Spectrum Of Emitted Radiation Research Articles

Revealing the Properties of Electrically Driven Optical Antennas via Conductive Atomic Force Microscope.

Light emission from ultracompact electrically driven optical antennas (EDOAs) has garnered significant attention due to its terahertz modulation bandwidth. Typically, the EDOAs are fixed and nonadjustable once fabricated, thus hindering the attempts to investigate the influence of structural geometry on light emission properties. Here, we propose and demonstrate that the EDOAs can be constructed by carefully manipulating the gold-coated tips of atomic force microscopy operated in conductive mode into contact with the optical antennas covered by insulating film, where the position of the tunnel junction on the antenna surface can be controlled with high accuracy and flexibility. Taking gold nanorod antennas covered by HfO2 film as an example, we found that the highest light generation efficiency is obtained when the tunnel junction is located at the shoulder edge of the nanorod antenna, where the bonding dipolar surface plasmon mode in the junction is spectrally and spatially coupled with the longitudinal radiation mode of the EDOAs. Besides, position variation of the tunnel junction on the nanorod surface also strongly influences the far-field radiation angular distribution and emission spectrum. Numerical simulations are in good agreement with the experimental results. Our findings offer fundamental insights into the influence of structural parameters on the light emission performance of EDOAs, thus leading to better design of EDOAs with high light generation efficiency and powerful functionality.

Electron tail suppression and effective collisionality due to synchrotron emission and absorption in mildly relativistic plasmas

Synchrotron radiation losses are a significant cause of concern for high-temperature aneutronic fusion reactions such as proton–Boron 11. The fact that radiation losses occur primarily in the high-energy tail, where the radiation itself has a substantial impact on the electron distribution, necessitates a self-consistent approach to modeling the diffusion and drag induced by synchrotron absorption and emission. Furthermore, an accurate model must account for the fact that the radiation emission spectrum is momentum-dependent, and the plasma opacity is frequency-dependent. Here, we present a simple Fokker–Planck operator, built on a newly solved-for blackbody synchrotron diffusion operator, which captures all relevant features of the synchrotron radiation. Focusing on magnetic mirror fusion plasmas, we show that significant suppression of the electron distribution occurs for relativistic values of the perpendicular electron momentum, which therefore emit much less radiation than predicted under the assumption of a Maxwell–Jüttner distribution.

Contribution of radioactive particles to the post-explosion exposure of atomic bomb survivors implied from their stable chromosome aberration rates.

Even today when nearly 80 years have passed after the atomic bomb (A-bomb) was dropped, there are still debates about the exact doses received by the A-bomb survivors. While initial airborne kerma radiation (or energy spectrum of emitted radiation) can be measured with sufficient accuracy to assess the radiation dose to A-bomb survivors, it is not easy to accurately assess the neutron dose including appropriate weighting of neutron absorbed dose. Particularly, possible post-explosion exposure due to the radioactive particles generated through neutron activation have been almost neglected so far, mainly because of a large uncertainty associated to the behavior of those particles. However, it has been supposed that contribution of such non-initial radiation exposure from the neutron-induced radioactive particles could be significant, according to the findings that the stable chromosomal aberration rates which indicate average whole-body radiation doses were found to be more than 30% higher for those exposed indoors than for those outdoors even at the same initial dose estimated for the Life Span Study. In this Mini Review article, the authors explain that such apparently controversial observations can be reasonably explained by assuming a higher production rate of neutron-induced radioactive particles in the indoor environment near the hypocenter.

First Simulations for the EuAPS Betatron Radiation Source: A Dedicated Radiation Calculation Code

X-ray production through betatron radiation emission from electron bunches is a valuable resource for several research fields. The EuAPS (EuPRAXIA Advanced Photon Sources) project, within the framework of EuPRAXIA, aims to provide 1–10 keV photons (X-rays), developing a compact plasma-based system designed to exploit self-injection processes that occur in the highly nonlinear laser-plasma interaction (LWFA) to drive electron betatron oscillations. Since the emitted radiation spectrum, intensity, angular divergence, and possible coherence strongly depend on the properties of the self-injected beam, accurate preliminary simulations of the process are necessary to evaluate the optimal diagnostic device specifications and to provide an initial estimate of the source’s performance. A dedicated tool for these tasks has been developed; electron trajectories from particle-in-cell (PIC) simulations are currently undergoing numerical analysis through the calculation of retarded fields and spectra for various plasma and laser parameter combinations. The implemented forward approach evaluation of the fields could allow for the integration of the presented scheme into already existing PIC codes. The spectrum calculation is thus performed in detector time, giving a linear complex exponential phase; this feature allows for a semi-analitical Fourier transform evaluation. The code structure and some trajectories analysis results are presented.

Indirect photolysis of cysteine and thiourea in the presence of metal ions in the aquatic environment

In this work are presented the studies on the photochemical transformations of TU (thiourea) and Cys (cysteine) with the addition of Cu(II) or Fe(III) ions to the system. So both thiols, TU, and Cys, have been subjected to induced photolysis with OH radicals, generated during irradiation of H2O2 with different artificial light sources in the presence of the Cu(II) and Fe(III) ions. Based on the results obtained, it was found that when Cu(II) or Fe(III) ions are added to the system, the oxidation rate of the thiols goes up a lot. It has been found that TU and, even more effectively, Cys bind the ions of the studied metals into stable complex compounds. It has been shown that the oxidation rates of the thiols depend also on the irradiation sources' radiation intensity and emission spectrum.

Feasibility Study on the Radiation Dose by Radioactive Magnetic Core-Shell Nanoparticles for Open-Source Brachytherapy.

Treatment of early-stage breast cancer currently includes surgical removal of the tumor and (partial) breast irradiation of the tumor site performed at fractionated dose. Although highly effective, this treatment is exhaustive for both patient and clinic. In this study, the theoretical potential of an alternative treatment combining thermal ablation with low dose rate (LDR) brachytherapy using radioactive magnetic nanoparticles (RMNPs) containing 103-palladium was researched. The radiation dose characteristics and emission spectra of a single RMNP were calculated, and dose distributions of a commercial brachytherapy seed and an RMNP brachytherapy seed were simulated using Geant4 Monte Carlo toolkit. It was found that the RMNP seeds deliver a therapeutic dose similar to currently used commercial seed, while the dose distribution shows a spherical fall off compared to the more inhomogeneous dose distribution of the commercial seed. Changes in shell thickness only changed the dose profile between 2 × 10-4 mm and 3 × 10-4 mm radial distance to the RMNP, not effecting long-range dose. The dose distribution of the RMNP seed is comparable with current commercial brachytherapy seeds, while anisotropy of the dose distribution is reduced. Because this reduces the dependency of the dose distribution on the orientation of the seed, their surgical placement is easier. This supports the feasibility of the clinical application of the proposed novel treatment modality.

Radiation Emitter Classification and Identification Approach Based on Radiation Emission Components

An electronic system generates a large number of intended or unintended electromagnetic radiated emissions in its operating state, which can lead to potential electromagnetic compatibility (EMC) problems. To avoid the impact of these electromagnetic radiation emissions on the surrounding electronic equipment or systems, it is necessary to classify and identify these radiation emitters. In this paper, we proposed a systematic approach for radiation emitter classification and identification based on radiation emission components. Inspired by the basic emission waveform theory (BEWT), the radiation emission data of electronic systems are decomposed into three kinds of radiation emission components, and the different groups of radiation emission data can be classified or identified according to the similarity of these radiation emission components. The radiation emission (RE) spectral data of several kinds of electronic equipment, such as laptops and digital cameras, were used to verify the proposed method. The classification and identification accuracy for data corresponding to different kinds of radiation emission spectra was about 99%, which confirmed the effectiveness of this method.

Spectral investigations of Nd3+:Ba(PO3)2+La2O3 glasses for infrared laser gain media applications

The investigation of the concentration dependent spectroscopic characteristics of Nd3+ ion in Ba(PO3)2+La2O3 (PBaLa) glasses have been carried out. Based on prominent Judd-Ofelt (JO) formalism, the three JO phenomenological quantitative intensity parameters (Ωλ = 2,4,6) were determined by using absorption levels. The very high Ω6 intensity parameter value reveals greater degree of structural distortion of the Nd3+ sites in PBaLa glass. From Ωλ, required radiative characteristics such as radiative emission probability, lifetime (τr), branching ratio (βr) and emission cross-section (σ(λ)) for excited fluorescent levels have been predicted to assess the potentiality of the glasses. The de-excitation (radiative emission) spectra observed for these glasses yield three prominent levels of 4F3/2 → 4I13/2,11/2,9/2 and their related effective bandwidths and de-excitation cross-sections have been quantified. The lifetimes of the 4F3/2 fluorescent state in Nd3+:PBLa for different concentrations (0.1–2.0 mol %) of Nd3+ ion have been determined by exciting with diode laser (808 nm). The quenching of lifetime could be attributed to the enhanced energy transfer phenomenon via cross-relaxation between pairs of the Nd3+ ions. The crucial spectroscopic characteristics that include Ωλ parameters, radiative properties, effective bandwidths, stimulated emission cross-section, gain bandwidth, figure of merit and optical gain of 4F3/2 → 4I11/2 transitions of PBaLaNd1.0 glass are determined which are also compared with other reported 85 Nd3+: glasses which include 63 Nd3+:phosphate glasses. These systematic analysis and critical comparison with similar results reveal that Nd3+:PBaLa glasses with a wide bandwidth of fluorescence can also be useful for optical amplifiers or laser gain media applications.

THz-driven split ring resonator undulator

We propose a short period undulator based on the electromagnetic field pattern in a THz-driven split ring resonator structure. An analytical model is developed that allows us to assess the key performance parameters of the undulator and to estimate the emitted radiation spectrum. Different geometric configurations are compared in detail using numerical simulations. A 100 MeV electron bunch with 5 pC charge is shown to emit narrow band 83 eV photon pulses with a peak brightness of approximately ${10}^{19}\text{ }\mathrm{photons}/(\mathrm{s}\text{ }{\mathrm{mrad}}^{2}\text{ }{\mathrm{mm}}^{2}\text{ }\text{ }0.1%\text{ }\text{ }\mathrm{BW})$ when passing through the 100 mm long undulator with a 1 mm period.

Microdosimetric calculations for radionuclides emitting β and α particles and Auger electrons

This work focuses on the calculation of S-values and radial energy profiles for radionuclides emitting high (Y-90, Sr-89), medium (Re-186, Sm-153) and low-energy (Er-169, Lu-177) β-particles, Auger electrons (In-111, Ga-67, I-123) and α-particles (At-211, Ac-225). Simulations were performed using the EGSnrc and GEANT4-DNA Monte Carlo (MC) codes for a spherical cell geometry. S-values were computed using decay spectra available in literature for Tc-99m and In-111. To investigate the effect on S-value when the same emission spectrum is used in two different MC codes. Internal modules of the MC codes were used to simulate the decay of other radionuclides mentioned above. Radial energy profiles for uniformly distributed radioactive sources in the cell nucleus and cytoplasm were calculated and results were compared with the literature. For S-values calculated using the same emission spectrum, the results showed good agreement with each other and with the literature. Whereas, the S-values calculated using the internal decay data of the MC codes, for instance, for Ga-67 and Y-90, showed discrepancies up to 40%. Radial energy profiles were also different from those reported in the literature. Our results show that well validated radiation emission spectra must be used for such calculations and internal decay spectra of MC codes should be used with caution. The normalized probability density functions must be used to sample points uniformly into spherical volumes and the methodology proposed here can be used to correctly determine radial energy profiles.

Analysis of various electron blocking layers to improve efficiency in green light-emitting diodes

Efficiency of GaN-based green light-emitting diodes with various electron blocking layers has been studied numerically. By employing conventional AlGaN, graded AlGaN, quaternary AlGaInN and ternary AlInN electron blocking layers, performance of each device has been evaluated. The device characteristics presented include carrier transport, radiative recombination rate, electrostatic field, emission spectra and efficiency.

Erratum: Atom and quantum oscillator coupled by the vacuum field: Radiation pattern, emission spectrum, and decay dynamics [Phys. Rev. A 93 , 013804 (2016)

Erratum: Atom and quantum oscillator coupled by the vacuum field: Radiation pattern, emission spectrum, and decay dynamics [Phys. Rev. A <b>93</b> , 013804 (2016)

THz-driven surface plasmon undulator as a compact highly directional narrow band incoherent x-ray source

We propose a short period undulator which is based on the alternating electromagnetic field pattern of THz-driven surface plasmons in a thin conductive layer on a dielectric grating. An approximate analytical model allows to assess the key performance parameters of the undulator and to estimate the emitted radiation spectrum. The specific example of a graphene based undulator is simulated in detail. For a moderate electron beam energy of 100 MeV and a bunch charge of 0.5 pC the 40 mm long undulator is shown to emit narrow band 1 keV x-ray pulses with a peak brightness of approximately $1{0}^{16}\text{ }\text{ }\mathrm{photons}/(\mathrm{s}\text{ }{\mathrm{mrad}}^{2}\text{ }{\mathrm{mm}}^{2}\text{ }0.1%\text{ }\text{ }\mathrm{BW})$. It therefore has potential for a compact and low cost x-ray source.

Investigation of the plasma parameters of a laboratory argon plasma source using a collisional radiative model with the comparison of experimental and simulated spectra

Plasma spectroscopy is a common method for diagnosing the radiative behaviour and predicting the key properties of a plasma. Plasma spectroscopy may be merged with plasma modelling and simulation to perform numerical diagnostics. A new Collisional Radiative (CR) model is developed for argon plasma at low temperature and low pressure. In the developed model, rather than grouping the energy levels into lumped sets, all the energy levels up to a maximum level were modeled for both the argon neutrals and the argon single ions. With the gathered data of collisional and radiative rate coefficients from LANL (Los Alamos National Laboratory) and NIST (National Institute of Standards and Technology), this model calculates the time-varying population densities of 101 atomic and 222 ionic energy levels. The model considers the emissions of 146 Ar-I lines (in 86.68–2397.3 nm range) and 303 Ar-II lines (in 71.8–6985.3 nm range), and gives the simulated spectra over the optical and near-optical region. The simulated radiation emission spectra were then compared with the measured spectra of a laboratory helicon plasma source for the prediction of the plasma parameters such as electron temperature and electron density.

Theoretical and experimental characterization of emission and transmission spectra of Cerenkov radiation generated by 177Lu in tissue.

.Cerenkov radiation (CR) is the emission of UV-vis light generated by the de-excitation of the molecules in the medium, after being polarized by an excited particle traveling faster than the speed of light. When particles travel through tissue with energies greater than 219 keV, CR occurs. Tissues possess a spectral optical window of 600 to 1100 nm. The CR within this range can be useful for quantitative preclinical studies using optical imaging and for the in-vivo evaluation of -radiopharmaceuticals (-particle emitters). The objective of our research was to determine the experimental emission light spectrum of -CR and evaluate its transmission properties in tissue as well as the feasibility to applying CR imaging in the preclinical studies of -radiopharmaceuticals. The theoretical and experimental characterizations of the emission and transmission spectra of -CR in tissue, in the vis-NIR region (350 to 900 nm), were performed using Monte Carlo simulation and UV-vis spectroscopy. Mice -CR images were acquired using a charge-coupled detector camera and were quantitatively analyzed. The results demonstrated good agreement between the theoretical and the experimental -CR emission spectra. Preclinical CR imaging demonstrated that the biokinetics of -radiopharmaceuticals in the main organs of mice can be acquired.

Exoplanetary Monte Carlo radiative transfer with correlated-k – I. Benchmarking transit and emission observables

Abstract Current observational data of exoplanets are providing increasing detail of their 3D atmospheric structures. As characterization efforts expand in scope, the need to develop consistent 3D radiative-transfer methods becomes more pertinent as the complex atmospheric properties of exoplanets are required to be modelled together consistently. We aim to compare the transmission and emission spectra results of a 3D Monte Carlo radiative transfer (MCRT) model to contemporary radiative-transfer suites. We perform several benchmarking tests of an MCRT code, Cloudy Monte Carlo Radiative Transfer (cmcrt), to transmission and emission spectra model output. We add flexibility to the model through the use of k-distribution tables as input opacities. We present a hybrid MCRT and ray tracing methodology for the calculation of transmission spectra with a multiple scattering component. cmcrt compares well to the transmission spectra benchmarks at the 10s of ppm level. Emission spectra benchmarks are consistent to within 10 per cent of the 1D models. We suggest that differences in the benchmark results are likely caused by geometric effects between plane-parallel and spherical models. In a practical application, we post-process a cloudy 3D HD 189733b GCM model and compare to available observational data. Our results suggest the core methodology and algorithms of cmcrt produce consistent results to contemporary radiative transfer suites. 3D MCRT methods are highly suitable for detailed post-processing of cloudy and non-cloudy 1D and 3D exoplanet atmosphere simulations in instances where atmospheric inhomogeneities, significant limb effects/geometry or multiple scattering components are important considerations.

Absorbed dose evaluation at different organs after 131I oral contamination of two Wistar rat models

Iodine-131 (131I) is one of the most frequently used radionuclides for diagnosis and therapy of thyroid diseases. It is administered orally in the treatment of cancer to eliminate the residual postoperative microscopic tumor foci, and the residual normal thyroid tissue for early detection of recurrence [1]. The comparative behavior of 131I concentration into two animalmodels with total and partial thyroid has been investigated in our previous work [2]. The accumulated activities have been measured in fourteen organs. In this study, the mean absorbed doses resulting from 131I accumulated in all organs have been evaluated using RODES software [3, 4]. With this software, mean absorbed doses were calculatedfor selected organs (thyroid, lungs, heart, liver, kidneys, stomach, spleen, large and small intestine, testes, urinary bladder wall) by combining the specific absorbed fractions (SAF) of energy with radiation emission spectra and biokinetic data determined from our previous experimental study [2]. Calculations were based on the 131I photon and electron emissions reported by [5] and SAFs previously calculated by Monte Carlo simulation in the voxel phantom of an adult male rate [3, 4]. The obtained results show high absorbed dosesdeliveredto stomach and lungs for both models compared to other organs. The dose received by the testes and salivary glands is found to be higher in the case of the rat model without thyroid. Conversely, the spleen and bladder wall received lower doses in this latter model compared to those received by the rat model with thyroid. One can also note that the difference in mean absorbed dose received by liver, lungs, heart, and walls of the stomach is not significant between the two rat models.

Influence of Electrical Properties on Radiation and Emission to Pinch Radius Thermal Plasma Device

Plasma focus (PF) generation has advanced the development of high-density, high-temperature plasma that emits intense radiation. The radiation output and emission spectra depend on the operating parameters of the PF device. The ability to focus plasma governs the pinch radius and electrical properties at the truncated end of the PF device. In this study, the simulation system RADPF 5.15 FIB was used to investigate the pinching properties of the neon ion beam generated using an AECS PF-1 device. The pinch radius was the dominant factor affecting the current density produced.

Experimental evidence of quantum radiation reaction in aligned crystals

Quantum radiation reaction is the influence of multiple photon emissions from a charged particle on the particle's dynamics, characterized by a significant energy-momentum loss per emission. Here we report experimental radiation emission spectra from ultrarelativistic positrons in silicon in a regime where quantum radiation reaction effects dominate the positron's dynamics. Our analysis shows that while the widely used quantum approach is overall the best model, it does not completely describe all the data in this regime. Thus, these experimental findings may prompt seeking more generally valid methods to describe quantum radiation reaction. This experiment is a fundamental test of quantum electrodynamics in a regime where the dynamics of charged particles is strongly influenced not only by the external electromagnetic fields but also by the radiation field generated by the charges themselves and where each photon emission may significantly reduce the energy of the charge.

Spectral properties of the accretion discs around rotating black holes

We study the radiation properties of an accretion disc around a rotating black hole. We solve the hydrodynamic equations and calculate the transonic solutions of accretion disc in the presence of shocks. Then we use these solutions to generate the radiation spectrum in the presence of radiative heating and cooling processes. We present the effect of spin parameter of the black hole on the emitted radiation spectrum. In addition, attention has also been paid to the variation in energy spectral index with Kerr parameter and accretion rate. We find that spectral index becomes harder as the spin parameter changes from negative (accretion disc is counter-rotating with respect to the black hole spin) to a positive value. Finally, we compute and compare the spectral characteristics due to a free-fall flow and a transonic flow. We notice significant differences in high energy contributions from these two solutions.