Effects Of Black-body Radiation Research Articles

Three-dimensional shape measurement technique for hot and shiny forging

For hot and shiny forging, rapid optical three-dimensional (3D) shape measurement can find the defects in time, improve manufacturing efficiency and reduce manufacturing cost. Optical 3D measurement of hot and shiny forging faces following three challenges. (a) Influence of blackbody radiation on the red band of visible light leads to saturation of captured fringe pattern. (b) Infrared band of blackbody radiation causes the camera to heat up. (c) Specular reflection of shiny forging leads to local saturation of captured fringe pattern. To address the above issues, we propose an effective optical 3D measurement scheme for hot and shiny forging in this paper. Firstly, the experiments demonstrate that the influence of blackbody radiation on visible light is concentrated in red light band and has no crosstalk in the blue light band, so we adopt blue light projection and blue light band-pass filter (BBF) to capture clear fringe pattern. Secondly, since the BBF cannot block the near-infrared component, we use an infrared light cutoff filter (ICF) to reduce the thermal effect of blackbody radiation. Finally, we analyze the Fourier transform (FT) spectrum of saturated fringe pattern caused by specular reflection, and propose an efficient Butterworth low-pass filtering (BLPF) method that does not require additional hardware, algorithm processing, and image assistance. The experimental results verify the effectiveness of the proposed scheme.

Black-body radiation-induced photodissociation and population redistribution of weakly bound states in H2 +

Molecular hydrogen ions in weakly bound states close to the first dissociation threshold are attractive quantum sensors for measuring the proton-to-electron mass ratio and hyperfine-induced ortho-para mixing. The experimental accuracy of previous spectroscopic studies relying on fast ion beams could be improved by using state-of-the-art ion trap setups. With the electric-dipole moment vanishing in H and preventing fast spontaneous emission, radiative lifetimes of the order of weeks are found. We include the effect of black-body radiation that can lead to photodissociation and rovibronic state redistribution to obtain effective lifetimes for trapped ion experiments. Rate coefficients for bound-bound and bound-continuum processes were calculated using adiabatic nuclear wave functions and nonadiabatic energies, including relativistic and radiative corrections. Effective lifetimes for the weakly bound states were obtained by solving a rate equation model and lifetimes in the range of 4–523 and >215 ms were found at room temperature and liquid nitrogen temperature, respectively. Black-body induced photodissociation was identified as the lifetime-limiting effect, which guarantees the purity of state-selectively generated molecular ion ensembles. The role of hyperfine-induced g/u-mixing, which allows pure rovibrational transitions, was found to be negligible.

Comparison of temperature, current density, and light intensity distributions of nano-resistor patterns for an improved solid state incandescent light emitting device simulation model

The solid-state incandescent light-emitting device is an emerging optoelectronic device that is made on a silicon wafer using IC compatible materials and processes. Light emission takes place by thermal excitation of numerous nano-sized, high-resistivity conductive paths, i.e., nano-resistors, formed from the dielectric breakdown of an MOS capacitor. A simulation method that uses comsol multiphysics, python, and matlab to predict the temperature, current density, and light intensity distributions of various nano-resistor patterns in the device is presented. The Joule heating and blackbody radiation effects are correlated to the temperature and light emission profiles. The effect of mesh quality and depth on these distributions is also investigated. Electrical and optoelectronic properties of the nano-resistors calculated from this new program are consistent with the experimental results.

Design and characterization of a cryogenic linear Paul ion trap for ion-neutral reaction studies.

Ultra-high vacuum conditions are ideal for the study of trapped ions. They offer an almost perturbation-free environment, where ions confined in traps can be studied for extended periods of time-facilitating precision measurements and allowing infrequent events to be observed. However, if one wishes to study processes involving molecular ions, it is important to consider the effect of blackbody radiation (BBR). The vast majority of molecular ions interact with BBR. At 300K, state selection in trapped molecular ions can be rapidly lost (in a matter of seconds). To address this issue, and to maintain state selectivity in trapped molecular ions, a cryogenic ion trap chamber has been constructed and characterized. At the center of the apparatus is a linear Paul ion trap, where Coulomb crystals can be formed for ion-neutral reaction studies. Optical access is provided, for lasers and for imaging of the crystals, alongside ion optics and a flight tube for recording time-of-flight mass spectra. The ion trap region, encased within two nested temperature stages, reaches temperatures below 9K. To avoid vibrations from the cryocooler impeding laser cooling or imaging of the ions, vibration-damping elements are explicitly included. These components successfully inhibit the coupling of vibrations from the cold head to the ion trap-confirmed by accelerometer measurements and by the resolution of images recorded at the trap center (at 9 and 295K). These results confirm that the cryogenic ion trap apparatus meets all requirements for studying ion-neutral reactions under cold, controlled conditions.

Slow Decay Processes of Electrostatically Trapped Rydberg NO Molecules.

Nitric oxide (NO) molecules initially traveling at 795 m/s in pulsed supersonic beams have been photoexcited to long-lived hydrogenic Rydberg-Stark states, decelerated and electrostatically trapped in a cryogenically cooled, chip-based transmission-line Rydberg-Stark decelerator. The decelerated and trapped molecules were detected insitu by pulsed electric field ionization. The operation of the decelerator was validated by comparison of the experimental data with the results of numerical calculations of particle trajectories. Studies of the decay of the trapped molecules on timescales up to 1ms provide new insights into the lifetimes of, and effects of blackbody radiation on, Rydberg states of NO.

Confinement of High- and Low-Field-Seeking Rydberg Atoms Using Time-Varying Inhomogeneous Electric Fields.

Helium atoms in high- and low-field-seeking Rydberg states with linear and quadratic Stark shifts have been confined in two dimensions and guided over a distance of 150mm using time-varying inhomogeneous electric fields. This was achieved with an electrode structure composed of four parallel cylindrical rods to which voltages were applied to form oscillating and rotating saddle-point fields. These two modes of operation result in time-averaged pseudopotentials that confine samples in high- and low-field-seeking states about the axis of the device. The experimental data have been compared to the results of numerical particle trajectory calculations that include effects of blackbody radiation and electric field ionization. The results highlight important contributions from single-photon blackbody-induced transitions that cause large changes in the principal quantum number of the Rydberg atoms.

Positronium production in cryogenic environments

We report measurements of positronium (Ps) formation following positron irradiation of mesoporous ${\mathrm{SiO}}_{2}$ films and Ge(100) single crystals at temperatures ranging from 12\char21{}700 K. As both of these materials generate Ps atoms via nonthermal processes, they are able to function as positron-positronium converters at cryogenic temperatures. Our data show that such Ps formation is possibly provided the targets are not compromised by adsorption of residual gas. In the case of ${\mathrm{SiO}}_{2}$ films, we observe a strong reduction in the Ps formation efficiency following irradiation with UV laser light ($\ensuremath{\lambda}=243.01$ nm) below 250 K, in accordance with previous observations of radiation-induced surface paramagnetic centers. Conversely, Ps emission from Ge is enhanced by irradiation with visible laser light ($\ensuremath{\lambda}=532$ nm) via a photoemission process that persists at cryogenic temperatures. Both mesoporous ${\mathrm{SiO}}_{2}$ films and Ge crystals were found to produce Ps efficiently in cryogenic environments. Accordingly, these materials are likely to prove useful in several areas of research, including Ps mediated antihydrogen formation conducted in the cold bore of a superconducting magnet, the production of Rydberg Ps for experiments in which the effects of black-body radiation must be minimized, and the utilization of mesoporous structures that have been modified to produce cold Ps atoms.

A stability analysis of a self-gravitating optically thick magnetized quantum plasma including the effects of black body radiation

We have discussed the effect of black body radiation on self-gravitational instability of infinite homogeneous, optically thick quantum plasma carrying a uniform magnetic field. With the help of relevant linearized perturbation quantum magneto-hydrodynamic equations of the problem, using normal mode technique, a general dispersion relation is obtained with black body radiation, quantum correction and magnetic field. Discussed when propagation vectors are longitudinal and transverse to the magnetic field, separately. The new Jeans condition of instability due to quantum correction, magnetic field and black body radiation is discussed. We find that in transverse mode of propagation the condition of Jeans instability of gaseous plasma is modified by quantum correction, magnetic field and black body radiation. In the case of longitudinal mode, it is unaffected by a magnetic field, as this mode provides the Alfven mode separately with the gravitational mode. From the curves we found that the effects of quantum correction, black body radiation and magnetic field have a stabilizing influence.

Distilled shock conditions for ideal magneto-acoustic shock waves in an optically thick medium

AbstractThe shock waves are important features in the analysis of transonic magnetohydrodynamical (MHD) flows where thermal radiation could also be significant. In this paper the effects of black-body radiation on non-relativistic shock waves in an ideal radiation MHD model for the optically thick case are discussed. Distilled shock conditions were derived and discussed for the case of a fixed ratio of specific heats of an ideal gas (γ) and ratio of gas to total pressure (b). The special case, when jumps in γ and/or b are allowed, was also considered.

Driving Rydberg-Rydberg Transitions from a Coplanar Microwave Waveguide

The coherent interaction between ensembles of helium Rydberg atoms and microwave fields in the vicinity of a solid-state coplanar waveguide is reported. Rydberg-Rydberg transitions, at frequencies between 25 and 38 GHz, have been studied for states with principal quantum numbers in the range 30-35 by selective electric-field ionization. An experimental apparatus cooled to 100 K was used to reduce effects of blackbody radiation. Inhomogeneous, stray electric fields emanating from the surface of the waveguide have been characterized in frequency- and time-resolved measurements and coherence times of the Rydberg atoms on the order of 250 ns have been determined. These results represent a key element in the development of an experimental architecture to interface Rydberg atoms with solid-state devices.

Blackbody-radiation shift in a 199Hg+ ion optical frequency standard

The background blackbody radiation causes the shift of the hyperfine energy level and affects the accuracy of the optical frequency standard. The polarizabilities of the hyperfine energy levels 5d106s2S1/2 (F=0) and 5d96s2 2D5/2 (F=2) of 199Hg+ are evaluated and the relative frequency shift at room temperature due to blackboby radiation is calculated to be -5.410-17. Finally the effect of blackbody radiation on single 199Hg+ optical frequency standard is discussed at an ultralow temperature.

Quantum efficiencies, absolute intensities and signal‐to‐blackbody ratios of high‐temperature laser‐induced thermographic phosphors

There are a number of issues related to high-temperature phosphor thermometry, which include measurement of faster decays, decreasing emission intensity and rising levels of blackbody radiation, that will impose limits on the maximum delectable temperature. This paper provides absolute intensity measurements, quantum efficiencies and signal-to-blackbody radiation ratios at peak emission wavelengths, at various temperatures (20-1400°C), for Y(2)O(3):Eu, YAG:Tb and YAG:Tm thermographic phosphors under 266 and 355 nm excitation from a Q-switched Nd:YAG laser. These terms are beneficial in a number of ways for engineers wanting to use a phosphor thermometry solution at high temperatures. They may also provide additional insight to the physical luminescence processes of phosphors at high temperatures. The phosphor signal:blackbody radiation ratio is useful because it combines the effects of blackbody radiation and phosphor emission intensities at various temperatures, providing a valuable quantitative evaluation that can be used as a design aid for phosphor selection. A figure of merit is the temperature when the blackbody radiation equals the phosphor emission (ratio = 1); this is the cross-over temperature at which the blackbody radiation rapidly starts to overtake and mask out phosphor emissions. To the best of our knowledge no such work exists previously. The results presented show a variation in phosphor intensity with increasing temperature, and although the intensity and quantum efficiencies for Y(2)O(3):Eu and YAG:Tb were much greater than YAG:Tm at low temperatures, YAG:Tm was found to be the most efficient phosphor investigated at higher temperatures (>900°C). With a peak emission wavelength of 458 nm, YAG:Tm experienced the lowest proportion of blackbody radiation therefore its advantage at higher temperatures was further amplified and was found to offer an advantage of approximately +350°C and +250°C increased upper temperature capability compared to Y(2)O(3):Eu and YAG:Tb phosphors, respectively.

Blackbody-radiation correction to the polarizability of helium

The correction to the polarizability of helium due to blackbody radiation is calculated near room temperature. A precise theoretical determination of the blackbody radiation correction to the polarizability of helium is essential for dielectric gas thermometry and for the determination of the Boltzmann constant. We find that the correction, for not too high temperature, is roughly proportional to a modified hyperpolarizability (two-color hyperpolarizability), which is different from the ordinary hyperpolarizability of helium. Our explicit calculations provide a definite numerical result for the effect and indicate that the effect of blackbody radiation can be excluded as a limiting factor for dielectric gas thermometry using helium or argon.

Dynamic polarizabilities and related properties of clock states of the ytterbium atom

We carry out relativistic many-body calculations of the static and dynamic dipole polarizabilities of the ground 6s2 1S0 and the first excited 6s6p 3Po0 states of Yb. With these polarizabilities, we compute several properties of Yb relevant to optical lattice clocks operating on the 6s2 1S0–6s6p 3Po0 transition. We determine (i) the first four magic wavelengths of the laser field for which the frequency of the clock transition is insensitive to the laser intensity. While the first magic wavelength is known, we predict the second, the third and the fourth magic wavelengths to be 551 nm, 465 nm and 413 nm. (ii) We re-evaluate the effect of black-body radiation on the frequency of the clock transition, the resulting clock shift at T = 300 K being −1.41(17) Hz. (iii) We compute long-range interatomic van der Waals coefficients (in a.u.) C6(6s2 1S0 + 6s2 1S0) = 1909(160), C6(6s2 1S0 + 6s6p 3P0) = 2709(338) and C6(6s6p 3P0 + 6s6p 3P0) = 3886(360). Finally, we determine the atom-wall interaction coefficients (in a.u.), C3(6s2 1S0) = 3.34 and C3(6s6p 3P0) = 3.68. We also address and resolve a disagreement between previous calculations of the static polarizability of the ground state.

Sr Lattice Clock at 1 × 10 –16 Fractional Uncertainty by Remote Optical Evaluation with a Ca Clock

Optical atomic clocks promise timekeeping at the highest precision and accuracy, owing to their high operating frequencies. Rigorous evaluations of these clocks require direct comparisons between them. We have realized a high-performance remote comparison of optical clocks over kilometer-scale urban distances, a key step for development, dissemination, and application of these optical standards. Through this remote comparison and a proper design of lattice-confined neutral atoms for clock operation, we evaluate the uncertainty of a strontium (Sr) optical lattice clock at the 1 x 10(-16) fractional level, surpassing the current best evaluations of cesium (Cs) primary standards. We also report on the observation of density-dependent effects in the spin-polarized fermionic sample and discuss the current limiting effect of blackbody radiation-induced frequency shifts.

BLACKBODY RADIATION: ROSETTA STONE OF HEAT BATH MODELS

The radiation field can be regarded as a collection of independent harmonic oscillators and, as such, constitutes a heat bath. Moreover, the known form of its interaction with charged particles provides a "rosetta stone" for deciding on and interpreting the correct interaction for the more general case of a quantum particle in an external potential and coupled to an arbitrary heat bath. In particular, combining QED with the machinery of stochastic physics, enables the usual scope of applications to be widened. We discuss blackbody radiation effects on: the equation of motion of a radiating electron (obtaining an equation of motion which is free from runaway solutions), anomalous diffusion, the spreading of a Gaussian wave packet, and decoherence effects due to zero-point oscillations. In addition, utilizing a formula we obtained for the free energy of an oscillator in a heat bath, enables us to determine all the quantum thermodynamic functions of interest (particularly in the areas of quantum information and nanophysics where small systems are involved) and from which we obtain temperature dependent Lamb shifts, quantum effects on the entropy at low temperature and implications for Nernst's law.

A Computational Fluid Dynamics Model for Designing Heat Exchangers based on Natural Convection

A computational fluid dynamics model was created for the design of a natural convection shell-and-tube heat exchanger with baffles. The flow regime proved to be turbulent and this was modelled using the k – ω turbulence model. The features of the complex geometry were simplified considerably resulting in an almost two-dimensional mesh with only 30 000 mesh cells. The effect of black-body radiation was investigated. The modelling results were validated experimentally and a model neglecting the effect of radiation turned out to be sufficiently accurate, reducing calculation times with a factor 60. Different meshes were used to check that the solution did not depend on the mesh chosen. The measurements indicated that the cross-flow caused by the baffles improved the heat-flux dramatically. The heat exchanger in this case study was intended to be used in an experimental greenhouse. The usefulness of the heat exchanger model was demonstrated by applying it to relevant variations of the experimental arrangements. The model calculations resulted in many recommendations on the dimensions and the operation of the heat exchanger.

Atomic physics with a relativistic H− beam

A study is currently under way at the Fermi National Accelerator Laboratory for a superconducting linear accelerator that will accelerate H− ions to 8 GeV. This Proton Driver beam is intended to be injected, stripped down to protons, into the 120 GeV Main Injector for the mass production of neutrinos aimed at a neutrino detector (MINOS) in a mine shaft in Soudan, Minnesota, USA, for the study of neutrino oscillations. The highly relativistic kinematics of the one- and two-electron atomic systems (H0 and H−) that could be produced by this accelerator present unique research opportunities in atomic physics for the study of fundamental questions. Finally we shall discuss the effects of black-body radiation on high-energy H− beams.

In situ deposition rate monitoring during the three-stage-growth process of Cu(In,Ga)Se 2 absorber films

The controllability of the three-stage-growth process of Cu(In,Ga)Se 2 films was investigated, implementing two different substrate temperature monitoring channels simultaneously: (a) a thermocouple at the rear side of the substrate, and (b) a pyrometer, measuring the emission of heat radiation from the front surface of the growing film. By this setup not only the film composition, i.e. the relative incorporation rate of Cu and group III elements, but as well the absolute growth rate can be monitored on-line during growth. The heat radiation intensity during the first growth stage (deposition of (In,Ga) 2Se 3 precursor films) exhibits characteristic oscillations. The oscillation period is inversely proportional to the growth rate. The oscillations are caused by thickness interference effects of black body radiation within the growing film. By a simulation of the infrared emissivity, the refractive index n igs=2.9 and absorption coefficient k igs=0.2 of the growing film could be extracted. Employing our process, Mo/CIGS/CdS/ZnO/Al solar cells with an efficiency up to 16.4% could be realized.

Black-body radiation effects and light shifts in atomic frequency standards

A general method is presented for calculating the higher-order terms of series in powers of the black-body radiation field for the Stark-state wavefunctions, dipole transition matrix elements and corresponding frequency shifts of hyperfine splitting in the ground states for Cs and Rb atoms. A numerical method for calculating the light shifts in Sr atoms is described. It is based on the Green function method for summation over all intermediate states and exact Dirac–Fock wavefunctions for the resonant transitions to the first excited s-, p- and d-states. By comparing the calculated Stark shift with results of measurements employing atomic frequency standards, the black-body radiation effects on the ground state are analysed.