determining the radiation front speed and curvature. note number.

Earth Radiation Budget Experiment scanner radiometric calibration results

NASA Technical Reports Server (NTRS)

Lee, Robert B., III; Gibson, M. A.; Thomas, Susan; Meekins, Jeffrey L.; Mahan, J. R.

1990-01-01

The Earth Radiation Budget Experiment (ERBE) scanning radiometers are producing measurements of the incoming solar, earth/atmosphere-reflected solar, and earth/atmosphere-emitted radiation fields with measurement precisions and absolute accuracies, approaching 1 percent. ERBE uses thermistor bolometers as the detection elements in the narrow-field-of-view scanning radiometers. The scanning radiometers can sense radiation in the shortwave, longwave, and total broadband spectral regions of 0.2 to 5.0, 5.0 to 50.0, and 0.2 to 50.0 micrometers, respectively. Detailed models of the radiometers' response functions were developed in order to design the most suitable calibration techniques. These models guided the design of in-flight calibration procedures as well as the development and characterization of a vacuum-calibration chamber and the blackbody source which provided the absolute basis upon which the total and longwave radiometers were characterized. The flight calibration instrumentation for the narror-field-of-view scanning radiometers is presented and evaluated.

The Big Bang, COBE, and the Relic Radiation of Creation (LBNL Science at the Theater)

ScienceCinema

Smoot, George [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2018-05-23

Berkeley Lab's George Smoot won the 2006 Physics Nobel Prize, together with John Mather of NASA Goddard Space Flight Center, for "the discovery of the blackbody form and anisotropy of the cosmic microwave background radiation." The anisotropy showed as small variations in the map of the early universe. This research looks back into the infant universe and provides a better understanding of the origin of galaxies and stars. The cosmic background radiation is a tool to understand the structure and history of the universe and the structure of space-time. These observations have provided increased support for the big bang theory of the universe's origin. The Cosmic Background Explorer (COBE) NASA satellite, launched in 1989, carries instruments that measured various aspects of cosmic microwave background radiation, and produced the data for these compelling scientific results, which opened up a field that continues very actively today.

Io - Ground-based observations of hot spots

NASA Technical Reports Server (NTRS)

Sinton, W. M.; Tokunaga, A. T.; Becklin, E. E.; Gatley, I.; Lee, T. J.; Lonsdale, C. J.

1980-01-01

Observations of Io in eclipse demonstrate conclusively that Io emits substantial amounts of radiation at 4.8 and 3.8 micrometers and a measurable amount at 2.2 micrometers. Color temperatures derived from the observations fit blackbody emission at 560 K. The required source area to yield the observed 4.8-micrometer flux is approximately 5 x 10 to the -5th of the disk of Io and is most likely comprised of small hot spots in the vicinity of the volcanoes.

Q&A with Nobelist George Smoot - 2009 BCCP Cosmology Workshop

DOE Office of Scientific and Technical Information (OSTI.GOV)

George Smoot

2010-06-02

July 2009: What happens when dark matter and anti-dark mattter collide? If you were in a gravity free environment, what would happen to time? At the annual Cosmology Workshop at Lawrence Berkeley Lab, Nobelist George Smoot answers these questions and more from high school students and teachers. Dr. Smoot was co-awarded the 2006 Nobel Prize in Physics for the discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.

Spectral distortions of the cosmic microwave background

NASA Technical Reports Server (NTRS)

Adams, Fred C.; Mcdowell, Jonathan C.; Freese, Katherine; Levin, Janna

1989-01-01

Recent experiments indicate that the spectrum of the cosmic microwave background deviates from a pure blackbody; here, spectral distortions produced by cosmic dust are considered. The main result is that cosmic dust in conjunction with an injected radiation field (perhaps produced by an early generation of very massive stars) can explain the observed spectral distortions without violating existing cosmological constraints. In addition, it is shown that Compton y-distortions can also explain the observed spectral shape, but the energetic requirements are more severe.

Blackbody Cavity for Calibrations at 200 to 273 K

NASA Technical Reports Server (NTRS)

Howell, Dane; Ryan, Robert; Ryan, Jim; Henderson, Doug; Clayton, Larry

2004-01-01

A laboratory blackbody cavity has been designed and built for calibrating infrared radiometers used to measure radiant temperatures in the range from about 200 to about 273 K. In this below-room-temperature range, scattering of background infrared radiation from room-temperature surfaces could, potentially, contribute significantly to the spectral radiance of the blackbody cavity, thereby contributing a significant error to the radiant temperature used as the calibration value. The present blackbody cavity is of an established type in which multiple reflections from a combination of conical and cylindrical black-coated walls are exploited to obtain an effective emissivity greater than the emissivity value of the coating material on a flat exposed surface. The coating material in this case is a flat black paint that has an emissivity of approximately of 0.91 in the thermal spectral range and was selected over other, higher-emissivity materials because of its ability to withstand thermal cycling. We found many black coatings cracked and flaked after thermal cycling due to differences in the coefficient of expansion differences. On the basis of theoretical calculations, the effective emissivity is expected to approach 0.999. The cylindrical/conical shell enclosing the cavity is machined from copper, which is chosen for its high thermal conductivity. In use, the shell is oriented vertically, open end facing up, and inserted in a Dewar flask filled with isopropyl alcohol/dry-ice slush. A flange at the open end of the shell is supported by a thermally insulating ring on the lip of the Dewar flask. The slush cools the shell (and thus the black-body cavity) to the desired temperature. Typically, the slush starts at a temperature of about 194 K. The slush is stirred and warmed by bubbling dry air or nitrogen through it, thereby gradually increasing the temperature through the aforementioned calibration range during an interval of several hours. The temperature of the slush is monitored by use of a precise thermocouple probe.

APMP Scale Comparison with Three Radiation Thermometers and Six Fixed-Point Blackbodies

NASA Astrophysics Data System (ADS)

Yamada, Y.; Shimizu, Y.; Ishii, J.

2015-08-01

New Asia Pacific Metrology Programme (APMP) comparisons of radiation thermometry standards, APMP TS-11, and -12, have recently been initiated. These new APMP comparisons cover the temperature range from to . Three radiation thermometers with central wavelengths of 1.6 , 0.9 , and 0.65 are the transfer devices for the radiation thermometer scale comparison conducted in the so-called star configuration. In parallel, a compact fixed-point blackbody furnace that houses six types of fixed-point cells of In, Sn, Zn, Al, Ag, and Cu is circulated, again in a star-type comparison, to substantiate fixed-point calibration capabilities. Twelve APMP national metrology institutes are taking part in this endeavor, in which the National Metrology Institute of Japan acts as the pilot. In this article, the comparison scheme is described with emphasis on the features of the transfer devices, i.e., the radiation thermometers and the fixed-point blackbodies. Results of preliminary evaluations of the performance and characteristic of these instruments as well as the evaluation method of the comparison results are presented.

Black Hole Universe Model for Explaining GRBs, X-Ray Flares, and Quasars as Emissions of Dynamic Star-like, Massive, and Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Zhang, Tianxi

2014-01-01

Slightly modifying the standard big bang theory, the author has recently developed a new cosmological model called black hole universe, which is consistent with Mach’s principle, governed by Einstein’s general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, cosmic microwave background radiation, and acceleration of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This study investigates the emissions of dynamic black holes according to the black hole universe model and provides a self-consistent explanation for the observations of gamma ray bursts (GRBs), X-ray flares, and quasars as emissions of dynamic star-like, massive, and supermassive black holes. It is shown that a black hole, when it accretes its ambient matter or merges with other black holes, becomes dynamic. Since the event horizon of a dynamic black hole is broken, the inside hot (or high-frequency) blackbody radiation leaks out. The leakage of the inside hot blackbody radiation leads to a GRB if it is a star-like black hole, an X-ray flare if it is a massive black hole like the one at the center of the Milky Way, or a quasar if it is a supermassive black hole like an active galactic nucleus (AGN). The energy spectra and amount of emissions produced by the dynamic star-like, massive, and supermassive black holes can be consistent with the measurements of GRBs, X-ray flares, and quasars.

Microwave blackbodies for spaceborne receivers

NASA Technical Reports Server (NTRS)

Stacey, J. M.

1985-01-01

The properties of microwave blackbody targets are explained as they apply to the calibration of spaceborne receivers. Also described are several practicable, blackbody targets used to test and calibrate receivers in the laboratory and in the thermal vacuum chamber. Problems with the precision and the accuracy of blackbody targets, and blackbody target design concepts that overcome some of the accuracy limitations present in existing target designs, are presented. The principle of the Brewster angle blackbody target is described where the blackbody is applied as a fixed-temperature test target in the laboratory and as a variable-temperature target in the thermal vacuum chamber. The reflectivity of a Brewster angle target is measured in the laboratory. From this measurement, the emissivity of the target is calculated. Radiatively cooled thermal suspensions are discussed as the coolants of blackbody targets and waveguide terminations that function as calibration devices in spaceborne receivers. Examples are given for the design of radiatively cooled thermal suspensions. Corrugated-horn antennas used to observe the cosmic background and to provide a cold-calibration source for spaceborne receivers are described.

Radiation energy receiver for laser and solar propulsion systems

NASA Technical Reports Server (NTRS)

Rault, D. F. G.; Hertzberg, A.

1983-01-01

The concept of remotely heating a rocket propellant with a high intensity radiant energy flux is especially attractive due to its high specific impulse and large payload mass capabilities. In this paper, a radiation receiver-thruster which is especially suited to the particular thermodynamic and spectral characteristics of highly concentrated solar energy is proposed. In this receiver, radiant energy is volumetrically absorbed within a hydrogen gas seeded with alkali metal vapors. The alkali atoms and molecules absorb the radiant flux and, subsequently, transfer their internal excitation to hydrogen molecules through collisional quenching. It is shown that such a radiation receiver would outperform a blackbody cavity type receiver in both efficiency and maximum operating temperatures. A solar rocket equipped with such a receiver-thruster would deliver thrusts of several hundred newtons at a specific impulse of 1000 seconds.

Thermodynamics and Hawking radiation of five-dimensional rotating charged Goedel black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu Shuangqing; Peng Junjin; College of Science, Wuhan Textile University, Wuhan, Hubei 430074

2011-02-15

We study the thermodynamics of Goedel-type rotating charged black holes in five-dimensional minimal supergravity. These black holes exhibit some peculiar features such as the presence of closed timelike curves and the absence of a globally spatial-like Cauchy surface. We explicitly compute their energies, angular momenta, and electric charges that are consistent with the first law of thermodynamics. Besides, we extend the covariant anomaly cancellation method, as well as the approach of the effective action, to derive their Hawking fluxes. Both the methods of the anomaly cancellation and the effective action give the same Hawking fluxes as those from the Planckmore » distribution for blackbody radiation in the background of the charged rotating Goedel black holes. Our results further support that Hawking radiation is a quantum phenomenon arising at the event horizon.« less

Overview and future direction for blackbody solar-pumped lasers

NASA Technical Reports Server (NTRS)

Deyoung, R. J.

1988-01-01

A review of solar-pumped blackbody lasers is given which addresses their present status and suggests future research directions. The blackbody laser concept is one system proposed to scale to multimegawatt power levels for space-to-space power transmissions for such applications as onboard spacecraft electrical or propulsion needs. Among the critical technical issues are the scalability to high powers and the laser wavelength which impacts the transmission optics size as well as the laser-to-electric converter at the receiver. Because present blackbody solar-pumped lasers will have laser wavelengths longer than 4 microns, simple photovoltaic converters cannot be used, and transmission optics will be large. Thus, future blackbody laser systems should emphasize near visible laser wavelengths.

Soft X-ray emission from the Lupus Loop and Sn 1006 supernova remnants

NASA Technical Reports Server (NTRS)

Winkler, P. F., Jr.; Hearn, D. R.; Richardson, J. A.; Behnken, J. M.

1979-01-01

X-ray maps of the Lupus region have been obtained in a raster scan observation from SAS 3. These show the Lupus Loop to be a faint extended source of soft X-rays with a temperature about 2.5 million K. The most prominent feature of the region is the A.D. 1006 supernova remnant, which is unexpectedly bright at 0.2-1.0 keV. One speculative interpretation of the low-energy flux from SN 1006 is as blackbody radiation from a hot neutron star.

Stand-off molecular composition analysis

NASA Astrophysics Data System (ADS)

Hughes, Gary B.; Lubin, Philip; Meinhold, Peter; O'Neill, Hugh; Brashears, Travis; Zhang, Qicheng; Griswold, Janelle; Riley, Jordan; Motta, Caio

2015-09-01

Molecular composition of distant stars is explored by observing absorption spectra. The star produces blackbody radiation that passes through the molecular cloud of vaporized material surrounding the star. Characteristic absorption lines are discernible with a spectrometer, and molecular composition is investigated by comparing spectral observations with known material profiles. Most objects in the solar system—asteroids, comets, planets, moons—are too cold to be interrogated in this manner. Molecular clouds around cold objects consist primarily of volatiles, so bulk composition cannot be probed. Additionally, low volatile density does not produce discernible absorption lines in the faint signal generated by low blackbody temperatures. This paper describes a system for probing the molecular composition of cold solar system targets from a distant vantage. The concept utilizes a directed energy beam to melt and vaporize a spot on a distant target, such as from a spacecraft orbiting the object. With sufficient flux (~10 MW/m2), the spot temperature rises rapidly (to ~2 500 K), and evaporation of all materials on the target surface occurs. The melted spot creates a high-temperature blackbody source, and ejected material creates a molecular plume in front of the spot. Bulk composition is investigated by using a spectrometer to view the heated spot through the ejected material. Spatial composition maps could be created by scanning the surface. Applying the beam to a single spot continuously produces a borehole, and shallow sub-surface composition profiling is also possible. Initial simulations of absorption profiles with laser heating show great promise for molecular composition analysis.

Hawking radiation from dilatonic black holes via anomalies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang Qingquan; Cai Xu; Wu Shuangqing

2007-03-15

Recently, Hawking radiation from a Schwarzschild-type black hole via a gravitational anomaly at the horizon has been derived by Robinson and Wilczek. Their result shows that, in order to demand general coordinate covariance at the quantum level to hold in the effective theory, the flux of the energy-momentum tensor required to cancel the gravitational anomaly at the horizon of the black hole is exactly equal to that of (1+1)-dimensional blackbody radiation at the Hawking temperature. In this paper, we attempt to apply the analysis to derive Hawking radiation from the event horizons of static, spherically symmetric dilatonic black holes withmore » arbitrary coupling constant {alpha}, and that from the rotating Kaluza-Klein ({alpha}={radical}(3)) as well as the Kerr-Sen ({alpha}=1) black holes via an anomalous point of view. Our results support Robinson and Wilczek's opinion. In addition, the properties of the obtained physical quantities near the extreme limit are qualitatively discussed.« less

Gamma ray bursts of black hole universe

NASA Astrophysics Data System (ADS)

Zhang, T. X.

2015-07-01

Slightly modifying the standard big bang theory, Zhang recently developed a new cosmological model called black hole universe, which has only a single postulate but is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain existing observations of the universe. In the previous studies, we have explained the origin, structure, evolution, expansion, cosmic microwave background radiation, quasar, and acceleration of black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This study investigates gamma ray bursts of black hole universe and provides an alternative explanation for the energy and spectrum measurements of gamma ray bursts according to the black hole universe model. The results indicate that gamma ray bursts can be understood as emissions of dynamic star-like black holes. A black hole, when it accretes its star or merges with another black hole, becomes dynamic. A dynamic black hole has a broken event horizon and thus cannot hold the inside hot (or high-frequency) blackbody radiation, which flows or leaks out and produces a GRB. A star when it collapses into its core black hole produces a long GRB and releases the gravitational potential energy of the star as gamma rays. A black hole that merges with another black hole produces a short GRB and releases a part of their blackbody radiation as gamma rays. The amount of energy obtained from the emissions of dynamic star-like black holes are consistent with the measurements of energy from GRBs. The GRB energy spectra derived from this new emission mechanism are also consistent with the measurements.

Optical emission line monitor with background observation and cancellation

DOEpatents

Goff, David R.; Notestein, John E.

1986-01-01

A fiber optics based optical emission line monitoring system is provided in which selected spectral emission lines, such as the sodium D-line emission in coal combustion, may be detected in the presence of interferring background or blackbody radiation with emissions much greater in intensity than that of the emission line being detected. A bifurcated fiber optic light guide is adapted at the end of one branch to view the combustion light which is guided to a first bandpass filter, adapted to the common trunk end of the fiber. A portion of the light is reflected back through the common trunk portion of the fiber to a second bandpass filter adapted to the end of the other branch of the fiber. The first filter bandpass is centered at a wavelength corresponding to the emission line to be detected with a bandwidth of about three nanometers (nm). The second filter is centered at the same wavelength but having a width of about 10 nm. First and second light detectors are located to view the light passing through the first and second filters respectively. Thus, the second detector is blind to the light corresponding to the emission line of interest detected by the first detector and the difference between the two detector outputs is uniquely indicative of the intensity of only the combustion flame emission of interest. This instrument can reduce the effects of interferring blackbody radiation by greater than 20 dB.

Design and application of an array extended blackbody

NASA Astrophysics Data System (ADS)

Zhang, Ya-zhou; Fan, Xiao-li; Lei, Hao; Zhou, Zhi-yuan

2018-02-01

An array extended blackbody is designed to quantitatively measure and evaluate the performance of infrared imaging systems. The theory, structure, control software and application of blackbody are introduced. The parameters of infrared imaging systems such as the maximum detectable range, detection sensitivity, spatial resolution and temperature resolution can be measured.

Micro rectennas: Brownian ratchets for thermal-energy harvesting

NASA Astrophysics Data System (ADS)

Pan, Y.; Powell, C. V.; Song, A. M.; Balocco, C.

2014-12-01

We experimentally demonstrated the operation of a rectenna for harvesting thermal (blackbody) radiation and converting it into dc electric power. The device integrates an ultrafast rectifier, the self-switching nanodiode, with a wideband log-periodic spiral microantenna. The radiation from the thermal source drives the rectenna out of thermal equilibrium, permitting the rectification of the excess thermal fluctuations from the antenna. The power conversion efficiency increases with the source temperatures up to 0.02% at 973 K. The low efficiency is attributed mainly to the impedance mismatch between antenna and rectifier, and partially to the large field of view of the antenna. Our device not only opens a potential solution for harvesting thermal energy but also provides a platform for experimenting with Brownian ratchets.

Solar powered blackbody-pumped lasers

NASA Astrophysics Data System (ADS)

Christiansen, Walter H.; Sirota, J. M.

1991-02-01

A concept for a solar-powered laser is presented which utilizes an intermediate blackbody cavity to provide a uniform optical pumping environment for the lasant, typically CO or CO2 or possibly a solid state laser medium. High power cw blackbody- pumped lasers with efficiencies on the order of 20 percent or more are feasible. The physical basis of this idea is reviewed. Small scale experiments using a high temperature oven as the optical pump have been carried out with gas laser mixtures. Detailed calculations showing a potential efficiency of 35 percent for blackbody pumped Nd:YAG system are discussed.

Micro rectennas: Brownian ratchets for thermal-energy harvesting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Y.; Powell, C. V.; Balocco, C., E-mail: claudio.balocco@durham.ac.uk

2014-12-22

We experimentally demonstrated the operation of a rectenna for harvesting thermal (blackbody) radiation and converting it into dc electric power. The device integrates an ultrafast rectifier, the self-switching nanodiode, with a wideband log-periodic spiral microantenna. The radiation from the thermal source drives the rectenna out of thermal equilibrium, permitting the rectification of the excess thermal fluctuations from the antenna. The power conversion efficiency increases with the source temperatures up to 0.02% at 973 K. The low efficiency is attributed mainly to the impedance mismatch between antenna and rectifier, and partially to the large field of view of the antenna. Our devicemore » not only opens a potential solution for harvesting thermal energy but also provides a platform for experimenting with Brownian ratchets.« less

Infrared cameras are potential traceable "fixed points" for future thermometry studies.

PubMed

Yap Kannan, R; Keresztes, K; Hussain, S; Coats, T J; Bown, M J

2015-01-01

The National physical laboratory (NPL) requires "fixed points" whose temperatures have been established by the International Temperature Scale of 1990 (ITS 90) be used for device calibration. In practice, "near" blackbody radiators together with the standard platinum resistance thermometer is accepted as a standard. The aim of this study was to report the correlation and limits of agreement (LOA) of the thermal infrared camera and non-contact infrared temporal thermometer against each other and the "near" blackbody radiator. Temperature readings from an infrared thermography camera (FLIR T650sc) and a non-contact infrared temporal thermometer (Hubdic FS-700) were compared to a near blackbody (Hyperion R blackbody model 982) at 0.5 °C increments between 20-40 °C. At each increment, blackbody cavity temperature was confirmed with the platinum resistance thermometer. Measurements were taken initially with the thermal infrared camera followed by the infrared thermometer, with each device mounted in turn on a stand at a fixed distance of 20 cm and 5 cm from the blackbody aperture, respectively. The platinum thermometer under-estimated the blackbody temperature by 0.015 °C (95% LOA: -0.08 °C to 0.05 °C), in contrast to the thermal infrared camera and infrared thermometer which over-estimated the blackbody temperature by 0.16 °C (95% LOA: 0.03 °C to 0.28 °C) and 0.75 °C (95% LOA: -0.30 °C to 1.79 °C), respectively. Infrared thermometer over-estimates thermal infrared camera measurements by 0.6 °C (95% LOA: -0.46 °C to 1.65 °C). In conclusion, the thermal infrared camera is a potential temperature reference "fixed point" that could substitute mercury thermometers. However, further repeatability and reproducibility studies will be required with different models of thermal infrared cameras.

Monte Carlo Study on Carbon-Gradient-Doped Silica Aerogel Insulation.

PubMed

Zhao, Y; Tang, G H

2015-04-01

Silica aerogel is almost transparent for wavelengths below 8 µm where significant energy is transferred by thermal radiation. The radiative heat transfer can be restricted at high temperature if doped with carbon powder in silica aerogel. However, different particle sizes of carbon powder doping have different spectral extinction coefficients and the doped carbon powder will increase the solid conduction of silica aerogel. This paper presents a theoretical method for determining the optimal carbon doping in silica aerogel to minimize the energy transfer. Firstly we determine the optimal particle size by combining the spectral extinction coefficient with blackbody radiation and then evaluate the optimal doping amount between heat conduction and radiation. Secondly we develop the Monte Carlo numerical method to study radiative properties of carbon-gradient-doped silica aerogel to decrease the radiative heat transfer further. The results indicate that the carbon powder is able to block infrared radiation and thus improve the thermal insulating performance of silica aerogel effectively.

Optical emission line monitor with background observation and cancellation

DOEpatents

Goff, D.R.; Notestein, J.E.

1985-01-04

A fiber optics based optical emission line monitoring system is provided in which selected spectral emission lines, such as the sodium D-line emission in coal combustion, may be detected in the presence of interferring background or blackbody radiation with emissions much greater in intensity than that of the emission line being detected. A bifurcated fiber optic light guide is adapted at the end of one branch to view the combustion light which is guided to a first bandpass filter, adapted to the common trunk end of the fiber. A portion of the light is reflected back through the common trunk portion of the fiber to a second bandpass filter adapted to the end of the other branch of the fiber. The first filter bandpass is centered at a wavelength corresponding to the emission line to be detected with a bandwidth of about three nanometers (nm). The second filter is centered at the same wavelength but having a width of about 10 nm. First and second light detectors are located to view the light passing through the first and second filters respectively. Thus, the second detector is blind to the light corresponding to the emission line of interest detected by the first detector and the difference between the two detector outputs is uniquely indicative of the intensity of only the combustion flame emission of interest. This instrument can reduce the effects of interfering blackbody radiation by greater than 20 dB.

An Oil-Bath-Based 293 K to 473 K Blackbody Source

PubMed Central

Fowler, Joel B.

1996-01-01

A high temperature oil-bath-based-black-body source has been designed and constructed in the Radiometric Physics Division at the National Institute of Standards and Technology, Gaithersburg, MD. The goal of this work was to design a large aperture blackbody source with highly uniform radiance across the aperture, good temporal stability, and good reproducibility. This blackbody source operates in the 293 K to 473 K range with blackbody temperature combined standard uncertainties of 7.2 mK to 30.9 mK. The calculated emissivity of this source is 0.9997 with a standard uncertainty of 0.0003. With a 50 mm limiting aperture at the cavity entrance, the emissivity increases to 0.99996. PMID:27805082

Transient thermal modeling of the nonscanning ERBE detector

NASA Technical Reports Server (NTRS)

Mahan, J. R.

1983-01-01

A numerical model to predict the transient thermal response of the ERBE nonscanning wide field of view total radiometer channel was developed. The model, which uses Monte Carlo techniques to characterize the radiative component of heat transfer, is described and a listing of the computer program is provided. Application of the model to simulate the actual blackbody calibration procedure is discussed. The use of the model to establish a real time flight data interpretation strategy is recommended. Modification of the model to include a simulated Earth radiation source field and a filter dome is indicated.

First Octahedral Spherical Hohlraum Energetics Experiment at the SGIII Laser Facility

NASA Astrophysics Data System (ADS)

Huo, Wen Yi; Li, Zhichao; Chen, Yao-Hua; Xie, Xufei; Ren, Guoli; Cao, Hui; Li, Shu; Lan, Ke; Liu, Jie; Li, Yongsheng; Li, Sanwei; Guo, Liang; Liu, Yonggang; Yang, Dong; Jiang, Xiaohua; Hou, Lifei; Du, Huabing; Peng, Xiaoshi; Xu, Tao; Li, Chaoguang; Zhan, Xiayu; Wang, Zhebin; Deng, Keli; Wang, Qiangqiang; Deng, Bo; Wang, Feng; Yang, Jiamin; Liu, Shenye; Jiang, Shaoen; Yuan, Guanghui; Zhang, Haijun; Jiang, Baibin; Zhang, Wei; Gu, Qianqian; He, Zhibing; Du, Kai; Deng, Xuewei; Zhou, Wei; Wang, Liquan; Huang, Xiaoxia; Wang, Yuancheng; Hu, Dongxia; Zheng, Kuixing; Zhu, Qihua; Ding, Yongkun

2018-04-01

The first octahedral spherical hohlraum energetics experiment is accomplished at the SGIII laser facility. For the first time, the 32 laser beams are injected into the octahedral spherical hohlraum through six laser entrance holes. Two techniques are used to diagnose the radiation field of the octahedral spherical hohlraum in order to obtain comprehensive experimental data. The radiation flux streaming out of laser entrance holes is measured by six flat-response x-ray detectors (FXRDs) and four M -band x-ray detectors, which are placed at different locations of the SGIII target chamber. The radiation temperature is derived from the measured flux of FXRD by using the blackbody assumption. The peak radiation temperature inside hohlraum is determined by the shock wave technique. The experimental results show that the octahedral spherical hohlraum radiation temperature is in the range of 170-182 eV with drive laser energies of 71 kJ to 84 kJ. The radiation temperature inside the hohlraum determined by the shock wave technique is about 175 eV at 71 kJ. For the flat-top laser pulse of 3 ns, the conversion efficiency of gas-filled octahedral spherical hohlraum from laser into soft x rays is about 80% according to the two-dimensional numerical simulation.

Active photonic lattices: is greater than blackbody intensity possible?

DOE PAGES

Chow, W. W.; Waldmueller, I.

2006-11-10

In this paper, the emission from a radiating source embedded in a photonic lattice is investigated. The photonic lattice spectrum was found to deviate from the blackbody distribution, with intracavity emission suppressed at certain frequencies and significantly enhanced at others. For rapid population relaxation, where the photonic lattice and blackbody populations are described by the same thermal distribution, it was found that the enhancement does not result in output intensities exceeding those of the blackbody. Finally, however, for slow population relaxation, the photonic lattice population has a greater tendency to deviate from thermal equilibrium, resulting in output intensities exceeding thosemore » of the blackbody.« less

A STATE-DEPENDENT INFLUENCE OF TYPE I BURSTS ON THE ACCRETION IN 4U 1608-52?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Long; Zhang, Shu; Chen, YuPeng

2014-08-20

We investigated the possible feedback of type I bursts on the accretion process during the spectral evolution of the atoll source 4U 1608-52. By fitting the burst spectrum with a blackbody and an adjustable, persistent spectral component, we found that the latter is significantly state-dependent. In the banana state, the persistent flux increases along the burst evolution, while in the island state this trend holds only when the bursts are less luminous and start to reverse at higher burst luminosities. We speculate that, by taking into account both the Poynting-Robertson drag and radiation pressure, these phenomena may arise from the interactionsmore » between the radiation field of the type I burst and the inner region of the accretion disk.« less

Spectral infrared hemispherical reflectance measurements for LDEF tray clamps

NASA Technical Reports Server (NTRS)

Wood, Bobby E.; Cromwell, Brian K.; Pender, Charles W.; Shepherd, Seth D.

1992-01-01

This paper describes infrared hemispherical reflectance measurements (2-15 microns) that were made on 58 chromic acid anodized tray clamps retrieved from the LDEF spacecraft. These clamps were used for maintaining the experiments in place and were located at various locations about the spacecraft. Changes in reflectance of the tray clamps at these locations were compared with atomic oxygen fluxes at the same locations. A decrease in absorption band depth was seen for the surfaces exposed to space indicating that there was some surface layer erosion. In all of the surfaces measured, little evidence of contamination was observed and none of the samples showed evidence of the brown nicotine stain that was so prominent in other experiments. Total emissivity values were calculated for both exposed and unexposed tray clamp surfaces. Only small differences, usually less than 1 percent, were observed. The spectral reflectances were measured using a hemi-ellipsoidal mirror reflectometer matched with an interferometer spectrometer. The rapid scanning capability of the interferometer allowed the reflectance measurements to be made in a timely fashion. The ellipsoidal mirror has its two foci separated by 2 inches and located on the major axis. A blackbody source was located at one focus while the tray clamp samples were located at the conjugate focus. The blackbody radiation was modulated and then focused by the ellipsoid onto the tray clamps. Radiation reflected from the tray clamp was sampled by the interferometer by viewing through a hole in the ellipsoid. A gold mirror (reflectance approximately 98 percent) was used as the reference surface.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evtushenko, Pavel E.; Klopf, John M.

Frequency domain measurements with Martin-Puplett interferometer is one of a few techniques capable of bunch length measurements at the level of ~ 100 fs. As the bunch length becomes shorter, it is important to know and be able to measure the limitations of the instrument in terms of shortest measurable bunch length. In this paper we describe an experiment using a blackbody source with the modified Martin-Puplett interferometer that is routine- ly used for bunch length measurements at the JLab FEL, as a way to estimate the shortest, measurable bunch length. The limitation comes from high frequency cut-off of themore » wire-grid polarizer currently used and is estimated to be 50 fs RMS. The measurements are made with the same Golay cell detector that is used for beam measure- ments. We demonstrate that, even though the blackbody source is many orders of magnitude less bright than the coherent transition or synchrotron radiation, it can be used for the measurements and gives a very good signal to noise ratio in combination with lock-in detection. We also compare the measurements made in air and in vacuum to characterize the very strong effect of the atmospheric absorption.« less

A SUPER-EDDINGTON, COMPTON-THICK WIND IN GRO J1655–40?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neilsen, J.; Homan, J.; Rahoui, F.

2016-05-01

During its 2005 outburst, GRO J1655–40 was observed at high spectral resolution with the Chandra High-Energy Transmission Grating Spectrometer, revealing a spectrum rich with blueshifted absorption lines indicative of an accretion disk wind—apparently too hot, too dense, and too close to the black hole to be driven by radiation pressure or thermal pressure (Miller et al.). However, this exotic wind represents just one piece of the puzzle in this outburst, as its presence coincides with an extremely soft and curved X-ray continuum spectrum, remarkable X-ray variability (Uttley and Klein-Wolt), and a bright, unexpected optical/infrared blackbody component that varies on themore » orbital period. Focusing on the X-ray continuum and the optical/infrared/UV spectral energy distribution, we argue that the unusual features of this “hypersoft state” are natural consequences of a super-Eddington Compton-thick wind from the disk: the optical/infrared blackbody represents the cool photosphere of a dense, extended outflow, while the X-ray emission is explained as Compton scattering by the relatively cool, optically thick wind. This wind obscures the intrinsic luminosity of the inner disk, which we suggest may have been at or above the Eddington limit.« less

Why Don't We See in the Infrared?

NASA Astrophysics Data System (ADS)

Brecher, K.

1998-12-01

Solar radiation reaching the surface of the Earth includes a wide range of wavelengths and frequencies, with the peak of intensity including the infrared, visible and ultraviolet regions of the electromagnetic spectrum. In fact, the largest number of solar photons reaching our eyes arrives in the near infrared. Why, then, don't we see the world in the infrared? Many astronomy textbooks, both elementary and advanced, argue that the human eye has evolved to act as a kind of `solar Wien peak detector'. They note that if one uses the effective solar blackbody temperature of 5770 K, then, according to Wien's displacement law, the peak of the solar flux occurs at a wavelength of about 503 nm. Rods in the human eye peak in sensitivity at about 507 nm. Therefore, according to this line of reasoning, the human eye has evolved to avail itself of the Wien peak of the solar spectrum. (However, it should be noted that the peak sensitivity of the three different kinds of cones range from about 420 nm to about 560 nm). This astronomical argument is, at best, misleading. The solar blackbody spectrum, evaluated as a function of frequency, has a peak at about 340 THz. This is in the near infrared at a wavelength of about 884 nm. Since the human eye acts as an efficient quantum detector of photons, this is the appropriate solar radiation referent. Thus the Wien peak of the solar spectrum is not the reason that the eye's (scotopic) sensitivity peaks in the green. Many other factors contribute. Probably the most important are biochemical ones, which are constrained by available molecules such as rhodopsin that are useful for radiation to matter energy transfer. Physics also plays a role, because of absorption, scattering, refraction and diffraction. Other effects, including the Earth's atmospheric transmission and terrestrial surface reflectivities, may also matter.

Design and Construction of a Small Vacuum Furnace

NASA Astrophysics Data System (ADS)

Peawbang, P.; Thedsakhulwong, A.

2017-09-01

The purpose of this research is designed and constructed of a small vacuum furnace. A cylindrical graphite was chosen as the material of the furnace, the cylinder aluminium and copper sheets were employed to prevent the heat radiation that transfers from the furnace to the chamber wall. A rotary pump used, the pressure of graphite furnace can be pumped up to 30 mTorr and heated up to 700 °C driving by wire and the temperature of the chamber wall is relatively remained too low. In addition, heat loss obtained from the graphite furnace by conduction, convection, and radiation were analyzed. The dominating heat loss was found to be caused by the blackbody radiation, which can thus be used to estimate the relationship between graphite furnace temperature and the drive power needed. The cylindrical graphite furnace has an inner diameter of 44 mm, the outer diameter of 60 mm and 45 mm in height, the 355.5 W of power is needed to drive the furnace to 700 °C.

Precision Measurement of Phonon-Polaritonic Near-Field Energy Transfer between Macroscale Planar Structures Under Large Thermal Gradients

NASA Astrophysics Data System (ADS)

Ghashami, Mohammad; Geng, Hongyao; Kim, Taehoon; Iacopino, Nicholas; Cho, Sung Kwon; Park, Keunhan

2018-04-01

Despite its strong potentials in emerging energy applications, near-field thermal radiation between large planar structures has not been fully explored in experiments. Particularly, it is extremely challenging to control a subwavelength gap distance with good parallelism under large thermal gradients. This article reports the precision measurement of near-field radiative energy transfer between two macroscale single-crystalline quartz plates that support surface phonon polaritons. Our measurement scheme allows the precise control of a gap distance down to 200 nm in a highly reproducible manner for a surface area of 5 × 5 mm2 . We have measured near-field thermal radiation as a function of the gap distance for a broad range of thermal gradients up to ˜156 K , observing more than 40 times enhancement of thermal radiation compared to the blackbody limit. By comparing with theoretical prediction based on fluctuational electrodynamics, we demonstrate that such remarkable enhancement is owing to phonon-polaritonic energy transfer across a nanoscale vacuum gap.

Precision Measurement of Phonon-Polaritonic Near-Field Energy Transfer between Macroscale Planar Structures Under Large Thermal Gradients.

PubMed

Ghashami, Mohammad; Geng, Hongyao; Kim, Taehoon; Iacopino, Nicholas; Cho, Sung Kwon; Park, Keunhan

2018-04-27

Despite its strong potentials in emerging energy applications, near-field thermal radiation between large planar structures has not been fully explored in experiments. Particularly, it is extremely challenging to control a subwavelength gap distance with good parallelism under large thermal gradients. This article reports the precision measurement of near-field radiative energy transfer between two macroscale single-crystalline quartz plates that support surface phonon polaritons. Our measurement scheme allows the precise control of a gap distance down to 200 nm in a highly reproducible manner for a surface area of 5×5  mm^{2}. We have measured near-field thermal radiation as a function of the gap distance for a broad range of thermal gradients up to ∼156  K, observing more than 40 times enhancement of thermal radiation compared to the blackbody limit. By comparing with theoretical prediction based on fluctuational electrodynamics, we demonstrate that such remarkable enhancement is owing to phonon-polaritonic energy transfer across a nanoscale vacuum gap.

Experimental and Metrological Basis for SI-Traceable Infrared Radiance Measurements From Space

NASA Astrophysics Data System (ADS)

Gero, P. J.; Dykema, J. A.; Anderson, J. G.; Leroy, S. S.

2007-12-01

In order to establish a climate benchmark record and to be useful in interdecadal climate forecast testing, satellite measurements of high spectral resolution infrared radiance must have uncertainty estimates that can be proven beyond a doubt. An uncertainty in radiance of about 1 part in 1000 is required for climate applications. This can be accomplished by appealing to the best measurement practices of the metrology community. The International System of Units (SI) are linked to fundamental physical properties of matter, and can be realized anywhere in the world without bias. By doing so, one can make an accurate observation to within a specified uncertainty. Achieving SI-traceable radiance measurements from space is a novel requirement, and requires specialized sensor design and a disciplined experimental approach. Infrared remote sensing satellite instruments typically employ blackbody calibration targets, which are tied to the SI through Planck's law and the definition of the Kelvin. The blackbody temperature and emissivity, however, must be determined accurately on- orbit, in order for the blackbody emission scale to be SI-traceable. We outline a methodology of instrument design, pre-flight calibration and on-orbit diagnostics for realizing SI- traceable infrared radiance measurements. This instrument is intended as a component of the Climate Absolute Radiance and Refractivity Earth Observatory (CLARREO), a high priority recommendation of the National Research Council decadal survey. Calibration blackbodies for remote sensing differ from a perfect Planckian blackbody; thus the component uncertainties must be evaluated in order to confer traceability. We have performed traceability experiments in the laboratory to verify blackbody temperature, emissivity and the end-to-end radiance scale. We discuss the design of the Harvard standard blackbody and an intercomparison campaign that will be conducted with the GIFTS blackbody (University of Wisconsin, Madison) and radiometric calibration facilities at NIST. The GIFTS blackbody is a high-performance space-qualified design with a new generation of on-orbit thermometer calibration via miniaturized fixed point cells. NIST facilities allow the step-by-step measurement of blackbody surface properties, thermal properties, on-axis emissivity, and end-to-end radiometric performance. These activities will lay the experimental groundwork for achieving SI-traceable infrared radiance measurements on a satellite instrument.

FSD: Frequency Space Differential measurement of CMB spectral distortions

NASA Astrophysics Data System (ADS)

Mukherjee, Suvodip; Silk, Joseph; Wandelt, Benjamin D.

2018-07-01

Although the cosmic microwave background (CMB) agrees with a perfect blackbody spectrum within the current experimental limits, it is expected to exhibit certain spectral distortions with known spectral properties. We propose a new method Frequency Space Differential (FSD) to measure the spectral distortions in the CMB spectrum by using the inter-frequency differences of the brightness temperature. The difference between the observed CMB temperature at different frequencies must agree with the frequency derivative of the blackbody spectrum in the absence of any distortion. However, in the presence of spectral distortions, the measured inter-frequency differences would also exhibit deviations from blackbody that can be modelled for known sources of spectral distortions like y and μ. Our technique uses FSD information for the CMB blackbody, y, μ, or any other sources of spectral distortions to model the observed signal. Successful application of this method in future CMB missions can provide an alternative method to extract spectral distortion signals and can potentially make it feasible to measure spectral distortions without an internal blackbody calibrator.

Energy and Emission Characteristics of a Short-Arc Xenon Flash Lamp Under "Saturated" Optical Brightness Conditions

NASA Astrophysics Data System (ADS)

Kamrukov, A. S.; Kireev, S. G.; Kozlov, N. P.; Shashkovskii, S. G.

2017-09-01

We present the results of a study of the electrical, energy, and spectral brightness characteristics of an experimental three-electrode high-pressure xenon flash lamp under conditions ensuring close to maximum possible spectral brightness for the xenon emission. We show that under saturated optical brightness conditions (brightness temperature in the visible region of the spectrum 30,000 K), emission of a pulsed discharge in xenon is quite different from the emission from an ideal blackbody: the maximum brightness temperatures are 24,000 K in the short-wavelength UV region and 19,000 K in the near IR range. The relative fraction of UV radiation in the emission spectrum of the lamp is >50%, which lets us consider such lamps as promising broadband sources of radiation with high spectral brightness for many important practical applications.

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) on-board blackbody calibration system

NASA Astrophysics Data System (ADS)

Best, Fred A.; Revercomb, Henry E.; Knuteson, Robert O.; Tobin, David C.; Ellington, Scott D.; Werner, Mark W.; Adler, Douglas P.; Garcia, Raymond K.; Taylor, Joseph K.; Ciganovich, Nick N.; Smith, William L., Sr.; Bingham, Gail E.; Elwell, John D.; Scott, Deron K.

2005-01-01

The NASA New Millennium Program's Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) instrument provides enormous advances in water vapor, wind, temperature, and trace gas profiling from geostationary orbit. The top-level instrument calibration requirement is to measure brightness temperature to better than 1 K (3 sigma) over a broad range of atmospheric brightness temperatures, with a reproducibility of +/-0.2 K. For in-flight radiometric calibration, GIFTS uses views of two on-board blackbody sources (290 K and 255 K) along with cold space, sequenced at regular programmable intervals. The blackbody references are cavities that follow the UW Atmospheric Emitted Radiance Interferometer (AERI) design, scaled to the GIFTS beam size. The cavity spectral emissivity is better than 0.998 with an absolute uncertainty of less than 0.001. Absolute blackbody temperature uncertainties are estimated at 0.07 K. This paper describes the detailed design of the GIFTS on-board calibration system that recently underwent its Critical Design Review. The blackbody cavities use ultra-stable thermistors to measure temperature, and are coated with high emissivity black paint. Monte Carlo modeling has been performed to calculate the cavity emissivity. Both absolute temperature and emissivity measurements are traceable to NIST, and detailed uncertainty budgets have been developed and used to show the overall system meets accuracy requirements. The blackbody controller is housed on a single electronics board and provides precise selectable set point temperature control, thermistor resistance measurement, and the digital interface to the GIFTS instrument. Plans for the NIST traceable ground calibration of the on-board blackbody system have also been developed and are presented in this paper.

The Observed Galactic Annihilation Line: Possible Signature of Accreting Small Mass Black Holes in the Galactic Center

NASA Technical Reports Server (NTRS)

Titarchuk, Lev; Chardonnet, Pascal

2006-01-01

Various balloon and satellite observatories have revealed what appears to be an extended source of 0.511 MeV annihilation radiation with flux of approx. 10(exp -3) photons/sq cm/s centered on the Galactic Center. Positrons from radioactive products of stellar explosions can account for a significant fraction of the emission. We discuss an additional source for this emission: namely e(+)e(-) pairs produced when X-rays generated from the approx. 2.6 x 10(exp 6) solar mass Galactic Center Black Hole interact with approx. 10 MeV temperature blackbody emission from 10(exp 17) g black holes within 10(exp 14-l5) cm of the center. The number of such Small Mass Black Holes (SMMBHs) can account for the production of the 10(exp 42) e(+)/s that produces the observed annihilation in the inner Galaxy when transport effects are taken into account. We consider the possibility for confirming the presence of these SMMBHs in the Galactic Center region with future generations of gamma-ray instruments if a blackbody like emission of approx. 10 MeV temperature would be detected by them. Small Mass Black Hole can be a potential candidate for dark (invisible) matter hal

Electromagnetic Design and Performance of a Conical Microwave Blackbody Target for Radiometer Calibration

NASA Astrophysics Data System (ADS)

Houtz, Derek A.; Emery, William; Gu, Dazhen; Jacob, Karl; Murk, Axel; Walker, David K.; Wylde, Richard J.

2017-08-01

A conical cavity has been designed and fabricated for use as a broadband passive microwave calibration source, or blackbody, at the National Institute of Standards and Technology. The blackbody will be used as a national primary standard for brightness temperature and will allow for the prelaunch calibration of spaceborne radiometers and calibration of ground-based systems to provide traceability among radiometric data. The conical geometry provides performance independent of polarization, minimizing reflections, and standing waves, thus having a high microwave emissivity. The conical blackbody has advantages over typical pyramidal array geometries, including reduced temperature gradients and excellent broadband electromagnetic performance over more than a frequency decade. The blackbody is designed for use between 18 and 230 GHz, at temperatures between 80 and 350 K, and is vacuum compatible. To approximate theoretical blackbody behavior, the design maximizes emissivity and thus minimizes reflectivity. A newly developed microwave absorber is demonstrated that uses cryogenically compatible, thermally conductive two-part epoxy with magnetic carbonyl iron (CBI) powder loading. We measured the complex permittivity and permeability properties for different CBI-loading percentages; the conical absorber is then designed and optimized with geometric optics and finite-element modeling, and finally, the reflectivity of the resulting fabricated structure is measured. We demonstrated normal incidence reflectivity considerably below -40 dB at all relevant remote sensing frequencies.

The development of hurricane Inez, 1966, as shown by satellite nighttime radiometric and daytime television coverage

NASA Technical Reports Server (NTRS)

Allison, L. J.

1972-01-01

A complete documentation of Numbus 2 High Resolution infrared Radiometer data and ESSA-1 and 3 television photographs is presented for the life-time of Hurricane Inez, 1966. Ten computer produced radiation charts were analyzed in order to delineate the three dimensional cloud structure during the formative, mature and dissipating stages of this tropical cyclone. Time sections were drawn throughout the storm's life cycle to relate the warm core development and upper level outflow of the storm with their respective cloud canopies, as shown by the radiation data. Aerial reconnaissance weather reports, radar photographs and conventional weather analyses were used to complement the satellite data. A computer program was utilized to accept Nimbus 2 HRIR equivalent blackbody temperatures within historical maximum and minimum sea surface temperature limits over the tropical Atlantic Ocean.

Electromagnetic crystal based terahertz thermal radiators and components

NASA Astrophysics Data System (ADS)

Wu, Ziran

This dissertation presents the investigation of thermal radiation from three-dimensional electromagnetic crystals (EMXT), as well as the development of a THz rapid prototyping fabrication technique and its application in THz EMXT components and micro-system fabrication and integration. First, it is proposed that thermal radiation from a 3-D EMXT would be greatly enhanced at the band gap edge frequency due to the redistribution of photon density of states (DOS) within the crystal. A THz thermal radiator could thus be built upon a THz EMXT by utilizing the exceptional emission peak(s) around its band gap frequency. The thermal radiation enhancement effects of various THz EMXT including both silicon and tungsten woodpile structures (WPS) and cubic photonic cavity (CPC) array are explored. The DOS of all three structures are calculated, and their thermal radiation intensities are predicted using Planck's Equation. These calculations show that the DOS of the silicon and tungsten WPS can be enhanced by a factor of 11.8 around 364 GHz and 2.6 around 406 GHz respectively, in comparison to the normal blackbody radiation at same frequencies. An enhancement factor of more than 100 is obtained in calculation from the CPC array. A silicon WPS with a band gap around 200 GHz has been designed and fabricated. Thermal emissivity of the silicon WPS sample is measured with a control blackbody as reference. And enhancements of the emission from the WPS over the control blackbody are observed at several frequencies quite consistent with the theoretical predictions. Second, the practical challenge of THz EMXT component and system fabrication is met by a THz rapid prototyping technique developed by us. Using this technique, the fabrications of several EMXTs with 3D electromagnetic band gaps in the 100-400 GHz range are demonstrated. Characterization of the samples via THz Time-domain Spectroscopy (THz-TDS) shows very good agreement with simulation, confirming the build accuracy of this prototyping approach. Third, an all-dielectric THz waveguide is designed, fabricated and characterized. The design is based on hollow-core EMXT waveguide, and the fabrication is implemented with the THz prototyping method. Characterization results of the waveguide power loss factor show good consistency with the simulation, and waveguide propagation loss as low as 0.03 dB/mm at 105 GHz is demonstrated. Several design parameters are also varied and their impacts on the waveguide performance investigated theoretically. Finally, a THz EMXT antenna based on expanding the defect radius of the EMXT waveguide to a horn shape is proposed and studied. The boresight directivity and main beam angular width of the optimized EMXT horn antenna is comparable with a copper horn antenna of the same dimensions at low frequencies, and much better than the copper horn at high frequencies. The EMXT antenna has been successfully fabricated via the same THz prototyping, and we believe this is the first time an EMXT antenna of this architecture is fabricated. Far-field measurement of the EMXT antenna radiation pattern is undergoing. Also, in order to integrate planar THz solid-state devices (especially source and detector) and THz samples under test with the potential THz micro-system fabricate-able by the prototyping approach, an EMXT waveguide-to-microstrip line transition structure is designed. The structure uses tapered solid dielectric waveguides on both ends to transit THz energy from the EMXT waveguide defect onto the microstrip line. Simulation of the transition structure in a back-to-back configuration yields about -15 dB insertion loss mainly due to the dielectric material loss. The coupling and radiation loss of the transition structure is estimated to be -2.115 dB. The fabrication and characterization of the transition system is currently underway. With all the above THz components realized in the future, integrated THz micro-systems manufactured by the same prototyping technique will be achieved, with low cost, high quality, self-sufficiency, and great customizability.

The Vela pulsar with an active fallback disk

DOE Office of Scientific and Technical Information (OSTI.GOV)

Özsükan, Gökçe; Ekşi, K. Yavuz; Hambaryan, Valeri

2014-11-20

Fallback disks are expected to form around young neutron stars. The presence of these disks can be revealed by their blackbody spectrum in the infrared, optical, and UV bands. We present a re-reduction of the archival optical and infrared data of the Vela pulsar, together with the existing infrared and UV spectrum of Vela, and model their unpulsed components with the blackbody spectrum of a supernova debris disk. We invoke the quiescent disk solution of Sunyaev and Shakura for the description of the disk in the propeller stage and find the inner radius of the disk to be inside themore » light cylinder radius. We perform a high-resolution X-ray analysis with XMM-Newton and find a narrow absorption feature at 0.57 keV that can be interpreted as the K {sub α} line of He-like oxygen (O VII). The strength of the line indicates an element over-abundance in our line of sight exceeding the amounts that would be expected from interstellar medium. The spectral feature may originate from the pulsar wind nebula and may be partly caused by the reprocessed X-ray radiation by the fallback disk. We discuss the lower-than-three braking index of Vela as partially due to the contribution of the propeller torques. Our results suggest that the pulsar mechanism can work simultaneously with the propeller processes and that the debris disks can survive the radiation pressure for at least ∼10{sup 4} yr. As Vela is a relatively close object, and a prototypical pulsar, the presence of a disk, if confirmed, may indicate the ubiquity of debris disks around young neutron stars.« less

Molecular Composition Analysis of Distant Targets

NASA Technical Reports Server (NTRS)

Hughes, Gary B.; Lubin, Philip

2017-01-01

This document is the Final Report for NASA Innovative Advanced Concepts (NIAC) Phase I Grant 15-NIAC16A-0145, titled Molecular Composition Analysis of Distant Targets. The research was focused on developing a system concept for probing the molecular composition of cold solar system targets, such as Asteroids, Comets, Planets and Moons from a distant vantage, for example from a spacecraft that is orbiting the target (Hughes et al., 2015). The orbiting spacecraft is equipped with a high-power laser, which is run by electricity from photovoltaic panels. The laser is directed at a spot on the target. Materials on the surface of the target are heated by the laser beam, and begin to melt and then evaporate, forming a plume of asteroid molecules in front of the heated spot. The heated spot glows, producing blackbody illumination that is visible from the spacecraft, via a path through the evaporated plume. As the blackbody radiation from the heated spot passes through the plume of evaporated material, molecules in the plume absorb radiation in a manner that is specific to the rotational and vibrational characteristics of the specific molecules. A spectrometer aboard the spacecraft is used to observe absorption lines in the blackbody signal. The pattern of absorption can be used to estimate the molecular composition of materials in the plume, which originated on the target. Focusing on a single spot produces a borehole, and shallow subsurface profiling of the targets bulk composition is possible. At the beginning of the Phase I research, the estimated Technology Readiness Level (TRL) of the system was TRL-1. During the Phase I research, an end-to-end theoretical model of the sensor system was developed from first principles. The model includes laser energy and optical propagation, target heating, melting and evaporation of target material, plume density, thermal radiation from the heated spot, molecular cross section of likely asteroid materials, and estimation of the absorption profile at a distant spectrometer. Results obtained by executing simulations based on the model provide compelling evidence that the concept of remote laser evaporative molecular absorption spectroscopy is feasible. In this document, technical details of the model are presented, and results of simulations are described that indicate the utility of the proposed sensor system. Additionally, an asteroid rendezvous mission is analyzed, with a survey of system requirements to accomplish molecular composition analysis of the asteroid. Based on positive theoretical results obtained during Phase I, the estimated TRL of the system is now TRL-2. This document also describes potential future research and experimentation that could push the system to TRL-4 within 2 years. Steps required for construction of a laboratory prototype are described. An experiment to test predictions of the theory is described, based on the laboratory prototype setup.

Vacuum Processing Technique for Development of Primary Standard Blackbodies

PubMed Central

Navarro, M.; Bruce, S. S.; Johnson, B. Carol; Murthy, A. V.; Saunders, R. D.

1999-01-01

Blackbody sources with nearly unity emittance that are in equilibrium with a pure freezing metal such as gold, silver, or copper are used as primary standard sources in the International Temperature Scale of 1990 (ITS-90). Recently, a facility using radio-frequency induction heating for melting and filling the blackbody crucible with the freeze metal under vacuum conditions was developed at the National Institute of Standards and Technology (NIST). The blackbody development under a vacuum environment eliminated the possibility of contamination of the freeze metal during the process. The induction heating, compared to a resistively heated convection oven, provided faster heating of crucible and resulted in shorter turn-around time of about 7 h to manufacture a blackbody. This paper describes the new facility and its application to the development of fixed-point blackbodies.

System Concept for Remote Measurement of Asteroid Molecular Composition

NASA Astrophysics Data System (ADS)

Hughes, G. B.; Lubin, P. M.; Zhang, Q.; Brashears, T.; Cohen, A. N.; Madajian, J.

2016-12-01

We propose a method for probing the molecular composition of cold solar system targets (asteroids, comets, planets, moons) from a distant vantage, such as from a spacecraft orbiting the object. A directed energy beam is focused on the target. With sufficient flux, the spot temperature rises rapidly, and evaporation of surface materials occurs. The melted spot creates a high-temperature blackbody source, and ejected material creates a plume of surface materials in front of the spot. Molecular and atomic absorption of the blackbody radiation occurs within the ejected plume. Bulk composition of the surface material is investigated by using a spectrometer to view the heated spot through the ejected material. Our proposed method differs from technologies such as Laser-Induced Breakdown Spectroscopy (LIBS), which atomizes and ionizes materials in the target; scattered ions emit characteristic radiation, and the LIBS detector performs atomic composition analysis by observing emission spectra. Standoff distance for LIBS is limited by the strength of characteristic emission, and distances greater than 10 m are problematic. Our proposed method detects atomic and molecular absorption spectra in the plume; standoff distance is limited by the size of heated spot, and the plume opacity; distances on the order of tens of kilometers are immediately feasible. Simulations have been developed for laser heating of a rocky target, with concomitant evaporation. Evaporation rates lead to determination of plume density and opacity. Absorption profiles for selected materials are estimated from plume properties. Initial simulations of absorption profiles with laser heating show great promise for molecular composition analysis from tens of kilometers distance. This paper explores the feasibility a hypothetical mission that seeks to perform surface molecular composition analysis of a near-earth asteroid while the craft orbits the asteroid. Such a system has compelling potential benefit for solar system exploration.

An Analysis of Recent Measurements of the Temperature of the Cosmic Microwave Background Radiation

DOE R&D Accomplishments Database

Smoot, G.; Levin, S. M.; Witebsky, C.; De Amici, G.; Rephaeli, Y.

1987-07-01

This paper presents an analysis of the results of recent temperature measurements of the cosmic microwave background radiation (CMBR). The observations for wavelengths longer than 0.1 cum are well fit by a blackbody spectrum at 2.74{+ or -}0.0w K; however, including the new data of Matsumoto et al. (1987) the result is no longer consistent with a Planckian spectrum. The data are described by a Thomson-distortion parameter u=0.021{+ or -}0.002 and temperature 2.823{+ or -}0.010 K at the 68% confidence level. Fitting the low-frequency data to a Bose-Einstein spectral distortion yields a 95% confidence level upper limit of 1.4 x 10{sup -2} on the chemical potential mu{sub 0}. These limits on spectral distortions place restrictions on a number of potentially interesting sources of energy release to the CMBR, including the hot intergalactic medium proposed as the source of the X-ray background.

A flat Universe from high-resolution maps of the cosmic microwave background radiation

PubMed

de Bernardis P; Ade; Bock; Bond; Borrill; Boscaleri; Coble; Crill; De Gasperis G; Farese; Ferreira; Ganga; Giacometti; Hivon; Hristov; Iacoangeli; Jaffe; Lange; Martinis; Masi; Mason; Mauskopf; Melchiorri; Miglio; Montroy; Netterfield

2000-04-27

The blackbody radiation left over from the Big Bang has been transformed by the expansion of the Universe into the nearly isotropic 2.73 K cosmic microwave background. Tiny inhomogeneities in the early Universe left their imprint on the microwave background in the form of small anisotropies in its temperature. These anisotropies contain information about basic cosmological parameters, particularly the total energy density and curvature of the Universe. Here we report the first images of resolved structure in the microwave background anisotropies over a significant part of the sky. Maps at four frequencies clearly distinguish the microwave background from foreground emission. We compute the angular power spectrum of the microwave background, and find a peak at Legendre multipole Ipeak = (197 +/- 6), with an amplitude delta T200 = (69 +/- 8) microK. This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe, as favoured by standard inflationary models.

The Heated Halo for Space-Based Blackbody Emissivity Measurement

NASA Astrophysics Data System (ADS)

Gero, P.; Taylor, J. K.; Best, F. A.; Revercomb, H. E.; Garcia, R. K.; Adler, D. P.; Ciganovich, N. N.; Knuteson, R. O.; Tobin, D. C.

2012-12-01

The accuracy of radiance measurements with space-based infrared spectrometers is contingent on the quality of the calibration subsystem, as well as knowledge of its uncertainty. Upcoming climate benchmark missions call for measurement uncertainties better than 0.1 K (k=3) in radiance temperature for the detection of spectral climate signatures. Blackbody cavities impart the most accurate calibration for spaceborne infrared sensors, provided that their temperature and emissivity is traceably determined on-orbit. The On-Orbit Absolute Radiance Standard (OARS) has been developed at the University of Wisconsin and has undergone further refinement under the NASA Instrument Incubator Program (IIP) to meet the stringent requirements of the next generation of infrared remote sensing instruments. It provides on-orbit determination of both traceable temperature and emissivity for calibration blackbodies. The Heated Halo is the component of the OARS that provides a robust and compact method to measure the spectral emissivity of a blackbody in situ. A carefully baffled thermal source is placed in front of a blackbody in an infrared spectrometer system, and the combined radiance of the blackbody and Heated Halo reflection is observed. Knowledge of key temperatures and the viewing geometry allow the blackbody cavity spectral emissivity to be calculated. We present the results from the Heated Halo methodology implemented with a new Absolute Radiance Interferometer (ARI), which is a prototype space-based infrared spectrometer designed for climate benchmarking. We show the evolution of the technical readiness level of this technology and we compare our findings to models and other experimental methods of emissivity determination.

Scaling studies of solar pumped lasers

NASA Astrophysics Data System (ADS)

Christiansen, W. H.; Chang, J.

1985-08-01

A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow.

Scaling studies of solar pumped lasers

NASA Technical Reports Server (NTRS)

Christiansen, W. H.; Chang, J.

1985-01-01

A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow.

The structure and spectrum of a colliding-cloud system and its possible relationship to QSOs

NASA Technical Reports Server (NTRS)

Daltabuit, E.; Macalpine, G. M.; Cox, D. P.

1978-01-01

A collision between two gas clouds with initial densities of approximately 10 million per cu cm, velocities of about 1000 km/s, and radii of approximately 1 pc is investigated quantitatively by coupling a calculation of the radiation spectrum resulting from the anticipated shock fronts with a computation for the conversion of this high-energy radiation into optical emission in adjacent photoionized regions. The detailed structure of the colliding clouds is discussed, and the effects of an ambient magnetic field are considered. The combined emission-line spectrum is presented along with continuum emission estimates for thermal, synchrotron, and very-high-energy bremsstrahlung mechanisms. It is shown that significant continua can be produced over the range from 300 microns to 3 keV, including a blackbody contribution from a high-density neutral region between the shock fronts, free-free and free-bound radiation from the cooling zones directly behind the shocks, and free-free, free-bound, and two-photon radiation from the photoionized regions immediately ahead of and behind the cooling zones. The theoretical spectrum of the structure resulting from the collision is found to be similar in general and in some details to those observed for typical quasars.

A comparison of absolute calibrations of a radiation thermometer based on a monochromator and a tunable source

NASA Astrophysics Data System (ADS)

Keawprasert, T.; Anhalt, K.; Taubert, D. R.; Sperling, A.; Schuster, M.; Nevas, S.

2013-09-01

An LP3 radiation thermometer was absolutely calibrated at a newly developed monochromator-based set-up and the TUneable Lasers in Photometry (TULIP) facility of PTB in the wavelength range from 400 nm to 1100 nm. At both facilities, the spectral radiation of the respective sources irradiates an integrating sphere, thus generating uniform radiance across its precision aperture. The spectral irradiance of the integrating sphere is determined via an effective area of a precision aperture and a Si trap detector, traceable to the primary cryogenic radiometer of PTB. Due to the limited output power from the monochromator, the absolute calibration was performed with the measurement uncertainty of 0.17 % (k = 1), while the respective uncertainty at the TULIP facility is 0.14 %. Calibration results obtained by the two facilities were compared in terms of spectral radiance responsivity, effective wavelength and integral responsivity. It was found that the measurement results in integral responsivity at the both facilities are in agreement within the expanded uncertainty (k = 2). To verify the calibration accuracy, the absolutely calibrated radiation thermometer was used to measure the thermodynamic freezing temperatures of the PTB gold fixed-point blackbody.

An application of statistical mechanics for representing equilibrium perimeter distributions of tropical convective clouds

NASA Astrophysics Data System (ADS)

Garrett, T. J.; Alva, S.; Glenn, I. B.; Krueger, S. K.

2015-12-01

There are two possible approaches for parameterizing sub-grid cloud dynamics in a coarser grid model. The most common is to use a fine scale model to explicitly resolve the mechanistic details of clouds to the best extent possible, and then to parameterize these behaviors cloud state for the coarser grid. A second is to invoke physical intuition and some very general theoretical principles from equilibrium statistical mechanics. This approach avoids any requirement to resolve time-dependent processes in order to arrive at a suitable solution. The second approach is widely used elsewhere in the atmospheric sciences: for example the Planck function for blackbody radiation is derived this way, where no mention is made of the complexities of modeling a large ensemble of time-dependent radiation-dipole interactions in order to obtain the "grid-scale" spectrum of thermal emission by the blackbody as a whole. We find that this statistical approach may be equally suitable for modeling convective clouds. Specifically, we make the physical argument that the dissipation of buoyant energy in convective clouds is done through mixing across a cloud perimeter. From thermodynamic reasoning, one might then anticipate that vertically stacked isentropic surfaces are characterized by a power law dlnN/dlnP = -1, where N(P) is the number clouds of perimeter P. In a Giga-LES simulation of convective clouds within a 100 km square domain we find that such a power law does appear to characterize simulated cloud perimeters along isentropes, provided a sufficient cloudy sample. The suggestion is that it may be possible to parameterize certain important aspects of cloud state without appealing to computationally expensive dynamic simulations.

The Next Generation Heated Halo for Blackbody Emissivity Measurement

NASA Astrophysics Data System (ADS)

Gero, P.; Taylor, J. K.; Best, F. A.; Revercomb, H. E.; Knuteson, R. O.; Tobin, D. C.; Adler, D. P.; Ciganovich, N. N.; Dutcher, S. T.; Garcia, R. K.

2011-12-01

The accuracy of radiance measurements from space-based infrared spectrometers is contingent on the quality of the calibration subsystem, as well as knowledge of its uncertainty. Future climate benchmarking missions call for measurement uncertainties better than 0.1 K (k=3) in radiance temperature for the detection of spectral climate signatures. Blackbody cavities impart the most accurate calibration for spaceborne infrared sensors, provided that their temperature and emissivity is traceably determined on-orbit. The On-Orbit Absolute Radiance Standard (OARS) has been developed at the University of Wisconsin to meet the stringent requirements of the next generation of infrared remote sensing instruments. It provides on-orbit determination of both traceable temperature and emissivity for calibration blackbodies. The Heated Halo is the component of the OARS that provides a robust and compact method to measure the spectral emissivity of a blackbody in situ. A carefully baffled thermal source is placed in front of a blackbody in an infrared spectrometer system, and the combined radiance of the blackbody and Heated Halo reflection is observed. Knowledge of key temperatures and the viewing geometry allow the blackbody cavity spectral emissivity to be calculated. We present the results from the Heated Halo methodology implemented with a new Absolute Radiance Interferometer (ARI), which is a prototype space-based infrared spectrometer designed for climate benchmarking that was developed under the NASA Instrument Incubator Program (IIP). We compare our findings to models and other experimental methods of emissivity determination.

Interaction of surface plasmon polaritons in heavily doped GaN microstructures with terahertz radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melentev, G. A., E-mail: gamelen@spbstu.ru; Shalygin, V. A.; Vorobjev, L. E.

2016-03-07

We present the results of experimental and theoretical studies of the surface plasmon polariton excitations in heavily doped GaN epitaxial layers. Reflection and emission of radiation in the frequency range of 2–20 THz including the Reststrahlen band were investigated for samples with grating etched on the sample surface, as well as for samples with flat surface. The reflectivity spectrum for p-polarized radiation measured for the sample with the surface-relief grating demonstrates a set of resonances associated with excitations of different surface plasmon polariton modes. Spectral peculiarities due to the diffraction effect have been also revealed. The characteristic features of themore » reflectivity spectrum, namely, frequencies, amplitudes, and widths of the resonance dips, are well described theoretically by a modified technique of rigorous coupled-wave analysis of Maxwell equations. The emissivity spectra of the samples were measured under epilayer temperature modulation by pulsed electric field. The emissivity spectrum of the sample with surface-relief grating shows emission peaks in the frequency ranges corresponding to the decay of the surface plasmon polariton modes. Theoretical analysis based on the blackbody-like radiation theory well describes the main peculiarities of the observed THz emission.« less

Lifecycle of laser-produced air sparks

DOE PAGES

Harilal, S. S.; Brumfield, B. E.; Phillips, M. C.

2015-06-03

Here, we investigated the lifecycle of laser-generated air sparks or plasmas using multiple plasma diagnostic tools. The sparks were generated by focusing the fundamental radiation from an Nd:YAG laser in air, and studies included early and late time spark dynamics, decoupling of the shock wave from the plasma core, emission from the spark kernel, cold gas excitation by UV radiation, shock waves produced by the air spark, and the spark's final decay and turbulence formation. The shadowgraphic and self-emission images showed similar spark morphology at earlier and late times of its lifecycle; however, significant differences are seen in the midlifemore » images. Spectroscopic studies in the visible region showed intense blackbody-type radiation at early times followed by clearly resolved ionic, atomic, and molecular emission. The detected spectrum at late times clearly contained emission from both CN and N 2 +. Additional spectral features have been identified at late times due to emission from O and N atoms, indicating some degree of molecular dissociation and excitation. Detailed spatially and temporally resolved emission analysis provides insight about various physical mechanisms leading to molecular and atomic emission by air sparks, including spark plasma excitation, heating of cold air by UV radiation emitted by the spark, and shock-heating.« less

Fire detection behind a wall by using microwave techniques

NASA Astrophysics Data System (ADS)

Alkurt, Fatih Özkan; Baǧmancı, Mehmet; Karaaslan, Muharrem; Bakır, Mehmet; Altıntaş, Olcay; Karadaǧ, Faruk; Akgöl, Oǧuzhan; Ünal, Emin

2018-02-01

In this work, detection of the fire location behind a wall by using microwave techniques is illustrated. According to Planck's Law, Blackbody emits electromagnetic radiation in the microwave region of the electromagnetic spectrum. This emitted waves penetrates all materials except that metals. These radiated waves can be detected by using directional and high gain antennas. The proposed antenna consists of a simple microstrip patch antenna and a 2×2 microstrip patch antenna array. FIT based simulation results show that 2×2 array antenna can absorb emitted power from a fire source which is located behind a wall. This contribution can be inspirational for further works.

Fundamental studies in X-ray astrophysics

NASA Technical Reports Server (NTRS)

Lamb, D. Q.; Lightman, A. P.

1982-01-01

An analytical model calculation of the ionization structure of matter accreting onto a degenerate dwarf was carried out. Self-consistent values of the various parameters are used. The possibility of nuclear burning of the accreting matter is included. We find the blackbody radiation emitted from the stellar surface keeps hydrogen and helium ionized out to distances much larger than a typical binary separation. Except for low mass stars or high accretion rates, the assumption of complete ionization of the elements heavier than helium is a good first approximation. For low mass stars or high accretion rates the validity of assuming complete ionization depends sensitivity on the distribution of matter in the binary system.

Fine Structure of Dark Energy and New Physics

DOE PAGES

Jejjala, Vishnu; Kavic, Michael; Minic, Djordje

2007-01-01

Following our recent work on the cosmological constant problem, in this letter we make a specific proposal regarding the fine structure (i.e., the spectrum) of dark energy. The proposal is motivated by a deep analogy between the blackbody radiation problem, which led to the development of quantum theory, and the cosmological constant problem, for which we have recently argued calls for a conceptual extension of the quantum theory. We argue that the fine structure of dark energy is governed by a Wien distribution, indicating its dual quantum and classical nature. We discuss observational consequences of such a picture of darkmore » energy and constrain the distribution function.« less

Airborne lidar/radiometric measurements of cirrus cloud parameters and their application to LOWTRAN radiance evaluations

NASA Technical Reports Server (NTRS)

Uthe, Edward E.

1990-01-01

SRI has assembled an airborne lidar/radiometric instrumentation suite for mapping cirrus cloud distribution and analyzing cirrus cloud optical properties. Operation of upward viewing infrared radiometers from an airborne platform provides the optimum method of measuring high altitude cold cloud radiative properties with minimum interference from the thermal emission by the earth's surface and lower atmospheric components. Airborne installed sensors can also operate over large regional areas including water, urban, and mountain surfaces and above lower atmospheric convective clouds and haze layers. Currently available sensors installed on the SRI Queen Air aircraft are illustrated. Lidar and radiometric data records are processed for real time viewing on a color video screen. A cirrus cloud data example is presented as a black and white reproduction of a color display of data at the aircraft altitude of 12,000 ft, the 8 to 14 micron atmospheric radiation background was equivalent to a blackbody temperature of about -60 C and, therefore, the radiometer did not respond strongly to low density cirrus cloud concentrations detected by the lidar. Cloud blackbody temperatures (observed by radiometer) are shown plotted against midcloud temperatures (derived from lidar observed cloud heights and supporting temperature profiles) for data collected on 30 June and 28 July.

Photothermal effects during nanodiamond synthesis from a carbon aerogel in a laser-heated diamond anvil cell

DOE PAGES

Crane, Matthew J.; Smith, Bennett E.; Meisenheimer, Peter B.; ...

2018-05-17

Nanodiamonds have emerged as promising materials for quantum computing, biolabeling, and sensing due to their ability to host color centers with remarkable photostability and long spin-coherence times at room temperature. Recently, a bottom-up, high-pressure, high-temperature (HPHT) approach was demonstrated for growing nanodiamonds with color centers from amorphous carbon precursors in a laser-heated diamond anvil cell (LH-DAC) that was supported by a near-hydrostatic noble gas pressure medium. However, a detailed understanding of the photothermal heating and its effect on diamond growth, including the phase conversion conditions and the temperature-dependence of color center formation, has not been reported. In this work, wemore » measure blackbody radiation during LH-DAC synthesis of nanodiamond from carbon aerogel to examine these temperature-dependent effects. Blackbody temperature measurements suggest that nanodiamond growth can occur at 16.3 GPa and 1800 K. We use Mie theory and analytical heat transport to develop a predictive photothermal heating model. This model demonstrates that melting the noble gas pressure medium during laser heating decreases the local thermal conductivity to drive a high spatial resolution of phase conversion to diamond. In conclusion, we observe a temperature-dependent formation of nitrogen vacancy centers and interpret this phenomenon in the context of HPHT carbon vacancy diffusion.« less

Photothermal effects during nanodiamond synthesis from a carbon aerogel in a laser-heated diamond anvil cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crane, Matthew J.; Smith, Bennett E.; Meisenheimer, Peter B.

Nanodiamonds have emerged as promising materials for quantum computing, biolabeling, and sensing due to their ability to host color centers with remarkable photostability and long spin-coherence times at room temperature. Recently, a bottom-up, high-pressure, high-temperature (HPHT) approach was demonstrated for growing nanodiamonds with color centers from amorphous carbon precursors in a laser-heated diamond anvil cell (LH-DAC) that was supported by a near-hydrostatic noble gas pressure medium. However, a detailed understanding of the photothermal heating and its effect on diamond growth, including the phase conversion conditions and the temperature-dependence of color center formation, has not been reported. In this work, wemore » measure blackbody radiation during LH-DAC synthesis of nanodiamond from carbon aerogel to examine these temperature-dependent effects. Blackbody temperature measurements suggest that nanodiamond growth can occur at 16.3 GPa and 1800 K. We use Mie theory and analytical heat transport to develop a predictive photothermal heating model. This model demonstrates that melting the noble gas pressure medium during laser heating decreases the local thermal conductivity to drive a high spatial resolution of phase conversion to diamond. In conclusion, we observe a temperature-dependent formation of nitrogen vacancy centers and interpret this phenomenon in the context of HPHT carbon vacancy diffusion.« less

Design and analysis on fume exhaust system of blackbody cavity sensor for continuously measuring molten steel temperature

NASA Astrophysics Data System (ADS)

Mei, Guohui; Zhang, Jiu; Zhao, Shumao; Xie, Zhi

2017-03-01

Fume exhaust system is the main component of the novel blackbody cavity sensor with a single layer tube, which removes the fume by gas flow along the exhaust pipe to keep the light path clean. However, the gas flow may break the conditions of blackbody cavity and results in the poor measurement accuracy. In this paper, we analyzed the influence of the gas flow on the temperature distribution of the measuring cavity, and then calculated the integrated effective emissivity of the non-isothermal cavity based on Monte-Carlo method, accordingly evaluated the sensor measurement accuracy, finally obtained the maximum allowable flow rate for various length of the exhaust pipe to meet the measurement accuracy. These results will help optimize the novel blackbody cavity sensor design and use it better for measuring the temperature of molten steel.

Models for X-Ray Emission from Isolated Pulsars

NASA Technical Reports Server (NTRS)

Wang, F. Y.-H.; Ruderman, M.; Halpern, Jules P.; Zhu, T.; Oliversen, Ronald (Technical Monitor)

2001-01-01

A model is proposed for the observed combination of power-law and thermal X-rays from rotationally powered pulsars. For gamma-ray pulsars with accelerators very many stellar radii above the neutron star surface, 100 MeV curvature gamma-rays from e(-) or e(+) flowing starward out of such accelerators are converted to e1 pairs on closed field lines all around the star. These pairs strongly affect X-ray emission from near the star in two ways. (1) The pairs are a source of synchrotron emission immediately following their creation in regions where B approx. 10(exp 10) G. This emission, in the photon energy range 0.1 keV less than E(sub X) less than 5 MeV, has a power-law spectrum with energy index 0.5 and X-ray luminosity that depends on the back-flow current, and is typically approx. 10(exp 33) ergs/ s. (2) The pairs ultimately a cyclotron resonance "blanket" surrounding the star except for two holes along the open field line bundles which pass through it. In such a blanket the gravitational pull on e(+,-) pairs toward the star is balanced by the hugely amplified push of outflowing surface emitted X-rays wherever cyclotron resonance occurs. Because of it the neutron star is surrounded by a leaky "hohlraum" of hot blackbody radiation with two small holes, which prevents direct X-ray observation of a heated polar cap of a gamma-ray pulsar. Weakly spin modulated radiation from the blanket together with more strongly spin-modulated radiation from the holes through it would then dominate observed low energy (0.1-10 keV) emission. For non-y-ray pulsars, in which no such accelerators with their accompanying extreme relativistic back-flow toward the star are expected, optically thick e1 resonance blankets should not form (except in special cases very close to the open field line bundle). From such pulsars blackbody radiation from both the warm stellar surface and the heated polar caps should be directly observable. In these pulsars, details of the surface magnetic field evolution, especially of polar cap areas, become relevant to observations. The models are compared to X-ray data from Geminga, PSR 1055-52, PSR 0656+14, PSR 1929+10, and PSR 0950+08.

Emissivity correction for interpreting thermal radiation from a terrestrial surface

NASA Technical Reports Server (NTRS)

Sutherland, R. A.; Bartholic, J. F.; Gerber, J. F.

1979-01-01

A general method of accounting for emissivity in making temperature determinations of graybody surfaces from radiometric data is presented. The method differs from previous treatments in that a simple blackbody calibration and graphical approach is used rather than numerical integrations which require detailed knowledge of an instrument's spectral characteristics. Also, errors caused by approximating instrumental response with the Stephan-Boltzman law rather than with an appropriately weighted Planck integral are examined. In the 8-14 micron wavelength interval, it is shown that errors are at most on the order of 3 C for the extremes of the earth's temperature and emissivity. For more practical limits, however, errors are less than 0.5 C.

Characterization of the 300 K and 700 K Calibration Sources for Space Application with the Bepicolombo Mission to Mercury

NASA Astrophysics Data System (ADS)

Gutschwager, B.; Driescher, H.; Herrmann, J.; Hirsch, H.; Hollandt, J.; Jahn, H.; Kuchling, P.; Monte, C.; Scheiding, M.

2011-08-01

The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) onboard the European-Japanese space mission BepiColombo to Mercury will be launched in 2014. The MERTIS scientific objective is to identify rock-forming minerals and measure surface temperatures by infrared spectroscopy (7 μm to 14 μm) and spectrally unresolved infrared radiometry (7 μm to 40 μm). To achieve this goal, MERTIS utilizes two onboard infrared calibration sources, the MERTIS blackbody at 700 K (MBB7) and the MERTIS blackbody at 300 K (MBB3), together with deep space observations corresponding to 3 K. All three sources can be observed one after the other using a rotating mirror system. The leaders of the project MERTIS are the Westfälische University of Münster, institute for planetary investigation, Mr. Prof. Dr. H. Hiesinger (PI) and the DLR, Institute of Planetary Research Berlin-Adlershof, Mr. Dr. J. Helbert (CoPI). Both blackbody radiators have to fulfill the severe mass, volume, and power restrictions of MERTIS. The radiating area of the MBB3 is based on a structured surface with a high-emissivity space qualified coating. The relatively high emissivity of the coating was further enhanced by a pyramidal surface structure to values over 0.99 in the wavelength range from 5 μm to 10 μm and over 0.95 in the wavelength range from 10 μm to 30 μm. The MBB7 is based on a small commercially available surface emitter in a standard housing. The windowless emitter is an electrically heated resistor, which consists of a platinum structure with a blackened surface on a ceramic body. The radiation of the emitter is expanded and collimated through use of a parabolic mirror. The design requirements and the radiometric and thermometric characterization of these two blackbodies are described in this paper.

Selected highly charged ions as prospective candidates for optical clocks with quality factors larger than 1015

NASA Astrophysics Data System (ADS)

Yu, Yan-mei; Sahoo, B. K.

2018-04-01

The Ni12 +, Cu13 +, Pd12 +, and Ag13 + highly charged ions (HCIs) are proposed for making very accurate optical clocks with the fractional uncertainties below 10-19 level. These HCIs have simple atomic energy levels, clock transitions with quality factors larger than 1015, and optical magnetic-dipole (M 1 ) transitions that can be used for laser cooling and detecting quantum jumps on the clock transitions by the shelving method. To demonstrate the projected fractional uncertainties, we estimate orders of magnitude of the Zeeman, Stark, blackbody radiation, and electric quadrupole shifts of the clock transitions by performing calculations of the relevant atomic properties in the above HCIs.

Measuring Earth's radiation imbalance with RAVAN: A CubeSat mission to measure the driver of global climate change

NASA Astrophysics Data System (ADS)

Swartz, W. H.; Dyrud, L. P.; Wiscombe, W. J.; Lorentz, S. R.; Papadakis, S.; Summers, R. A.; Smith, A. W.; Wu, D. L.; Deglau, D. M.; Arnold, S. P.

2013-12-01

The Earth radiation imbalance (ERI) is the single most important quantity for predicting the course of climate change over the next century. It is also the single most important metric for any geo-engineering scheme. We review the current scientific understanding of ERI and present a recently funded CubeSat mission, the Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN), that will demonstrate an affordable, accurate radiometer that directly measures Earth-leaving fluxes of total and solar-reflected radiation. Coupled with knowledge of the incoming radiation from the Sun, RAVAN directly gives ERI. The objective of RAVAN is to demonstrate that a compact spaceborne radiometer that is absolutely accurate to NIST-traceable standards can be built for low cost. The key technologies that enable a radiometer with all these attributes are: a gallium fixed-point blackbody as a built-in calibration source and a vertically aligned carbon nanotube (VACNT) absorber. VACNTs are the blackest known substance, making them ideal radiometer absorbers with order-of-magnitude improvements in spectral flatness and stability over the existing art. The Johns Hopkins University Applied Physics Laboratory heritage 3U Multi-Mission Nanosat will host RAVAN, providing the reliability, agility, and resources needed. RAVAN will pave the way for a constellation Earth radiation budget mission that can provide the measurements needed to enable vastly superior predictions of future climate change.

Sensitivity of blackbody effective emissivity to wavelength and temperature: By genetic algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ejigu, E. K.; Liedberg, H. G.

A variable-temperature blackbody (VTBB) is used to calibrate an infrared radiation thermometer (pyrometer). The effective emissivity (ε{sub eff}) of a VTBB is dependent on temperature and wavelength other than the geometry of the VTBB. In the calibration process the effective emissivity is often assumed to be constant within the wavelength and temperature range. There are practical situations where the sensitivity of the effective emissivity needs to be known and correction has to be applied. We present a method using a genetic algorithm to investigate the sensitivity of the effective emissivity to wavelength and temperature variation. Two matlab® programs are generated:more » the first to model the radiance temperature calculation and the second to connect the model to the genetic algorithm optimization toolbox. The effective emissivity parameter is taken as a chromosome and optimized at each wavelength and temperature point. The difference between the contact temperature (reading from a platinum resistance thermometer or liquid in glass thermometer) and radiance temperature (calculated from the ε{sub eff} values) is used as an objective function where merit values are calculated and best fit ε{sub eff} values selected. The best fit ε{sub eff} values obtained as a solution show how sensitive they are to temperature and wavelength parameter variation. Uncertainty components that arise from wavelength and temperature variation are determined based on the sensitivity analysis. Numerical examples are considered for illustration.« less

Lifecycle of laser-produced air sparks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harilal, S. S., E-mail: hari@pnnl.gov; Brumfield, B. E.; Phillips, M. C.

2015-06-15

We investigated the lifecycle of laser-generated air sparks or plasmas using multiple plasma diagnostic tools. The sparks were generated by focusing the fundamental radiation from an Nd:YAG laser in air, and studies included early and late time spark dynamics, decoupling of the shock wave from the plasma core, emission from the spark kernel, cold gas excitation by UV radiation, shock waves produced by the air spark, and the spark's final decay and turbulence formation. The shadowgraphic and self-emission images showed similar spark morphology at earlier and late times of its lifecycle; however, significant differences are seen in the midlife images.more » Spectroscopic studies in the visible region showed intense blackbody-type radiation at early times followed by clearly resolved ionic, atomic, and molecular emission. The detected spectrum at late times clearly contained emission from both CN and N{sub 2}{sup +}. Additional spectral features have been identified at late times due to emission from O and N atoms, indicating some degree of molecular dissociation and excitation. Detailed spatially and temporally resolved emission analysis provides insight about various physical mechanisms leading to molecular and atomic emission by air sparks, including spark plasma excitation, heating of cold air by UV radiation emitted by the spark, and shock-heating.« less

A Blackbody Is Not a Blackbox

ERIC Educational Resources Information Center

Smerlak, Matteo

2011-01-01

We discuss carefully the "blackbody approximation", stressing what it is (a limit case of radiative transfer), and what it is not (the assumption that the body is perfectly absorbing, namely "black"). Furthermore, we derive the Planck spectrum without enclosing the field in a box, as is done in most textbooks. Although convenient, this trick…

Stainless steel/tin/glass coating as spectrally selective material for passive radiative cooling applications

NASA Astrophysics Data System (ADS)

Mouhib, T.; Mouhsen, A.; Oualim, E. M.; Harmouchi, M.; Vigneron, J. P.; Defrance, P.

2009-02-01

Glass substrates coated with a stainless steel-tin double layer were prepared in order to achieve the inverse greenhouse effect. The measurements of the optical properties of the samples indicate that the needed specific spectral selectivity is available. Practical tests of radiative cooling were performed during clear night using a blackbody radiator covered by the coated plate with glass facing the sky. The blackbody temperature was observed to be 6.0 °C below that of the ambient, and the cooling power was estimated to be 27.9 W/m 2. Diurnal measurements indicated that cooling of the blackbody radiator is achieved except for approximately 6 hours around noon.

Radiometric observations of the 752.033-GHz rotational absorption line of H2O from a laboratory jet. [simulation of rocket plumes

NASA Technical Reports Server (NTRS)

Dionne, G. F.; Fitzgerald, J. F.; Chang, T.-S.; Fetterman, H. R.; Litvak, M. M.

1980-01-01

With the aid of a high-resolution two-stage heterodyne radiometer, spectral absorption measurements of the 752.033 GHz line of water vapor were carried out, using a blackbody continuum as a background radiation source for investigating the absorptive properties of the H2O content of high altitude rocket plumes. To simulate this physical situation in a laboratory environment, a small steam jet was operated within a large high-vacuum chamber, with the H2O jet plume traversing the radiometer line of sight. The experiments verified that this rotational line is optically thick, with excitation temperatures below 100 K, in the downstream part of the plume, as predicted by theoretical modelling.

Quantum key distribution over a 72 dB channel loss using ultralow dark count superconducting single-photon detectors.

PubMed

Shibata, Hiroyuki; Honjo, Toshimori; Shimizu, Kaoru

2014-09-01

We report the first quantum key distribution (QKD) experiment over a 72 dB channel loss using superconducting nanowire single-photon detectors (SSPD, SNSPD) with the dark count rate (DCR) of 0.01 cps. The DCR of the SSPD, which is dominated by the blackbody radiation at room temperature, is blocked by introducing cold optical bandpass filter. We employ the differential phase shift QKD (DPS-QKD) scheme with a 1 GHz system clock rate. The quantum bit error rate (QBER) below 3% is achieved when the length of the dispersion shifted fiber (DSF) is 336 km (72 dB loss), which is low enough to generate secure keys.

Rare Earth Doped High Temperature Ceramic Selective Emitters

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Pal, AnnaMarie; Patton, Martin O.; Jenkins, Phillip P.

1999-01-01

As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study develops a spectral emittance model for films of rare earth containing materials. Although there are several possible rare earth doped high temperature materials, this study was confined to rare earth aluminum garnets. Good agreement between experimental and theoretical spectral emittances was found for erbium, thulium and erbium-holmium aluminum garnets. Spectral emittances of these films are sensitive to temperature differences across the film. Emitter efficiency is also a sensitive function of temperature. For thulium aluminum garnet the efficiency is 0.38 at 1700 K but only 0.19 at 1262 K.

Construction and performance of a high-temperature-superconductor composite bolometer

NASA Technical Reports Server (NTRS)

Brasunas, J. C.; Moseley, S. H.; Lakew, B.; Ono, R. H.; Mcdonald, D. G.

1989-01-01

A high-Tc superconducting bolometer has been constructed using a YBa2Cu3O(x) thin-film meander line 20 microns wide and 76,000 microns long, deposited on a SrTiO3 substrate. Radiation is absorbed by a thin film of Bi with well-characterized absorption properties deposited on a Si substrate in contact with the SrTiO3. At 1.8 Hz the measured bolometer response to a 500-K blackbody is 5.2 V/W (820 V/W extrapolated to dc). The impact of apparent nonohmic behavior at the transition is discussed, as are ways of reducing the observed 1/f noise. The response time is 32 s and is dominated by the heat capacity of the SrTiO3 substrate.

Using VISAR to assess the M-band isotropy in hohlraums

DOE PAGES

Lanier, Nicholas Edward; Kline, John L.; Morton, John

2016-09-27

In laser based radiation flow experiments, drive variability can often overwhelm the physics sensitivity that one seeks to quantify. Hohlraums can help by providing a more symmetrized, Planckian-like source. However, at higher temperatures, the hohlraum’s actual emission can deviate significantly from a truly blackbody, Lambertian source. At the National Ignition Facility (NIF), Dante provides the best quantification of hohlraum output. Unfortunately, limited diagnostic access coupled with NIF’s natural symmetry does not allow for Dante measurements at more than two angles. As part of the CEPHEUS campaign on NIF, proof-of-principle experiments to better quantify the gold M-band isotropy were conducted. Thesemore » experiments positioned beryllium/aluminum mirrors at differing angles, offset from the hohlraum. Filtering removes the thermal emission of the hohlraum and the remaining M-band radiation is preferentially absorbed in the aluminum layer. The subsequent hydrodynamic motion is measured via VISAR. Although indirect, this M-band measurement can be made at any angle.« less

Helium emission from model flare layers. [of outer solar atmosphere

NASA Technical Reports Server (NTRS)

Kulander, J. I.

1976-01-01

The emission of visible and UV He I and He II line radiation from a plane-parallel model flare layer characterized by electron temperatures of 10,000 to 50,000 K and electron densities of 10 to the 10th power to 10 to the 15th power per cu cm is analyzed by solving the statistical-equilibrium equations for a 30-level He I-II-III system, using parametric representations of the line and continuum radiation fields. The atomic model was chosen to provide accurate solutions for the first two resonance lines of He I and He II as well as for the D3 and 10,830-A lines of He I. Reaction rates are discussed, and sample solutions to the steady-state population equations are given for a generally optically thin gas assumed to be irradiated over 2pi sr by a blackbody spectrum at 6000 K. Specific results are examined for ionization equilibrium, level populations, approximate optical depths of a 1000-km-thick flare layer, line intensities, and upper-level population rates.

Surface temperature of a magnetized neutron star and interpretation of the ROSAT data. 1: Dipole fields

NASA Technical Reports Server (NTRS)

Page, Dany

1995-01-01

We model the temperature distribution at the surface of a magnetized neutron star and study the effects on the observed X-ray spectra and light curves. Generalrelativistic effects, i.e., redshift and lensing, are fully taken into account. Atmospheric effects on the emitted spectral flux are not included: we consider only blackbody emission at the local effective temperature. In this first paper we restrict ourselves to dipole fields. General features are studied and compared with the ROSAT data from the pulsars 0833 - 45 (Vela), 0656 + 14, 0630 + 178 (Geminga), and 1055 - 52, the four cases for which there is strong evidence that thermal radiation from the stellar surface is detected. The composite spectra we obtain are not very different from a blackbody spectrum at the star's effective temperature. We conclude that, as far as blackbody spectra are considered, temperature estimates using single-temperature models give results practically identical to our composite models. The change of the (composite blackbody) spectrum with the star's rotational phase is also not very large and may be unobservable inmost cases. Gravitational lensing strongly suppresses the light curve pulsations. If a dipole field is assumed, pulsed fractions comparable to the observed ones can be obtained only with stellar radii larger than those which are predicted by current models of neutron star struture, or with low stellar masses. Moreover, the shapes of the theoretical light curves with dipole fields do not correspond to the observations. The use of magnetic spectra may raise the pulsed fraction sufficiently but will certainly make the discrepancy with the light curve shapes worse: dipole fields are not sufficient to interpret the data. Many neutron star models with a meson condensate or hypersons predict very small radii, and hence very strong lensing, which will require highly nondipolar fields to be able to reproduce the observed pulsed fractions, if possible at all: this may be a new tool to constrain the size of neutron stars. The pulsed fractions obtained in all our models increase with photon energy: the strong decrease observed in Geminga at energies 0.3-0.5 keV is definitely a genuine effect of the magnetic field on the spectrum in contradistinction to the magnetic effects on the surface temperature considered her. Thus, a detailed analysis of thermal emission from the four pulsars we consider will require both complex surface field configurations and the inclusion of magnetic effects in the atmosphere (i.e., on the emitted spectrum).

The rank correlated SLW model of gas radiation in non-uniform media

NASA Astrophysics Data System (ADS)

Solovjov, Vladimir P.; Andre, Frederic; Lemonnier, Denis; Webb, Brent W.

2017-08-01

A comprehensive theoretical development of possible reference approaches in modelling of radiation transfer in non-uniform gaseous media is developed within the framework of the Generalized SLW Model. The notion of absorption spectrum ;correlation; adopted currently for global methods in gas radiation is critically revisited and replaced by a less restrictive concept of rank correlated spectrum. Within this framework it is shown that eight different reference approaches are possible, of which only three have been reported in the literature. Among the approaches presented is a novel Rank Correlated SLW Model, which is distinguished by the fact that i) it does not require the specification of a reference gas thermodynamic state, and ii) it preserves the emission term in the spectrally integrated Radiative Transfer Equation. Construction of this reference model requires only two absorption line blackbody distribution functions, and subdivision into gray gases can be performed using standard quadratures. Consequently, this new reference approach appears to have significant advantages over all other methods, and is, in general, a significant improvement in the global modelling of gas radiation. All reference approaches are summarized in the present work, and their use in radiative transfer prediction is demonstrated for simple example cases. Further, a detailed rigorous theoretical development of the improved methods is provided.

Radiation Entropy and Near-Field Thermophotovoltaics

NASA Astrophysics Data System (ADS)

Zhang, Zhuomin M.

2008-08-01

Radiation entropy was key to the original derivation of Planck's law of blackbody radiation, in 1900. This discovery opened the door to quantum mechanical theory and Planck was awarded the Nobel Prize in Physics in 1918. Thermal radiation plays an important role in incandescent lamps, solar energy utilization, temperature measurements, materials processing, remote sensing for astronomy and space exploration, combustion and furnace design, food processing, cryogenic engineering, as well as numerous agricultural, health, and military applications. While Planck's law has been fruitfully applied to a large number of engineering problems for over 100 years, questions have been raised about its limitation in micro/nano systems, especially at subwavelength distances or in the near field. When two objects are located closer than the characteristic wavelength, wave interference and photon tunneling occurs that can result in significant enhancement of the radiative transfer. Recent studies have shown that the near-field effects can realize emerging technologies, such as superlens, sub-wavelength light source, polariton-assisted nanolithography, thermophotovoltaic (TPV) systems, scanning tunneling thermal microscopy, etc. The concept of entropy has also been applied to explain laser cooling of solids as well as the second law efficiency of devices that utilize thermal radiation to produce electricity. However, little is known as regards the nature of entropy in near-field radiation. Some history and recent advances are reviewed in this presentation with a call for research of radiation entropy in the near field, due to the important applications in the optimization of thermophotovoltaic converters and in the design of practical systems that can harvest photon energies efficiently.

The GOES-R Advanced Baseline Imager: detector spectral response effects on thermal emissive band calibration

NASA Astrophysics Data System (ADS)

Pearlman, Aaron J.; Padula, Francis; Cao, Changyong; Wu, Xiangqian

2015-10-01

The Advanced Baseline Imager (ABI) will be aboard the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite R-Series (GOES-R) to supply data needed for operational weather forecasts and long-term climate variability studies, which depend on high quality data. Unlike the heritage operational GOES systems that have two or four detectors per band, ABI has hundreds of detectors per channel requiring calibration coefficients for each one. This increase in number of detectors poses new challenges for next generation sensors as each detector has a unique spectral response function (SRF) even though only one averaged SRF per band is used operationally to calibrate each detector. This simplified processing increases computational efficiency. Using measured system-level SRF data from pre-launch testing, we have the opportunity to characterize the calibration impact using measured SRFs, both per detector and as an average of detector-level SRFs similar to the operational version. We calculated the spectral response impacts for the thermal emissive bands (TEB) theoretically, by simulating the ABI response viewing an ideal blackbody and practically, with the measured ABI response to an external reference blackbody from the pre-launch TEB calibration test. The impacts from the practical case match the theoretical results using an ideal blackbody. The observed brightness temperature trends show structure across the array with magnitudes as large as 0.1 K for and 12 (9.61 µm), and 0.25 K for band 14 (11.2 µm) for a 300 K blackbody. The trends in the raw ABI signal viewing the blackbody support the spectral response measurements results, since they show similar trends in bands 12 (9.61µm), and 14 (11.2 µm), meaning that the spectral effects dominate the response differences between detectors for these bands. We further validated these effects using the radiometric bias calculated between calibrations using the external blackbody and another blackbody, the ABI on-board calibrator. Using the detector-level SRFs reduces the structure across the arrays but leaves some residual bias. Further understanding of this bias could lead to refinements of the blackbody thermal model. This work shows the calibration impacts of using an average SRF across many detectors instead of accounting for each detector SRF independently in the TEB calibration. Note that these impacts neglect effects from the spectral sampling of Earth scene radiances that include atmospheric effects, which may further contribute to artifacts post-launch and cannot be mitigated by processing with detector-level SRFs. This study enhances the ability to diagnose anomalies on-orbit and reduce calibration uncertainty for improved system performance.

A Third Generation Water Bath Based Blackbody Source

PubMed Central

Fowler, Joel B.

1995-01-01

A third generation water bath based black-body source has been designed and constructed in the Radiometric Physics Division at the National Institute of Standards and Technology, Gaithersburg, MD. The goal of this work was to design a large aperture blackbody source with improved temporal stability and reproducibility compared with earlier designs, as well as improved ease of use. These blackbody sources operate in the 278 K to 353 K range with water temperature combined standard uncertainties of 3.5 mK to 7.8 mK. The calculated emissivity of these sources is 0.9997 with a relative standard uncertainty of 0.0003. With a 50 mm limiting aperture at the cavity; entrance, the emissivity increases to 0.99997. PMID:29151763

Bolometric kinetic inductance detector technology for sub-millimeter radiometric imaging

NASA Astrophysics Data System (ADS)

Hassel, Juha; Timofeev, Andrey V.; Vesterinen, Visa; Sipola, Hannu; Helistö, Panu; Aikio, Mika; Mäyrä, Aki; Grönberg, Leif; Luukanen, Arttu

2015-10-01

Radiometric sub-millimeter imaging is a candidate technology especially in security screening applications utilizing the property of radiation in the band of 0.2 - 1.0 THz to penetrate through dielectric substances such as clothing. The challenge of the passive technology is the fact that the irradiance corresponding to the blackbody radiation is very weak in this spectral band: about two orders of magnitude below that of the infrared band. Therefore the role of the detector technology is of ultimate importance to achieve sufficient sensitivity. In this paper we present results related to our technology relying on superconducting kinetic inductance detectors operating in a thermal (bolometric) mode. The detector technology is motivated by the fact that it is naturally suitable for scalable multiplexed readout systems, and operates with relatively simple cryogenics. We will review the basic concepts of the detectors, and provide experimental figures of merit. Furthermore, we will discuss the issues related to the scale-up of our detector technology into large 2D focal plane arrays.

Temperatures of shock-induced shear instabilities and their relationship to fusion curves. [emission from glass

NASA Technical Reports Server (NTRS)

Schmitt, D. R.; Ahrens, T. J.

1983-01-01

New emission spectra for MgO and CaAl2Si2O8 (glass) are observed from 430 to 820 nm. Taken with previous data, it is suggested that transparent solids display three regimes of light emission upon shock compression to successively higher pressures: (1) characteristic radiation such as observed in MgO and previously in other minerals, (2) heterogeneous hot spot (greybody) radiation observed in CaAl2Si2O8 and previously in all transparent solids undergoing shock-induced phase transformations, and (3) blackbody emission observed in the high pressure phase regime in NaCl, SiO2, CaO, CaAl2Si2O8, and Mg2SiO4. The onset of the second regime may delineate the onset of shock-induced polymorphism whereas the onset of the third regime delineates the Hugoniot pressure required to achieve local thermal equilibrium in the shocked solid. It is also proposed that the hot spot temperatures and corresponding shock pressures determined in the second regime delineate points on the fusion curves of the high pressure phase.

Tiros IV Radiation Data Catalog and Users' Manual

NASA Technical Reports Server (NTRS)

Kunde, V. G.

1963-01-01

The TIROS IV Meteorological Satellite contains a medium resolution scanning radiometer. Two of the channels of this instrument are sensitive to reflected solar radiation and the remaining two respond to emitted thermal radiation from the earth and its atmosphere. The two thermal channels are calibrated in terms of equivalent blackbody temperatures, and the reflected solar radiation channels in terms of effective radiant emittances. The calibration data, along with orbital and attitude data and the radiation data from the satellite, were incorporated in a computer program for an IBM 7090 which was used to produce, in binary form, the "Final Meteorological Radiation Tape" which is the basic repository of all radiation data. After launch, the radiometer displaye d the same degradation of response characteristics as did its predecessors in TIROS II and TIROS III. The onset of degradation results in a departure of the data from the prelaunch laboratory calibration. The cause of degradation has not been determined, and the matter is still being studied at the Goddard Space Flight Center. Before work with the TIROS IV radiation data is attempted, an understanding of the radiometer, its calibration, and the problems encountered in the experiment, especially from response degradation, is essential. The instrumentation design, development work, and the calibrations herein described were performed by the Goddard Space Flight Center Staff, whereas the computer and programming efforts were carried out jointly by the staffs of the National Weather Satellite Center, U. S. Weather Bureau, and the Goddard Space Flight Center. In this Catalog-Manual, the radiometer an d its calibration, data processing, the "Final Meteorological Radiation Tape", the observed degradation patterns, and possible corrections for degradation are discussed. The Catalog-Manual also includes, in two forms, documentation of each orbit of successfully reduced radiation data acquired by TIROS IV. One method of presentation is the Index of Final Meteorological Radiation Tapes and the other is a Subpoint Track, Summary of Available Radiation Data in diagrammatic form.

Land surface temperature measurements from EOS MODIS data

NASA Technical Reports Server (NTRS)

Wan, Zhengming

1993-01-01

The task objectives of this reporting phase included: (1) completing the draft of the LST Algorithms Theoretical Basic Document by July 30, 1993; (2) making a detailed characterization of the thermal infrared measurement system including spectrometer, blackbody, and radiation sources; (3) making TIR spectral measurements of water and snow-cover surfaces with the MIDAC M2401 spectrometer; and (4) making conceptual and engineering design of an accessory system for spectrometric measurements at variable angles. These objectives are based on the requirements by the MODIS Science Team and the unique challenge in the development of MODIS LST algorithms: to acquire accurate spectral emissivity data of land covers in the near-term and to make ground validations of the LST product in the long-term with a TIR measurement system.

Rare Earth Doped Yttrium Aluminum Garnet (YAG) Selective Emitters

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Pal, AnnaMarie T.; Patton, Martin O.; Jenkins, Phillip P.

1999-01-01

As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study presents a spectral emittance model for films and cylinders of rare earth doped yttrium aluminum garnets. Good agreement between experimental and theoretical film spectral emittances was found for erbium and holmium aluminum garnets. Spectral emittances of films are sensitive to temperature differences across the film. For operating conditions of interest, the film emitter experiences a linear temperature variation whereas the cylinder emitter has a more advantageous uniform temperature. Emitter efficiency is also a sensitive function of temperature. For holminum aluminum garnet film the efficiency is 0.35 at 1446K but only 0.27 at 1270 K.

Plasmonically Enhanced Reflectance of Heat Radiation from Low-Bandgap Semiconductor Microinclusions.

PubMed

Tang, Janika; Thakore, Vaibhav; Ala-Nissila, Tapio

2017-07-18

Increased reflectance from the inclusion of highly scattering particles at low volume fractions in an insulating dielectric offers a promising way to reduce radiative thermal losses at high temperatures. Here, we investigate plasmonic resonance driven enhanced scattering from microinclusions of low-bandgap semiconductors (InP, Si, Ge, PbS, InAs and Te) in an insulating composite to tailor its infrared reflectance for minimizing thermal losses from radiative transfer. To this end, we compute the spectral properties of the microcomposites using Monte Carlo modeling and compare them with results from Fresnel equations. The role of particle size-dependent Mie scattering and absorption efficiencies, and, scattering anisotropy are studied to identify the optimal microinclusion size and material parameters for maximizing the reflectance of the thermal radiation. For composites with Si and Ge microinclusions we obtain reflectance efficiencies of 57-65% for the incident blackbody radiation from sources at temperatures in the range 400-1600 °C. Furthermore, we observe a broadbanding of the reflectance spectra from the plasmonic resonances due to charge carriers generated from defect states within the semiconductor bandgap. Our results thus open up the possibility of developing efficient high-temperature thermal insulators through use of the low-bandgap semiconductor microinclusions in insulating dielectrics.

The Creative Power of Formal Analogies in Physics: The Case of Albert Einstein

NASA Astrophysics Data System (ADS)

Gingras, Yves

2015-07-01

In order to show how formal analogies between different physical systems play an important conceptual work in physics, this paper analyzes the evolution of Einstein's thoughts on the structure of radiation from the point of view of the formal analogies he used as "lenses" to "see" through the "black box" of Planck's blackbody radiation law. A comparison is also made with his 1925 paper on the quantum gas where he used the same formal methods. Changes of formal points of view are most of the time taken for granted or passed over in silence in studies on the mathematization of physics as if they had no special significance. Revisiting Einstein's classic papers on the nature of light and matter from the angle of the various theoretical tools he used, namely entropy and energy fluctuation calculations, helps explain why he was in a unique position to make visible the particle structure of radiation and the dual (particle and wave) nature of light and matter. Finally, this case study calls attention to the more general question of the surprising creative power of formal analogies and their frequent use in theoretical physics. This aspect of intellectual creation can be useful in the teaching of physics.

Sensor for performance monitoring of advanced gas turbines

NASA Astrophysics Data System (ADS)

Latvakoski, Harri M.; Markham, James R.; Harrington, James A.; Haan, David J.

1999-01-01

Advanced thermal coating materials are being developed for use in the combustor section of high performance turbine engines to allow for higher combustion temperatures. To optimize the use of these thermal barrier coatings (TBC), accurate surface temperature measurements are required to understand their response to changes in the combustion environment. Present temperature sensors, which are based on the measurement of emitted radiation, are not well studied for coated turbine blades since their operational wavelengths are not optimized for the radiative properties of the TBC. This work is concerned with developing an instrument to provide accurate, real-time measurements of the temperature of TBC blades in an advanced turbine engine. The instrument will determine the temperature form a measurement of the radiation emitted at the optimum wavelength, where the TBC radiates as a near-blackbody. The operational wavelength minimizes interference from the high temperature and pressure environment. A hollow waveguide is used to transfer the radiation from the engine cavity to a high-speed detector and data acquisition system. A prototype of this system was successfully tested at an atmospheric burner test facility, and an on-engine version is undergoing testing for installation on a high-pressure rig.

Polarization of Gamma-Ray Bursts in the Dissipative Photosphere Model

NASA Astrophysics Data System (ADS)

Lundman, Christoffer; Vurm, Indrek; Beloborodov, Andrei M.

2018-04-01

The MeV spectral peak of gamma-ray bursts (GRBs) is best explained as photospheric emission from a dissipative relativistic jet. The observed non-blackbody spectrum shows that sub-photospheric dissipation involves both thermal plasma heating and injection of nonthermal particles, which quickly cool through inverse Compton scattering and emission of synchrotron radiation. Synchrotron photons emitted around and above the photosphere are predicted to dominate the low-energy part of the GRB spectrum, starting from roughly a decade in energy below the MeV peak. We show that this leads to a unique polarization signature: a rise in GRB polarization toward lower energies. We compute the polarization degree of GRB radiation as a function of photon energy for a generic jet model, and show the predictions for GRBs 990123, 090902B, and 110721A. The expected polarization is significant in the X-ray band, in particular for bursts similar to GRB 090902B. The model predicts that radiation in the MeV peak (and at higher energies) is unpolarized as long as the jet is approximately uniform on angular scales δθ ≳ Γ‑1 where Γ is the bulk Lorentz factor of the jet.

Towards the development of high temperature comparison artifacts for radiation thermometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teixeira, R. N.; Machin, G.; Orlando, A.

This paper describes the methodology and first results of the development of high temperature fixed point artifacts of unknown temperature suitable for scale comparison purposes. This study is being undertaken at the Thermal Metrology Division of Inmetro, Brazil, as part of PhD studies. In this initial phase of the study two identical cobalt carbon eutectic cells were constructed and one doped with a known amount of copper. This was an attempt to achieve a controlled change in the transition temperature of the alloy during melting. Copper was chosen due to the relatively simple phase diagram it forms with carbon andmore » cobalt. The cobalt, in powder form, was supplied by Alfa Aesar at 99.998 % purity, and was mixed with carbon powder (1,9 % by weight) of 99.9999 % purity. Complete filling of the crucible took 6 steps and was performed in a vertical furnace with graphite heating elements, in an inert gas atmosphere. The temperature measurements were performed using a KE LP3 radiation thermometer, which was previously evaluated for spectral responsivity, linearity and size-of-source effect (SSE). During these measurements, the thermometer stability was periodically checked using a silver fixed point blackbody maintained in a three zone furnace. The main purpose of the first part of this study is to dope a series of Co-C blackbody with differing amounts of copper, in order to alter their temperatures whilst still retaining good melting plateau performance. The long-term stability of the adjusted transition temperatures will also be investigated. Other dopants will be studied as the research progresses, and thermo chemical modeling will be performed in an attempt to understand the change in temperature with dopant concentration and so help select suitable dopants in the future. The overall objective is to construct comparison artifacts that have good performance, in terms of plateau shape and long-term temperature stability, but with unknown temperatures. These can then be used as comparison artifacts with no participant, except the pilot, knowing the temperature a priori.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kırmızıbayrak, Demet; Şaşmaz Muş, Sinem; Kaneko, Yuki

We present our broadband (2–250 keV) time-averaged spectral analysis of 388 bursts from SGR J1550−5418, SGR 1900+14, and SGR 1806−20 detected with the Rossi X-ray Timing Explorer ( RXTE ) here and as a database in a companion web-catalog. We find that two blackbody functions (BB+BB), the sum of two modified blackbody functions (LB+LB), the sum of a blackbody function and a power-law function (BB+PO), and a power law with a high-energy exponential cutoff (COMPT) all provide acceptable fits at similar levels. We performed numerical simulations to constrain the best fitting model for each burst spectrum and found that 67.6%more » of burst spectra with well-constrained parameters are better described by the Comptonized model. We also found that 64.7% of these burst spectra are better described with the LB+LB model, which is employed in the spectral analysis of a soft gamma repeater (SGR) for the first time here, than with the BB+BB and BB+PO models. We found a significant positive lower bound trend on photon index, suggesting a decreasing upper bound on hardness, with respect to total flux and fluence. We compare this result with bursts observed from SGR and AXP (anomalous X-ray pulsar) sources and suggest that the relationship is a distinctive characteristic between the two. We confirm a significant anticorrelation between burst emission area and blackbody temperature, and find that it varies between the hot and cool blackbody temperatures differently than previously discussed. We expand on the interpretation of our results in the framework of a strongly magnetized neutron star.« less

Report on the measurement results for the EURAMET 658 extension: project to examine underlying parameters in radiance scale realisation

NASA Astrophysics Data System (ADS)

McEvoy, Helen; Martin, Maria Jose; Steiner, Anton; Schreiber, Ekkehard; Girard, Ferruccio; Battuello, Mauro; Sadli, Mohamed; Ridoux, Pascal; Gutschwager, Berndt; Hollandt, Joerg; Diril, Ahmet; Pehlivan, Özlem

2018-01-01

This report describes the measurement procedures and participant results for the EURAMET project 658 extension—'project to examine underlying parameters in radiance temperature scale realisation from 156 °C to 1000 °C', with particular emphasis on the results of the variable temperature and fixed point blackbody measurements for the justification of radiation thermometry CMCs. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The Emergent 1.1-1.7 μm Spectrum of the Exoplanet CoRoT-2b as Measured Using the Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Wilkins, Ashlee N.; Deming, Drake; Madhusudhan, Nikku; Burrows, Adam; Knutson, Heather; McCullough, Peter; Ranjan, Sukrit

2014-03-01

We have used Hubble/WFC3 and the G141 grism to measure the secondary eclipse of the transiting, very hot Jupiter CoRoT-2b in the 1.1-1.7 μm spectral region. We find an eclipse depth averaged over this band equal to 395^{+69}_{-45} parts per million, equivalent to a blackbody temperature of 1788 ± 18 K. We study and characterize several WFC3 instrumental effects, especially the "hook" phenomenon described by Deming et al. We use data from several transiting exoplanet systems to find a quantitative relation between the amplitude of the hook and the exposure level of a given pixel. Although the uncertainties in this relation are too large to allow us to develop an empirical correction for our data, our study provides a useful guide for optimizing exposure levels in future WFC3 observations. We derive the planet's spectrum using a differential method. The planet-to-star contrast increases to longer wavelength within the WFC3 bandpass, but without water absorption or emission to a 3σ limit of 85 ppm. The slope of the WFC3 spectrum is significantly less than the slope of the best-fit blackbody. We compare all existing eclipse data for this planet to a blackbody spectrum, and to spectra from both solar abundance and carbon-rich (C/O = 1) models. A blackbody spectrum is an acceptable fit to the full data set. Extra continuous opacity due to clouds or haze, and flattened temperature profiles, are strong candidates to produce quasi-blackbody spectra, and to account for the amplitude of the optical eclipses. Our results show ambiguous evidence for a temperature inversion in this planet.

Broadband Spectral Investigations of Magnetar Bursts

NASA Astrophysics Data System (ADS)

Kırmızıbayrak, Demet; Şaşmaz Muş, Sinem; Kaneko, Yuki; Göğüş, Ersin

2017-09-01

We present our broadband (2-250 keV) time-averaged spectral analysis of 388 bursts from SGR J1550-5418, SGR 1900+14, and SGR 1806-20 detected with the Rossi X-ray Timing Explorer (RXTE) here and as a database in a companion web-catalog. We find that two blackbody functions (BB+BB), the sum of two modified blackbody functions (LB+LB), the sum of a blackbody function and a power-law function (BB+PO), and a power law with a high-energy exponential cutoff (COMPT) all provide acceptable fits at similar levels. We performed numerical simulations to constrain the best fitting model for each burst spectrum and found that 67.6% of burst spectra with well-constrained parameters are better described by the Comptonized model. We also found that 64.7% of these burst spectra are better described with the LB+LB model, which is employed in the spectral analysis of a soft gamma repeater (SGR) for the first time here, than with the BB+BB and BB+PO models. We found a significant positive lower bound trend on photon index, suggesting a decreasing upper bound on hardness, with respect to total flux and fluence. We compare this result with bursts observed from SGR and AXP (anomalous X-ray pulsar) sources and suggest that the relationship is a distinctive characteristic between the two. We confirm a significant anticorrelation between burst emission area and blackbody temperature, and find that it varies between the hot and cool blackbody temperatures differently than previously discussed. We expand on the interpretation of our results in the framework of a strongly magnetized neutron star.

The role of the equivalent blackbody temperature in the study of Atlantic Ocean tropical cyclones

NASA Technical Reports Server (NTRS)

Steranka, J.; Rodgers, E. B.; Gentry, R. C.

1983-01-01

Satellite measured equivalent blackbody temperatures of Atlantic Ocean tropical cyclones are used to investigate their role in describing the convection and cloud patterns of the storms and in predicting wind intensity. The high temporal resolution of the equivalent blackbody temperature measurements afforded with the geosynchronous satellite provided sequential quantitative measurements of the tropical cyclone which reveal a diurnal pattern of convection at the inner core during the early developmental stage; a diurnal pattern of cloudiness in the storm's outer circulation throughout the life cycle; a semidiurnal pattern of cloudiness in the environmental atmosphere surrounding the storms during the weak storm stage; an outward modulating atmospheric wave originating at the inner core; and long term convective bursts at the inner core prior to wind intensification.

Blackbody absorption efficiencies for six lamp pumped Nd laser materials

NASA Technical Reports Server (NTRS)

Cross, Patricia L.; Barnes, Norman P.; Skolaut, Milton W., Jr.; Storm, Mark E.

1990-01-01

Utilizing high resolution spectra, the absorption efficiencies for six Nd laser materials were calculated as functions of the effective blackbody temperature of the lamp and laser crystal size. The six materials were Nd:YAG, Nd:YLF, Nd:Q-98 Glass, Nd:YVO4, Nd:BEL, and Nd:Cr:GSGG. Under the guidelines of this study, Nd:Cr:GSGG's absorption efficiency is twice the absorption efficiency of any of the other laser materials.

Thermal emission and absorption of radiation in finite inverted-opal photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Florescu, Marian; Stimpson, Andrew J.; Lee, Hwang

We study theoretically the optical properties of a finite inverted-opal photonic crystal. The light-matter interaction is strongly affected by the presence of the three-dimensional photonic crystal and the alterations of the light emission and absorption processes can be used to suppress or enhance the thermal emissivity and absorptivity of the dielectric structure. We investigate the influence of the absorption present in the system on the relevant band edge frequencies that control the optical response of the photonic crystal. Our study reveals that the absorption processes cause spectral broadening and shifting of the band edge optical resonances, and determine a strongmore » reduction of the photonic band gap spectral range. Using the angular and spectral dependence of the band edge frequencies for stop bands along different directions, we argue that by matching the blackbody emission spectrum peak with a prescribed maximum of the absorption coefficient, it is possible to achieve an angle-sensitive enhancement of the thermal emission/absorption of radiation. This result opens a way to realize a frequency-sensitive and angle-sensitive photonic crystal absorbers/emitters.« less

Absolute high spectral resolution measurements of surface solar radiation for detection of water vapour continuum absorption.

PubMed

Gardiner, T D; Coleman, M; Browning, H; Tallis, L; Ptashnik, I V; Shine, K P

2012-06-13

Solar-pointing Fourier transform infrared (FTIR) spectroscopy offers the capability to measure both the fine scale and broadband spectral structure of atmospheric transmission simultaneously across wide spectral regions. It is therefore suited to the study of both water vapour monomer and continuum absorption behaviours. However, in order to properly address this issue, it is necessary to radiatively calibrate the FTIR instrument response. A solar-pointing high-resolution FTIR spectrometer was deployed as part of the 'Continuum Absorption by Visible and Infrared radiation and its Atmospheric Relevance' (CAVIAR) consortium project. This paper describes the radiative calibration process using an ultra-high-temperature blackbody and the consideration of the related influence factors. The result is a radiatively calibrated measurement of the solar irradiation at the ground across the IR region from 2000 to 10 000 cm(-1) with an uncertainty of between 3.3 and 5.9 per cent. This measurement is shown to be in good general agreement with a radiative-transfer model. The results from the CAVIAR field measurements are being used in ongoing studies of atmospheric absorbers, in particular the water vapour continuum.

Remote laser evaporative molecular absorption spectroscopy

NASA Astrophysics Data System (ADS)

Hughes, Gary B.; Lubin, Philip; Cohen, Alexander; Madajian, Jonathan; Kulkarni, Neeraj; Zhang, Qicheng; Griswold, Janelle; Brashears, Travis

2016-09-01

We describe a novel method for probing bulk molecular and atomic composition of solid targets from a distant vantage. A laser is used to melt and vaporize a spot on the target. With sufficient flux, the spot temperature rises rapidly, and evaporation of surface materials occurs. The melted spot creates a high-temperature blackbody source, and ejected material creates a plume of surface materials in front of the spot. Molecular and atomic absorption occurs as the blackbody radiation passes through the ejected plume. Bulk molecular and atomic composition of the surface material is investigated by using a spectrometer to view the heated spot through the ejected plume. The proposed method is distinct from current stand-off approaches to composition analysis, such as Laser-Induced Breakdown Spectroscopy (LIBS), which atomizes and ionizes target material and observes emission spectra to determine bulk atomic composition. Initial simulations of absorption profiles with laser heating show great promise for Remote Laser-Evaporative Molecular Absorption (R-LEMA) spectroscopy. The method is well-suited for exploration of cold solar system targets—asteroids, comets, planets, moons—such as from a spacecraft orbiting the target. Spatial composition maps could be created by scanning the surface. Applying the beam to a single spot continuously produces a borehole or trench, and shallow subsurface composition profiling is possible. This paper describes system concepts for implementing the proposed method to probe the bulk molecular composition of an asteroid from an orbiting spacecraft, including laser array, photovoltaic power, heating and ablation, plume characteristics, absorption, spectrometry and data management.

A Summary of Lightpipe Radiation Thermometry Research at NIST

PubMed Central

Tsai, Benjamin K.

2006-01-01

During the last 10 years, research in light-pipe radiation thermometry has significantly reduced the uncertainties for temperature measurements in semiconductor processing. The National Institute of Standards and Technology (NIST) has improved the calibration of lightpipe radiation thermometers (LPRTs), the characterization procedures for LPRTs, the in situ calibration of LPRTs using thin-film thermocouple (TFTC) test wafers, and the application of model-based corrections to improve LPRT spectral radiance temperatures. Collaboration with industry on implementing techniques and ideas established at NIST has led to improvements in temperature measurements in semiconductor processing. LPRTs have been successfully calibrated at NIST for rapid thermal processing (RTP) applications using a sodium heat-pipe blackbody between 700 °C and 900 °C with an uncertainty of about 0.3 °C (k = 1) traceable to the International Temperature Scale of 1990. Employing appropriate effective emissivity models, LPRTs have been used to determine the wafer temperature in the NIST RTP Test Bed with an uncertainty of 3.5 °C. Using a TFTC wafer for calibration, the LPRT can measure the wafer temperature in the NIST RTP Test Bed with an uncertainty of 2.3 °C. Collaborations with industry in characterizing and calibrating LPRTs will be summarized, and future directions for LPRT research will be discussed. PMID:27274914

Twin-Slot Antenna-Coupled Superconducting Ti Transition-Edge Sensor at 350 GHz

NASA Astrophysics Data System (ADS)

Zhang, W.; Miao, W.; Wang, Z.; Guo, X. H.; Liu, D.; Zhong, J. Q.; Yao, Q. J.; Shi, S. C.

2018-05-01

We have developed four-leg-supported superconducting Ti transition-edge sensors (TES) formed by KOH wet etching. Energy relaxation mechanism is changed from electron-phonon coupling to diffusive phonon after wet etching. The current-voltage curves of the same TES device were measured before and after wet etching. After wet etching, its thermal conductance (G) is reduced to 500 pW/K from 8950 pW/K. The measured effective response time (τ eff) is 143 μs, about 30 times larger. In addition, we have studied the optical noise equivalent power (NEP) with a cryogenic blackbody in combination with metal-mesh filters to define the radiation bandwidth. The obtained optical NEP is 5 × 10-16 W/√Hz, which is suitable for ground-based astronomical applications.

Doppler-Free Spectroscopy of the {sup 1}S{sub 0}-{sup 3}P{sub 0} Optical Clock Transition in Laser-Cooled Fermionic Isotopes of Neutral Mercury

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petersen, M.; Chicireanu, R.; Dawkins, S. T.

2008-10-31

We report direct laser spectroscopy of the {sup 1}S{sub 0}-{sup 3}P{sub 0} transition at 265.6 nm in fermionic isotopes of neutral mercury in a magneto-optical trap. Measurements of the frequency against the LNE-SYRTE primary reference using an optical frequency comb yield 1 128 575 290 808.4{+-}5.6 kHz in {sup 199}Hg and 1 128 569 561 139.6{+-}5.3 kHz in {sup 201}Hg. The uncertainty, allowed by the observation of the Doppler-free recoil doublet, is 4 orders of magnitude lower than previous indirect determinations. Mercury is a promising candidate for future optical lattice clocks due to its low sensitivity to blackbody radiation.

Modeling and validation of photometric characteristics of space targets oriented to space-based observation.

PubMed

Wang, Hongyuan; Zhang, Wei; Dong, Aotuo

2012-11-10

A modeling and validation method of photometric characteristics of the space target was presented in order to track and identify different satellites effectively. The background radiation characteristics models of the target were built based on blackbody radiation theory. The geometry characteristics of the target were illustrated by the surface equations based on its body coordinate system. The material characteristics of the target surface were described by a bidirectional reflectance distribution function model, which considers the character of surface Gauss statistics and microscale self-shadow and is obtained by measurement and modeling in advance. The contributing surfaces of the target to observation system were determined by coordinate transformation according to the relative position of the space-based target, the background radiation sources, and the observation platform. Then a mathematical model on photometric characteristics of the space target was built by summing reflection components of all the surfaces. Photometric characteristics simulation of the space-based target was achieved according to its given geometrical dimensions, physical parameters, and orbital parameters. Experimental validation was made based on the scale model of the satellite. The calculated results fit well with the measured results, which indicates the modeling method of photometric characteristics of the space target is correct.

Experiments on the CMB Spectrum, Big Jets Model and Their Implications for the Missing Half of the Universe

NASA Astrophysics Data System (ADS)

Hsu, Leonardo; Hsu, Jong-Ping

2018-01-01

Based on the limiting continuation of Lorentz-Poincaré invariance, we propose an alternative formulation of the generalized Planck distribution for inertial and noninertial frames. The Lorentz invariant Planck distribution law leads to a new physical interpretation of the dipole anisotropy of the Cosmic Microwave Background. The Big Jets model predicts a distant `antimatter blackbody,' whose radiations could make 50% of the sky very slightly warmer than the isotropic CMB temperature TCMB with a cosine function. The other 50% of the sky has the same isotropic temperature TCMB. Thus, we could have a pseudo-dipole anisotropy because the microwaves emitted from the antimatter blackbody are totally absorbed by our matter blackbody. We suggest that accurate data of satellite experiments might be used to search for the pseudo-dipole anisotropy and the missing half of the antimatter universe.

The emergent 1.1-1.7 μm spectrum of the exoplanet COROT-2B as measured using the Hubble space telescope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilkins, Ashlee N.; Deming, Drake; Madhusudhan, Nikku

2014-03-10

We have used Hubble/WFC3 and the G141 grism to measure the secondary eclipse of the transiting, very hot Jupiter CoRoT-2b in the 1.1-1.7 μm spectral region. We find an eclipse depth averaged over this band equal to 395{sub −45}{sup +69} parts per million, equivalent to a blackbody temperature of 1788 ± 18 K. We study and characterize several WFC3 instrumental effects, especially the 'hook' phenomenon described by Deming et al. We use data from several transiting exoplanet systems to find a quantitative relation between the amplitude of the hook and the exposure level of a given pixel. Although the uncertaintiesmore » in this relation are too large to allow us to develop an empirical correction for our data, our study provides a useful guide for optimizing exposure levels in future WFC3 observations. We derive the planet's spectrum using a differential method. The planet-to-star contrast increases to longer wavelength within the WFC3 bandpass, but without water absorption or emission to a 3σ limit of 85 ppm. The slope of the WFC3 spectrum is significantly less than the slope of the best-fit blackbody. We compare all existing eclipse data for this planet to a blackbody spectrum, and to spectra from both solar abundance and carbon-rich (C/O = 1) models. A blackbody spectrum is an acceptable fit to the full data set. Extra continuous opacity due to clouds or haze, and flattened temperature profiles, are strong candidates to produce quasi-blackbody spectra, and to account for the amplitude of the optical eclipses. Our results show ambiguous evidence for a temperature inversion in this planet.« less

Investigation of advanced propulsion technologies: The RAM accelerator and the flowing gas radiation heater

NASA Technical Reports Server (NTRS)

Bruckner, A. P.; Knowlen, C.; Mattick, A. T.; Hertzberg, A.

1992-01-01

The two principal areas of advanced propulsion investigated are the ram accelerator and the flowing gas radiation heater. The concept of the ram accelerator is presented as a hypervelocity launcher for large-scale aeroballistic range applications in hypersonics and aerothermodynamics research. The ram accelerator is an in-bore ramjet device in which a projectile shaped like the centerbody of a supersonic ramjet is propelled in a stationary tube filled with a tailored combustible gas mixture. Combustion on and behind the projectile generates thrust which accelerates it to very high velocities. The acceleration can be tailored for the 'soft launch' of instrumented models. The distinctive reacting flow phenomena that have been observed in the ram accelerator are relevant to the aerothermodynamic processes in airbreathing hypersonic propulsion systems and are useful for validating sophisticated CFD codes. The recently demonstrated scalability of the device and the ability to control the rate of acceleration offer unique opportunities for the use of the ram accelerator as a large-scale hypersonic ground test facility. The flowing gas radiation receiver is a novel concept for using solar energy to heat a working fluid for space power or propulsion. Focused solar radiation is absorbed directly in a working gas, rather than by heat transfer through a solid surface. Previous theoretical analysis had demonstrated that radiation trapping reduces energy loss compared to that of blackbody receivers, and enables higher efficiencies and higher peak temperatures. An experiment was carried out to measure the temperature profile of an infrared-active gas and demonstrate the effect of radiation trapping. The success of this effort validates analytical models of heat transfer in this receiver, and confirms the potential of this approach for achieving high efficiency space power and propulsion.

A Summary of Lightpipe Radiation Thermometry Research at NIST.

PubMed

Tsai, Benjamin K

2006-01-01

During the last 10 years, research in light-pipe radiation thermometry has significantly reduced the uncertainties for temperature measurements in semiconductor processing. The National Institute of Standards and Technology (NIST) has improved the calibration of lightpipe radiation thermometers (LPRTs), the characterization procedures for LPRTs, the in situ calibration of LPRTs using thin-film thermocouple (TFTC) test wafers, and the application of model-based corrections to improve LPRT spectral radiance temperatures. Collaboration with industry on implementing techniques and ideas established at NIST has led to improvements in temperature measurements in semiconductor processing. LPRTs have been successfully calibrated at NIST for rapid thermal processing (RTP) applications using a sodium heat-pipe blackbody between 700 °C and 900 °C with an uncertainty of about 0.3 °C (k = 1) traceable to the International Temperature Scale of 1990. Employing appropriate effective emissivity models, LPRTs have been used to determine the wafer temperature in the NIST RTP Test Bed with an uncertainty of 3.5 °C. Using a TFTC wafer for calibration, the LPRT can measure the wafer temperature in the NIST RTP Test Bed with an uncertainty of 2.3 °C. Collaborations with industry in characterizing and calibrating LPRTs will be summarized, and future directions for LPRT research will be discussed.

Determination of combustion gas temperatures by infrared radiometry in sooting and nonsooting flames

NASA Technical Reports Server (NTRS)

Lyons, Valerie J.; Gracia-Salcedo, Carmen M.

1989-01-01

Flame temperatures in nonsooting and sooting environments were successfully measured by radiometry for pre-mixed propane-oxygen laminar flames stabilized on a water-cooled, porous sintered-bronze burner. The measured temperatures in the nonsooting flames were compared with fine-wire thermocouple measurements. The results show excellent agreement below 1700 K, and when the thermocouple measurements were corrected for radiation effects, the agreement was good for even higher temperatures. The benefits of radiometry are: (1) the flow is not disturbed by an intruding probe, (2) calibration is easily done using a blackbody source, and (3) measurements can be made even with soot present. The theory involved in the radiometry measurements and the energy balance calculations used to correct the thermocouple temperature measurements are discussed.

X-ray nova MAXI J1828-249. Evolution of the broadband spectrum during its 2013-2014 outburst

NASA Astrophysics Data System (ADS)

Grebenev, S. A.; Prosvetov, A. V.; Burenin, R. A.; Krivonos, R. A.; Mescheryakov, A. V.

2016-02-01

Based on data from the SWIFT, INTEGRAL, MAXI/ISS orbital observatories, and the ground-based RTT-150 telescope, we have investigated the broadband (from the optical to the hard X-ray bands) spectrum of the X-ray nova MAXI J1828-249 and its evolution during the outburst of the source in 2013-2014. The optical and infrared emissions from the nova are shown to be largely determined by the extension of the power-law component responsible for the hard X-ray emission. The contribution from the outer cold regions of the accretion disk, even if the X-ray heating of its surface is taken into account, turns out to be moderate during the source's "high" state (when a soft blackbody emission component is observed in the X-ray spectrum) and is virtually absent during its "low" ("hard") state. This result suggests that much of the optical and infrared emissions from such systems originates in the same region of main energy release where their hard X-ray emission is formed. This can be the Compton or synchro-Compton radiation from a high-temperature plasma in the central accretion disk region puffed up by instabilities, the synchrotron radiation from a hot corona above the disk, or the synchrotron radiation from its relativistic jets.

Spectral shifting strongly constrains molecular cloud disruption by radiation pressure on dust

NASA Astrophysics Data System (ADS)

Reissl, Stefan; Klessen, Ralf S.; Mac Low, Mordecai-Mark; Pellegrini, Eric W.

2018-03-01

Aim. We aim to test the hypothesis that radiation pressure from young star clusters acting on dust is the dominant feedback agent disrupting the largest star-forming molecular clouds and thus regulating the star-formation process. Methods: We performed multi-frequency, 3D, radiative transfer calculations including both scattering and absorption and re-emission to longer wavelengths for model clouds with masses of 104-107 M⊙, containing embedded clusters with star formation efficiencies of 0.009-91%, and varying maximum grain sizes up to 200 μm. We calculated the ratio between radiative and gravitational forces to determine whether radiation pressure can disrupt clouds. Results: We find that radiation pressure acting on dust almost never disrupts star-forming clouds. Ultraviolet and optical photons from young stars to which the cloud is optically thick do not scatter much. Instead, they quickly get absorbed and re-emitted by the dust at thermal wavelengths. As the cloud is typically optically thin to far-infrared radiation, it promptly escapes, depositing little momentum in the cloud. The resulting spectrum is more narrowly peaked than the corresponding Planck function, and exhibits an extended tail at longer wavelengths. As the opacity drops significantly across the sub-mm and mm wavelength regime, the resulting radiative force is even smaller than for the corresponding single-temperature blackbody. We find that the force from radiation pressure falls below the strength of gravitational attraction by an order of magnitude or more for either Milky Way or moderate starbust conditions. Only for unrealistically large maximum grain sizes, and star formation efficiencies far exceeding 50% do we find that the strength of radiation pressure can exceed gravity. Conclusions: We conclude that radiation pressure acting on dust does not disrupt star-forming molecular clouds in any Local Group galaxies. Radiation pressure thus appears unlikely to regulate the star-formation process on either local or global scales.

Universe opacity and CMB

NASA Astrophysics Data System (ADS)

Vavryčuk, Václav

2018-04-01

A cosmological model, in which the cosmic microwave background (CMB) is a thermal radiation of intergalactic dust instead of a relic radiation of the Big Bang, is revived and revisited. The model suggests that a virtually transparent local Universe becomes considerably opaque at redshifts z > 2 - 3. Such opacity is hardly to be detected in the Type Ia supernova data, but confirmed using quasar data. The opacity steeply increases with redshift because of a high proper density of intergalactic dust in the previous epochs. The temperature of intergalactic dust increases as (1 + z) and exactly compensates the change of wavelengths due to redshift, so that the dust radiation looks apparently like the radiation of the blackbody with a single temperature. The predicted dust temperature is TD = 2.776 K, which differs from the CMB temperature by 1.9% only, and the predicted ratio between the total CMB and EBL intensities is 13.4 which is close to 12.5 obtained from observations. The CMB temperature fluctuations are caused by EBL fluctuations produced by galaxy clusters and voids in the Universe. The polarization anomalies of the CMB correlated with temperature anisotropies are caused by the polarized thermal emission of needle-shaped conducting dust grains aligned by large-scale magnetic fields around clusters and voids. A strong decline of the luminosity density for z > 4 is interpreted as the result of high opacity of the Universe rather than of a decline of the global stellar mass density at high redshifts.

NuSTAR + XMM-Newton monitoring of the neutron star transient AX J1745.6-2901

NASA Astrophysics Data System (ADS)

Ponti, G.; Bianchi, S.; Muñoz-Darias, T.; Mori, K.; De, K.; Rau, A.; De Marco, B.; Hailey, C.; Tomsick, J.; Madsen, K. K.; Clavel, M.; Rahoui, F.; Lal, D. V.; Roy, S.; Stern, D.

2018-01-01

AX J1745.6-2901 is a high-inclination (eclipsing) transient neutron star (NS) low-mass X-ray binary showcasing intense ionized Fe K absorption. We present here the analysis of 11 XMM-Newton and 15 NuSTAR new data sets (obtained between 2013 and 2016), therefore tripling the number of observations of AX J1745.6-2901 in outburst. Thanks to simultaneous XMM-Newton and NuSTAR spectra, we greatly improve on the fitting of the X-ray continuum. During the soft state, the emission can be described by a disc blackbody (kT ∼ 1.1-1.2 keV and inner disc radius rDBB ∼ 14 km), plus hot (kT ∼ 2.2-3.0 keV) blackbody radiation with a small emitting radius (rBB ∼ 0.5 - 0.8 km) likely associated with the boundary layer or NS surface, plus a faint Comptonization component. Imprinted on the spectra are clear absorption features created by both neutral and ionized matter. Additionally, positive residuals suggestive of an emission Fe K α disc line and consistent with relativistic ionized reflection are present during the soft state, while such residuals are not significant during the hard state. The hard-state spectra are characterized by a hard (Γ ∼ 1.9-2.1) power law, showing no evidence for a high energy cut-off (kTe > 60-140 keV) and implying a small optical depth (τ < 1.6). The new observations confirm the previously witnessed trend of exhibiting strong Fe K absorption in the soft state that significantly weakens during the hard state. Optical (GROND) and radio (GMRT) observations suggest for AX J1745.6-2901 a standard broad-band spectral energy distribution as typically observed in accreting NSs.

Double Compton and Cyclo-Synchrotron in Super-Eddington Discs, Magnetized Coronae, and Jets

NASA Astrophysics Data System (ADS)

McKinney, Jonathan C.; Chluba, Jens; Wielgus, Maciek; Narayan, Ramesh; Sadowski, Aleksander

2017-05-01

Black hole accretion discs accreting near the Eddington rate are dominated by bremsstrahlung cooling, but above the Eddington rate, the double Compton process can dominate in radiation-dominated regions, while the cyclo-synchrotron can dominate in strongly magnetized regions like a corona or a jet. We present an extension to the general relativistic radiation magnetohydrodynamic code harmrad to account for emission and absorption by thermal cyclo-synchrotron, double Compton, bremsstrahlung, low-temperature opal opacities, as well as Thomson and Compton scattering. The harmrad code and associated analysis and visualization codes have been made open-source and are publicly available at the github repository website. We approximate the radiation field as a Bose-Einstein distribution and evolve it using the radiation number-energy-momentum conservation equations in order to track photon hardening. We perform various simulations to study how these extensions affect the radiative properties of magnetically arrested discs accreting at Eddington to super-Eddington rates. We find that double Compton dominates bremsstrahlung in the disc within a radius of r ˜ 15rg (gravitational radii) at hundred times the Eddington accretion rate, and within smaller radii at lower accretion rates. Double Compton and cyclo-synchrotron regulate radiation and gas temperatures in the corona, while cyclo-synchrotron regulates temperatures in the jet. Interestingly, as the accretion rate drops to Eddington, an optically thin corona develops whose gas temperature of T ˜ 109K is ˜100 times higher than the disc's blackbody temperature. Our results show the importance of double Compton and synchrotron in super-Eddington discs, magnetized coronae and jets.

Universe opacity and CMB

NASA Astrophysics Data System (ADS)

Vavryčuk, Václav

2018-07-01

A cosmological model, in which the cosmic microwave background (CMB) is a thermal radiation of intergalactic dust instead of a relic radiation of the big bang, is revived and revisited. The model suggests that a virtually transparent local Universe becomes considerably opaque at redshifts z > 2-3. Such opacity is hardly to be detected in the Type Ia supernova data, but confirmed using quasar data. The opacity steeply increases with redshift because of a high proper density of intergalactic dust in the previous epochs. The temperature of intergalactic dust increases as (1 + z) and exactly compensates the change of wavelengths due to redshift, so that the dust radiation looks apparently like the radiation of the blackbody with a single temperature. The predicted dust temperature is TD = 2.776 K, which differs from the CMB temperature by 1.9 per cent only, and the predicted ratio between the total CMB and extragalactic background light (EBL) intensities is 13.4 which is close to 12.5 obtained from observations. The CMB temperature fluctuations are caused by EBL fluctuations produced by galaxy clusters and voids in the Universe. The polarization anomalies of the CMB correlated with temperature anisotropies are caused by the polarized thermal emission of needle-shaped conducting dust grains aligned by large-scale magnetic fields around clusters and voids. A strong decline of the luminosity density for z > 4 is interpreted as the result of high opacity of the Universe rather than of a decline of the global stellar mass density at high redshifts.

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic.

PubMed

Rowan, W L; Houshmandyar, S; Phillips, P E; Austin, M E; Beno, J H; Hubbard, A E; Khodak, A; Ouroua, A; Taylor, G

2016-11-01

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct view of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Blackbody radiation sources are provided for in situ calibration.

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic

DOE PAGES

Rowan, W. L.; Houshmandyar, S.; Phillips, P. E.; ...

2016-09-07

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct viewmore » of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Here, blackbody radiation sources are provided for in situ calibration.« less

Measurements of thermal infrared spectral reflectance of frost, snow, and ice

NASA Technical Reports Server (NTRS)

Salisbury, John W.; D'Aria, Dana M.; Wald, Andrew

1994-01-01

Because much of Earth's surface is covered by frost, snow, and ice, the spectral emissivities of these materials are a significant input to radiation balance calculations in global atmospheric circulation and climate change models. Until now, however, spectral emissivities of frost and snow have been calculated from the optical constants of ice. We have measured directional hemispherical reflectance spectra of frost, snow, and ice from which emissivities can be predicted using Kirchhoff's law (e = 1-R). These measured spectra show that contrary to conclusions about the emissivity of snow drawn from previously calculated spectra, snow emissivity departs significantly from blackbody behavior in the 8-14 micrometer region of the spectrum; snow emissivity decreases with both increasing particle size and increasing density due to packing or grain welding; while snow emissivity increases due to the presence of meltwater.

The AU Mic Debris Disk: Far-infrared and Submillimeter Resolved Imaging

NASA Astrophysics Data System (ADS)

Matthews, Brenda C.; Kennedy, Grant; Sibthorpe, Bruce; Holland, Wayne; Booth, Mark; Kalas, Paul; MacGregor, Meredith; Wilner, David; Vandenbussche, Bart; Olofsson, Göran; Blommaert, Joris; Brandeker, Alexis; Dent, W. R. F.; de Vries, Bernard L.; Di Francesco, James; Fridlund, Malcolm; Graham, James R.; Greaves, Jane; Heras, Ana M.; Hogerheijde, Michiel; Ivison, R. J.; Pantin, Eric; Pilbratt, Göran L.

2015-10-01

We present far-infrared and submillimeter maps from the Herschel Space Observatory and the James Clerk Maxwell Telescope of the debris disk host star AU Microscopii. Disk emission is detected at 70, 160, 250, 350, 450, 500, and 850 μm. The disk is resolved at 70, 160, and 450 μm. In addition to the planetesimal belt, we detect thermal emission from AU Mic’s halo for the first time. In contrast to the scattered light images, no asymmetries are evident in the disk. The fractional luminosity of the disk is 3.9× {10}-4 and its milimeter-grain dust mass is 0.01 {M}\\oplus (±20%). We create a simple spatial model that reconciles the disk spectral energy distribution as a blackbody of 53 ± 2 K (a composite of 39 and 50 K components) and the presence of small (non-blackbody) grains which populate the extended halo. The best-fit model is consistent with the “birth ring” model explored in earlier works, i.e., an edge-on dust belt extending from 8.8 to 40 AU, but with an additional halo component with an {r}-1.5 surface density profile extending to the limits of sensitivity (140 AU). We confirm that AU Mic does not exert enough radiation force to blow out grains. For stellar mass-loss rates of 10-100 times solar, compact (zero porosity) grains can only be removed if they are very small; consistently with previous work, if the porosity is 0.9, then grains approaching 0.1 μm can be removed via corpuscular forces (i.e., the stellar wind).

Radiative heat transfer exceeding the blackbody limit between macroscale planar surfaces separated by a nanosize vacuum gap

NASA Astrophysics Data System (ADS)

Bernardi, Michael P.; Milovich, Daniel; Francoeur, Mathieu

2016-09-01

Using Rytov's fluctuational electrodynamics framework, Polder and Van Hove predicted that radiative heat transfer between planar surfaces separated by a vacuum gap smaller than the thermal wavelength exceeds the blackbody limit due to tunnelling of evanescent modes. This finding has led to the conceptualization of systems capitalizing on evanescent modes such as thermophotovoltaic converters and thermal rectifiers. Their development is, however, limited by the lack of devices enabling radiative transfer between macroscale planar surfaces separated by a nanosize vacuum gap. Here we measure radiative heat transfer for large temperature differences (~120 K) using a custom-fabricated device in which the gap separating two 5 × 5 mm2 intrinsic silicon planar surfaces is modulated from 3,500 to 150 nm. A substantial enhancement over the blackbody limit by a factor of 8.4 is reported for a 150-nm-thick gap. Our device paves the way for the establishment of novel evanescent wave-based systems.

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody.

PubMed

Zhu, Linxiao; Raman, Aaswath P; Fan, Shanhui

2015-10-06

A solar absorber, under the sun, is heated up by sunlight. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic for either operational or aesthetic considerations, but the resulting heating is undesirable. Because a solar absorber by necessity faces the sky, it also naturally has radiative access to the coldness of the universe. Therefore, in these applications it would be very attractive to directly use the sky as a heat sink while preserving solar absorption properties. Here we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal. When placed on a silicon absorber under sunlight, such a blackbody preserves or even slightly enhances sunlight absorption, but reduces the temperature of the underlying silicon absorber by as much as 13 °C due to radiative cooling. Our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities.

TRM4: Range performance model for electro-optical imaging systems

NASA Astrophysics Data System (ADS)

Keßler, Stefan; Gal, Raanan; Wittenstein, Wolfgang

2017-05-01

TRM4 is a commonly used model for assessing device and range performance of electro-optical imagers. The latest version, TRM4.v2, has been released by Fraunhofer IOSB of Germany in June 2016. While its predecessor, TRM3, was developed for thermal imagers, assuming blackbody targets and backgrounds, TRM4 extends the TRM approach to assess three imager categories: imagers that exploit emitted radiation (TRM4 category Thermal), reflected radiation (TRM4 category Visible/NIR/SWIR), and both emitted and reflected radiation (TRM4 category General). Performance assessment in TRM3 and TRM4 is based on the perception of standard four-bar test patterns, whether distorted by under-sampling or not. Spatial and sampling characteristics are taken into account by the Average Modulation at Optimum Phase (AMOP), which replaces the system MTF used in previous models. The Minimum Temperature Difference Perceived (MTDP) figure of merit was introduced in TRM3 for assessing the range performance of thermal imagers. In TRM4, this concept is generalized to the MDSP (Minimum Difference Signal Perceived), which can be applied to all imager categories. In this paper, we outline and discuss the TRM approach and pinpoint differences between TRM4 and TRM3. In addition, an overview of the TRM4 software and its functionality is given. Features newly introduced in TRM4, such as atmospheric turbulence, irradiation sources, and libraries are addressed. We conclude with an outlook on future work and the new module for intensified CCD cameras that is currently under development

Assessment of radiative feedback in climate models using satellite observations of annual flux variation.

PubMed

Tsushima, Yoko; Manabe, Syukuro

2013-05-07

In the climate system, two types of radiative feedback are in operation. The feedback of the first kind involves the radiative damping of the vertically uniform temperature perturbation of the troposphere and Earth's surface that approximately follows the Stefan-Boltzmann law of blackbody radiation. The second kind involves the change in the vertical lapse rate of temperature, water vapor, and clouds in the troposphere and albedo of the Earth's surface. Using satellite observations of the annual variation of the outgoing flux of longwave radiation and that of reflected solar radiation at the top of the atmosphere, this study estimates the so-called "gain factor," which characterizes the strength of radiative feedback of the second kind that operates on the annually varying, global-scale perturbation of temperature at the Earth's surface. The gain factor is computed not only for all sky but also for clear sky. The gain factor of so-called "cloud radiative forcing" is then computed as the difference between the two. The gain factors thus obtained are compared with those obtained from 35 models that were used for the fourth and fifth Intergovernmental Panel on Climate Change assessment. Here, we show that the gain factors obtained from satellite observations of cloud radiative forcing are effective for identifying systematic biases of the feedback processes that control the sensitivity of simulated climate, providing useful information for validating and improving a climate model.

Measurement of Far-Infrared Paint Emissivity for Reference Blackbody Modeling and Design

NASA Astrophysics Data System (ADS)

Kaplan, S. G.; Hanssen, L. M.; Mekhontsev, S. N.

2008-12-01

Blackbody sources are typically used for both ground-based and on-orbit calibration of infrared radiometers for atmospheric sounding. Accurate knowledge of the emissivity (or reflectivity) of the painted cavity surfaces is important for the design and modeling of the blackbody performance. Devices designed for the mid- to long-wave infrared (2 μm to 100 μm) generally use specular black paint and multiple (4 to 6) bounces to achieve high emissivity and uniform radiance over the required optical extent. To meet the CLARREO goal of long-term climate monitoring with an absolute uncertainty of < 0.1 K (3 σ), it will be necessary to calibrate radiance measurements to < 0.1 % uncertainty, which could require knowledge of paint emissivity with < 0.005 uncertainty at long wavelength. Critical material parameters include the dependence of emissivity on wavelength, angle of incidence, polarization, and temperature (200 K to 350 K), as well as contributions of scattered light. We present measurement methods and results in support of the CORSAIR SI-traceable far-infrared blackbody design, including temperature-dependent specular reflectance measurements out to 100 μm and angle-dependent data out to 25 μm. In addition, we describe the design for a proposed new facility at NIST (CBS3) that will enable hemispherical-directional emittance and reflectance measurements versus temperature and angle out to 100 μm.

The use of remotely-sensed wildland fire radiation to infer the fates of carbon during biomass combustion - the need to understand and quantify a fire's mass and energy budget

NASA Astrophysics Data System (ADS)

Dickinson, M. B.; Dietenberger, M.; Ellicott, E. A.; Hardy, C.; Hudak, A. T.; Kremens, R.; Mathews, W.; Schroeder, W.; Smith, A. M.; Strand, E. K.

2016-12-01

Few measurement techniques offer broad-scale insight on the extent and characteristics of biomass combustion during wildland fires. Remotely-sensed radiation is one of these techniques but its measurement suffers from several limitations and, when quantified, its use to derive variables of real interest depends on an understanding of the fire's mass and energy budget. In this talk, we will review certain assumptions of wildland fire radiation measurement and explore the use of those measurements to infer the fates of biomass and the dissipation of combustion energy. Recent measurements show that the perspective of the sensor (nadir vs oblique) matters relative to estimates of fire radiated power. Other considerations for producing accurate estimates of fire radiation from remote sensing include obscuration by an intervening forest canopy and to what extent measurements that are based on the assumption of graybody/blackbody behavior underestimate fire radiation. Fire radiation measurements are generally a means of quantifying other variables and are often not of interest in and of themselves. Use of fire radiation measurements as a means of inference currently relies on correlations with variables of interest such as biomass consumption and sensible and latent heat and emissions fluxes. Radiation is an imperfect basis for these correlations in that it accounts for a minority of combustion energy ( 15-30%) and is not a constant as is often assumed. Measurements suggest that fire convective energy accounts for the majority of combustion energy and (after radiation) is followed by latent energy, soil heating, and pyrolysis energy, more or less in that order. Combustion energy in and of itself is not its potential maximum, but is reduced to an effective heat of combustion by combustion inefficiency and by work done to pyrolyze fuel (important in char production) and in moisture vaporization. The effective heat of combustion is often on the order of 65% of its potential maximum. Through consideration of available data and modeling, we conclude that there is substantial scope to improve the science behind fire radiation measurements and the inferences derived from those measurements.

Dynamics of a Sonoluminescing Bubble in Sulfuric Acid

NASA Astrophysics Data System (ADS)

Hopkins, Stephen D.; Putterman, Seth J.; Kappus, Brian A.; Suslick, Kenneth S.; Camara, Carlos G.

2005-12-01

The spectral shape and observed sonoluminescence emission from Xe bubbles in concentrated sulfuric acid is consistent only with blackbody emission from a spherical surface that fills the bubble. The interior of the observed 7000 K blackbody must be at least 4 times hotter than the emitting surface in order that the equilibrium light-matter interaction length be smaller than the radius. Bright emission is correlated with long emission times (˜10ns), sharp thresholds, unstable translational motion, and implosions that are sufficiently weak that contributions from the van der Waals hard core are small.

Near-Blackbody Enclosed Particle-Receiver Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Zhiwen; Sakadjian, Bartev

2015-12-01

This 3-year project develops a technology using gas/solid, two-phase flow as a heat-transfer fluid and separated, stable, solid particles as a thermal energy storage (TES) medium for a concentrating solar power (CSP) plant, to address the temperature, efficiency, and cost barriers associated with current molten-salt CSP systems. This project focused on developing a near-blackbody particle receiver and an integrated fluidized-bed heat exchanger with auxiliary components to achieve greater than 20% cost reduction over current CSP plants, and to provide the ability to drive high-efficiency power cycles.

Mid-Infrared Spectrum of the Zodiacal Emission: Detection of Crystalline Silicates in Interplanetary Dust

NASA Technical Reports Server (NTRS)

Ootsubo, T.; Onaka, T.; Yamamura, I.; Ishihara, D.; Tanabe, T.; Roellig, T. L.

2003-01-01

Within a few astronomical units of the Sun the solar system is filled with interplanetary dust, which is believed to be dust of cometary and asteroidal origin. Spectroscopic observations of the zodiacal emission with moderate resolution provide key information on the composition and size distribution of the dust in the interplanetary space. They can be compared directly to laboratory measurements of candidate materials, meteorites, and dust particles collected in the stratosphere. Recently mid-infrared spectroscopic observations of the zodiacal emission have been made by two instruments on board the Infrared Space Observatory; the camera (ISOCAM) and the spectrophotometer (ISOPHOT-S). A broad excess emission feature in the 9-11 micron range is reported in the ISOCAM spectrum, whereas the ISOPHOT-S spectra in 6-12 microns can be well fitted by a blackbody radiation without spectral features.

Spatial and Temporal Variabilities of Solar and Longwave Radiation Fluxes below a Coniferous Forest in the French Alps

NASA Astrophysics Data System (ADS)

Sicart, J. E.; Ramseyer, V.; Lejeune, Y.; Essery, R.; Webster, C.; Rutter, N.

2017-12-01

At high altitudes and latitudes, snow has a large influence on hydrological processes. Large fractions of these regions are covered by forests, which have a strong influence on snow accumulation and melting processes. Trees absorb a large part of the incoming shortwave radiation and this heat load is mostly dissipated as longwave radiation. Trees shelter the snow surface from wind, so sub-canopy snowmelt depends mainly on the radiative fluxes: vegetation attenuates the transmission of shortwave radiation but enhances longwave irradiance to the surface. An array of 13 pyranometers and 11 pyrgeometers was deployed on the snow surface below a coniferous forest at the CEN-MeteoFrance Col de Porte station in the French Alps (1325 m asl) during the 2017 winter in order to investigate spatial and temporal variabilities of solar and infrared irradiances in different meteorological conditions. Sky view factors measured with hemispherical photographs at each radiometer location were in a narrow range from 0.2 to 0.3. The temperature of the vegetation was measured with IR thermocouples and an IR camera. In clear sky conditions, the attenuation of solar radiation by the canopy reached 96% and its spatial variability exceeded 100 W m-2. Longwave irradiance varied by 30 W m-2 from dense canopy to gap areas. In overcast conditions, the spatial variabilities of solar and infrared irradiances were reduced and remained closely related to the sky view factor. A simple radiative model taking into account the penetration through the canopy of the direct and diffuse solar radiation, and isotropic infrared emission of the vegetation as a blackbody emitter, accurately reproduced the dynamics of the radiation fluxes at the snow surface. Model results show that solar transmissivity of the canopy in overcast conditions is an excellent proxy of the sky view factor and the emitting temperature of the vegetation remained close to the air temperature in this typically dense Alpine forest.

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rowan, W. L., E-mail: w.l.rowan@austin.utexas.edu; Houshmandyar, S.; Phillips, P. E.

2016-11-15

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct viewmore » of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Blackbody radiation sources are provided for in situ calibration.« less

A Smoking Gun in the Carina Nebula

NASA Technical Reports Server (NTRS)

Hamaguchi, Kenji; Corcoran, Michael F.; Ezoe, Yuichiro; Townsley, Leisa; Broos, Patrick; Gruendl, Robert; Vaidya, Kaushar; White, Stephen M.; Petre, Rob; Chu, You-Hua

2009-01-01

The Carina Nebula is one of thc youngest, most active sites of massive star formation in our Galaxy. In this nebula, we have discovered a bright X-ray source that has persisted for approx.30 years. The soft X-ray spectrum. consistent with kT approx.130 eV blackbody radiation with mild extinction, and no counterpart in the near- and mid-infrared wavelengths indicate that it is a, approx. 10(exp 6)-year-old neutron star housed in the Carina Nebula. Current star formation theory does not suggest that the progenitor of the neutron star and massive stars in the Carina Nebula, in particular (eta)Car, are coeval. This result demonstrates that the Carina Nebula experienced at least two major episodes of massive star formation. The neutron star would be responsible for remnants of high energy activity seen in multiple wavelengths.

Highly Flexible, Multipixelated Thermosensitive Smart Windows Made of Tough Hydrogels.

PubMed

La, Thanh-Giang; Li, Xinda; Kumar, Amit; Fu, Yiyang; Yang, Shu; Chung, Hyun-Joong

2017-09-27

In a cold night, a clear window that will become opaque while retaining the indoor heat is highly desirable for both privacy and energy efficiency. A thermally responsive material that controls both the transmittance of solar radiance (predominantly in the visible and near-infrared wavelengths) and blackbody radiation (mainly in the mid-infrared) can realize such windows with minimal energy consumption. Here, we report a smart coating made from polyampholyte hydrogel (PAH) that transforms from a transparency state to opacity to visible radiation and strengthens opacity to mid-infrared when lowering the temperature as a result of phase separation between the water-rich and polymer-rich phases. To match a typical temperature fluctuation during the day, we fine-tune the phase transition temperature between 25 and 55 °C by introducing a small amount of relatively hydrophobic monomers (0.1 to 0.5 wt % to PAH). To further demonstrate an actively controlled, highly flexible, and high-contrast smart window, we build in an array of electric heaters made of printed elastomeric composite. The multipixelated window offers rapid switching, ∼70 s per cycle, whereas the device can withstand high strain (up to 80%) during operations.

Dynamics of a sonoluminescing bubble in sulfuric acid.

PubMed

Hopkins, Stephen D; Putterman, Seth J; Kappus, Brian A; Suslick, Kenneth S; Camara, Carlos G

2005-12-16

The spectral shape and observed sonoluminescence emission from Xe bubbles in concentrated sulfuric acid is consistent only with blackbody emission from a spherical surface that fills the bubble. The interior of the observed 7000 K blackbody must be at least 4 times hotter than the emitting surface in order that the equilibrium light-matter interaction length be smaller than the radius. Bright emission is correlated with long emission times (approximately 10 ns), sharp thresholds, unstable translational motion, and implosions that are sufficiently weak that contributions from the van der Waals hard core are small.

Standoff detection of explosive substances at distances of up to 150 m.

PubMed

Mukherjee, Anadi; Von der Porten, Steven; Patel, C Kumar N

2010-04-10

We report detection and identification of trace quantities of explosives at standoff distances up to 150 m with high sensitivity (signal-to-noise ratio of approximately 70) and high selectivity. The technique involves illuminating the target object with laser radiation at a wavelength that is strongly absorbed by the target. The resulting temperature rise is observed by remotely monitoring the increased blackbody radiation from the sample. An unambiguous determination of the target, TNT, in soil samples collected from an explosives test site in China Lake Naval Air Weapons Station is achieved through the use of a tunable CO(2) laser that scans over the absorption fingerprint of the target explosives. The theoretical analysis supports the observation and indicates that, with optimized detectors and data processing algorithms, the measurement capability can be improved significantly, permitting rapid standoff detection of explosives at distances approaching 1 km. The detection sensitivity varies as R(-2) and, thus, with the availability of high power, room-temperature, tunable mid-wave infrared and long-wave infrared quantum cascade lasers, this technology may play an important role in screening personnel and their belongings at short distances, such as in airports, for detecting and identifying explosives material residue on persons.

Vacuum Radiance-Temperature Standard Facility for Infrared Remote Sensing at NIM

NASA Astrophysics Data System (ADS)

Hao, X. P.; Song, J.; Xu, M.; Sun, J. P.; Gong, L. Y.; Yuan, Z. D.; Lu, X. F.

2018-06-01

As infrared remote sensors are very important parts of Earth observation satellites, they must be calibrated based on the radiance temperature of a blackbody in a vacuum chamber prior to launch. The uncertainty of such temperature is thus an essential component of the sensors' uncertainty. This paper describes the vacuum radiance-temperature standard facility (VRTSF) at the National Institute of Metrology of China, which will serve to calibrate infrared remote sensors on Chinese meteorological satellites. The VRTSF can be used to calibrate vacuum blackbody radiance temperature, including those used to calibrate infrared remote sensors. The components of the VRTSF are described in this paper, including the VMTBB, the LNBB, the FTIR spectrometer, the reduced-background optical system, the vacuum chamber used to calibrate customers' blackbody, the vacuum-pumping system and the liquid-nitrogen-support system. The experimental methods and results are expounded. The uncertainty of the radiance temperature of VMTBB is 0.026 °C at 30 °C over 10 μm.

Can Flare Loops Contribute to the White-light Emission of Stellar Superflares?

NASA Astrophysics Data System (ADS)

Heinzel, P.; Shibata, K.

2018-06-01

Since the discovery of stellar superflares by the Kepler satellite, these extremely energetic events have been studied in analogy to solar flares. Their white-light (WL) continuum emission has been interpreted as being produced by heated ribbons. In this paper, we compute the WL emission from overlying flare loops depending on their density and temperature and show that, under conditions expected during superflares, the continuum brightening due to extended loop arcades can significantly contribute to stellar flux detected by Kepler. This requires electron densities in the loops of 1012‑1013 cm‑3 or higher. We show that such densities, exceeding those typically present in solar-flare loops, can be reached on M-dwarf and solar-type superflare stars with large starspots and much stronger magnetic fields. Quite importantly, the WL radiation of loops is not very sensitive to their temperature and thus both cool as well as hot loops may contribute. We show that the WL intensity emergent from optically thin loops is lower than the blackbody radiation from flare ribbons, but the contribution of loops to total stellar flux can be quite important due to their significant emitting areas. This new scenario for interpreting superflare emission suggests that the observed WL flux is due to a mixture of the ribbon and loop radiation and can be even loop-dominated during the gradual phase of superflares.

The RAVAN CubeSat Mission: A Pathfinder for a New Measurement of Earth's Radiation Budget

NASA Astrophysics Data System (ADS)

Swartz, W.; Lorentz, S. R.; Huang, P. M.; Smith, A. W.; Deglau, D.; Reynolds, E.; Carvo, J.; Papadakis, S.; Wu, D. L.; Wiscombe, W. J.; Dyrud, L. P.

2016-12-01

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat is a pathfinder for a constellation to measure the Earth's radiation imbalance (ERI), which is the single most important quantity for predicting the course of climate change over the next century. RAVAN demonstrates a small, accurate radiometer that measures top-of-the-atmosphere Earth-leaving fluxes of total and solar-reflected radiation. Coupled with knowledge of the incoming radiation from the Sun, a constellation of such measurements would aim to determine ERI directly. Our objective with RAVAN is to establish that a compact radiometer that is absolutely calibrated to climate accuracy can be built and operated in space for low cost. The radiometer, hosted on a 3U CubeSat, relies on two key technologies. The first is the use of vertically aligned carbon nanotubes (VACNTs) as the radiometer absorber. VACNT forests are some of the blackest materials known and have an extremely flat spectral response over a wide wavelength range. The second key technology is a gallium fixed-point blackbody calibration source, embedded in RAVAN's sensor head contamination cover, that serves as a stable and repeatable reference to track the long-term degradation of the sensor. Absolute calibration is also maintained by regular solar and deep space views. We present the scientific motivation for the NASA-funded mission, design and characterization of the spacecraft, and mission operations concept. Pending a successful launch in fall 2016, we will also present the first results on-orbit. RAVAN will help enable the development of an Earth radiation budget constellation mission that can provide the measurements needed for superior predictions of future climate change.

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

PubMed Central

Zhu, Linxiao; Raman, Aaswath P.; Fan, Shanhui

2015-01-01

A solar absorber, under the sun, is heated up by sunlight. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic for either operational or aesthetic considerations, but the resulting heating is undesirable. Because a solar absorber by necessity faces the sky, it also naturally has radiative access to the coldness of the universe. Therefore, in these applications it would be very attractive to directly use the sky as a heat sink while preserving solar absorption properties. Here we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal. When placed on a silicon absorber under sunlight, such a blackbody preserves or even slightly enhances sunlight absorption, but reduces the temperature of the underlying silicon absorber by as much as 13 °C due to radiative cooling. Our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities. PMID:26392542

Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

DOE PAGES

Zhu, Linxiao; Raman, Aaswath P.; Fan, Shanhui

2015-09-21

A solar absorber, under the sun, is heated up by sunlight. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic for either operational or aesthetic considerations, but the resulting heating is undesirable. Because a solar absorber by necessity faces the sky, it also naturally has radiative access to the coldness of the universe. Therefore, in these applications it would be very attractive to directly use the sky as a heat sink while preserving solar absorption properties. In this paper, we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal. Whenmore » placed on a silicon absorber under sunlight, such a blackbody preserves or even slightly enhances sunlight absorption, but reduces the temperature of the underlying silicon absorber by as much as 13 °C due to radiative cooling. Lastly, our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities.« less

Estimating index of refraction from polarimetric hyperspectral imaging measurements.

PubMed

Martin, Jacob A; Gross, Kevin C

2016-08-08

Current material identification techniques rely on estimating reflectivity or emissivity which vary with viewing angle. As off-nadir remote sensing platforms become increasingly prevalent, techniques robust to changing viewing geometries are desired. A technique leveraging polarimetric hyperspectral imaging (P-HSI), to estimate complex index of refraction, N̂(ν̃), an inherent material property, is presented. The imaginary component of N̂(ν̃) is modeled using a small number of "knot" points and interpolation at in-between frequencies ν̃. The real component is derived via the Kramers-Kronig relationship. P-HSI measurements of blackbody radiation scattered off of a smooth quartz window show that N̂(ν̃) can be retrieved to within 0.08 RMS error between 875 cm^-1 ≤ ν̃ ≤ 1250 cm^-1. P-HSI emission measurements of a heated smooth Pyrex beaker also enable successful N̂(ν̃) estimates, which are also invariant to object temperature.

Fine structure constant and quantized optical transparency of plasmonic nanoarrays.

PubMed

Kravets, V G; Schedin, F; Grigorenko, A N

2012-01-24

Optics is renowned for displaying quantum phenomena. Indeed, studies of emission and absorption lines, the photoelectric effect and blackbody radiation helped to build the foundations of quantum mechanics. Nevertheless, it came as a surprise that the visible transparency of suspended graphene is determined solely by the fine structure constant, as this kind of universality had been previously reserved only for quantized resistance and flux quanta in superconductors. Here we describe a plasmonic system in which relative optical transparency is determined solely by the fine structure constant. The system consists of a regular array of gold nanoparticles fabricated on a thin metallic sublayer. We show that its relative transparency can be quantized in the near-infrared, which we attribute to the quantized contact resistance between the nanoparticles and the metallic sublayer. Our results open new possibilities in the exploration of universal dynamic conductance in plasmonic nanooptics.

Measurement of the cosmic microwave background spectrum by the COBE FIRAS instrument

NASA Technical Reports Server (NTRS)

Mather, J. C.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Fixsen, D. J.; Hewagama, T.; Isaacman, R. B.; Jensen, K. A.; Meyer, S. S.; Noerdlinger, P. D.

1994-01-01

The cosmic microwave background radiation (CMBR) has a blackbody spectrum within 3.4 x 10(exp -8) ergs/sq cm/s/sr cm over the frequency range from 2 to 20/cm (5-0.5 mm). These measurements, derived from the Far-Infrared Absolute Spectrophotomer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite, imply stringent limits on energy release in the early universe after t approximately 1 year and redshift z approximately 3 x 10(exp 6). The deviations are less than 0.30% of the peak brightness, with an rms value of 0.01%, and the dimensionless cosmological distortion parameters are limited to the absolute value of y is less than 2.5 x 10(exp -5) and the absolute value of mu is less than 3.3 x 10(exp -4) (95% confidence level). The temperature of the CMBR is 2.726 +/- 0.010 K (95% confidence level systematic).

Interpretation of the COBE FIRAS CMBR spectrum

NASA Technical Reports Server (NTRS)

Wright, E. L.; Mather, J. C.; Fixsen, D. J.; Kogut, A.; Shafer, R. A.; Bennett, C. L.; Boggess, N. W.; Cheng, E. S.; Silverberg, R. F.; Smoot, G. F.

1994-01-01

The cosmic microwave background radiation (CMBR) spectrum measured by the Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on NASA's Cosmic Background Explorer (COBE) is indistinguishable from a blackbody, implying stringent limits on energy release in the early universe later than the time t = 1 yr after the big bang. We compare the FIRAS data to previous precise measurements of the cosmic microwave background spectrum and find a reasonable agreement. We discuss the implications of the absolute value of y is less than 2.5 x 10(exp -5) and the absolute value of mu is less than 3.3 x 10(exp -4) 95% confidence limits found by Mather et al. (1994) on many processes occurring after t = 1 yr, such as explosive structure formation, reionization, and dissipation of small-scale density perturbations. We place limits on models with dust plus Population III stars, or evolving populations of IR galaxies, by directly comparing the Mather et al. spectrum to the model predictions.

NuSTAR Observations of Magnetar 1E 1841-045

NASA Astrophysics Data System (ADS)

An, Hongjun; Hascoët, Romain; Kaspi, Victoria M.; Beloborodov, Andrei M.; Dufour, François; Gotthelf, Eric V.; Archibald, Robert; Bachetti, Matteo; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Greffenstette, Brian W.; Hailey, Charles J.; Harrison, Fiona A.; Kitaguchi, Takao; Kouveliotou, Chryssa; Madsen, Kristin K.; Markwardt, Craig B.; Stern, Daniel; Vogel, Julia K.; Zhang, William W.

2013-12-01

We report new spectral and temporal observations of the magnetar 1E 1841-045 in the Kes 73 supernova remnant obtained with the Nuclear Spectroscopic Telescope Array. Combined with new Swift and archival XMM-Newton and Chandra observations, the phase-averaged spectrum is well characterized by a blackbody plus double power law, in agreement with previous multimission X-ray results. However, we are unable to reproduce the spectral results reported based on Suzaku observations. The pulsed fraction of the source is found to increase with photon energy. The measured rms pulsed fractions are ~12% and ~17% at ~20 and ~50 keV, respectively. We detect a new feature in the 24-35 keV band pulse profile that is uniquely double peaked. This feature may be associated with a possible absorption or emission feature in the phase-resolved spectrum. We fit the X-ray data using the recently developed electron-positron outflow model by Beloborodov for the hard X-ray emission from magnetars. This produces a satisfactory fit, allowing a constraint on the angle between the rotation and magnetic axes of the neutron star of ~20° and on the angle between the rotation axis and line of sight of ~50°. In this model, the soft X-ray component is inconsistent with a single blackbody; adding a second blackbody or a power-law component fits the data. The two-blackbody interpretation suggests a hot spot of temperature kT ≈ 0.9 keV occupying ~1% of the stellar surface.

Time-dependent, x-ray spectral unfolds and brightness temperatures for intense Li{sup +} ion beam-driven hohlraums

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fehl, D.L.; Chandler, G.A.; Biggs, F.

X-ray-producing hohlraums are being studied as indirect drives for Inertial Confinement Fusion targets. In a 1994 target series on the PBFAII accelerator, cylindrical hohlraum targets were heated by an intense Li{sup +} ion beam and viewed by an array of 13 time-resolved, filtered x-ray detectors (XRDs). The UFO unfold code and its suite of auxiliary functions were used extensively in obtaining time- resolved x-ray spectra and radiation temperatures from this diagnostic. UFO was also used to obtain fitted response functions from calibration data, to simulate data from blackbody x-ray spectra of interest, to determine the suitability of various unfolding parametersmore » (e.g., energy domain, energy partition, smoothing conditions, and basis functions), to interpolate the XRD signal traces, and to unfold experimental data. The simulation capabilities of the code were useful in understanding an anomalous feature in the unfolded spectra at low photon energies ({le} 100 eV). Uncertainties in the differential and energy-integrated unfolded spectra were estimated from uncertainties in the data. The time-history of the radiation temperature agreed well with independent calculations of the wall temperature in the hohlraum.« less

Ground-based remote sensing of thin clouds in the Arctic

NASA Astrophysics Data System (ADS)

Garrett, T. J.; Zhao, C.

2012-11-01

This paper describes a method for using interferometer measurements of downwelling thermal radiation to retrieve the properties of single-layer clouds. Cloud phase is determined from ratios of thermal emission in three "micro-windows" where absorption by water vapor is particularly small. Cloud microphysical and optical properties are retrieved from thermal emission in two micro-windows, constrained by the transmission through clouds of stratospheric ozone emission. Assuming a cloud does not approximate a blackbody, the estimated 95% confidence retrieval errors in effective radius, visible optical depth, number concentration, and water path are, respectively, 10%, 20%, 38% (55% for ice crystals), and 16%. Applied to data from the Atmospheric Radiation Measurement program (ARM) North Slope of Alaska - Adjacent Arctic Ocean (NSA-AAO) site near Barrow, Alaska, retrievals show general agreement with ground-based microwave radiometer measurements of liquid water path. Compared to other retrieval methods, advantages of this technique include its ability to characterize thin clouds year round, that water vapor is not a primary source of retrieval error, and that the retrievals of microphysical properties are only weakly sensitive to retrieved cloud phase. The primary limitation is the inapplicability to thicker clouds that radiate as blackbodies.

The Scaled SLW model of gas radiation in non-uniform media based on Planck-weighted moments of gas absorption cross-section

NASA Astrophysics Data System (ADS)

Solovjov, Vladimir P.; Andre, Frederic; Lemonnier, Denis; Webb, Brent W.

2018-02-01

The Scaled SLW model for prediction of radiation transfer in non-uniform gaseous media is presented. The paper considers a new approach for construction of a Scaled SLW model. In order to maintain the SLW method as a simple and computationally efficient engineering method special attention is paid to explicit non-iterative methods of calculation of the scaling coefficient. The moments of gas absorption cross-section weighted by the Planck blackbody emissive power (in particular, the first moment - Planck mean, and first inverse moment - Rosseland mean) are used as the total characteristics of the absorption spectrum to be preserved by scaling. Generalized SLW modelling using these moments including both discrete gray gases and the continuous formulation is presented. Application of line-by-line look-up table for corresponding ALBDF and inverse ALBDF distribution functions (such that no solution of implicit equations is needed) ensures that the method is flexible and efficient. Predictions for radiative transfer using the Scaled SLW model are compared to line-by-line benchmark solutions, and predictions using the Rank Correlated SLW model and SLW Reference Approach. Conclusions and recommendations regarding application of the Scaled SLW model are made.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahlgren, Björn; Larsson, Josefin; Nymark, Tanja

The origin of the prompt emission in gamma-ray bursts (GRBs) is still an unsolved problem and several different mechanisms have been suggested. We fit Fermi GRB data with a photospheric emission model which includes dissipation of the jet kinetic energy below the photosphere. The resulting spectra are dominated by Comptonization and contain no significant contribution from synchrotron radiation. In order to fit to the data, we span a physically motivated part of the model's parameter space and create DREAM (Dissipation with Radiative Emission as A table Model), a table model for XSPEC. Here, we show that this model can describemore » different kinds of GRB spectra, including GRB 090618, representing a typical Band function spectrum, and GRB 100724B, illustrating a double peaked spectrum, previously fitted with a Band+blackbody model, suggesting they originate from a similar scenario. We also suggest that the main difference between these two types of bursts is the optical depth at the dissipation site.« less

Intercomparison of Laboratory Radiance Calibration Standards

NASA Technical Reports Server (NTRS)

Pavri, Betina; Chrien, Tom; Green, Robert; Williams, Orlesa

2000-01-01

Several standards for radiometric calibration were measured repeatedly with a spectroradiometer in order to understand how they compared in accuracy and stability. The tested radiance standards included a NIST 1000 W bulb and halon panel, two calibrated and stabilized integrating spheres, and a cavity blackbody. Results indicate good agreement between the blackbody and 1000 W bulb/spectralon panel, If these two radiance sources are assumed correct, then the integrating spheres did not conform. to their manufacturer-reported radiances in several regions of the spectrum. More detailed measurements am underway to investigate the discrepancy.

A radiatively pumped CW CO2 laser

NASA Technical Reports Server (NTRS)

Insuik, R. J.; Christiansen, W. H.

1984-01-01

A proof of principle experiment to demonstrate the physics of a radiatively pumped laser has been carried out. For the first time, a blackbody cavity has optically pumped a CW CO2 laser. Results are presented from a series of experiments using mixtures of CO2, He, and Ar in which maximum output power was obtained with a 20 percent CO2-15 percent He-65 percent Ar mixture. The dependence of the output power on the blackbody temperature and the cooling gas flow rate is also discussed. By appropriately varying these parameters, continuous output powers of 8-10 mW have been achieved.

Predicting tropical cyclone intensity using satellite measured equivalent blackbody temperatures of cloud tops. [regression analysis

NASA Technical Reports Server (NTRS)

Gentry, R. C.; Rodgers, E.; Steranka, J.; Shenk, W. E.

1978-01-01

A regression technique was developed to forecast 24 hour changes of the maximum winds for weak (maximum winds less than or equal to 65 Kt) and strong (maximum winds greater than 65 Kt) tropical cyclones by utilizing satellite measured equivalent blackbody temperatures around the storm alone and together with the changes in maximum winds during the preceding 24 hours and the current maximum winds. Independent testing of these regression equations shows that the mean errors made by the equations are lower than the errors in forecasts made by the peristence techniques.

Improved Blackbody Temperature Sensors for a Vacuum Furnace

NASA Technical Reports Server (NTRS)

Farmer, Jeff; Coppens, Chris; O'Dell, J. Scott; McKechnie, Timothy N.; Schofield, Elizabeth

2009-01-01

Some improvements have been made in the design and fabrication of blackbody sensors (BBSs) used to measure the temperature of a heater core in a vacuum furnace. Each BBS consists of a ring of thermally conductive, high-melting-temperature material with two tantalum-sheathed thermocouples attached at diametrically opposite points. The name "blackbody sensor" reflects the basic principle of operation. Heat is transferred between the ring and the furnace heater core primarily by blackbody radiation, heat is conducted through the ring to the thermocouples, and the temperature of the ring (and, hence, the temperature of the heater core) is measured by use of the thermocouples. Two main requirements have guided the development of these BBSs: (1) The rings should have as high an emissivity as possible in order to maximize the heat-transfer rate and thereby maximize temperature-monitoring performance and (2) the thermocouples must be joined to the rings in such a way as to ensure long-term, reliable intimate thermal contact. The problem of fabricating a BBS to satisfy these requirements is complicated by an application-specific prohibition against overheating and thereby damaging nearby instrumentation leads through the use of conventional furnace brazing or any other technique that involves heating the entire BBS and its surroundings. The problem is further complicated by another application-specific prohibition against damaging the thin tantalum thermocouple sheaths through the use of conventional welding to join the thermocouples to the ring. The first BBS rings were made of graphite. The tantalum-sheathed thermocouples were attached to the graphite rings by use of high-temperature graphite cements. The ring/thermocouple bonds thus formed were found to be weak and unreliable, and so graphite rings and graphite cements were abandoned. Now, each BBS ring is made from one of two materials: either tantalum or a molybdenum/titanium/zirconium alloy. The tantalum-sheathed thermocouples are bonded to the ring by laser brazing. The primary advantage of laser brazing over furnace brazing is that in laser brazing, it is possible to form a brazed connection locally, without heating nearby parts to the flow temperature of the brazing material. Hence, it is possible to comply with the prohibition against overheating nearby instrumentation leads. Also, in laser brazing, unlike in furnace brazing, it is possible to exert control over the thermal energy to such a high degree that it becomes possible to braze the thermocouples to the ring without burning through the thin tantalum sheaths on the thermocouples. The brazing material used in the laser brazing process is a titanium-boron paste. This brazing material can withstand use at temperatures up to about 1,400 C. In thermal-cycling tests performed thus far, no debonding between the rings and thermocouples has been observed. Emissivity coatings about 0.001 in. (.0.025 mm) thick applied to the interior surfaces of the rings have been found to improve the performance of the BBS sensors by raising the apparent emissivities of the rings. In thermal-cycling tests, the coatings were found to adhere well to the rings.

Measurement and evaluation of the radiative properties of a thin solid fuel

NASA Technical Reports Server (NTRS)

Pettegrew, Richard; Street, Kenneth; Pitch, Nancy; Tien, James; Morrison, Phillip

2003-01-01

Accurate modeling of combustion systems requires knowledge of the radiative properties of the system. Gas phase properties are well known, but detailed knowledge of surface properties is limited. Recent work has provided spectrally resolved data for some solid fuels, but only for the unburned material at room temperature, and for limited sets of previously burned and quenched samples. Due to lack of knowledge of the spectrally resolved properties at elevated temperatures, as well as processing limitations in the modeling effort, graybody values are typically used for the fuels surface radiative properties. However, the spectrally resolved properties for the fuels at room temperature can be used to give a first-order correction for temperature effects on the graybody values. Figure 1 shows a sample of the spectrally resolved emittance/absorptance for a thin solid fuel of the type commonly used in combustion studies, from approximately 2 to 20 microns. This plot clearly shows a strong spectral dependence across the entire range. By definition, the emittance is the ratio of the emitted energy to that of a blackbody at the same temperature. Therefore, to determine a graybody emittance for this material, the spectrally resolved data must be applied to a blackbody curve. The total area under the resulting curve is ratioed to the total area under the blackbody curve to yield the answer. Due to the asymmetry of the spectrally resolved emittance and the changing shape of the blackbody curve as the temperature increases, the relative importance of the emittance value at any given wavelength will change as a function of temperature. Therefore, the graybody emittance value for a given material will change as a function of temperature even if the spectral dependence of the radiative properties remains unchanged. This is demonstrated in Figures 2 and 3, which are plots of the spectrally resolved emittance for KimWipes (shown in Figure 1) multiplied by the blackbody curves for 300 K (Figure 2) and 800 K (Figure 3). Each figure also shows the blackbody curve for that temperature. Ratioing the areas under the curve for each of these figures give a graybody emittance of 0.64 at 300 K, and 0.46 at 800 K. It is recognized that materials undergoing pyrolysis will change in composition as they heat up, and that the radiative properties of the materials may have inherent temperature dependence. Both of these effects will contribute to changes in the radiative characteristics of a given material, and are not accounted for here. However, this paper demonstrates the temperature dependence of graybody radiative properties, and provides a method for a first-order correction (for temperature) to the graybody values if the spectrally resolved properties are known.

Tandem mass spectrometry of large biomolecule ions by blackbody infrared radiative dissociation.

PubMed

Price, W D; Schnier, P D; Williams, E R

1996-03-01

A new method for the dissociation of large ions formed by electrospray ionization is demonstrated. Ions trapped in a Fourier transform mass spectrometer at pressures below 10(-)(8) Torr are dissociated by elevating the vacuum chamber to temperatures up to 215 °C. Rate constants for dissociation are measured and found to be independent of pressure below 10(-)(7) Torr. This indicates that the ions are activated by absorption of blackbody radiation emitted from the chamber walls. Dissociation efficiencies as high as 100% are obtained. There is no apparent mass limit to this method; ions as large as ubiquitin (8.6 kDa) are readily dissociated. Thermally stable ions, such as melittin 3+ (2.8 kDa), did not dissociate at temperatures up to 200 °C. This method is highly selective for low-energy fragmentation, from which limited sequence information can be obtained. From the temperature dependence of the dissociation rate constants, Arrhenius activation energies in the low-pressure limit are obtained. The lowest energy dissociation processes for the singly and doubly protonated ions of bradykinin are loss of NH(3) and formation of the b(2)/y(7) complementary pair, with activation energies of 1.3 and 0.8 eV, respectively. No loss of NH(3) is observed for the doubly protonated ion; some loss of H(2)O occurs. These results show that charge-charge interactions not only lower the activation energy for dissociation but also can dramatically change the fragmentation, most likely through changes in the gas-phase conformation of the ion. Dissociation of ubiquitin ions produces fragmentation similar to that obtained by IRMPD and SORI-CAD. Higher charge state ions dissociate to produce y and b ions; the primary fragmentation process for low charge state ions is loss of H(2)O.

The Candela and Photometric and Radiometric Measurements

PubMed Central

Parr, Albert C.

2001-01-01

The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements. PMID:27500020

A carbon dioxide radiance model of the earth planet using the conical earth sensor data

NASA Astrophysics Data System (ADS)

Deng, Loulou; Mei, Zhiwu; Tu, Zhijun; Yuan, Jun; He, Ting; Wei, Yi

2013-10-01

Climate Modeling results show that about 50% of the Earth's outgoing radiation and 75% of the atmospheric outgoing radiation are contained in the far infrared. Generally the earth is considered as a 220~230 K blackbody, and the peak breadth of the Earth's outgoing radiation is around the wavelength of 10 micron. The atmospheric outgoing radiation are contained with five spectral intervals: the water vapor band from 6.33 to 6.85 microns, the ozone band from 8.9 to 10.1microns, the atmospheric window from 10.75 to 11.75 microns, the carbon dioxide band from 14 to 16 microns, and finally the rotational water vapor band from 21 to 125 microns. The properties of the carbon dioxide band is stable than other bands which has been chosen for the work Spectrum of the earth sensors. But the radiation energy of carbon dioxide band is variety and it is a function of latitude, season and weather conditions. Usually the luminance of the Earth's radiation (14 to 16 μm) is from 3 to 7 W/m2Sr. Earth sensor is an important instrument of the Attitude and Orbit Control System (AOCS), and it is sensitive to the curve of the earth's and atmospheric outgoing radiation profile to determine the roll and pitch angles of satellite which are relative to nadir vector. Most earth sensors use profile data gathered form Project Scanner taken in August and December 1966. The earth sensor referred in this paper is the conical scanning earth sensor which is mainly used in the LEO (Low Earth Orbit) satellite. A method to determine the luminance of earth's and atmospheric outgoing radiation (carbon dioxide) using the earth sensor is discussed in this paper. When the conical scanning sensor scan form the space to the earth, a pulse is produced and the pulse breadth is scale with the infrared radiation luminance. Then the infrared radiation luminance can be calculated. A carbon dioxide radiance model of the earth's and atmospheric outgoing radiation is obtained according the luminance data about with different latitudes and seasons which are measured form the conical scanning earth sensors of ZY-1 satellite. When the carbon dioxide radiance model has been collected, it can be fed directly to the earth sensors to improve their accuracy. It also can be supplied for the research of the content and distribution of carbon dioxide in the atmosphere.

An improved electrical and thermal model of a microbolometer for electronic circuit simulation

NASA Astrophysics Data System (ADS)

Würfel, D.; Vogt, H.

2012-09-01

The need for uncooled infrared focal plane arrays (IRFPA) for imaging systems has increased since the beginning of the nineties. Examples for the application of IRFPAs are thermography, pedestrian detection for automotives, fire fighting, and infrared spectroscopy. It is very important to have a correct electro-optical model for the simulation of the microbolometer during the development of the readout integrated circuit (ROIC) used for IRFPAs. The microbolometer as the sensing element absorbs infrared radiation which leads to a change of its temperature due to a very good thermal insulation. In conjunction with a high temperature coefficient of resistance (TCR) of the sensing material (typical vanadium oxide or amorphous silicon) this temperature change results in a change of the electrical resistance. During readout, electrical power is dissipated in the microbolometer, which increases the temperature continuously. The standard model for the electro-optical simulation of a microbolometer includes the radiation emitted by an observed blackbody, radiation emitted by the substrate, radiation emitted by the microbolometer itself to the surrounding, a heat loss through the legs which connect the microbolometer electrically and mechanically to the substrate, and the electrical power dissipation during readout of the microbolometer (Wood, 1997). The improved model presented in this paper takes a closer look on additional radiation effects in a real IR camera system, for example the radiation emitted by the casing and the lens. The proposed model will consider that some parts of the radiation that is reflected from the casing and the substrate is also absorbed by the microbolometer. Finally, the proposed model will include that some fraction of the radiation is transmitted through the microbolometer at first and then absorbed after the reflection at the surface of the substrate. Compared to the standard model temperature and resistance of the microbolometer can be modelled more realistically when these higher order effects are taken into account. A Verilog-A model for electronic circuit simulations is developed based on the improved thermal model of the microbolometer. Finally, a simulation result of a simple circuit is presented.

Infrared radiation from hot Jupiters

NASA Astrophysics Data System (ADS)

Deming, D.; Richardson, L. J.; Seager, S.; Harrington, J.

2006-02-01

Recent Spitzer infrared (IR) observations of two transiting hot Jupiters during their secondary eclipses have provided the first direct detection of planets orbiting other stars (Charbonneau et al. 2005, ApJ 626, 523; Deming et al. 2005, Nature 434, 740). We here elaborate on some aspects of our detection of HD 209458b at 24 μm, and we compare to the detection of TrES-1 by Charbonneau et al. Spitzer will eventually determine the IR spectral energy distribution of these and similar hot Jupiters, opening the new field of comparative exoplanetology. For now, we have only three Spitzer data points, augmented by upper limits from the ground. We here interpret the available measurements from a purely observational perspective, and we point out that a blackbody spectrum having T ˜ 1100K can account for all current IR measurements, within the errors. This will surely not remain true for long, since ongoing Spitzer observations will be very sensitive to the IR characteristics of hot Jupiters.

Quantum-secure covert communication on bosonic channels.

PubMed

Bash, Boulat A; Gheorghe, Andrei H; Patel, Monika; Habif, Jonathan L; Goeckel, Dennis; Towsley, Don; Guha, Saikat

2015-10-19

Computational encryption, information-theoretic secrecy and quantum cryptography offer progressively stronger security against unauthorized decoding of messages contained in communication transmissions. However, these approaches do not ensure stealth--that the mere presence of message-bearing transmissions be undetectable. We characterize the ultimate limit of how much data can be reliably and covertly communicated over the lossy thermal-noise bosonic channel (which models various practical communication channels). We show that whenever there is some channel noise that cannot in principle be controlled by an otherwise arbitrarily powerful adversary--for example, thermal noise from blackbody radiation--the number of reliably transmissible covert bits is at most proportional to the square root of the number of orthogonal modes (the time-bandwidth product) available in the transmission interval. We demonstrate this in a proof-of-principle experiment. Our result paves the way to realizing communications that are kept covert from an all-powerful quantum adversary.

Development of InSb charge-coupled infrared imaging devices: Linear imager

NASA Technical Reports Server (NTRS)

Phillips, J. D.

1976-01-01

The following results were accomplished in the development of charge coupled infrared imaging devices: (1) a four-phase overlapping gate with 9 transfers (2-bits) and 1.0-mil gate lengths was successfully operated, (2) the measured transfer efficiency of 0.975 for this device is in excellent agreement with predictions for the reduced gate length device, (3) mask revisions of the channel stop metal on the 8582 mask have been carried out with the result being a large increase in the dc yield of the tested devices, (4) partial optical sensitivity to chopped blackbody radiation was observed for an 8582 9-bit imager, (5) analytical consideration of the modulation transfer function degradation caused by transfer inefficiency in the CCD registers was presented, and (6) for larger array lengths or for the insertion of isolated bits between sensors, improvements in InSb fabrication technology with corresponding decrease in the interface state density are required.

100 years of photometry and radiometry

NASA Astrophysics Data System (ADS)

Hardis, Jonathan E.

2001-06-01

Measurement of light is an old subject, though the past 100 years have seen significant advances. 100 years ago, photometry - the art and science of measuring light as it is perceived by people - had the greater technological importance. Even today SI (the metric system) retains a base unit for photometry, the candela. However, early work at NBS included pivotal projects in the field of radiometry - the measurement of the physical characteristics of light. These included the validation of Planck's newly-minted theory of blackbody radiation, determining the radiation constants with good accuracy, and the definitive analysis of the spectral responsivity of human vision, so as to relate photometry to radiometry. This latter work has only increased in importance over the past 75 years as the definition of the candela has changed and improved. Today, NIST makes radiometric, and hence photometric measurements, with unprecedented precision. Cryogenic radiometers based on the principle of electrical substitution measure optical flux with uncertainties of 0.02%. Additional facilities enable measurement of spectral responsivity, spectral radiance, and spectral irradiance. Novel detectors, such as light-traps, allow the best accuracy to be transferred from the primary standards to routinely-used instruments and to calibration customers. Filtered detectors are used to realize photometric scales, radiation temperature scales, and other specialized measurements. Indeed, the story of the metrology of light is the story of continuous improvement, both driven by and enabled by advances in technology. We touch upon some of these as a prelude to the other talks in this Conference.

Radiometric traceability diagnosis and bias correction for the Suomi NPP VIIRS long-wave infrared channels during blackbody unsteady states

NASA Astrophysics Data System (ADS)

Cao, Changyong; Wang, Wenhui; Blonski, Slawomir; Zhang, Bin

2017-05-01

The Suomi National Polar-orbiting Partnership Program (NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Thermal Emissive Bands (TEBs) have been performing well since the data became available on 20 January 2012, and the Sensor Data Record data reached validated maturity on 18 March 2014. While overall the validation has shown that these channels have an estimated absolute uncertainty on the order of 0.1 K based on extensive comparisons, there is a remaining issue that persisted over the years. A calibration bias on the order of 0.1 K is introduced in channels such as M15 during the quarterly blackbody temperature warm-up/cooldown, and the bias is further amplified by the sea surface temperature (SST) retrieval algorithm up to 0.3 K in the global daily-averaged products which causes an apparent spike in the SST time series. Our investigation reveals that this bias is caused by a fundamental but flawed theoretical assumption in the VIIRS calibration equation, which states that the shape of the calibration curve is assumed unchanged from prelaunch to postlaunch without any constrains. While the assumption may work to account for long-term degradation, it has a shortcoming during the blackbody unsteady state. In this study, we present a diagnostic and correction method with a compensatory term (Ltrace) to reconcile the assumption such that it removes the calibration bias during the blackbody temperature changes. The methodology has been tested using historical data, and the results are very positive. The implementation has minimal impacts on the operational data processing system and is readily available for use in operations.

Should Tungsten Ribbon Lamps Be Replaced or Not?

NASA Astrophysics Data System (ADS)

Matveyev, M. S.; Pokhodun, A. I.; Sild, Yu. A.

2003-09-01

Tungsten ribbon lamps are the most frequently used means in the temperature range higher than 800 °C for reproduction and precise transfer of a temperature scale by non-contact methods. Lamps have many advantages: a very high reproducibility, stability and durability; use of a lamp over dozens of years with careful and correct operation; and relative simplicity of operation, storage and transportation. The direct correlation of temperature and current through a ribbon enables us to use the advantages of electrical measurements. At the same time lamps have also a number of negative features. Small deviations from the prescribed procedure can lead to unpredictable changes of the performance of a lamp and, even, to irreversible changes of its parameters. The important factor of the quality of transferring the temperature scale is the propinquity of the transferred temperature to the thermodynamic one. Only this factor guarantees the accuracy and unity of temperature measurements of temperature by instruments applying different principles of operation and various designs. However, this is the quality that the lamps do not possess. Their main drawback is selectivity of radiation stipulated by the spectral dependence of emissivity. That is why it is necessary to replace them with blackbodies, which let us rely completely on the definition of the ITS-90. Several years ago at our institute we started investigations on development of special measuring instruments, in which a sensor was located around a miniature blackbody. The aperture of this blackbody could be used as a standard emitter, which temperature was accurately determined by a resistance thermometer. Applying also a standard pyrometer, we refined the reference function of a platinum resistor in the range between the Ag and Cu fixed points. To extend the temperature range up to 1450 °C to 1500 °C we built an instrument in the form of a miniature blackbody made of Pd which was connected to three platinum wires forming Pt-Pd thermocouples. Then we built a similar device made of Pt-Rh alloy. It gave us an opportunity to reach the temperatures up to 1600 to 1700 °C. Having the maximal diameter 8 mm, about 35 mm length and a radiating aperture of diameter 1.8 mm, the device had emissivity about 0.9994, and it was suitable for transfer of the temperature scale, without using conditional temperatures. Its small dimensions allowed for applying it also as a temperature-measuring instrument using the well known and developed contact methods. We discuss in the paper whether such instrument equipped with a simple heater would compete with lamps.

Characterization of a quantum cascade laser-based emissivity monitor for CORSAIR

NASA Astrophysics Data System (ADS)

Lwin, Maung; Wojcik, Michael; Latvakoski, Harri; Scott, Deron; Watson, Mike; Marchant, Alan; Topham, Shane; Mlynczak, Martin

2011-06-01

Continuous improvements of quantum cascade laser (QCL) technology have extended the applications in environmental trace gas monitoring, mid-infrared spectroscopy in medicine and life science, law enforcement and homeland security and satellite sensor systems. We present the QCL based emissivity monitor for the CORSAIR blackbody. The emissivity of the blackbody was designed to be better than 0.9999 for the spectral range between 5 to 50μm. To actively monitor changes in blackbody emissivity we employ a QCL-based infrared illumination source. The illumination source consisted of a QCL and thermoelectric cooler (TEC) unit mounted on a copper fixture. The stability of the QCL was measured for 30, 60, and 90s operation time at 1.5A driving current. The temperature distribution along the laser mounting fixture and time dependent system heat dispersion were analyzed. The results were compared to radiative and conductive heat transfer models to define the potential laser operating time and required waiting time to return to initial temperature of the laser mount. The observed cooling behaviour is consistent with a primarily conductive heat transfer mechanism.

Effective emissivities of isothermal blackbody cavities calculated by the Monte Carlo method using the three-component bidirectional reflectance distribution function model.

PubMed

Prokhorov, Alexander

2012-05-01

This paper proposes a three-component bidirectional reflectance distribution function (3C BRDF) model consisting of diffuse, quasi-specular, and glossy components for calculation of effective emissivities of blackbody cavities and then investigates the properties of the new reflection model. The particle swarm optimization method is applied for fitting a 3C BRDF model to measured BRDFs. The model is incorporated into the Monte Carlo ray-tracing algorithm for isothermal cavities. Finally, the paper compares the results obtained using the 3C model and the conventional specular-diffuse model of reflection.

Blackbody Emission from Laser Breakdown in High-Pressure Gases

NASA Astrophysics Data System (ADS)

Bataller, A.; Plateau, G. R.; Kappus, B.; Putterman, S.

2014-08-01

Laser induced breakdown of pressurized gases is used to generate plasmas under conditions where the atomic density and temperature are similar to those found in sonoluminescing bubbles. Calibrated streak spectroscopy reveals that a blackbody persists well after the exciting femtosecond laser pulse has turned off. Deviation from Saha's equation of state and an accompanying large reduction in ionization potential are observed at unexpectedly low atomic densities—in parallel with sonoluminescence. In laser breakdown, energy input proceeds via excitation of electrons whereas in sonoluminescence it is initiated via the atoms. The similar responses indicate that these systems are revealing the thermodynamics and transport of a strongly coupled plasma.

Design of two blackbody sources for millimeter and sub-millimeter wave Fourier transform spectrometry

NASA Astrophysics Data System (ADS)

Colin, Angel

2014-03-01

This paper describes an experimental setup for the spectral calibration of bolometric detectors used in radioastronomy. The system is composed of a Martin-Puplett interferometer with two identical artificial blackbody sources operating in the vacuum mode at 77 K and 300 K simultaneously. One source is integrated into a liquid nitrogen cryostat, and the other one into a vacuum chamber at room temperature. The sources were designed with a combination of conical with cylindrical geometries thus forming an orthogonal configuration to match the internal optics of the interfermometer. With a simple mathematical model we estimated emissivities of ε 0.995 for each source.

A Blackbody Microwave Source for CMB Polarimeter Development

NASA Astrophysics Data System (ADS)

Lindman, Alec

2014-03-01

I present an evolved design for a thermally isolated blackbody source operating at 90 GHz and 120 GHz, frequencies of interest to Cosmic Microwave Background measurements. The NASA GSFC Experimental Cosmology lab is developing transition edge sensor bolometers for the CLASS and PIPER missions to measure CMB polarization; the source described here is for use in an existing 150 mK test package to quantify the detectors' properties. The design is optimized to minimize heat loading into the ADR and cryocoolers by employing a Kevlar kinematic suspension and additional thermal breaks. The blackbody light is coupled to a detector by means of an electroformed waveguide, which is mated to the source by an ultraprecise ring-centered flange design; this precision is critical to maintain the vacuum gap between the heated source and the cold waveguide, which is an order of magnitude smaller than the allowable misalignment of the standard military-spec microwave flange design. The source will provide at least 50% better thermal isolation than the existing 40 GHz source, as well as a smaller thermal time constant to enable faster measurement cycles. Special thanks to Dr. David Chuss at GSFC, and the Society of Physics Students.

Energy Spectra and High Frequency Oscillations in 4U 0614+091

NASA Technical Reports Server (NTRS)

Ford, E. C.; Kaaret, P.; Chen, K.; Tavani, M.; Barret, D.; Bloser, P.; Grindlay, J.; Harmon, B. A.; Paciesas, W. S.; Zhang, S. N.

1997-01-01

We investigate the behavior of the high frequency quasi-periodic oscillations (QPOs) in 4U 0614+091, combining timing and spectral analysis of RXTE (Rossi X-ray Timing Explorer) observations. The energy spectrum of the source can be described by a power law plus a blackbody component. The blackbody has a variable temperature (kT approximately 0.8 to 1.4 keV) and accounts for 10 to 25% of the total energy flux. The power law flux and photon index also vary (F approximately 0.8 to 1.6 x 10(exp -9) erg/sq cm.s and alpha approximately 2.0 to 2.8 respectively). We find a robust correlation of the frequency of the higher frequency QPO with the flux of the blackbody. The source follows the same relation even in observations separated by several months. The QPO frequency does not have a similarly unique correlation with the total flux or the flux of the power law component. The RMS amplitudes of the higher frequency QPO rise with energy but are consistent with a constant for the lower frequency QPO. These results may be interpreted in terms of a beat frequency model for the production of the high frequency QPOs.

Ground-based atmospheric water vapor monitoring system with spectroscopy of radiation in 20-30 GHz and 50-60 GHz bands

NASA Astrophysics Data System (ADS)

Nagasaki, Takeo; Tajima, Osamu; Araki, Kentaro; Ishimoto, Hiroshi

2016-07-01

We propose a novel ground-based meteorological monitoring system. In the 20{30 GHz band, our system simultaneously measures a broad absorption peak of water vapor and cloud liquid water. Additional observation in the 50{60 GHz band obtains the radiation of oxygen. Spectral results contain vertical profiles of the physical temperature of atmospheric molecules. We designed a simple method for placing the system atop high buildings and mountains and on decks of ships. There is a simple optical system in front of horn antennas for each frequency band. A focused signal from a reflector is separated into two polarized optical paths by a wire grid. Each signal received by the horn antenna is amplified by low-noise amplifiers. Spectra of each signal are measured as a function of frequency using two analyzers. A blackbody calibration source is maintained at 50 K in a cryostat. The calibration signal is led to each receiver via the wire grid. The input path of the signal is selected by rotation of the wire grid by 90°, because the polarization axis of the reflected path and axis of the transparent path are orthogonal. We developed a prototype receiver and demonstrated its performance using monitoring at the zenith.

The rank correlated FSK model for prediction of gas radiation in non-uniform media, and its relationship to the rank correlated SLW model

NASA Astrophysics Data System (ADS)

Solovjov, Vladimir P.; Webb, Brent W.; Andre, Frederic

2018-07-01

Following previous theoretical development based on the assumption of a rank correlated spectrum, the Rank Correlated Full Spectrum k-distribution (RC-FSK) method is proposed. The method proves advantageous in modeling radiation transfer in high temperature gases in non-uniform media in two important ways. First, and perhaps most importantly, the method requires no specification of a reference gas thermodynamic state. Second, the spectral construction of the RC-FSK model is simpler than original correlated FSK models, requiring only two cumulative k-distributions. Further, although not exhaustive, example problems presented here suggest that the method may also yield improved accuracy relative to prior methods, and may exhibit less sensitivity to the blackbody source temperature used in the model predictions. This paper outlines the theoretical development of the RC-FSK method, comparing the spectral construction with prior correlated spectrum FSK method formulations. Further the RC-FSK model's relationship to the Rank Correlated Spectral Line Weighted-sum-of-gray-gases (RC-SLW) model is defined. The work presents predictions using the Rank Correlated FSK method and previous FSK methods in three different example problems. Line-by-line benchmark predictions are used to assess the accuracy.

Time-dependent, x-ray spectral unfolds and brightness temperatures for intense Li{sup +} ion beam-driven hohlraums

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fehl, D.L.; Chandler, G.A.; Biggs, F.

X-ray-producing hohlraums are being studied as indirect drives for inertial confinement fusion targets. In a 1994 target series on the PBFAII accelerator, cylindrical hohlraum targets were heated by an intense Li{sup +} ion beam and viewed by an array of 13 time-resolved, filtered x-ray detectors (XRDs). The unfold operator (UFO) code and its suite of auxiliary functions were used extensively in obtaining time-resolved x-ray spectra and radiation temperatures from this diagnostic. The UFO was also used to obtain fitted response functions from calibration data, to simulate data from blackbody x-ray spectra of interest, to determine the suitability of various unfoldingmore » parameters (e.g., energy domain, energy partition, smoothing conditions, and basis functions), to interpolate the XRD signal traces, and to unfold experimental data. The simulation capabilities of the code were useful in understanding an anomalous feature in the unfolded spectra at low photon energies ({le}100 eV). Uncertainties in the differential and energy-integrated unfolded spectra were estimated from uncertainties in the data. The time{endash}history of the radiation temperature agreed well with independent calculations of the wall temperature in the hohlraum. {copyright} {ital 1997 American Institute of Physics.}« less

Observations of cataclysmic variables with IUE

NASA Technical Reports Server (NTRS)

Hartmann, L.; Raymond, J.

1981-01-01

Observations are reported of the cataclysmic variables AN UMa, 2AO311-227, VV Pup, DQ Her, and GK Per. Continuum emission was detected in the short wavelength region in DQ Her. This object exhibits a quasi-blackbody spectrum at short wavelengths, such blackbody components are a common property of the variables AM Her, SS Cyg, and U Gem, suggesting an underlying similarity in the activity of these diverse systems. Flat continuum components at longer wavelengths in general are not compatible with standard disk models. The emission line ratios in AE Aqr are anomalous in that C IV is absent to a very low level relative to N V.

Blackbody emission from laser breakdown in high-pressure gases.

PubMed

Bataller, A; Plateau, G R; Kappus, B; Putterman, S

2014-08-15

Laser induced breakdown of pressurized gases is used to generate plasmas under conditions where the atomic density and temperature are similar to those found in sonoluminescing bubbles. Calibrated streak spectroscopy reveals that a blackbody persists well after the exciting femtosecond laser pulse has turned off. Deviation from Saha's equation of state and an accompanying large reduction in ionization potential are observed at unexpectedly low atomic densities-in parallel with sonoluminescence. In laser breakdown, energy input proceeds via excitation of electrons whereas in sonoluminescence it is initiated via the atoms. The similar responses indicate that these systems are revealing the thermodynamics and transport of a strongly coupled plasma.

A new method of field MRTD test

NASA Astrophysics Data System (ADS)

Chen, Zhibin; Song, Yan; Liu, Xianhong; Xiao, Wenjian

2014-09-01

MRTD is an important indicator to measure the imaging performance of infrared camera. In the traditional laboratory test, blackbody is used as simulated heat source which is not only expensive and bulky but also difficult to meet field testing requirements of online automatic infrared camera MRTD. To solve this problem, this paper introduces a new detection device for MRTD, which uses LED as a simulation heat source and branded plated zinc sulfide glass carved four-bar target as a simulation target. By using high temperature adaptability cassegrain collimation system, the target is simulated to be distance-infinite so that it can be observed by the human eyes to complete the subjective test, or collected to complete objective measurement by image processing. This method will use LED to replace blackbody. The color temperature of LED is calibrated by thermal imager, thereby, the relation curve between the LED temperature controlling current and the blackbody simulation temperature difference is established, accurately achieved the temperature control of the infrared target. Experimental results show that the accuracy of the device in field testing of thermal imager MRTD can be limited within 0.1K, which greatly reduces the cost to meet the project requirements with a wide application value.

Image Comparisons of Black Hole vs. Neutron Dark Star by Ray Tracing

NASA Astrophysics Data System (ADS)

Froedge, D. T.

2015-04-01

In previous papers we have discussed the concept of a theory of gravitation with local energy conservation, and the properties of a large neutron star resulting when the energy of gravitation resides locally with the particle mass and not in the gravitational field. A large neutron star's surface radius grows closer to the gravitational radius as the mass increases. Since the localization of energy applies to the photon, they do not decrease energy rising in a gravitational field, and can escape. Photon trajectories in a strong gravitational field can be investigated by the use of ray tracing procedures. Only a fraction of the blackbody radiation emitted from the surface escapes into space (about 0.00004% for Sag A*). Because of the low % of escaping radiation, the heavy neutron stars considered in this paper will be referred to as a Neutron Dark Star (NDS). In contrast to the Black Hole (BH) which should be totally dark inside the photon shadow, the NDS will appear as a fuzzy low luminosity ball. For Sag A* a full width half maximum diameter is about 3.85 Schwarzschild radii inside the shadow. (http://www.arxdtf.org/css/Image%20Comparisons.pdf). The Event Horizon Telescope should be able to distinguish the difference between the theories.

Research on the shortwave infrared hyperspectral imaging technology based on Integrated Stepwise filter

NASA Astrophysics Data System (ADS)

Wei, Liqing; Xiao, Xizhong; Wang, Yueming; Zhuang, Xiaoqiong; Wang, Jianyu

2017-11-01

Space-borne hyperspectral imagery is an important tool for earth sciences and industrial applications. Higher spatial and spectral resolutions have been sought persistently, although this results in more power, larger volume and weight during a space-borne spectral imager design. For miniaturization of hyperspectral imager and optimization of spectral splitting methods, several methods are compared in this paper. Spectral time delay integration (TDI) method with high transmittance Integrated Stepwise Filter (ISF) is proposed.With the method, an ISF imaging spectrometer with TDI could achieve higher system sensitivity than the traditional prism/grating imaging spectrometer. In addition, the ISF imaging spectrometer performs well in suppressing infrared background radiation produced by instrument. A compact shortwave infrared (SWIR) hyperspectral imager prototype based on HgCdTe covering the spectral range of 2.0-2.5 μm with 6 TDI stages was designed and integrated. To investigate the performance of ISF spectrometer, a method to derive the optimal blocking band curve of the ISF is introduced, along with known error characteristics. To assess spectral performance of the ISF system, a new spectral calibration based on blackbody radiation with temperature scanning is proposed. The results of the imaging experiment showed the merits of ISF. ISF has great application prospects in the field of high sensitivity and high resolution space-borne hyperspectral imagery.

Broadband Spectral Investigations of SGR J1550-5418 Bursts

NASA Technical Reports Server (NTRS)

Lin, Lin; Goegues, Ersin; Baring, Matthew G.; Granot, Jonathan; Kouveliotou, Chryssa; Kaneko, Yuki; van der Horst, Alexander; Gruber, David; von Kienlin, Andreas; Younes, George;

DISCOVERY OF SMOOTHLY EVOLVING BLACKBODIES IN THE EARLY AFTERGLOW OF GRB 090618: EVIDENCE FOR A SPINE–SHEATH JET?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basak, Rupal; Rao, A. R., E-mail: rupalb@tifr.res.in, E-mail: arrao@tifr.res.in

2015-10-20

GRB 090618 is a bright gamma-ray burst (GRB) with multiple pulses. It shows evidence of thermal emission in the initial pulses as well as in the early afterglow phase. Because high-resolution spectral data from the Swift/X-ray Telescope (XRT) are available for the early afterglow, we investigate the shape and evolution of the thermal component in this phase using data from the Swift/Burst Alert Telescope (BAT), the Swift/XRT, and the Fermi/Gamma-ray Burst Monitor detectors. An independent fit to the BAT and XRT data reveals two correlated blackbodies with monotonically decreasing temperatures. Hence, we investigated the combined data with a model consistingmore » of two blackbodies and a power law (2BBPL), a model suggested for several bright GRBs. We elicit the following interesting features of the 2BBPL model: (1) the same model is applicable from the peak of the last pulse in the prompt emission to the afterglow emission, (2) the ratio of temperatures and the fluxes of the two blackbodies remains constant throughout the observations, (3) the blackbody temperatures and fluxes show a monotonic decrease with time, with the BB fluxes dropping about a factor of two faster than that of the power-law (PL) emission, and (4) attributing the blackbody emission to photospheric emissions, we find that the photospheric radii increase very slowly with time, and the lower-temperature blackbody shows a larger emitting radius than that of the higher-temperature blackbody. We find some evidence that the underlying shape of the nonthermal emission is a cutoff power law rather than a PL. We sketch a spine–sheath jet model to explain our observations.« less

Advances in Front-end Enabling Technologies for Thermal Infrared ` THz Torch' Wireless Communications

NASA Astrophysics Data System (ADS)

Hu, Fangjing; Lucyszyn, Stepan

2016-09-01

The thermal (emitted) infrared frequency bands (typically 20-40 and 60-100 THz) are best known for remote sensing applications that include temperature measurement (e.g. non-contacting thermometers and thermography), night vision and surveillance (e.g. ubiquitous motion sensing and target acquisition). This unregulated part of the electromagnetic spectrum also offers commercial opportunities for the development of short-range secure communications. The ` THz Torch' concept, which fundamentally exploits engineered blackbody radiation by partitioning thermally generated spectral radiance into pre-defined frequency channels, was recently demonstrated by the authors. The thermal radiation within each channel can be independently pulse-modulated, transmitted and detected, to create a robust form of short-range secure communications within the thermal infrared. In this paper, recent progress in the front-end enabling technologies associated with the THz Torch concept is reported. Fundamental limitations of this technology are discussed; possible engineering solutions for further improving the performance of such thermal-based wireless links are proposed and verified either experimentally or through numerical simulations. By exploring a raft of enabling technologies, significant enhancements to both data rate and transmission range can be expected. With good engineering solutions, the THz Torch concept can exploit nineteenth century physics with twentieth century multiplexing schemes for low-cost twenty-first century ubiquitous applications in security and defence.

Stellar Temporal Intensity Interferometry

NASA Astrophysics Data System (ADS)

Kian, Tan Peng

Stellar intensity interferometry was developed by Hanbury-Brown & Twiss [1954, 1956b, 1957, 1958] to bypass the diffraction limit of telescope apertures, with successful measurements including the determination of 32 stellar angular diameters using the Narrabri Stellar Intensity Interferometer [Hanbury-Brown et al., 1974]. This was achieved by measuring the intensity correlations between starlight received by a pair of telescopes separated by varying baselines b which, by invoking the van Cittert-Zernicke theorem [van Cittert, 1934; Zernicke, 1938], are related to the angular intensity distributions of the stellar light sources through a Fourier transformation of the equal-time complex degree of coherence gamma(b) between the two telescopes. This intensity correlation, or the second order correlation function g(2) [Glauber, 1963], can be described in terms of two-photoevent coincidence measurements [Hanbury-Brown, 1974] for our use of photon-counting detectors. The application of intensity interferometry in astrophysics has been largely restricted to the spatial domain but not found widespread adoption due to limitations by its signal-to-noise ratio [Davis et al., 1999; Foellmi, 2009; Jensen et al., 2010; LeBohec et al., 2008, 2010], although there is a growing movement to revive its use [Barbieri et al., 2009; Capraro et al., 2009; Dravins & Lagadec, 2014; Dravins et al., 2015; Dravins & LeBohec, 2007]. In this thesis, stellar intensity interferometry in the temporal domain is investigated instead. We present a narrowband spectral filtering scheme [Tan et al., 2014] that allows direct measurements of the Lorentzian temporal correlations, or photon bunching, from the Sun, with the preliminary Solar g(2)(tau = 0) = 1.3 +/- 0.1, limited mostly by the photon detector response [Ghioni et al., 2008], compared to the theoretical value of g(2)(0) = 2. The measured temporal photon bunching signature of the Sun exceeded the previous records of g(2)(0) = 1.03 [Karmakar et al., 2012] and g(2)(0) = 1.04 [Liu et al., 2014] by an order of magnitude. In order to study possible effects of atmospheric turbulence [Blazej et al., 2008; Cavazzani et al., 2012; Dravins et al., 1997] on temporal intensity interferometry, the filtering scheme was improved so that the required integration time of measurement reduced from 45 minutes previously to only 4 minutes, which allowed for timing correlation measurements of Sunlight in 1° intervals of elevation angular position to probe the atmospheric dependence. The instruments were used to measure the temporal photon bunching signal of the Sun from 11:36 am to 5:36 pm, covering Solar elevation angles from approximately 70° just before noon to about 20° by the evening, corresponding to different depths of atmospheric air column [Bennett, 1982; Marini & Murray, 1973] the sunlight passed through. The thereby obtained Solar g (2)(tau = 0) = 1.693 +/- 0.003 exceeded our previous record, due to improved suppression of the blackbody spectrum outside the target bandwidth. The Solar photon bunching signature was compatible with control measurements of an Argon arc lamp with g(2)(tau = 0) = 1.687 +/- 0.004, which served as a blackbody light source of temperature T = 6000K. This suggests that the atmospheric and weather conditions have no measurable effects on temporal intensity interferometry for a 2GHz optical bandwidth after narrowband spectral filtering. The instruments were exposed to a light source simulating astrophysical scenarios, created by mixing the blackbody radiation from the Argon arc lamp with laser light at 513.8 nm. The spectral filtering scheme was able to isolate the laser light by filtering the blackbody spectrum to only Deltanu FWHM ≈ 2GHz and thus suppressing the blackbody contribution to the order of 104 photoevents/sec. The instruments were thus able to identify coherent laser light contributions of 3 x 10 4 photoevents/sec within the blackbody spectrum, which is a situation that Optical SETI [Drake, 1961; Dyson, 1960; Forgan, 2014; Korpela et al., 2011; Merali, 2015; Sagan & Drake, 1975; Townes, 1983] may have to identify. The final scenario tested was to identify the laser light at 513.8 nm that has been Doppler broadened by a suspension of mono-dispersive microspheres [Dravins & Lagadec, 2014; Dravins et al., 2015]. We found that g(2)(0) = 1.227 +/- 0.005 and determined the coherence time of the broadened laser signal to be tauc = 44 +/- 2 ns, corresponding to a linewidth of about 23MHz which is comparable to the predicted linewidth values for natural lasers [Dravins & Germana, 2008; Griest et al., 2010; Johansson & Letokhov, 2005; Roche et al., 2012; Strelnitski et al., 1995; Taylor, 1983; Tellis & Marcy, 2015]. These results suggest that the narrowband spectral filtering technique developed in this thesis may provide a useful tool for revisiting intensity correlation measurements in astronomy again.

Blackbody emission from light interacting with an effective moving dispersive medium.

PubMed

Petev, M; Westerberg, N; Moss, D; Rubino, E; Rimoldi, C; Cacciatori, S L; Belgiorno, F; Faccio, D

2013-07-26

Intense laser pulses excite a nonlinear polarization response that may create an effective flowing medium and, under appropriate conditions, a blocking horizon for light. Here, we analyze in detail the interaction of light with such laser-induced flowing media, fully accounting for the medium dispersion properties. An analytical model based on a first Born approximation is found to be in excellent agreement with numerical simulations based on Maxwell's equations and shows that when a blocking horizon is formed, the stimulated medium scatters light with a blackbody emission spectrum. Based on these results, diamond is proposed as a promising candidate medium for future studies of Hawking emission from artificial, dispersive horizons.

Systematic evaluation of an atomic clock at 2 × 10−18 total uncertainty

PubMed Central

Nicholson, T.L.; Campbell, S.L.; Hutson, R.B.; Marti, G.E.; Bloom, B.J.; McNally, R.L.; Zhang, W.; Barrett, M.D.; Safronova, M.S.; Strouse, G.F.; Tew, W.L.; Ye, J.

2015-01-01

The pursuit of better atomic clocks has advanced many research areas, providing better quantum state control, new insights in quantum science, tighter limits on fundamental constant variation and improved tests of relativity. The record for the best stability and accuracy is currently held by optical lattice clocks. Here we take an important step towards realizing the full potential of a many-particle clock with a state-of-the-art stable laser. Our 87Sr optical lattice clock now achieves fractional stability of 2.2 × 10−16 at 1 s. With this improved stability, we perform a new accuracy evaluation of our clock, reducing many systematic uncertainties that limited our previous measurements, such as those in the lattice ac Stark shift, the atoms' thermal environment and the atomic response to room-temperature blackbody radiation. Our combined measurements have reduced the total uncertainty of the JILA Sr clock to 2.1 × 10−18 in fractional frequency units. PMID:25898253

On extreme transient events from rotating black holes and their gravitational wave emission

NASA Astrophysics Data System (ADS)

van Putten, Maurice H. P. M.; Della Valle, Massimo

2017-01-01

The super-luminous object ASASSN-15lh (SN2015L) is an extreme event with a total energy Erad ≃ 1.1 × 1052 erg in blackbody radiation on par with its kinetic energy Ek in ejecta and a late time plateau in the UV, which defies a nuclear origin. It likely presents a new explosion mechanism for hydrogen-deprived supernovae. With no radio emission and no H-rich environment, we propose to identify Erad with dissipation of a baryon-poor outflow in the optically thick remnant stellar envelope produced by a central engine. By negligible time-scales of light crossing and radiative cooling of the envelope, SN2015L's light curve closely tracks the evolution of this engine. We here model its light curve by the evolution of black hole spin during angular momentum loss in Alvén waves to matter at the Inner Most Stable Circular Orbit (ISCO). The duration is determined by σ = MT/M of the torus mass MT around the black hole of mass M: σ ˜ 10-7 and σ ˜ 10-2 for SN2015L and, respectively, a long GRB. The observed electromagnetic radiation herein represents a minor output of the rotational energy Erot of the black hole, while most is radiated unseen in gravitational radiation. This model explains the high-mass slow-spin binary progenitor of GWB150914, as the remnant of two CC-SNe in an intra-day binary of two massive stars. This model rigorously predicts a change in magnitude Δm ≃ 1.15 in the light curve post-peak, in agreement with the light curve of SN2015L with no fine-tuning.

New constraints on the X-ray spectral properties of type 1 active galactic nuclei

NASA Astrophysics Data System (ADS)

Scott, A. E.; Stewart, G. C.; Mateos, S.; Alexander, D. M.; Hutton, S.; Ward, M. J.

2011-10-01

We present a detailed characterization of the X-ray spectral properties of 761 type 1 active galactic nuclei (AGN), selected from a cross-correlation of the SDSS DR5 quasar catalogue and the incremental version of the second XMM-Newton serendipitous X-ray source catalogue 2XMMi-DR2. The X-ray spectrum of each source has been fitted with models based on a simple power law to which additional cold absorption and/or soft-excess features have been added if an F-test at 99 per cent significance required them. The distribution of best-fitting photon indices, Γ, has been fitted with a Gaussian with mean <Γ>= 1.99 ± 0.01 and dispersion σ<Γ>= 0.30 ± 0.01; however, this does not provide a good representation of the distribution due to sources with very flat or steep Γ values. A highly significant trend for decreasing Γ values with increasing 2-10 keV luminosity, LX, has been seen but only a weak trend with redshift has been found. Intrinsic cold absorption has been detected in ˜4 per cent of the sample and soft-excess emission has been detected in ˜8 per cent. These values are lower limits due to the detectability being limited by the quality of the spectra and we suggest that the intrinsic values may be as high as ˜25 and ˜80 per cent, respectively. The levels of rest-frame absorption are higher than expected for type 1 objects (NH= 1021-1023 cm-2) and the fraction of absorbed sources and the NH values were not seen to vary with LX or z. The average blackbody temperature used to model the soft excesses is = 0.17 ± 0.09 keV. This temperature has been found to correlate with LX but not the blackbody luminosity or the black hole mass which do correlate with each other. A strong correlation has been found between the luminosities in the blackbody and power-law components, suggesting that a similar fraction is reprocessed from the blackbody to the power-law component for the entire luminosity range of objects. A positive correlation between Γ and the X-ray derived Eddington ratio has been found for the sources whose mass was determined using the Hβ line, but a negative correlation has been found where the C IV line was used. No correlation has been found where the Mg II line was used. No significant correlations have been found between the blackbody temperature, luminosity or black hole mass with Eddington ratio, despite a link between the power law and blackbody production being indicated. The sample includes 552 confirmed radio-quiet quasars (RQQ) and 75 confirmed radio-loud quasars (RLQ). The RLQ have been found to have higher LX values than their RQQ counterparts, suggesting an additional X-ray component, perhaps related to a jet, is present in these sources. This component may also be the cause of the flatter Γ values seen in RLQ.

Planck early results. XXV. Thermal dust in nearby molecular clouds

NASA Astrophysics Data System (ADS)

Planck Collaboration; Abergel, A.; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bhatia, R.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Cabella, P.; Cardoso, J.-F.; Catalano, A.; Cayón, L.; Challinor, A.; Chamballu, A.; Chiang, L.-Y.; Chiang, C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Coulais, A.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Gasperis, G.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Dobashi, K.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Guillet, V.; Hansen, F. K.; Harrison, D.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Hoyland, R. J.; Huffenberger, K. M.; Jaffe, A. H.; Jones, A.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knox, L.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leach, S.; Leonardi, R.; Leroy, C.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Maffei, B.; Mandolesi, N.; Mann, R.; Maris, M.; Marshall, D. J.; Martin, P.; Martínez-González, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, A.; Naselsky, P.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Pajot, F.; Paladini, R.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Poutanen, T.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, P.; Smoot, G. F.; Starck, J.-L.; Stivoli, F.; Stolyarov, V.; Sudiwala, R.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Torre, J.-P.; Tristram, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Verstraete, L.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Yvon, D.; Zacchei, A.; Zonca, A.

2011-12-01

Planck allows unbiased mapping of Galactic sub-millimetre and millimetre emission from the most diffuse regions to the densest parts of molecular clouds. We present an early analysis of the Taurus molecular complex, on line-of-sight-averaged data and without component separation. The emission spectrum measured by Planck and IRAS can be fitted pixel by pixel using a single modified blackbody. Some systematic residuals are detected at 353 GHz and 143 GHz, with amplitudes around -7% and +13%, respectively, indicating that the measured spectra are likely more complex than a simple modified blackbody. Significant positive residuals are also detected in the molecular regions and in the 217 GHz and 100 GHz bands, mainly caused by the contribution of the J = 2 → 1 and J = 1 → 0 12CO and 13CO emission lines. We derive maps of the dust temperature T, the dust spectral emissivity index β, and the dust optical depth at 250 μm τ250. The temperature map illustrates the cooling of the dust particles in thermal equilibrium with the incident radiation field, from 16 - 17 K in the diffuse regions to 13 - 14 K in the dense parts. The distribution of spectral indices is centred at 1.78, with a standard deviation of 0.08 and a systematic error of 0.07. We detect a significant T - β anti-correlation. The dust optical depth map reveals the spatial distribution of the column density of the molecular complex from the densest molecular regions to the faint diffuse regions. We use near-infrared extinction and Hi data at 21-cm to perform a quantitative analysis of the spatial variations of the measured dust optical depth at 250 μm per hydrogen atom τ250/NH. We report an increase of τ250/NH by a factor of about 2 between the atomic phase and the molecular phase, which has a strong impact on the equilibrium temperature of the dust particles. Corresponding author: A. Abergel, e-mail: alain.abergel@ias.u-psud.fr

XMM-Newton Archival Study of the ULX Population in Nearby Galaxies

NASA Technical Reports Server (NTRS)

Winter, Lisa M.; Mushotzky, Richard F.; Reynolds, christopher S.

2006-01-01

We present the results of an archival XMM-Newton study of the bright X-ray point sources (L(sub X) greater than 10(exp 38 erg per second)) in 32 nearby galaxies. From our list of approximately 100 point sources, we attempt to determine if there is a low-state counterpart to the Ultraluminous X-ray (ULX) population, searching for a soft-hard state dichotomy similar to that known for Galactic X-ray binaries and testing the specific predictions of the IMBH hypothesis. To this end, we searched for low-state objects, which we defined as objects within our sample which had a spectrum well fit by a simple absorbed power law, and high-state objects, which we defined as objects better fit by a combined blackbody and a power law. Assuming that low-state)) objects accrete at approximately 10% of the Eddington luminosity (Done & Gierlinski 2003) and that high-state objects accrete near the Eddington luminosity we further divided our sample of sources into low and high state ULX sources. We classify 16 sources as low-state ULXs and 26 objects as high-state ULXs. As in Galactic black hole systems, the spectral indices, GAMMA, of the lowstate objects, as well as the luminosities, tend to be lower than those of the high-state objects. The observed range of blackbody temperatures for the high state is 0.1-1 keV, with the most luminous systems tending toward the lowest temperatures. We therefore divide our high-state ULXs into candidate IMBHs (with blackbody temperatures of approximately 0.1 keV) and candidate stellar mass BHs (with blackbody temperatures of approximately 1.0 keV). A subset of the candidate stellar mass BHs have spectra that are well-fit by a Comptonization model, a property similar of Galactic BHs radiating in the very-high state near the Eddington limit.

The microwave background anisotropies: Observations

PubMed Central

Wilkinson, David

1998-01-01

Most cosmologists now believe that we live in an evolving universe that has been expanding and cooling since its origin about 15 billion years ago. Strong evidence for this standard cosmological model comes from studies of the cosmic microwave background radiation (CMBR), the remnant heat from the initial fireball. The CMBR spectrum is blackbody, as predicted from the hot Big Bang model before the discovery of the remnant radiation in 1964. In 1992 the cosmic background explorer (COBE) satellite finally detected the anisotropy of the radiation—fingerprints left by tiny temperature fluctuations in the initial bang. Careful design of the COBE satellite, and a bit of luck, allowed the 30 μK fluctuations in the CMBR temperature (2.73 K) to be pulled out of instrument noise and spurious foreground emissions. Further advances in detector technology and experiment design are allowing current CMBR experiments to search for predicted features in the anisotropy power spectrum at angular scales of 1° and smaller. If they exist, these features were formed at an important epoch in the evolution of the universe—the decoupling of matter and radiation at a temperature of about 4,000 K and a time about 300,000 years after the bang. CMBR anisotropy measurements probe directly some detailed physics of the early universe. Also, parameters of the cosmological model can be measured because the anisotropy power spectrum depends on constituent densities and the horizon scale at a known cosmological epoch. As sophisticated experiments on the ground and on balloons pursue these measurements, two CMBR anisotropy satellite missions are being prepared for launch early in the next century. PMID:9419320

Collimated thermal radiation transfer via half Maxwell's fish-eye lens for thermophotovoltaics

NASA Astrophysics Data System (ADS)

Chung, Haejun; Zhou, Zhiguang; Bermel, Peter

2017-05-01

Thermophotovoltaics (TPV) convert heat into electricity by capturing thermal radiation with a photovoltaic (PV) cell, ideally at efficiencies of 50% or more. However, excess heating of the PV cell from close proximity to the emitter substantially reduces the system efficiency. In this work, we theoretically develop and numerically demonstrate an approach to fundamentally improving TPV systems that allow for a much greater separation of an emitter and a receiver. Thus, we solve the excess heating dilemma, required for achieving theoretically high efficiencies. It consists of a spherically graded index lens known as Maxwell's Fish-Eye (MFE) structure, capable of collimating hemispherical emission into a much narrower range of angles, close to the normal direction. To fully characterize the power radiation profile of the MFE, we perform finite-difference time-domain simulations for a quarter MFE and then map it onto a Gaussian beam approximation. The modeled beam properties are subsequently used to study a half MFE. In an optimized half MFE design, 90% of all thermal photons reach a receiver at a distance of 100 λ; by comparison, only 15.6% of a blackbody emitter reach a receiver in the same geometry. It is also shown that the emission achieved by a half MFE can lead to a photon recycling rate above 95% for below bandgap photons at an emitter-receiver separation of 100 λ. By applying a half MFE, the absolute TPV efficiency can be improved from 5.74% to 37.15%, which represents a significant step forward in realizing high-efficiency TPV systems.

Infrared rectification in a nanoantenna-coupled metal-oxide-semiconductor tunnel diode.

PubMed

Davids, Paul S; Jarecki, Robert L; Starbuck, Andrew; Burckel, D Bruce; Kadlec, Emil A; Ribaudo, Troy; Shaner, Eric A; Peters, David W

2015-12-01

Direct rectification of electromagnetic radiation is a well-established method for wireless power conversion in the microwave region of the spectrum, for which conversion efficiencies in excess of 84% have been demonstrated. Scaling to the infrared or optical part of the spectrum requires ultrafast rectification that can only be obtained by direct tunnelling. Many research groups have looked to plasmonics to overcome antenna-scaling limits and to increase the confinement. Recently, surface plasmons on heavily doped Si surfaces were investigated as a way of extending surface-mode confinement to the thermal infrared region. Here we combine a nanostructured metallic surface with a heavily doped Si infrared-reflective ground plane designed to confine infrared radiation in an active electronic direct-conversion device. The interplay of strong infrared photon-phonon coupling and electromagnetic confinement in nanoscale devices is demonstrated to have a large impact on ultrafast electronic tunnelling in metal-oxide-semiconductor (MOS) structures. Infrared dispersion of SiO2 near a longitudinal optical (LO) phonon mode gives large transverse-field confinement in a nanometre-scale oxide-tunnel gap as the wavelength-dependent permittivity changes from 1 to 0, which leads to enhanced electromagnetic fields at material interfaces and a rectified displacement current that provides a direct conversion of infrared radiation into electric current. The spectral and electrical signatures of the nanoantenna-coupled tunnel diodes are examined under broadband blackbody and quantum-cascade laser (QCL) illumination. In the region near the LO phonon resonance, we obtained a measured photoresponsivity of 2.7 mA W(-1) cm(-2) at -0.1 V.

Coherence-limited solar power conversion: the fundamental thermodynamic bounds and the consequences for solar rectennas

NASA Astrophysics Data System (ADS)

Mashaal, Heylal; Gordon, Jeffrey M.

2014-10-01

Solar rectifying antennas constitute a distinct solar power conversion paradigm where sunlight's spatial coherence is a basic constraining factor. In this presentation, we derive the fundamental thermodynamic limit for coherence-limited blackbody (principally solar) power conversion. Our results represent a natural extension of the eponymous Landsberg limit, originally derived for converters that are not constrained by the radiation's coherence, and are irradiated at maximum concentration (i.e., with a view factor of unity to the solar disk). We proceed by first expanding Landsberg's results to arbitrary solar view factor (i.e., arbitrary concentration and/or angular confinement), and then demonstrate how the results are modified when the converter can only process coherent radiation. The results are independent of the specific power conversion mechanism, and hence are valid for diffraction-limited as well as quantum converters (and not just classical heat engines or in the geometric optics regime). The derived upper bounds bode favorably for the potential of rectifying antennas as potentially high-efficiency solar converters.

Reproducibility of WC-C High-Temperature Fixed Point

NASA Astrophysics Data System (ADS)

Grigoryeva, I. A.; Khlevnoy, B. B.; Solodilov, M. V.

2017-05-01

Reproducibility of the tungsten carbide-carbon peritectic (WC-C) fixed point (3021 K) was investigated by comparing six WC-C blackbody-type cells with each other. All the cells were built at VNIIOFI and had the same design with a cell outer diameter of 24 mm and a cavity opening diameter of 3 mm. Four cells were built using tungsten powder supplied by Alfa Aesar, while the other two cells used powder from Zhuzhou KETE (China). The nominal purity of both suppliers was 99.999 %. All the cells were compared in the same furnace. A reference cell in the second furnace was used for monitoring the stability of a radiation thermometer. Melting temperatures (given by the point of inflection) of all six cells agreed within ±45 mK. The reproducibility, as a standard deviation of the measured temperatures, can be estimated as 35 mK. The Zhuzhou KETE cells showed a slightly lower temperature than the Alfa Aesar cells: by 32 mK on average, which is comparable with repeatability of the measurements.

Real-time millimeter-wave imaging radiometer for avionic synthetic vision

NASA Astrophysics Data System (ADS)

Lovberg, John A.; Chou, Ri-Chee; Martin, Christopher A.

1994-07-01

ThermoTrex Corporation (TTC) has developed an imaging radiometer, the passive microwave camera (PMC), that uses an array of frequency-scanned antennas coupled to a multi-channel acousto-optic (Bragg cell) spectrum analyzer to form visible images of a scene through acquisition of thermal blackbody radiation in the millimeter-wave spectrum. The output of the Bragg cell is imaged by a standard video camera and passed to a computer for normalization and display at real-time frame rates. One application of this system could be its incorporation into an enhanced vision system to provide pilots with a clear view of the runway during fog and other adverse weather conditions. The unique PMC system architecture will allow compact large-aperture implementations because of its flat antenna sensor. Other potential applications include air traffic control, all-weather area surveillance, fire detection, and security. This paper describes the architecture of the TTC PMC and shows examples of images acquired with the system.

ED07-0210-3

NASA Image and Video Library

2007-09-13

The instruments that make up the Ames Autonomous Module Scanner (AMS) that provided precise thermal-infrared imaging during the Western States Fire Mission in 2007 are detailed in this photo of the AMS as mounted on Ikhana's pod tray. The large foil-covered foam-insulated box at left covers the pressure vessel containing the data system computers and other electronics. The round white-topped assembly is the scan head, including the scan mirror, folded telescope, blackbody references, spectrometer and detectors. Two pressure boxes visible at the forward end of the tray contain the Applanix POS/AV precision navigation subsystem (black) and the power distributor including circuit breakers and ancillary wiring, scan motor controller and the blackbody reference temperature controller (blue).

Shape-Independent Limits to Near-Field Radiative Heat Transfer

NASA Astrophysics Data System (ADS)

Miller, Owen D.; Johnson, Steven G.; Rodriguez, Alejandro W.

2015-11-01

We derive shape-independent limits to the spectral radiative heat transfer rate between two closely spaced bodies, generalizing the concept of a blackbody to the case of near-field energy transfer. Through conservation of energy and reciprocity, we show that each body of susceptibility χ can emit and absorb radiation at enhanced rates bounded by |χ |2/Im χ , optimally mediated by near-field photon transfer proportional to 1 /d2 across a separation distance d . Dipole-dipole and dipole-plate structures approach restricted versions of the limit, but common large-area structures do not exhibit the material enhancement factor and thus fall short of the general limit. By contrast, we find that particle arrays interacting in an idealized Born approximation (i.e., neglecting multiple scattering) exhibit both enhancement factors, suggesting the possibility of orders-of-magnitude improvement beyond previous designs and the potential for radiative heat transfer to be comparable to conductive heat transfer through air at room temperature, and significantly greater at higher temperatures.

Investigating students’ mental models about the nature of light in different contexts

NASA Astrophysics Data System (ADS)

Özcan, Özgür

2015-11-01

In this study, we investigated pre-service physics teachers’ mental models of light in different contexts, such as blackbody radiation, the photoelectric effect and the Compton effect. The data collected through the paper-and-pencil questionnaire (PPQ) were analyzed both quantitatively and qualitatively. Sampling of this study consists of a total of 110 physics education students who were taking a modern physics course at two different state universities in Turkey. As a result, three mental models, which were called the beam ray model (BrM), hybrid model (HM) and particle model (PM), were being used by the students while explaining these phenomena. The most model fluctuation was seen in HM and BrM. In addition, some students were in a mixed-model state where they use multiple mental models in explaining a phenomenon and used these models inconsistently. On the other hand, most of the students who used the particle model can be said to be in a pure model state.

Photodissociation of CS from Excited Rovibrational Levels

NASA Astrophysics Data System (ADS)

Pattillo, R. J.; Cieszewski, R.; Stancil, P. C.; Forrey, R. C.; Babb, J. F.; McCann, J. F.; McLaughlin, B. M.

2018-05-01

Accurate photodissociation cross sections have been computed for transitions from the X 1Σ+ ground electronic state of CS to six low-lying excited electronic states. New ab initio potential curves and transition dipole moment functions have been obtained for these computations using the multi-reference configuration interaction approach with the Davidson correction (MRCI+Q) and aug-cc-pV6Z basis sets. State-resolved cross sections have been computed for transitions from nearly the full range of rovibrational levels of the X 1Σ+ state and for photon wavelengths ranging from 500 Å to threshold. Destruction of CS via predissociation in highly excited electronic states originating from the rovibrational ground state is found to be unimportant. Photodissociation cross sections are presented for temperatures in the range between 1000 and 10,000 K, where a Boltzmann distribution of initial rovibrational levels is assumed. Applications of the current computations to various astrophysical environments are briefly discussed focusing on photodissociation rates due to the standard interstellar and blackbody radiation fields.

Design and calibration of a novel transient radiative heat flux meter for a spacecraft thermal test

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Chunchen; Hu, Peng, E-mail: hupeng@ustc.edu.cn; Cheng, Xiaofang

2016-06-15

Radiative heat flux measurement is significantly important for a spacecraft thermal test. To satisfy the requirements of both high accuracy and fast response, a novel transient radiative heat flux meter was developed. Its thermal receiver consists of a central thermal receiver and two thermal guarded annular plates, which ensure the temperature distribution of the central thermal receiver to be uniform enough for reasonably applying lumped heat capacity method in a transient radiative heat flux measurement. This novel transient radiative heat flux meter design can also take accurate measurements regardless of spacecraft surface temperature and incident radiation spectrum. The measurement principlemore » was elaborated and the coefficients were calibrated. Experimental results from testing a blackbody furnace and an Xenon lamp show that this novel transient radiative heat flux meter can be used to measure transient radiative heat flux up to 1400 W/m{sup 2} with high accuracy and the response time of less than 10 s.« less

Confronting GRB prompt emission with a model for subphotospheric dissipation

DOE PAGES

Ahlgren, Björn; Larsson, Josefin; Nymark, Tanja; ...

2015-09-16

The origin of the prompt emission in gamma-ray bursts (GRBs) is still an unsolved problem and several different mechanisms have been suggested. We fit Fermi GRB data with a photospheric emission model which includes dissipation of the jet kinetic energy below the photosphere. The resulting spectra are dominated by Comptonization and contain no significant contribution from synchrotron radiation. In order to fit to the data, we span a physically motivated part of the model's parameter space and create DREAM (Dissipation with Radiative Emission as A table Model), a table model for XSPEC. Here, we show that this model can describemore » different kinds of GRB spectra, including GRB 090618, representing a typical Band function spectrum, and GRB 100724B, illustrating a double peaked spectrum, previously fitted with a Band+blackbody model, suggesting they originate from a similar scenario. We also suggest that the main difference between these two types of bursts is the optical depth at the dissipation site.« less

Evolution of branch points for a laser beam propagating through an uplink turbulent atmosphere.

PubMed

Ge, Xiao-Lu; Liu, Xuan; Guo, Cheng-Shan

2014-03-24

Evolution of branch points in the distorted optical field is studied when a laser beam propagates through turbulent atmosphere along an uplink path. Two categories of propagation events are mainly explored for the same propagation height: fixed wavelength with change of the turbulence strength and fixed turbulence strength with change of the wavelength. It is shown that, when the beam propagates to a certain height, the density of the branch-points reaches its maximum and such a height changes with the turbulence strength but nearly remains constant with different wavelengths. The relationship between the density of branch-points and the Rytov number is also given. A fitted formula describing the relationship between the density of branch-points and propagation height with different turbulence strength and wavelength is found out. Interestingly, this formula is very similar to the formula used for describing the Blackbody radiation in physics. The results obtained may be helpful for atmospheric optics, astronomy and optical communication.

New trends in cosmology

NASA Technical Reports Server (NTRS)

Canuto, V. M.

1978-01-01

A review of big-bang cosmology is presented, emphasizing the big-bang model, hypotheses on the origin of galaxies, observational tests of the big-bang model that may be possible with the Large Space Telescope, and the scale-covariant theory of gravitation. Detailed attention is given to the equations of general relativity, the redshift-distance relation for extragalactic objects, expansion of the universe, the initial singularity, the discovery of the 3-K blackbody radiation, and measurements of the amount of deuterium in the universe. The curvature of the expanding universe is examined along with the magnitude-redshift relation for quasars and galaxies. Several models for the origin of galaxies are evaluated, and it is suggested that a model of galaxy formation via the formation of black holes is consistent with the model of an expanding universe. Scale covariance is discussed, a scale-covariant theory is developed which contains invariance under scale transformation, and it is shown that Dirac's (1937) large-numbers hypothesis finds a natural role in this theory by relating the atomic and Einstein units.

Long pulse Soft X-ray Emission from Laser Generated Irradiated Gold Foils

NASA Astrophysics Data System (ADS)

Davis, Joshua; Frank, Yechiel; Raicher, Erez; Fraenkel, Moshe; Keiter, Paul; Klein, Sallee; Drake, R. P.; Shvarts, Dov

2016-10-01

Long pulse soft x-ray sources (SXS) allow for flexibility in high-energy-density experimental designs by providing a means of driving matter to the high temperatures needed, for example to study radiation waves in different materials. SXSs can be made by using lasers to heat a high-Z thin foil, which then acts as a quasi-blackbody emitter. Previous studies of the x-ray emission characteristics of gold foils have focused on laser pulses of 1ns or less. We performed experiments using a 6.0ns laser pulse with energy of 2kJ on the Omega-60 system to generate and characterize multi-ns laser heated Au foils of thicknesses between 0.5-2.0 μm. We measured the 2D spatial profile of the emission with a soft x-ray camera and the time history of the emission with the Dante photodiode array . Effective temperatures for the emission were then calculated using the Dante measurements. Discussion of experimental results and a comparison with 1-D Rad-Hydro NLTE simulations will be presented.

A Comparison Between Spectral Properties of ULXs and Luminous X-ray Binaries

NASA Astrophysics Data System (ADS)

Berghea, C. T.; Colbert, E. J. M.; Roberts, T. P.

2004-05-01

What is special about the 1039 erg s-1 limit that is used to define the ULX class? We investigate this question by analyzing Chandra X-ray spectra of 71 X-ray bright point sources from nearby galaxies. Fifty-one of these sources are ULXs (LX(0.3-8.0 keV) ≥ 1039 erg s-1), and 20 sources (our comparison sample) are less-luminous X-ray binaries with LX(0.3-8.0 keV) = 1038-39 erg s-1. Our sample objects were selected from the Chandra archive to have ≥1000 counts and thus represent the highest quality spectra in the Chandra archives for extragalactic X-ray binaries and ULXs. We fit the spectra with one-component models (e.g., cold absorption with power-law, or cold absorption with multi-colored disk blackbody) and two-component models (e.g. absorption with both a power-law and a multi colored disk blackbody). A crude measure of the spectral states of the sources are determined observationally by calibrating the strength of the disk (blackbody) and coronal (power-law) components. These results are then use to determine if spectral properties of the ULXs are statistically distinct from those of the comparison objects, which are assumed to be ``normal'' black-hole X-ray binaries.

X-Ray Observations of Magnetar SGR 0501+4516 from Outburst to Quiescence

NASA Astrophysics Data System (ADS)

Mong, Y.-L.; Ng, C.-Y.

2018-01-01

Magnetars are neutron stars having extreme magnetic field strengths. Study of their emission properties in quiescent state can help understand effects of a strong magnetic field on neutron stars. SGR 0501+4516 is a magnetar that was discovered in 2008 during an outburst, which has recently returned to quiescence. We report its spectral and timing properties measured with new and archival observations from the Chandra X-ray Observatory, XMM-Newton, and Suzaku. We found that the quiescent spectrum is best fit by a power-law plus two blackbody model, with temperatures of kT low ∼ 0.26 keV and kT high ∼ 0.62 keV. We interpret these two blackbody components as emission from a hotspot and the entire surface. The hotspot radius shrunk from 1.4 km to 0.49 km since the outburst, and there was a significant correlation between its area and the X-ray luminosity, which agrees well with the prediction by the twisted magnetosphere model. We applied the two-temperature spectral model to all magnetars in quiescence and found that it could be a common feature among the population. Moreover, the temperature of the cooler blackbody shows a general trend with the magnetar field strength, which supports the simple scenario of heating by magnetic field decay.

The Project LITE Spectrum Explorer

NASA Astrophysics Data System (ADS)

Brecher, K.; Carr, P.; Garik, P.; Weeks, E.

2002-12-01

We are developing a powerful new software tool which can help students at all levels understand the spectral properties of light. As a recent AAS survey of astronomy faculty members found (The Physics Teacher, 39, 52, 2001), essentially all introductory astronomy courses spend a significant amount of time dealing with the nature of light. Among the most difficult concepts for students to master are Kirchhoff's laws, blackbody radiation, the Stefan-Boltzmann law, Wien's law, the nature and causes of emission and absorption lines, and the relation of spectra to the underlying astronomical and physical processes producing them. Students often seem baffled by the connection between a spectrum seen visually as a color band and the same spectrum plotted graphically as intensity versus wavelength or frequency. The "Spectrum Explorer", a JAVA applet, is being developed as part of "Project LITE: Light Inquiry Through Experiments" to address these issues. It can be used by instructors in lecture presentations and by students learning at home or working in laboratory settings. We will show some of the current capabilities of the software which include simultaneous display of multiple spectra (normalized and non-normalized as a function of either wavelength or frequency) and the ability to manipulate blackbody spectra. Our future development plans include the addition of a variety of spectral data sets (from physics and chemistry as well as from astronomy); computed inputs from basic quantum mechanics (e.g. Zeeman effect in hydrogen) and from astronomical models (e.g. time varying spectra in binary stars); and the ability to test the effect of filters and physical processes (e.g. Rayleigh scattering) on input spectra. The Spectrum Explorer (along with many other applets about both the physical and perceptual nature of light) can be found on the Project LITE web site http://lite.bu.edu. Project LITE is supported by Grant #DUE-0125992 from the National Science Foundation Division of Undergraduate Education.

Two new intermediate polars with a soft X-ray component

NASA Astrophysics Data System (ADS)

Anzolin, G.; de Martino, D.; Bonnet-Bidaud, J.-M.; Mouchet, M.; Gänsicke, B. T.; Matt, G.; Mukai, K.

2008-10-01

Aims: We analyze the first X-ray observations with XMM-Newton of 1RXS J070407.9+262501 and 1RXS 180340.0+401214, in order to characterize their broad-band temporal and spectral properties, also in the UV/optical domain, and to confirm them as intermediate polars. Methods: For both objects, we performed a timing analysis of the X-ray and UV/optical light curves to detect the white dwarf spin pulsations and study their energy dependence. For 1RXS 180340.0+401214 we also analyzed optical spectroscopic data to determine the orbital period. X-ray spectra were analyzed in the 0.2-10.0 keV range to characterize the emission properties of both sources. Results: We find that the X-ray light curves of both systems are energy dependent and are dominated, below 3-5 keV, by strong pulsations at the white dwarf rotational periods (480 s for 1RXS J070407.9+262501 and 1520.5 s for 1RXS 180340.0+401214). In 1RXS 180340.0+401214 we also detect an X-ray beat variability at 1697 s which, together with our new optical spectroscopy, favours an orbital period of 4.4 h that is longer than previously estimated. Both systems show complex spectra with a hard (temperature up to 40 keV) optically thin and a soft (kT ~ 85-100 eV) optically thick components heavily absorbed by material partially covering the X-ray sources. Conclusions: Our observations confirm the two systems as intermediate polars and also add them as new members of the growing group of “soft” systems which show the presence of a soft X-ray blackbody component. Differences in the temperatures of the blackbodies are qualitatively explained in terms of reprocessing over different sizes of the white dwarf spot. We suggest that systems showing cooler soft X-ray blackbody components also possess white dwarfs irradiated by cyclotron radiation. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA, and with the Observatoire de Haute Provence (CNRS), France.

New blackbody standard for the evaluation and calibration of tympanic ear thermometers at the NPL, United Kingdom

NASA Astrophysics Data System (ADS)

McEvoy, Helen C.; Simpson, Robert; Machin, Graham

2004-04-01

The use of infrared tympanic thermometers for monitoring patient health is widespread. However, studies into the performance of these thermometers have questioned their accuracy and repeatability. To give users confidence in these devices, and to provide credibility in the measurements, it is necessary for them to be tested using an accredited, standard blackbody source, with a calibration traceable to the International Temperature Scale of 1990 (ITS-90). To address this need the National Physical Laboratory (NPL), UK, has recently set up a primary ear thermometer calibration (PET-C) source for the evaluation and calibration of tympanic (ear) thermometers over the range from 15 °C to 45 °C. The overall uncertainty of the PET-C source is estimated to be +/- 0.04 °C at k = 2. The PET-C source meets the requirements of the European Standard EN 12470-5: 2003 Clinical thermometers. It consists of a high emissivity blackbody cavity immersed in a bath of stirred liquid. The temperature of the blackbody is determined using an ITS-90 calibrated platinum resistance thermometer inserted close to the rear of the cavity. The temperature stability and uniformity of the PET-C source was evaluated and its performance validated. This paper provides a description of the PET-C along with the results of the validation measurements. To further confirm the performance of the PET-C source it was compared to the standard ear thermometer calibration sources of the National Metrology Institute of Japan (NMIJ), Japan and the Physikalisch-Technische Bundesanstalt (PTB), Germany. The results of this comparison will also be briefly discussed. The PET-C source extends the capability for testing ear thermometers offered by the NPL body temperature fixed-point source, described previously. An update on the progress with the commercialisation of the fixed-point source will be given.

XMM-Newton Archival Study of the ULX Population in Nearby Galaxies

NASA Technical Reports Server (NTRS)

Winter, Lisa M.; Mushotzky, Richard; Reynolds, Christopher S.

2005-01-01

We have conducted an archival XMM-Newton study of the bright X-ray point sources in 32 nearby galaxies. From our list of approximately 100 point sources, we attempt to determine if there is a low-state counterpart to the Ultraluminous X-ray (ULX) population. Indeed, 16 sources in our sample match the criteria we set for a low-state ULX, namely, L(sub X) greater than 10(exp 38 ergs per second) and a spectrum best fit with an absorbed power law. Further, we find evidence for 26 high-state ULXs which are best fit by a combined blackbody and a power law. As in Galactic black hole systems, the spectral indices, GAMMA, of the low-state objects, as well a s the luminosities, tend to be lower than those of the high-state objects. The observed range of blackbody temperatures is 0.1-1 keV with the most luminous systems tending toward the lowest temperatures. We also find a class of object whose properties (luminosity, blackbody temperature, and power law slopes) are very similar to those of galactic stellar mass black holes. In addition, we find a subset of these objects that can be best fit by a Comptonized spectrum similar to that used for Galactic black holes in the very high state, when they are radiating near the Eddington limit.

Noncontact true temperature measurement, 2

NASA Technical Reports Server (NTRS)

Lee, Mark C.; Allen, James L.

1988-01-01

A laser pyrometer was developed for acquiring the true temperature of a levitated sample. The reflectivity is measured by first expanding the laser beam to cover the entire cross-sectional surface of the diffuse target. The reflectivity calibration of this system is determined from the surface emissivity of a target with a blackbody cavity. The emissivity of the real target can then be calculated. The overall system constant is obtained by passively measuring the radiance of the blackbody cavity (emissivity = 1.0) at a known, arbitrary temperature. Since the photosensor used is highly linear over the entire operating temperature range, the true temperature of the target can then be computed. The latest results available from this on-going research indicate that true temperatures thus obtained are in very good quantitative agreement with thermocouple measured temperatures.

Long-Term Stability of WC-C Peritectic Fixed Point

NASA Astrophysics Data System (ADS)

Khlevnoy, B. B.; Grigoryeva, I. A.

2015-03-01

The tungsten carbide-carbon peritectic (WC-C) melting transition is an attractive high-temperature fixed point with a temperature of . Earlier investigations showed high repeatability, small melting range, low sensitivity to impurities, and robustness of WC-C that makes it a prospective candidate for the highest fixed point of the temperature scale. This paper presents further study of the fixed point, namely the investigation of the long-term stability of the WC-C melting temperature. For this purpose, a new WC-C cell of the blackbody type was built using tungsten powder of 99.999 % purity. The stability of the cell was investigated during the cell aging for 50 h at the cell working temperature that tooks 140 melting/freezing cycles. The method of investigation was based on the comparison of the WC-C tested cell with a reference Re-C fixed-point cell that reduces an influence of the probable instability of a radiation thermometer. It was shown that after the aging period, the deviation of the WC-C cell melting temperature was with an uncertainty of.

Teaching climate change in undergraduate courses

NASA Astrophysics Data System (ADS)

Sadler, Michael

2013-04-01

Although anthropogenic climate change is generally accepted in the scientific community, there is considerable skepticism among the general population and, therefore, in undergraduate students of all majors. Students are often asked by their peers, family members, and others, whether they ``believe'' climate change is occurring and what should be done about it (if anything). I will present my experiences and recommendations for teaching the physics of climate change to both physics and non-science majors. For non-science majors, the basic approach is to try to develop an appreciation for the scientific method (particularly peer-reviewed research) in a course on energy and the environment. For physics majors, the pertinent material is normally covered in their undergraduate courses in modern physics and thermodynamics. Nevertheless, it helps to review the basics, e.g. introductory quantum mechanics (discrete energy levels of atomic systems), molecular spectroscopy, and blackbody radiation. I have done this in a separate elective topics course, titled ``Physics of Climate Change,'' to help the students see how their knowledge gives them insight into a topic that is very volatile (socially and politically).

Detection of the thermal component in GRB 160107A

NASA Astrophysics Data System (ADS)

Kawakubo, Yuta; Sakamoto, Takanori; Nakahira, Satoshi; Yamaoka, Kazutaka; Serino, Motoko; saoka, Yoichi; Cherry, Michael L.; Matsukawa, Shohei; Mori, Masaki; Nakagawa, Yujin; Ozawa, Shunsuke; Penacchioni, Ana V.; Ricciarini, Sergio B.; Tezuka, Akira; Torii, Shoji; Yamada, Yusuke; Yoshida, Atsumasa

2018-01-01

We present the detection of a blackbody component in gamma-ray burst GRB 160107A emission by using the combined spectral data of the CALET Gamma-ray Burst Monitor (CGBM) and the MAXI Gas Slit Camera (GSC). MAXI/GSC detected the emission ˜45 s prior to the main burst episode observed by the CGBM. The MAXI/GSC and the CGBM spectrum of this prior emission period is fitted well by a blackbody with temperature 1.0^{+0.3}_{-0.2} keV plus a power law with a photon index of -1.6 ± 0.3. We discuss the radius of the photospheric emission and the main burst emission based on the observational properties. We stress the importance of coordinated observations via various instruments collecting high-quality data over a broad energy coverage in order to understand the GRB prompt emission mechanism.

Fiber-coupled superconducting nanowire single-photon detectors integrated with a bandpass filter on the fiber end-face

NASA Astrophysics Data System (ADS)

Zhang, W. J.; Yang, X. Y.; Li, H.; You, L. X.; Lv, C. L.; Zhang, L.; Zhang, C. J.; Liu, X. Y.; Wang, Z.; Xie, X. M.

2018-07-01

Superconducting nanowire single-photon detectors (SNSPDs) with both high system detection efficiency (SDE) and low dark count rate (DCR) play significant roles in quantum information processes and various applications. The background dark counts of SNSPDs originate from the room temperature blackbody radiation coupled to the device via a fiber. Therefore, a bandpass filter (BPF) operated at low temperature with minimal insert loss is necessary to suppress the background DCR. Herein, a low-loss BPF integrated on a single-mode fiber end-face was designed, fabricated and verified for the low temperature implement. The fiber end-face BPF was featured with a typical passband width about 40 nm in the 1550 nm telecom band and a peak transmittance of over 0.98. SNSPD with high SDE fabricated on a distributed Bragg reflector was coupled to the BPF. The device with such a BPF showed an SDE of 80% at a DCR of 0.5 Hz, measured at 2.1 K. Compared the same device without a BPF, the DCR was reduced by over 13 dB with an SDE decrease of <3%.

Compact blackbody calibration sources for in-flight calibration of spaceborne infrared instruments

NASA Astrophysics Data System (ADS)

Scheiding, S.; Driescher, H.; Walter, I.; Hanbuch, K.; Paul, M.; Hartmann, M.; Scheiding, M.

2017-11-01

High-emissivity blackbodies are mandatory as calibration sources in infrared radiometers. Besides the requirements on the high spectral emissivity and low reflectance, constraints regarding energy consumption, installation space and mass must be considered during instrument design. Cavity radiators provide an outstanding spectral emissivity to the price of installation space and mass of the calibration source. Surface radiation sources are mainly limited by the spectral emissivity of the functional coating and the homogeneity of the temperature distribution. The effective emissivity of a "black" surface can be optimized, by structuring the substrate with the aim to enlarge the ratio of the surface to its projection. Based on the experiences of the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) calibration source MBB3, the results of the surface structuring on the effective emissivity are described analytically and compared to the experimental performance. Different geometries are analyzed and the production methods are discussed. The high-emissivity temperature calibration source features values of 0.99 for wavelength from 5 μm to 10 μm and emissivity larger than 0.95 for the spectral range from 10 μm to 40 μm.

Optimization of the thermogauge furnace for realizing high temperature fixed points

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, T.; Dong, W.; Liu, F.

2013-09-11

The thermogauge furnace was commonly used in many NMIs as a blackbody source for calibration of the radiation thermometer. It can also be used for realizing the high temperature fixed point(HTFP). According to our experience, when realizing HTFP we need the furnace provide relative good temperature uniformity to avoid the possible damage to the HTFP. To improve temperature uniformity in the furnace, the furnace tube was machined near the tube ends with a help of a simulation analysis by 'ansys workbench'. Temperature distributions before and after optimization were measured and compared at 1300 °C, 1700°C, 2500 °C, which roughly correspondmore » to Co-C(1324 °C), Pt-C(1738 °C) and Re-C(2474 °C), respectively. The results clearly indicate that through machining the tube the temperature uniformity of the Thermogage furnace can be remarkably improved. A Pt-C high temperature fixed point was realized in the modified Thermogauge furnace subsequently, the plateaus were compared with what obtained using old heater, and the results were presented in this paper.« less

YAG glass-ceramic phosphor for white LED (II): luminescence characteristics

NASA Astrophysics Data System (ADS)

Tanabe, Setsuhisa; Fujita, Shunsuke; Yoshihara, Satoru; Sakamoto, Akihiko; Yamamoto, Shigeru

2005-09-01

Optical properties of the Ce:YAG glass-ceramic (GC) phosphor for the white LED were investigated. Concentration dependence of fluorescence intensity of Ce3+:5d→4f transition in the GC showed a maximum at 0.5mol%Ce2O3. Quantum efficiency (QE) of Ce3+ fluorescence in the GC materials, the color coordinate and luminous flux of electroluminescence of LED composite were evaluated with an integrating sphere. QE increased with increasing ceramming temperature of the as-made glass. The color coordinates (x,y) of the composite were increased with increasing thickness of the GC mounted on a blue LED chip. The effect of Gd2O3 substitution on the optical properties of the GC materials was also investigated. The excitation and emission wavelength shifted to longer side up to Gd/(Y+Gd)=0.40 in molar composition. As a result, the color coordinate locus of the LED with various thickness of the GdYAG-GC shifted to closer to the Planckian locus for the blackbody radiation. These results were explained by partial substitution of Gd3+ ions in the precipitated YAG micro-crystals, leading to the increase of lattice constant of unit cell, which was confirmed by X-ray diffraction.

Chemistry and cosmology.

PubMed

Black, John H

2006-01-01

The simplest elements, hydrogen and helium, offer a remarkably rich chemistry, which has controlled crucial features of the early evolution of the universe. Theoretical models of the origin of structure (stars, galaxies, clusters of galaxies, etc.) now incorporate this chemistry in some detail. In addition to the origin of structure, cosmologists are concerned with observational tests of competing world models. Primordial chemistry may give rise to some of the earliest departures from thermodynamic equilibrium in the universe. These effects may be observable as broad-band spectroscopic distortions of the cosmic background radiation, which otherwise exhibits a nearly perfect blackbody spectrum. The chemical history of the expanding universe is followed through a detailed calculation of the evolution of the abundances of H, H+, H-, H2, H2+, H3+, and other minor species. It is shown that continuous absorption by the small concentration of H- can produce a distortion in the cosmic background spectrum with a maximum at a frequency near nu/c = 9 cm-1 (wavelength 1.1 mm). The predicted effect lies only a factor of 5 below current limits. Its detection would provide an important test of our understanding of the recombination epoch of the universe.

Near-Field Thermal Radiation for Solar Thermophotovoltaics and High Temperature Thermal Logic and Memory Applications

NASA Astrophysics Data System (ADS)

Elzouka, Mahmoud

This dissertation investigates Near-Field Thermal Radiation (NFTR) applied to MEMS-based concentrated solar thermophotovoltaics (STPV) energy conversion and thermal memory and logics. NFTR is the exchange of thermal radiation energy at nano/microscale; when separation between the hot and cold objects is less than dominant radiation wavelength (˜1 mum). NFTR is particularly of interest to the above applications due to its high rate of energy transfer, exceeding the blackbody limit by orders of magnitude, and its strong dependence on separation gap size, surface nano/microstructure and material properties. Concentrated STPV system converts solar radiation to electricity using heat as an intermediary through a thermally coupled absorber/emitter, which causes STPV to have one of the highest solar-to-electricity conversion efficiency limits (85.4%). Modeling of a near-field concentrated STPV microsystem is carried out to investigate the use of STPV based solid-state energy conversion as high power density MEMS power generator. Numerical results for In 0.18Ga0.82Sb PV cell illuminated with tungsten emitter showed significant enhancement in energy transfer, resulting in output power densities as high as 60 W/cm2; 30 times higher than the equivalent far-field power density. On thermal computing, this dissertation demonstrates near-field heat transfer enabled high temperature NanoThermoMechanical memory and logics. Unlike electronics, NanoThermoMechanical memory and logic devices use heat instead of electricity to record and process data; hence they can operate in harsh environments where electronics typically fail. NanoThermoMechanical devices achieve memory and thermal rectification functions through the coupling of near-field thermal radiation and thermal expansion in microstructures, resulting in nonlinear heat transfer between two temperature terminals. Numerical modeling of a conceptual NanoThermoMechanical is carried out; results include the dynamic response under write/read cycles for a practical silicon-based device. NanoThermoMechanical rectification is achieved experimentally--for the first time--with measurements at a high temperature of 600 K, demonstrating the feasibility of NanoThermoMechanical to operate in harsh environments. The proof-of-concept device has shown a maximum rectification of 10.9%. This dissertation proposes using meshed photonic crystal structures to enhance NFTR between surfaces. Numerical results show thermal rectification as high as 2500%. Incorporating these structures in thermal memory and rectification devices will significantly enhance their functionality and performance.

Ground-based remote sensing of thin clouds in the Arctic

NASA Astrophysics Data System (ADS)

Garrett, T. J.; Zhao, C.

2013-05-01

This paper describes a method for using interferometer measurements of downwelling thermal radiation to retrieve the properties of single-layer clouds. Cloud phase is determined from ratios of thermal emission in three "micro-windows" at 862.5 cm-1, 935.8 cm-1, and 988.4 cm-1 where absorption by water vapour is particularly small. Cloud microphysical and optical properties are retrieved from thermal emission in the first two of these micro-windows, constrained by the transmission through clouds of primarily stratospheric ozone emission at 1040 cm-1. Assuming a cloud does not approximate a blackbody, the estimated 95% confidence retrieval errors in effective radius re, visible optical depth τ, number concentration N, and water path WP are, respectively, 10%, 20%, 38% (55% for ice crystals), and 16%. Applied to data from the Atmospheric Radiation Measurement programme (ARM) North Slope of Alaska - Adjacent Arctic Ocean (NSA-AAO) site near Barrow, Alaska, retrievals show general agreement with both ground-based microwave radiometer measurements of liquid water path and a method that uses combined shortwave and microwave measurements to retrieve re, τ and N. Compared to other retrieval methods, advantages of this technique include its ability to characterise thin clouds year round, that water vapour is not a primary source of retrieval error, and that the retrievals of microphysical properties are only weakly sensitive to retrieved cloud phase. The primary limitation is the inapplicability to thicker clouds that radiate as blackbodies and that it relies on a fairly comprehensive suite of ground based measurements.

DOE Research and Development Accomplishments Interesting Insights

Science.gov Websites

There secrets powering the stars [Bethe] Synthesis of the Elements in the Stars [Fowler] blackbody form organic synthesis [Schrock/Grubbs] provided the theoretical explanation of the fractional quantum Hall

A survey of eight hot Jupiters in secondary eclipse using WIRCam at CFHT

NASA Astrophysics Data System (ADS)

Martioli, Eder; Colón, Knicole D.; Angerhausen, Daniel; Stassun, Keivan G.; Rodriguez, Joseph E.; Zhou, George; Gaudi, B. Scott; Pepper, Joshua; Beatty, Thomas G.; Tata, Ramarao; James, David J.; Eastman, Jason D.; Wilson, Paul Anthony; Bayliss, Daniel; Stevens, Daniel J.

2018-03-01

We present near-infrared high-precision photometry for eight transiting hot Jupiters observed during their predicted secondary eclipses. Our observations were carried out using the staring mode of the WIRCam instrument on the Canada-France-Hawaii Telescope (CFHT). We present the observing strategies and data reduction methods which delivered time series photometry with statistical photometric precision as low as 0.11 per cent. We performed a Bayesian analysis to model the eclipse parameters and systematics simultaneously. The measured planet-to-star flux ratios allowed us to constrain the thermal emission from the day side of these hot Jupiters, as we derived the planet brightness temperatures. Our results combined with previously observed eclipses reveal an excess in the brightness temperatures relative to the blackbody prediction for the equilibrium temperatures of the planets for a wide range of heat redistribution factors. We find a trend that this excess appears to be larger for planets with lower equilibrium temperatures. This may imply some additional sources of radiation, such as reflected light from the host star and/or thermal emission from residual internal heat from the formation of the planet.

Nist Microwave Blackbody: The Design, Testing, and Verification of a Conical Brightness Temperature Source

NASA Astrophysics Data System (ADS)

Houtz, Derek Anderson

Microwave radiometers allow remote sensing of earth and atmospheric temperatures from space, anytime, anywhere, through clouds, and in the dark. Data from microwave radiometers are high-impact operational inputs to weather forecasts, and are used to provide a vast array of climate data products including land and sea surface temperatures, soil moisture, ocean salinity, cloud precipitation and moisture height profiles, and even wind speed and direction, to name a few. Space-borne microwave radiometers have a major weakness when it comes to long-term climate trends due to their lack of traceability. Because there is no standard, or absolute reference, for microwave brightness temperature, nationally or internationally, individual instruments must each rely on their own internal calibration source to set an absolute reference to the fundamental unit of Kelvin. This causes each subsequent instrument to have a calibration offset and there is no 'true' reference. The work introduced in this thesis addresses this vacancy by proposing and introducing a NIST microwave brightness temperature source that may act as the primary reference. The NIST standard will allow pre-launch calibration of radiometers across a broad range of remote sensing pertinent frequencies between 18 GHz and 220 GHz. The blackbody will be capable of reaching temperatures ranging between liquid nitrogen boiling at approximately 77 K and warm-target temperature of 350 K. The brightness temperature of the source has associated standard uncertainty ranging as a function of frequency between 0.084 K and 0.111 K. The standard can be transferred to the calibration source in the instrument, providing traceability of all subsequent measurements back to the primary standard. The development of the NIST standard source involved predicting and measuring its brightness temperature, and minimizing the associated uncertainty of this quantity. Uniform and constant physical temperature along with well characterized and maximized emissivity are fundamental to a well characterized blackbody. The chosen geometry is a microwave absorber coated copper cone. Electromagnetic and thermal simulations are introduced to optimize the design. Experimental verifications of the simulated quantities confirm the predicted performance of the blackbody.

EVIDENCE OF SPREADING LAYER EMISSION IN A THERMONUCLEAR SUPERBURST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koljonen, K. I. I.; Kajava, J. J. E.; Kuulkers, E., E-mail: karri.koljonen@nyu.edu

2016-10-01

When a neutron star (NS) accretes matter from a companion star in a low-mass X-ray binary, the accreted gas settles onto the stellar surface through a boundary/spreading layer. On rare occasions the accumulated gas undergoes a powerful thermonuclear superburst powered by carbon burning deep below the NS atmosphere. In this paper, we apply the non-negative matrix factorization spectral decomposition technique to show that the spectral variations during a superburst from 4U 1636–536 can be explained by two distinct components: (1) the superburst emission characterized by a variable temperature blackbody radiation component and (2) a quasi-Planckian component with a constant, ∼2.5more » keV, temperature varying by a factor of ∼15 in flux. The spectrum of the quasi-Planckian component is identical in shape and characteristics to the frequency-resolved spectra observed in the accretion/persistent spectrum of NS low-mass X-ray binaries and agrees well with the predictions of the spreading layer model by Inogamov and Sunyaev. Our results provide yet more observational evidence that superbursts—and possibly also normal X-ray bursts—induce changes in the disc–star boundary.« less

Far-infrared observations of a star-forming region in the Corona Australis dark cloud

NASA Technical Reports Server (NTRS)

Cruz-Gonzalez, I.; Mcbreen, B.; Fazio, G. G.

1984-01-01

A high-resolution far-IR (40-250-micron) survey of a 0.9-sq-deg section of the core region of the Corona Australis dark cloud (containing very young stellar objects such as T Tauri stars, Herbig Ae and Be stars, Herbig-Haro objects, and compact H II regions) is presented. Two extended far-IR sources were found, one associated with the Herbig emission-line star R CrA and the other with the irregular emission-line variable star TY CrA. The two sources have substantially more far-IR radiation than could be expected from a blackbody extrapolation of their near-IR fluxes. The total luminosities of these sources are 145 and 58 solar luminosity, respectively, implying that the embedded objects are of intermediate or low mass. The infrared observations of the sources associated with R CrA and TY CrA are consistent with models of the evolution of protostellar envelopes of intermediate mass. However, the TY CrA source appears to have passed the evolutionary stage of expelling most of the hot dust near the central source, yielding an age of about 1 Myr.

Thermalization of a two-dimensional photonic gas in a `white wall' photon box

NASA Astrophysics Data System (ADS)

Klaers, Jan; Vewinger, Frank; Weitz, Martin

2010-07-01

Bose-Einstein condensation, the macroscopic accumulation of bosonic particles in the energetic ground state below a critical temperature, has been demonstrated in several physical systems. The perhaps best known example of a bosonic gas, blackbody radiation, however exhibits no Bose-Einstein condensation at low temperatures. Instead of collectively occupying the lowest energy mode, the photons disappear in the cavity walls when the temperature is lowered-corresponding to a vanishing chemical potential. Here we report on evidence for a thermalized two-dimensional photon gas with a freely adjustable chemical potential. Our experiment is based on a dye-filled optical microresonator, acting as a `white wall' box for photons. Thermalization is achieved in a photon-number-conserving way by photon scattering off the dye molecules, and the cavity mirrors provide both an effective photon mass and a confining potential-key prerequisites for the Bose-Einstein condensation of photons. As a striking example of the unusual system properties, we demonstrate a yet unobserved light concentration effect into the centre of the confining potential, an effect with prospects for increasing the efficiency of diffuse solar light collection.

Methods of teaching the physics of climate change in undergraduate physics courses

NASA Astrophysics Data System (ADS)

Sadler, Michael

2015-04-01

Although anthropogenic climate change is generally accepted in the scientific community, there is considerable skepticism among the general population and, therefore, in undergraduate students of all majors. Students are often asked by their peers, family members, and others, whether they ``believe'' climate change is occurring and what should be done about it (if anything). I will present my experiences and recommendations for teaching the physics of climate change to both physics and non-science majors. For non-science majors, the basic approach is to try to develop an appreciation for the scientific method (particularly peer-reviewed research) in a course on energy and the environment. For physics majors, the pertinent material is normally covered in their undergraduate courses in modern physics and thermodynamics. Nevertheless, it helps to review the basics, e.g. introductory quantum mechanics (discrete energy levels of atomic systems), molecular spectroscopy, and blackbody radiation. I have done this in a separate elective topics course, titled ``Physics of Climate Change,'' to help the students see how their knowledge gives them insight into a topic that is very volatile (socially and politically).

Calibration of the COBE FIRAS instrument

NASA Technical Reports Server (NTRS)

Fixsen, D. J.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Hewagama, T.; Isaacman, R. B.; Jensen, K. A.; Mather, J. C.; Massa, D. L.; Meyer, S. S.

1994-01-01

The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite was designed to accurately measure the spectrum of the cosmic microwave background radiation (CMBR) in the frequency range 1-95/cm with an angular resolution of 7 deg. We describe the calibration of this instrument, including the method of obtaining calibration data, reduction of data, the instrument model, fitting the model to the calibration data, and application of the resulting model solution to sky observations. The instrument model fits well for calibration data that resemble sky condition. The method of propagating detector noise through the calibration process to yield a covariance matrix of the calibrated sky data is described. The final uncertainties are variable both in frequency and position, but for a typical calibrated sky 2.6 deg square pixel and 0.7/cm spectral element the random detector noise limit is of order of a few times 10(exp -7) ergs/sq cm/s/sr cm for 2-20/cm, and the difference between the sky and the best-fit cosmic blackbody can be measured with a gain uncertainty of less than 3%.

A simple blackbody simulator with several possibilities and applications on thermography

NASA Astrophysics Data System (ADS)

dos Santos, Laerte; Lemos, Alisson Maria; Abi-Ramia, Marco Antônio

2016-05-01

Originally designed to make the practical examination on thermography certification1 possible, the device presented in this paper has demonstrated to be a very useful and versatile didactic tool for training centers and educational institutions, it can also be used as a low cost blackbody simulator to verify calibration of radiometers. It is a simple device with several functionalities for studying and for applications on heat transfer and radiometry, among them the interesting ability to thermally simulate the surface of real objects. On that functionality, if the device is seen by a thermographic camera, it reproduces the surface apparent temperatures of the object that it is simulating, at the same time, if it is seen by a naked eye it shows a visible image of that same surface. This functionality makes the practical study in the classroom possible, from different areas such as electrical, mechanical, medical, building, veterinary, etc.

Fourier transform spectrometer for spectral emissivity measurement in the temperature range between 60 and 1500°C

NASA Astrophysics Data System (ADS)

Dai, Jingmin; Wang, Xinbei; Yuan, Guibin

2005-01-01

A new spectral emissivity measurement system has been developed at Harbin Institute of Technology (HIT) by using a Fourier transform infrared (FTIR) spectrometer. The spectral range between 0.6 and 25 µm was covered by a photovoltaic HgCdTe and a silicon photodiode detector. A SiC heater with a black hole was employed for heating the sample. The temperature of the sample can be controlled in a range between 60 and 1500°C with an error of less than 1°C. The system was calibrated against two high quality reference blackbodies: a low temperature heat-pipe blackbody operated in the temperature range between 60°C and 300°C and a high temperature blackbody with SiC heater operated in the temperature range between 300°C and 1500°C. Several tests were done for this new system. The estimated uncertainty of emissivity measurement is better than 3%.

Analytic evaluation of the weighting functions for remote sensing of blackbody planetary atmospheres : the case of limb viewing geometry

NASA Technical Reports Server (NTRS)

Ustinov, Eugene A.

2006-01-01

In a recent publication (Ustinov, 2002), we proposed an analytic approach to evaluation of radiative and geophysical weighting functions for remote sensing of a blackbody planetary atmosphere, based on general linearization approach applied to the case of nadir viewing geometry. In this presentation, the general linearization approach is applied to the limb viewing geometry. The expressions, similar to those obtained in (Ustinov, 2002), are obtained for weighting functions with respect to the distance along the line of sight. Further on, these expressions are converted to the expressions for weighting functions with respect to the vertical coordinate in the atmosphere. Finally, the numerical representation of weighting functions in the form of matrices of partial derivatives of grid limb radiances with respect to the grid values of atmospheric parameters is used for a convolution with the finite field of view of the instrument.

A blackbody-pumped CO2-N2 transfer laser

NASA Astrophysics Data System (ADS)

Deyoung, R. J.; Higdon, N. S.

1984-08-01

A compact blackbody-pumped CO2-N2 transfer laser was constructed and the significant operating parameters were investigated. Lasing was achieved at 10.6 microns by passing preheated N2 through a 1.5-mm-diameter nozzle to a laser cavity where the N2 was mixed with CO2 and He. An intrinsic efficiency of 0.7 percent was achieved for an oven temperature of 1473 K and N2 oven pressure of 440 torr. The optimum laser cavity consisted of a back mirror with maximum reflectivity and an output mirror with 97.5-percent reflectivity. The optimum gas mixture was 1CO2/.5He/6N2. The variation of laser output was measured as a function of oven temperature, nozzle diameter, N2 oven pressure, He and CO2 partial pressures, nozzle-to-oven separation, laser cell temperature, and output laser mirror reflectivity. With these parameters optimized, outputs approaching 1.4 watts were achieved.

Time-Resolved Properties and Global Trends in dMe Flares from Simultaneous Photometry and Spectra

NASA Astrophysics Data System (ADS)

Kowalski, Adam F.

We present a homogeneous survey of near-ultraviolet (NUV) /optical line and continuum emission during twenty M dwarf flares with simultaneous, high cadence photometry and spectra. These data were obtained to study the white-light continuum components to the blue and red of the Balmer jump to break the degeneracy with fitting emission mechanisms to broadband colors and to provide constraints for radiative-hydrodynamic flare models that seek to reproduce the white-light flare emission. The main results from the continuum analysis are the following: 1) the detection of Balmer continuum (in emission) that is present during all flares, with a wide range of relative contribution to the continuum flux in the NUV; 2) a blue continuum at the peak of the photometry that is linear with wavelength from λ = 4000 - 4800Å, matched by the spectral shape of hot, blackbody emission with typical temperatures of 10 000 - 12 000 K; 3) a redder continuum apparent at wavelengths longer than Hβ; this continuum becomes relatively more important to the energy budget during the late gradual phase. The hot blackbody component and redder continuum component (which we call "the conundruum") have been detected in previous UBVR colorimetry studies of flares. With spectra, one can compare the properties and detailed timings of all three components. Using time-resolved spectra during the rise phase of three flares, we calculate the speed of an expanding flare region assuming a simple geometry; the speeds are found to be ~5- 10 km s-1 and 50 - 120 km s -1, which are strikingly consistent with the speeds at which two-ribbon flares develop on the Sun. The main results from the emission line analysis are 1) the presentation of the "time-decrement", a relation between the timescales of the Balmer series; 2) a Neupert-like relation between Ca \\pcy K and the blackbody continuum, and 3) the detection of absorption wings in the Hydrogen Balmer lines during times of peak continuum emission, indicative of hot-star spectra forming during the flare. A byproduct of this study is a new method for deriving absolute fluxes during M dwarf flare observations obtained from narrow-slit spectra or during variable weather conditions. This technique allows us to analyze the spectra and photometry independently of one another, in order to connect the spectral properties to the rise, peak, and decay phases of broadband light curve morphology. We classify the light curve morphology according to an "impulsiveness index" and find that the fast (impulsive) flares have less Balmer continuum at peak emission than the slow (gradual) flares. In the gradual phase, the energy budget of the flare spectrum during almost all flares has a larger contribution from the Hydrogen Balmer component than in the impulsive phase, suggesting that the heating and cooling processes evolve over the course of a flare. We find that, in general, the evolution of the hot blackbody is rapid, and that the blackbody temperature decreases to ~8000 K in the gradual phase. The Balmer continuum evolves more slowly than the blackbody ¨C similar to the higher order Balmer lines but faster than the lower order Balmer lines. The height of the Balmer jump increases during the gradual decay phase. We model the Balmer continuum emission using the RHD F11 model spectrum from Allred et al. (2006), but we discuss several important systematic uncertainties in relating the apparent amount of Balmer continuum to a given RHD beam model. Good fits to the shape of the RHD F11 model spectrum are not obtained at peak times, in contrast to the gradual phase. We model the blackbody component using model hot star atmospheres from Castelli & Kurucz (2004) in order to account for the effects of flux redistribution in the flare atmosphere. This modeling is motivated by observations during a secondary flare in the decay phase of a megaflare, when the newly formed flare spectrum resembled that of Vega with the Balmer continuum and lines in absorption. We model this continuum phenomenologically with the RH code using hot spots placed at high column mass in the M dwarf quiescent atmosphere; a superposition of hot spot models and the RHD model are used to explain the anti-correlation in the apparent amount of Balmer continuum in emission and the U-band light curve. We attempt to reproduce the blackbody component in self-consistent 1D radiative hydrodynamic flare models using the RADYN code. We simulate the flare using a solar-type nonthermal electron beam heating function with a total energy flux of 1012 ergs cm-2 s-1 (F12) for a duration of 5 seconds and a subsequent gradual phase. Although there is a larger amount of NUV backwarming at log mc/(1g cm-2)~0 than in the F11 model, the resulting flare continuum shape is similar to the F11 model spectrum with a larger Balmer jump and a much redder spectral shape than is seen in the observations. We do not find evidence of white-light emitting chromospheric condensations, in contrast to the previous F12 model of Livshits et al. (1981). We discuss future avenues for RHD modeling in order to produce a hot blackbody component, including the treatment of nonthermal protons in M dwarf flares.

A blackbody-pumped CO2-N2 transfer laser

NASA Technical Reports Server (NTRS)

Deyoung, R. J.; Higdon, N. S.

1984-01-01

A compact blackbody-pumped CO2-N2 transfer laser was constructed and the significant operating parameters were investigated. Lasing was achieved at 10.6 microns by passing preheated N2 through a 1.5-mm-diameter nozzle to a laser cavity where the N2 was mixed with CO2 and He. An intrinsic efficiency of 0.7 percent was achieved for an oven temperature of 1473 K and N2 oven pressure of 440 torr. The optimum laser cavity consisted of a back mirror with maximum reflectivity and an output mirror with 97.5-percent reflectivity. The optimum gas mixture was 1CO2/.5He/6N2. The variation of laser output was measured as a function of oven temperature, nozzle diameter, N2 oven pressure, He and CO2 partial pressures, nozzle-to-oven separation, laser cell temperature, and output laser mirror reflectivity. With these parameters optimized, outputs approaching 1.4 watts were achieved.

X-Ray Brightening and UV Fading of Tidal Disruption Event ASASSN-15oi

NASA Astrophysics Data System (ADS)

Gezari, S.; Cenko, S. B.; Arcavi, I.

2017-12-01

We present late-time observations by Swift and XMM-Newton of the tidal disruption event (TDE) ASASSN-15oi that reveal that the source brightened in the X-rays by a factor of ∼10 one year after its discovery, while it faded in the UV/optical by a factor of ∼100. The XMM-Newton observations measure a soft X-ray blackbody component with {{kT}}{bb}∼ 45 {eV}, corresponding to radiation from several gravitational radii of a central ∼ {10}6 {M}ȯ black hole. The last Swift epoch taken almost 600 days after discovery shows that the X-ray source has faded back to its levels during the UV/optical peak. The timescale of the X-ray brightening suggests that the X-ray emission could be coming from delayed accretion through a newly forming debris disk and that the prompt UV/optical emission is from the prior circularization of the disk through stream–stream collisions. The lack of spectral evolution during the X-ray brightening disfavors ionization breakout of a TDE “veiled” by obscuring material. This is the first time a TDE has been shown to have a delayed peak in soft X-rays relative to the UV/optical peak, which may be the first clear signature of the real-time assembly of a nascent accretion disk, and provides strong evidence for the origin of the UV/optical emission from circularization, as opposed to reprocessed emission of accretion radiation.

The turning point for Einstein's Annus mirabilis

NASA Astrophysics Data System (ADS)

Rynasiewicz, Robert; Renn, Jürgen

The year 1905 has been called Einstein's Annus mirabilis because of three ground-breaking works completed over the span of a few months-the light-quantum paper, the Brownian motion paper, and the paper on the electrodynamics of moving bodies introducing the special theory of relativity. There are prima facie reasons for thinking that the origins of these papers cannot be understood in isolation from one another. Due to space limitations, we concentrate primarily on the light quantum paper, since, in key respects, it marks the turning point for the Annus mirabilis. The task is to probe, not just how the idea of the light quantum might have occurred to Einstein, but, more importantly, what convinced him that the idea was not just a quixotic hypothesis, but an unavoidable and demonstrable feature of radiation. The crucial development, we suggest, arose from comparing the energy fluctuations that follow rigorously from the Stefan-Boltzmann law, as well as from Wien's distribution formula for blackbody radiation, with what it is reasonable to expect from Maxwell's electromagnetic theory of light. A special case of this is addressed in Einstein's one paper from 1904, "Zur allgemeinen molekularen Theorie der Wärme". Annalen der Physik, 14, 355-362 (Also in CPAE, Vol. 2, Doc. 5)]. The outcome for the general case leads naturally to the central theoretical argument of the light quantum paper, the expectation of Brownian-like motion, and several of the key results for the electrodynamics of moving bodies.

Dynamic Modulation of Radiative Heat Transfer beyond the Blackbody Limit.

PubMed

Ito, Kota; Nishikawa, Kazutaka; Miura, Atsushi; Toshiyoshi, Hiroshi; Iizuka, Hideo

2017-07-12

Dynamic control of electromagnetic heat transfer without changing mechanical configuration opens possibilities in intelligent thermal management in nanoscale systems. We confirmed by experiment that the radiative heat transfer is dynamically modulated beyond the blackbody limit. The near-field electromagnetic heat exchange mediated by phonon-polariton is controlled by the metal-insulator transition of tungsten-doped vanadium dioxide. The functionalized heat flux is transferred over an area of 1.6 cm 2 across a 370 nm gap, which is maintained by the microfabricated spacers and applied pressure. The uniformity of the gap is validated by optical interferometry, and the measured heat transfer is well modeled as the sum of the radiative and the parasitic conductive components. The presented methodology to form a nanometric gap with functional heat flux paves the way to the smart thermal management in various scenes ranging from highly integrated systems to macroscopic apparatus.

On the dissociation and conformation of gas-phase methonium ions

PubMed Central

Gross, Deborah S.

2005-01-01

The dissociation pathways of both doubly and singly charged methonium ions, (CH3)3N+ –(CH2)n–+N(CH3)3·X− (n = 6,10; X = Br, I, and OAc), are measured using blackbody infrared radiative dissociation (BIRD) and SORI–CAD in a Fourier transform mass spectrometer. SORI–CAD of the doubly charged decamethonium ions results primarily in the formation of even electron ions by hydrogen rearrangements. In contrast, homolytic bond cleavage to form two odd electron ions is highly favored in the hexamethonium ion, presumably due to increased Coulomb repulsion in this ion. For BIRD of the singly charged salts, ions are mass selected and dissociated by heating the vacuum chamber to elevated temperatures. Under the low pressure conditions of our experiment, energy is transferred from the chamber walls to the ions by the absorption of blackbody radiation. From the temperature dependence of the unimolecular rate constants for dissociation, Arrhenius activation energies in the zero-pressure limit are obtained. The primary dissociation pathways correspond to counterion substitution reactions which result in loss of N(CH3)3 and CH3X. For hexamethonium and decamethonium with X = Br or I, the branching ratios for these pathways differ dramatically; the ratio of loss of N(CH3)3 and CH3Br is 3.8 and 0.4 for hexamethonium and decamethonium bromide, respectively. The hexamethonium acetate salt has a branching ratio of 0.1. The Arrhenius activation energies for hexamethonium (Br or I) and decamethonium (Br or I) are 0.9 and 1.0 eV, respectively. This value for hexamethonium acetate is 0.6 eV. Molecular dynamics simulations and Monte Carlo conformation searching are used to obtain the lowest energy structures of hexamethonium and decamethonium bromide. These calculations indicate that the methonium ion folds around the counterion to form a cyclic salt-bridge structure in which both quaternary nitrogens interact with the oppositely charged counterion. The significantly different branching ratios observed for these ions is attributed to the large change in orientation of the counterion with respect to the ammonium centers as the number of methylene groups in these ions increases. Similar ion conformational differences appear to explain the fragmentation for the OAc counter ion as well. PMID:16479265

Polarimetric Thermal Imaging

DTIC Science & Technology

2007-03-01

front of a large area blackbody as background. The viewing angle , defined as the angle between surface normal and camera line of sight, was varied by...and polarization angle were derived from the Stokes parameters. The dependence of these polarization characteristics on viewing angle was investigated

GIFTS SM EDU Data Processing and Algorithms

NASA Technical Reports Server (NTRS)

Tian, Jialin; Johnson, David G.; Reisse, Robert A.; Gazarik, Michael J.

2007-01-01

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) Sensor Module (SM) Engineering Demonstration Unit (EDU) is a high resolution spectral imager designed to measure infrared (IR) radiances using a Fourier transform spectrometer (FTS). The GIFTS instrument employs three Focal Plane Arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. This paper describes the processing algorithms involved in the calibration stage. The calibration procedures can be subdivided into three stages. In the pre-calibration stage, a phase correction algorithm is applied to the decimated and filtered complex interferogram. The resulting imaginary part of the spectrum contains only the noise component of the uncorrected spectrum. Additional random noise reduction can be accomplished by applying a spectral smoothing routine to the phase-corrected blackbody reference spectra. In the radiometric calibration stage, we first compute the spectral responsivity based on the previous results, from which, the calibrated ambient blackbody (ABB), hot blackbody (HBB), and scene spectra can be obtained. During the post-processing stage, we estimate the noise equivalent spectral radiance (NESR) from the calibrated ABB and HBB spectra. We then implement a correction scheme that compensates for the effect of fore-optics offsets. Finally, for off-axis pixels, the FPA off-axis effects correction is performed. To estimate the performance of the entire FPA, we developed an efficient method of generating pixel performance assessments. In addition, a random pixel selection scheme is designed based on the pixel performance evaluation.

1ES 1113+432: Luminous, soft X-ray outburst from a nearby cataclysmic variable (AR Ursae Majoris)

NASA Technical Reports Server (NTRS)

Remillard, R. A.; Schachter, J. F.; Silber, A. D.; Slane, P.

1994-01-01

A remarkable X-ray transient from the Einstein Slew Survey, 1 ES 1113+432, is identified with a nearby, short-period cataclysmic variable. Wenzel (1993) has confirmed that the optical counterpart is the variable star, AR UMa (cataloged as 'semiregular'), erroneously reported 5.7 min southeast of the true position. One of the Einstein slew observations recorded a flux of 43 IPC counts/s, which is an order of magnitude above the flux observed from the brightest cataclysmic variables in other X-ray surveys. The outburst spectrum is extremely 'soft,' with an implied blackbody temperature of approximately 22 eV. The optical counterpart (V = 16.5) exhibits a strong UV component, TiO bands from an M star, and broadened Balmer emission lines. Optical states as bright as V approx. 13 were found on photographs from the Harvard Plate Library, confirming outburst behavior in the optical counterpart. The historical photographic record suggests that 1ES 1113+432 remains in a low-accretion state most of the time. Both of the soft X-ray spectrum and the transitions between high and low-accretion states are suggestive of the AM Her (magnetic) subclass. Photometric observations in the I band show 0.18 mag modulations at a period of 0.966 hr. These are interpreted as ellipsiodal variations in the secondary star for a binary period of 1.932 hr, which is near the lower boundary of the 'period gap' in the histogram, of orbital periods of accreting white dwarfs. Thus 1ES 1113+432 provides the rare opportunity to study a secondary star in a cataclysmic binary that has evolved through the period gap. The optical spectral features from the secondary imply a spectral type of approximately M6 and a distance of approximately 88 pc. The peak luminosity in the soft X-ray component (unabsorbed) is then estimated to be 3 X 10(exp 33) ergs/s, assuming emission from a blackbody slab with a temperature of 22 eV. While this luminosity is higher than previous measures of the soft X-ray component, it does not exceed the amount of radiation that could be emitted from the accretion-heated surface of a white dwarf.

Activation of Peptide ions by blackbody radiation: factors that lead to dissociation kinetics in the rapid energy exchange limit.

PubMed

Price, W D; Williams, E R

1997-11-20

Unimolecular rate constants for blackbody infrared radiative dissociation (BIRD) were calculated for the model protonated peptide (AlaGly)(n) (n = 2-32) using a variety of dissociation parameters. Combinations of dissociation threshold energies ranging from 0.8 to 1.7 eV and transition entropies corresponding to Arrhenius preexponential factors ranging from very "tight" (A(infinity) = 10(9.9) s(-1)) to "loose" (A(infinity) = 10(16.8) s(-1)) were selected to represent dissociation parameters within the experimental temperature range (300-520 K) and kinetic window (k(uni) = 0.001-0.20 s(-1)) typically used in the BIRD experiment. Arrhenius parameters were determined from the temperature dependence of these values and compared to those in the rapid energy exchange (REX) limit. In this limit, the internal energy of a population of ions is given by a Boltzmann distribution, and kinetics are the same as those in the traditional high-pressure limit. For a dissociation process to be in this limit, the rate of photon exchange between an ion and the vacuum chamber walls must be significantly greater than the dissociation rate. Kinetics rapidly approach the REX limit either as the molecular size or threshold dissociation energy increases or as the transition-state entropy or experimental temperature decreases. Under typical experimental conditions, peptide ions larger than 1.6 kDa should be in the REX limit. Smaller ions may also be in the REX limit depending on the value of the threshold dissociation energy and transition-state entropy. Either modeling or information about the dissociation mechanism must be known in order to confirm REX limit kinetics for these smaller ions. Three principal factors that lead to the size dependence of REX limit kinetics are identified. With increasing molecular size, rates of radiative absorption and emission increase, internal energy distributions become relatively narrower, and the microcanonical dissociation rate constants increase more slowly over the energy distribution of ions. Guidelines established here should make BIRD an even more reliable method to obtain information about dissociation energetics and mechanisms for intermediate size molecules.

Improved Blackbody Simulator

DTIC Science & Technology

1974-06-01

28 - ABS Resins ................... 012 0.02 Carbon & Free-Cutting Steels%,. . . . . 27 - Acrylics ......................... 0.12 0.10 Alloy...Borosilicate Glasses................. 0.7 - Zinc At Its Alloys ................. 65.3 60.5 Alkyds .... .... .............. 010 0.20 Tungsten Carbide Cermet...cast).............47.6 25 ABS Resins ............ .. IS 3 FlowbnFie ........... 7 - Cellulose Acetate ............ &. 1.9 Pajadafi CW

Non-blackbody Disks Can Help Explain Inferred AGN Accretion Disk Sizes

NASA Astrophysics Data System (ADS)

Hall, Patrick B.; Sarrouh, Ghassan T.; Horne, Keith

2018-02-01

If the atmospheric density {ρ }atm} in the accretion disk of an active galactic nucleus (AGN) is sufficiently low, scattering in the atmosphere can produce a non-blackbody emergent spectrum. For a given bolometric luminosity, at ultraviolet and optical wavelengths such disks have lower fluxes and apparently larger sizes as compared to disks that emit as blackbodies. We show that models in which {ρ }atm} is a sufficiently low fixed fraction of the interior density ρ can match the AGN STORM observations of NGC 5548 but produce disk spectral energy distributions that peak at shorter wavelengths than observed in luminous AGN in general. Thus, scattering atmospheres can contribute to the explanation for large inferred AGN accretion disk sizes but are unlikely to be the only contributor. In the appendix section, we present unified equations for the interior ρ and T in gas pressure-dominated regions of a thin accretion disk.

Pulsed Thermal Emission from the Accreting Pulsar XMMU J054134.7-682550

NASA Astrophysics Data System (ADS)

Manousakis, Antonis; Walter, Roland; Audard, Marc; Lanz, Thierry

2009-05-01

XMMU J054134.7-682550, located in the LMC, featured a type II outburst in August 2007. We analyzed XMM-Newton (EPIC-MOS) and RXTE (PCA) data in order to derive the spectral and temporal characteristics of the system throughout the outburst. Spectral variability, spin period evolution, energy dependent pulse shape are discussed. The outburst (LX~3×1038 erg/s~LEDD) spectrum can be modeled using, cutoff power law, soft X-ray blackbody, disk emission, and cyclotron absorption line. The blackbody component shows a sinusoidal behavior, expected from hard X-ray reprocessing on the inner edge of the accretion disk. The thickness of the inner accretion disk (width of ~75 km) can be constrained. The spin-up of the pulsar during the outburst is the signature of a (huge) accretion rate. Simbol-X will provide similar capabilities as XMM-Newton and RXTE together, for such bright events.

Operational calibration of Geostationary Operational Environmental Satellite-8 and-9 imagers and sounders.

PubMed

Weinreb, M; Jamieson, M; Fulton, N; Chen, Y; Johnson, J X; Bremer, J; Smith, C; Baucom, J

1997-09-20

We describe the operational in-orbit calibration of the Geostationary Operational Environmental Satellite (GOES)-8 and-9 imagers and sounders. In the infrared channels the calibration is based on observations of space and an onboard blackbody. The calibration equation expresses radiance as a quadratic in instrument output. To suppress noise in the blackbody sequences, we filter the calibration slopes. The calibration equation also accounts for an unwanted variation of the reflectances of the instruments' scan mirrors with east-west scan position, which was not discovered until the instruments were in orbit. The visible channels are not calibrated, but the observations are provided relative to the level of space and are normalized to minimize east-west striping in the images. Users receive scaled radiances in a GOES variable format (GVAR) data stream. We describe the procedure users can apply to transform GVAR counts into radiances, temperatures, and mode-A counts.

On the dissociation and conformation of gas-phase methonium ions.

PubMed

Gross, Deborah S; Williams, Evan R

1996-12-20

The dissociation pathways of both doubly and singly charged methonium ions, (CH(3))(3)N(+) -(CH(2))(n)-(+)N(CH(3))(3)·X(-) (n = 6,10; X = Br, I, and OAc), are measured using blackbody infrared radiative dissociation (BIRD) and SORI-CAD in a Fourier transform mass spectrometer. SORI-CAD of the doubly charged decamethonium ions results primarily in the formation of even electron ions by hydrogen rearrangements. In contrast, homolytic bond cleavage to form two odd electron ions is highly favored in the hexamethonium ion, presumably due to increased Coulomb repulsion in this ion. For BIRD of the singly charged salts, ions are mass selected and dissociated by heating the vacuum chamber to elevated temperatures. Under the low pressure conditions of our experiment, energy is transferred from the chamber walls to the ions by the absorption of blackbody radiation. From the temperature dependence of the unimolecular rate constants for dissociation, Arrhenius activation energies in the zero-pressure limit are obtained. The primary dissociation pathways correspond to counterion substitution reactions which result in loss of N(CH(3))(3) and CH(3)X. For hexamethonium and decamethonium with X = Br or I, the branching ratios for these pathways differ dramatically; the ratio of loss of N(CH(3))(3) and CH(3)Br is 3.8 and 0.4 for hexamethonium and decamethonium bromide, respectively. The hexamethonium acetate salt has a branching ratio of 0.1. The Arrhenius activation energies for hexamethonium (Br or I) and decamethonium (Br or I) are 0.9 and 1.0 eV, respectively. This value for hexamethonium acetate is 0.6 eV. Molecular dynamics simulations and Monte Carlo conformation searching are used to obtain the lowest energy structures of hexamethonium and decamethonium bromide. These calculations indicate that the methonium ion folds around the counterion to form a cyclic salt-bridge structure in which both quaternary nitrogens interact with the oppositely charged counterion. The significantly different branching ratios observed for these ions is attributed to the large change in orientation of the counterion with respect to the ammonium centers as the number of methylene groups in these ions increases. Similar ion conformational differences appear to explain the fragmentation for the OAc counter ion as well.

Activation of Peptide Ions by Blackbody Radiation: Factors That Lead to Dissociation Kinetics in the Rapid Energy Exchange Limit

PubMed Central

Price, William D.

2005-01-01

Unimolecular rate constants for blackbody infrared radiative dissociation (BIRD) were calculated for the model protonated peptide (AlaGly)n (n = 2–32) using a variety of dissociation parameters. Combinations of dissociation threshold energies ranging from 0.8 to 1.7 eV and transition entropies corresponding to Arrhenius preexponential factors ranging from very “tight” (A∞ = 109.9 s−1) to “loose” (A∞ = 1016.8 s−1) were selected to represent dissociation parameters within the experimental temperature range (300–520 K) and kinetic window (kuni = 0.001–0.20 s−1) typically used in the BIRD experiment. Arrhenius parameters were determined from the temperature dependence of these values and compared to those in the rapid energy exchange (REX) limit. In this limit, the internal energy of a population of ions is given by a Boltzmann distribution, and kinetics are the same as those in the traditional high-pressure limit. For a dissociation process to be in this limit, the rate of photon exchange between an ion and the vacuum chamber walls must be significantly greater than the dissociation rate. Kinetics rapidly approach the REX limit either as the molecular size or threshold dissociation energy increases or as the transition-state entropy or experimental temperature decreases. Under typical experimental conditions, peptide ions larger than 1.6 kDa should be in the REX limit. Smaller ions may also be in the REX limit depending on the value of the threshold dissociation energy and transition-state entropy. Either modeling or information about the dissociation mechanism must be known in order to confirm REX limit kinetics for these smaller ions. Three principal factors that lead to the size dependence of REX limit kinetics are identified. With increasing molecular size, rates of radiative absorption and emission increase, internal energy distributions become relatively narrower, and the microcanonical dissociation rate constants increase more slowly over the energy distribution of ions. Guidelines established here should make BIRD an even more reliable method to obtain information about dissociation energetics and mechanisms for intermediate size molecules. PMID:16604162

MgB2 Thin-Film Bolometer for Applications in Far-Infrared Instruments on Future Planetary Missions

NASA Technical Reports Server (NTRS)

Lakew, B.; Aslam, S.; Brasunas, J.; Cao, N.; Costen, N.; La, A.; Stevenson, T.; Waczynski, A.

2012-01-01

A SiN membrane based MgB2 thin-film bolometer, with a non-optimized absorber, has been fabricated that shows an electrical noise equivalent power of 256 fW/square root Hz operating at 30 Hz in the 8.5 - 12.35 micron spectral bandpass. This value corresponds to an electrical specific detectivity of 7.6 x 10(exp 10) cm square root Hz/W. The bolometer shows a measured blackbody (optical) specific detectivity of 8.8 x 10(exp 9) cm square root Hz/W, with a responsivity of 701.5 kV/W and a first-order time constant of 5.2 ms. It is predicted that with the inclusion of a gold black absorber that a blackbody specific detectivity of 6.4 x 10(exp 10) cm/square root Hz/W at an operational frequency of 10 Hz, can be realized for integration into future planetary exploration instrumentation where high sensitivity is required in the 17 - 250 micron spectral wavelength range.

Atmospheric Compensation and Surface Temperature and Emissivity Retrieval with LWIR Hyperspectral Imagery

NASA Astrophysics Data System (ADS)

Pieper, Michael

Accurate estimation or retrieval of surface emissivity spectra from long-wave infrared (LWIR) or Thermal Infrared (TIR) hyperspectral imaging data acquired by airborne or space-borne sensors is necessary for many scientific and defense applications. The at-aperture radiance measured by the sensor is a function of the ground emissivity and temperature, modified by the atmosphere. Thus the emissivity retrieval process consists of two interwoven steps: atmospheric compensation (AC) to retrieve the ground radiance from the measured at-aperture radiance and temperature-emissivity separation (TES) to separate the temperature and emissivity from the ground radiance. In-scene AC (ISAC) algorithms use blackbody-like materials in the scene, which have a linear relationship between their ground radiances and at-aperture radiances determined by the atmospheric transmission and upwelling radiance. Using a clear reference channel to estimate the ground radiance, a linear fitting of the at-aperture radiance and estimated ground radiance is done to estimate the atmospheric parameters. TES algorithms for hyperspectral imaging data assume that the emissivity spectra for solids are smooth compared to the sharp features added by the atmosphere. The ground temperature and emissivity are found by finding the temperature that provides the smoothest emissivity estimate. In this thesis we develop models to investigate the sensitivity of AC and TES to the basic assumptions enabling their performance. ISAC assumes that there are perfect blackbody pixels in a scene and that there is a clear channel, which is never the case. The developed ISAC model explains how the quality of blackbody-like pixels affect the shape of atmospheric estimates and the clear channel assumption affects their magnitude. Emissivity spectra for solids usually have some roughness. The TES model identifies four sources of error: the smoothing error of the emissivity spectrum, the emissivity error from using the incorrect temperature, and the errors caused by sensor noise and wavelength calibration. The ways these errors interact determines the overall TES performance. Since the AC and TES processes are interwoven, any errors in AC are transferred to TES and the final temperature and emissivity estimates. Combining the two models, shape errors caused by the blackbody assumption are transferred to the emissivity estimates, where magnitude errors from the clear channel assumption are compensated by TES temperature induced emissivity errors. The ability for the temperature induced error to compensate for such atmospheric errors makes it difficult to determine the correct atmospheric parameters for a scene. With these models we are able to determine the expected quality of estimated emissivity spectra based on the quality of blackbody-like materials on the ground, the emissivity of the materials being searched for, and the properties of the sensor. The quality of material emissivity spectra is a key factor in determining detection performance for a material in a scene.

Technology Development for Cosmic Microwave Background Cosmology

NASA Astrophysics Data System (ADS)

Munson, Charles D.

The Cosmic Microwave Background (CMB) offers a unique window into the early universe by probing thermal radiation remaining from the big bang. Due to its low temperature and bright foregrounds, its thorough characterization requires technological advancement beyond the current state-of-the-art. In this thesis, I present the development and fabrication of novel metamaterial silicon optics to improve the sensitivity of current and future CMB telescopes. By machining subwavelength features into the silicon surfaces, traditional antireflection coatings can be replaced by all-silicon metamaterials that significantly reduce reflections over previous approaches. I discuss the design of these structured surfaces and the design and construction of a sophisticated fabrication facility necessary to implement this technology on large diameter (30+ cm) lenses for the Atacama Cosmology Telescope Polarization project (ACTPol). I then apply this metamaterial technology to the development of improved free-space filters for millimeter and sub-millimeter wavelength imaging (focusing specifically on blocking infrared radiation, necessary for current cryogenic detector systems). This produces a highly effective infrared-blocking filter, blocking over 99% of the incident power from a 300 K blackbody while maintaining transmission of better than 99% in a target CMB observing band (between 70 and 170 GHz). I conclude with a discussion of the development of a real-space simulation framework to assist in better understanding current CMB results and forecasting for future experiments. By taking a CMB realization and adding to it accurate real-space modeling of the Sunyaev-Zel'dovich effect and weak lensing distortions (introduced by galaxy clusters), a better understanding of the impacts of large scale structure on the CMB can be obtained.

Correlated Timing and Spectral Behavior of 4U 1705-44

NASA Astrophysics Data System (ADS)

Olive, Jean-François; Barret, Didier; Gierliński, Marek

2003-01-01

We follow the timing properties of the neutron star low-mass X-ray binary system 4U 1705-44 in different spectral states, as monitored by the Rossi X-Ray Timing Explorer over about a month. We fit the power density spectra using multiple Lorentzians. We show that the characteristic frequencies of these Lorentzians, when properly identified, fit within the correlations previously reported. The time evolution of these frequencies and their relation with the parameters of the energy spectra reported in Barret & Olive are used to constrain the accretion geometry changes. The spectral data were fitted by the sum of a blackbody and a Comptonized component and were interpreted in the framework of a truncated accretion disk geometry, with a varying truncation radius. If one assumes that the characteristic frequencies of the Lorentzians are some measure of this truncation radius, as in most theoretical models, then the timing data presented here strengthen the above interpretation. The soft-to-hard and hard-to-soft transitions are clearly associated with the disk receding from and approaching the neutron star, respectively. During the transitions, correlations are found between the Lorentzian frequencies and the flux and temperature of the blackbody, which is thus likely to be coming from the disk. On the other hand, in the hard state, the characteristic Lorentzians frequencies that are the lowest remained nearly constant despite significant evolution of the spectra parameters. The disk no longer contributes to the X-ray emission, and the blackbody is now likely to be emitted by the neutron star surface that is providing the seed photons for the Comptonization.

Analysis of the Herschel DEBRIS Sun-like star sample

NASA Astrophysics Data System (ADS)

Sibthorpe, B.; Kennedy, G. M.; Wyatt, M. C.; Lestrade, J.-F.; Greaves, J. S.; Matthews, B. C.; Duchêne, G.

2018-04-01

This paper presents a study of circumstellar debris around Sun-like stars using data from the Herschel DEBRIS Key Programme. DEBRIS is an unbiased survey comprising the nearest ˜90 stars of each spectral type A-M. Analysis of the 275 F-K stars shows that excess emission from a debris disc was detected around 47 stars, giving a detection rate of 17.1^{+2.6}_{-2.3} per cent, with lower rates for later spectral types. For each target a blackbody spectrum was fitted to the dust emission to determine its fractional luminosity and temperature. The derived underlying distribution of fractional luminosity versus blackbody radius in the population showed that most detected discs are concentrated at f ˜ 10-5 and at temperatures corresponding to blackbody radii 7-40 au, which scales to ˜40 au for realistic dust properties (similar to the current Kuiper belt). Two outlying populations are also evident; five stars have exceptionally bright emission ( f > 5 × 10-5), and one has unusually hot dust <4 au. The excess emission distributions at all wavelengths were fitted with a steady-state evolution model, showing that these are compatible with all stars being born with a narrow belt that then undergoes collisional grinding. However, the model cannot explain the hot dust systems - likely originating in transient events - and bright emission systems - arising potentially from atypically massive discs or recent stirring. The emission from the present-day Kuiper belt is predicted to be close to the median of the population, suggesting that half of stars have either depleted their Kuiper belts (similar to the Solar system) or had a lower planetesimal formation efficiency.

X-ray observations of black widow pulsars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gentile, P. A.; McLaughlin, M. A.; Roberts, M. S. E.

2014-03-10

We describe the first X-ray observations of five short orbital period (P{sub B} < 1 day), γ-ray emitting, binary millisecond pulsars (MSPs). Four of these—PSRs J0023+0923, J1124–3653, J1810+1744, and J2256–1024—are 'black-widow' pulsars, with degenerate companions of mass <<0.1 M {sub ☉}, three of which exhibit radio eclipses. The fifth source, PSR J2215+5135, is an eclipsing 'redback' with a near Roche-lobe filling ∼0.2 solar mass non-degenerate companion. Data were taken using the Chandra X-Ray Observatory and covered a full binary orbit for each pulsar. Two pulsars, PSRs J2215+5135 and J2256–1024, show significant orbital variability while PSR J1124–3653 shows marginal orbital variability.more » The lightcurves for these three pulsars have X-ray flux minima coinciding with the phases of the radio eclipses. This phenomenon is consistent with an intrabinary shock emission interpretation for the X-rays. The other two pulsars, PSRs J0023+0923 and J1810+1744, are fainter and do not demonstrate variability at a level we can detect in these data. All five spectra are fit with three separate models: a power-law model, a blackbody model, and a combined model with both power-law and blackbody components. The preferred spectral fits yield power-law indices that range from 1.3 to 3.2 and blackbody temperatures in the hundreds of eV. The spectrum for PSR J2215+5135 shows a significant hard X-ray component, with a large number of counts above 2 keV, which is additional evidence for the presence of intrabinary shock emission. This is similar to what has been detected in the low-mass X-ray binary to MSP transition object PSR J1023+0038.« less

Fuel Effective Photonic Propulsion

NASA Astrophysics Data System (ADS)

Rajalakshmi, N.; Srivarshini, S.

2017-09-01

With the entry of miniaturization in electronics and ultra-small light-weight materials, energy efficient propulsion techniques for space travel can soon be possible. We need to go for such high speeds so that the generation’s time long interstellar missions can be done in incredibly short time. Also renewable energy like sunlight, nuclear energy can be used for propulsion instead of fuel. These propulsion techniques are being worked on currently. The recently proposed photon propulsion concepts are reviewed, that utilize momentum of photons generated by sunlight or onboard photon generators, such as blackbody radiation or lasers, powered by nuclear or solar power. With the understanding of nuclear photonic propulsion, in this paper, a rough estimate of nuclear fuel required to achieve the escape velocity of Earth is done. An overview of the IKAROS space mission for interplanetary travel by JAXA, that was successful in demonstrating that photonic propulsion works and also generated additional solar power on board, is provided; which can be used as a case study. An extension of this idea for interstellar travel, termed as ‘Star Shot’, aims to send a nanocraft to an exoplanet in the nearest star system, which could be potentially habitable. A brief overview of the idea is presented.

Experimental Demonstration of Adaptive Infrared Multispectral Imaging using Plasmonic Filter Array.

PubMed

Jang, Woo-Yong; Ku, Zahyun; Jeon, Jiyeon; Kim, Jun Oh; Lee, Sang Jun; Park, James; Noyola, Michael J; Urbas, Augustine

2016-10-10

In our previous theoretical study, we performed target detection using a plasmonic sensor array incorporating the data-processing technique termed "algorithmic spectrometry". We achieved the reconstruction of a target spectrum by extracting intensity at multiple wavelengths with high resolution from the image data obtained from the plasmonic array. The ultimate goal is to develop a full-scale focal plane array with a plasmonic opto-coupler in order to move towards the next generation of versatile infrared cameras. To this end, and as an intermediate step, this paper reports the experimental demonstration of adaptive multispectral imagery using fabricated plasmonic spectral filter arrays and proposed target detection scenarios. Each plasmonic filter was designed using periodic circular holes perforated through a gold layer, and an enhanced target detection strategy was proposed to refine the original spectrometry concept for spatial and spectral computation of the data measured from the plasmonic array. Both the spectrum of blackbody radiation and a metal ring object at multiple wavelengths were successfully reconstructed using the weighted superposition of plasmonic output images as specified in the proposed detection strategy. In addition, plasmonic filter arrays were theoretically tested on a target at extremely high temperature as a challenging scenario for the detection scheme.

Cosmology and Dust from the COBE FIRAS

NASA Astrophysics Data System (ADS)

Mather, John C.

1995-12-01

I report the results of an analysis of improved data sets from the COBE FIRAS (Far Infrared Absolute Spectrophotometer) experiment. The new data sets have been analyzed to obtain improved limits, with smaller error bars, on the distortion of the cosmic microwave background radiation relative to a pure blackbody. These place strong constraints on exotic energy releases in the early universe. Also, an extension of the Principal Component analysis has provided new information on Galactic dust and limits on a far infrared cosmic background (FIRB) in the 0.1 - 0.5 mm range. Although the FIRAS data are consistent with a FIRB that is a significant fraction of the Galactic brightness at the poles, they can also be explained in terms of spatial variations of the properties of the interstellar medium. I acknowledge the FIRAS team, and especially D. J. Fixsen and R. A. Shafer, for the improved data sets and significant contributions to the analyses reported here. The National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC) is responsible for the design, development, and operation of the Cosmic Background Explorer (COBE), under the scientific guidance of the COBE Science Working Group. GSFC is also responsible for the software development and the final processing of the mission data.

Study of a new central compact object: The neutron star in the supernova remnant G15.9+0.2

NASA Astrophysics Data System (ADS)

Klochkov, D.; Suleimanov, V.; Sasaki, M.; Santangelo, A.

2016-08-01

We present our study of the central point source CXOU J181852.0-150213 in the young Galactic supernova remnant (SNR) G15.9+0.2 based on the recent ~90 ks Chandra observations. The point source was discovered in 2005 in shorter Chandra observations and was hypothesized to be a neutron star associated with the SNR. Our X-ray spectral analysis strongly supports the hypothesis of a thermally emitting neutron star associated with G15.9+0.2. We conclude that the object belongs to the class of young cooling low-magnetized neutron stars referred to as central compact objects (CCOs). We modeled the spectrum of the neutron star with a blackbody spectral function and with our hydrogen and carbon neutron star atmosphere models, assuming that the radiation is uniformly emitted by the entire stellar surface. Under this assumption, only the carbon atmosphere models yield a distance that is compatible with a source located in the Galaxy. In this respect, CXOU J181852.0-150213 is similar to two other well-studied CCOs, the neutron stars in Cas A and in HESS J1731-347, for which carbon atmosphere models were used to reconcile their emission with the known or estimated distances.

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

NASA Astrophysics Data System (ADS)

Klärs, Jan; Schmitt, Julian; Vewinger, Frank; Weitz, Martin

2011-01-01

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.

An Unusual Stellar Death on Christmas Day

NASA Technical Reports Server (NTRS)

Thone, C. C.; de Ugarte Postigo, A.; Fryer, C. L.; Page, K. L.; Gorosabel, J.; Aloy, M. A.; Perley, D. A.; Kouveliotou, C.; Janka, H. T.; Mimica, P.;

An interpretation of X-ray spectra of type II bursts from the 'rapid burster' - Comptonization due to accretion flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirotani, Kouichi; Hanawa, Tomoyuki; Kawai, Nobuyuki

1990-06-01

A new model is proposed for the spectrum of a type II burst from the 'rapid burster'. The spectrum of a type II burst has been considered to be well fitted with a blackbody spectrum with temperature T about 1.5 keV. Recent observations with Tenma and Exosat, however, have found an excess from the blackbody spectrum in the high-energy range (E greater than 10 keV). The high-energy component is approximated to be a power-law spectrum of f(E) proportional to E exp -4, where E and f(E) are the X-ray energy and observed counts per unit energy, respectively. The model explainsmore » this high-energy component gives a method to evaluate the velocity and the optical depth of the accretion flow from observations of the high-energy component. It is shown that the spectrum observed with Tenma can be fitted with the model. 33 refs.« less

Photoionization models for the wind from TW Vir

NASA Technical Reports Server (NTRS)

Kallman, T.

1985-01-01

Line profiles are examined for the resonance doublets of the ions C IV, Si IV, and N V in the spectrum of the dwarf nova TW Virginis as observed by Cordova and Mason (1982). Line strengths depend on the abundances of the scattering ions and hence on the physical characteristics in the stellar wind. Results of the study show that the observed UV line ratios from TW Vir cannot be produced by photoionization by either an unattenuated single bremsstrahlung or by a single blackbody spectrum. Satisfactory values of the abundance ratios can be produced by bremsstrahlung spectra extending into the X-ray region which have low-energy cutoffs near the N IV threshold energy at 77 eV and have fluxes corresponding to an ionization parameter xi-sub-br of about 10. A finding that the flux in the soft X-ray bremsstrahlung component must exceed the EUV blackbody flux by at least an order of magnitude has implications for theories of the continuum emission from cataclysmic variables.

On-Orbit Operation and Performance of MODIS Blackbody

NASA Technical Reports Server (NTRS)

Xiong, X.; Chang, T.; Barnes, W.

2009-01-01

MODIS collects data in 36 spectral bands, including 20 reflective solar bands (RSB) and 16 thermal emissive bands (TES). The TEB on-orbit calibration is performed on a scan-by-scan basis using a quadratic algorithm that relates the detector response with the calibration radiance from the sensor on-board blackbody (BB). The calibration radiance is accurately determined each scan from the BB temperature measured using a set of 12 thermistors. The BB thermistors were calibrated pre-launch with traceability to the NIST temperature standard. Unlike many heritage sensors, the MODIS BB can be operated at a constant temperature or with the temperature continuously varying between instrument ambient (about 270K) and 315K. In this paper, we provide an overview of both Terra and Aqua MODIS on-board BB operations, functions, and on-orbit performance. We also examine the impact of key calibration parameters, such as BB emissivity and temperature (stability and gradient) determined from its thermistors, on the TEB calibration and Level I (LIB) data product uncertainty.

Rapid onset of decoherence in driven-dissipative Rydberg systems

NASA Astrophysics Data System (ADS)

Magnan, Eric; Boulier, Thomas; Bracamontes, Carlos; Maslek, James; Young, Jeremy; Gorshkov, Alexei; Porto, Trey; Rolston, Steven; JQI-Rubidium One Team

2017-04-01

Rydberg atoms have been strong candidates for the realization of quantum information processing and quantum simulation. Recently, however, there has been concerns about this approach due to the observation of a rapid onset of decoherence in large ensembles. In we provide experimental support for the hypothesis that this is due to the avalanche-like onset of exchange dipole interactions, fueled by blackbody transitions to nearby Rydberg states of opposite parity. Making a fully microscopic model has proven difficult as it requires beyond mean-field arguments, but the ubiquitousness of Rydberg-Rydberg blackbody transitions at room temperature and the always-resonant nature of dipole exchange interactions make it an interesting challenge, and argues for deeper study into the matter. In this poster, we present complementary measurements and analysis that confirm this mechanism. We also discuss several possibilities to reduce its impact on the system's coherence. This work was partially supported by NSF PIF, AFOSR, ARO, ARL-CDQI, and NSF PFC at JQI.

Hot Carrier-Based Near-Field Thermophotovoltaic Energy Conversion.

PubMed

St-Gelais, Raphael; Bhatt, Gaurang Ravindra; Zhu, Linxiao; Fan, Shanhui; Lipson, Michal

2017-03-28

Near-field thermophotovoltaics (NFTPV) is a promising approach for direct conversion of heat to electrical power. This technology relies on the drastic enhancement of radiative heat transfer (compared to conventional blackbody radiation) that occurs when objects at different temperatures are brought to deep subwavelength distances (typically <100 nm) from each other. Achieving such radiative heat transfer between a hot object and a photovoltaic (PV) cell could allow direct conversion of heat to electricity with a greater efficiency than using current solid-state technologies (e.g., thermoelectric generators). One of the main challenges in the development of this technology, however, is its incompatibility with conventional silicon PV cells. Thermal radiation is weak at frequencies larger than the ∼1.1 eV bandgap of silicon, such that PV cells with lower excitation energies (typically 0.4-0.6 eV) are required for NFTPV. Using low bandgap III-V semiconductors to circumvent this limitation, as proposed in most theoretical works, is challenging and therefore has never been achieved experimentally. In this work, we show that hot carrier PV cells based on Schottky junctions between silicon and metallic films could provide an attractive solution for achieving high efficiency NFTPV electricity generation. Hot carrier science is currently an important field of research and several approaches are investigated for increasing the quantum efficiency (QE) of hot carrier generation beyond conventional Fowler model predictions. If the Fowler limit can indeed be overcome, we show that hot carrier-based NFTPV systems-after optimization of their thermal radiation spectrum-could allow electricity generation with up to 10-30% conversion efficiencies and 10-500 W/cm 2 generated power densities (at 900-1500 K temperatures). We also discuss how the unique properties of thermal radiation in the extreme near-field are especially well suited for investigating recently proposed approaches for high QE hot carrier junctions. We therefore expect our work to be of interest for the field of hot carrier science and-by relying solely on conventional thin film materials-to provide a path for the experimental demonstration of NFTPV energy conversion.

A reconsideration of the noise equivalent power and the data analysis procedure for the infrared imaging video bolometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pandya, Shwetang N., E-mail: pandya.shwetang@LHD.nifs.ac.jp; Sano, Ryuichi; Peterson, Byron J.

The infrared imaging video bolometer (IRVB) used for measurement of the two-dimensional (2D) radiation profiles from the Large Helical Device has been significantly upgraded recently to improve its signal to noise ratio, sensitivity, and calibration, which ultimately provides quantitative measurements of the radiation from the plasma. The reliability of the quantified data needs to be established by various checks. The noise estimates also need to be revised and more realistic values need to be established. It is shown that the 2D heat diffusion equation can be used for estimating the power falling on the IRVB foil, even with a significantmore » amount of spatial variation in the thermal diffusivity across the area of the platinum foil found experimentally during foil calibration. The equation for the noise equivalent power density (NEPD) is re-derived to include the errors in the measurement of the thermophysical and the optical properties of the IRVB foil. The theoretical value estimated using this newly derived equation matches closely, within 5.5%, with the mean experimental value. The change in the contribution of each error term of the NEPD equation with rising foil temperature is also studied and the blackbody term is found to dominate the other terms at elevated operating temperatures. The IRVB foil is also sensitive to the charge exchange (CX) neutrals escaping from the plasma. The CX neutral contribution is estimated to be marginally higher than the noise equivalent power (NEP) of the IRVB. It is also established that the radiation measured by the IRVB originates from the impurity line radiation from the plasma and not from the heated divertor tiles. The change in the power density due to noise reduction measures such as data smoothing and averaging is found to be comparable to the IRVB NEPD. The precautions that need to be considered during background subtraction are also discussed with experimental illustrations. Finally, the analysis algorithm with all the improvements is validated and found to reproduce the input power well within 10% accuracy. This article answers many fundamental questions relevant to the IRVB and illustrates the care to be exercised while processing the IRVB data.« less

Emission of Gas and Al2O3 Smoke in Gas-Al Particle Deflagration: Experiments and Emission Modeling for Explosive Fireballs

NASA Astrophysics Data System (ADS)

Ranc-Darbord, Isabelle; Baudin, Gérard; Genetier, Marc; Ramel, David; Vasseur, Pierre; Legrand, Julien; Pina, Vincent

2018-03-01

Emission of gas and Al2O3 smoke within the deflagration of H2{-}O2-{N2{-}CO2}-Al particles has been studied in a closed combustion chamber at pressures of up to 18 bar and at gas temperatures of up to 3700 K. Measurements of radiance intensity were taken using a five wavelength pyrometer (0.660 μ m, 0.850 μ m, 1.083 μ m, 1.260 μ m, 1.481 μ m) and a grating spectrometer in the range (4.10 μ m to 4.30 μ m). In order to characterize the aluminum oxide smoke size and temperature, an inversion method has been developed based on the radiation transfer equation and using pyrometer measurements and thermochemical calculations of Al2O3 smoke volume fractions. Temperatures in combustion gas have been determined using a method based on the assumed blackbody head of the 4.26 μ m CO2 emission line and on its spectral shift with pressure and temperature. For validation purpose, this method has been applied to measurements obtained when calibrated alumina particles are injected in a combustion chamber prior to gaseous deflagrations. This mathematical inversion method was developed to investigate explosive fireballs.

George Smoot, Blackbody, and Anisotropy of the Cosmic Microwave Background

Science.gov Websites

, ... has been awarded the 2006 Nobel Prize for physics. He shares the award with John C. Mather of NASA we continue to support him today. In addition, one of the principal instruments for the NASA COBE

Suzaku Observation of the Classical Nova V2491 Cyg in Quiescence

NASA Technical Reports Server (NTRS)

Zemko, P.; Mukai, K.; Orio, M.

2015-01-01

We present Suzaku XIS observation of V2491 Cyg (Nova Cyg 2008 No. 2) obtained in quiescence, more than two years after the outburst. The nova was detected as a very luminous source in a wide spectral range from soft to hard X-rays. A very soft blackbody-like component peaking at 0.5 keV indicates that either we observe remaining, localized hydrogen burning on the surface of the white dwarf, or accretion onto a magnetized polar cap. In the second case, V2491 Cyg is a candidate "soft intermediate polar". We obtained the best fit for the X-ray spectra with several components: two of thermal plasma, a blackbody and a complex absorber. The later is typical of intermediate polars. The X-ray light-curve shows a modulation with an approximately 38 min period. The amplitude of this modulation is strongly energy dependent and reaches maximum in the 0.8-2.0 keV range. We discuss the origin of the X-ray emission and pulsations, and the likelihood of the intermediate polar scenario.

Laboratory simulation of photoionized plasma among astronomical compact objects

NASA Astrophysics Data System (ADS)

Fujioka, Shinsuke; Yamamoto, Norimasa; Wang, Feilu; Salzmann, David; Li, Yutong; Rhee, Yong-Joo; Nishimura, Hiroaki; Takabe, Hideaki; Mima, Kunioki

2008-11-01

X-ray line emission with several-keV of photon energy was observed from photoionized accreting clouds, for example CYGNUS X-3 and VELA X-1, those are exposed by hard x-ray continuum from the compact objects, such as neutron stars, black holes, or white dwarfs, although accreting clouds are thermally cold. The x-ray continuum-induced line emission gives a good insight to the accreting clouds. We will present a novel laboratory simulation of the photoionized plasma under well-characterized conditions by using high-power laser facility. Blackbody radiator with 500-eV of temperature, as a miniature of a hot compact object, was created.Silicon (Si) plasma with 30-eV of electron temperature was produced in the vicinity of the 0.5-keV blackbody radiator. Line emissions of lithium- and helium-like Si ions was clearly observed around 2-keV of photon-energy from the thermally cold Si plasma, this result is hardly interpreted without consideration of the photoionization. Atomic kinetics code reveals importance of inner-shell ionization directly caused by incoming hard x-rays.

Technology Development for Cosmic Microwave Background Cosmology

NASA Astrophysics Data System (ADS)

Munson, Charles D.

2017-05-01

The Cosmic Microwave Background (CMB) offers a unique window into the early universe by probing thermal radiation remaining from the big bang. Due to its low temperature and bright foregrounds, its thorough characterization requires technological advancement beyond the current state-of-the-art. In this thesis, I present the development and fabrication of novel metamaterial silicon optics to improve the sensitivity of current and future CMB telescopes. By machining subwavelength features into the silicon surfaces, traditional antireflection coatings can be replaced by all-silicon metamaterials that significantly reduce reflections over previous approaches. I discuss the design of these structured surfaces and the design and construction of a sophisticated fabrication facility necessary to implement this technology on large diameter (30+ cm) lenses for the Atacama Cosmology Telescope Polarization project (ACTPol). I then apply this metamaterial technology to the development of improved free-space filters for millimeter and sub-millimeter wavelength imaging (focusing specifically on blocking infrared radiation, necessary for current cryogenic detector systems). This produces a highly effective infrared-blocking filter, blocking over 99% of the incident power from a 300 K blackbody while maintaining transmission of better than 99% in a target CMB observing band (between 70 and 170 GHz). I conclude with a discussion of the development of a real-space simulation framework to assist in better understanding current CMB results and forecasting for future experiments. By taking a CMB realization and adding to it accurate real-space modeling of the Sunyaev-Zel'dovich effect and weak lensing distortions (introduced by galaxy clusters), a better understanding of the impacts of large scale structure on the CMB can be obtained.

Radiation attenuation and opacity in smoke and water sprays

NASA Astrophysics Data System (ADS)

Parent, Gilles; Boulet, Pascal; Morlon, Romain; Blanchard, Elizabeth

2017-08-01

Radiation attenuation through sprays, smoke and mixings of both media was studied in the infrared and in the visible range, by conducting real scale experiments in a corridor. The effect of water injection by a water mist nozzle and a sprinkler device was investigated. Radiation attenuation in the infrared range and opacity in the visible range were measured, by using a FTIR spectrometer and a dedicated opacimetry device especially designed for the present application. Experiments were done using either a blackbody source for attenuation characterization, or a heptane pool fire aimed at producing smoke for opacity measurements. For tests with smoke, the difficulties raised by the harsh environment involving a hot mixing of gas plus soot and vapor carrying water droplets were circumvented with an original device involving an optical fiber network. Mean infrared transmission was found equal to 12% for the water mist (with a 25 L/min water flowrate) and 37% for the sprinkler (with a 91 L/min water flowrate). Fitting the infrared transmission spectra with results obtained using a Monte Carlo simulation provided an estimation of the water volumetric fraction in the spray. It was shown that the better attenuation capability of the water mist is due to two factors: (1) a higher extinction coefficient of the water mist for a given water volumetric fraction due to the small size of the injected droplets and (2) a higher water volumetric fraction. Opacity measurements in the visible range yielded a measured extinction coefficient in good agreement with an estimation obtained with the Mie theory and the identified water volumetric fraction. Moreover, the water sprays (sprinkler or water mist) was seen to lead to a quick de-stratification of the smoke layer. When the spraying operation was stopped, the visibility re-increased in two main steps: a first step of fast increase and a second step of slow increase needing a few tens of seconds to get again a fully stratified smoke layer.

THE WISE DETECTION OF AN INFRARED ECHO IN TIDAL DISRUPTION EVENT ASASSN-14li

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Ning; Dou, Liming; Wang, Tinggui

We report the detection of a significant infrared variability of the nearest tidal disruption event (TDE) ASASSN-14li using Wide-field Infrared Survey Explorer and newly released Near-Earth Object WISE Reactivation data. In comparison with the quiescent state, the infrared flux is brightened by 0.12 and 0.16 mag in the W1 (3.4 μ m) and W2 (4.6 μ m) bands at 36 days after the optical discovery (or ∼110 days after the peak disruption date). The flux excess is still detectable ∼170 days later. Assuming that the flare-like infrared emission is from the dust around the black hole, its blackbody temperature ismore » estimated to be ∼2.1 × 10{sup 3} K, slightly higher than the dust sublimation temperature, indicating that the dust is likely located close to the dust sublimation radius. The equilibrium between the heating and radiation of the dust claims a bolometric luminosity of ∼10{sup 43}–10{sup 45} erg s{sup −1}, comparable with the observed peak luminosity. This result has for the first time confirmed the detection of infrared emission from the dust echoes of TDEs.« less

Depopulation of metastable helium by radiative association with hydrogen and lithium ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Augustovičová, L.; Soldán, P.; Kraemer, W. P., E-mail: pavel.soldan@mff.cuni.cz

2014-02-10

Depopulation of metastable He(2{sup 3}S) by radiative association with hydrogen and lithium ions is investigated using a fully quantal approach. Rate coefficients for spontaneous and stimulated radiative association of the HeH{sup +}, HeD{sup +}, and LiHe{sup +} molecular ions on the spin-triplet manifold are presented as functions of temperature considering the association to rotational-vibrational states of the lowest triplet electronic states a {sup 3}Σ{sup +} and b {sup 3}Σ{sup +} from the continuum states of the b {sup 3}Σ{sup +} electronic state. Evaluation of the rate coefficients is based on highly accurate quantum calculations, taking into account all possible state-to-statemore » transitions at thermal energies (for spontaneous association) or at higher background energies (stimulated association). As expected, calculations show that the rate coefficients for radiative association to the a state are several orders of magnitude larger than the one for the b state formation. A noticeable effect by blackbody background radiation on the radiative association is only obtained for the b → b process. Aspects of the formation and abundance of the metastable HeH{sup +}(a {sup 3}Σ{sup +}) in astrophysical environments are briefly discussed.« less

Growth dynamics of carbon-metal particles and nanotubes synthesized by CO2 laser vaporization

NASA Astrophysics Data System (ADS)

Kokai, F.; Takahashi, K.; Yudasaka, M.; Iijima, S.

To study the growth of carbon-Co/Ni particles and single-wall carbon nanotubes (SWNTs) by 20 ms CO2 laser-pulse irradiation of a graphite-Co/Ni (1.2 at.%) target in an Ar gas atmosphere (600 Torr), we used emission imaging spectroscopy and shadowgraphy with a temporal resolution of 1.67 ms. Wavelength-selected emission images showed that C2 emission was strong in the region close to the target (within 2 cm), while for the same region the blackbody radiation from the large clusters or particles increased with increasing distance from the target. Shadowgraph images showed that the viscous flow of carbon and metal species formed a mushroom or a turbulent cloud spreading slowly into the Ar atmosphere, indicating that particles and SWNTs continued to grow as the ejected material cooled. In addition, emission imaging spectroscopy at 1200 °C showed that C2 and hot clusters and particles with higher emission intensities were distributed over much wider areas. We discuss the growth dynamics of the particles and SWNTs through the interaction of the ambient Ar with the carbon and metal species released from the target by the laser pulse.

Squeezed states and graviton-entropy production in the early universe

NASA Technical Reports Server (NTRS)

Giovannini, Massimo

1994-01-01

Squeezed states are a very useful framework for the quantum treatment of tensor perturbations (i.e. gravitons production) in the early universe. In particular, the non equilibrium entropy growth in a cosmological process of pair production is completely determined by the associated squeezing parameter and is insensitive to the number of particles in the initial state. The total produced entropy may represent a significant fraction of the entropy stored today in the cosmic blackbody radiation, provided pair production originates from a change in the background metric at a curvature scale of the Planck order. Within the formalism of squeezed thermal states it is also possible to discuss the stimulated emission of gravitons from an initial thermal bath, under the action of the cosmic gravitational background field. We find that at low energy the graviton production is enhanced, if compared with spontaneous creation from the vacuum; as a consequence, the inflation scale must be lowered, in order not to exceed the observed CMB quadrupole anisotropy. This effect is important, in particular, for models based on a symmetry-breaking transition which require, as initial condition, a state of thermal equilibrium at temperatures higher than the inflation scale and in which inflation has a minimal duration.

Effect of Index of Refraction on Radiation Characteristics in a Heated Absorbing, Emitting, and Scattering Layer

NASA Technical Reports Server (NTRS)

Siegel, R.; Spuckler, C. M.

1992-01-01

The index of refraction can considerably influence the temperature distribution and radiative heat flow in semitransparent materials such as some ceramics. For external radiant heating, the refractive index influences the amount of energy transmitted into the interior of the material. Emission within a material depends on the square of its refractive index, and hence this emission can be many times that for a biackbody radiating into a vacuum. Since radiation exiting through an interface into a vacuum cannot exceed that of a blackbody, there is extensive reflection at the internal surface of an interface, mostly by total internal reflection. This redistributes energy within the layer and tends to make its temperature distribution more uniform. The purpose of the present analysis is to show that, for radiative equilibrium in a gray layer with diffuse interfaces, the temperature distribution and radiative heat flux for any index of refraction can be obtained very simply from the results for an index of refraction of unity. For the situation studied here, the layer is subjected to external radiative heating incident on each of its surfaces. The material emits, absorbs, and isotropically scatters radiation. For simplicity the index of refraction is unity in the medium surrounding the layer. The surfaces of the layer are assumed diffuse. This is probably a reasonable approximation for a ceramic layer that has not been polished. When transmitted radiation or radiation emitted from the interior reaches the inner surface of an interface, the radiation is diffused and some of it thereby placed into angular directions for which there is total internal reflection. This provides a trapping effect for retaining energy within the layer and tends to equalize its temperature distribution. An analysis of temperature distributions in absorbing-emitting layers, including index of refraction effects, was developed by Gardon (1958) to predict cooling and heat treating of glass plates. The interfaces were optically smooth; the resulting specular reflections were computed from the Fresnel reflection laws. This provides a somewhat different behavior than for diffuse interfaces. A similar application was for heating that occurs in a window of a re-entry vehicle (Fowle et al., 1969). A number of recent papers (Rokhsaz and Dougherty, 1989; Ping and Lallemand, 1989; Crosbie and Shieh, 1990) further examined the effects of Fresnel boundary reflections and nonunity refractive index. Other examples of analyses of both steady and transient heat transfer to single or multiple plane layers (Amlin and Korpela, 1979; Tarshis et al., 1969) have used diffuse assumptions at the interfaces as in the present study

X-ray astronomy in the laboratory with a miniature compact object produced by laser-driven implosion

NASA Astrophysics Data System (ADS)

Fujioka, Shinsuke; Takabe, Hideaki; Yamamoto, Norimasa; Salzmann, David; Wang, Feilu; Nishimura, Hiroaki; Li, Yutong; Dong, Quanli; Wang, Shoujun; Zhang, Yi; Rhee, Yong-Joo; Lee, Yong-Woo; Han, Jae-Min; Tanabe, Minoru; Fujiwara, Takashi; Nakabayashi, Yuto; Zhao, Gang; Zhang, Jie; Mima, Kunioki

2009-11-01

X-ray spectroscopy is an important tool for understanding the extreme photoionization processes that drive the behaviour of non-thermal equilibrium plasmas in compact astrophysical objects such as black holes. Even so, the distance of these objects from the Earth and the inability to control or accurately ascertain the conditions that govern their behaviour makes it difficult to interpret the origin of the features in astronomical X-ray measurements. Here, we describe an experiment that uses the implosion driven by a 3TW, 4kJ laser system to produce a 0.5keV blackbody radiator that mimics the conditions that exist in the neighbourhood of a black hole. The X-ray spectra emitted from photoionized silicon plasmas resemble those observed from the binary stars Cygnus X-3 (refs 7, 8) and Vela X-1 (refs 9, 10 11) with the Chandra X-ray satellite. As well as demonstrating the ability to create extreme radiation fields in a laboratory plasma, our theoretical interpretation of these laboratory spectra contrasts starkly with the generally accepted explanation for the origin of similar features in astronomical observations. Our experimental approach offers a powerful means to test and validate the computer codes used in X-ray astronomy.

Cosmic Microwave Background Timeline

Science.gov Websites

about 2.3 K 1948: George Gamow, Ralph Alpher, and Robert Herman predict that a Big Bang universe perfect blackbody spectrum and thereby strongly supporting the hot big bang model, the thermal history of anisotropy in the cosmic microwave background, this strongly supports the big bang model with gravitational

NuSTAR and Swift joint view of neutron star X-ray binary 4U 1728-34: disc reflection in the island and lower banana states

NASA Astrophysics Data System (ADS)

Mondal, Aditya S.; Pahari, Mayukh; Dewangan, G. C.; Misra, R.; Raychaudhuri, B.

2017-04-01

We analyse two simultaneous NuSTAR and Swift data of the Atoll-type neutron star (NS) X-ray binary 4U 1728-34 observed on 2013 October 1 and 3. We infer that the first and the second observations belong to the island state and the lower banana state, respectively. During island state, four type-I X-ray bursts are observed within 60 ks exposure. From the time-resolved spectral analysis of each burst with NuSTAR, the blackbody temperature kTbb are found to vary between 1.3 and 3.0 keV, while the blackbody normalizations (km/10 kpc)2 vary in the range 20-200, which translates to blackbody radii of 3.5-7.4 km for an assumed distance of 5 kpc. The persistent, joint energy spectra from Swift and NuSTAR for both observations in the energy band 1-79 keV are well described with thermal emission from the NS surface (kTbb ≃ 1-2.5 keV), Comptonized emission of thermal seed photons from the hot boundary layer/corona and the strong reflection component from the accretion disc. We detect a broad iron line in the 5-8 keV band and reflection hump in the 15-30 keV band modelled by the relxill reflection model. Joint spectral fitting constrains the inclination angle of the binary system and inner disc radius to be 22°-40° and (2.0-4.3) × RISCO, respectively. We estimate the magnetic field to be (1.8-6.5) × 108 G. The X-ray luminosity of the source during the island and lower banana states are found to be LX = 1.1 and 1.6 × 1037 erg s-1, respectively, which correspond to ˜6 per cent and ˜9 per cent of the Eddington luminosity.

The Preflight Calibration of the Thermal Infrared Sensor (TIRS) on the Landsat Data Continuity Mission

NASA Technical Reports Server (NTRS)

Smith, Ramsey; Reuter, Dennis; Irons, James; Lunsford, Allen; Montanero, Matthew; Tesfaye, Zelalem; Wenny, Brian; Thome, Kurtis

2011-01-01

The preflight calibration testing of TIRS evaluates the performance of the instrument at the component, subsystem and system level, The overall objective is to provide an instrument that is well calibrated and well characterized with specification compliant data that will ensure the data continuity of Landsat from the previous missions to the LDCM, The TIRS flight build unit and the flight instrument were assessed through a series of calibration tests at NASA Goddard Space Flight Center. Instrument-level requirements played a strong role in defining the test equipment and procedures used for the calibration in the thermal/vacuum chamber. The calibration ground support equipment (CGSE), manufactured by MEI and ATK Corporation, was used to measure the optical, radiometric and geometric characteristics of TIRS, The CGSE operates in three test configurations: GeoRad (geometric, radiometric and spatial), flood source and spectral, TIRS was evaluated though the following tests: bright target recovery, radiometry, spectral response, spatial shape, scatter, stray light, focus, and uniformity, Data were obtained for the instrument and various subsystems under conditions simulating those on orbit In the spectral configuration, a monochromator system with a blackbody source is used for in-band and out-of-band relative spectral response characterization, In the flood source configuration the entire focal plane array is illuminated simultaneously to investigate pixel-to-pixel uniformity and dead or inoperable pixels, The remaining tests were executed in the GeoRad configuration and use a NIST calibrated cavity blackbody source, The NIST calibration is transferred to the TIRS sensor and to the blackbody source on-board TIRS, The onboard calibrator will be the primary calibration source for the TIRS sensor on orbit.

Characterization of near-terahertz complementary metal-oxide semiconductor circuits using a Fourier-transform interferometer

DOE PAGES

Arenas, D. J.; Shim, Dongha; Koukis, D. I.; ...

2011-10-24

Optical methods for measuring of the emission spectra of oscillator circuits operating in the 400-600 GHz range are described. The emitted power from patch antennas included in the circuits is measured by placing the circuit in the source chamber of a Fourier-transform interferometric spectrometer. The results show that this optical technique is useful for measuring circuits pushing the frontier in operating frequency. The technique also allows the characterization of the circuit by measuring the power radiated in the fundamental and in the harmonics. This capability is useful for oscillator architectures designed to cancel the fundamental and use higher harmonics. Themore » radiated power was measured using two techniques: direct measurement of the power by placing the device in front of a bolometer of known responsivity, and by comparison to the estimated power from blackbody sources. The latter technique showed that these circuits have higher emission than blackbody sources at the operating frequencies, and, therefore, offer potential spectroscopy applications.« less

EPIC Study of Two Enigmatic Sources: The Mouse and SNR 359.1-0.5

NASA Technical Reports Server (NTRS)

Pavlov, George

2004-01-01

The objective of the original proposal was to observe the Mouse pulsar wind nebula (associated with PSR J1744-2958) and the nearby supernova remnant G359.1-0.5, where the pulsar was probably born, with the XMM-Newton observatory to study the properties of these objects. SNR G359.1-0.5 was accepted as a Category C target and has not been observed. The Mouse was observed on April 27,2003 for 52 ks. The image analysis has shown that the Mouse is extended in the East-West direction, possibly along the direction of the pulsar's proper motion. The spectrum of this pulsar wind nebula can be described as an absorbed power law with the photon index GAMMA = 1.9 plus or minus 0.1, effective hydrogen column density n(sub H) = (2.6 plus or minus 0.1) x 10(exp 22) per square centimeter, and flux F = 1.8 x 10(exp -11) erg per square centimeter per second in the 1-10 keV energy range. Based on the n(sub H) value, the distance to the source is about 5 kpc, which results in the luminosity 3.7 x 10(exp 34) erg per second. We conclude that PSR J1744-2958 and the Mouse are not physically associated with G359.1-0.5, which lies at a larger distance. In addition to the Mouse, we also detected two Low-Mass X-ray Binaries, SLX 1744-299 and 1744-300, in the EPIC MOS and PN fields of view. The latter of these objects showed a Type I X-ray burst during our observation, with a rise time of 5 s and decay time of 60 s. A very strong pileup during the burst made the analysis of the burst properties unreliable. The spectral analysis of the persistent radiation from SLX 1744-299 and 1744-300 yields the hydrogen column densities of 3.2 plus or minus 0.1 and (3.6 plus or minus 0.2) x 10(exp 22) per square centimeter, respectively, which suggests that the sources are close to the Galactic center (d = 8-9 kpc). The spectra can be reasonably well fitted with a blackbody plus thin disk model, with the blackbody temperatures of 1.7 plus or minus 0.2 and 1.8 plus or minus 0.2 keV, respectively.

EOS/AMSU: A Blackbody Spacecraft Test Targets Operation and Maintenance Manual

NASA Technical Reports Server (NTRS)

1998-01-01

This report describes the spacecraft test targets and readout console as described in section 5.3.3 of the performance specification S-480-80. The spacecraft targets are to be used to provide a well-known radiometric reference for testing the functionality of the AMSU-A instruments at the spacecraft contractor's facility.

COBE - Cosmic Background Explorer

Science.gov Websites

with that from a precise blackbody. Data from the full four years of COBE observations continue to be stages in the COBE project. DIRBE (Diffuse Infrared Background Experiment) DIRBE has mapped the absolute sky brightness in 10 wavelength bands ranging from 1.25 microns to 240 microns. These data contain the

Reducing the biases in simulated polar climate by incorporating realistic surface spectral emissivity into the global climate model

NASA Astrophysics Data System (ADS)

Huang, X.; Chen, X.; Flanner, M.; Yang, P.; Feldman, D.; Kuo, C.

2017-12-01

Surface longwave emissivity can be less than unity and vary significantly with frequency. The emissivities of water, ice, and bare land all exhibit different spectral dependence, for both the far-IR and mid-IR bands. However, most climate models still assume blackbody surface in the longwave (LW) radiation scheme of their atmospheric modules. This study incorporates realistic surface spectral emissivity into the RRTMG_LW, the LW radiation scheme in CAM, which is the atmospheric component of the NCAR Community Earth System Model (CESM) version 1.1.1. Then we evaluate its impact on simulated climatology, especially for the polar regions. By ensuring the consistency of the broadband longwave flux across different modules of the CESM, the TOA energy balance in the simulation can be attained without additional tuning of the model. While the impact on global mean surface temperature is small, the surface temperature differences in Polar Regions are statistically significant. The mean surface temperature in Arctic in the modified CESM is 1.5K warmer than that in the standard CESM, reducing the cold bias that the standard CESM has with respect to observations. Accordingly the sea ice fraction in the modified CESM simulation is less than that in the standard CESM simulation by as much as 0.1, which significantly reduces the positive biases in the simulated sea ice coverage by the CESM. The largest sea-ice coverage difference happens in August and September, when new sea ice starts to form. The similar changes can be seen for the simulated Antarctic surface climate as well. In a nutshell, incorporating realistic surface spectral emissivity helps improving the fidelity of simulated surface energy budget in the polar region, which leads to a better simulation of the surface temperature and sea ice coverage.

Unusual X-ray burst profiles from 4U/MXB 1636-53

NASA Technical Reports Server (NTRS)

Sztajno, M.; Truemper, J.; Pietsch, W.; Van Paradijs, J.; Stollman, G.

1985-01-01

During a one day Exosat observation eight X-ray bursts from 4U/MXB 1636-53 are observed. Four of these were very unusual. Their peak fluxes were relatively low, and they showed a distinct double peak in their bolometric flux profiles. These new double-peaked bursts are unexplained by presently available models of X-ray bursts. It is possible that the energy release in these bursts proceeds in two 'steps'. The burst profiles are not the result of an expansion and subsequent contraction of the photosphere of the neutron star. Thus, they are very different from previously observed bursts which do show a double peak in certain energy ranges but not in their bolometric flux profiles; these are satisfactorily explained in terms of photospheric radius expansion and contraction. The anticorrelation between the apparent blackbody radius and blackbody temperature is discussed in terms of the nonPlanckian character of burst spectra and it is concluded that the model calculations reported by London, Taam, and Howard in 1984 give a reasonable first-order description of the observed apparent radius changes in X-ray bursts.

ROSAT observations of pulsed soft X-ray emission from PSR 1055-52

NASA Technical Reports Server (NTRS)

Oegelman, Hakki; Finley, John P.

1993-01-01

Utilizing the position-sensitive proportional counter and the high-resolution imager aboard the orbiting X-ray observatory ROSAT, we have detected pulsations at the radio period from the pulsar PSR 1055-52. The pulse shapes are energy-dependent and show a transition at about 0.5 keV where the phase angle of the pulse peak changes by about -120 deg and the pulsed fraction increases from 11 percent to 63 percent toward larger energies. Simple spectral models are found to be unsatisfactory, while multicomponent models, such as a soft blackbody and hard power-law tail, yield better fits to the pulse-height data. The hard power-law tail is consistent with the extension of the recently reported EGRET results and may indicate a common emission mechanism for the X-ray through GeV gamma-ray regime. The soft blackbody component with T(infinity) = (7.5 +/- 0.6) x 10 exp 5 K, if interpreted as the initial cooling of a neutron star, is consistent with standard cooling models and does not require the presence of exotic components.

Image Registration Using Single Cluster PHD Methods

NASA Astrophysics Data System (ADS)

Campbell, M.; Schlangen, I.; Delande, E.; Clark, D.

Cadets in the Department of Physics at the United States Air Force Academy are using the technique of slitless spectroscopy to analyze the spectra from geostationary satellites during glint season. The equinox periods of the year are particularly favorable for earth-based observers to detect specular reflections off satellites (glints), which have been observed in the past using broadband photometry techniques. Three seasons of glints were observed and analyzed for multiple satellites, as measured across the visible spectrum using a diffraction grating on the Academy’s 16-inch, f/8.2 telescope. It is clear from the results that the glint maximum wavelength decreases relative to the time periods before and after the glint, and that the spectral reflectance during the glint is less like a blackbody. These results are consistent with the presumption that solar panels are the predominant source of specular reflection. The glint spectra are also quantitatively compared to different blackbody curves and the solar spectrum by means of absolute differences and standard deviations. Our initial analysis appears to indicate a potential method of determining relative power capacity.

GRB110721A: An Extreme Peak Energy and Signatures of the Photosphere

NASA Technical Reports Server (NTRS)

Axelsson, M.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bellazzini, R.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Caliandro, G. A.;

Comparison of Geosynchronous Satellites Spectral Signatures During Glint Season

NASA Astrophysics Data System (ADS)

Weisz, D.; Dunsmore, A.; Key, J.; Tucker, R.; Weld, E.; Chun, F.; Tippets, R.

2016-09-01

Cadets in the Department of Physics at the United States Air Force Academy are using the technique of slitless spectroscopy to analyze the spectra from geostationary satellites during glint season. The equinox periods of the year are particularly favorable for earth-based observers to detect specular reflections off satellites (glints), which have been observed in the past using broadband photometry techniques. Three seasons of glints were observed and analyzed for multiple satellites, as measured across the visible spectrum using a diffraction grating on the Academy's 16-inch, f/8.2 telescope. It is clear from the results that the glint maximum wavelength decreases relative to the time periods before and after the glint, and that the spectral reflectance during the glint is less like a blackbody. The glint spectra are also quantitatively compared to different blackbody curves and the solar spectrum by means of absolute differences. Our initial analysis appears to indicate a potential method of determining relative power capacity. These results are consistent with the presumption that solar panels are the predominant source of specular reflection.

DOE Office of Scientific and Technical Information (OSTI.GOV)

C. BARNES

Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either overdense, operating at high density relative to the magnetic field (e.g. {omega}{sub pe} >> {Omega}{sub ce} in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition ({tau} > 2). Electron Bernstein waves (EBWs) are electrostatic waves which can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers, as amore » result of their large K{sub i}. This talk reports on measurements of EBW emission on the CDX-U spherical torus, where B{sub 0} {approx} 2 kG, {approx} 10{sup 13} cm{sup -3} and T{sub e} {approx} 10 - 200 eV. Results will be presented for both direct detection of EBWs and for mode-converted EBW emission. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multi-point Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be {le} T{sub e} and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe was employed to measure changes in edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Changes in the mode conversion efficiency may explain the observation of mode-converted EBW radiation temperatures below T{sub e}. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where {omega}{sub pe} >> {Omega}{sub ce}.« less

On Radiative Factors in Planetary Rings: New Insight Derived from Cassini CIRS Observations at Saturn Equinox

NASA Astrophysics Data System (ADS)

Brooks, S. M.; Spilker, L. J.; Pilorz, S.; Edgington, S. G.; Deau, E.; Morishima, R.

2012-12-01

Since arriving at Saturn in 2004, Cassini's Composite Infrared Spectrometer has recorded tens of millions of spectra of Saturn's rings (personal communication, M. Segura). CIRS records far infrared radiation (16.7-1000 microns) at focal plane 1 (FP1). Thermal emission from Saturn's rings peaks at FP1 wavelengths. CIRS spectra are well characterized as blackbody emission at an effective temperature Te, multiplied by a scalar factor related to ring emissivity (Spilker et al. [2005, 2006]). CIRS can therefore characterize the rings' temperature and study the thermal environment to which the ring particles are subject. We focus on CIRS data from the 2009 Saturnian equinox. As the Sun's disk crossed the ring plane, CIRS obtained several radial scans of the rings at a variety of phase angles, local hour angles and distances. With the Sun's rays striking the rings at an incidence angle of zero, solar heating is virtually absent, and thermal radiation from Saturn and sunlight reflected by Saturn dominate the thermal environment. These observations appear to present a paradox. Equinox data show that the flux of thermal energy radiated by the rings can even exceed the energy incident upon them as prescribed by thermal models, particularly in the C ring and Cassini Division (Ferrari and Leyrat [2006], Morishima et al. [2009, 2010]). Conservation principles suggest that such models underestimate heating of the rings in these cases, as it is clearly unphysical for the rings to radiate significantly more energy than is incident upon them. In this presentation, we will describe our efforts to resolve this paradox and determine what doing so can teach us about Saturn's rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2012 California Institute of Technology. Government sponsorship acknowledged.

Application of a relativistic accretion disc model to X-ray spectra of LMC X-1 and GRO J1655-40

NASA Astrophysics Data System (ADS)

Gierliński, Marek; Maciołek-Niedźwiecki, Andrzej; Ebisawa, Ken

2001-08-01

We present a general relativistic accretion disc model and its application to the soft-state X-ray spectra of black hole binaries. The model assumes a flat, optically thick disc around a rotating Kerr black hole. The disc locally radiates away the dissipated energy as a blackbody. Special and general relativistic effects influencing photons emitted by the disc are taken into account. The emerging spectrum, as seen by a distant observer, is parametrized by the black hole mass and spin, the accretion rate, the disc inclination angle and the inner disc radius. We fit the ASCA soft-state X-ray spectra of LMC X-1 and GRO J1655-40 by this model. We find that, having additional limits on the black hole mass and inclination angle from optical/UV observations, we can constrain the black hole spin from X-ray data. In LMC X-1 the constraint is weak, and we can only rule out the maximally rotating black hole. In GRO J1655-40 we can limit the spin much better, and we find 0.68<=a<=0.88. Accretion discs in both sources are radiation-pressure dominated. We do not find Compton reflection features in the spectra of any of these objects.

Experimental Demonstration of Adaptive Infrared Multispectral Imaging using Plasmonic Filter Array

PubMed Central

Jang, Woo-Yong; Ku, Zahyun; Jeon, Jiyeon; Kim, Jun Oh; Lee, Sang Jun; Park, James; Noyola, Michael J.; Urbas, Augustine

2016-01-01

In our previous theoretical study, we performed target detection using a plasmonic sensor array incorporating the data-processing technique termed “algorithmic spectrometry”. We achieved the reconstruction of a target spectrum by extracting intensity at multiple wavelengths with high resolution from the image data obtained from the plasmonic array. The ultimate goal is to develop a full-scale focal plane array with a plasmonic opto-coupler in order to move towards the next generation of versatile infrared cameras. To this end, and as an intermediate step, this paper reports the experimental demonstration of adaptive multispectral imagery using fabricated plasmonic spectral filter arrays and proposed target detection scenarios. Each plasmonic filter was designed using periodic circular holes perforated through a gold layer, and an enhanced target detection strategy was proposed to refine the original spectrometry concept for spatial and spectral computation of the data measured from the plasmonic array. Both the spectrum of blackbody radiation and a metal ring object at multiple wavelengths were successfully reconstructed using the weighted superposition of plasmonic output images as specified in the proposed detection strategy. In addition, plasmonic filter arrays were theoretically tested on a target at extremely high temperature as a challenging scenario for the detection scheme. PMID:27721506

Advances in real-time millimeter-wave imaging radiometers for avionic synthetic vision

NASA Astrophysics Data System (ADS)

Lovberg, John A.; Chou, Ri-Chee; Martin, Christopher A.; Galliano, Joseph A., Jr.

1995-06-01

Millimeter-wave imaging has advantages over conventional visible or infrared imaging for many applications because millimeter-wave signals can travel through fog, snow, dust, and clouds with much less attenuation than infrared or visible light waves. Additionally, passive imaging systems avoid many problems associated with active radar imaging systems, such as radar clutter, glint, and multi-path return. ThermoTrex Corporation previously reported on its development of a passive imaging radiometer that uses an array of frequency-scanned antennas coupled to a multichannel acousto-optic spectrum analyzer (Bragg-cell) to form visible images of a scene through the acquisition of thermal blackbody radiation in the millimeter-wave spectrum. The output from the Bragg cell is imaged by a standard video camera and passed to a computer for normalization and display at real-time frame rates. An application of this system is its incorporation as part of an enhanced vision system to provide pilots with a synthetic view of a runway in fog and during other adverse weather conditions. Ongoing improvements to a 94 GHz imaging system and examples of recent images taken with this system will be presented. Additionally, the development of dielectric antennas and an electro- optic-based processor for improved system performance, and the development of an `ultra- compact' 220 GHz imaging system will be discussed.

Constraining Accretion Signatures of Exoplanets in the TW Hya Transitional Disk

NASA Astrophysics Data System (ADS)

Uyama, Taichi; Tanigawa, Takayuki; Hashimoto, Jun; Tamura, Motohide; Aoyama, Yuhiko; Brandt, Timothy D.; Ishizuka, Masato

2017-09-01

We present a near-infrared direct imaging search for accretion signatures of possible protoplanets around the young stellar object (YSO) TW Hya, a multi-ring disk exhibiting evidence of planet formation. The Paβ line (1.282 μm) is an indication of accretion onto a protoplanet, and its intensity is much higher than that of blackbody radiation from the protoplanet. We focused on the Paβ line and performed Keck/OSIRIS spectroscopic observations. Although spectral differential imaging (SDI) reduction detected no accretion signatures, the results of the present study allowed us to set 5σ detection limits for Paβ emission of 5.8 × 10-18 and 1.5 × 10-18 erg-1 s-1 cm-2 at 0.″4 and 1.″6, respectively. We considered the mass of potential planets using theoretical simulations of circumplanetary disks and hydrogen emission. The resulting masses were 1.45 ± 0.04 M J and {2.29}-0.04+0.03 {M}{{J}} at 25 and 95 au, respectively, which agree with the detection limits obtained from previous broadband imaging. The detection limits should allow for the identification of protoplanets as small as ˜1 M J, which may assist in direct imaging searches around faint YSOs for which extreme adaptive optics instruments are unavailable.

Ghost features in Doppler-broadened spectra of rovibrational transitions in trapped HD+ ions

NASA Astrophysics Data System (ADS)

Patra, Sayan; Koelemeij, J. C. J.

2017-02-01

Doppler broadening plays an important role in laser rovibrational spectroscopy of trapped deuterated molecular hydrogen ions (HD+), even at the millikelvin temperatures achieved through sympathetic cooling by laser-cooled beryllium ions. Recently, Biesheuvel et al. (2016) presented a theoretical lineshape model for such transitions which not only considers linestrengths and Doppler broadening, but also the finite sample size and population redistribution by blackbody radiation, which are important in view of the long storage and probe times achievable in ion traps. Here, we employ the rate equation model developed by Biesheuvel et al. to theoretically study the Doppler-broadened hyperfine structure of the (v, L) : (0, 3) → (4, 2) rovibrational transition in HD+ at 1442 nm. We observe prominent yet hitherto unrecognized ghost features in the simulated spectrum, whose positions depend on the Doppler width, transition rates, and saturation levels of the hyperfine components addressed by the laser. We explain the origin and behavior of such features, and we provide a simple quantitative guideline to assess whether ghost features may appear. As such ghost features may be common to saturated Doppler-broadened spectra of rotational and vibrational transitions in trapped ions composed of partly overlapping lines, our work illustrates the necessity to use lineshape models that take into account all the relevant physics.

New Measurement of the Electron Magnetic Moment and the Fine Structure Constant: A First Application of a One-Electron Quantum Cyclotron

ScienceCinema

Gabrielse, Gerald

2018-05-22

Remarkably, the famous UW measurement of the electron magnetic moment has stood since 1987. With QED theory, this measurement has determined the accepted value of the fine structure constant. This colloquium is about a new Harvard measurement of these fundamental constants. The new measurement has an uncertainty that is about six times smaller, and it shifts the values by 1.7 standard deviations. One electron suspended in a Penning trap is used for the new measurement, like in the old measurement. What is different is that the lowest quantum levels of the spin and cyclotron motion are resolved, and the cyclotron as well as spin frequencies are determined using quantum jump spectroscopy. In addition, a 0.1 mK Penning trap that is also a cylindrical microwave cavity is used to control the radiation field, to suppress spontaneous emission by more than a factor of 100, to control cavity shifts, and to eliminate the blackbody photons that otherwise stimulate excitations from the cyclotron ground state. Finally, great signal-to-noise for one-quantum transitions is obtained using electronic feedback to realize the first one-particle self-excited oscillator. The new methods may also allow a million times improved measurement of the 500 times small antiproton magnetic moment.

GIFTS SM EDU Level 1B Algorithms

NASA Technical Reports Server (NTRS)

Tian, Jialin; Gazarik, Michael J.; Reisse, Robert A.; Johnson, David G.

2007-01-01

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) SensorModule (SM) Engineering Demonstration Unit (EDU) is a high resolution spectral imager designed to measure infrared (IR) radiances using a Fourier transform spectrometer (FTS). The GIFTS instrument employs three focal plane arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. This paper describes the GIFTS SM EDU Level 1B algorithms involved in the calibration. The GIFTS Level 1B calibration procedures can be subdivided into four blocks. In the first block, the measured raw interferograms are first corrected for the detector nonlinearity distortion, followed by the complex filtering and decimation procedure. In the second block, a phase correction algorithm is applied to the filtered and decimated complex interferograms. The resulting imaginary part of the spectrum contains only the noise component of the uncorrected spectrum. Additional random noise reduction can be accomplished by applying a spectral smoothing routine to the phase-corrected spectrum. The phase correction and spectral smoothing operations are performed on a set of interferogram scans for both ambient and hot blackbody references. To continue with the calibration, we compute the spectral responsivity based on the previous results, from which, the calibrated ambient blackbody (ABB), hot blackbody (HBB), and scene spectra can be obtained. We now can estimate the noise equivalent spectral radiance (NESR) from the calibrated ABB and HBB spectra. The correction schemes that compensate for the fore-optics offsets and off-axis effects are also implemented. In the third block, we developed an efficient method of generating pixel performance assessments. In addition, a random pixel selection scheme is designed based on the pixel performance evaluation. Finally, in the fourth block, the single pixel algorithms are applied to the entire FPA.

The Geminga Pulsar: Soft X-Ray Variability and an EUVE Observation

NASA Technical Reports Server (NTRS)

Halpern, Jules P.; Martin, Christopher; Marshall, Herman L.

1996-01-01

We observed the Geminga pulsar with the EUVE satellite, detecting pulsed emission in the Deep Survey imager. Joint spectral fits of the EUVE flux with ROSAT PSPC data are consistent with thermal plus power-law models in which the thermal component makes the dominant contribution to the soft X-ray flux seen by EUVE and ROSAT. The data are consistent with blackbody emission of T = (4-6) x 10(exp 5) K over most of the surface of the star at the measured parallax distance of 160 pc. Although model atmospheres are more realistic, and can fit the data with effective temperatures a factor of 2 lower, current data would not discriminate between these and blackbody models. We also find evidence for variability of Geminga's soft X-ray pulse shape. Narrow dips in the light curve that were present in 1991 had largely disappeared in 1993/1994, causing the pulsed fraction to decline from 32% to 18%. If the dips are attributed to cyclotron resonance scattering by an e(+/-) plasma on closed magnetic field lines, then the process that resupplies that plasma must be variable.

High-speed and on-chip graphene blackbody emitters for optical communications by remote heat transfer.

PubMed

Miyoshi, Yusuke; Fukazawa, Yusuke; Amasaka, Yuya; Reckmann, Robin; Yokoi, Tomoya; Ishida, Kazuki; Kawahara, Kenji; Ago, Hiroki; Maki, Hideyuki

2018-03-29

High-speed light emitters integrated on silicon chips can enable novel architectures for silicon-based optoelectronics, such as on-chip optical interconnects, and silicon photonics. However, conventional light sources based on compound semiconductors face major challenges for their integration with a silicon-based platform because of their difficulty of direct growth on a silicon substrate. Here we report ultra-high-speed (100-ps response time), highly integrated graphene-based on-silicon-chip blackbody emitters in the near-infrared region including telecommunication wavelength. Their emission responses are strongly affected by the graphene contact with the substrate depending on the number of graphene layers. The ultra-high-speed emission can be understood by remote quantum thermal transport via surface polar phonons of the substrates. We demonstrated real-time optical communications, integrated two-dimensional array emitters, capped emitters operable in air, and the direct coupling of optical fibers to the emitters. These emitters can open new routes to on-Si-chip, small footprint, and high-speed emitters for highly integrated optoelectronics and silicon photonics.

Effects of water-emission anisotropy on multispectral remote sensing at thermal wavelengths of ocean temperature and of cirrus clouds

NASA Technical Reports Server (NTRS)

Otterman, J.; Susskind, J.; Dalu, G.; Kratz, D.; Goldberg, I. L.

1992-01-01

The impact of water-emission anisotropy on remotedly sensed long-wave data has been studied. Water emission is formulated from a calm body for a facile computation of radiative transfer in the atmosphere. The error stemming from the blackbody assumption are calculated for cases of a purely absorbing or a purely scattering atmosphere taking the optical properties of the atmosphere as known. For an absorbing atmosphere, the errors in the sea-surface temperature (SST) are found to be always reduced and be the same whether measurements are made from space or at any level of the atmosphere. The inferred optical thickness tau of an absorbing layer can be in error under the blackbody assumption by a delta tau of 0.01-0.08, while the inferred optical thickness of a scattering layer can be in error by a larger amount, delta tau of 0.03-0.13. It is concluded that the error delta tau depends only weakly on the actual optical thickness and the viewing angle, but is rather sensitive to the wavelength of the measurement.

The Geminga Pulsar: Soft X-Ray Variability and an EUVE Observation

NASA Technical Reports Server (NTRS)

Halpern, Jules P.; Martin, Christopher; Marshall, Herman L.; Oliversen, Ronald (Technical Monitor)

2001-01-01

We observed the Geminga pulsar with the EUVE satellite, detecting pulsed emission in the Deep Survey imager. Joint spectral fits of the EUVE flux with ROSAT PSPC data are consistent with thermal plus power-law models in which the thermal component makes the dominant contribution to the soft X-ray flux seen by EUVE and ROSAT. The data are consistent with blackbody emission of T = (4 - 6) x 10(exp 5) K over most of the surface of the star at the measured parallax distance of 160 pc. Although model atmospheres are more realistic, and can fit the data with effective temperatures a factor of 2 lower, current data would not discriminate between these and blackbody models. We also find evidence for variability of Geminga's soft X-ray pulse shape. Narrow dips in the light curve that were present in 1991 had largely disappeared in 1993/1994, causing the pulsed fraction to decline from 32% to 18%. If the dips are attributed to cyclotron resonance scattering by an e1 plasma on closed magnetic field lines, then the process that resupplies that plasma must be variable.

Optimized thermal amplification in a radiative transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prod'homme, Hugo; Ordonez-Miranda, Jose; Ezzahri, Younes, E-mail: younes.ezzahri@univ-poitiers.fr

The thermal performance of a far-field radiative transistor made up of a VO{sub 2} base in between a blackbody collector and a blackbody emitter is theoretically studied and optimized. This is done by using the grey approximation on the emissivity of VO{sub 2} and deriving analytical expressions for the involved heat fluxes and transistor amplification factor. It is shown that this amplification factor can be maximized by tuning the base temperature close to its critical one, which is determined by the temperature derivative of the VO{sub 2} emissivity and the equilibrium temperatures of the collector and emitter. This maximization ismore » the result of the presence of two bi-stable temperatures appearing during the heating and cooling processes of the VO{sub 2} base and enables a thermal switching (temperature jump) characterized by a sizeable variation of the collector-to-base and base-to-emitter heat fluxes associated with a slight change of the applied power to the base. This switching effect leads to the optimization of the amplification factor and therefore it could be used for thermal modulation purposes.« less

Spectral reflectance properties of black chrome for use as a solar selective coating

NASA Technical Reports Server (NTRS)

Mcdonald, G. E.

1974-01-01

The NASA-Lewis Research Center has determined that a widely available commercially electroplated decorative finish known as black chrome has desirable solar selective properties. Black chrome electroplated coating has high absorbtance in the solar spectrum and low emissivity in the 250 F blackbody thermal spectrum. The spectral reflectance properties of a commercially prepared black chrome on steel have been measured. Values are presented for reflectance of the black chrome, and compared with the reflectance of black paint and with two available samples of black nickel which had been prepared for solar selective properties. The reflectance of black chrome, of the two black nickels, and of black paint integrated over the solar spectrum for air mass 2 were 0.132, 0.123, 0.133, and 0.033, respectively. The reflectance of the black chrome, two black nickels, and of the black paint integrated over the blackbody spectrum for 250 F from 3 to 15 microns are 0.912, 0.934, 0.891, and 0.033, respectively. These reflectance measurements indicate absorptivity-to-emissivity values of 9.8, 13.8, 8.0, and 1.00, respectively.

Spitzer Observations of the New Luminous Red Nova M85 OT2006-1

NASA Astrophysics Data System (ADS)

Rau, A.; Kulkarni, S. R.; Ofek, E. O.; Yan, L.

2007-04-01

M85 OT2006-1 is the latest and most brilliant addition to the small group of known luminous red novae (LRNe). An identifying characteristic of the previously detected events (M31 RV, V4332 Sgr, and V838 Mon) was a spectral redward evolution connected with an emerging infrared component following the optical decay. Here we report on the discovery of a similar feature in Keck NIRC and Spitzer photometry of M85 OT2006-1 6 months posteruption. We find that its 2.1-22 μm spectral energy distribution is best described by a blackbody with effective temperature Teff=950+/-150 K and bolometric luminosity L=2.9+0.4-0.5×105 Lsolar. Assuming spherical geometry, the blackbody effective radius, R=2.0+0.6-0.4×104 Rsolar, and corresponding expansion velocity, v=870+260-180 km s-1, are remarkably similar to the properties of M31 RV 70 days after its eruption. Furthermore, we propose a search strategy for LRNe in the local universe making use of the longevity of their infrared excess emission and discuss the expected number of events in the Spitzer Infrared Nearby Galaxies Survey.

CIRiS: Compact Infrared Radiometer in Space

NASA Astrophysics Data System (ADS)

Osterman, D. P.; Collins, S.; Ferguson, J.; Good, W.; Kampe, T.; Rohrschneider, R.; Warden, R.

2016-09-01

The Compact Infrared Radiometer in Space (CIRiS) is a thermal infrared radiometric imaging instrument under development by Ball Aerospace for a Low Earth Orbit mission on a CubeSat spacecraft. Funded by the NASA Earth Science Technology Office's In-Space Validation of Earth Science Technology (InVEST) program, the mission objective is technology demonstration for improved on-orbit radiometric calibration. The CIRiS calibration approach uses a scene select mirror to direct three calibration views to the focal plane array and to transfer the resulting calibrated response to earth images. The views to deep space and two blackbody sources, including one at a selectable temperature, provide multiple options for calibration optimization. Two new technologies, carbon nanotube blackbody sources and microbolometer focal plane arrays with reduced pixel sizes, enable improved radiometric performance within the constrained 6U CubeSat volume. The CIRiS instrument's modular design facilitates subsystem modifications as required by future mission requirements. CubeSat constellations of CIRiS and derivative instruments offer an affordable approach to achieving revisit times as short as one day for diverse applications including water resource and drought management, cloud, aerosol, and dust studies, and land use and vegetation monitoring. Launch is planned for 2018.

Solar pumped laser technology options for space power transmission

NASA Technical Reports Server (NTRS)

Conway, E. J.

1986-01-01

An overview of long-range options for in-space laser power transmission is presented. The focus is on the new technology and research status of solar-pumped lasers and their solar concentration needs. The laser options include gas photodissociation lasers, optically-pumped solid-state lasers, and blackbody-pumped transfer lasers. The paper concludes with a summary of current research thrusts.

Minidisks in Binary Black Hole Accretion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryan, Geoffrey; MacFadyen, Andrew, E-mail: gsr257@nyu.edu

Newtonian simulations have demonstrated that accretion onto binary black holes produces accretion disks around each black hole (“minidisks”), fed by gas streams flowing through the circumbinary cavity from the surrounding circumbinary disk. We study the dynamics and radiation of an individual black hole minidisk using 2D hydrodynamical simulations performed with a new general relativistic version of the moving-mesh code Disco. We introduce a comoving energy variable that enables highly accurate integration of these high Mach number flows. Tidally induced spiral shock waves are excited in the disk and propagate through the innermost stable circular orbit, providing a Reynolds stress thatmore » causes efficient accretion by purely hydrodynamic means and producing a radiative signature brighter in hard X-rays than the Novikov–Thorne model. Disk cooling is provided by a local blackbody prescription that allows the disk to evolve self-consistently to a temperature profile where hydrodynamic heating is balanced by radiative cooling. We find that the spiral shock structure is in agreement with the relativistic dispersion relation for tightly wound linear waves. We measure the shock-induced dissipation and find outward angular momentum transport corresponding to an effective alpha parameter of order 0.01. We perform ray-tracing image calculations from the simulations to produce theoretical minidisk spectra and viewing-angle-dependent images for comparison with observations.« less

Statistical thermodynamics and the size distributions of tropical convective clouds.

NASA Astrophysics Data System (ADS)

Garrett, T. J.; Glenn, I. B.; Krueger, S. K.; Ferlay, N.

2017-12-01

Parameterizations for sub-grid cloud dynamics are commonly developed by using fine scale modeling or measurements to explicitly resolve the mechanistic details of clouds to the best extent possible, and then to formulating these behaviors cloud state for use within a coarser grid. A second is to invoke physical intuition and some very general theoretical principles from equilibrium statistical thermodynamics. This second approach is quite widely used elsewhere in the atmospheric sciences: for example to explain the heat capacity of air, blackbody radiation, or even the density profile or air in the atmosphere. Here we describe how entrainment and detrainment across cloud perimeters is limited by the amount of available air and the range of moist static energy in the atmosphere, and that constrains cloud perimeter distributions to a power law with a -1 exponent along isentropes and to a Boltzmann distribution across isentropes. Further, the total cloud perimeter density in a cloud field is directly tied to the buoyancy frequency of the column. These simple results are shown to be reproduced within a complex dynamic simulation of a tropical convective cloud field and in passive satellite observations of cloud 3D structures. The implication is that equilibrium tropical cloud structures can be inferred from the bulk thermodynamic structure of the atmosphere without having to analyze computationally expensive dynamic simulations.

A comprehensive study of high-energy gamma-ray and radio emission from Cyg X-3

NASA Astrophysics Data System (ADS)

Zdziarski, Andrzej A.; Malyshev, Denys; Dubus, Guillaume; Pooley, Guy G.; Johnson, Tyrel; Frankowski, Adam; de Marco, Barbara; Chernyakova, Maria; Rao, A. R.

2018-06-01

We study high-energy γ-rays observed from Cyg X-3 by the Fermi Large Area Telescope and the 15-GHz emission observed by the Ryle Telescope and the Arcminute Microkelvin Imager. We measure the γ-ray spectrum averaged over strong flares much more accurately than before, and find it well modelled by Compton scattering of stellar radiation by relativistic electrons with the power law index of ≃3.5 and a low-energy cutoff at the Lorentz factor of ˜103. We find a weaker spectrum in the soft spectral state, but only upper limits in the hard and intermediate states. We measure strong orbital modulation during the flaring state, well modelled by anisotropic Compton scattering of blackbody photons from the donor by jet relativistic electrons. We discover a weaker orbital modulation of the 15 GHz radio emission, which is well modelled by free-free absorption by the stellar wind. We then study cross-correlations between radio, γ-ray and X-ray emissions. We find the cross-correlation between the radio and γ-ray emissions peaks at a lag less than 1 d, while we detect a distinct radio lag of ˜50 d with respect to the soft X-rays in the soft spectral state.

Correcting Geophysical Fallacies

NASA Astrophysics Data System (ADS)

Barbat, W. N.

2013-12-01

The escape velocity from a Big Bang explosion would greatly exceed the speed of light, which is impossible; William Tifft's (1976-77) observations of a common stepwise decline in photon size of 72.5 km/sec replaces a universal Doppler Red Shift, so the universe is not expanding; and the idea that all the mass and energy of the universe were instantly created is unscientific. Joseph Larmor's 1897 equation relates the radiation of photons from a moving electric charge to the square of a change of the acceleration of the charge. Hence the continual centripetal acceleration of orbiting electrons continually radiates low grade photon heat (Zero Point Energy). Shpenkov and Kreidik (2008) found that the heat source which sustains the Cosmic Background Energy at the measured peak blackbody temperature of 2.725+/-0.002K must be due to radiation from the orbital electron motion of hydrogen at its fundamental period, which they calculated to be 2.7289K. Cosmic Background Energy is not left over from a Big Bang 13 billion years ago. Of course, if nature can create energy, then it is reasonable to expect that man can create energy too. Importantly, the creation of photons by orbiting electrons and spinning protons also creates mass. Isaac Newton showed in Book 3 of Opticks that light rays bend as they pass closely over a sharp knife edge, and that the closer the ray is to the knife edge, the more the light path bends. Newton thus showed that corpuscles of light (photons) obey the law of gravitation, so photons possess mass. Photon creation inside stars builds up intense heat and pressure, splitting photons into electrons and positrons. A large positron and photon can apparently combine into a three lump particle with a charge of plus one, making a new proton. Hollow electrons can apparently surround a proton, making a neutron for fission. A small spun-off star advances up the main sequence until a buildup of iron cools and shrinks the core from its hydrogen envelope, leaving a planet. Over eons, planets increase to 70-90% of older galaxies to comprise Dark Matter. Radiation from orbiting electrons and spinning protons would comprise Dark Energy.

Exploration of Integrated Visible to Near-, Shortwave-, and Longwave-Infrared (Full-Range) Spectral Analysis

DTIC Science & Technology

2014-09-01

4 Figure 2. The four fundamental energy interactions with matter (from Olsen, 2014). ..... 4 Figure 3. Comparison of Blackbody, Graybody...15 Figure 10. Mineral maps of Comstock mining district around Virginia City, Nevada (from Vaughan & Calvin...23 Figure 13. Comparison of SEBASS emissivity spectrum (hydrothermal silica, Cuprite, NV) and laboratory spectrum of quartz (JHU Minerals

Laser Optics/Combustion Diagnostics.

DTIC Science & Technology

1986-07-01

of Blackbody at Various Temperatures (K). . . 153 21 Transmission Attenuation of Quartz Fiber ... ............ .. 155 22 Schematic Diagram of Receiver...transfer pro- time-multiplexed via different lengths of fiber -optic cable to gram (machine code) of the TN- 1710 controls the handshak- a single...linewidths depend upon temperature, pressure, and , composition of the medium as well as the J value of the line. Collisional effects, as demonstrated for

Analysis of TIMS performance subjected to simulated wind blast

NASA Technical Reports Server (NTRS)

Jaggi, S.; Kuo, S.

1992-01-01

The results of the performance of the Thermal Infrared Multispectral Scanner (TIMS) when it is subjected to various wind conditions in the laboratory are described. Various wind conditions were simulated using a 24 inch fan or combinations of air jet streams blowing toward either or both of the blackbody surfaces. The fan was used to simulate a large volume of air flow at moderate speeds (up to 30 mph). The small diameter air jets were used to probe TIMS system response in reaction to localized wind perturbations. The maximum nozzle speed of the air jet was 60 mph. A range of wind directions and speeds were set up in the laboratory during the test. The majority of the wind tests were conducted under ambient conditions with the room temperature fluctuating no more than 2 C. The temperature of the high speed air jet was determined to be within 1 C of the room temperature. TIMS response was recorded on analog tape. Additional thermistor readouts of the blackbody temperatures and thermocouple readout of the ambient temperature were recorded manually to be compared with the housekeeping data recorded on the tape. Additional tests were conducted under conditions of elevated and cooled room temperatures. The room temperature was varied between 19.5 to 25.5 C in these tests. The calibration parameters needed for quantitative analysis of TIMS data were first plotted on a scanline-by-scanline basis. These parameters are the low and high blackbody temperature readings as recorded by the TIMS and their corresponding digitized count values. Using these values, the system transfer equations were calculated. This equation allows us to compute the flux for any video count by computing the slope and intercept of the straight line that relates the flux to the digital count. The actual video of the target (the lab floor in this case) was then compared with a simulated target. This simulated target was assumed to be a blackbody at emissivity of .95 degrees and the temperature was assumed to be at ambient temperature as recorded by the TIMS for each scanline. Using the slope and the intercept the flux corresponding to this target was converted into digital counts. The counts were observed to have a strong correlation with the actual video as recorded by the TIMS. The attached graphs describe the performance of the TIMS when compressed air is blown at each one of the blackbodies at different speeds. The effect of blowing a fan and changing the room temperature is also being analyzed. Results indicate that the TIMS system responds to variation in wind speed in real time and maintains the capability to produce accurate temperatures on a scan line basis.

NIST TXR Validation of S-HIS radiances and a UW-SSEC Blackbody

NASA Astrophysics Data System (ADS)

Taylor, J. K.; O'Connell, J.; Rice, J. P.; Revercomb, H. E.; Best, F. A.; Tobin, D. C.; Knuteson, R. O.; Adler, D. P.; Ciganovich, N. C.; Dutcher, S. T.; Laporte, D. D.; Ellington, S. D.; Werner, M. W.; Garcia, R. K.

2007-12-01

The ability to accurately validate infrared spectral radiances measured from space by direct comparison with airborne spectrometer radiances was first demonstrated using the Scanning High-resolution Interferometer Sounder (S-HIS) aircraft instrument flown under the AIRS on the NASA Aqua spacecraft in 2002 with subsequent successful comparisons in 2004 and 2006. The comparisons span a range of conditions, including arctic and tropical atmospheres, daytime and nighttime, and ocean and land surfaces. Similar comprehensive and successful comparisons have also been conducted with S-HIS for the MODIS sensors, the Tropospheric Emission Spectrometer (TES), and most recently the MetOp Infrared Atmospheric Sounding Interferometer (IASI). These comparisons are part of a larger picture that already shows great progress toward transforming our ability to make, and verify, highly accurate spectral radiance observations from space. A key challenge, especially for climate, is to carefully define the absolute accuracy of satellite radiances. Our vision of the near-term future of spectrally resolved infrared radiance observation includes a new space-borne mission that provides benchmark observations of the emission spectrum for climate. This concept, referred to as the CLimate Absolute Radiance and REfractivity Observatory (CLARREO) in the recent NRC Decadal Survey provides more complete spectral and time-of-day coverage and would fly basic physical standards to eliminate the need to assume on-board reference stability. Therefore, the spectral radiances from this mission will also serve as benchmarks to propagate a highly accurate calibration to other space-borne IR instruments. For the current approach of calibrating infrared flight sensors, in which thermal vacuum tests are conducted before launch and stability is assumed after launch, in-flight calibration validation is essential for highly accurate applications. At present, airborne observations provide the only source of direct radiance validation with resulting traceable uncertainties approaching the level required for remote sensing and climate applications (0.1 K 3- sigma). For the calibration validation process to be accurate, repeatable, and meaningful, the reference instrument must be extremely well characterized and understood, carefully maintained, and accurately calibrated, with the calibration accuracy of the reference instrument tied to absolute standards. Tests of the S-HIS absolute calibration have been conducted using the NIST transfer radiometer (TXR). The TXR provides a more direct connection to the Blackbody reference sources maintained by NIST than the normal traceability of blackbody temperature scales and paint emissivity measurements. Two basic tests were conducted: (1) comparison of radiances measured by the S-HIS to those from the TXR, and (2) measuring the reflectivity of a UW-SSEC blackbody by using the TXR as a stable detector. Preliminary results from both tests are very promising for confirming and refining the expected absolute accuracy of the S-HIS.

Dielectric polarization in the Planck theory of sonoluminescence.

PubMed

Prevenslik, T V

1998-11-01

Sonoluminescence observed in the cavitation of liquid H2O may be explained by the Planck theory of SL, which treats the bubbles as collapsing miniature masers having optical waves standing in resonance with the dimensions of the bubble cavity. Microwaves are shown to be created from the Planck energy of the standing waves, provided the bubble wall can be treated as a perfect blackbody surface. Liquid H2O is strongly absorbent in the ultraviolet and there the bubble approaches a Planck blackbody enclosure. The microwaves are created at frequencies proportional to the bubble collapse velocity only to be promptly absorbed by the rotation quantum states of the H2O and other bubble wall molecules. The microwaves are absorbed discretely at rotation line frequencies, or continuously by dipole rotation at frequencies from 1 to 30 GHz. In the liquid state, molecular rotation of the H2O molecule is hindered and the microwave energy is rapidly turned into bending energy by intermolecular collisions. Subsequently, the bubble wall molecules may thereby ionize and produce visible photons. The microwaves create intense electrical fields in the bubble wall by dielectric polarization. If the gases adjacent to the bubble wall undergo electrical breakdown, free electrons are created, thereby providing sonoluminescence with a magnetic field effect.

Low-cost microwave radiometry for remote sensing of soil moisture

NASA Astrophysics Data System (ADS)

Chikando, Eric Ndjoukwe

2007-12-01

Remote sensing is now widely regarded as a dominant means of studying the Earth and its surrounding atmosphere. This science is based on blackbody theory, which states that all objects emit broadband electromagnetic radiation proportional to their temperature. This thermal emission is detectable by radiometers---highly sensitive receivers capable of measuring extremely low power radiation across a continuum of frequencies. In the particular case of a soil surface, one important parameter affecting the emitted radiation is the amount of water content or, soil moisture. A high degree of precision is required when estimating soil moisture in order to yield accurate forecasting of precipitations and short-term climate variability such as storms and hurricanes. Rapid progress within the remote sensing community in tackling current limitations necessitates an awareness of the general public towards the benefits of the science. Information about remote sensing instrumentation and techniques remain inaccessible to many higher-education institutions due to the high cost of instrumentation and the current general inaccessibility of the science. In an effort to draw more talent within the field, more affordable and reliable scientific instrumentation are needed. This dissertation introduces the first low-cost handheld microwave instrumentation fully capable of surface soil moisture studies. The framework of this research is two-fold. First, the development of a low-cost handheld microwave radiometer using the well-known Dicke configuration is examined. The instrument features a super-heterodyne architecture and is designed following a microwave integrated circuit (MIC) system approach. Validation of the instrument is performed by applying it to various soil targets and comparing measurement results to gravimetric technique measured data; a proven scientific method for determining volumetric soil moisture content. Second, the development of a fully functional receiver RF front-end is presented. This receiver module is designed in support to a digital radiometer effort under development by the Center of Microwave Satellite and RF Engineering (COMSARE) at Morgan State University. The topology of the receiver includes a low-noise amplifier, bandpass filters and a three-stage gain amplifier. Design, characterization and evaluation of these system blocks are detailed within the framework of this dissertation.

GRB110721A: An extreme peak energy and signatures of the photosphere

DOE PAGES

Axelsson, M.; Baldini, L.; Barbiellini, G.; ...

2012-09-17

GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). This burst consisted of one major emission episode which lasted for ~24.5 s (in the GBM) and had a peak flux of (5.7 ± 0.2) × 10 –5 erg s –1 cm –2. The time-resolved emission spectrum is best modeled with a combination of a Band function and a blackbody spectrum. The peak energy of the Band component was initially 15 ± 2 MeV, which is the highest value ever detected in a GRB. We mademore » this measurement by combining GBM/BGO data with LAT Low Energy events to achieve continuous 10-100 MeV coverage. The peak energy later decreased as a power law in time with an index of –1.89 ± 0.10. The temperature of the blackbody component also decreased, starting from ~80 keV, and the decay showed a significant break after ~2 s. The spectrum provides strong constraints on the standard synchrotron model, indicating that alternative mechanisms may give rise to the emission at these energies.« less

NuSTAR Observations of the Magnetar 1E 2259+586

NASA Technical Reports Server (NTRS)

Vogel, Julia K.; Hascoet, Romain; Kaspi, Victoria M.; An, Hongjun; Archibald, Robert; Beloborodov, Andrei M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Gotthelf, Eric V.;

A Simple Geometrical Model for Calculation of the Effective Emissivity in Blackbody Cylindrical Cavities

NASA Astrophysics Data System (ADS)

De Lucas, Javier

2015-03-01

A simple geometrical model for calculating the effective emissivity in blackbody cylindrical cavities has been developed. The back ray tracing technique and the Monte Carlo method have been employed, making use of a suitable set of coordinates and auxiliary planes. In these planes, the trajectories of individual photons in the successive reflections between the cavity points are followed in detail. The theoretical model is implemented by using simple numerical tools, programmed in Microsoft Visual Basic for Application and Excel. The algorithm is applied to isothermal and non-isothermal diffuse cylindrical cavities with a lid; however, the basic geometrical structure can be generalized to a cylindro-conical shape and specular reflection. Additionally, the numerical algorithm and the program source code can be used, with minor changes, for determining the distribution of the cavity points, where photon absorption takes place. This distribution could be applied to the study of the influence of thermal gradients on the effective emissivity profiles, for example. Validation is performed by analyzing the convergence of the Monte Carlo method as a function of the number of trials and by comparison with published results of different authors.

An Empirical Fitting Method for Type Ia Supernova Light Curves: A Case Study of SN 2011fe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, WeiKang; Filippenko, Alexei V., E-mail: zwk@astro.berkeley.edu

We present a new empirical fitting method for the optical light curves of Type Ia supernovae (SNe Ia). We find that a variant broken-power-law function provides a good fit, with the simple assumption that the optical emission is approximately the blackbody emission of the expanding fireball. This function is mathematically analytic and is derived directly from the photospheric velocity evolution. When deriving the function, we assume that both the blackbody temperature and photospheric velocity are constant, but the final function is able to accommodate these changes during the fitting procedure. Applying it to the case study of SN 2011fe givesmore » a surprisingly good fit that can describe the light curves from the first-light time to a few weeks after peak brightness, as well as over a large range of fluxes (∼5 mag, and even ∼7 mag in the g band). Since SNe Ia share similar light-curve shapes, this fitting method has the potential to fit most other SNe Ia and characterize their properties in large statistical samples such as those already gathered and in the near future as new facilities become available.« less

Laser and solar-photovoltaic space power systems comparison. II.

NASA Technical Reports Server (NTRS)

De Young, R. J.; Stripling, J.; Enderson, T. M.; Humes, D. H.; Davis, W. T.

1984-01-01

A comparison of total system cost is made between solar photovoltaic and laser/receiver systems. The laser systems assume either a solar-pumped CO2 blackbody transfer laser with MHD receiver or a solar pumped liquid neodymium laser with a photovoltaic receiver. Total system costs are less for the laser systems below 300 km where drag is significant. System costs are highly dependent on altitude.

Arctic Clouds Infrared Imaging Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaw, J. A.

2016-03-01

The Infrared Cloud Imager (ICI), a passive thermal imaging system, was deployed at the North Slope of Alaska site in Barrow, Alaska, from July 2012 to July 2014 for measuring spatial-temporal cloud statistics. Thermal imaging of the sky from the ground provides high radiometric contrast during night and polar winter when visible sensors and downward-viewing thermal sensors experience low contrast. In addition to demonstrating successful operation in the Arctic for an extended period and providing data for Arctic cloud studies, a primary objective of this deployment was to validate novel instrument calibration algorithms that will allow more compact ICI instrumentsmore » to be deployed without the added expense, weight, size, and operational difficulty of a large-aperture onboard blackbody calibration source. This objective was successfully completed with a comparison of the two-year data set calibrated with and without the onboard blackbody. The two different calibration methods produced daily-average cloud amount data sets with correlation coefficient = 0.99, mean difference = 0.0029 (i.e., 0.29% cloudiness), and a difference standard deviation = 0.054. Finally, the ICI instrument generally detected more thin clouds than reported by other ARM cloud products available as of late 2015.« less

Bulk Comptonization: new hints from the luminous blazar 4C+25.05

NASA Astrophysics Data System (ADS)

Kammoun, E. S.; Nardini, E.; Risaliti, G.; Ghisellini, G.; Behar, E.; Celotti, A.

2018-01-01

Blazars are often characterized by a spectral break at soft X-rays, whose origin is still debated. While most sources show a flattening, some exhibit a blackbody-like soft excess with temperatures of the order of ∼0.1 keV, similar to low-luminosity, non-jetted Seyferts. Here, we present the analysis of the simultaneous XMM-Newton and NuSTAR observations of the luminous flat-spectrum radio quasar 4C+25.05 (z = 2.368). The observed 0.3-30 keV spectrum is best described by the sum of a hard X-ray power law (Γ = 1.38_{-0.03}^{+0.05}) and a soft component, approximated by a blackbody with kT_BB = 0.66_{-0.04}^{+0.05} keV (rest frame). If the spectrum of 4C+25.05 is interpreted in the context of bulk Comptonization by cold electrons of broad-line region photons emitted in the direction of the jet, such an unusual temperature implies a bulk Lorentz factor of the jet of Γbulk ∼ 11.7. Bulk Comptonization is expected to be ubiquitous on physical grounds, yet no clear signature of it has been found so far, possibly due to its transient nature and the lack of high-quality, broad-band X-ray spectra.

Sub-MeV band observation of a hard burst from AXP 1E 1547.0-5408 with the Suzaku Wide-band All-sky Monitor

NASA Astrophysics Data System (ADS)

Yasuda, Tetsuya; Iwakiri, Wataru B.; Tashiro, Makoto S.; Terada, Yukikatsu; Kouzu, Tomomi; Enoto, Teruaki; Nakagawa, Yujin E.; Bamba, Aya; Urata, Yuji; Yamaoka, Kazutaka; Ohno, Masanori; Shibata, Shinpei; Makishima, Kazuo

2015-06-01

The 2.1-s anomalous X-ray pulsar 1E 1547.0-5408 exhibited an X-ray outburst on 2009 January 22, emitting a large number of short bursts. The wide-band all-sky monitor (WAM) on-board Suzaku detected at least 254 bursts in the 160 keV-6.2 MeV band over the period of January 22 00:57-17:02 UT from the direction of 1E 1547.0-5408. One of these bursts, which occurred at 06:45:13, produced the brightest fluence in the 0.5-6.2 MeV range, with an averaged 0.16-6.2 MeV flux and extrapolated 25 keV-2 MeV fluence of about 1 × 10-5 erg cm-2 s-1 and about 3 × 10-4 erg cm-2, respectively. After pile-up corrections, the time-resolved WAM spectra of this burst were well-fitted in the 0.16-6.2 MeV range by two-component models; specifically, a blackbody plus an optically thin thermal bremsstrahlung or a combination of a blackbody and a power-law component with an exponential cut-off. These results are compared with previous works reporting the persistent emission and weaker short bursts followed by the same outburst.

Dark Kinetic Heating of Neutron Stars and an Infrared Window on WIMPs, SIMPs, and Pure Higgsinos

NASA Astrophysics Data System (ADS)

Baryakhtar, Masha; Bramante, Joseph; Li, Shirley Weishi; Linden, Tim; Raj, Nirmal

2017-09-01

We identify a largely model-independent signature of dark matter (DM) interactions with nucleons and electrons. DM in the local galactic halo, gravitationally accelerated to over half the speed of light, scatters against and deposits kinetic energy into neutron stars, heating them to infrared blackbody temperatures. The resulting radiation could potentially be detected by the James Webb Space Telescope, the Thirty Meter Telescope, or the European Extremely Large Telescope. This mechanism also produces optical emission from neutron stars in the galactic bulge, and x-ray emission near the galactic center because dark matter is denser in these regions. For GeV-PeV mass dark matter, dark kinetic heating would initially unmask any spin-independent or spin-dependent dark matter-nucleon cross sections exceeding 2 ×10-45 cm2, with improved sensitivity after more telescope exposure. For lighter-than-GeV dark matter, cross-section sensitivity scales inversely with dark matter mass because of Pauli blocking; for heavier-than-PeV dark matter, it scales linearly with mass as a result of needing multiple scatters for capture. Future observations of dark sector-warmed neutron stars could determine whether dark matter annihilates in or only kinetically heats neutron stars. Because inelastic interstate transitions of up to a few GeV would occur in relativistic scattering against nucleons, elusive inelastic dark matter like pure Higgsinos can also be discovered.

Method calibration of the model 13145 infrared target projectors

NASA Astrophysics Data System (ADS)

Huang, Jianxia; Gao, Yuan; Han, Ying

2014-11-01

The SBIR Model 13145 Infrared Target Projectors ( The following abbreviation Evaluation Unit ) used for characterizing the performances of infrared imaging system. Test items: SiTF, MTF, NETD, MRTD, MDTD, NPS. Infrared target projectors includes two area blackbodies, a 12 position target wheel, all reflective collimator. It provide high spatial frequency differential targets, Precision differential targets imaged by infrared imaging system. And by photoelectricity convert on simulate signal or digital signal. Applications software (IR Windows TM 2001) evaluate characterizing the performances of infrared imaging system. With regards to as a whole calibration, first differently calibration for distributed component , According to calibration specification for area blackbody to calibration area blackbody, by means of to amend error factor to calibration of all reflective collimator, radiance calibration of an infrared target projectors using the SR5000 spectral radiometer, and to analyze systematic error. With regards to as parameter of infrared imaging system, need to integrate evaluation method. According to regulation with -GJB2340-1995 General specification for military thermal imaging sets -testing parameters of infrared imaging system, the results compare with results from Optical Calibration Testing Laboratory . As a goal to real calibration performances of the Evaluation Unit.

Insights from Synthetic Star-forming Regions. II. Verifying Dust Surface Density, Dust Temperature, and Gas Mass Measurements With Modified Blackbody Fitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koepferl, Christine M.; Robitaille, Thomas P.; Dale, James E., E-mail: koepferl@usm.lmu.de

We use a large data set of realistic synthetic observations (produced in Paper I of this series) to assess how observational techniques affect the measurement physical properties of star-forming regions. In this part of the series (Paper II), we explore the reliability of the measured total gas mass, dust surface density and dust temperature maps derived from modified blackbody fitting of synthetic Herschel observations. We find from our pixel-by-pixel analysis of the measured dust surface density and dust temperature a worrisome error spread especially close to star formation sites and low-density regions, where for those “contaminated” pixels the surface densitiesmore » can be under/overestimated by up to three orders of magnitude. In light of this, we recommend to treat the pixel-based results from this technique with caution in regions with active star formation. In regions of high background typical in the inner Galactic plane, we are not able to recover reliable surface density maps of individual synthetic regions, since low-mass regions are lost in the far-infrared background. When measuring the total gas mass of regions in moderate background, we find that modified blackbody fitting works well (absolute error: + 9%; −13%) up to 10 kpc distance (errors increase with distance). Commonly, the initial images are convolved to the largest common beam-size, which smears contaminated pixels over large areas. The resulting information loss makes this commonly used technique less verifiable as now χ {sup 2} values cannot be used as a quality indicator of a fitted pixel. Our control measurements of the total gas mass (without the step of convolution to the largest common beam size) produce similar results (absolute error: +20%; −7%) while having much lower median errors especially for the high-mass stellar feedback phase. In upcoming papers (Paper III; Paper IV) of this series we test the reliability of measured star formation rate with direct and indirect techniques.« less

Exploring Near-Field Radiative Heat Transfer for Thermo-photovoltaic Applications

NASA Astrophysics Data System (ADS)

Ganjeh, Yashar; Song, Bai; Sadat, Seid; Thompson, Dakotah; Fiorino, Anthony; Reddy, Pramod; Meyhofer, Edgar

2014-03-01

Understanding near-field radiative heat transfer (NFRHT) is critical for developing efficient thermo-photovoltaic devices. Theoretical predictions suggest that when the spatial separation of two parallel planes at different temperatures is less than their Wien's thermal wavelength, thermal transport via radiation can be greatly enhanced. The radiative heat flow across nanoscale gaps is predicted to be orders-of-magnitude higher than that given by Stefan-Boltzmann law, due to contribution of evanescent waves. In order to test these predictions, a novel experimental platform was designed and built enabling parallelization of two planar surfaces (50 μm by 50 μm) with 500 microradian resolution in their relative orientation. This platform was used to probe NFRHT between two planes and also between a plane and a sphere. It was found that, when a 50 μm diameter silica sphere was approximately 20 nm away from a 50 by 50 μm2 silica plane, a significant increase in radiative heat transfer coefficient was observed. This increase is 3 orders of magnitude higher than the value predicted by the blackbody limit. Other setups, including Au spheres and planes, and the plane-plane geometries are currently being investigated. 1) Army Research office (W911NF-12-1-0612), 2) NSF Thermal Transport Prcesses (CBET 1235691), 3) Center for Solar and Thermal Energy conversion, funded by the US Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0000957.

Towards an Understanding of Radiative Factors on Planetary Rings: a Perspective from Cassini CIRS Observations at Saturn Equinox

NASA Astrophysics Data System (ADS)

Brooks, Shawn M.; Spilker, L.; Edgington, S. G.; Déau, E.; Pilorz, S. H.

2012-10-01

Since arriving at Saturn in 2004, Cassini's Composite Infrared Spectrometer has recorded tens of millions of spectra of Saturn’s rings (personal communication, M. Segura). CIRS records far infrared radiation (16.7-1000 microns) at focal plane 1 (FP1). Thermal emission from Saturn’s rings peaks at FP1 wavelengths. CIRS spectra are well characterized as blackbody emission at an effective temperature Te, multiplied by a scalar factor related to ring emissivity (Spilker et al. [2005, 2006]). CIRS can therefore characterize the rings' temperature and study the thermal environment to which the ring particles are subject. We focus on CIRS data from the 2009 Saturnian equinox. As the Sun's disk crossed the ring plane, CIRS obtained several radial scans of the rings at a variety of phase angles, local hour angles and distances. With the Sun's rays striking the rings at an incidence angle of zero, solar heating is virtually absent, and thermal radiation from Saturn and sunlight reflected by Saturn dominate the thermal environment. These observations present an apparent paradox. Equinox data show that the flux of thermal energy radiated by the rings is roughly equivalent to or even exceeds the energy incident upon them as prescribed by thermal models (Froidevaux [1981], Ferrari and Leyrat [2006], Morishima et al. [2009, 2010]). This apparent energy excess is largest in the C ring and Cassini Division. Conservation principles suggest that models underestimate heating of the rings, as it is clearly unphysical for the rings to radiate significantly more energy than is incident upon them. In this presentation, we will attempt to resolve this paradox and determine what this can teach us about Saturn's rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2012 California Institute of Technology. Government sponsorship acknowledged.

Observational Appearance and Spectrum of Black-Hole Winds

NASA Astrophysics Data System (ADS)

Fukue, Jun; Iino, Eriko

2010-12-01

We examine the observational appearance of an optically thick, spherically symmetric, relativistic wind (a black-hole wind), focusing our attention on the emerging spectrum. In a relativistic flow, the apparent optical depth becomes small (large) in the downstream (upstream) direction due to the Lorentz-Fitzgerald contraction. As a result, the location of the apparent photosphere of the wind is remarkably modified, and there appears a relativistic limb-darkening (center-brightening) effect, where the comoving temperature distribution of the apparent photosphere is enhanced (reduced) at the center (in the limb). In addition, due to the usual Doppler boost, the observed temperature distribution is greatly changed. These relativistic effects modify the expected spectrum. When the wind speed is subrelativistic, the observed temperature distribution is almost uniform, and the spectra of the black-hole wind are blackbody-like. When the wind speed becomes relativistic, on the other hand, the observed temperature distribution, Tobs, exhibits a power-law nature of Tobs ∝ r-1, where r is the distance from the disk center, and the observed spectra Sν become a modified blackbody, which has a power-law part of Sν ∝ ν, where ν is the frequency. We briefly examine the effects of the spatial variation of the wind speed and the mass-loss rate.

Time-dependent disk accretion in X-ray Nova MUSCAE 1991

NASA Astrophysics Data System (ADS)

Mineshige, Shin; Hirano, Akira; Kitamoto, Shunji; Yamada, Tatsuya T.; Fukue, Jun

1994-05-01

We propose a new model for X-ray spectral fitting of binary black hole candidates. In this model, it is assumed that X-ray spectra are composed of a Comptonized blackbody (hard component) and a disk blackbody spectra (soft component), in which the temperature gradient of the disk, q identically equal to -d log T/d log r, is left as a fitting parameter. With this model, we have fitted X-ray spectra of X-ray Nova Muscae 1991 obtained by Ginga. The fitting shows that a hot cloud, which Compton up-scatters soft photons from the disk, gradually shrank and became transparent after the main peak. The temperature gradient turns out to be fairly constant and is q approximately 0.75, the value expected for a Newtonian disk model. To reproduce this value with a relativistic disk model, a small inclination angle, i approximately equal to 0 deg to 15 deg, is required. It seems, however, that the q-value temporarily decreased below 0.75 at the main flare, and q increased in a transient fashion at the second peak (or the reflare) occurring approximately 70 days after the main peak. Although statistics are poor, these results, if real, would indicate that the disk brightening responsible for the main and secondary peaks are initiated in the relatively inner portions of the disk.

NuSTAR Observations of X-Ray Bursts from the Magnetar 1E 1048.1-5937

NASA Technical Reports Server (NTRS)

An, Hongjun; Kaspi, Victoria M.; Beloborodov, Andrei M.; Kouveliotou, Chryssa; Archibald, Robert T.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Gotthelf, Eric V.; Stern, Daniel;

High light-quality OLEDs with a wet-processed single emissive layer.

PubMed

Singh, Meenu; Jou, Jwo-Huei; Sahoo, Snehasis; S S, Sujith; He, Zhe-Kai; Krucaite, Gintare; Grigalevicius, Saulius; Wang, Ching-Wu

2018-05-08

High light-quality and low color temperature are crucial to justify a comfortable healthy illumination. Wet-process enables electronic devices cost-effective fabrication feasibility. We present herein low color temperature, blue-emission hazards free organic light emitting diodes (OLEDs) with very-high light-quality indices, that with a single emissive layer spin-coated with multiple blackbody-radiation complementary dyes, namely deep-red, yellow, green and sky-blue. Specifically, an OLED with a 1,854 K color temperature showed a color rendering index (CRI) of 90 and a spectrum resemblance index (SRI) of 88, whose melatonin suppression sensitivity is only 3% relative to a reference blue light of 480 nm. Its maximum retina permissible exposure limit is 3,454 seconds at 100 lx, 11, 10 and 6 times longer and safer than the counterparts of compact fluorescent lamp (5,920 K), light emitting diode (5,500 K) and OLED (5,000 K). By incorporating a co-host, tris(4-carbazoyl-9-ylphenyl)amine (TCTA), the resulting OLED showed a current efficiency of 24.9 cd/A and an external quantum efficiency of 24.5% at 100 cd/m 2 . It exhibited ultra-high light quality with a CRI of 93 and an SRI of 92. These prove blue-hazard free, high quality and healthy OLED to be fabrication feasible via the easy-to-apply wet-processed single emissive layer with multiple emitters.

Big Bang Titanic: New Dark Energy (Vacuum Gravity) Cosmic Model Emerges Upon Falsification of The Big Bang By Disproof of Its Central Assumptions

NASA Astrophysics Data System (ADS)

Gentry, Robert

2011-04-01

Physicists who identify the big bang with the early universe should have first noted from Hawking's A Brief History of Time, p. 42, that he ties Hubble's law to Doppler shifts from galaxy recession from a nearby center, not to bb's unvalidated and thus problematical expansion redshifts. Our PRL submission LJ12135 describes such a model, but in it Hubble's law is due to Doppler and vacuum gravity effects, the 2.73K CBR is vacuum gravity shifted blackbody cavity radiation from an outer galactic shell, and its (1 + z)-1 dilation and (M,z) relations closely fit high-z SNe Ia data; all this strongly implies our model's vacuum energy is the elusive dark energy. We also find GPS operation's GR effects falsify big bang's in-flight expansion redshift paradigm, and hence the big bang, by showing λ changes occur only at emission. Surprisingly we also discover big bang's CBR prediction is T < 2x10-8 K, not the observed 2.73K. So instead of the 2.73K affirming the big bang as cosmologists claim, it actually disproves it, to which the DAE's response is most enigmatic -- namely, CBR photons expand dλ/dt > 0, while galactic photons shrink dλ/dt < 0. Contrary to a PRL editor's claim, the above results show LJ12135 fits PRL guidelines for papers that replace established theories. For details see alphacosmos.net.

Improved calibration-based non-uniformity correction method for uncooled infrared camera

NASA Astrophysics Data System (ADS)

Liu, Chengwei; Sui, Xiubao

2017-08-01

With the latest improvements of microbolometer focal plane arrays (FPA), uncooled infrared (IR) cameras are becoming the most widely used devices in thermography, especially in handheld devices. However the influences derived from changing ambient condition and the non-uniform response of the sensors make it more difficult to correct the nonuniformity of uncooled infrared camera. In this paper, based on the infrared radiation characteristic in the TEC-less uncooled infrared camera, a novel model was proposed for calibration-based non-uniformity correction (NUC). In this model, we introduce the FPA temperature, together with the responses of microbolometer under different ambient temperature to calculate the correction parameters. Based on the proposed model, we can work out the correction parameters with the calibration measurements under controlled ambient condition and uniform blackbody. All correction parameters can be determined after the calibration process and then be used to correct the non-uniformity of the infrared camera in real time. This paper presents the detail of the compensation procedure and the performance of the proposed calibration-based non-uniformity correction method. And our method was evaluated on realistic IR images obtained by a 384x288 pixels uncooled long wave infrared (LWIR) camera operated under changed ambient condition. The results show that our method can exclude the influence caused by the changed ambient condition, and ensure that the infrared camera has a stable performance.

Dark Kinetic Heating of Neutron Stars and an Infrared Window on WIMPs, SIMPs, and Pure Higgsinos.

PubMed

Baryakhtar, Masha; Bramante, Joseph; Li, Shirley Weishi; Linden, Tim; Raj, Nirmal

2017-09-29

We identify a largely model-independent signature of dark matter (DM) interactions with nucleons and electrons. DM in the local galactic halo, gravitationally accelerated to over half the speed of light, scatters against and deposits kinetic energy into neutron stars, heating them to infrared blackbody temperatures. The resulting radiation could potentially be detected by the James Webb Space Telescope, the Thirty Meter Telescope, or the European Extremely Large Telescope. This mechanism also produces optical emission from neutron stars in the galactic bulge, and x-ray emission near the galactic center because dark matter is denser in these regions. For GeV-PeV mass dark matter, dark kinetic heating would initially unmask any spin-independent or spin-dependent dark matter-nucleon cross sections exceeding 2×10^{-45}  cm^{2}, with improved sensitivity after more telescope exposure. For lighter-than-GeV dark matter, cross-section sensitivity scales inversely with dark matter mass because of Pauli blocking; for heavier-than-PeV dark matter, it scales linearly with mass as a result of needing multiple scatters for capture. Future observations of dark sector-warmed neutron stars could determine whether dark matter annihilates in or only kinetically heats neutron stars. Because inelastic interstate transitions of up to a few GeV would occur in relativistic scattering against nucleons, elusive inelastic dark matter like pure Higgsinos can also be discovered.

Recent solar extreme ultraviolet irradiance observations and modeling: A review

NASA Technical Reports Server (NTRS)

Tobiska, W. Kent

1993-01-01

For more than 90 years, solar extreme ultraviolet (EUV) irradiance modeling has progressed from empirical blackbody radiation formulations, through fudge factors, to typically measured irradiances and reference spectra was well as time-dependent empirical models representing continua and line emissions. A summary of recent EUV measurements by five rockets and three satellites during the 1980s is presented along with the major modeling efforts. The most significant reference spectra are reviewed and threee independently derived empirical models are described. These include Hinteregger's 1981 SERF1, Nusinov's 1984 two-component, and Tobiska's 1990/1991/SERF2/EUV91 flux models. They each provide daily full-disk broad spectrum flux values from 2 to 105 nm at 1 AU. All the models depend to one degree or another on the long time series of the Atmosphere Explorer E (AE-E) EUV database. Each model uses ground- and/or space-based proxies to create emissions from solar atmospheric regions. Future challenges in EUV modeling are summarized including the basic requirements of models, the task of incorporating new observations and theory into the models, the task of comparing models with solar-terrestrial data sets, and long-term goals and modeling objectives. By the late 1990s, empirical models will potentially be improved through the use of proposed solar EUV irradiance measurements and images at selected wavelengths that will greatly enhance modeling and predictive capabilities.

Optical excess of dim isolated neutron stars

NASA Astrophysics Data System (ADS)

Ertan, Ü.; Çalışkan, Ş.; Alpar, M. A.

2017-09-01

The optical excess in the spectra of dim isolated neutron stars (XDINs) is a significant fraction of their rotational energy loss rate. This is strikingly different from the situation in isolated radio pulsars. We investigate this problem in the framework of the fallback disc model. The optical spectra can be powered by magnetic stresses on the innermost disc matter, as the energy dissipated is emitted as blackbody radiation mainly from the inner rim of the disc. In the fallback disc model, XDINs are the sources evolving in the propeller phase with similar torque mechanisms. In this model, the ratio of the total magnetic work that heats up the inner disc matter is expected to be similar for different XDINs. Optical luminosities that are calculated consistently with the optical spectra and the theoretical constraints on the inner disc radii give very similar ratios of the optical luminosity to the rotational energy loss rate for all these sources. These ratios indicate that a significant fraction of the magnetic torque heats up the disc matter while the remaining fraction expels disc matter from the system. For XDINs, the contribution of heating by X-ray irradiation to the optical luminosity is negligible in comparison with the magnetic heating. The correlation we expect between the optical luminosities and the rotational energy loss rates of XDINs can be a property of the systems with low X-ray luminosities, in particular those in the propeller phase.

Glossary | Efficient Windows Collaborative

Science.gov Websites

double-hung windows as a means of counterbalancing the weight of the sash during opening and closing. Bay a fixed sash or a double-hung window. Also referred to as bead stop. Blackbody. The ideal, perfect member of the lower sash which meet at the middle of a double-hung window. Clerestory. A window in the

CONTINUUM ENHANCEMENTS IN THE ULTRAVIOLET, THE VISIBLE AND THE INFRARED DURING THE X1 FLARE ON 2014 MARCH 29

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleint, Lucia; Krucker, Säm; Heinzel, Petr

2016-01-10

Enhanced continuum brightness is observed in many flares (“white light flares”), yet it is still unclear which processes contribute to the emission. To understand the transport of energy needed to account for this emission, we must first identify both the emission processes and the emission source regions. Possibilities include heating in the chromosphere causing optically thin or thick emission from free-bound transitions of Hydrogen, and heating of the photosphere causing enhanced H{sup −} continuum brightness. To investigate these possibilities, we combine observations from Interface Region Imaging Spectrograph (IRIS), SDO/Helioseismic and Magnetic Imager, and the ground-based Facility Infrared Spectrometer instrument, coveringmore » wavelengths in the far-UV, near-UV (NUV), visible, and infrared during the X1 flare SOL20140329T17:48. Fits of blackbody spectra to infrared and visible wavelengths are reasonable, yielding radiation temperatures ∼6000–6300 K. The NUV emission, formed in the upper photosphere under undisturbed conditions, exceeds these simple fits during the flare, requiring extra emission from the Balmer continuum in the chromosphere. Thus, the continuum originates from enhanced radiation from photosphere (visible-IR) and chromosphere (NUV). From the standard thick-target flare model, we calculate the energy of the nonthermal electrons observed by Reuven Ramaty High Energy Solar Spectroscope Imager (RHESSI) and compare it to the energy radiated by the continuum emission. We find that the energy contained in most electrons >40 keV, or alternatively, of ∼10%–20% of electrons >20 keV is sufficient to explain the extra continuum emission of ∼(4–8) × 10{sup 10} erg s{sup −1} cm{sup −2}. Also, from the timing of the RHESSI HXR and the IRIS observations, we conclude that the NUV continuum is emitted nearly instantaneously when HXR emission is observed with a time difference of no more than 15 s.« less

A Novel Miniature Wide-band Radiometer for Space Applications

NASA Astrophysics Data System (ADS)

Sykulska-Lawrence, H. M.

2016-12-01

Design, development and testing of a novel miniaturised infrared radiometer is described. The instrument opens up new possibilities in planetary science of deployment on smaller platforms - such as unmanned aerial vehicles and microprobes - to enable study of a planet's radiation balance, as well as terrestrial volcano plumes and trace gases in planetary atmospheres, using low-cost long-term observations. Thus a key enabling development is that of miniaturised, low-power and well-calibrated instrumentation. The talk reports advances in miniature technology to perform high accuracy visible / IR remote sensing measurements. The infrared radiometer is akin to those widely used for remote sensing for earth and space applications, which are currently either large instruments on orbiting platforms or medium-sized payloads on balloons. We use MEMS microfabrication techniques to shrink a conventional design, while combining the calibration benefits of large (>1kg) type radiometers with the flexibility and portability of a <10g device. The instrument measures broadband (0.2 to 100µm) upward and downward radiation fluxes, showing improvements in calibration stability and accuracy,with built-in calibration capability, incorporating traceability to temperature standards such as ITS-90. The miniature instrument described here was derived from a concept developed for a European Space Agency study, Dalomis (Proc. of 'i-SAIRAS 2005', Munich, 2005), which involved dropping multiple probes into the atmosphere of Venus from a balloon to sample numerous parts of the complex weather systems on the planet. Data from such an in-situ instrument would complement information from a satellite remote sensing instrument or balloon radiosonde. Moreover, the addition of an internal calibration standard facilitates comparisons between datasets. One of the main challenges for a reduced size device is calibration. We use an in-situ method whereby a blackbody source is integrated within the device and a micromirror switches the input to the detector between the measured signal and the calibration target. Achieving two well-calibrated radiometer channels within a small (<10g) payload is made possible by using modern micromachining techniques.

A Novel Miniature Wide-band Radiometer for Space Applications

NASA Astrophysics Data System (ADS)

Sykulska-Lawrence, Hanna

2016-10-01

Design, development and testing of a novel miniaturised infrared radiometer is described. The instrument opens up new possibilities in planetary science of deployment on smaller platforms - such as unmanned aerial vehicles and microprobes - to enable study of a planet's radiation balance, as well as terrestrial volcano plumes and trace gases in planetary atmospheres, using low-cost long-term observations. Thus a key enabling development is that of miniaturised, low-power and well-calibrated instrumentation.The paper reports advances in miniature technology to perform high accuracy visible / IR remote sensing measurements. The infrared radiometer is akin to those widely used for remote sensing for earth and space applications, which are currently either large instruments on orbiting platforms or medium-sized payloads on balloons. We use MEMS microfabrication techniques to shrink a conventional design, while combining the calibration benefits of large (>1kg) type radiometers with the flexibility and portability of a <10g device. The instrument measures broadband (0.2 to 100um) upward and downward radiation fluxes, with built-in calibration capability, incorporating traceability to temperature standards such as ITS-90.The miniature instrument described here was derived from a concept developed for a European Space Agency study, Dalomis (Proc. of 'i-SAIRAS 2005', Munich, 2005), which involved dropping multiple probes into the atmosphere of Venus from a balloon to sample numerous parts of the complex weather systems on the planet. Data from such an in-situ instrument would complement information from a satellite remote sensing instrument or balloon radiosonde. Moreover, the addition of an internal calibration standard facilitates comparisons between datasets.One of the main challenges for a reduced size device is calibration. We use an in-situ method whereby a blackbody source is integrated within the device and a micromirror switches the input to the detector between the measured signal and the calibration target. Achieving two well-calibrated radiometer channels within a small (<10g) payload is made possible by using micromachining techniques.

Incorporating realistic surface longwave spectral emissivity in the CESM and the impact on simulated current climate and climate changes

NASA Astrophysics Data System (ADS)

Chen, X.; Huang, X.; Flanner, M.; Yang, P.; Feldman, D.; Kuo, C.

2016-12-01

As of today, most state-of-the-art GCMs still assumes blackbody surface in their longwave radiation scheme. Recent works by Chen et al. (2014) and Feldman et al. (2014) have suggested that the surface spectral emissivity can impact the simulated radiation budget and climate change in a discernible way, especially in high latitudes. Using a recently developed global emissivity database that covers both far-IR and mid-IR, we incorporated the LW surface spectral emissivity into the radiation scheme of the CESM. Effort has been made to ensure a consistent treatment of surface upward LW broadband flux in both the land module and the atmospheric module of the CESM, an important aspect overlooked by the previous study. Then we assess impacts of the inclusion of surface spectral emissivity on simulated mean-state climate and climate changes by carrying out two sets of parallel runs. The first pair of experiments uses the standard slab-ocean CESM v1.1.1 to run two experiments: one control run using forcings at year 2000 level and one sensitivity run abruptly doubling the CO2. The second pair of experiment setup is identical to the first one but using the CESM that we have modified (Surface emissivity is a prognostic variable in our second pair of experiments). The current climate simulation results show that the Sahara desert region in the modified CESM has a warmer surface temperature than in the standard CESM by 2-3K. Over the high-latitude regions, the modified CESM tends to have a colder surface temperature than the standard CESM by 1-2.5K. As a result, the climatological sea ice coverage in the modified CESM is 8% more than it in the standard CESM in both Polar Regions. All these differences are statistically significant. As for simulated climate change in response to a doubling of CO2, the Arctic region in the modified CESM warms consistently faster than in the standard CESM by 1-2K while the Antarctic region shows a non-uniform pattern of differences between two models. Differences in the changes of sea ice coverage between two models show a zonally-uniform dipole pattern over both polar oceans. The reasons for such differences and its linkage with the change of surface spectral emissivity are further explained.

Selective emission and luminescence of Er{sub 2}O{sub 3} under intense laser excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marchenko, V M; Studenikin, M I; Iskhakova, L D

2013-09-30

The microstructure of Er{sub 2}O{sub 3} polycrystals synthesised by laser heating is studied. The synthesis of erbium silicate (Er{sub 2}SiO{sub 5}) layers was observed upon interaction of Er{sub 2}O{sub 3} and SiO{sub 2} melts. The dependences of the selective emission (SE) and luminescence spectra of Er{sub 2}O{sub 3} polycrystals in the range 200 – 1700 nm on the intensity of laser-thermal (at the wavelength λ = 10.6 μm) and resonant laser (λ ≈ 975 nm) excitation are investigated. The emission of heated Er{sub 2}O{sub 3} polycrystals arises as a result of multiphonon relaxation of absorbed energy and is a superpositionmore » of the SE at the electronic-vibrational transitions of Er{sup 3+} ions and the thermal radiation of the crystal lattice. The shape of the SE spectra of Er{sub 2}O{sub 3} polycrystals in the range 400 – 1700 nm almost does not change upon laser-thermal heating from 300 to 1500 K and subsequent cooling and corresponds to the absorption spectra of Er{sup 3+} ions. With increasing temperature, the thermal radiation intensity increases faster than the SE intensity, and the shape of the Er{sub 2}O{sub 3} spectrum becomes closer to the calculated spectrum of a blackbody. The anti-Stokes luminescence spectra of Er{sup 3+} ions formed under intense laser excitation of the {sup 4}I{sub 11/2} level are explained by additional SE caused by heating of the crystal matrix due to the Stokes losses. A difference between the SE and luminescence spectra is observed at low intensities of resonant laser excitation and low temperatures, when only the Stokes luminescence occurs. The temperature dependences of the SE and luminescence spectra of Er{sub 2}O{sub 3} upon laser excitation testify to the fundamental role played by the interaction of the electronic f-shell of Er{sup 3+} ions with crystal lattice vibrations in the processes of multiphonon radiative and nonradiative relaxation. The laser-thermal synthesis is promising for inprocess variation of the chemical composition of rare-earth samples. (interaction of laser radiation with matter)« less

The Multiple Continuum Components in the White-Light Flare of 16 January 2009 on the dM4.5e Star YZ CMi

NASA Astrophysics Data System (ADS)

Kowalski, A. F.; Hawley, S. L.; Holtzman, J. A.; Wisniewski, J. P.; Hilton, E. J.

2012-03-01

The white light during M dwarf flares has long been known to exhibit the broadband shape of a T≈10 000 K blackbody, and the white light in solar-flares is thought to arise primarily from hydrogen recombination. Yet, a current lack of broad-wavelength coverage solar flare spectra in the optical/near-UV region prohibits a direct comparison of the continuum properties to determine if they are indeed so different. New spectroscopic observations of a secondary flare during the decay of a megaflare on the dM4.5e star YZ CMi have revealed multiple components in the white-light continuum of stellar flares, including both a blackbody-like spectrum and a hydrogen-recombination spectrum. One of the most surprising findings is that these two components are anti-correlated in their temporal evolution. We combine initial phenomenological modeling of the continuum components with spectra from radiative hydrodynamic models to show that continuum veiling causes the measured anti-correlation. This modeling allows us to use the components' inferred properties to predict how a similar spatially resolved, multiple-component, white-light continuum might appear using analogies to several solar-flare phenomena. We also compare the properties of the optical stellar flare white light to Ellerman bombs on the Sun.

The near-infrared broad emission line region of active galactic nuclei - II. The 1-μm continuum

NASA Astrophysics Data System (ADS)

Landt, Hermine; Elvis, Martin; Ward, Martin J.; Bentz, Misty C.; Korista, Kirk T.; Karovska, Margarita

2011-06-01

We use quasi-simultaneous near-infrared (near-IR) and optical spectroscopy from four observing runs to study the continuum around 1 μm in 23 well-known broad emission line active galactic nuclei (AGN). We show that, after correcting the optical spectra for host galaxy light, the AGN continuum around this wavelength can be approximated by the sum of mainly two emission components, a hot dust blackbody and an accretion disc. The accretion disc spectrum appears to dominate the flux at ˜ 1 μm, which allows us to derive a relation for estimating AGN black hole masses based on the near-IR virial product. This result also means that a near-IR reverberation programme can determine the AGN state independent of simultaneous optical spectroscopy. On average we derive hot dust blackbody temperatures of ˜1400 K, a value close to the sublimation temperature of silicate dust grains, and relatively low hot dust covering factors of ˜7 per cent. Our preliminary variability studies indicate that in most sources, the hot dust emission responds to changes in the accretion disc flux with the expected time lag; however, a few sources show a behaviour that can be attributed to dust destruction.

High-energy non-thermal and thermal emission from GRB 141207A detected by Fermi

DOE PAGES

Arimoto, Makoto; Asano, Katsuaki; Ohno, Masanori; ...

2016-12-13

A bright long gamma-ray burst GRB 141207A was observed by the Fermi Gamma-ray Space Telescope and detected by both instruments onboard. The observations show that the spectrum in the prompt phase is not well described by the canonical empirical Band function alone, and that an additional power-law component is needed. In the early phase of the prompt emission, a modified blackbody with a hard low-energy photon index (α = +0.2 to +0.4) is detected, which suggests a photospheric origin. In a finely time-resolved analysis, the spectra are also well fitted by the modified blackbody combined with a power-law function. Heremore » we discuss the physical parameters of the photosphere such as the bulk Lorentz factor of the relativistic flow and the radius. We also discuss the physical origin of the extra power-law component observed during the prompt phase in the context of different models such as leptonic and hadronic scenarios in the internal shock regime and synchrotron emission in the external forward shock. In the afterglow phase, the temporal and spectral behaviors of the temporally extended high-energy emission and the fading X-ray emission detected by the X-Ray Telescope on-board Swift are consistent with synchrotron emission in a radiative external forward shock.« less

Chandra Low Energy Transmission Grating Spectrum of SS Cygni in Outburst

NASA Astrophysics Data System (ADS)

Mauche, Christopher W.

2004-07-01

We have fitted the Chandra Low Energy Transmission Grating (LETG) spectrum of SS Cygni in outburst with a single-temperature blackbody suffering the photoelectric opacity of a neutral column density and the scattering opacity of an outflowing wind. We find that this simple model is capable of reproducing the essential features of the observed spectrum with the blackbody temperature Tbl~250+/-50 kK, hydrogen column density NH~5.0+2.9-1.5×1019cm-2, fractional emitting area f~5.6+60-4.5×10-3, boundary layer luminosity Lbl~5+18-3×1033ergss-1, wind velocity v~2500kms-1, wind mass-loss rate Mw~1.1×1016gs-1, and arbitrary values of the wind ionization fractions of 20 ions of O, Ne, Mg, Si, S, and Fe. Given that in outburst the accretion disk luminosity Ldisk~1×1035ergss-1, Lbl/Ldisk~0.05+0.18-0.03, which can be explained if the white dwarf (or an equatorial belt thereon) is rotating with an angular velocity Ωwd~0.7+0.1-0.2 Hz, hence Vrotsini~2300kms-1. This paper is dedicated to the memory and accomplishments of my colleague and friend Janet Akyüz Mattei, who died on 2004 March 22 after a long battle with acute myelogenous leukemia. Her passing is a great loss to the astronomical community, both amateur and professional.

SGR 1822-1606 (Swift J1822.3-1606): X-ray spectrum and refined spin period from Swift XRT analysis

NASA Astrophysics Data System (ADS)

Esposito, P.; Rea, N.; Israel, G. L.

2011-07-01

We have analysed 1.6 ks s of Photon Counting (PC) XRT data of the new SGR/magnetar candidate Swift J1822.3-1606 (Cummings et al. GCN #12159), including the first 0.6 ks on which Pagani et al. reported in GCN #12163. We found that the source spectrum is well described by a power-law plus blackbody model, modified for the interstellar absorption (reduced chi-squared = 1.04 for 97 degrees of freedom).

Analysis of Lubricant Films in Bearings Under Incipient Failure Conditions.

DTIC Science & Technology

1981-01-01

AFOSUR. 8 2 -34 0 1 ACEjSN NO. lEN’ CATALOG NUMBERFO"R8 0-0010 4 4. TITLE (and Subtitio) S. TYPE OFf REPORT a PERIOD COVERED "Analysis of Lubricant...spectroscopy of the lubricant in operating heavily loaded bearings under so-called elasto- hydrodynamic lubricating conditions. In this type of...Chopper and Blackbody Reference Both interferometers are equipped with choppers of the tuning fork type shown in Fig. 6. The tines are located in front of

A Proposal to Develop and Test a Fibre-Optic Coupled Solar Thermal Propulsion System for Microsatellites

DTIC Science & Technology

2006-03-01

high numerical aperture fibre optics. Applying fibre optics to STP allows the solar concentrator mirror to be mechanically decoupled from the solar...Applying fibre optics to STP allows the solar concentrator mirror to be mechanically decoupled from the solar heat exchanger as well as granting...concentration is achieved via an optical concentrating system, such as a series of lenses or mirrors . This concentrated sunlight impinges on a blackbody

Recent results from the Japanese X-ray astronomy satellites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Y.

1986-01-01

Observations of neutron stars and their environments, and the emission and absorption of iron, obtained with the Hakucho and Tenma satellites, are examined. The characteristics of X-ray bursts, neutron stars, and accretion disks, in particular spectra, color and effective temperatures, blackbody temperature and radius, the emissivity factor, and the Eddington limit luminosity, are discussed. Consideration is given to the rapid burster discovered by Lewin et al. (1976) and potential blackhole sources. 43 references.

Infrared Data for Storm Analysis

NASA Technical Reports Server (NTRS)

Adler, R.

1982-01-01

The papers in this section include: 1) 'Thunderstorm Top Structure Observed by Aircraft Overflights with an Infrared Radiometer'; 2) 'Thunderstorm Intensity as Determined from Satellite Data'; 3) 'Relation of Satellite-Based Thunderstorm Intensity to Radar-Estimated Rainfall'; 4) 'A Simple Physical Basis for Relating Geosynchronous Satellite Infrared Observations to Thunderstorm Rainfall'; 5) 'Satellite-Observed Cloud-Top Height Changes in Tornadic Thunderstorms'; 6) 'Predicting Tropical Cyclone Intensity Using Satellite-Measured Equivalent Blackbody Temperatures of Cloud Tops'.

The Spectral Results of the FIRAS Instrument on COBE

NASA Technical Reports Server (NTRS)

Fixsen, Dale J.; Mather, John C.

2002-01-01

The Cosmic Microwave Background (CMB) spectral results of the FIRAS instrument are summarized. Some questions that have been raised about the calibration accuracy are also addressed. Finally we comment on the potential for major improvements with new measurement approaches. The measurement of the deviation of the CMB spectrum from a 2.725 plus or minus 0.001 K blackbody form made by the COBE-FIRAS could be improved by two orders of magnitude.

TWO-DIMENSIONAL MAPPING OF YOUNG STARS IN THE INNER 180 pc OF NGC 1068: CORRELATION WITH MOLECULAR GAS RING AND STELLAR KINEMATICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Storchi-Bergmann, Thaisa; Riffel, Rogerio; Vale, Tiberio Borges

We report the first two-dimensional mapping of the stellar population and non-stellar continua within the inner 180 pc (radius) of NGC 1068 at a spatial resolution of 8 pc, using integral field spectroscopy in the near-infrared. We have applied the technique of spectral synthesis to data obtained with the instrument NIFS and the adaptive optics module ALTAIR at the Gemini North Telescope. Two episodes of recent star formation are found to dominate the stellar population contribution: the first occurred 300 Myr ago, extending over most of the nuclear region; the second occurred just 30 Myr ago, in a ring-like structuremore » at Almost-Equal-To 100 pc from the nucleus, where it is coincident with an expanding ring of H{sub 2} emission. Inside the ring, where a decrease in the stellar velocity dispersion is observed, the stellar population is dominated by the 300 Myr age component. In the inner 35 pc, the oldest age component (age {>=} 2 Gyr) dominates the mass, while the flux is dominated by blackbody components with temperatures in the range 700 K {<=} T {<=} 800 K which we attribute to the dusty torus. We also find some contribution from blackbody and power-law components beyond the nucleus which we attribute to dust emission and scattered light.« less

Calibration of VIIRS F1 Sensor Fire Detection Band Using lunar Observations

NASA Technical Reports Server (NTRS)

McIntire, Jeff; Efremova, Boryana; Xiong, Xiaoxiong

2012-01-01

Visible Infrared Imager Radiometer Suite (VIIRS) Fight 1 (Fl) sensor includes a fire detection band at roughly 4 microns. This spectral band has two gain states; fire detection occurs in the low gain state above approximately 345 K. The thermal bands normally utilize an on-board blackbody to provide on-orbit calibration. However, as the maximum temperature of this blackbody is 315 K, the low gain state of the 4 micron band cannot be calibrated in the same manner as the rest of the thermal bands. Regular observations of the moon provide an alternative calibration source. The lunar surface temperature has been recently mapped by the DIVINER sensor on the LRO platform. The periodic on-board high gain calibration along with the DIVINER surface temperatures was used to determine the emissivity and solar reflectance of the lunar surface at 4 microns; these factors and the lunar data are then used to fit the low gain calibration coefficients of the 4 micron band. Furthermore, the emissivity of the lunar surface is well known near 8.5 microns due to the Christiansen feature (an emissivity maximum associated with Si-O stretching vibrations) and the solar reflectance is negligible. Thus, the 8.5 micron band is used for relative calibration with the 4 micron band to de-trend any temporal variations. In addition, the remaining thermal bands are analyzed in a similar fashion, with both calculated emissivities and solar reflectances produced.

Accurate Ray-tracing of Realistic Neutron Star Atmospheres for Constraining Their Parameters

NASA Astrophysics Data System (ADS)

Vincent, Frederic H.; Bejger, Michał; Różańska, Agata; Straub, Odele; Paumard, Thibaut; Fortin, Morgane; Madej, Jerzy; Majczyna, Agnieszka; Gourgoulhon, Eric; Haensel, Paweł; Zdunik, Leszek; Beldycki, Bartosz

2018-03-01

Thermal-dominated X-ray spectra of neutron stars in quiescent, transient X-ray binaries and neutron stars that undergo thermonuclear bursts are sensitive to mass and radius. The mass–radius relation of neutron stars depends on the equation of state (EoS) that governs their interior. Constraining this relation accurately is therefore of fundamental importance to understand the nature of dense matter. In this context, we introduce a pipeline to calculate realistic model spectra of rotating neutron stars with hydrogen and helium atmospheres. An arbitrarily fast-rotating neutron star with a given EoS generates the spacetime in which the atmosphere emits radiation. We use the LORENE/NROTSTAR code to compute the spacetime numerically and the ATM24 code to solve the radiative transfer equations self-consistently. Emerging specific intensity spectra are then ray-traced through the neutron star’s spacetime from the atmosphere to a distant observer with the GYOTO code. Here, we present and test our fully relativistic numerical pipeline. To discuss and illustrate the importance of realistic atmosphere models, we compare our model spectra to simpler models like the commonly used isotropic color-corrected blackbody emission. We highlight the importance of considering realistic model-atmosphere spectra together with relativistic ray-tracing to obtain accurate predictions. We also insist upon the crucial impact of the star’s rotation on the observables. Finally, we close a controversy that has been ongoing in the literature in the recent years, regarding the validity of the ATM24 code.

Digital Signal Processing Techniques for the GIFTS SM EDU

NASA Technical Reports Server (NTRS)

Tian, Jialin; Reisse, Robert A.; Gazarik, Michael J.

2007-01-01

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) Sensor Module (SM) Engineering Demonstration Unit (EDU) is a high resolution spectral imager designed to measure infrared (IR) radiance using a Fourier transform spectrometer (FTS). The GIFTS instrument employs three Focal Plane Arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. This paper describes several digital signal processing (DSP) techniques involved in the development of the calibration model. In the first stage, the measured raw interferograms must undergo a series of processing steps that include filtering, decimation, and detector nonlinearity correction. The digital filtering is achieved by employing a linear-phase even-length FIR complex filter that is designed based on the optimum equiripple criteria. Next, the detector nonlinearity effect is compensated for using a set of pre-determined detector response characteristics. In the next stage, a phase correction algorithm is applied to the decimated interferograms. This is accomplished by first estimating the phase function from the spectral phase response of the windowed interferogram, and then correcting the entire interferogram based on the estimated phase function. In the calibration stage, we first compute the spectral responsivity based on the previous results and the ideal Planck blackbody spectra at the given temperatures, from which, the calibrated ambient blackbody (ABB), hot blackbody (HBB), and scene spectra can be obtained. In the post-calibration stage, we estimate the Noise Equivalent Spectral Radiance (NESR) from the calibrated ABB and HBB spectra. The NESR is generally considered as a measure of the instrument noise performance, and can be estimated as the standard deviation of calibrated radiance spectra from multiple scans. To obtain an estimate of the FPA performance, we developed an efficient method of generating pixel performance assessments. In addition, a random pixel selection scheme is developed based on the pixel performance evaluation. This would allow us to perform the calibration procedures on a random pixel population that is a good statistical representation of the entire FPA. The design and implementation of each individual component will be discussed in details.

THE X-RAY THROUGH OPTICAL FLUXES AND LINE STRENGTHS OF TIDAL DISRUPTION EVENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roth, Nathaniel; Kasen, Daniel; Guillochon, James

We study the emission from tidal disruption events (TDEs) produced as radiation from black hole accretion propagates through an extended, optically thick envelope formed from stellar debris. We analytically describe key physics controlling spectrum formation, and present detailed radiative transfer calculations that model the spectral energy distribution and optical line strengths of TDEs near peak brightness. The steady-state transfer is coupled to a solver for the excitation and ionization states of hydrogen, helium, and oxygen (as a representative metal), without assuming local thermodynamic equilibrium. Our calculations show how an extended envelope can reprocess a fraction of soft X-rays and producemore » the observed optical fluxes of the order of 10{sup 43} erg s{sup −1}, with an optical/UV continuum that is not described by a single blackbody. Variations in the mass or size of the envelope may help explain how the optical flux changes over time with roughly constant color. For high enough accretion luminosities, X-rays can escape to be observed simultaneously with the optical flux. Due to optical depth effects, hydrogen Balmer line emission is often strongly suppressed relative to helium line emission (with He ii-to-H line ratios of at least 5:1 in some cases) even in the disruption of a solar-composition star. We discuss the implications of our results to understanding the type of stars destroyed in TDEs and the physical processes responsible for producing the observed flares.« less

Herschel Observations and Updated Spectral Energy Distributions of Five Sunlike Stars with Debris Disks

NASA Astrophysics Data System (ADS)

Dodson-Robinson, Sarah E.; Su, Kate Y. L.; Bryden, Geoff; Harvey, Paul; Green, Joel D.

2016-12-01

Observations from the Herschel Space Observatory have more than doubled the number of wide debris disks orbiting Sunlike stars to include over 30 systems with R > 100 AU. Here, we present new Herschel PACS and reanalyzed Spitzer MIPS photometry of five Sunlike stars with wide debris disks, from Kuiper Belt size to R > 150 AU. The disk surrounding HD 105211 is well resolved, with an angular extent of >14″ along the major axis, and the disks of HD 33636, HD 50554, and HD 52265 are extended beyond the PACS point-spread function size (50% of energy enclosed within radius 4.″23). HD 105211 also has a 24 μm infrared excess, which was previously overlooked, because of a poorly constrained photospheric model. Archival Spitzer IRS observations indicate that the disks have small grains of minimum radius a min ˜ 3 μm, although a min is larger than the radiation-pressure blowout size in all systems. If modeled as single-temperature blackbodies, the disk temperatures would all be <60 K. Our radiative transfer models predict actual disk radii approximately twice the radius of a model blackbody disk. We find that the Herschel photometry traces dust near the source population of planetesimals. The disk luminosities are in the range 2 × 10-5 ⩽ L/L ⊙ ⩽ 2 × 10-4, consistent with collisions in icy planetesimal belts stirred by Pluto-size dwarf planets.

X-Ray Study of Variable Gamma-Ray Pulsar PSR J2021+4026

NASA Astrophysics Data System (ADS)

Wang, H. H.; Takata, J.; Hu, C.-P.; Lin, L. C. C.; Zhao, J.

2018-04-01

PSR J2021+4026 showed a sudden decrease in the gamma-ray emission at the glitch that occurred around 2011 October 16, and a relaxation of the flux to the pre-glitch state at around 2014 December. We report X-ray analysis results of the data observed by XMM-Newton on 2015 December 20 in the post-relaxation state. To examine any change in the X-ray emission, we compare the properties of the pulse profiles and spectra at the low gamma-ray flux state and at the post-relaxation state. The phase-averaged spectra for both states can be well described by a power-law component plus a blackbody component. The former is dominated by unpulsed emission and probably originated from the pulsar wind nebula as reported by Hui et al. The emission property of the blackbody component is consistent with the emission from the polar cap heated by the back-flow bombardment of the high-energy electrons or positrons that were accelerated in the magnetosphere. We found no significant change in the X-ray emission properties between two states. We suggest that the change of the X-ray luminosity is at an order of ∼4%, which is difficult to measure with the current observations. We model the observed X-ray light curve with the heated polar cap emission, and we speculate that the observed large pulsed fraction is owing to asymmetric magnetospheric structure.