Intense Background Radiation Research Articles

A decay database of coincident γ−γ and γ−X-ray branching ratios for in-field spectroscopy applications

Current fieldable spectroscopy techniques often use single detector systems heavily impacted by interferences from intense background radiation fields. These effects result in low-confidence measurements that can lead to misinterpretation of the collected spectrum. To help improve interpretation of the fission products and short-lived radionuclides produced in a composite sample, a coincidence-database is being developed in support of a robust portable and X-ray coincidence detector system concurrently under development at the Pacific Northwest National Laboratory for in-field deployment. Hitherto, no database exists containing coincident γ−γ and γ−X-ray branching-ratio intensities on an absolute scale that will greatly enhance isotopic identification for in-field applications. As part of this project, software has been developed to parse all radioactive-decay data sets from the Evaluated Nuclear Structure Data File (ENSDF) archive to enable translation into a more useful JavaScript Object Notation (JSON) formats that more readily supports query-based data manipulation. The coincident database described in this work is the first of its kind and contains coincidence γ−γ and γ−X-ray intensities and their corresponding uncertainties, together with auxiliary metadata associated with each decay data set. The new JSON format provides a convenient and portable means of data storage that can be imported into analysis frameworks with relatively low overhead allowing for meaningful comparison with measured data.

An analytical model of zenith radiance under different atmosphere and earth-surface conditions for JHKs bands

The application of star sensor navigation to aircraft and ships is a significant development direction. Due to the intense sky background radiation in the daytime, it is difficult for a visible-light camera to detect stars effectively in near-earth space, the development of a short-wavelength infrared (SWIR, especial for JHKs bands) detector provides the possibility for it. However, in the system design, simulation verification, and software integration of star sensor based on SWIR, a mass of sky background data of JHKs bands under different atmosphere and earth-surface conditions is needed as input. Although the existing atmospheric radiative transfer software can generate large amounts of discrete sky background data in some directions, it has a complicated operation, low efficiency, and time-consuming disadvantage, which is challenging to meet the real-time application in engineering. To use the sky background radiation data more efficiently and conveniently, an analytical model of zenith radiance for JHKs bands is urgent to build. Zenith radiance reference data are generated by libRadtran. Atmospheric absorption function and atmospheric scattering function are used to construct the analytical model of zenith radiance. The Levenberg-Marquardt (L-M) method is used to solve the parameters of the analytical model of zenith radiance. The Adaptive Moment Estimation (Adam) method is used to optimize the parameters of the analytical model of zenith radiance. The mean relative error between the zenith radiance's analytical function value and the zenith radiance's reference data is calculated to evaluate the accuracy of the constructed analytical model of zenith radiance. The results show that the mean relative errors are no greater than 2.54%, 2.15%, 2.26%; the root mean square errors are no greater than 1.0414, 0.2462, 0.0642; the correlation coefficients are no less than 0.9985, 0.9976, 0.9979 for all combination of cases corresponding to JHKs bands. It indicates that zenith radiance's analytical model constructed is exact and can provide a useful reference for the star sensor's demonstration design and application assessment based on SWIR technology.

Most stars (and planets?) are born in intense radiation fields

ABSTRACT Protostars and young stars are strongly spatially ‘clustered’ or ‘correlated’ within their natal giant molecular clouds. We demonstrate that such clustering leads to the conclusion that the incident bolometric radiative flux upon a random young star/disc is enhanced (relative to volume-averaged fluxes) by a factor that increases with the total stellar mass of the complex. Because the Galactic cloud mass function is top-heavy, the typical star in our Galaxy experienced a much stronger radiative environment than those forming in well-observed nearby (but relatively small) clouds, exceeding fluxes in the Orion Nebular Cluster by factors of ≳30. Heating of the circumstellar disc around a median young star is dominated by this external radiation beyond $\sim \! 50$ au. And if discs are not well shielded by ambient dust, external ultraviolet irradiation can dominate over the host star down to sub-au scales. Another consequence of stellar clustering is an extremely broad Galaxy-wide distribution of incident flux (spanning >10 decades), with half the Galactic star formation in a substantial ‘tail’ towards even more intense background radiation. We also show that the strength of external irradiation is amplified superlinearly in high-density environments such as the Galactic Centre, starbursts, or high-redshift galaxies.

Optical Parameters Optimization for All-Time Star Sensor

As an important development direction of star sensor technology, the All-Time star sensor technology can expand the application of star sensors to flight platforms inside the atmosphere. Due to intense atmospheric background radiation during the daytime, the commonly used star sensors operating in the visible wavelength range are significantly limited in their ability to detect stars, and hence the All-Time star sensor technology which is based on the shortwave infrared (SWIR) imaging system has become an effective research direction. All-Time star sensor detection capability is significantly affected by observation conditions and, therefore, an optimized selection of optical parameters, which mainly includes the field of view (FOV) and the detection wavelength band, can effectively improve the detection performance of All-Time star sensors under harsh observation conditions. This paper uses the model simulation method to analyze and optimize the optical parameters under various observation conditions in a high-altitude environment. A main parameter among those discussed is the analysis of detection band optimization based on the SWIR band. Due to the huge cost constraints of high-altitude experiments, we conducted experiments near the ground to verify the effectiveness of the detection band selection and the correctness of the SWIR star sensor detection model, which thereby proved that the optimization of the optical parameters for high altitudes was effective and could be used as a reference.

ДВА МЕХАНИЗМА АЭРОТЕРМОМЕХАНИЧЕСКОГО РАЗРУШЕНИЯ ПРИ ГИПЕРЗВУКОВЫХ СКОРОСТЯХ ОБТЕКАНИЯ В ВОЗДУХЕ

The issues of protecting the Earth from the collision with space objects are considered. The effectiveness of various methods of crushing such space objects, to alleviate the detrimental effects of their falling onto the Earth, are analyzed. In the framework of the task, the problem of experimentally studying aerothermomechanical carryover at the initial stage of the acceleration of a model of a meteorite at hypersonic velocities in the conditions of intensive background radiation is solved. Based on x-ray pictures and photographs of a body moving through the Earth's atmosphere at hypersonic velocities, a qualitative picture of the aerothermomechanical carryover and the deceleration of steel balls and balls made of a composite wolfram-nickel-iron alloy is presented. The processes observed during the motion of the steel balls and the balls of the composite alloy are shown to differ in their character. Their motion under the effect of the heat flow (convective or radiation) is accompanied by intensive heating of the frontal surface of the objects, followed by its carryover, which results in the changes of its mass and outline. During the motion from the polar part of the frontal surface along the flow, the level of thermal loading decreases and, hence, the film cools down. Accordingly, the viscosity of the melt increases, the flow rate of the film decreases, and a burl is formed. The accumulating melt periodically drops from the body surface. In the process of deceleration the flows decrease, the carryover stops, after which the outline of the objects no longer changes, and the surface temperature drops. For the steel balls, the carryover results from melting through the outer layer and drop losing. The carryover mechanism in the balls of the wolfram-nickel-iron alloy is connected with the different melting temperatures of its components and results in the motion of the wolfram particles in the direction normal to the direction of the motion of the body.Keywords: aero-thermo-mechanical ablation, aeroballistic experiment, X-ray imaging.

Enrichment of 57Fe isotope in neutron flux of nuclear reactors observed by Mössbauer spectroscopy

The abundance of 57Fe isotope in nuclear reactor core materials can be considerably enriched by neutron-capture 56Fe(n,γ) reactions. This is demonstrated using the sections of Zr-2.5 wt.%Nb pressure tubes removed from two CANDU* reactors. The tubes contained 0.11 and 0.04wt% Fe and were irradiated for about 10 effective full power years (EFPY) up to ~1026n/m2 fast neutron (E > 1MeV) fluencies. The Mössbauer spectra of 57Fe in irradiated samples indicated up to 10 times larger areas than unirradiated off-cuts from the same pressure tubes. The observed effect is in accord with the values calculated for known thermal neutron-capture cross-sections and resonance capture integrals, neutron flux profiles and spectra, and times of irradiation. The build-up of 57Fe facilitated recording Mössbauer absorption spectra of alloys with minor amount of Fe down to ~ 400ppm, despite intense background radiation emitted by samples. These findings can open new possibilities in post-irradiation studies of alloys used in nuclear reactors and in other objects subjected to large neutron fluencies.

Online monitoring of the Osiris reactor with the Nucifer neutrino detector

Originally designed as a new nuclear reactor monitoring device, the Nucifer detector has successfully detected its first neutrinos. We provide the second shortest baseline measurement of the reactor neutrino flux. The detection of electron antineutrinos emitted in the decay chains of the fission products, combined with reactor core simulations, provides an new tool to assess both the thermal power and the fissile content of the whole nuclear core and could be used by the Inter- national Agency for Atomic Energy (IAEA) to enhance the Safeguards of civil nuclear reactors. Deployed at only 7.2m away from the compact Osiris research reactor core (70MW) operating at the Saclay research centre of the French Alternative Energies and Atomic Energy Commission (CEA), the experiment also exhibits a well-suited configuration to search for a new short baseline oscillation. We report the first results of the Nucifer experiment, describing the performances of the 0.85m3 detector remotely operating at a shallow depth equivalent to 12m of water and under intense background radiation conditions. Based on 145 (106) days of data with reactor ON (OFF), leading to the detection of an estimated 40760 electron antineutrinos, the mean number of detected antineutrinos is 281 +- 7(stat) +- 18(syst) electron antineutrinos/day, in agreement with the prediction 277(23) electron antineutrinos/day. Due the the large background no conclusive results on the existence of light sterile neutrinos could be derived, however. As a first societal application we quantify how antineutrinos could be used for the Plutonium Management and Disposition Agreement.

Carbon–polydimethylsiloxane-based integratable optical technology for spectroscopic analysis

A polydimethylsiloxane (PDMS)-based optical system has been demonstrated. To suppress intense background radiation due to multiple internal scatting in a transparent material, a composite structure of a carbon–PDMS compound and PDMS was proposed. The index matching of the real part of the refractive index can suppress internal scattering, and an absorption of 99–99.7% was attained by using carbon micro particles and carbon nano tubes. The black-PDMS light channel functions as a light filter for straight pass, and an optical density of 5 was obtained by bending the filter.

Planets in other universes: habitability constraints on density fluctuations and galactic structure

Motivated by the possibility that different versions of the laws of physics could be realized within other universes, this paper delineates the galactic structure parameters that allow for habitable planets and revisits constraints on the amplitude Q of the primordial density fluctuations. Previous work indicates that large values of Q lead to galaxies so dense that planetary orbits cannot survive long enough for life to develop. Small values of Q lead to delayed star formation, loosely bound galaxies, and compromised heavy element retention. This work generalizes previous treatments in the following directions: [A] We consider models for the internal structure of the galaxies, including a range of stellar densities, and find the fraction of the resulting galactic real estate that allows for stable, long-lived planetary orbits. [B] For high velocity encounters, we perform a large ensemble of numerical simulations to estimate cross sections for the disruption of planetary orbits due to interactions with passing stars. [C] We consider the background radiation fields produced by the galaxies: if a galaxy is too compact, the night sky seen from a potentially habitable planet can provide more power than the host star. [D] One consequence of intense galactic background radiation fields is that some portion of the galaxy, denoted as the Galactic Habitable Zone, will provide the right flux levels to support habitable planets for essentially any planetary orbit including freely floating bodies (but excluding close-in planets). As the value of Q increases, the fraction of stars in a galaxy that allow for (traditional) habitable planets decreases due to both orbital disruption and the intense background radiation. However, the outer parts of the galaxy always allow for habitable planets, so that the value of Q does not have a well-defined upper limit (due to scattering or radiation constraints). Moreover, some Galactic Habitable Zones are large enough to support more potentially habitable planets than the galaxies found in our universe. These results suggest that the possibilities for habitability in other universes are somewhat more favorable and far more diverse than previously imagined.

CMB quenching of high-redshift radio-loud AGNs

The very existence of more than a dozen of high-redshift (z ≳ 4) blazars indicates that a much larger population of misaligned powerful jetted active galactic nucleus (AGN) was already in place when the Universe was ≲1.5 Gyr old. Such parent population proved to be very elusive, and escaped direct detection in radio surveys so far. High-redshift blazars themselves seem to be failing in producing extended radio lobes, raising questions about the connection between such class and the vaster population of radio galaxies. We show that the interaction of the jet electrons with the intense cosmic microwave background (CMB) radiation explains the lack of extended radio emission in high-redshift blazars and in their parent population, helping to explain the apparently missing misaligned counterparts of high-redshift blazars. On the other hand, the emission from the more compact and more magnetized hotspots are less affected by the enhanced CMB energy density. By modelling the spectral energy distribution of blazar lobes and hotspots, we find that most of them should be detectable by low-frequency deep radio observations, e.g. by LOw-Frequency ARray for radio astronomy and by relatively deep X-ray observations with good angular resolution, e.g. by the Chandra satellite. At high redshifts, the emission of a misaligned relativistic jet, being debeamed, is missed by current large sky area surveys. The isotropic flux produced in the hotspots can be below ∼1 mJy and the isotropic lobe radio emission is quenched by the CMB cooling. Consequently, even sources with very powerful jets can go undetected in current radio surveys, and misclassified as radio-quiet AGNs.

A comparative analysis of the sensitivity of CsI (Tl), ZnO(Ga), and YAG(Ce) scintillators to the plasma background radiation under operating conditions of the ITER tokamak reactor

Problems related to neutral particle flux measurements on the ITER tokamak reactor under intense plasma background radiation conditions are considered. The results of measuring a background sensitivity with respect to neutron and γ-radiation for the scintillation detector, which is based on three different crystals (CsI (Tl), ZnO(Ga), and YAG(Ce)), are presented. The scintillators are compared and conclusions about the possibility of their applications in detectors of neutral particle analyzers currently created at the Ioffe Institute for the ITER tokamak reactor, are drawn.

Detection of weak optical signals in lidar measurements under noise conditions

An algorithm of weak optical signal processing in lidar measurements under intensive background radiation is described. The algorithm is based on transformation of the Poisson photoelectron flow forming at the output of the photodetector photocathode into a flux with sub-Poisson statistics due to its stochastic-determined “rarefaction.” The quality coefficients of the proposed algorithm are estimated.

In situ Si Wafer Surface Temperature Measurement during Flash Lamp Annealing

Automatic emissivity compensating radiation thermometry based on polaradiometry was applied to in situ wafer surface temperature measurement on a flash lamp annealing prototype system. The developed temperature measurement system consists of a dual polarization radiation thermometer and a modulating reference light source, which were mounted on two opposing ports of the process chamber. The intense background radiation from the flash lamp was successfully suppressed by introducing a water flow layer beneath the flash lamp unit and measuring at the water absorption band of 1.95 µm. Millisecond heating and cooling of the wafer was measured for various operating conditions of the flash lamp and for various silicon wafers including wafers with microstructures. The peak temperature was compared with the sheet resistance after treatment and device properties after fabrication. Good correlation was confirmed between sheet resistance and measured peak temperature for various flash lamp intensities irrespective of the surface emissivity or heating conditions. Transistor threshold voltage showed similar correlation, which verifies the applicability of the developed thermometer system to in situ measurement during production.

Measurement of Dust Optical Properties in the Coalsack Nebula

We have used FUSE and Voyager observations of dust-scattered starlight in the neighborhood of the Coalsack Nebula to derive the optical constants of the dust grains. The albedo is consistent with a value of 0.28 ± 0.04, and the phase function asymmetry factor with a value of 0.61 ± 0.07, throughout the spectral range from 900-1200 A, in agreement with previous determinations as well as theoretical predictions. We have now observed two regions (Ophiuchus and Coalsack) with intense diffuse background radiation and in both cases have found that the emission is due to light from nearby hot stars scattered by a relatively thin foreground cloud, with negligible contribution from the background molecular cloud.

Effect of intense background radiation on the sensitivity of a laser receiver with an iodine active quantum filter

The effect of background light on the sensitivity of a laser receiver with an iodine active quantum filter (λ=1.315 μm) was theoretically and experimentally investigated. Upon the reception of a 40-ns pulsed signal against the background of 2.5-fold attenuated radiation of a pulsed light source with a brightness temperature of 4 × 104 K, the sensitivity of this receiver for a signal-to-noise ratio of three and a diffraction-limited acceptance angle was experimentally shown to be equal to 20 photons, which exceeds the quantum limit by about a factor of two. This is consistent with the results of theoretical treatment and suggests that upon the detection of optical signals against the background of the solar disk, the sensitivity of this receiver should decrease by only 12%. This receiver was compared with a receiver employing a photomultiplier of the visible range. Upon the reception of optical signals with the same parameters against the background of the solar disk and an interference filter with a transmission band width of 5 nm, the sensitivity of a receiver equipped with an FEU-115 photomultiplier was shown to be equal to about 1400 photons for a signal-to-noise ratio of three.

Accretion Disk Flares in Energetic Radiation Fields

We consider the physics of magnetic flares in the energetic radiation field of an accretion disk corona (ADC). The X-ray emission from these flares is thought to be responsable for the observed hard powerlaw component in the X-ray spectra of galactic black hole candidates in their ‘high’ spectral state. During the flare event (inverse Compton) scattering of soft photons from the underlying disk into hard photons occurs on accelerated electrons in current sheets. The electrons are decelerated by the radiation drag force that results from the up-scattering. This friction-like effect of the intense background radiation field on the motion of the electrons in the sheet can be considered as a form of resistivity in the magnetohydrodynamical picture of the current sheet: Compton resistivity. A spectrum is derived for the up-scattered radiation from current sheets in the ADC and it is found that this spectrum mimics a powerlaw above a critical photon energy.

Radiation-Hardened Wall Detector for Alpha Particles

The measurement of the pitch angle distribution of energetic alphas escaping from a burning plasma represents a key next step diagnostics problem. A unique wall detector design is proposed here which uses a combination of curved collimation, thin scintillator and a fast multi-channel signal processing unit to allow detection of 10-5 alphas per fusion neutron despite the intensive background radiation field involved. An analysis of the shielding of this radiation hardened detector system is presented.

Proposed laser-induced fluorescence method for remote thermometry inturbine engines

Introduction R is under way to measure the temperature of surfaces within operating turbine engines. To supply these measurements, which are necessary for some Air Force programs, current efforts are concentrating on the first-stage rotor blades and stator vanes. These components, positioned just behind the burner, are the most difficult parts of a turbine to measure because they are the hottest and because the leading surfaces of the firststage vanes reflect intense background blackbody radiation from the burning fuel. Currently, the two principal temperature-diagnostic tools are pyrometers and thermocouples. Contact sensors, such as thermocouples, require leads that connect them to datarecording instruments, while optical sensors, such as pyrometers, are remote (noncontact) electric thermometers. Both thermocouples and pyrometers exhibit limitations in turbine-engine applications. Protruding surface-mounted wire thermocouples, which disturb the airflow and heat-transfer characteristics, perturb the temperature at the point being measured. Cutting trenches to flush-mount them changes the structural properties and also perturbs the temperature. Thin-film thermocouples are so small and flat that their influence on temperature is negligible, but they do not adhere well under operating conditions. They also erode and oxidize and are expensive to install. Because they lack a way of scanning, pyrometers can look at only one point in any given experiment geometry and are therefore not suitable for measuring static surfaces. In addition, pyrometers give erroneous readings in the presence of intense background radiation, and their low-temperature limit of about 700°C makes them useful only in hot regions of engines. Both gas centrifuges and turbine engines have hostile internal environments when operating. For our purposes, the principal difference is that the engine runs at high temperatures,

Baffle Design For Earth Radiation Rejection In The Cryogenic Limb-Scanning Interferometer/Radiometer

The function of the cryogenic limb-scanning interferometer/radiometer (CLIR) is to observe infrared emissions of the earth's upper atmosphere from space. The earth's surface is an extended source of intense background radiation with a small angular separation from the desired scene. The CLIR employs an off-axis Gregorian telescope whose primary mirror and baffles are cooled by an open-cycle cryogenic system. A system of specular annular baffles has been designed to minimize both stray light problems and cryogen consumption by retromapping the aperture into itself. Off-axis rays which enter the aperture and strike the baffles are reflected so that they pass out of the aperture again and are not absorbed on cryogenic surfaces. The edge ray principle is used to configure the specular baffle surfaces. The baffle which lies closest to the aperture is an ellipsoid whose foci trace out the circular aperture on revolution about the axis. Its theoretical "ray trace" efficiency is 100 percent. A subsequent baffle has an elliptical cross section whose near focus traces out the central hole in the ellipsoidal baffle and whose far focus traces out the aperture. Its theoretical efficiency is about 90 percent. These baffles reduce the earth radiation heat load on the cryogenic cooler by an order of magnitude, changing it from the dominant cause of cryogen consumption to a relatively small effect. An aperture shield is also desirable to reduce cryogen consumption, stray light, and contamination.

Photon condensation in the big bang cosmology and longitudinal background radiation of the universe

With the assumption of nonzero photon mass the existence of the photon condensate at the early stages of the Universe's expansion is supposed. Evaporation of the condensate leads then to the formation of intensive longitudinal background radiation.