Presence Of Background Radiation Research Articles

Systematic Study of the Inner Structure of Molecular Tori in Nearby U/LIRGs Using Velocity Decomposition of CO Rovibrational Absorption Lines* *This research is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We are honored by and grateful for the opportunity to observe the universe from Maunakea, which has cultural, historical,

Determining the inner structure of the molecular torus around an active galactic nucleus is essential for understanding its formation mechanism. However, spatially resolving the torus is difficult because of its small size. To probe the clump conditions in the torus, we therefore perform the systematic velocity-decomposition analyses of the gaseous 12CO rovibrational absorption lines (v = 0 → 1, ΔJ = ±1) at λ ∼ 4.67 μm observed toward four (ultra)luminous infrared galaxies using the high-resolution (R ∼ 5000–10,000) spectroscopy from the Subaru Telescope. We find that each transition has two to five distinct velocity components with different line-of-sight (LOS) velocities (V LOS ∼ −240 to +100 km s−1) and dispersions (σ V ∼ 15–190 km s−1), i.e., the components (a), (b), ⋯, beginning with the broadest one in each target, indicating that the tori have clumpy structures. By assuming a hydrostatic disk ( σV∝Rrot−0.5 ), we find that the tori has dynamic inner structures, with the innermost component (a) outflowing with velocity ∣V LOS∣ ∼ 160–240 km s−1, and the outer components (b) and (c) outflowing more slowly or infalling with ∣V LOS∣ ≲ 100 km s−1. In addition, we find that the innermost component (a) can be attributed to collisionally excited hot (≳530 K) and dense ( log(nH2/cm−3)≳6 ) clumps, based on the level populations. Conversely, the outer component (b) can be attributed to cold (∼30–140 K) clumps radiatively excited by a far-infrared-to-submillimeter background with a brightness temperature higher than ∼20–400 K. These observational results demonstrate the clumpy and dynamic structure of tori in the presence of background radiation.

Digital radiography by counting photons: innovative solution for testing very thick parts

In 2019 we presented the first prototype of a photon counting detector (PCD) specially designed for the inspection of very thick parts requiring the use of high energy (HE) sources (E > 200keV). HE PCD differs from the standard model by the following characteristics: 1) Photoconductor CdTe active layer thickness optimized for HE, with about 30% increased detection efficiency; 2) Completely renewed ASIC allowing selection of energy threshold up to 1300keV. Modification 2) allows to reduce scattered radiation when using gamma sources such as Iridium 192 and Cobalt 60; or pulsed sources like linear accelerators and betatrons. The object-contrast results from this considerably improved. Image quality is comparable to, if not better than, film. We present energy threshold optimization study and performance evaluation results in terms of ISO 19232 IQI (wire and hole), signal-to-noise ratio, and spatial resolution (via duplex IQI) according to ISO 17636_2 (class B). Focus is given to HE PCD/film comparison, which was carried out by means of mock-ups containing artificial and/or real flaws; and, in 2020, for the first time in a nuclear power plant site, for the examination of primary circuit dissimilar welds. Photons energy thresholding successfully addressed also the presence of background radiation. The latter represented 2% of counted photons, while with film, background was responsible of 13% of optical density.

Analog of electromagnetically induced transparency in metasurfaces composed of identical dielectric disks

An analog of electromagnetically induced transparency was revealed in metasurfaces (MSs), composed from identical dielectric resonators of simple cylindrical shapes. It was detected in numerical experiments at optical and microwave frequencies and confirmed by real experiments in the microwave range. The main specific of the observed phenomenon was its appearance at frequencies of electric dipolar resonances (EDRs) in MS elements, when total reflection of incident waves instead of transmission was expected. Investigations of electric field distributions in MSs allowed for detecting several Fano resonances caused by interaction between background radiation defined by incident waves, and radiation produced by oscillations of resonance fields in dielectric particles. The characteristics for EDR changes in phases of resonance oscillations by π radians were found controlling the transitions from constructive to destructive interference between participating wave processes. The onset of destructive interference was marked by sharp jumps by π radians in the spectra of signal phases. Performed analysis revealed that zero signals at Fano resonances, observed in the gaps between resonators, arranged along the electric field direction, could serve as indicators of realizing the conditions necessary for the transparency of MSs. These conditions included the elimination of the presence of background radiation and thus of interaction between trespassing waves and MSs.

Bounce and Stability in the Early Cosmology with Anomaly-Induced Corrections

An extremely fast exponential expansion of the Universe is typical for the stable version of the inflationary model, based on the anomaly-induced action of gravity. The total amount of exponential e-folds could be very large, before the transition to the unstable version and the beginning of the Starobinsky inflation. Thus, the stable exponential expansion can be seen as a pre-inflationary semiclassical cosmological solution. We explore whether this stable phase could follow after the bounce, subsequent to the contraction of the Universe. Extending the previous consideration of the bounce, we explore both stable expansion and the bounce solutions in the models with non-zero cosmological constant and the presence of background radiation. The critical part of the analysis concerns stability for small perturbations of the Hubble parameter. It is shown that the stability is possible for the variations in the bounce region, but not in the sufficiently distant past in the contraction phase.

WE‐D‐BRF‐03: Proton Beam Range Verification with a Single Prompt Gamma‐Ray Detector

Purpose:To present an experimental study of a novel range verification method for scanned and scattered proton beams.Methods:A detection system consisting of an actively shielded lanthanum(III)bromide scintillator and a one‐sided lead collimator was used to measure prompt gamma‐rays emitted during the delivery of proton beams to a water phantom and an anthropomorphic head phantom. The residual proton range at the collimator position was determined by comparing gamma‐ray intensities while the proton energy was modulated to the distal end of the target. We used a clinical field to deliver a 50 cGy dose to a 12 cm diameter target in the water phantom and to a 175 cc tumor‐shaped target in the head phantom. The detector signals were acquired with a custom data acquisition system enabling energy and time‐of‐flight discrimination of prompt gamma‐rays.Results:Range deviations were detected with a statistical accuracy of ± 0.2 mm and ± 1.4 mm at 90% confidence level, respectively for the water and head phantom. We obtained a time resolution of 1 ns FWHM and an energy resolution < 2% FWHM for the main gamma lines from proton‐induced nuclear reactions with carbon and oxygen. This allowed for an accurate separation of the prompt gamma‐rays from neutron‐induced background.Conclusion:Proton range deviations can be detected with millimeter accuracy using a single prompt gamma‐ray measurement point acquired during the delivery of a few proton energy layers to the distal part of the target. The method is also feasible in the presence of background radiation from passively scattered proton beam delivery.

Emulating Nuclear Emissions With a Pulsed Laser

This paper presents an approach to emulate the Poisson process observed by a sensor when subject to low levels of radiation, motivated by the problem of detecting a weak source in the presence of background radiation. We construct a physical emulation of this process to serve as a means of experimentation for various detection models involving mobile sensor networks. A pulsing laser emulates the nuclear emission, and a rotating mirror deflects the pulses in a random direction. The degree to which the proposed emulation process matches actual radiation measurement results is assessed experimentally, and the utility of the device is demonstrated and compared against conventional methods in a simple detection scenario.

SU‐E‐T‐443: Measuring Prompt Gamma Emission During Passive Beam Proton Radiotherapy for Real Time Treatment Verification

Purpose: Recent studies demonstrate the feasibility of prompt‐gamma imaging for pencil beam proton therapy. In contrast to passive‐scatter proton radiotherapy, the existence of high background signal from secondary radiation produced by protons in the beam line components makes the detection of prompt‐gammas challenging. Our primary goal is to produce a more complete measurement of the prompt‐gammas produced in tissue for clinical treatment conditions. Methods: The proton treatment facility at iThemba Labs was studied in detail and all the nozzle components that interact with the proton beam were built and positioned at the locations specified by the manufacturer using the Geant4 Monte Carlo toolkit. The treatment nozzle was validated against depth dose and lateral profiles in a water phantom at therapeutic energies. The model included NaI detectors of different dimensions to detect the prompt‐gamma spectra, and standard gamma emitting sources in the energy range 0.661 to 4.438 MeV were used to determine the Gaussian broadening parameters of the detectors. Finally, prompt‐gamma spectra from the tissue phantom were simulated over a range of energies in order to make comparisons with the experimental spectra currently being measured. Results: The prompt‐gamma energy spectra show prominent peaks caused by collisions of proton with nuclei in the tissue phantom. Single and double escape peaks of 4.44 MeV were clearly seen, while the 6.129 MeV peak was unresolved due to the Doppler broadening effect, peaks at 6.916 and 7.115 MeV were not observed, but the single and double escape peaks of 6.129 MeV were visible. Conclusion: Our study confirms the feasibility of prompt‐gamma imaging during passive proton radiotherapy to assist for on‐line treatment verification. The energy range from 3.0 MeV to 5.0 MeV is a suitable candidate for further investigation and the presence of background radiation can be minimized by introducing proper shielding and collimation.

The effect of energy resolution on the extraction of information content from gamma-ray spectra

Abstract Rapid unambiguous identification of illicit radioactive materials is a matter of international concern that has yet to be fully attained. This is particularly true for shielded fissile materials in the presence of background radiation and routinely encountered benign radionuclides. We present a systematic treatment of the effect of detector resolution on the identification of nuclides in simple and complex shielded γ-ray spectra. Case studies of some problematic spectra with 1000 counts suggest that, at moderate count rates, near-unambiguous identification (

Entanglement transfer through the turbulent atmosphere

The propagation of polarization-entangled states of light through fluctuating loss channels in the turbulent atmosphere is studied, including the situation of strong losses. We consider violations of Bell inequalities by light, emitted by a parametric down-conversion source, after transmission through the turbulent atmosphere. It is shown by analytical calculations, that in the presence of background radiation and dark counts, fluctuating loss channels may preserve entanglement properties of light even better than standard loss channels, when postselected measurements are applied.

Dynamics of moduli and gaugino condensates in an expanding universe

We study dynamical moduli stabilization driven by gaugino condensation in supergravity. In the presenceof background radiation, there exists a region of initial conditions leading to successful stabilization.We point out that most of the allowed region corresponds to initial Hubble rate H close to the scale ofcondensation Λ, which is the natural cutoff of the effective theory. We first show thatincluding the condensate dynamics sets a strong bound on the initial conditions. We then find that(complete) decoupling of the condensate happens at H about two orders of magnitude below Λ.This bound implies that in the usual scenario with the condensate integrated out, only the vicinity ofthe minimum leads to stabilization. Finally, we discuss the effects of thermal corrections.

LDPC-Coded $M$-ary PSK Optical Coherent State Quantum Communication

This paper addresses two important problems of interest for deep-space optical communications, quantum inter-chip/intra-chip optical communications and quantum-key distribution: 1) the problem of coded <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary phase-shift keying optical coherent-state quantum communication in the absence of background radiation, and 2) the problem of coded binary coherent state communication in the presence of background radiation. In both cases large girth low-density parity-check (LDPC) codes are used as channel codes. With girth-10 LDPC-code of rate 0.8 and BPSK, the bit-error ratio of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> can be achieved for average number of signal photons of 0.73, resulting in net-effective coding gain of 7.63 dB.

LDPC-Coded Optical Coherent State Quantum Communications

The problem of communication using optical coherent quantum states, in the presence of background radiation, is considered. Two modulation formats are studied, on-off keying (OOK) and M-ary pulse-position modulation (PPM). The bit-error-rate performance improvement due to low-density parity-check coding is reported. For OOK, it is assumed that the coherent state signal has a random phase. For an average number of noise photons N = 0.1, the required number of signal photons per information bit is six in the case of coded quantum OOK. For the same level of noise (N = 0.1) and assuming that signal phase is known, coded 16-ary PPM requires only 1.21 of signal photons per information bit.

The LHCb triple-GEM detector for the inner region of the first station of the muon system: construction and module-0 performance

A triple-gas electron multiplier (GEM) detector, operated with the gas mixture Ar/CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (45/15/40), is going to equip station M1, region R1 of the LHCb muon system. A Module-0 of this detector, with full area (20 cmtimes24 cm) GEM foils, was recently built and tested. In this paper, new measurements of efficiency and pad multiplicity are presented. These new measurements were very important to select of the final pad board configuration. The sensitivity to discharges is a very important issue in this type of detector; we discuss here new measurements of the maximum number of discharges that a triple-GEM detector can stand before breakdown, and we show that detector operation in LHCb is safe from this point of view. We also discuss new measurements of the time performance of the detector in the presence of background radiation, indicating that no significant deterioration of the performances is expected in the LHCb environment

Comparison between orthogonal subspace projection and background subtraction techniques applied to remote-sensing data

The basic measurement equation r = B + alphad + n is solved for alpha (the weight or abundance of the spectral target vector d) by two methods: (a) by subtracting the stochastic spectral background vector B from the spectral measurement's vector r (subtraction solution) and (b) by orthogonal subspace projection (OSP) of the measurements to a subspace orthogonal to B (the OSP solution). The different geometry of the two solutions and in particular the geometry of the noise vector n is explored. The angular distribution of the noise angle between B and n is the key factor for determining and predicting which solution is better. When the noise-angle distribution is uniform, the subtraction solution is always superior regardless of the orientation of the spectral target vector d. When the noise is more concentrated in the direction orthogonal to B, the OSP solution becomes better (as expected). Simulations and one-dimensional hyperspectral measurements of vapor concentration in the presence of background radiation and noise are given to illustrate these two solutions.

Optical array receiver for communication through atmospheric turbulence

An optical array receiver concept is developed and analyzed. It is shown that for ground-based reception, the number of array elements can be increased without incurring performance degradation, provided the array telescope diameters exceed the coherence-length of the atmosphere. Maximum likelihood detection of turbulence-degraded signal fields is developed for the case of pulse-position modulated signals observed in the presence of background radiation. Performance of optical array receivers is compared to single-aperture receivers with diameters ranging from 4 to 8 m, both in the presence of turbulence and in a turbulence-free environment such as space. It is shown that in the absence of atmospheric turbulence, single-aperture receivers outperform receiver arrays when significant background radiation is present. However, it is also demonstrated that for ground-based reception of deep-space signals, the number of array elements can be as great as several thousand without incurring any performance degradation relative to a large single-aperture receiver.

Evaluation of a fast neutron coincidence counter for the measurements of uranium samples

A fast neutron coincidence counter using BC454/BGO phoswich detectors has been evaluated for the purpose of rapid verification measurements of uranium items. This counter uses custom electronics to identify and count coincidence neutrons in the presence of background radiation. Measurements of uranium standards were performed to evaluate the counter. This counter is successful in measuring uranium items but has a low efficiency that results in minimal improvement over current technology. An optimized counter can be built with better performance capabilities, but it is recommended that newer technologies be used instead.

Constraints on the Dynamics of Electron-Positron Jets in Active Galactic Nuclei

view Abstract Citations (9) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Constraints on the Dynamics of Electron-Positron Jets in Active Galactic Nuclei Levinson, Amir Abstract The bulk acceleration of electron-positron jets in the presence of background radiation is examined, taking account of the conversion of electromagnetic energy into pairs and X-rays through the interaction of the cold e^+/-^ beam with the ambient radiation. It is shown that in order to avoid catastrophic radiative drag, the fraction of total jet power carried by pairs must not exceed the ratio of radiative cooling time of the outflowing pairs by soft photons to dynamical time. This requirement is automatically satisfied, owing to rapid pair annihilation, if the total jet power is not much smaller than the fraction of UV/soft X-ray luminosity intercepted by the inner jet, as measured in the comoving frame. It is found that the flow undergoes a sharp transition whereby the Poynting flux is converted into pairs and beamed X-rays, when the bulk Lorentz factor exceeds the corresponding threshold energy above which the pair-production opacity becomes larger than unity. When the scattered spectrum is sufficiently flat, such that the cooling rate is dominated by hard photons from near its upper cutoff, the Poynting flux is converted mostly into beamed pairs. However, if the scattered spectrum is steep at low energies, like those observed in radio-quiet sources, there is catastrophic X-ray production. The implications for jets from blazars are considered, and several ways in which X-ray overproduction may he avoided are discussed. Publication: The Astrophysical Journal Pub Date: August 1996 DOI: 10.1086/177632 Bibcode: 1996ApJ...467..546L Keywords: ELEMENTARY PARTICLES; GALAXIES: ACTIVE; GALAXIES: JETS; GALAXIES: NUCLEI; X-RAYS: GALAXIES full text sources ADS | data products SIMBAD (2)

Maximum heterodyne efficiency of optical heterodyne detection in the presence of background radiation

Maximum heterodyne efficiency is obtained for an optical heterodyne detection system in the presence of background radiation. When the local oscillator (LO) power is limited, the signal-to-noise ratio in the output is degraded from that of quantum-noise-limited detection by the background radiation noise. To reduce it, an aperture is used in front of the detector. The optimum incidence conditions of the signal and the corresponding maximum heterodyne efficiency are obtained numerically assuming that the signal and the LO fields are determinable and have Gaussian amplitude distributions. The spontaneous emission from the laser amplifier located just in front of the system is taken into account as the background radiation.

Generation-recombination noise in extrinsic photoconductive detectors

A theory of generation–recombination noise is presented and applied to the analysis of the performance limitations of extrinsic photoconductive detectors. The theory takes account both of the photoinduced generation of carriers and of thermal generation that is due to the finite temperature of the detector. Explicit formulas are derived that relate the detector response time, responsivity, and noise equivalent power to the material properties of the photo-conductor (such as the presence of compensating impurities) and to the detector’s operating conditions, such as its temperature and the presence of background radiation. The detector’s performance is shown to degrade at high background levels because of saturation effects.

Detection of Coherent Optical Signals in Generalized Gaussian Noise

Results of receiver performance for the detection of a coherent light signal in the presence of background radiation are obtained and compared for two different types of background noise: a Gaussian field and a Gaussian field whose complex analytic signal is not circularly symmetric. It is pointed out that the randomness in the noise radiation does not significantly diminish the probability of correct detection.