Radiative recombination data for tungsten ions: III.  W{sup 14+}–W{sup 23+}

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

Trzhaskovskaya, M.B., E-mail: Trzhask@MT5605.spb.edu; Nikulin, V.K.

2014-09-15

This paper completes the cycle of our calculations of the radiative recombination and photoionization data for tungsten ions. Presented here are the photoionization and radiative recombination cross sections, radiative recombination rate coefficients, and radiated power loss rate coefficients for ten tungsten impurity ions from W{sup 14+} to W{sup 23+}. These data are required in diagnostics and modeling fusion plasmas studied in such devices as ITER, ASDEX Upgrade, and EBIT. Partial photoionization cross sections have been fitted by an analytical expression with five fit parameters tabulated here. Total radiative recombination cross sections are presented in the electron energy range from 1 eVmore » to ∼80 keV. Radiative recombination rates and radiated power loss rates are given in the temperature range from 10{sup 4}  K to 10{sup 9}  K. Calculations have been performed on the basis of the fully relativistic treatment of photoionization and radiative recombination taking into account all significant multipoles of the radiative field. Electron wave functions have been obtained by the Dirac–Fock method with the proper consideration of the electron exchange. The relativistic Maxwell–Jüttner distribution of continuum electrons has been used in calculations of radiative recombination rates and radiated power loss rates. This decreases values of the rates noticeably at a high temperature as compared to the usual non-relativistic Maxwell–Boltzmann distribution. -- Highlights: •Radiative recombination data for ten tungsten ions W{sup 14+}–W{sup 23+} are presented. •Photoionization cross sections are also given. •Calculations are fully relativistic including all multipoles of the radiative field. •We use the Dirac–Fock method to obtain the electron wave functions. •The data are required for diagnostics and modeling fusion plasmas studied in ITER.« less

Absorption cross sections of some atmospheric molecules for resonantly scattered O I 1304-A radiation

NASA Technical Reports Server (NTRS)

Starr, W. L.

1976-01-01

Absorption cross sections for O2, N2, CO2, CH4, N2O, and CO have been measured at each of the lines of the atomic oxygen triplet at 1302, 1305, and 1306 A. Radiation resonantly scattered from oxygen atoms at a temperature of about 300 K was used for the line source. Absorber temperatures were also near 300 K. Direct application of the Lambert-Beer absorption equation yielded pressure-dependent cross sections for carbon monoxide at each line of the O I triplet. Reasons for this apparent dependence are presented and discussed.

Determination of Important Nuclear Fragmentation Processes for Human Space Radiation Protection

NASA Technical Reports Server (NTRS)

Lin, Zi-Wei

2007-01-01

We present a semi-analytical method to determine which partial cross sections of nuclear fragmentations most affect the shielded dose equivalent due to exposure to galactic cosmic rays. The cross sections thus determined will require more theoretical and/or experimental studies in order for us to better predict, reduce and mitigate the radiation exposure in human space explorations.

A factorization approach to next-to-leading-power threshold logarithms

NASA Astrophysics Data System (ADS)

Bonocore, D.; Laenen, E.; Magnea, L.; Melville, S.; Vernazza, L.; White, C. D.

2015-06-01

Threshold logarithms become dominant in partonic cross sections when the selected final state forces gluon radiation to be soft or collinear. Such radiation factorizes at the level of scattering amplitudes, and this leads to the resummation of threshold logarithms which appear at leading power in the threshold variable. In this paper, we consider the extension of this factorization to include effects suppressed by a single power of the threshold variable. Building upon the Low-Burnett-Kroll-Del Duca (LBKD) theorem, we propose a decomposition of radiative amplitudes into universal building blocks, which contain all effects ultimately responsible for next-to-leading-power (NLP) threshold logarithms in hadronic cross sections for electroweak annihilation processes. In particular, we provide a NLO evaluation of the radiative jet function, responsible for the interference of next-to-soft and collinear effects in these cross sections. As a test, using our expression for the amplitude, we reproduce all abelian-like NLP threshold logarithms in the NNLO Drell-Yan cross section, including the interplay of real and virtual emissions. Our results are a significant step towards developing a generally applicable resummation formalism for NLP threshold effects, and illustrate the breakdown of next-to-soft theorems for gauge theory amplitudes at loop level.

Molecular Data for a Biochemical Model of DNA Radiation Damage: Electron Impact Ionization and Dissociative Ionization of DNA Bases and Sugar-Phosphate Backbone

NASA Technical Reports Server (NTRS)

Dateo, Christopher E.; Fletcher, Graham D.

2004-01-01

As part of the database for building up a biochemical model of DNA radiation damage, electron impact ionization cross sections of sugar-phosphate backbone and DNA bases have been calculated using the improved binary-encounter dipole (iBED) model. It is found that the total ionization cross sections of C3'- and C5'-deoxyribose-phospate, two conformers of the sugar-phosphate backbone, are close to each other. Furthermore, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3'- and C5'-deoxyribose-phospate cross sections, differing by less than 10%. Of the four DNA bases, the ionization cross section of guanine is the largest, then in decreasing order, adenine, thymine, and cytosine. The order is in accordance with the known propensity of oxidation of the bases by ionizing radiation. Dissociative ionization (DI), a process that both ionizes and dissociates a molecule, is investigated for cytosine. The DI cross section for the formation of H and (cytosine-Hl)(+), with the cytosine ion losing H at the 1 position, is also reported. The threshold of this process is calculated to be 17.1 eV. Detailed analysis of ionization products such as in DI is important to trace the sequential steps in the biochemical process of DNA damage.

Microcircuit radiation effects databank

NASA Technical Reports Server (NTRS)

1983-01-01

This databank is the collation of radiation test data submitted by many testers and serves as a reference for engineers who are concerned with and have some knowledge of the effects of the natural radiation environment on microcircuits. It contains radiation sensitivity results from ground tests and is divided into two sections. Section A lists total dose damage information, and section B lists single event upset cross sections, I.E., the probability of a soft error (bit flip) or of a hard error (latchup).

Projectile and Lab Frame Differential Cross Sections for Electromagnetic Dissociation

NASA Technical Reports Server (NTRS)

Norbury, John W.; Adamczyk, Anne; Dick, Frank

2008-01-01

Differential cross sections for electromagnetic dissociation in nuclear collisions are calculated for the first time. In order to be useful for three - dimensional transport codes, these cross sections have been calculated in both the projectile and lab frames. The formulas for these cross sections are such that they can be immediately used in space radiation transport codes. Only a limited amount of data exists, but the comparison between theory and experiment is good.

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

Aguado, Alfredo; Roncero, Octavio; Zanchet, Alexandre

The impact of the photodissociation of HCN and HNC isomers is analyzed in different astrophysical environments. For this purpose, the individual photodissociation cross sections of HCN and HNC isomers have been calculated in the 7–13.6 eV photon energy range for a temperature of 10 K. These calculations are based on the ab initio calculation of three-dimensional adiabatic potential energy surfaces of the 21 lower electronic states. The cross sections are then obtained using a quantum wave packet calculation of the rotational transitions needed to simulate a rotational temperature of 10 K. The cross section calculated for HCN shows significant differencesmore » with respect to the experimental one, and this is attributed to the need to consider non-adiabatic transitions. Ratios between the photodissociation rates of HCN and HNC under different ultraviolet radiation fields have been computed by renormalizing the rates to the experimental value. It is found that HNC is photodissociated faster than HCN by a factor of 2.2 for the local interstellar radiation field and 9.2 for the solar radiation field, at 1 au. We conclude that to properly describe the HNC/HCN abundance ratio in astronomical environments illuminated by an intense ultraviolet radiation field, it is necessary to use different photodissociation rates for each of the two isomers, which are obtained by integrating the product of the photodissociation cross sections and ultraviolet radiation field over the relevant wavelength range.« less

Absolute absorption cross sections of ozone at 300 K, 228 K and 195 K in the wavelength region 185-240 nm

NASA Technical Reports Server (NTRS)

Yoshino, K.; Parkinson, W. H.; Freeman, D. E.

1992-01-01

An account is given of progress of work on absorption cross section measurements of ozone at 300 K, 228 K and 195 K in the wavelength region 185-240 nm. In this wavelength region, the penetration of solar radiation into the Earth's atmosphere is controlled by O2 and O3. The transmitted radiation is available to dissociate trace species such as halocarbons and nitrous oxide. We have recently measured absolute absorption cross sections of O3 in the wavelength region 240-350 nm (Freeman et al., 1985; Yoshino et al., 1988). We apply these proven techniques to the determination of the absorption cross section of O3 at 300 K, 228 K and 195 K throughout the wavelength region 185-240 nm. A paper titled 'Absolute Absorption Cross Section Measurements of Ozone in the Wavelength Region 185-254 nm and the Temperature Dependence' has been submitted for publication in the Journal of Geophysical Research.

Meson Production and Space Radiation

NASA Astrophysics Data System (ADS)

Norbury, John; Blattnig, Steve; Norman, Ryan; Aghara, Sukesh

Protecting astronauts from the harmful effects of space radiation is an important priority for long duration space flight. The National Council on Radiation Protection (NCRP) has recently recommended that pion and other mesons should be included in space radiation transport codes, especially in connection with the Martian atmosphere. In an interesting accident of nature, the galactic cosmic ray spectrum has its peak intensity near the pion production threshold. The Boltzmann transport equation is structured in such a way that particle production cross sec-tions are multiplied by particle flux. Therefore, the peak of the incident flux of the galactic cosmic ray spectrum is more important than other regions of the spectrum and cross sections near the peak are enhanced. This happens with pion cross sections. The MCNPX Monte-Carlo transport code now has the capability of transporting heavy ions, and by using a galactic cosmic ray spectrum as input, recent work has shown that pions contribute about twenty percent of the dose from galactic cosmic rays behind a shield of 20 g/cm2 aluminum and 30 g/cm2 water. It is therefore important to include pion and other hadron production in transport codes designed for space radiation studies, such as HZETRN. The status of experimental hadron production data for energies relevant to space radiation will be reviewed, as well as the predictive capa-bilities of current theoretical hadron production cross section and space radiation transport models. Charged pions decay into muons and neutrinos, and neutral pions decay into photons. An electromagnetic cascade is produced as these particles build up in a material. The cascade and transport of pions, muons, electrons and photons will be discussed as they relate to space radiation. The importance of other hadrons, such as kaons, eta mesons and antiprotons will be considered as well. Efficient methods for calculating cross sections for meson production in nucleon-nucleon and nucleus-nucleus reactions will be presented. The NCRP has also recom-mended that more attention should be paid to neutron and light ion transport. The coupling of neutrons, light ions, mesons and other hadrons will be discussed.

Final state interactions in single- and multiparticle inclusive cross sections for hadronic collisions

NASA Astrophysics Data System (ADS)

Mitov, Alexander; Sterman, George

2012-12-01

We study the role of low momentum transfer (soft) interactions between high transverse momentum heavy particles and beam remnants (spectators) in hadronic collisions. Such final state interactions are power suppressed for single-particle inclusive cross sections whenever that particle is accompanied by a recoiling high-pT partner whose momentum is not fixed. An example is the single-top inclusive cross section in top-pair production. Final state soft interactions in multiparticle inclusive cross sections, including transverse momentum distributions, however, produce leading-power corrections in the absence of hard recoiling radiation. Nonperturbative corrections due to scattering from spectators are generically suppressed by powers of Λ/pT', where Λ is a hadronic scale and pT' is the largest transverse momentum of radiation recoiling against the particles whose momenta are observed.

Nuclear model calculations and their role in space radiation research

NASA Technical Reports Server (NTRS)

Townsend, L. W.; Cucinotta, F. A.; Heilbronn, L. H.

2002-01-01

Proper assessments of spacecraft shielding requirements and concomitant estimates of risk to spacecraft crews from energetic space radiation requires accurate, quantitative methods of characterizing the compositional changes in these radiation fields as they pass through thick absorbers. These quantitative methods are also needed for characterizing accelerator beams used in space radiobiology studies. Because of the impracticality/impossibility of measuring these altered radiation fields inside critical internal body organs of biological test specimens and humans, computational methods rather than direct measurements must be used. Since composition changes in the fields arise from nuclear interaction processes (elastic, inelastic and breakup), knowledge of the appropriate cross sections and spectra must be available. Experiments alone cannot provide the necessary cross section and secondary particle (neutron and charged particle) spectral data because of the large number of nuclear species and wide range of energies involved in space radiation research. Hence, nuclear models are needed. In this paper current methods of predicting total and absorption cross sections and secondary particle (neutrons and ions) yields and spectra for space radiation protection analyses are reviewed. Model shortcomings are discussed and future needs presented. c2002 COSPAR. Published by Elsevier Science Ltd. All right reserved.

ARTICLES: Variation of the absorption cross section of high-power infrared laser radiation in homologous series of CnH2n+1OH molecules

NASA Astrophysics Data System (ADS)

Bagratashvili, Viktor N.; Brodskaya, E. A.; Vereshchagina, Lyudmila N.; Kuz'min, M. V.; Osmanov, R. R.; Putilin, F. N.; Stuchebryukhov, A. A.

1984-11-01

An experimental investigation was made of variation of the characteristics of infrared multiphoton absorption in a homologous series of CnH2n+1OH alcohols (n = 1-5) excited with CO2 laser pulses. The dependences of the energy absorbed by the molecules on the frequency and energy density of laser radiation were determined by the optoacoustic method. It was found that the multiphoton absorption cross section decreases on increase in the radiation energy density at a rate which becomes slower on increase in the molecular size. A model is proposed for multiphoton excitation of molecules in a homologous series. This model is based on an analysis of a resonant mode interacting with the infrared radiation field and coupled to a reservoir of modes that do not interact with the field. The model predicts correctly the change in the multiphoton absorption cross section on increase in the number of the degrees of freedom of a molecule.

Measurement of 173Lu(n,γ) Cross Sections at DANCE

NASA Astrophysics Data System (ADS)

Roig, O.; Theroine, C.; Ebran, A.; Méot, V.; Bond, E. M.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Nortier, F. M.; O'Donnell, J. M.; Rundberg, R. S.; Taylor, W. A.; Ullmann, J. L.; Vieira, D. J.

2014-05-01

A highly gamma-radioactive target, 3.7 GBq, of 173Lu isotope was placed inside the DANCE array (Detector for Advanced Neutron Capture Experiments) at Los Alamos to study the radiative neutron capture on an unstable isotope. The 173Lu element was produced by naturalHf(p,xn) reactions following by beta-decays at the Isotope Production Facility (IPF). Measurements of radiative neutron capture cross section on 173Lu were achieved at the Los Alamos Neutron Science Center (LANSCE) spallation neutron source facility over the neutron energy range from thermal up to 1 keV. A special configuration was necessary to perform the experiment using the DANCE [1] array due to the high gamma activity of the target. We will report on the target production, the experiment and the results obtained for the radiative neutron capture on 173Lu. The radiative capture cross section was obtained for the first time on this unstable nucleus. Some resonances have been characterized. A comparison with a recent data evaluation is presented.

Proton-Nucleus Elastic Cross Sections Using Two-Body In-Medium Scattering Amplitudes

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, John W.; Cucinotta, Francis A.

2001-01-01

Recently, a method was developed of extracting nucleon-nucleon (NN) cross sections in the medium directly from experiment. The in-medium NN cross sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the Langley Research Center. The ratio of the real to the imaginary part of the two-body scattering amplitude in the medium was investigated. These ratios are used in combination with the in-medium NN cross sections to calculate elastic proton-nucleus cross sections. The agreement is excellent with the available experimental data. These cross sections are needed for the radiation risk assessment of space missions.

Algorithm for Surface of Translation Attached Radiators (A-STAR). Volume 1: Formulation of the analysis

NASA Astrophysics Data System (ADS)

Medgyesimitschang, L. N.; Putnam, J. M.

1982-05-01

A general analytical formulation, based on the method of moments (MM) is described for solving electromagnetic problems associated with off-surface (wire) and aperture radiators on finite-length cylinders of arbitrary cross section, denoted in this report as bodies of translation (BOT). This class of bodies can be used to model structures with noncircular cross sections such as wings, fins and aircraft fuselages.

Risk cross sections and their application to risk estimation in the galactic cosmic-ray environment

NASA Technical Reports Server (NTRS)

Curtis, S. B.; Nealy, J. E.; Wilson, J. W.; Chatterjee, A. (Principal Investigator)

1995-01-01

Radiation risk cross sections (i.e. risks per particle fluence) are discussed in the context of estimating the risk of radiation-induced cancer on long-term space flights from the galactic cosmic radiation outside the confines of the earth's magnetic field. Such quantities are useful for handling effects not seen after low-LET radiation. Since appropriate cross-section functions for cancer induction for each particle species are not yet available, the conventional quality factor is used as an approximation to obtain numerical results for risks of excess cancer mortality. Risks are obtained for seven of the most radiosensitive organs as determined by the ICRP [stomach, colon, lung, bone marrow (BFO), bladder, esophagus and breast], beneath 10 g/cm2 aluminum shielding at solar minimum. Spectra are obtained for excess relative risk for each cancer per LET interval by calculating the average fluence-LET spectrum for the organ and converting to risk by multiplying by a factor proportional to R gamma L Q(L) before integrating over L, the unrestricted LET. Here R gamma is the risk coefficient for low-LET radiation (excess relative mortality per Sv) for the particular organ in question. The total risks of excess cancer mortality obtained are 1.3 and 1.1% to female and male crew, respectively, for a 1-year exposure at solar minimum. Uncertainties in these values are estimated to range between factors of 4 and 15 and are dominated by the biological uncertainties in the risk coefficients for low-LET radiation and in the LET (or energy) dependence of the risk cross sections (as approximated by the quality factor). The direct substitution of appropriate risk cross sections will eventually circumvent entirely the need to calculate, measure or use absorbed dose, equivalent dose and quality factor for such a high-energy charged-particle environment.

Knowledge deficiency of work-related radiation hazards associated with psychological distress among orthopedic surgeons: A cross-sectional study.

PubMed

Fan, Guoxin; Wang, Yueye; Guo, Changfeng; Lei, Xuefeng; He, Shisheng

2017-05-01

Knowledge and concern degree about work-related radiation hazards remained unknown among orthopedic surgeons. The aim of the cross-sectional study is to investigate whether the knowledge degree of work-related radiation is associated with psychological distress among orthopedic surgeons. This cross-sectional study sent electronic questionnaire via WeChat to orthopedic surgeons nationwide. Concern and knowing degree over radiation exposure was evaluated by a single self-reported question. Professional evaluation of concern degree was reflected by general psychological distress, which was assessed with the Kessler 10 scale (K10) and depressive symptoms with the Center for Epidemiologic Studies Depression Scale (CES-D). Only 43.23% (115/266) respondents knew well about radiation and a total of 78.20% (208/266) respondents considered radiation exposure as a great concern. Among those who reported concerns about radiation exposure, a total of 57.69% (120/208) respondents reported knowing little about radiation. Respondents who reported concerns over radiation exposure were significantly associated with higher scores on CES-D and K10 (P < .05). Among respondents who reported concerns over radiation exposure, those who have fewer knowledge about radiation, had higher CES-D and K10 scores than those who knew well about radiation (P < .05). Among respondents who reported no concerns over radiation exposure, those who knew little about radiation still had higher CES-D and K10 scores (P < .05). Fewer radiation knowledge tends to induce more radiation concerns associated with higher psychological distress in orthopedic surgeons. Radiation knowledge should be enhanced for surgeons who daily work with radiation-related fluoroscopy.

Comparison of the effect of soft-core potentials and Coulombic potentials on bremsstrahlung during laser matter interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi R.; Becker, Valerie R.; Barrington, Kasey; Thurston, Jeremy; Ramunno, Lora; Ackad, Edward

2018-04-01

An intense, short laser pulse incident on rare-gas clusters can produce nano-plasmas containing energetic electrons. As these electrons undergo scattering, from both phonons and ions, they emit bremsstrahlung radiation. Here, we compare a theory of bremsstrahlung emission appropriate for the interaction of intense lasers with matter using soft-core potentials and Coulombic potentials. A new scaling for the radiation cross-section and the radiated power via bremsstrahlung is derived for a soft-core potential (which depends on the potential depth) and compared with the Coulomb potential. Calculations using the new scaling are performed for electrons in vacuum ultraviolet, infrared and mid-infrared laser pulses. The radiation cross-section and the radiation power via bremsstrahlung are found to increase rapidly with increases in the potential depth of up to around 200 eV and then become mostly saturated for larger depths while remaining constant for the Coulomb potential. In both cases, the radiation cross-section and the radiation power of bremsstrahlung decrease with increases in the laser wavelength. The ratio of the scattering amplitude for the soft-core potential and that for the Coulombic potential decreases exponentially with an increase in momentum transfer. The bremsstrahlung emission by electrons in plasmas may provide a broadband light source for diagnostics.

Parameterized Cross Sections for Pion Production in Proton-Proton Collisions

NASA Technical Reports Server (NTRS)

Blattnig, Steve R.; Swaminathan, Sudha R.; Kruger, Adam T.; Ngom, Moussa; Norbury, John W.; Tripathi, R. K.

2000-01-01

An accurate knowledge of cross sections for pion production in proton-proton collisions finds wide application in particle physics, astrophysics, cosmic ray physics, and space radiation problems, especially in situations where an incident proton is transported through some medium and knowledge of the output particle spectrum is required when given the input spectrum. In these cases, accurate parameterizations of the cross sections are desired. In this paper much of the experimental data are reviewed and compared with a wide variety of different cross section parameterizations. Therefore, parameterizations of neutral and charged pion cross sections are provided that give a very accurate description of the experimental data. Lorentz invariant differential cross sections, spectral distributions, and total cross section parameterizations are presented.

Nuclear Fragmentation Processes Relevant for Human Space Radiation Protection

NASA Technical Reports Server (NTRS)

Lin, Zi-Wei

2007-01-01

Space radiation from cosmic ray particles is one of the main challenges for human space explorations such-as a moon base or a trip to Mars. Models have been developed in order to predict the radiation exposure to astronauts and to evaluate the effectiveness of different shielding materials, and a key ingredient in these models is the physics of nuclear fragmentations. We have developed a semi-analytical method to determine which partial cross sections of nuclear fragmentations most affect the radiation dose behind shielding materials due to exposure to galactic cosmic rays. The cross sections thus determined will require more theoretical and/or experimental studies in order for us to better predict, reduce and mitigate the radiation exposure in human space explorations.

Determination of Spectroscopic Properties of Atmospheric Molecules from High Resolution Vacuum Ultraviolet Cross Section and Wavelength Measurements

NASA Technical Reports Server (NTRS)

Parkinson, W. H.; Yoshino, K.

1997-01-01

An account is given of progress during the period 8/l/96-7/31/97 on work on (a) cross section measurements of O2 S-R using a Fourier transform spectrometer (FTS) at the Photon Factory in Japan; (b) the determination of the predissociation linewidths of the Schumann-Runge bands (S-R) of 02; (c) cross section measurements of 02 Herzberg bands using a Fourier transform spectrometer (FTS) at Imperial College; and (d) cross section measurements of H2O in the wavelength region 120-188 nm. The experimental investigations are effected at high resolution with a 6.65 m scanning spectrometer and with the Fourier transform spectrometer. Below 175 nm, synchrotron radiation is most suitable for cross section measurements in combination with spectrometers at the Photon Factory Japan. Cross section measurements of the Doppler limited bands depend on using the very high resolution, available with the Fourier transform spectrometer, (0.025/cm resolution). All of these spectroscopic measurements are needed for accurate calculations of the production of atomic oxygen, the penetration of solar radiation into the Earth's atmosphere, and photochemistry of minor molecules.

Recent Advances in Resonance Region Nuclear Data Measurements and Analyses for Supporting Nuclear Energy Applications

NASA Astrophysics Data System (ADS)

Dunn, Michael

2008-10-01

For over 30 years, the Oak Ridge National Laboratory (ORNL) has performed research and development to provide more accurate nuclear cross-section data in the resonance region. The ORNL Nuclear Data (ND) Program consists of four complementary areas of research: (1) cross-section measurements at the Oak Ridge Electron Linear Accelerator; (2) resonance analysis methods development with the SAMMY R-matrix analysis software; (3) cross-section evaluation development; and (4) cross-section processing methods development with the AMPX software system. The ND Program is tightly coupled with nuclear fuel cycle analyses and radiation transport methods development efforts at ORNL. Thus, nuclear data work is performed in concert with nuclear science and technology needs and requirements. Recent advances in each component of the ORNL ND Program have led to improvements in resonance region measurements, R-matrix analyses, cross-section evaluations, and processing capabilities that directly support radiation transport research and development. Of particular importance are the improvements in cross-section covariance data evaluation and processing capabilities. The benefit of these advances to nuclear science and technology research and development will be discussed during the symposium on Nuclear Physics Research Connections to Nuclear Energy.

Nucleon-Nucleon Total Cross Section

NASA Technical Reports Server (NTRS)

Norbury, John W.

2008-01-01

The total proton-proton and neutron-proton cross sections currently used in the transport code HZETRN show significant disagreement with experiment in the GeV and EeV energy ranges. The GeV range is near the region of maximum cosmic ray intensity. It is therefore important to correct these cross sections, so that predictions of space radiation environments will be accurate. Parameterizations of nucleon-nucleon total cross sections are developed which are accurate over the entire energy range of the cosmic ray spectrum.

Total photoionization cross sections of atomic oxygen from threshold to 44.3 A

NASA Technical Reports Server (NTRS)

Angel, G. C.; Samson, James A. R.

1988-01-01

Synchrotron radiation was used to obtain the relative photoionization cross section of atomic oxygen for the production of singly charged ions over the 44.3-910.5-A wavelength range. Measurement of the contribution of multiple ionization to the cross sections has made possible the determination of total photoionization cross sections below 250 A. The series of autoionizing resonances leading to the 4P state of the oxygen ion has been observed using an ionization-type experimental procedure for the first time.

The Photodissociation of HCN and HNC: Effects on the HNC/HCN Abundance Ratio in the Interstellar Medium

NASA Astrophysics Data System (ADS)

Aguado, Alfredo; Roncero, Octavio; Zanchet, Alexandre; Agúndez, Marcelino; Cernicharo, José

2017-03-01

The impact of the photodissociation of HCN and HNC isomers is analyzed in different astrophysical environments. For this purpose, the individual photodissociation cross sections of HCN and HNC isomers have been calculated in the 7-13.6 eV photon energy range for a temperature of 10 K. These calculations are based on the ab initio calculation of three-dimensional adiabatic potential energy surfaces of the 21 lower electronic states. The cross sections are then obtained using a quantum wave packet calculation of the rotational transitions needed to simulate a rotational temperature of 10 K. The cross section calculated for HCN shows significant differences with respect to the experimental one, and this is attributed to the need to consider non-adiabatic transitions. Ratios between the photodissociation rates of HCN and HNC under different ultraviolet radiation fields have been computed by renormalizing the rates to the experimental value. It is found that HNC is photodissociated faster than HCN by a factor of 2.2 for the local interstellar radiation field and 9.2 for the solar radiation field, at 1 au. We conclude that to properly describe the HNC/HCN abundance ratio in astronomical environments illuminated by an intense ultraviolet radiation field, it is necessary to use different photodissociation rates for each of the two isomers, which are obtained by integrating the product of the photodissociation cross sections and ultraviolet radiation field over the relevant wavelength range.

String Fragmentation Model in Space Radiation Problems

NASA Technical Reports Server (NTRS)

Tang, Alfred; Johnson, Eloise (Editor); Norbury, John W.; Tripathi, R. K.

2002-01-01

String fragmentation models such as the Lund Model fit experimental particle production cross sections very well in the high-energy limit. This paper gives an introduction of the massless relativistic string in the Lund Model and shows how it can be modified with a simple assumption to produce formulas for meson production cross sections for space radiation research. The results of the string model are compared with inclusive pion production data from proton-proton collision experiments.

The Iron Project & Opacity Project: Photoionization, radiative transitions of iron ions for Opacities and Astrophysical Applications

NASA Astrophysics Data System (ADS)

Zhao, Lianshui; Nahar, Sultana; Pradhan, Anil; Eissner, Werner

2017-04-01

We have carried out converged close coupling R-Matrix (CCC-RM) calculations for photoionization of Ne-like Fe XVII and demonstrate orders-of-magnitude enhancements in cross section due to successive core excitations. Convergence criteria are: (i) inclusion of sufficient number of residual ion Fe XVIII core states, (ii) high-resolution of myriad autoionizing resonances, and (iii) high-energy cross sections. We discuss verification of the conventional oscillator strength sum-rule in limited energy regions for bound-free plasma opacity. High energy cross sections are also under investigation. In order to obtain solar iron opacity at the boundary of the radiative and convection zones, we have studied the residual ion states that should provide convergence of resonances of other L-shell iron ions, Fe XIV - Fe XX, in the plasma region. Preliminary results from R-matrix calculations of photoionization cross sections will be reported. NSF, DOE, OSC.

Absolute Photoionization Cross Section for Fe6+ to Fe10+ Ions in the Photon Energy Region of the 2p–3d Resonance Lines

NASA Astrophysics Data System (ADS)

Blancard, C.; Cubaynes, D.; Guilbaud, S.; Bizau, J.-M.

2018-01-01

Resonant single photoionization cross sections of Fen+ (n = 6 to 10) ions have been measured in absolute values using a merged-beams setup at the SOLEIL synchrotron radiation facility. Photon energies were between about 710 and 780 eV, covering the range of the 2p–3d transitions. The experimental cross sections are compared to calculations we performed using a multi-configuration Dirac–Fock code and the OPAS code dedicated to radiative opacity calculations. Comparisons are also done with the Chandra X-ray observatory NGC 3783 spectra and with the results of previously published calculations.

Proton-Nucleus Total Cross Sections in Coupled-Channel Approach

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, John W.; Cucinotta, Francis A.

2000-01-01

Recently, nucleon-nucleon (N-N) cross sections in the medium have been extracted directly from experiment. The in-medium N-N cross sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the Langley Research Center. In the present study the ratio of the real to the imaginary part of the two-body scattering amplitude in the medium was investigated. These ratios are used in combination with the in-medium N-N cross sections to calculate total proton-nucleus cross sections. The agreement is excellent with the available experimental data. These cross sections are needed for the radiation risk assessment of space missions.

Scattering of Non-Relativistic Charged Particles by Electromagnetic Radiation

NASA Astrophysics Data System (ADS)

Apostol, M.

2017-11-01

The cross-section is computed for non-relativistic charged particles (like electrons and ions) scattered by electromagnetic radiation confined to a finite region (like the focal region of optical laser beams). The cross-section exhibits maxima at scattering angles given by the energy and momentum conservation in multi-photon absorption or emission processes. For convenience, a potential scattering is included and a comparison is made with the well-known Kroll-Watson scattering formula. The scattering process addressed in this paper is distinct from the process dealt with in previous studies, where the scattering is immersed in the radiation field.

Determination of spectroscopic properties of atmospheric molecules from high resolution vacuum ultraviolet cross section and wavelength measurements

NASA Technical Reports Server (NTRS)

Parkinson, W. H.; Yoshino, K.; Freeman, D. E.

1993-01-01

An account is given of progress during the six-month period 1 Nov. 1992 to 30 Apr. 1993 on work on (1) cross section measurements of the Schumann-Runge continuum; (2) the determination of the predissociation linewidths of the Schumann-Runge bands of O2; (3) the determination of the molecular constants of the ground state of O2; (4) cross section measurements of CO2 in wavelength region 120-170 nm; and (4) determination of dissociation energy of O2. The experimental investigations are effected at high resolution with a 6.65 m scanning spectrometer which is, by virtue of its small instrumental width (FWHM = 0.0013 nm), uniquely suitable for cross section measurements of molecular bands with discrete rotational structure. Below 175 nm and in the region of the S-R continuum, synchrotron radiation is suitable for cross section measurements. All of these spectroscopic measurements are needed for accurate calculations of the production of atomic oxygen and penetration of solar radiation into the Earth's atmosphere.

State-resolved Photodissociation and Radiative Association Data for the Molecular Hydrogen Ion

NASA Astrophysics Data System (ADS)

Zammit, Mark C.; Savage, Jeremy S.; Colgan, James; Fursa, Dmitry V.; Kilcrease, David P.; Bray, Igor; Fontes, Christopher J.; Hakel, Peter; Timmermans, Eddy

2017-12-01

We present state-resolved (electronic, vibrational, and rotational) cross sections and rate coefficients for the photodissociation (PD) of {{{H}}}2+ and radiative association (RA) of H–H+. We developed a fully quantum mechanical approach within the nonrelativistic Born–Oppenheimer approximation to describe {{{H}}}2+ and calculate the data for transitions between the ground electronic state 1s{σ }g and the 2p{σ }u, 2p{π }u, 3p{σ }u, 3p{π }u, 4p{σ }u, 4f{σ }u, 4f{π }u, and 4p{π }u electronic states (i.e., up to {{{H}}}2+ n = 4). Tables of the dipole-matrix elements and energies needed to calculate state-resolved cross sections and rate coefficients will be made publicly available. These data could be important in astrophysical models when dealing with photon wavelengths (or radiation temperature distributions that are weighted toward such wavelengths) around 100 nm. For example, at these wavelengths and a material temperature of 8400 K, the LTE-averaged PD cross section via the (second electronically excited) 2p{π }u state is over three times larger than the PD cross section via the (first electronically excited) 2p{σ }u state.

Rayleigh, Compton and K-shell radiative resonant Raman scattering in 83Bi for 88.034 keV γ-rays

NASA Astrophysics Data System (ADS)

Kumar, Sanjeev; Sharma, Veena; Mehta, D.; Singh, Nirmal

2007-11-01

The Rayleigh, Compton and K-shell radiative resonant Raman scattering cross-sections for the 88.034 keV γ-rays have been measured in the 83Bi (K-shell binding energy = 90.526 keV) element. The measurements have been performed at 130° scattering angle using reflection-mode geometrical arrangement involving the 109Cd radioisotope as photon source and an LEGe detector. Computer simulations were exercised to determine distributions of the incident and emission angles, which were further used in evaluation of the absorption corrections for the incident and emitted photons in the target. The measured cross-sections for the Rayleigh scattering are compared with the modified form-factors (MFs) corrected for the anomalous-scattering factors (ASFs) and the S-matrix calculations; and those for the Compton scattering are compared with the Klein-Nishina cross-sections corrected for the non-relativistic Hartree-Fock incoherent scattering function S(x, Z). The ratios of the measured KL2, KL3, KM and KN2,3 radiative resonant Raman scattering cross-sections are found to be in general agreement with those of the corresponding measured fluorescence transition probabilities.

Nonrelativistic grey S n -transport radiative-shock solutions

DOE PAGES

Ferguson, J. M.; Morel, J. E.; Lowrie, R. B.

2017-06-01

We present semi-analytic radiative-shock solutions in which grey Sn-transport is used to model the radiation, and we include both constant cross sections and cross sections that depend on temperature and density. These new solutions solve for a variable Eddington factor (VEF) across the shock domain, which allows for interesting physics not seen before in radiative-shock solutions. Comparisons are made with the grey nonequilibrium-diffusion radiative-shock solutions of Lowrie and Edwards [1], which assumed that the Eddington factor is constant across the shock domain. It is our experience that the local Mach number is monotonic when producing nonequilibrium-diffusion solutions, but that thismore » monotonicity may disappear while integrating the precursor region to produce Sn-transport solutions. For temperature- and density-dependent cross sections we show evidence of a spike in the VEF in the far upstream portion of the radiative-shock precursor. We show evidence of an adaptation zone in the precursor region, adjacent to the embedded hydrodynamic shock, as conjectured by Drake [2, 3], and also confirm his expectation that the precursor temperatures adjacent to the Zel’dovich spike take values that are greater than the downstream post-shock equilibrium temperature. We also show evidence that the radiation energy density can be nonmonotonic under the Zel’dovich spike, which is indicative of anti-diffusive radiation flow as predicted by McClarren and Drake [4]. We compare the angle dependence of the radiation flow for the Sn-transport and nonequilibriumdiffusion radiation solutions, and show that there are considerable differences in the radiation flow between these models across the shock structure. Lastly, we analyze the radiation flow to understand the cause of the adaptation zone, as well as the structure of the Sn-transport radiation-intensity solutions across the shock structure.« less

Nonrelativistic grey S n -transport radiative-shock solutions

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

Ferguson, J. M.; Morel, J. E.; Lowrie, R. B.

We present semi-analytic radiative-shock solutions in which grey Sn-transport is used to model the radiation, and we include both constant cross sections and cross sections that depend on temperature and density. These new solutions solve for a variable Eddington factor (VEF) across the shock domain, which allows for interesting physics not seen before in radiative-shock solutions. Comparisons are made with the grey nonequilibrium-diffusion radiative-shock solutions of Lowrie and Edwards [1], which assumed that the Eddington factor is constant across the shock domain. It is our experience that the local Mach number is monotonic when producing nonequilibrium-diffusion solutions, but that thismore » monotonicity may disappear while integrating the precursor region to produce Sn-transport solutions. For temperature- and density-dependent cross sections we show evidence of a spike in the VEF in the far upstream portion of the radiative-shock precursor. We show evidence of an adaptation zone in the precursor region, adjacent to the embedded hydrodynamic shock, as conjectured by Drake [2, 3], and also confirm his expectation that the precursor temperatures adjacent to the Zel’dovich spike take values that are greater than the downstream post-shock equilibrium temperature. We also show evidence that the radiation energy density can be nonmonotonic under the Zel’dovich spike, which is indicative of anti-diffusive radiation flow as predicted by McClarren and Drake [4]. We compare the angle dependence of the radiation flow for the Sn-transport and nonequilibriumdiffusion radiation solutions, and show that there are considerable differences in the radiation flow between these models across the shock structure. Lastly, we analyze the radiation flow to understand the cause of the adaptation zone, as well as the structure of the Sn-transport radiation-intensity solutions across the shock structure.« less

Cross-Section Parameterizations for Pion and Nucleon Production From Negative Pion-Proton Collisions

NASA Technical Reports Server (NTRS)

Norbury, John W.; Blattnig, Steve R.; Norman, Ryan; Tripathi, R. K.

2002-01-01

Ranft has provided parameterizations of Lorentz invariant differential cross sections for pion and nucleon production in pion-proton collisions that are compared to some recent data. The Ranft parameterizations are then numerically integrated to form spectral and total cross sections. These numerical integrations are further parameterized to provide formula for spectral and total cross sections suitable for use in radiation transport codes. The reactions analyzed are for charged pions in the initial state and both charged and neutral pions in the final state.

General upper bound on single-event upset rate. [due to ionizing radiation in orbiting vehicle avionics

NASA Technical Reports Server (NTRS)

Chlouber, Dean; O'Neill, Pat; Pollock, Jim

1990-01-01

A technique of predicting an upper bound on the rate at which single-event upsets due to ionizing radiation occur in semiconducting memory cells is described. The upper bound on the upset rate, which depends on the high-energy particle environment in earth orbit and accelerator cross-section data, is given by the product of an upper-bound linear energy-transfer spectrum and the mean cross section of the memory cell. Plots of the spectrum are given for low-inclination and polar orbits. An alternative expression for the exact upset rate is also presented. Both methods rely only on experimentally obtained cross-section data and are valid for sensitive bit regions having arbitrary shape.

Lithography Radiation Effects Study.

DTIC Science & Technology

1984-11-01

Electronic Industries, 7317 South Washinqton Avenue, Edina, Minnesota 5;435, 1972) A- 2-8 15. J. H. Scofield , Theoretical Photoionization Cross Sections...exci- tation of a qiven shell is proportional to the photoionization cross-section * of the shell. Theoretical photoionization cross-sections as a...Ti (Ka = 4.51 keV), 500 A and for Cr (K. = 5.41 keV), 580 A. Comparison of these data with existing theoretical models were not carried out. The

Absorption of infrared radiation by electrons in the field of a neutral hydrogen atom

NASA Technical Reports Server (NTRS)

Stallcop, J. R.

1974-01-01

An analytical expression for the absorption coefficient is developed from a relationship between the cross-section for inverse bremsstrahlung absorption and the cross-section for electron-atom momentum transfer; it is accurate for those photon frequencies v and temperatures such that hv/kT is small. The determination of the absorption of infrared radiation by free-free transitions of the negative hydrogen ion has been extended to higher temperatures. A simple analytical expression for the absorption coefficient has been derived.

CEPXS

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

2015-10-19

CEPXS is a multigroup-Legendre cross-section generating code. The cross sections produced by CEPXS enable coupled electron-photon transport calculations to be performed with multigroup radiation transport codes, e.g. MITS and SCEPTRE. CEPXS generates multigroup-Legendre cross sections for photons, electrons and positrons over the energy range from 100 MeV to 1.0 keV. The continuous slowing-down approximation is used for those electron interactions that result in small-energy losses. The extended transport correction is applied to the forward-peaked elastic scattering cross section for electrons. A standard multigroup-Legendre treatment is used for the other coupled electron-photon cross sections. CEPXS extracts electron cross-section information from themore » DATAPAC data set and photon cross-section information from Biggs-Lighthill data. The model that is used for ionization/relaxation in CEPXS is essentially the same as that employed in ITS.« less

Corrections to the Thomson cross section caused by relativistic effects and by the presence of the drift velocity of a classical charged particle in the field of a monochromatic plane wave

NASA Astrophysics Data System (ADS)

Perestoronin, A. V.

2017-03-01

An approach to the solution of the relativistic problem of the motion of a classical charged particle in the field of a monochromatic plane wave with an arbitrary polarization (linear, circular, or elliptic) is proposed. It is based on the analysis of the 4-vector equation of motion of the charged particle together with the 4-vector and tensor equations for the components of the electromagnetic field tensor of a monochromatic plane wave. This approach provides analytical expressions for the time-averaged square of the 4-acceleration of the charge, as well as for the averaged values of any quantities periodic in the time of the reference frame. Expressions for the integral power of scattered radiation, which is proportional to the time-averaged square of the 4-acceleration of the charge, and for the integral scattering cross section, which is the ratio of the power of scattered radiation to the intensity of incident radiation, are obtained for an arbitrary inertial reference frame. An expression for the scattering cross section, which coincides with the known results at the circular and linear polarizations of the incident waves and describes the case of elliptic polarization of the incident wave, is obtained for the reference frame where the charged particle is on average at rest. An expression for the scattering cross section including relativistic effects and the nonzero drift velocity of a particle in this system is obtained for the laboratory reference frame, where the initial velocity of the charged particle is zero. In the case of the circular polarization of the incident wave, the scattering cross section in the laboratory frame is equal to the Thompson cross section.

Py4CAtS - Python tools for line-by-line modelling of infrared atmospheric radiative transfer

NASA Astrophysics Data System (ADS)

Schreier, Franz; García, Sebastián Gimeno

2013-05-01

Py4CAtS — Python scripts for Computational ATmospheric Spectroscopy is a Python re-implementation of the Fortran infrared radiative transfer code GARLIC, where compute-intensive code sections utilize the Numeric/Scientific Python modules for highly optimized array-processing. The individual steps of an infrared or microwave radiative transfer computation are implemented in separate scripts to extract lines of relevant molecules in the spectral range of interest, to compute line-by-line cross sections for given pressure(s) and temperature(s), to combine cross sections to absorption coefficients and optical depths, and to integrate along the line-of-sight to transmission and radiance/intensity. The basic design of the package, numerical and computational aspects relevant for optimization, and a sketch of the typical workflow are presented.

Measurement of the e +e -→π +π - cross section between 600 and 900 MeV using initial state radiation

DOE PAGES

Ablikim, M.

2015-11-28

We extract the e +e -→π +π - cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. A data set with an integrated luminosity of 2.93 fb -1 taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor |F π| 2 as well as the contribution of the measured cross section to the leading-order hadronic vacuum polarization contribution to (g-2) μ. In conclusion, we find thismore » value to be a π μ π,LO (600–900 MeV) = (368.2 ±2.5 stat±3.3 sys) ·10 -10, which is between the corresponding values using the BaBar or KLOE data.« less

Measurement of charge- and mass-changing cross sections for 4He+12C collisions in the energy range 80-220 MeV/u for applications in ion beam therapy

NASA Astrophysics Data System (ADS)

Horst, Felix; Schuy, Christoph; Weber, Uli; Brinkmann, Kai-Thomas; Zink, Klemens

2017-08-01

4He ions are considered to be used for hadron radiotherapy due to their favorable physical and radiobiological properties. For an accurate dose calculation the fragmentation of the primary 4He ions occurring as a result of nuclear collisions must be taken into account. Therefore precise nuclear reaction models need to be implemented in the radiation transport codes used for dose calculation. A fragmentation experiment using thin graphite targets was conducted at the Heidelberg Ion Beam Therapy Center (HIT) to obtain new and precise 4He-nucleus cross section data in the clinically relevant energy range. Measured values for the charge-changing cross section, mass-changing cross section, as well as the inclusive 3He production cross section for 4He+12C collisions at energies between 80 and 220 MeV /u are presented. These data are compared to the 4He-nucleus reaction model by DeVries and Peng as well as to the parametrizations by Tripathi et al. and by Cucinotta et al., which are implemented in the treatment planning code trip98 and several other radiation transport codes.

Closing Report for NASA Cooperative Agreement NASA-1-242

NASA Technical Reports Server (NTRS)

Maung, Khin Maung

1999-01-01

Reliable estimates of exposures due to ionizing radiations are of paramount importance in achieving human exploration and development of space, and in several technologically important and scientifically significant areas impacting on industrial and public health. For proper assessment of radiation exposures reliable transport codes are needed. An essential input to the transport codes is the information about the interaction of ions and neutrons with the matter. Most of the information about this interaction is put in by nuclear cross section data. In order to obtain an accurate parameterization of cross sections data, theoretical input is indispensable especially for the processes where there is little or no experimental data available. In the grant period reliable data base was developed and a phenomenological model was developed for the total absorption cross sections valid for any charged/uncharged light, medium and heavy collision pairs valid for the entire energy range. It is gratifying to note the success of the model. The cross sections model has been adopted and is in use in NASA cosmic ray detector development projects, the radiation protection and shielding programs and several DoE laboratories and institutions. A list of the publications based on the work done during the grant period is given below and a sample copy of one of the papers is enclosed with this report.

Analytic forms for cross sections of di-lepton production from e+e- collisions around the J/Ψ resonance

NASA Astrophysics Data System (ADS)

Zhou, Xing-Yu; Wang, Ya-Di; Xia, Li-Gang

2017-08-01

A detailed theoretical derivation of the cross sections of e+e- → e+e- and e+e- → μ + μ - around the J/ψ resonance is reported. The resonance and interference parts of the cross sections, related to J/ψ resonance parameters, are calculated. Higher-order corrections for vacuum polarization and initial-state radiation are considered. An arbitrary upper limit of radiative correction integration is involved. Full and simplified versions of analytic formulae are given with precision at the level of 0.1% and 0.2%, respectively. Moreover, the results obtained in the paper can be applied to the case of the ψ(3686) resonance. Supported by National Natural Science Foundation of China (11275211) and Istituto Nazionale di Fisica Nucleare, Italy

Extinction cross-section cancellation of a cylindrical radiating active source near a rigid corner and acoustic invisibility

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2017-11-01

Active cloaking in its basic form requires that the extinction cross-section (or energy efficiency) from a radiating body vanishes. In this analysis, this physical effect is demonstrated for an active cylindrically radiating acoustic source in a non-viscous fluid, undergoing periodic axisymmetric harmonic vibrations near a rigid corner (i.e., quarter-space). The rigorous multipole expansion method in cylindrical coordinates, the method of images, and the addition theorem of cylindrical wave functions are used to derive closed-form mathematical expressions for the radiating, amplification, and extinction cross-sections of the active source. Numerical computations are performed assuming monopole and dipole modal oscillations of the circular source. The results reveal some of the situations where the extinction energy efficiency factor of the active source vanishes depending on its size and location with respect to the rigid corner, thus, achieving total invisibility. Moreover, the extinction energy efficiency factor varies between positive or negative values. These effects also occur for higher-order modal oscillations of the active source. The results find potential applications in the development of acoustic cloaking devices and invisibility in underwater acoustics or other areas.

Investigations of electromagnetic scattering by columnar ice crystals

NASA Technical Reports Server (NTRS)

Weil, H.; Senior, T. B. A.

1976-01-01

An integral equation approach was developed to determine the scattering and absorption of electromagnetic radiation by thin walled cylinders of arbitrary cross-section and refractive index. Based on this method, extensive numerical data was presented at infrared wavelengths for hollow hexagonal cross section cylinders which simulate columnar sheath ice crystals.

Physical parameters for proton induced K-, L-, and M-shell ionization processes

NASA Astrophysics Data System (ADS)

Shehla; Puri, Sanjiv

2016-10-01

The proton induced atomic inner-shell ionization processes comprising radiative and non-radiative transitions are characterized by physical parameters, namely, the proton ionization cross sections, X-ray emission rates, fluorescence yields and Coster-Kronig (CK) transition probabilities. These parameters are required to calculate the K/L/M shell X-ray production (XRP) cross sections and relative X-ray intensity ratios, which in turn are required for different analytical applications. The current status of different physical parameters is presented in this report for use in various applications.

Communication: Electron ionization of DNA bases.

PubMed

Rahman, M A; Krishnakumar, E

2016-04-28

No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve the existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.

Photon scattering cross sections of H2 and He measured with synchrotron radiation

NASA Technical Reports Server (NTRS)

Ice, G. E.

1977-01-01

Total (elastic + inelastic) differential photon scattering cross sections have been measured for H2 gas and He, using an X-ray beam. Absolute measured cross sections agree with theory within the probable errors. Relative cross sections (normalized to theory at large S) agree to better than one percent with theoretical values calculated from wave functions that include the effect of electron-electron Coulomb correlation, but the data deviate significantly from theoretical independent-particle (e.g., Hartree-Fock) results. The ratios of measured absolute He cross sections to those of H2, at any given S, also agree to better than one percent with theoretical He-to-H2 cross-section ratios computed from correlated wave functions. It appears that photon scattering constitutes a very promising tool for probing electron correlation in light atoms and molecules.

Radiative neutron capture cross sections on 176Lu at DANCE

NASA Astrophysics Data System (ADS)

Roig, O.; Jandel, M.; Méot, V.; Bond, E. M.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Keksis, A. L.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.

2016-03-01

The cross section of the neutron capture reaction 176Lu(n ,γ ) has been measured for a wide incident neutron energy range with the Detector for Advanced Neutron Capture Experiments at the Los Alamos Neutron Science Center. The thermal neutron capture cross section was determined to be (1912 ±132 ) b for one of the Lu natural isotopes, 176Lu. The resonance part was measured and compared to the Mughabghab's atlas using the R -matrix code, sammy. At higher neutron energies the measured cross sections are compared to ENDF/B-VII.1, JEFF-3.2, and BRC evaluated nuclear data. The Maxwellian averaged cross sections in a stellar plasma for thermal energies between 5 keV and 100 keV were extracted using these data.

Effects of quantum interference between radiative and dielectronic recombination on photorecombination cross-section profiles for the He-like ions Ar{sup 16+} and Fe{sup 24+}

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

Behar, Ehud; Jacobs, Verne L.; Oreg, Joseph

Total cross sections for electron-ion photorecombination (PR) processes are calculated using a projection-operator and resolvent-operator approach. This approach provides a unified quantum-mechanical description of the combined electron-ion PR process, including radiative and dielectronic recombination as coherent, interfering components. An especially adapted version of the Hebrew-University Lawrence-Livermore Atomic Code HULLAC is developed and employed for the calculations. In particular, PR cross sections for He-like argon and iron ions are calculated for incident-electron energies in the vicinity of the 1s2l2l{sup '} and 1s2l3l{sup '} doubly-excited, autoionizing levels of the Li-like ions. Significant effects of quantum interference between radiative and dielectronic recombination, inmore » the form of asymmetric PR cross-section profiles, are predicted, especially for weak transitions. The general behavior of the interference effect, as a function of the ion charge q and as a function of the principal quantum number n{sup '} of the outer electron in the autoionizing state, is investigated using a hydrogenic-scaling analysis. It is found that the degree of asymmetry in the PR cross-section profile can be substantial for close-to-neutral ions and also for very highly-charged ions. In the intermediate-charge regime, on the other hand, the asymmetry is anticipated to be less prominent. The dependence of the quantum-interference effect on n{sup '} is predicted to be much weaker.« less

Angular analysis of the e + e - → D ( * ) ± D * ∓ process near the open charm threshold using initial-state radiation

DOE PAGES

Zhukova, V.

2018-01-10

Here, we repormore » t a new measurement of the exclusive e + e - → D ( * ) ± D * ∓ cross sections as a function of the center-of-mass energy from the D ( * ) ± D * ∓ threshold through $$ \\sqrt{s}=6.0 $$ GeV, using the initial-state radiation technique. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 951 fb -1. The accuracy of the cross section measurement is increased by a factor of 2 over the first Belle study. We perform the first angular analysis of the e + e - → D ( * ) ± D * ∓ process and decompose this exclusive cross section into three components corresponding to the D * helicities.« less

Angular analysis of the e + e - → D ( * ) ± D * ∓ process near the open charm threshold using initial-state radiation

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

Zhukova, V.

Here, we repormore » t a new measurement of the exclusive e + e - → D ( * ) ± D * ∓ cross sections as a function of the center-of-mass energy from the D ( * ) ± D * ∓ threshold through $$ \\sqrt{s}=6.0 $$ GeV, using the initial-state radiation technique. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 951 fb -1. The accuracy of the cross section measurement is increased by a factor of 2 over the first Belle study. We perform the first angular analysis of the e + e - → D ( * ) ± D * ∓ process and decompose this exclusive cross section into three components corresponding to the D * helicities.« less

Universal Parameterization of Absorption Cross Sections

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Cucinotta, Francis A.; Wilson, John W.

1999-01-01

Our prior nuclear absorption cross sections model is extended for light systems (A less than or equal to 4) where either both projectile and target are light particles or one is a light particle and the other is a medium or heavy nucleus. The agreement with experiment is excellent for these cases as well. Present work in combination with our original model provides a comprehensive picture of absorption cross sections for light, medium, and heavy systems, a very valuable input for radiation protection studies.

Synchronized vortex shedding and sound radiation from two side-by-side rectangular cylinders of different cross-sectional aspect ratios

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

Octavianty, Ressa, E-mail: ressa-octavianty@ed.tmu.ac.jp; Asai, Masahito, E-mail: masai@tmu.ac.jp

Synchronized vortex shedding from two side-by-side cylinders and the associated sound radiation were examined experimentally at Reynolds numbers of the order of 10{sup 4} in low-Mach-number flows. In addition to a pair of square cylinders, a pair of rectangular cylinders, one with a square cross section (d × d) and the other with a rectangular cross section (d × c) having a cross-sectional aspect ratio (c/d) of 1.2–1.5, was considered. The center-to-center distance between the two cylinders L/d was 3.6, 4.5, and 6.0; these settings were within the non-biased flow regime for side-by-side square cylinders. In case of a squaremore » cylinder pair, anti-phase synchronized vortex shedding occurring for L/d = 3.6 and 4.5 generated a quadrupole-like sound source which radiated in-phase, planar-symmetric sound in the far field. Synchronized vortex shedding from the two rectangular cylinders with different c/d also occurred with almost the same frequency as the characteristic frequency of the square-cylinder wake in the case of the small center-to-center distance, L/d = 3.6, for all the cylinder pairs examined. The synchronized sound field was anti-phase and asymmetric in amplitude, unlike the case of a square cylinder pair. For larger spacing L/d = 4.5, synchronized vortex shedding and anti-phase sound still occurred, but only for close cross-sectional aspect ratios (c/d = 1.0 and 1.2), and highly modulated sound was radiated with two different frequencies due to non-synchronized vortex shedding from the two cylinders for larger differences in c/d. It was also found that when synchronized vortex shedding occurred, near-wake velocity fluctuations exhibited high spanwise-coherency, with a very sharp spectral peak compared with the single-cylinder case.« less

Efficient and Accurate Computation of Non-Negative Anisotropic Group Scattering Cross Sections for Discrete Ordinates and Monte Carlo Radiation Transport

DTIC Science & Technology

2002-07-01

Date Kirk A. Mathews (Advisor) James T. Moore (Dean’s Representative) Charles J. Bridgman (Member...Adler-Adler, and Kalbach -Mann representations of the scatter cross sections that are used for some isotopes in ENDF/B-VI are not included. They are not

Gas mixtures for gas-filled radiation detectors

DOEpatents

Christophorou, Loucas G.; McCorkle, Dennis L.; Maxey, David V.; Carter, James G.

1982-01-05

Improved binary and ternary gas mixtures for gas-filled radiation detectors are provided. The components are chosen on the basis of the principle that the first component is one molecular gas or mixture of two molecular gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a noble gas having a very small cross section at and below about 1.0 eV, whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electric field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Improved gas mixtures for gas-filled radiation detectors

DOEpatents

Christophorou, L.G.; McCorkle, D.L.; Maxey, D.V.; Carter, J.G.

1980-03-28

Improved binary and ternary gas mixtures for gas-filled radiation detectors are provided. The components are chosen on the basis of the principle that the first component is one molecular gas or mixture of two molecular gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a noble gas having a very small cross section at and below about 1.0 eV, whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electric field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Determination of the effective sample thickness via radiative capture

DOE PAGES

Hurst, A. M.; Summers, N. C.; Szentmiklosi, L.; ...

2015-09-14

Our procedure for determining the effective thickness of non-uniform irregular-shaped samples via radiative capture is described. In this technique, partial γ-ray production cross sections of a compound nucleus produced in a neutron-capture reaction are measured using Prompt Gamma Activation Analysis and compared to their corresponding standardized absolute values. For the low-energy transitions, the measured cross sections are lower than their standard values due to significant photoelectric absorption of the γ rays within the bulk-sample volume itself. Using standard theoretical techniques, the amount of γ-ray self absorption and neutron self shielding can then be calculated by iteratively varying the sample thicknessmore » until the observed cross sections converge with the known standards. The overall attenuation provides a measure of the effective sample thickness illuminated by the neutron beam. This procedure is illustrated through radiative neutron capture using powdered oxide samples comprising enriched 186W and 182W from which their tungsten-equivalent effective thicknesses are deduced to be 0.077(3) mm and 0.042(8) mm, respectively.« less

Prediction of error rates in dose-imprinted memories on board CRRES by two different methods. [Combined Release and Radiation Effects Satellite

NASA Technical Reports Server (NTRS)

Brucker, G. J.; Stassinopoulos, E. G.

1991-01-01

An analysis of the expected space radiation effects on the single event upset (SEU) properties of CMOS/bulk memories onboard the Combined Release and Radiation Effects Satellite (CRRES) is presented. Dose-imprint data from ground test irradiations of identical devices are applied to the predictions of cosmic-ray-induced space upset rates in the memories onboard the spacecraft. The calculations take into account the effect of total dose on the SEU sensitivity of the devices as the dose accumulates in orbit. Estimates of error rates, which involved an arbitrary selection of a single pair of threshold linear energy transfer (LET) and asymptotic cross-section values, were compared to the results of an integration over the cross-section curves versus LET. The integration gave lower upset rates than the use of the selected values of the SEU parameters. Since the integration approach is more accurate and eliminates the need for an arbitrary definition of threshold LET and asymptotic cross section, it is recommended for all error rate predictions where experimental sigma-versus-LET curves are available.

Fe L-shell Excitation Cross Section Measurements on EBIT-I

NASA Astrophysics Data System (ADS)

Chen, Hui; Beiersdorfer, P.; Brown, G.; Boyce, K.; Kelley, R.; Kilbourne, C.; Porter, F.; Gu, M. F.; Kahn, S.

2006-09-01

We report the measurement of electron impact excitation cross sections for the strong iron L-shell 3-2 lines of Fe XVII to Fe XXIV at the LLNL EBIT-I electron beam ion trap using a crystal spectrometer and NASA-Goddard Space Flight Center's 6x6 pixel array microcalorimeter. The cross sections were determined by direct normalization to the well-established cross sections for radiative electron capture. Our results include the excitation cross section for over 50 lines at multiple electron energies. Although we have found that for 3C line in Fe XVII the measured cross sections differ significantly from theory, in most cases the measurements and theory agree within 20%. This work was performed under the auspices of the U.S. DOE by LLNL under contract No. W-7405-Eng-48 and supported by NASA APRA grants to LLNL, GSFC, and Stanford University.

Heavy fragment production cross sections from 1.05 GeV/nucleon 56Fe in C, Al, Cu, Pb, and CH2 targets

NASA Technical Reports Server (NTRS)

Zeitlin, C.; Heilbronn, L.; Miller, J.; Rademacher, S. E.; Borak, T.; Carter, T. R.; Frankel, K. A.; Schimmerling, W.; Stronach, C. E.; Chatterjee, A. (Principal Investigator)

1997-01-01

We have obtained charge-changing cross sections and partial cross sections for fragmentation of 1.05 GeV/nucleon Fe projectiles incident on H, C, Al, Cu, and Pb nuclei. The energy region covered by this experiment is critical for an understanding of galactic cosmic ray propagation and space radiation biophysics. Surviving primary beam particles and fragments with charges from 12 to 25 produced within a forward cone of half-angle 61 mrad were detected using a silicon detector telescope to identify their charge and the cross sections were calculated after correction of the measured yields for finite target thickness effects. The cross sections are compared to model calculations and to previous measurements. Cross sections for the production of fragments with even-numbered nuclear charges are seen to be enhanced in almost all cases.

Medium modified two-body scattering amplitude from proton-nucleus total cross-sections

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.

2001-01-01

Recently (R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 145 (1998) 277; R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, NASA-TP-1998-208438), we have extracted nucleon-nucleon (N-N) cross-sections in the medium directly from experiment. The in-medium N-N cross-sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the NASA Langley Research Center. Here, we investigate the ratio of real to imaginary part of the two-body scattering amplitude in the medium. These ratios are used in combination with the in-medium N-N cross-sections to calculate total proton-nucleus cross-sections. The agreement is excellent with the available experimental data. These cross-sections are needed for the radiation risk assessment of space missions. c2001 Elsevier Science B.V. All rights reserved.

Communication: Electron ionization of DNA bases

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

Rahman, M. A.; Krishnakumar, E., E-mail: ekkumar@tifr.res.in

2016-04-28

No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve themore » existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.« less

A method for calculating proton-nucleus elastic cross-sections

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.

2002-01-01

Recently [Nucl. Instr. and Meth. B 145 (1998) 277; Extraction of in-medium nucleon-nucleon amplitude from experiment, NASA-TP, 1998], we developed a method of extracting nucleon-nucleon (N-N) cross-sections in the medium directly from experiment. The in-medium N-N cross-sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the NASA Langley Research Center. We investigated [Proton-nucleus total cross-sections in coupled-channel approach, NASA/TP, 2000; Nucl. Instr. and Meth. B 173-174 (2001) 391] the ratio of real to imaginary part of the two body scattering amplitude in the medium. These ratios are used in combination with the in-medium N-N cross-sections to calculate proton-nucleus elastic cross-sections. The agreement is excellent with the available experimental data. These cross-sections are needed for the radiation risk assessment of space missions. c2002 Elsevier Science B.V. All rights reserved.

Electron Bremsstrahlung Cross Sections at 25 and 50 keV from Xe and Kr

NASA Astrophysics Data System (ADS)

Portillo, Salvador; Quarles, C. A.

2002-05-01

Absolute doubly differential bremsstrahlung cross sections for radiation at 90 from 25 and 50 keV electron bombardment of Kr and Xe of will be presented. The electrons were accelerated by a Cockcroft - Walton accelerator into an Al chamber through a .06" Al collimator. Thick target bremsstrahlung background was minimized by having Al nipples and fixtures and by the addition of a carbon lined nipple placed at 180 to the SiLi detector. A comparison of the doubly differential cross sections will be made with current bremsstrahlung theories. The ratio of the Kr and Xe cross sections will also be compared with the theoretical cross section ratios. The ratio provides a more sensitive test of the contribution, if any, of polarization bremsstrahlung.

Analysis of multi-fragmentation reactions induced by relativistic heavy ions using the statistical multi-fragmentation model

NASA Astrophysics Data System (ADS)

Ogawa, T.; Sato, T.; Hashimoto, S.; Niita, K.

2013-09-01

The fragmentation cross-sections of relativistic energy nucleus-nucleus collisions were analyzed using the statistical multi-fragmentation model (SMM) incorporated with the Monte-Carlo radiation transport simulation code particle and heavy ion transport code system (PHITS). Comparison with the literature data showed that PHITS-SMM reproduces fragmentation cross-sections of heavy nuclei at relativistic energies better than the original PHITS by up to two orders of magnitude. It was also found that SMM does not degrade the neutron production cross-sections in heavy ion collisions or the fragmentation cross-sections of light nuclei, for which SMM has not been benchmarked. Therefore, SMM is a robust model that can supplement conventional nucleus-nucleus reaction models, enabling more accurate prediction of fragmentation cross-sections.

Electron-Impact Excitation Cross Sections for Modeling Non-Equilibrium Gas

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Liu, Yen; Panesi, Marco; Munafo, Alessandro; Wray, Alan; Carbon, Duane F.

2015-01-01

In order to provide a database for modeling hypersonic entry in a partially ionized gas under non-equilibrium, the electron-impact excitation cross sections of atoms have been calculated using perturbation theory. The energy levels covered in the calculation are retrieved from the level list in the HyperRad code. The downstream flow-field is determined by solving a set of continuity equations for each component. The individual structure of each energy level is included. These equations are then complemented by the Euler system of equations. Finally, the radiation field is modeled by solving the radiative transfer equation.

SHIELD and HZETRN comparisons of pion production cross sections

NASA Astrophysics Data System (ADS)

Norbury, John W.; Sobolevsky, Nikolai; Werneth, Charles M.

2018-03-01

A program of comparing American (NASA) and Russian (ROSCOSMOS) space radiation transport codes has recently begun, and the first paper directly comparing the NASA and ROSCOSMOS space radiation transport codes, HZETRN and SHIELD respectively has recently appeared. The present work represents the second time that NASA and ROSCOSMOS calculations have been directly compared, and the focus here is on models of pion production cross sections used in the two transport codes mentioned above. It was found that these models are in overall moderate agreement with each other and with experimental data. Disagreements that were found are discussed.

Theoretical studies of photoexcitation and ionization in H2O

NASA Technical Reports Server (NTRS)

Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; Mckoy, B. V.; Langhoff, S. R.; Langhoff, P. W.

1982-01-01

Theoretical studies using Franck-Condon and static-exchange approximations are reported for the complete dipole excitation and ionization spectrum in H2O, where (1) large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground state equilibrium geometry, and (2) previously devised moment-theory techniques are employed in constructing the continuum oscillator-strength densities from the calculated spectra. Comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact-excitation cross sections, and dipole and synchrotron-radiation studies of partial-channel photoionization cross sections. The calculated partial-channel cross sections are found to be atomic-like, and dominated by 2p-kd components. It is suggested that the latter transition couples with the underlying 1b(1)-kb(1) channel, accounting for a prominent feature in recent synchrotron-radiation measurements.

Thermal neutron radiative capture cross-section of 186W(n, γ)187W reaction

NASA Astrophysics Data System (ADS)

Tan, V. H.; Son, P. N.

2016-06-01

The thermal neutron radiative capture cross section for 186W(n, γ)187W reaction was measured by the activation method using the filtered neutron beam at the Dalat research reactor. An optimal composition of Si and Bi, in single crystal form, has been used as neutron filters to create the high-purity filtered neutron beam with Cadmium ratio of Rcd = 420 and peak energy En = 0.025 eV. The induced activities in the irradiated samples were measured by a high resolution HPGe digital gamma-ray spectrometer. The present result of cross section has been determined relatively to the reference value of the standard reaction 197Au(n, γ)198Au. The necessary correction factors for gamma-ray true coincidence summing, and thermal neutron self-shielding effects were taken into account in this experiment by Monte Carlo simulations.

Cascades from nu_E above 1020 eV

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

Klein, Spencer R.

2004-12-21

At very high energies, the Landau-Pomeranchuk-Migdal effect reduces the cross sections for electron bremsstrahlung and photon e{sup +}e{sup -} pair production. The fractional electron energy loss and pair production cross sections drop as the energy increases. In contrast, the cross sections for photonuclear interactions grow with energy. In solids and liquids, at energies above 10{sup 20} eV, photonuclear reactions dominate, and showers that originate as photons or electrons quickly become hadronic showers. These electron-initiated hadronic showers are much shorter (due to the absence of the LPM effect), but wider than purely electromagnetic showers would be. This change in shape altersmore » the spectrum of the electromagnetic and acoustic radiation emitted from the shower. These alterations have important implications for existing and planned searches for radiation from u{sub e} induced showers above 10{sup 20} eV, and some existing limits should be reevaluated.« less

Extinction cross-section suppression and active acoustic invisibility cloaking

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2017-10-01

Invisibility in its canonical form requires rendering a zero extinction cross-section (or energy efficiency) from an active or a passive object. This work demonstrates the successful theoretical realization of this physical effect for an active cylindrically radiating acoustic body, undergoing periodic axisymmetric harmonic vibrations near a flat rigid boundary. Radiating, amplification and extinction cross-sections of the active source are defined. Assuming monopole and dipole modal oscillations of the circular source, conditions are found where the extinction energy efficiency factor of the active source vanishes, achieving total invisibility with minimal influence of the source size. It also takes positive or negative values, depending on its size and distance from the boundary. Moreover, the amplification energy efficiency factor is negative for the acoustically-active source. These effects also occur for higher-order modal oscillations of the active source. The results find potential applications in the development of acoustic cloaking devices and invisibility.

Insulating epoxy/barite and polyester/barite composites for radiation attenuation.

PubMed

El-Sarraf, M A; El-Sayed Abdo, A

2013-09-01

A trial has been made to create insulating Epoxy/Barite (EP/Brt) (ρ=2.85 g cm(-3)) and Crosslinked Unsaturated Polyester/Barite (CUP/Brt) (ρ=3.25 g cm(-3)) composites with radiation attenuation and shielding capabilities. Experimental work regarding mechanical and physical properties was performed to study the composites integrity for practical applications. The properties were found to be reasonable. Radiation attenuation properties have been carried out using emitted collimated beam from a fission (252)Cf (100 µg) neutron source, and the neutron-gamma spectrometer with stilbene scintillator. The pulse shape discriminating (P.S.D) technique based on the zero cross-over method was used to discriminate between neutron and gamma-ray pulses. Thermal neutron fluxes, measured using the BF3 detector and thermal neutron detection system, were used to plot the attenuation relations. The fast neutron macroscopic effective removal cross-section ΣR, gamma ray total attenuation coefficient µ and thermal neutron macroscopic cross-section Σ have been evaluated. Theoretical calculations have been achieved using MCNP-4C2 code to calculate ΣR, µ and Σ. Also, MERCSF-N program was used to calculate macroscopic effective removal cross-section ΣR. Measured and calculated results have been compared and were found to be in reasonable agreement. Copyright © 2013 Elsevier Ltd. All rights reserved.

Towards a quantitative, measurement-based estimate of the uncertainty in photon mass attenuation coefficients at radiation therapy energies

NASA Astrophysics Data System (ADS)

Ali, E. S. M.; Spencer, B.; McEwen, M. R.; Rogers, D. W. O.

2015-02-01

In this study, a quantitative estimate is derived for the uncertainty in the XCOM photon mass attenuation coefficients in the energy range of interest to external beam radiation therapy—i.e. 100 keV (orthovoltage) to 25 MeV—using direct comparisons of experimental data against Monte Carlo models and theoretical XCOM data. Two independent datasets are used. The first dataset is from our recent transmission measurements and the corresponding EGSnrc calculations (Ali et al 2012 Med. Phys. 39 5990-6003) for 10-30 MV photon beams from the research linac at the National Research Council Canada. The attenuators are graphite and lead, with a total of 140 data points and an experimental uncertainty of ˜0.5% (k = 1). An optimum energy-independent cross section scaling factor that minimizes the discrepancies between measurements and calculations is used to deduce cross section uncertainty. The second dataset is from the aggregate of cross section measurements in the literature for graphite and lead (49 experiments, 288 data points). The dataset is compared to the sum of the XCOM data plus the IAEA photonuclear data. Again, an optimum energy-independent cross section scaling factor is used to deduce the cross section uncertainty. Using the average result from the two datasets, the energy-independent cross section uncertainty estimate is 0.5% (68% confidence) and 0.7% (95% confidence). The potential for energy-dependent errors is discussed. Photon cross section uncertainty is shown to be smaller than the current qualitative ‘envelope of uncertainty’ of the order of 1-2%, as given by Hubbell (1999 Phys. Med. Biol 44 R1-22).

Pion Total Cross Section in Nucleon - Nucleon Collisions

NASA Technical Reports Server (NTRS)

Norbury, John W.

2009-01-01

Total cross section parameterizations for neutral and charged pion production in nucleon - nucleon collisions are compared to experimental data over the projectile momentum range from threshold to 300 GeV. Both proton - proton and proton - neutron reactions are considered. Overall excellent agreement between parameterizations and experiment is found, except for notable disagreements near threshold. In addition, the hypothesis that the neutral pion production cross section can be obtained from the average charged pion cross section is checked. The theoretical formulas presented in the paper obey this hypothesis for projectile momenta below 500 GeV. The results presented provide a test of engineering tools used to calculate the pion component of space radiation.

Photoabsorption cross section of acetylene in the EUV region

NASA Technical Reports Server (NTRS)

Wu, C. Y. R.; Judge, D. L.

1985-01-01

The measurement of the absolute photoabsorption cross sections of C2H2 in the 175-740 A region by means of a double ionization chamber is reported. The continuum background source is the synchrotron radiation emitted by the Wisconsin 240 MeV electron storage ring. It is found that the cross sections range from 2 to a maximum of 36 Mb. Two new Rydberg series are identified and the cross section data are applied in the analysis of various sum rules. From the rules, it is shown that the data of C2H2 in the 580-1088 A range may be too low, while the measured ionization transition moment may be too high.

MSG-7: Atmospheric Penetration of Solar Radiation in the Range of Schumann-runge Bands

NASA Technical Reports Server (NTRS)

Frederick, J. E.

1982-01-01

There have been major efforts in measuring extraterrestrial solar irradiance for use in atmospheric studies. The quantity of immediate relevance to theoretical studies is the number of photons which reach a given altitude in the middle atmosphere. Current models compute the attenuated radiation field but the cross sections available for the major absorbers, O2 and O3, often come from experiments that are now quite old. Balloon measurements show some significant differences between the predicted and observed ultraviolet radiation field between 30 and 40 km. The wavelength region to be studied includes Lyman alpha plus the range 175 nm to the visible. Specific topics to be addressed are as follows: (1) the cross sections of the major absorbers, O2 and O3 including the Schumann-Runge bands as a subset; (2) comparison of the in situ measurements of the attenuated radiation field with calculations; and (3) the relevance of the scattered and reflected radiation fields for middle atmospheric processes.

MSG-7: atmospheric penetration of solar radiation in the range of Schumann-Runge bands

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

Frederick, J.E.

1982-12-01

There have been major efforts in measuring extraterrestrial solar irradiance for use in atmospheric studies. The quantity of immediate relevance to theoretical studies is the number of photons which reach a given altitude in the middle atmosphere. Current models compute the attenuated radiation field but the cross sections available for the major absorbers, O2 and O3, often come from experiments that are now quite old. Balloon measurements show some significant differences between the predicted and observed ultraviolet radiation field between 30 and 40 km. The wavelength region to be studied includes Lyman alpha plus the range 175 nm to themore » visible. Specific topics to be addressed are as follows: (1) the cross sections of the major absorbers, O2 and O3 including the Schumann-Runge bands as a subset (2) comparison of the in situ measurements of the attenuated radiation field with calculations and (3) the relevance of the scattered and reflected radiation fields for middle atmospheric processes.« less

Infrared absorption cross sections of alternative CFCs

NASA Technical Reports Server (NTRS)

Clerbaux, Cathy; Colin, Reginald; Simon, Paul C.

1994-01-01

Absorption cross sections have obtained in the infrared atmospheric window, between 600 and 1500 cm(exp -1), for 10 alternative hydrohalocarbons: HCFC-22, HCFC-123, HCFC-124, HCFC-141b, HCFC-142b, HCFC-225ca, HCFC-225cb, HFC-125, HFC-134a, and HFC-152a. The measurements were made at three temperatures (287K, 270K and 253K) with a Fourier transform spectrometer operating at 0.03 cm(exp -1) apodized resolution. Integrated cross sections are also derived for use in radiative models to calculate the global warming potentials.

Terahertz wide aperture reflection tomography.

PubMed

Pearce, Jeremy; Choi, Hyeokho; Mittleman, Daniel M; White, Jeff; Zimdars, David

2005-07-01

We describe a powerful imaging modality for terahertz (THz) radiation, THz wide aperture reflection tomography (WART). Edge maps of an object's cross section are reconstructed from a series of time-domain reflection measurements at different viewing angles. Each measurement corresponds to a parallel line projection of the object's cross section. The filtered backprojection algorithm is applied to recover the image from the projection data. To our knowledge, this is the first demonstration of a reflection computed tomography technique using electromagnetic waves. We demonstrate the capabilities of THz WART by imaging the cross sections of two test objects.

Neutron Capture Cross Sections and Gamma Emission Spectra from Neutron Capture on 234,236,238U Measured with DANCE

NASA Astrophysics Data System (ADS)

Ullmann, J. L.; Mosby, S.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Jandel, M.; Kawano, T.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wilhelmy, J. B.; Wu, C.-Y.; Becker, J. A.; Chyzh, A.; Baramsai, B.; Mitchell, G. E.; Krticka, M.

2014-05-01

A new measurement of the 238U(n, γ) cross section using a thin 48 mg/cm2 target was made using the DANCE detector at LANSCE over the energy range from 10 eV to 500 keV. The results confirm earlier measurements. Measurements of the gamma-ray emission spectra were also made for 238U(n, γ) as well as 234,236U(n, γ). These measurements help to constrain the radiative strength function used in the cross-section calculations.

Optical tractor Bessel polarized beams

NASA Astrophysics Data System (ADS)

Mitri, F. G.; Li, R. X.; Guo, L. X.; Ding, C. Y.

2017-01-01

Axial and transverse radiation force cross-sections of optical tractor Bessel polarized beams are theoretically investigated for a dielectric sphere with particular emphasis on the beam topological charge (or order), half-cone angle and polarization. The angular spectrum decomposition method (ASDM) is used to derive the non-paraxial electromagnetic (EM) field components of the Bessel beams. The multipole expansion method using vector spherical harmonics is utilized and appropriate beam-shape coefficients are derived in order to compute the radiation force cross-sections. The analysis has no limitation to a particular range of frequencies such that the Rayleigh, Mie or geometrical optics regimes can all be considered effectively using the present rigorous formalism. The focus of this investigation is to identify some of the tractor beam conditions so as to achieve retrograde motion of a dielectric sphere located arbitrarily in space. Numerical computations for the axial and transverse radiation force cross-sections are presented for linear, right-circular, radial, azimuthal and mixed polarizations of the individual plane waves forming the Bessel beams of zeroth- and first-order (with positive or negative helicity), respectively. As the sphere shifts off the beam's axis, the axial pulling (tractor) force is weakened. Moreover, the transverse radiation force cross-section field changes with the sphere's size factor ka (where k is the wavenumber and a is the sphere radius). Both stable and unstable equilibrium regions around the beam's axis are found, depending on the choice of ka and the half-cone angle α0. These results are particularly important in the development of emergent technologies for the photophoretic assembly of optically-engineered (meta)materials with designed properties using optical tractor (vortex) beams, particle manipulation, levitation and positioning, and other applications.

A Binary-Encounter-Bethe Approach to Simulate DNA Damage by the Direct Effect

NASA Technical Reports Server (NTRS)

Plante, Ianik; Cucinotta, Francis A.

2013-01-01

The DNA damage is of crucial importance in the understanding of the effects of ionizing radiation. The main mechanisms of DNA damage are by the direct effect of radiation (e.g. direct ionization) and by indirect effect (e.g. damage by.OH radicals created by the radiolysis of water). Despite years of research in this area, many questions on the formation of DNA damage remains. To refine existing DNA damage models, an approach based on the Binary-Encounter-Bethe (BEB) model was developed[1]. This model calculates differential cross sections for ionization of the molecular orbitals of the DNA bases, sugars and phosphates using the electron binding energy, the mean kinetic energy and the occupancy number of the orbital. This cross section has an analytic form which is quite convenient to use and allows the sampling of the energy loss occurring during an ionization event. To simulate the radiation track structure, the code RITRACKS developed at the NASA Johnson Space Center is used[2]. This code calculates all the energy deposition events and the formation of the radiolytic species by the ion and the secondary electrons as well. We have also developed a technique to use the integrated BEB cross section for the bases, sugar and phosphates in the radiation transport code RITRACKS. These techniques should allow the simulation of DNA damage by ionizing radiation, and understanding of the formation of double-strand breaks caused by clustered damage in different conditions.

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

Ullmann, John Leonard; Couture, Aaron Joseph; Koehler, Paul E.

An accurate knowledge of the neutron capture cross section is important for many applications. Experimental measurements are important since theoretical calculations of capture have been notoriously difficult, with the ratio of measured to calculated cross sections often a factor of 2 or more in the 10 keV to 1 MeV region. However, a direct measurement of capture cannot be made on many interesting radioactive nuclides because of their short half-life or backgrounds caused by their nuclear decay. On the other hand, neutron transmission measurements of the total cross section are feasible for a wide range of radioactive nuclides since themore » detectors are far from the sample, and often are less sensitive to decay radiation. The parameters extracted from a total cross section measurement, which include the average resonance spacing, the neutron strength function, and the average total radiation width, (Γ γ), provide tight constraints on the calculation of the capture cross section, and when applied produce much more accurate results. These measurements can be made using the intense epithermal neutron flux at the Lujan Center on relatively small quantities of target material. It was the purpose of this project to investigate and develop the capability to make these measurements. A great deal of progress was made towards establishing this capability during 2016, including setting up the flight path and obtaining preliminary results, but more work remains to be done.« less

Angle-Differential Cross Sections for Radiative Recombination and the Photoelectric Effect in the K, L, and M Shells of One-Electron Systems Calculated Within AN Exact Relativistic Description

NASA Astrophysics Data System (ADS)

Ichihara, Akira; Eichler, Jörg

2001-11-01

An extensive tabulation of angle-differential cross sections for radiative recombination and, consequently, for the photoelectric effect of hydrogen-like ions with representative charge numbers Z=18, 36, 54, 66, 79, 82, and 92 is presented for the K, L, and M shells and electron energies ranging from 1.0 keV to 1.5 MeV. The cross sections, accurate to three digits, are based on fully relativistic calculations including the effects of the finite nuclear size and all multipole orders of the photon field. In order to provide a good overview, the following procedure has been adopted: For the charge numbers 18, 54, and 92, the differential cross sections are presented in figures for all subshells and for representative energies. Furthermore, as a sample of the calculations, we present a complete table for the case of Z=79. The full tabulation for all charge numbers mentioned above is provided in electronic form (http://www.idealibrary.com/links/doi/10.1006/adnd.2001.0868/dat). By simple scaling, the dependence on the projectile energy in MeV/u can be derived for accelerator experiments, and, by using elementary formulas, the differential cross section for the photoelectric effect as a function of the electron emission angle can also be obtained.

Sequence dependence of electron-induced DNA strand breakage revealed by DNA nanoarrays

PubMed Central

Keller, Adrian; Rackwitz, Jenny; Cauët, Emilie; Liévin, Jacques; Körzdörfer, Thomas; Rotaru, Alexandru; Gothelf, Kurt V.; Besenbacher, Flemming; Bald, Ilko

2014-01-01

The electronic structure of DNA is determined by its nucleotide sequence, which is for instance exploited in molecular electronics. Here we demonstrate that also the DNA strand breakage induced by low-energy electrons (18 eV) depends on the nucleotide sequence. To determine the absolute cross sections for electron induced single strand breaks in specific 13 mer oligonucleotides we used atomic force microscopy analysis of DNA origami based DNA nanoarrays. We investigated the DNA sequences 5′-TT(XYX)3TT with X = A, G, C and Y = T, BrU 5-bromouracil and found absolute strand break cross sections between 2.66 · 10−14 cm2 and 7.06 · 10−14 cm2. The highest cross section was found for 5′-TT(ATA)3TT and 5′-TT(ABrUA)3TT, respectively. BrU is a radiosensitizer, which was discussed to be used in cancer radiation therapy. The replacement of T by BrU into the investigated DNA sequences leads to a slight increase of the absolute strand break cross sections resulting in sequence-dependent enhancement factors between 1.14 and 1.66. Nevertheless, the variation of strand break cross sections due to the specific nucleotide sequence is considerably higher. Thus, the present results suggest the development of targeted radiosensitizers for cancer radiation therapy. PMID:25487346

47 CFR 15.11 - Cross reference.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Cross reference. 15.11 Section 15.11 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES General § 15.11 Cross reference. The provisions of subparts A, H, I, J and K of part 2 apply to intentional and unintentional radiators...

Radiation and scattering by thin-wire structures in the complex frequency domain. [electromagnetic theory for thin-wire antennas

NASA Technical Reports Server (NTRS)

Richmond, J. H.

1974-01-01

Piecewise-sinusoidal expansion functions and Galerkin's method are employed to formulate a solution for an arbitrary thin-wire configuration in a homogeneous conducting medium. The analysis is performed in the real or complex frequency domain. In antenna problems, the solution determines the current distribution, impedance, radiation efficiency, gain and far-field patterns. In scattering problems, the solution determines the absorption cross section, scattering cross section and the polarization scattering matrix. The electromagnetic theory is presented for thin wires and the forward-scattering theorem is developed for an arbitrary target in a homogeneous conducting medium.

On the relativistic field theory model of the deuteron II

NASA Astrophysics Data System (ADS)

Ivanov, A. N.; Troitskaya, N. I.; Faber, M.; Oberhummer, H.

1997-02-01

The relativistic field theory model of the deuteron suggested previously is revised and applied to the calculation of the cross sections of the low-energy radiative neutron-proton capture n + p -> D + γ and the low-energy two-proton fusion p + p -> D + e+ + νc. For the low-energy radiative neutron-proton capture n + p -> D + γ our result agrees well with both experimental data and the potential model prediction. In the case of the two-proton fusion the cross section obtained is 2.9 times as much as that given by the potential approach. The obtained result is discussed in connection with the solar neutrino problem.

Covariances for the 56Fe radiation damage cross sections

NASA Astrophysics Data System (ADS)

Simakov, Stanislav P.; Koning, Arjan; Konobeyev, Alexander Yu.

2017-09-01

The energy-energy and reaction-reaction covariance matrices were calculated for the n + 56Fe damage cross-sections by Total Monte Carlo method using the TENDL-2013 random files. They were represented in the ENDF-6 format and added to the unperturbed evaluation file. The uncertainties for the spectrum averaged radiation quantities in the representative fission, fusion and spallation facilities were first time assessed as 5-25%. Additional 5 to 20% have to be added to the atom displacement rate uncertainties to account for accuracy of the primary defects simulation in materials. The reaction-reaction correlation were shown to be 1% or less.

Track structure: time evolution from physics to chemistry.

PubMed

Dingfelder, M

2006-01-01

This review discusses interaction cross sections of charged particles (electrons, protons, light ions) with atoms and molecules. The focus is on biological relevant targets like liquid water which serves as a substitute of soft tissue in most Monte Carlo codes. The spatial distribution of energy deposition patterns by different radiation qualities and their importance to the time evolution from the physical to the chemical stage or radiation response is discussed. The determination of inelastic interaction cross sections for charged particles in condensed matter is discussed within the relativistic plane-wave Born approximation and semi-empirical models. The dielectric-response-function of liquid water is discussed.

Charge equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

NASA Technical Reports Server (NTRS)

Rule, D. W.; Omidvar, K.

1979-01-01

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, are considered. Electron loss of the beam has been taken into account by means of the first Born approximation, allowing for the target atom to remain unexcited or to be excited to all possible states. Electron-capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms and capture into all excited states of the projectile. The capture and loss cross sections are found to be within 20%-30% of the existing experimental values for most of the cases considered. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation, and collisional inner-shell ionization, taking into account the fluorescence yield of the ions, has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated, and error estimates made for the results.

Measurement of electron impact collisional excitation cross sections of Ni to Ge-like gold

DOE PAGES

May, M. J.; Beiersdorfer, P.; Jordan, N.; ...

2017-03-01

We have measured the collisional excitation cross sections for the 3d→4f and 3d→5f excitations in Au ions near the Ni-like charge state by using beam plasmas created in the Livermore electron beam ion trap EBIT-I. The cross sections have been experimentally determined at approximately 1, 2 and 3 keV above the threshold energy, ET, for the 3d→4f excitations (ET ~2.5 keV) and at approximately 0.1, 1 and 2 keV above the threshold energy for the 3d→5f excitations (ET ~3.3 keV). The cross section measurements were made possible by using the GSFC x-ray microcalorimeter at the Livermore EBIT facility. The absolutemore » cross sections are determined from the ratio of the intensity of the collisionally excited bound-bound transitions to the intensity of the radiative recombination lines produced in EBIT-I plasmas. The effects of polarization and Auger decay channels are accounted for in the cross section determination. Measured cross sections are compared with those from HULLAC, DWS and FAC calculations. Finally, the measurements demonstrate that some errors exist in the calculated excitation cross sections.« less

Measurement of electron impact collisional excitation cross sections of Ni to Ge-like gold

NASA Astrophysics Data System (ADS)

May, M. J.; Beiersdorfer, P.; Jordan, N.; Scofield, J. H.; Reed, K. J.; Brown, G. V.; Hansen, S. B.; Porter, F. S.; Kelley, R.; Kilbourne, C. A.; Boyce, K. R.

2017-03-01

We have measured the collisional excitation cross sections for the 3d→4f and 3d→5f excitations in Au ions near the Ni-like charge state by using beam plasmas created in the Livermore electron beam ion trap EBIT-I. The cross sections have been experimentally determined at approximately 1, 2 and 3 keV above the threshold energy, ET, for the 3d→4f excitations (ET ˜ 2.5 keV) and at approximately 0.1, 1 and 2 keV above the threshold energy for the 3d→5f excitations (ET ˜ 3.3 keV). The cross section measurements were made possible by using the GSFC x-ray microcalorimeter at the Livermore EBIT facility. The absolute cross sections are determined from the ratio of the intensity of the collisionally excited bound-bound transitions to the intensity of the radiative recombination lines produced in EBIT-I plasmas. The effects of polarization and Auger decay channels are accounted for in the cross section determination. Measured cross sections are compared with those from HULLAC, DWS and FAC calculations. The measurements demonstrate that some errors exist in the calculated excitation cross sections.

Total absorption cross sections of several gases of aeronomic interest at 584 A.

NASA Technical Reports Server (NTRS)

Starr, W. L.; Loewenstein, M.

1972-01-01

Total photoabsorption cross sections have been measured at 584.3 A for N2, O2, Ar, CO2, CO, NO, N2O, NH3, CH4, H2, and H2S. A monochromator was used to isolate the He I 584 line produced in a helium resonance lamp, and thin aluminum filters were used as absorption cell windows, thereby eliminating possible errors associated with the use of undispersed radiation or windowless cells. Sources of error are examined, and limits of uncertainty are given. Previous relevant cross-sectional measurements and possible error sources are reviewed. Wall adsorption as a source of error in cross-sectional measurements has not previously been considered and is discussed briefly.

Derived Born cross sections of e+e‑ annihilation into open charm mesons from CLEO-c measurements

NASA Astrophysics Data System (ADS)

Dong, Xiang-Kun; Wang, Liang-Liang; Yuan, Chang-Zheng

2018-04-01

The exclusive Born cross sections of the production of D0, D+ and {{{D}}}{{s}}{{+}} mesons in e+e‑ annihilation at 13 energy points between 3.970 and 4.260 GeV are obtained by applying corrections for initial state radiation and vacuum polarization to the observed cross sections measured by the CLEO-c experiment. Both the statistical and the systematic uncertainties for the obtained Born cross sections are estimated. Supported in part by National Natural Science Foundation of China (NSFC) (11235011, 11475187, 11521505, U1632106), the Ministry of Science and Technology of China (2015CB856701), Key Research Program of Frontier Sciences, CAS, (QYZDJ-SSW-SLH011) and the CAS Center for Excellence in Particle Physics (CCEPP)

Radiation Transport and Shielding for Space Exploration and High Speed Flight Transportation

NASA Technical Reports Server (NTRS)

Maung, Khin Maung; Trapathi, R. K.

1997-01-01

Transportation of ions and neutrons in matter is of direct interest in several technologically important and scientific areas, including space radiation, cosmic ray propagation studies in galactic medium, nuclear power plants and radiological effects that impact industrial and public health. For the proper assessment of radiation exposure, both reliable transport codes and accurate data are needed. Nuclear cross section data is one of the essential inputs into the transport codes. In order to obtain an accurate parametrization of cross section data, theoretical input is indispensable especially for processes where there is little or no experimental data available. In this grant period work has been done on the studies of the use of relativistic equations and their one-body limits. The results will be useful in choosing appropriate effective one-body equation for reaction calculations. Work has also been done to improve upon the data base needed for the transport codes used in the studies of radiation transport and shielding for space exploration and high speed flight transportation. A phenomenological model was developed for the total absorption cross sections valid for any system of charged and/or uncharged collision pairs for the entire energy range. The success of the model is gratifying. It is being used by other federal agencies, national labs and universities. A list of publications based on the work during the grant period is given below and copies are enclosed with this report.

Electron induced inelastic and ionization cross section for plasma modeling

NASA Astrophysics Data System (ADS)

Verma, Pankaj; Mahato, Dibyendu; Kaur, Jaspreet; Antony, Bobby

2016-09-01

The present paper reports electron impact total inelastic and ionization cross section for silicon, germanium, and tin tetrahalides at energies varying from ionization threshold of the target to 5000 eV. These cross section data over a wide energy domain are very essential to understand the physico-chemical processes involved in various environments such as plasma modeling, semiconductor etching, atmospheric sciences, biological sciences, and radiation physics. However, the cross section data on the above mentioned molecules are scarce. In the present article, we report the computation of total inelastic cross section using spherical complex optical potential formalism and the estimation of ionization cross section through a semi-empirical method. The present ionization cross section result obtained for SiCl4 shows excellent agreement with previous measurements, while other molecules have not yet been investigated experimentally. Present results show more consistent behaviour than previous theoretical estimates. Besides cross sections, we have also studied the correlation of maximum ionization cross section with the square root of the ratio of polarizability to ionization potential for the molecules with known polarizabilities. A linear relation is observed between these quantities. This correlation is used to obtain approximate polarizability volumes for SiBr4, SiI4, GeCl4, GeBr4, and GeI4 molecules.

Cross Sections for Balmer-Alpha Excitation in Heavy Particle Collisions.

NASA Astrophysics Data System (ADS)

Bae, Young Kun

Doppler shifted and unshifted Balmer-alpha radiation has been observed in the absolute sense for energetic H('+), H(,2)('+) and H(,3)('+) ions incident on molecular hydrogen by the method of decay inside the target within the energy range of 20 keV to 150 keV. Most of the measurements were based on single-collision conditions, but a simple thick -target experiment has been tried for the case of dissociative excitation of the target molecules by H atoms. The Balmer-alpha radiation emitted by hydrogen and deuterium beams has been used as a diagnostic method of neutral beam parameters. One important neutral beam parameter is the species mix between H('+), H(,2)('+) and H(,3)('+) ion currents produced by the ion source and accelerator. This species mix can be resolved by analysis of the Balmer-alpha radiation if the beam is observed along an off normal axis with sufficient spectral resolution to separate the Doppler shifted radiation components from each other. An impediment to this approach to measuring the ion species is that some of the required cross sections have not been measured. This is the motivation for the presented experimental work. A home made monochromator gave enough optical throughput and spectral resolution for separation of the Doppler shifted lines from the unshifted lines. By selectively varying the target pressure and the distance of travel into the target prior to the observation region, excitation cross sections for three different angular momentum states (3s, 3p and 3d) have been determined. Combinations of a linear polarizer and a half-wave plate were used for polarization measurement. Separation of the individual Zeeman levels have been tried for the 3p state from the information obtained from the polarization. Theoretical estimates of the cascading corrections have been applied in the case of both thin and thick targets. The intensity development equations for thick targets also have been derived. Cross sections for 3s production show general agreement with previous measurements, while those for 3p and 3d differ by as much as a factor of two. Target dissociative excitation cross sections show good agreement with previous measurements except those measured by Williams, et al..

The S-Process Branching-Point at 205PB

NASA Astrophysics Data System (ADS)

Tonchev, Anton; Tsoneva, N.; Bhatia, C.; Arnold, C. W.; Goriely, S.; Hammond, S. L.; Kelley, J. H.; Kwan, E.; Lenske, H.; Piekarewicz, J.; Raut, R.; Rusev, G.; Shizuma, T.; Tornow, W.

2017-09-01

Accurate neutron-capture cross sections for radioactive nuclei near the line of beta stability are crucial for understanding s-process nucleosynthesis. However, neutron-capture cross sections for short-lived radionuclides are difficult to measure due to the fact that the measurements require both highly radioactive samples and intense neutron sources. We consider photon scattering using monoenergetic and 100% linearly polarized photon beams to obtain the photoabsorption cross section on 206Pb below the neutron separation energy. This observable becomes an essential ingredient in the Hauser-Feshbach statistical model for calculations of capture cross sections on 205Pb. The newly obtained photoabsorption information is also used to estimate the Maxwellian-averaged radiative cross section of 205Pb(n,g)206Pb at 30 keV. The astrophysical impact of this measurement on s-process nucleosynthesis will be discussed. This work was performed under the auspices of US DOE by LLNL under Contract DE-AC52-07NA27344.

A new compilation of experimental nuclear data for total reaction cross sections

NASA Astrophysics Data System (ADS)

Lantz, Mattias; Sihver, L.

The nucleon-nucleus and nucleus-nucleus total reaction cross sections are of importance in many different fields, both for a better theoretical understanding as well as for a number of applications, including space radiation dosimetry. We have performed a comprehensive literature study in order to find all available experimental data on total reaction cross sections, σR , and interaction cross sections, σI , for neutrons, protons, and all stable and exotic heavy ions. Excluded from the data base are measurements where the cross sections have been derived through model-dependent calculations from other kinds of measurements. The objective of the study is to identify where more measurements are needed in view of different applications, and to make the data easily available for model developers and experimentalists. We will present some examples from the study, which is in the stage of quality control of all the gathered data.

L X-ray fluorescence cross sections of some rare earth elements ( Z = 62, 64, 66, 68 and 70) at 17.8, 22.6 and 25.8 keV

NASA Astrophysics Data System (ADS)

Mandal, A. C.; Santra, S.; Mitra, D.; Sarkar, M.; Bhattacharya, D.

2005-06-01

L X-ray fluorescence cross sections of the elements with Z = 62, 64, 66, 68 and 70 have been measured at 17.8, 22.6 and 25.8 keV using an X-ray tube and secondary exciters of Mo, Ag and Sn. The measured cross sections have been compared with the theoretical predictions and with the data of others. Theoretical values calculated using photoionisation cross sections from Scofield [Lawrence Livermore Laboratory, UCRL-51326, 1973], fluorescence yields and Coster-Kronig transition probabilities from Puri et al. [X-ray Spectrom. 22 (1993) 358] and radiative widths from Campbell and Wang [At. Data Nucl. Data Tables 43 (1989) 281] show good agreement with our data. Except two sets of data on Lγ cross sections, all the data of other groups agree well with those of ours.

Microcircuit radiation effects databank

NASA Technical Reports Server (NTRS)

1983-01-01

Radiation test data submitted by many testers is collated to serve as a reference for engineers who are concerned with and have some knowledge of the effects of the natural radiation environment on microcircuits. Total dose damage information and single event upset cross sections, i.e., the probability of a soft error (bit flip) or of a hard error (latchup) are presented.

Pion and Kaon Lab Frame Differential Cross Sections for Intermediate Energy Nucleus-Nucleus Collisions

NASA Technical Reports Server (NTRS)

Norbury, John W.; Blattnig, Steve R.

2008-01-01

Space radiation transport codes require accurate models for hadron production in intermediate energy nucleus-nucleus collisions. Codes require cross sections to be written in terms of lab frame variables and it is important to be able to verify models against experimental data in the lab frame. Several models are compared to lab frame data. It is found that models based on algebraic parameterizations are unable to describe intermediate energy differential cross section data. However, simple thermal model parameterizations, when appropriately transformed from the center of momentum to the lab frame, are able to account for the data.

Geometric effect on second harmonic generation from gold grating

NASA Astrophysics Data System (ADS)

Lu, Jiao; Ding, Baoyong; Huo, Yanyan; Ning, Tingyin

2018-05-01

We numerically investigate second harmonic generation from gold gratings of an ideal rectangular and ladder-shaped cross-section. The SHG efficiency from the gold gratings of the ladder-shaped cross-section is significantly enhanced compared with that from the ideal rectangular cross-section with a maximum enhancement factor of around two. The enhancement is ascribe to the nanostructure dependent local fundamental electric field, the nonlinear sources and thus the far field radiation. Our results have a practical meaning in the explanation of experimental SHG measurement, and the modulation of SHG response in the metallic nanostructure.

Subtraction method of computing QCD jet cross sections at NNLO accuracy

NASA Astrophysics Data System (ADS)

Trócsányi, Zoltán; Somogyi, Gábor

2008-10-01

We present a general subtraction method for computing radiative corrections to QCD jet cross sections at next-to-next-to-leading order accuracy. The steps needed to set up this subtraction scheme are the same as those used in next-to-leading order computations. However, all steps need non-trivial modifications, which we implement such that that those can be defined at any order in perturbation theory. We give a status report of the implementation of the method to computing jet cross sections in electron-positron annihilation at the next-to-next-to-leading order accuracy.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Surface hardening of steels with a strip-shaped beam of a high-power CO2 laser

NASA Astrophysics Data System (ADS)

Dubovskii, P. E.; Kovsh, Ivan B.; Strekalova, M. S.; Sisakyan, I. N.

1994-12-01

A comparative analysis was made of the surface hardening of steel 45 by high-power CO2 laser beams with a rectangular strip-like cross section and a traditional circular cross section. This was done under various conditions. The treatment with the strip-like beam ensured a higher homogeneity of the hardened layer and made it possible to increase the productivity by a factor of 2-4 compared with the treatment by a beam of the same power but with a circular cross section.

Broadband Via-Less Microwave Crossover Using Microstrip-CPW Transitions

NASA Technical Reports Server (NTRS)

Stevenson, Thomas; U-Yen, Kongpop; Wollack, Edward; Moseley, Samuel; Hsieh, Wen-Ting

2011-01-01

The front-to-back interface between microstrip and CPW (coplanar waveguide) typically requires complex fabrication or has high radiation loss. The microwave crossover typically requires a complex fabrication step. The prior art in microstrip-CPW transition requires a physical vias connection between the microstrip and CPW line on a separate layer. The via-less version of this transition was designed empirically and does not have a close form solution. The prior art of the micro wave crossover requires either additional substrate or wire bond as an air bridge to isolate two microwave lines at the crossing junction. The disadvantages are high radiation loss, no analytical solution to the problem, lengthy simulation time, and complex fabrication procedures to generate air bridges or via. The disadvantage of the prior crossover is a complex fabrication procedure, which also affects the device reliability and yield. This microstrip-CPW transition is visualized as two microstrip-slotline transitions combined in a way that the radiation from two slotlines cancels each other out. The invention is designed based on analytical methods; thus, it significantly reduces the development time. The crossover requires no extra layer to cross two microwave signals and has low radiation loss. The invention is simple to fabricate and design. It produces low radiation loss and can be designed with low insertion loss, with some tradeoff with signal isolation. The microstrip-CPW transition is used as an interface to connect between the device and the circuit outside the package. The via-less microwave crossover is used to allow two signals to cross without using an extra layer or fabrication processing step to enable this function. This design allows the solution to be determined entirely though analytical techniques. In addition, a planar via-less microwave crossover using this technique was proposed. The experimental results show that the proposed crossover at 5 GHz has a minimum isolation of 32 dB. It also has low in-band insertion loss and return loss of 1.2 dB and 18 dB, respectively, over more than 44 percent of bandwidth at room temperature. This microstrip-CPW transition requires the microstrip line to be split into two sections. Each section is connected to a microstrip quarter-wavelength openended stub. A slotline is also placed perpendicular to the microstrip section. The slot is connected to a grounded-end quarter-wavelength slotline and generates a microstrip-slotline transition. When two of these sections are placed in parallel and with the microstrip section combined at transition, a microstrip- CPW transition is formed. The slotline radiation is suppressed as two slots are excited with the electric field in an opposite direction, which cancels the radiation in far field. The invention on the crossover consists of the invented microstrip-CPW transitions combined back-to-back and a microstrip low-pass filter. One signal is crossed through to the microstrip layer, while the other signal is crossed through the CPW line located on the ground plane of the microstrip line. The microstrip low-pass filter produces a narrow line at the crossing point to enhance the system isolation. It also produces broadband response in the operating frequency band. The microstrip-CPW transition allows a microwave signal to travel from microstrip line to CPW line with low radiation loss. The crossover allows two microwave signals to cross with minimal parasitic coupling.

40 CFR 192.31 - Definitions and cross-references.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Definitions and cross-references. 192.31 Section 192.31 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION... as practicable considering technological feasibility means as quickly as possible considering: the...

40 CFR 192.31 - Definitions and cross-references.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Definitions and cross-references. 192.31 Section 192.31 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION... as practicable considering technological feasibility means as quickly as possible considering: the...

40 CFR 192.31 - Definitions and cross-references.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Definitions and cross-references. 192.31 Section 192.31 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION... as practicable considering technological feasibility means as quickly as possible considering: the...

Photoionization research on atomic radiation. 3: The ionization cross section of atomic nitrogen

NASA Technical Reports Server (NTRS)

Comes, F. J.; Elzer, A.

1982-01-01

The photoionization cross section of atomic nitrogen was measured between the ionization limit and 432 A. The experimental values are well fitted by those from a calculation of HENRY due to the dipole velocity approximation. A Rydberg series converging to the 5S-state of the ion is clearly identified from the ionization measurements and is shown to ionize.

NASA study of cataract in astronauts (NASCA). Report 1: Cross-sectional study of the relationship of exposure to space radiation and risk of lens opacity.

PubMed

Chylack, Leo T; Peterson, Leif E; Feiveson, Alan H; Wear, Mary L; Manuel, F Keith; Tung, William H; Hardy, Dale S; Marak, Lisa J; Cucinotta, Francis A

2009-07-01

The NASA Study of Cataract in Astronauts (NASCA) is a 5-year longitudinal study of the effect of space radiation exposure on the severity/progression of nuclear, cortical and posterior subcapsular (PSC) lens opacities. Here we report on baseline data that will be used over the course of the longitudinal study. Participants include 171 consenting astronauts who flew at least one mission in space and a comparison group made up of three components: (a) 53 astronauts who had not flown in space, (b) 95 military aircrew personnel, and (c) 99 non-aircrew ground-based comparison subjects. Continuous measures of nuclear, cortical and PSC lens opacities were derived from Nidek EAS 1000 digitized images. Age, demographics, general health, nutritional intake and solar ocular exposure were measured at baseline. Astronauts who flew at least one mission were matched to comparison subjects using propensity scores based on demographic characteristics and medical history stratified by gender and smoking (ever/never). The cross-sectional data for matched subjects were analyzed by fitting customized non-normal regression models to examine the effect of space radiation on each measure of opacity. The variability and median of cortical cataracts were significantly higher for exposed astronauts than for nonexposed astronauts and comparison subjects with similar ages (P=0.015). Galactic cosmic space radiation (GCR) may be linked to increased PSC area (P=0.056) and the number of PSC centers (P=0.095). Within the astronaut group, PSC size was greater in subjects with higher space radiation doses (P=0.016). No association was found between space radiation and nuclear cataracts. Cross-sectional data analysis revealed a small deleterious effect of space radiation for cortical cataracts and possibly for PSC cataracts. These results suggest increased cataract risks at smaller radiation doses than have been reported previously.

High-Energy Electron-Induced SEUs and Jovian Environment Impact

NASA Astrophysics Data System (ADS)

Tali, Maris; Alía, Rubén García; Brugger, Markus; Ferlet-Cavrois, Veronique; Corsini, Roberto; Farabolini, Wilfrid; Mohammadzadeh, Ali; Santin, Giovanni; Virtanen, Ari

2017-08-01

We present experimental evidence of electron-induced upsets in a reference European Space Agency (ESA) single event upset (SEU) monitor, induced by a 200-MeV electron beam at the Very energetic Electronic facility for Space Planetary Exploration in harsh Radiation environments facility at CERN. Comparison of experimental cross sections and simulated cross sections is shown and the differences are analyzed. Possible secondary contributions to the upset rate by neutrons, flash effects, and cumulative dose effects are discussed, showing that electronuclear reactions are the expected SEU mechanism. The ESA Jupiter Icy Moons Explorer mission, to be launched in 2022, presents a challenging radiation environment due to the intense high-energy electron flux in the trapped radiation belts. Insight is given to the possible contribution of electrons to the overall upset rates in the Jovian radiation environment. Relative contributions of both typical electron and proton spectra created when the environmental spectra are transported through a typical spacecraft shielding are shown and the different mission phases are discussed.

Application of continuous-wave terahertz computed tomography for the analysis of chicken bone structure

NASA Astrophysics Data System (ADS)

Li, Bin; Wang, Dayong; Rong, Lu; Zhai, Changchao; Wang, Yunxin; Zhao, Jie

2018-02-01

Terahertz (THz) radiation is able to penetrate many different types of nonpolar and nonmetallic materials without the damaging effects of x-rays. THz technology can be combined with computed tomography (CT) to form THz CT, which is an effective imaging method that is used to visualize the internal structure of a three-dimensional sample as cross-sectional images. Here, we reported an application of THz as the radiation source in CT imaging by replacing the x-rays. In this method, the sample cross section is scanned in all translation and rotation directions. Then, the projection data are reconstructed using a tomographic reconstruction algorithm. Two-dimensional (2-D) cross-sectional images of the chicken ulna were obtained through the continuous-wave (CW) THz CT system. Given by the difference of the THz absorption of different substances, the compact bone and spongy bone inside the chicken ulna are structurally distinguishable in the 2-D cross-sectional images. Using the filtered back projection algorithm, we reconstructed the projection data of the chicken ulna at different projection angle intervals and found that the artifacts and noise in the images are strikingly increased when the projection angle intervals become larger, reflected by the blurred boundary of the compact bone. The quality and fidelity of the 2-D cross-sectional images could be substantially improved by reducing the projection angle intervals. Our experimental data demonstrated a feasible application of the CW THz CT system in biological imaging.

Low-Energy Electron-Induced Strand Breaks in Telomere-Derived DNA Sequences-Influence of DNA Sequence and Topology.

PubMed

Rackwitz, Jenny; Bald, Ilko

2018-03-26

During cancer radiation therapy high-energy radiation is used to reduce tumour tissue. The irradiation produces a shower of secondary low-energy (<20 eV) electrons, which are able to damage DNA very efficiently by dissociative electron attachment. Recently, it was suggested that low-energy electron-induced DNA strand breaks strongly depend on the specific DNA sequence with a high sensitivity of G-rich sequences. Here, we use DNA origami platforms to expose G-rich telomere sequences to low-energy (8.8 eV) electrons to determine absolute cross sections for strand breakage and to study the influence of sequence modifications and topology of telomeric DNA on the strand breakage. We find that the telomeric DNA 5'-(TTA GGG) 2 is more sensitive to low-energy electrons than an intermixed sequence 5'-(TGT GTG A) 2 confirming the unique electronic properties resulting from G-stacking. With increasing length of the oligonucleotide (i.e., going from 5'-(GGG ATT) 2 to 5'-(GGG ATT) 4 ), both the variety of topology and the electron-induced strand break cross sections increase. Addition of K + ions decreases the strand break cross section for all sequences that are able to fold G-quadruplexes or G-intermediates, whereas the strand break cross section for the intermixed sequence remains unchanged. These results indicate that telomeric DNA is rather sensitive towards low-energy electron-induced strand breakage suggesting significant telomere shortening that can also occur during cancer radiation therapy. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physical models, cross sections, and numerical approximations used in MCNP and GEANT4 Monte Carlo codes for photon and electron absorbed fraction calculation.

PubMed

Yoriyaz, Hélio; Moralles, Maurício; Siqueira, Paulo de Tarso Dalledone; Guimarães, Carla da Costa; Cintra, Felipe Belonsi; dos Santos, Adimir

2009-11-01

Radiopharmaceutical applications in nuclear medicine require a detailed dosimetry estimate of the radiation energy delivered to the human tissues. Over the past years, several publications addressed the problem of internal dose estimate in volumes of several sizes considering photon and electron sources. Most of them used Monte Carlo radiation transport codes. Despite the widespread use of these codes due to the variety of resources and potentials they offered to carry out dose calculations, several aspects like physical models, cross sections, and numerical approximations used in the simulations still remain an object of study. Accurate dose estimate depends on the correct selection of a set of simulation options that should be carefully chosen. This article presents an analysis of several simulation options provided by two of the most used codes worldwide: MCNP and GEANT4. For this purpose, comparisons of absorbed fraction estimates obtained with different physical models, cross sections, and numerical approximations are presented for spheres of several sizes and composed as five different biological tissues. Considerable discrepancies have been found in some cases not only between the different codes but also between different cross sections and algorithms in the same code. Maximum differences found between the two codes are 5.0% and 10%, respectively, for photons and electrons. Even for simple problems as spheres and uniform radiation sources, the set of parameters chosen by any Monte Carlo code significantly affects the final results of a simulation, demonstrating the importance of the correct choice of parameters in the simulation.

Broadband Measurement of Aerosol Extinction in the Visible Range

NASA Astrophysics Data System (ADS)

He, Quanfu; Bluvshtein, Nir; Segev, Lior; Flores, Michel; Rudich, Yinon; Washenfelder, Rebecca; Brown, Steven

2017-04-01

Atmospheric aerosols influence the Earth's radiative budget directly by scattering and absorbing incoming solar radiation. Aerosol direct forcing remains one of the largest uncertainties in quantifying the role that aerosols play in the Earth's radiative budget. The optical properties of aerosols vary as a function of wavelength, but few measurements reported the wavelength dependence of aerosol extinction cross section and complex refractive indices, particularly in the blue and visible spectral range. There is also currently a large gap in our knowledge of how the optical properties evolve as a function of atmospheric aging in the visible spectrum. In this study, we constructed a new and novel laboratory instrument to measure aerosol extinction as a function of wavelength, using cavity enhanced spectroscopy with a white light source. This broadband cavity enhanced spectroscopy (BBCES) covers the 395-700 nm spectral region using a broadband light source and a grating spectrometer with charge-coupled device detector (CCD). We evaluated this BBCES by measuring extinction cross section for aerosols that are pure scattering, slightly absorbing and strongly absorbing atomized from standard materials. We also retrieved the refractive indices from the measured extinction cross sections. Secondary organic aerosols from biogenic and anthropogenic precursors were "aged" to differential time scales (1 to 10 days) in an Oxidation Flow Reactor (OFR) under the combined influence of OH, O3 and UV light. The new BBCES was used to online measure the extinction cross sections of the SOA. This talk will provide a comprehensive understanding of aerosol optical properties alerting during aging process in the 395 - 700 nm spectrum.

Longitudinal evidence for anterograde trans-synaptic degeneration after optic neuritis

PubMed Central

Goodkin, Olivia; Altmann, Daniel R.; Jenkins, Thomas M.; Miszkiel, Katherine; Mirigliani, Alessia; Fini, Camilla; Gandini Wheeler-Kingshott, Claudia A. M.; Thompson, Alan J.; Ciccarelli, Olga; Toosy, Ahmed T.

2016-01-01

Abstract In multiple sclerosis, microstructural damage of normal-appearing brain tissue is an important feature of its pathology. Understanding these mechanisms is vital to help develop neuroprotective strategies. The visual pathway is a key model to study mechanisms of damage and recovery in demyelination. Anterograde trans-synaptic degeneration across the lateral geniculate nuclei has been suggested as a mechanism of tissue damage to explain optic radiation abnormalities seen in association with demyelinating disease and optic neuritis, although evidence for this has relied solely on cross-sectional studies. We therefore aimed to assess: (i) longitudinal changes in the diffusion properties of optic radiations after optic neuritis suggesting trans-synaptic degeneration; (ii) the predictive value of early optic nerve magnetic resonance imaging measures for late optic radiations changes; and (iii) the impact on visual outcome of both optic nerve and brain post-optic neuritis changes. Twenty-eight consecutive patients with acute optic neuritis and eight healthy controls were assessed visually (logMAR, colour vision, and Sloan 1.25%, 5%, 25%) and by magnetic resonance imaging, at baseline, 3, 6, and 12 months. Magnetic resonance imaging sequences performed (and metrics obtained) were: (i) optic nerve fluid-attenuated inversion-recovery (optic nerve cross-sectional area); (ii) optic nerve proton density fast spin-echo (optic nerve proton density-lesion length); (iii) optic nerve post-gadolinium T 1 -weighted (Gd-enhanced lesion length); and (iv) brain diffusion-weighted imaging (to derive optic radiation fractional anisotropy, radial diffusivity, and axial diffusivity). Mixed-effects and multivariate regression models were performed, adjusting for age, gender, and optic radiation lesion load. These identified changes over time and associations between early optic nerve measures and 1-year global optic radiation/clinical measures. The fractional anisotropy in patients’ optic radiations decreased ( P = 0.018) and radial diffusivity increased ( P = 0.002) over 1 year following optic neuritis, whereas optic radiation measures were unchanged in controls. Also, smaller cross-sectional areas of affected optic nerves at 3 months post-optic neuritis predicted lower fractional anisotropy and higher radial diffusivity at 1 year ( P = 0.007) in the optic radiations, whereas none of the inflammatory measures of the optic nerve predicted changes in optic radiations. Finally, greater Gd-enhanced lesion length at baseline and greater optic nerve proton density-lesion length at 1 year were associated with worse visual function at 1 year ( P = 0.034 for both). Neither the cross-sectional area of the affected optic nerve after optic neuritis nor the damage in optic radiations was associated with 1-year visual outcome. Our longitudinal study shows that, after optic neuritis, there is progressive damage to the optic radiations, greater in patients with early residual optic nerve atrophy, even after adjusting for optic radiation lesions. These findings provide evidence for trans-synaptic degeneration. PMID:26912640

Measurement of Neutron Reaction Cross Sections between 8 and 14 MeV

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

Mannhart, Wolf; Schmidt, Dankwart

2005-05-24

Cross-section measurements were performed with special emphasis on access to the 'blind spot' in the neutron energy range from 10 to 13 MeV. The use of a conventional D(d,n) neutron source in combination with TOF measurements of the D(d,np) break-up component allows the precise determination of monoenergetic cross-section data in this range. The procedure is demonstrated with the measurement of the cross sections of 64Zn(n,p)64Cu, 64Zn(n,2n)63Zn, 63Cu(n,2n)62Cu, and 65Cu(n,2n)64Cu. With all reaction products being strong positron emitters, the radioactivity-counting process has been optimised for a perfect registration of the associated annihilation radiation.

Measurement of Neutron Reaction Cross Sections between 8 and 14 MeV

NASA Astrophysics Data System (ADS)

Mannhart, Wolf; Schmidt, Dankwart

2005-05-01

Cross-section measurements were performed with special emphasis on access to the "blind spot" in the neutron energy range from 10 to 13 MeV. The use of a conventional D(d,n) neutron source in combination with TOF measurements of the D(d,np) break-up component allows the precise determination of monoenergetic cross-section data in this range. The procedure is demonstrated with the measurement of the cross sections of 64Zn(n,p)64Cu, 64Zn(n,2n)63Zn, 63Cu(n,2n)62Cu, and 65Cu(n,2n)64Cu. With all reaction products being strong positron emitters, the radioactivity-counting process has been optimised for a perfect registration of the associated annihilation radiation.

A program to measure new energetic particle nuclear interaction cross sections

NASA Astrophysics Data System (ADS)

Guzik, T. G.; Albergo, S.; Chen, C.-X.; Costa, S.; Crawford, H. J.; Engelage, J.; Ferrando, P.; Flores, I.; Greiner, L.; Jones, F. C.; Knott, C. N.; Ko, S.; Lindstrom, P. J.; Mazotta, J.; Mitchell, J. W.; Romanski, J.; Potenza, R.; Soutoul, A.; Testard, O.; Tull, C. E.; Tuve, C.; Waddington, C. J.; Webber, W. R.; Wefel, J. P.; Zhang, X.

1994-10-01

The Transport Collaboration, consisting of researchers from institutions in France, Germany, Italy, and the USA, has established a program to make new measurements of nuclear interaction cross sections for heavy projectiles (Z greater than or equal to 2) in targets of liquid H2, He and heavier materials. Such cross sections directly affect calculations of galactic and solar cosmic ray transport through matter and are needed for accurate radiation hazard assessment. To date, the collaboration has obtained data using the Lawrence Berkeley Laboratory Bevalac HISS facility with 20 projectiles from He-4 to Ni-58 in the energy range 393-910 MeV/nucleon. Preliminary results from the analysis of these data are presented here and compared to other measurements and to cross section prediction formulae.

A program to measure new energetic particle nuclear interaction cross sections

NASA Technical Reports Server (NTRS)

Guzik, T. G.; Albergo, S.; Chen, C. X.; Costa, S.; Crawford, H. J.; Engelage, J.; Ferrando, P.; Flores, I.; Greiner, L.; Jones, F. C.

1994-01-01

The Transport Collaboration, consisting of researchers from institutions in France, Germany, Italy, and the USA, has established a program to make new measurements of nuclear interaction cross sections for heavy projectiles (Z greater than or equal to 2) in targets of liquid H2, He and heavier materials. Such cross sections directly affect calculations of galactic and solar cosmic ray transport through matter and are needed for accurate radiation hazard assessment. To date, the collaboration has obtained data using the Lawrence Berkeley Laboratory Bevalac HISS facility with 20 projectiles from He-4 to Ni-58 in the energy range 393-910 MeV/nucleon. Preliminary results from the analysis of these data are presented here and compared to other measurements and to cross section prediction formulae.

Photoionization Efficiencies of Five Polycyclic Aromatic Hydrocarbons.

PubMed

Johansson, K Olof; Campbell, Matthew F; Elvati, Paolo; Schrader, Paul E; Zádor, Judit; Richards-Henderson, Nicole K; Wilson, Kevin R; Violi, Angela; Michelsen, Hope A

2017-06-15

We have measured photoionization-efficiency curves for pyrene, fluoranthene, chrysene, perylene, and coronene in the photon energy range of 7.5-10.2 eV and derived their photoionization cross-section curves in this energy range. All measurements were performed using tunable vacuum ultraviolet (VUV) radiation generated at the Advanced Light Source synchrotron at Lawrence Berkeley National Laboratory. The VUV radiation was used for photoionization, and detection was performed using a time-of-flight mass spectrometer. We measured the photoionization efficiency of 2,5-dimethylfuran simultaneously with those of pyrene, fluoranthene, chrysene, perylene, and coronene to obtain references of the photon flux during each measurement from the known photoionization cross-section curve of 2,5-dimethylfuran.

Influence of electron correlation on the cross section and linear polarization of radiation emitted by electron-impact excitation of Ca+ and Ba+ ions

NASA Astrophysics Data System (ADS)

Chen, Zhan-Bin

2018-04-01

Calculations of the electron-impact excitation (EIE) of singly charged Ca+ and Ba+ ions and subsequent de-excitation process are performed using a fully relativistic distorted wave (RDW) method. To resolve the discrepancy between previous theory and experiment, careful consideration is given to the generation of the target state wave-functions through the systematic inclusion of electron correlations. It is found that the electron correlation effects play a significant role on the cross section, while the effects on the linear polarization of the emitted radiation are relatively small. Good agreement between our result and experiment is obtained.

Search for P-ODD asymmetry in the radiative cross-section of the interaction of neutrons with lead nuclei

NASA Astrophysics Data System (ADS)

Gledenov, Yu. M.; Nesvizhevsky, V. V.; Sedyshev, P. V.; Shul'gina, E. V.; Vesna, V. A.

2014-03-01

The P-odd effect in the radiation cross section of capture of longitudinally polarized neutrons in a sample of natural lead is measured. The experiment was performed at PF1B facility at the Institut Max von Laue-Paul Langevin. The neutron polarization P n was 92%, the total flux of polarized neutrons was ˜3 × 1010 n/s, and the mean neutron wavelength was λ = 4.7 Å. Taking into account "0-test" we estimated the asymmetry: a γ(natPb) = (2.3 ± 3.5) × 10-7, i.e., α γ ≤ 8.1 × 10-7 at 90% confidence level.

Hadron Cancer Therapy: Role of Nuclear Reactions

DOE R&D Accomplishments Database

Chadwick, M. B.

2000-06-20

Recently it has become feasible to calculate energy deposition and particle transport in the body by proton and neutron radiotherapy beams, using Monte Carlo transport methods. A number of advances have made this possible, including dramatic increases in computer speeds, a better understanding of the microscopic nuclear reaction cross sections, and the development of methods to model the characteristics of the radiation emerging from the accelerator treatment unit. This paper describes the nuclear reaction mechanisms involved, and how the cross sections have been evaluated from theory and experiment, for use in computer simulations of radiation therapy. The simulations will allow the dose delivered to a tumor to be optimized, whilst minimizing the dos given to nearby organs at risk.

On the gas-phase formation of the HCO radical: accurate quantum study of the H+CO radiative association

NASA Astrophysics Data System (ADS)

Stoecklin, Thierry; Halvick, Philippe; Yu, Hua-Gen; Nyman, Gunnar; Ellinger, Yves

2018-04-01

We present the first quantum study of the radiative association of H and CO to form the HCO molecule within a time-independent approach. We use a recently published 3D potential energy surface of spectroscopic accuracy and two 3D dipole moment surfaces, which were calculated for this study. We discuss the variation of the radiative association cross-section as a function of both the rotational angular momentum of CO and the total angular momentum and use the uniform J-shifting approach to obtain the global radiative association rate coefficient. The effect of the saddle point separating the HCO molecule from the H+CO reactants and the main features of the radiative association cross-sections are analysed and discussed. The calculated rate coefficient is below 10-23 cm3 molecule-1 s-1 for temperatures lower than 30 K, and increases up to 5 × 10-20 cm3 molecule-1 s-1 at T = 300 K. These results demonstrate that the gas-phase H+CO radiative association cannot be the process at the origin of the sequence leading to the formation of methanol in a cold interstellar medium.

Fragmentation Cross Sections of 290 and 400 MeV/nucleon 12C Beamson Elemental Targets

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

Zeitlin, C.; Guetersloh, S.; Heilbronn, L.

Charge-changing and fragment production cross sections at 0circ have been obtained for interactions of 290 MeV/nucleon and 400MeV/nucleon carbon beams with C, CH2, Al, Cu, Sn, and Pb targets. Thesebeams are relevant to cancer therapy, space radiation, and the productionof radioactive beams. We compare to previously published results using Cand CH2 targets at similar beam energies. Due to ambiguities arising fromthe presence of multiple fragments on many events, previous publicationshave reported only cross sections for B and Be fragments. In this work wehave extracted cross sections for all fragment species, using dataobtained at three distinct values of angular acceptance, supplementedmore » bydata taken with the detector stack placed off the beam axis. A simulationof the experiment with the PHITS Monte Carlo code shows fair agreementwith the data obtained with the large acceptance detectors, but agreementis poor at small acceptance. The measured cross sections are alsocompared to the predictions of the one-dimensional cross section modelsEPAX2 and NUCFRG2; the latter is presently used in NASA's space radiationtransport calculations. Though PHITS and NUCFRG2 reproduce thecharge-changing cross sections with reasonable accuracy, none of themodels is able to accurately predict the fragment cross sections for allfragment species and target materials.« less

Pressure Dependence of Excitation Cross Sections for Resonant Levels of Rare Gases

NASA Astrophysics Data System (ADS)

Stewart, Michael D.; Chilton, J. Ethan; Lin, Chun C.

2000-06-01

In the rare gases, the excited n'p^5ns and n'p^5nd levels with J = 1 are optically coupled to ground as well as lower lying p levels. Resonant photons emitted when the atom decays to ground can be reabsorbed by another ground-state atom. At low gas pressures this reabsorption occurs infrequently, but at higher pressures becomes increasingly likely until the resonant transition is completely suppressed. This enhances the cascade transitions into lower p levels, resulting in pressure dependent optical emission cross sections. This reabsorption process can be understood quantitatively with a model developed by Heddle et al(D. W. O. Heddle and N. J. Samuel, J. Phys. B 3), 1593 (1970).. The radiation from transitions into the nonresonant levels often lie in the ir, while the resonant radiation is always in the uv spectral region. Using a Fourier-transform spectrometer, one can measure the cross sections for the ir transitions as a function of pressure. The Heddle model can be fit to these data with the use of theoretical values for the Einstein A coefficients. This provides a test of the accuracy of calculated A values. Discussion will include cross section measurements for Ne, Ar, and Kr excited by electron impact over a range of gas pressures.

Charge-equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

NASA Technical Reports Server (NTRS)

Rule, D. W.; Omidvar, K.

1977-01-01

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, is considered. Electron loss of the beam has been taken into account by means of the First Born approximation allowing for the target atom to remain unexcited, or to be excited to all possible states. Electron capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation and collisional inner-shell ionization of the ions has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated.

Circular polarization of X-ray radiation emitted by longitudinally polarized electron impact excitation: Under a screened Coulomb interaction

NASA Astrophysics Data System (ADS)

Chen, Zhan-Bin

2017-12-01

Longitudinally polarized electron impact excitation from the ground state 1s2 to the excited state 1s2l (l =s,p) levels of highly charged He-like Fe24+ ions in weakly coupled hot-dense plasmas is investigated using a fully relativistic distorted-wave method. The Debye-Hückel potential is used to describe the plasma screening. Benchmark results such as the total cross sections, the magnetic sublevels cross sections, and the circular polarizations of corresponding X-ray radiations are presented. For the excitation process, results show that the plasma screening has an effect in reducing both the total and magnetic sublevels cross sections. For the de-excitation process, it is found that while the plasma screening as a slightly effect on the circular polarizations of radiations for the 1 s 2 s 3S1 → 1 s21S0,1 s 2 p 3P2 → 1 s21S0 , and 1 s 2 p 1P1 → 1 s21S0 transition lines, it gives a substantial contribution for the same properties of the 1 s 2 p 3P1 → 1 s21S0 line.

EDDIX--a database of ionisation double differential cross sections.

PubMed

MacGibbon, J H; Emerson, S; Liamsuwan, T; Nikjoo, H

2011-02-01

The use of Monte Carlo track structure is a choice method in biophysical modelling and calculations. To precisely model 3D and 4D tracks, the cross section for the ionisation by an incoming ion, double differential in the outgoing electron energy and angle, is required. However, the double differential cross section cannot be theoretically modelled over the full range of parameters. To address this issue, a database of all available experimental data has been constructed. Currently, the database of Experimental Double Differential Ionisation Cross sections (EDDIX) contains over 1200 digitalised experimentally measured datasets from the 1960s to present date, covering all available ion species (hydrogen to uranium) and all available target species. Double differential cross sections are also presented with the aid of an eight parameter functions fitted to the cross sections. The parameters include projectile species and charge, target nuclear charge and atomic mass, projectile atomic mass and energy, electron energy and deflection angle. It is planned to freely distribute EDDIX and make it available to the radiation research community for use in the analytical and numerical modelling of track structure.

Investigating the sensitivity of nitric oxide infrared emissions to electron impact

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.; Allan, M.

2008-05-01

Integral cross sections for low energy electron excitation of the 0→1, 0→2 and 0→3 vibrational modes in nitric oxide have quite recently become available [Trevisan et al. PRA 71, 052714 (2005)]. In this study we adapt our recent work [Campbell and Brunger GRL, in press (2007)], to look at the effect of these new cross sections on the production of nitric oxide infrared radiation. Predictions from our model are compared with measurements from Espy et al. [Planet. Space Sci. 36, 543 (1988)], with the inclusion of the new cross sections improving the agreement of the shape of the spectrum with the measurements.

Knowledge deficiency of work-related radiation hazards associated with psychological distress among orthopedic surgeons

PubMed Central

Fan, Guoxin; Wang, Yueye; Guo, Changfeng; Lei, Xuefeng; He, Shisheng

2017-01-01

Abstract Knowledge and concern degree about work-related radiation hazards remained unknown among orthopedic surgeons. The aim of the cross-sectional study is to investigate whether the knowledge degree of work-related radiation is associated with psychological distress among orthopedic surgeons. This cross-sectional study sent electronic questionnaire via WeChat to orthopedic surgeons nationwide. Concern and knowing degree over radiation exposure was evaluated by a single self-reported question. Professional evaluation of concern degree was reflected by general psychological distress, which was assessed with the Kessler 10 scale (K10) and depressive symptoms with the Center for Epidemiologic Studies Depression Scale (CES-D). Only 43.23% (115/266) respondents knew well about radiation and a total of 78.20% (208/266) respondents considered radiation exposure as a great concern. Among those who reported concerns about radiation exposure, a total of 57.69% (120/208) respondents reported knowing little about radiation. Respondents who reported concerns over radiation exposure were significantly associated with higher scores on CES-D and K10 (P < .05). Among respondents who reported concerns over radiation exposure, those who have fewer knowledge about radiation, had higher CES-D and K10 scores than those who knew well about radiation (P < .05). Among respondents who reported no concerns over radiation exposure, those who knew little about radiation still had higher CES-D and K10 scores (P < .05). Fewer radiation knowledge tends to induce more radiation concerns associated with higher psychological distress in orthopedic surgeons. Radiation knowledge should be enhanced for surgeons who daily work with radiation-related fluoroscopy. PMID:28538368

High-resolution absorption cross section measurements of supersonic jet-cooled carbon monoxide between 92.5 and 97.4 nanometers

NASA Technical Reports Server (NTRS)

Yoshino, K.; Stark, G.; Esmond, J. R.; Smith, P. L.; Ito, K.; Matsui, T.

1995-01-01

High-resolution photoabsorption cross sections for eight CO bands, at wavelengths between 92.5 nm and 97.4 nm, have been measured in a supersonic jet-cooled source (approximately equals 20 K) at the Photon Factory synchrotron radiation facility. New integrated cross sections are reported for four bands between 92.5 nm and 94.2 nm. A low-temperature spectrum of the W(1)-X(0) band (95.6 nm), which was used to determine the absorbing CO column densities, is also presented. Additional jet-cooled cross section measurements were made on the L(0)-X(0), K(0)-X(0), and W(0)-X(0) bands (96.7-97.4 nm) which verify previously published results. A self-consistent set of band oscillator strengths is presented for the eight bands studied.

Computer program for thin-wire structures in a homogeneous conducting medium

NASA Technical Reports Server (NTRS)

Richmond, J. H.

1974-01-01

A computer program is presented for thin-wire antennas and scatters in a homogeneous conducting medium. The anaylsis is performed in the real or complex frequency domain. The program handles insulated and bare wires with finite conductivity and lumped loads. The output data includes the current distribution, impedance, radiation efficiency, gain, absorption cross section, scattering cross section, echo area and the polarization scattering matrix. The program uses sinusoidal bases and Galerkin's method.

On the use of the cross section concept as applied to pulsed CO2 laser dynamics

NASA Technical Reports Server (NTRS)

Flamant, P. H.; Menzies, R. T.

1985-01-01

The 'cross sections' which are commonly used in combination with the molecular vibrational level densities to describe induced transition rates are time dependent in a pulsed discharge. This greatly affects the relative rates of buildup of radiation at the various lines of a molecular gain medium in a nondispersive cavity, and the consequences for line selection by injection in a TEA-CO2 laser are discussed.

[Excitation transfer between high-lying states in K2 in collisions with ground state K and H2 molecules].

PubMed

Shen, Xiao-Yan; Liu, Jing; Dai, Kang; Shen, Yi-Fan

2010-02-01

Pure potassium vapor or K-H2 mixture was irradiated in a glass fluorescence cell with pulses of 710 nm radiation from an OPO laser, populating K2 (1lambda(g)) state by two-photon absorption. Cross sections for 1lambda(g)-3lambda(g) transfer in K2 were determined using methods of molecular fluorescence. During the experiments with pure K vapor, the cell temperature was varied between 553 and 603 K. The K number density was determined spectroscopically by the white-light absorption measurement in the blue wing of the self-broadened resonance D2 line. The resulting fluorescence included a direct component emitted in the decay of the optically excitation and a sensitized component arising from the collisionally populated state. The decay signal of time-resolved fluorescence from1lambda(g) -->1 1sigma(u)+ transition was monitored. It was seen that just after the laser pulse the fluorescence of the photoexcited level decreased exponentially. The effective lifetimes of the 1lambda(g) state can be resolved. The plot of reciprocal of effective lifetimes of the 1lambda(g) state against K densities yielded the slope that indicated the total cross section for deactivation and the intercept that provided the radiative lifetime of the state. The radiative lifetime (20 +/- 2) ns was obtained. The cross section for deactivation of the K2(1lambda(g)) molecules by collisions with K is (2.5 +/- 0.3) x 10(-14) cm2. The time-resolved intensities of the K23lambda(g) --> 1 3sigma(u)+ (484 nm) line were measured. The radiative lifetime (16.0 +/- 3.2) ns and the total cross section (2.5 +/- 0.6) x 10(-14) cm2 for deactivation of the K2 (3lambda(g)) state can also be determined through the analogous procedure. The time-integrated intensities of 1lambda(g) --> 1 1sigma(u)+ and 3lambda(g) --> 1 3sigma(u)+ transitions were measured. The cross section (1.1 +/- 0.3) x10(-14) cm2 was obtained for K2 (1lambda(g))+ K --> K2 (3lambda(g)) + K collisions. During the experiments with K-H2 mixture, the cell temperature was kept constant at 553 K. The H2 pressure was varied between 40 and 400 Pa. The effects of K2-K collisions could not be neglected. These effects were subtracted out using the results of the pure K experiments. The cross section (2.7 +/- 1.1) x 10(-15) cm2 was obtained for K2 (1lambda(g)) + H2 --> K2 (3lambda(g))+H2 collisions. The cross section is (6.8 +/- 2.7) x 10(-15) cm2 for K2 (3lambda(g)) + H2 --> states out of K2 (3lambda(g)) + H2 collisions.

Photon interaction study of organic nonlinear optical materials in the energy range 122-1330 keV

NASA Astrophysics Data System (ADS)

Awasarmol, Vishal V.; Gaikwad, Dhammajyot K.; Raut, Siddheshwar D.; Pawar, Pravina P.

2017-01-01

In the present study, the mass attenuation coefficient (μm) of six organic nonlinear optical materials has been calculated in the energy range 122-1330 keV and compared with the obtained values from the WinXCOM program. It is found that there is a good agreement between theoretical and experimental values (<3%). The linear attenuation coefficients (μ) total atomic cross section (σt, a), and total electronic cross section (σt, el) have also been calculated from the obtained μm values and their variations with photon energy have been plotted. From the present work, it is observed that the variation of obtained values of μm, μ, σt, a, and σt, el strongly depends on the photon energy and decreases or increases due to chemical composition and density of the sample. All the samples have been studied extensively using transmission method with a view to utilize the material for radiation dosimetry. Investigated samples are good material for radiation dosimetry due their low effective atomic number. The mass attenuation coefficient (μm), linear attenuation coefficients (μ), total atomic cross section (σt, a), total electronic cross section (σt, el), effective atomic numbers (Zeff), molar extinction coefficient (ε), mass energy absorption coefficient (μen/ρ) and effective atomic energy absorption cross section (σa, en) of all sample materials have been carried out and transmission curves have been plotted. The transmission curve shows that the variation of all sample materials decreases with increasing photon energy.

Track structure simulations at relativistic energies: an update on cross section calculations

NASA Astrophysics Data System (ADS)

Dingfelder, Michael

Charged particle track structure simulations follow the primary, as well as all (produced) sec-ondary particles in an event-by-event matter, from starting or ejection energies down to total stopping. They provide detailed information on the spacial distributions of energy depositions, interaction types, and radical species produced. These quantities provide a starting point to describe the interaction of the radiation with matter of biological interest and to explore and estimate the effects of radiation quality on various biological responses of these systems. Of special interest is liquid water which serves as surrogate for soft tissue. Ionization and excitation cross sections for bare charged particles can be calculated within the framework of the (relativistic) plane-wave Born approximation or the (relativistic) Bethe approximation. Both theories rely on a realistic model of the dielectric response function of the material under consideration and need to address relativistic medium polarization effects like the Fermi-density effect in a consistent way. In this talk we will review and present new and updated aspects of charged particle cross section calculations for relativistic heavy ions with liquid water and other materials of biological interest. This includes an updated model for the dielectric response function of liquid water to better reflect new data from inelastic X-ray scattering (IXS) experiments using synchrotron radiation and a model for the dielectric response function of calcium, which serves as a bone surrogate. We will also discuss the implementation of relativistic effect, especially of the Fermi-density effect into the cross section calculations. This work is supported by the National Aeronautics and Space Administration (NASA), grant no. NNJ04HF39G.

Active electromagnetic invisibility cloaking and radiation force cancellation

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2018-03-01

This investigation shows that an active emitting electromagnetic (EM) Dirichlet source (i.e., with axial polarization of the electric field) in a homogeneous non-dissipative/non-absorptive medium placed near a perfectly conducting boundary can render total invisibility (i.e. zero extinction cross-section or efficiency) in addition to a radiation force cancellation on its surface. Based upon the Poynting theorem, the mathematical expression for the extinction, radiation and amplification cross-sections (or efficiencies) are derived using the partial-wave series expansion method in cylindrical coordinates. Moreover, the analysis is extended to compute the self-induced EM radiation force on the active source, resulting from the waves reflected by the boundary. The numerical results predict the generation of a zero extinction efficiency, achieving total invisibility, in addition to a radiation force cancellation which depend on the source size, the distance from the boundary and the associated EM mode order of the active source. Furthermore, an attractive EM pushing force on the active source directed toward the boundary or a repulsive pulling one pointing away from it can arise accordingly. The numerical predictions and computational results find potential applications in the design and development of EM cloaking devices, invisibility and stealth technologies.

Measurements of elastic and inelastic scattering cross-sections using monoenergetic Kα radiation

NASA Astrophysics Data System (ADS)

Rao, Donepudi V.; Seltzer, S. M.; Hubbell, John H.; Cesareo, Roberto; Brunetti, Antonio; Gigante, Giovanni E.

2000-12-01

Elastic and inelastic scattering cross-sections for low, medium and high Z atoms are measured in vacuum using an x- ray tube with a secondary targets as an excitation source. Monoenergetic K(alpha) radiation emitted from the secondary target is used to excite the sample. Monoenergetic radiation emitted from the secondary target is used to excite the sample. Monoenergetic radiation is also produced using two secondary targets coupled to an x-ray tube and the radiation from the second target of the system is used to excite the sample. Elastic and inelastic scattering of K(alpha) X-ray line energies of the secondary target by the sample are recorded with Hp Ge and Si(Li) detectors. Using this system the degree of monochromaticity of the secondary emission and the geometrical effects of the measuring system is estimated. The efficiency is large because the secondary target acts as a converter. Experimental results based on this system will be presented and compared with theoretical estimates. The importance of the dat and the potential use of the system for few applications in the field of medicine and archaeometry will also be presented.

Nonprincipal plane scattering of flat plates and pattern control of horn antennas

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Polka, Lesley A.; Liu, Kefeng

1989-01-01

Using the geometrical theory of diffraction, the traditional method of high frequency scattering analysis, the prediction of the radar cross section of a perfectly conducting, flat, rectangular plate is limited to principal planes. Part A of this report predicts the radar cross section in nonprincipal planes using the method of equivalent currents. This technique is based on an asymptotic end-point reduction of the surface radiation integrals for an infinite wedge and enables nonprincipal plane prediction. The predicted radar cross sections for both horizontal and vertical polarizations are compared to moment method results and experimental data from Arizona State University's anechoic chamber. In part B, a variational calculus approach to the pattern control of the horn antenna is outlined. The approach starts with the optimization of the aperture field distribution so that the control of the radiation pattern in a range of directions can be realized. A control functional is thus formulated. Next, a spectral analysis method is introduced to solve for the eigenfunctions from the extremal condition of the formulated functional. Solutions to the optimized aperture field distribution are then obtained.

Photoneutron cross sections for 59Co : Systematic uncertainties of data from various experiments

NASA Astrophysics Data System (ADS)

Varlamov, V. V.; Davydov, A. I.; Ishkhanov, B. S.

2017-09-01

Data on partial photoneutron reaction cross sections (γ ,1n), (γ ,2n), and (γ ,3n) for 59Co obtained in two experiments carried out at Livermore (USA) were analyzed. The sources of radiation in both experiments were the monoenergetic photon beams from the annihilation in flight of relativistic positrons. The total yield was sorted by the neutron multiplicity, taking into account the difference in the neutron energy spectra for different multiplicity. The two quoted studies differ in the method of determining the neutron. Significant systematic disagreements between the results of the two experiments exist. They are considered to be caused by large systematic uncertainties in partial cross sections, since they do not satisfy physical criteria for reliability of the data. To obtain reliable cross sections of partial and total photoneutron reactions a new method combining experimental data and theoretical evaluation was used. It is based on the experimental neutron yield cross section which is rather independent of neutron multiplicity and the transitional neutron multiplicity functions of the combined photonucleon reaction model (CPNRM). The model transitional multiplicity functions were used for the decomposition of the neutron yield cross section into the contributions of partial reactions. The results of the new evaluation noticeably differ from the partial cross sections obtained in the two experimental studies are under discussion.

Rayleigh scattering cross-section measurements of nitrogen, argon, oxygen and air

NASA Astrophysics Data System (ADS)

Thalman, Ryan; Zarzana, Kyle J.; Tolbert, Margaret A.; Volkamer, Rainer

2014-11-01

Knowledge about Rayleigh scattering cross sections is relevant to predictions about radiative transfer in the atmosphere, and needed to calibrate the reflectivity of mirrors that are used in high-finesse optical cavities to measure atmospheric trace gases and aerosols. In this work we have measured the absolute Rayleigh scattering cross-section of nitrogen at 405.8 and 532.2 nm using cavity ring-down spectroscopy (CRDS). Further, multi-spectral measurements of the scattering cross-sections of argon, oxygen and air are presented relative to that of nitrogen from 350 to 660 nm using Broadband Cavity Enhanced Spectroscopy (BBCES). The reported measurements agree with refractive index based theory within 0.2±0.4%, and have an absolute accuracy of better than 1.3%. Our measurements expand the spectral range over which Rayleigh scattering cross section measurements of argon, oxygen and air are available at near-ultraviolet wavelengths. The expressions used to represent the Rayleigh scattering cross-section in the literature are evaluated to assess how uncertainties affect quantities measured by cavity enhanced absorption spectroscopic (CEAS) techniques. We conclude that Rayleigh scattering cross sections calculated from theory provide accurate data within very low error bounds, and are suited well to calibrate CEAS measurements of atmospheric trace gases and aerosols.

Tropical and Subtropical Cloud Transitions in Weather and Climate Prediction Models: The GCSS/WGNE Pacific Cross-Section Intercomparison (GPCI)

NASA Technical Reports Server (NTRS)

Teixeira, J.; Cardoso, S.; Bonazzola, M.; Cole, J.; DeGenio, A.; DeMott, C.; Franklin, C.; Hannay, C.; Jakob, C.; Jiao, Y.;

Measurements of Radiative Capture Cross Sections at Big Bang Energies

NASA Astrophysics Data System (ADS)

Tanaka, Masaomi; Fukuda, Mitsunori; Tanaka, Yutaro; Du, Hang; Ohnishi, Kousuke; Yagi, Shoichi; Sugihara, Takanobu; Hori, Taichi; Nakamura, Shoken; Yanagihara, Rikuto; Matsuta, Kensaku; Mihara, Mototsugu; Nishimura, Daiki; Iwakiri, Shuichi; Kambayashi, Shohei; Kunimatsu, Shota; Sakakibara, Hikaru; Yamaoka, Shintaro

We measured d(p, γ )3He cross sections at ECM = 0.12, 0.19, 0.44, and 0.57 MeV. In this energy region, available experimental values are systematically smaller than the recent calculation, so that additional experiments are desired for understanding the Big Bang Nucleosynthesis. The experiment was performed by bombarding proton beams to the D2 gas target with the 5 MV Van de Graaff accelerator at Osaka University. The experimental d(p, γ )3He cross sections of the present study are systematically larger than previous data. On the other hand, recent theoretical results by Marcucci et al. are in good agreement with present experimental results.

Absolute photoionization cross sections of two cyclic ketones: cyclopentanone and cyclohexanone.

PubMed

Price, Chelsea; Fathi, Yasmin; Meloni, Giovanni

2017-05-01

Absolute photoionization cross sections for cyclopentanone and cyclohexanone, as well as partial ionization cross sections for the dissociative ionized fragments, are presented in this investigation. Experiments are performed via a multiplexed photoionization mass spectrometer utilizing vacuum ultraviolet (VUV) synchrotron radiation supplied by the Advanced Light Source of Lawrence Berkeley National Laboratory. These results allow the quantification of these species that is relevant to investigate the kinetics and combustion reactions of potential biofuels. The CBS-QB3 calculated values for the adiabatic ionization energies agree well with the experimental values, and the identification of possible dissociative fragments is discussed for both systems. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Dissociative and double photoionization of CO2 from threshold to 90 A

NASA Technical Reports Server (NTRS)

Masuoka, T.; Samson, J. A. R.

1979-01-01

The molecular photoionization, dissociative photoionization and double photoionization cross sections for CO2 were measured from their onsets down to 90 A by using various combinations of mass spectrometers (a coincidence time-of-flight mass spectrometer and a magnetic mass spectrometer) and light sources (synchrotron radiation, and glow and spark discharge). It is concluded that the one broad peak and the three shoulders in the total adsorption cross section curve between 640 and 90 A are caused completely by dissociative ionization processes. Several peaks observed in the cross section curve for the total fragmentation CO(+)3, O(+) and C(+) are compared with those in the photoelectron spectrum reported for CO2.

Analytic calculation of 1-jettiness in DIS at O (α s)

DOE PAGES

Kang, Daekyoung; Lee, Christopher; Stewart, Iain W.

2014-11-01

We present an analytic O(α s) calculation of cross sections in deep inelastic scattering (DIS) dependent on an event shape, 1-jettiness, that probes final states with one jet plus initial state radiation. This is the first entirely analytic calculation for a DIS event shape cross section at this order. We present results for the differential and cumulative 1-jettiness cross sections, and express both in terms of structure functions dependent not only on the usual DIS variables x, Q 2 but also on the 1-jettiness τ. Combined with previous results for log resummation, predictions are obtained over the entire range ofmore » the 1-jettiness distribution.« less

A Stochastic Approach For Extending The Dimensionality Of Observed Datasets

NASA Technical Reports Server (NTRS)

Varnai, Tamas

2002-01-01

This paper addresses the problem that in many cases, observations cannot provide complete fields of the measured quantities, because they yield data only along a single cross-section through the examined fields. The paper describes a new Fourier-adjustment technique that allows existing fractal models to build realistic surroundings to the measured cross-sections. This new approach allows more representative calculations of cloud radiative processes and may be used in other areas as well.

Ti:sapphire - A theoretical assessment for its spectroscopy

NASA Astrophysics Data System (ADS)

Da Silva, A.; Boschetto, D.; Rax, J. M.; Chériaux, G.

2017-03-01

This article tries to theoretically compute the stimulated emission cross-sections when we know the oscillator strength of a broad material class (dielectric crystals hosting metal-transition impurity atoms). We apply the present approach to Ti:sapphire and check it by computing some emission cross-section curves for both π and σ polarizations. We also set a relationship between oscillator strength and radiative lifetime. Such an approach will allow future parametric studies for Ti:sapphire spectroscopic properties.

Acoustic attraction, repulsion and radiation force cancellation on a pair of rigid particles with arbitrary cross-sections in 2D: Circular cylinders example

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2017-11-01

The acoustic radiation forces arising on a pair of sound impenetrable cylindrical particles of arbitrary cross-sections are derived. Plane progressive, standing or quasi-standing waves with an arbitrary incidence angle are considered. Multiple scattering effects are described using the multipole expansion formalism and the addition theorem of cylindrical wave functions. An effective incident acoustic field on a particular object is determined, and used with the scattered field to derive closed-form analytical expressions for the radiation force vector components. The mathematical expressions for the radiation force components are exact, and have been formulated in partial-wave series expansions in cylindrical coordinates involving the angle of incidence, the reflection coefficient forming the progressive or the (quasi)standing wave field, the addition theorem, and the expansion coefficients. Numerical examples illustrate the analysis for two rigid circular cross-sections immersed in a non-viscous fluid. Computations for the dimensionless radiation force functions are performed with emphasis on varying the angle of incidence, the interparticle distance, the sizes of the particles as well as the characteristics of the incident field. Depending on the interparticle distance and angle of incidence, one of the particles yields neutrality; it experiences no force and becomes unresponsive (i.e., ;invisible;) to the linear momentum transfer of the effective incident field due to multiple scattering cancellation effects. Moreover, attractive or repulsive forces between the two particles may arise depending on the interparticle distance, the angle of incidence and size parameters of the particles. This study provides a complete analytical method and computations for the axial and transverse radiation force components in multiple acoustic scattering encompassing the cases of plane progressive, standing or quasi-standing waves of arbitrary incidence by a pair of scatterers. Potential applications concern the prediction of the forces used in acoustically-engineered metamaterials with reconfigurable periodicities, cloaking devices, and liquid crystals to name a few examples.

Temperature dependence of the cross section for the fragmentation of thymine via dissociative electron attachment

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

Kopyra, Janina; Abdoul-Carime, Hassan, E-mail: hcarime@ipnl.in2p3.fr

Providing experimental values for absolute Dissociative Electron Attachment (DEA) cross sections for nucleobases at realistic biological conditions is a considerable challenge. In this work, we provide the temperature dependence of the cross section, σ, of the dehydrogenated thymine anion (T − H){sup −} produced via DEA. Within the 393-443 K temperature range, it is observed that σ varies by one order of magnitude. By extrapolating to a temperature of 313 K, the relative DEA cross section for the production of the dehydrogenated thymine anion at an incident energy of 1 eV decreases by 2 orders of magnitude and the absolutemore » value reaches approximately 6 × 10{sup −19} cm{sup 2}. These quantitative measurements provide a benchmark for theoretical prediction and also a contribution to a more accurate description of the effects of ionizing radiation on molecular medium.« less

Radiative neutron capture cross section from 236U

NASA Astrophysics Data System (ADS)

Baramsai, B.; Jandel, M.; Bredeweg, T. A.; Bond, E. M.; Roman, A. R.; Rusev, G.; Walker, C. L.; Couture, A.; Mosby, S.; O'Donnell, J. M.; Ullmann, J. L.; Kawano, T.

2017-08-01

The 236U(n ,γ ) reaction cross section has been measured for the incident neutron energy range from 10 eV to 800 keV by using the Detector for Advanced Neutron Capture Experiments (DANCE) γ -ray calorimeter at the Los Alamos Neutron Science Center. The cross section was determined with the ratio method, which is a technique that uses the 235U(n ,f ) reaction as a reference. The results of the experiment are reported in the resolved and unresolved resonance energy regions. Individual neutron resonance parameters were obtained below 1 keV incident energy by using the R -matrix code sammy. The cross section in the unresolved resonance region is determined with improved experimental uncertainty. It agrees with both ENDF/B-VII.1 and JEFF-3.2 nuclear data libraries. The results above 10 keV agree better with the JEFF-3.2 library.

Radiative capture reactions via indirect methods

NASA Astrophysics Data System (ADS)

Mukhamedzhanov, A. M.; Rogachev, G. V.

2017-10-01

Many radiative capture reactions of astrophysical interest occur at such low energies that their direct measurement is hardly possible. Until now the only indirect method, which was used to determine the astrophysical factor of the astrophysical radiative capture process, was the Coulomb dissociation. In this paper we address another indirect method, which can provide information about resonant radiative capture reactions at astrophysically relevant energies. This method can be considered an extension of the Trojan horse method for resonant radiative capture reactions. The idea of the suggested indirect method is to use the indirect reaction A (a ,s γ )F to obtain information about the radiative capture reaction A (x ,γ )F , where a =(s x ) and F =(x A ) . The main advantage of using the indirect reactions is the absence of the penetrability factor in the channel x +A , which suppresses the low-energy cross sections of the A (x ,γ )F reactions and does not allow one to measure these reactions at astrophysical energies. A general formalism to treat indirect resonant radiative capture reactions is developed when only a few intermediate states contribute and a statistical approach cannot be applied. The indirect method requires coincidence measurements of the triple differential cross section, which is a function of the photon scattering angle, energy, and the scattering angle of the outgoing spectator particle s . Angular dependence of the triple differential cross section at fixed scattering angle of the spectator s is the angular γ -s correlation function. Using indirect resonant radiative capture reactions, one can obtain information about important astrophysical resonant radiative capture reactions such as (p ,γ ) , (α ,γ ) , and (n ,γ ) on stable and unstable isotopes. The indirect technique makes accessible low-lying resonances, which are close to the threshold, and even subthreshold bound states located at negative energies. In this paper, after developing the general formalism, we demonstrate the application of the indirect reaction 12C(6Li,d γ )16O proceeding through 1- and 2+ subthreshold bound states and resonances to obtain the information about the 12C(α ,γ )16O radiative capture at the astrophysically most effective energy 0.3 MeV, which is impossible using standard direct measurements. Feasibility of the suggested approach is discussed.

X-ray fluorescence cross sections for K and L x rays of the elements

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

Krause, M.O.; Nestor, C.W. Jr.; Sparks, C.J. Jr.

1978-06-01

X-ray fluorescence cross sections are calculated for the major x rays of the K series 5 less than or equal to Z less than or equal to 101, and the three L series 12 less than or equal to Z less than or equal to 101 in the energy range 1 to 200 keV. This calculation uses Scofield's theoretical partical photoionization cross sections, Krause's evaluation of fluorescence and Coster-Kronig yields, and Scofield's theoretical radiative rates. Values are presented in table and graph format, and an estimate of their accuracy is made. The following x rays are considered: K..cap alpha../sub 1/,more » K..cap alpha../sub 1/,/sub 2/, K..beta../sub 1/, K..beta../sub 1/,/sub 3/, L..cap alpha../sub 1/, L..cap alpha../sub 1/,/sub 2/, L..beta../sub 1/, L..beta../sub 2/,/sub 15/, L..beta../sub 3/, Ll, L..gamma../sub 1/, L..gamma../sub 4/, and L/sub 1/ ..-->.. L/sub 2/,/sub 3/. For use in x-ray fluorescence analysis, K..cap alpha.. and L..cap alpha.. fluorescence cross sections are presented at specific energies: TiK identical with 4.55 keV, CrK identical with 5.46 keV, CoK identical with 7.00 keV, CuK identical with 8.13 keV, MoK..cap alpha.. identical with 17.44 keV, AgK identical with 22.5 keV, DyK identical with 47.0 keV, and /sup 241/Am identical with 59.54 keV. Supplementary material includes fluorescence and Coster--Kronig yields, fractional radiative rates, fractional fluorescence yields, total L-shell fluorescence cross sections, fluorescence and Coster-Kronig yields in condensed matter, effective fluorescence yields, average L-shell fluorescence yield, L-subshell photoionization cross section ratios, and conversion factors from barns per atom to square centimeters per gram.« less

Low activated incore instrument

DOEpatents

Ekeroth, Douglas E.

1994-01-01

Instrumentation for nuclear reactor head-mounted incore instrumentation systems fabricated of low nuclear cross section materials (i.e., zirconium or titanium). The instrumentation emits less radiation than that fabricated of conventional materials.

Generation and amplification of sub-THz radiation in a rare gases plasma formed by a two-color femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Bogatskaya, A. V.; Volkova, E. A.; Popov, A. M.

2018-06-01

A new approach to constructing the source of radiation in the sub-THz frequency range is discussed. It is based on the strong-field ionization of heavy rare gases with Ramsauer minimum in the transport cross-section by a two-color () femtosecond laser pulse. Then a four-photon nonlinear process ( are the frequencies from the spectral width of the pulse with frequency ω, and is the frequency from the spectral width of the second harmonic 2ω) with a transition to the initial state results in a low-frequency spontaneous emission that can be amplified in the strongly nonequilibrium laser plasma if the position of the photoelectron peaks is located in the region of growing energy transport cross-section.

Synchrotron radiation based cross-sectional scanning photoelectron microscopy and spectroscopy of n-ZnO:Al/p-GaN:Mg heterojunction

NASA Astrophysics Data System (ADS)

Lee, Kai-Hsuan; Chang, Ping-Chuan; Chen, Tse-Pu; Chang, Sheng-Po; Shiu, Hung-Wei; Chang, Lo-Yueh; Chen, Chia-Hao; Chang, Shoou-Jinn

2013-02-01

Al-doped ZnO (AZO) deposited by radio frequency co-sputtering is formed on epitaxial Mg-doped GaN template at room temperature to achieve n-AZO/p-GaN heterojunction. Alignment of AZO and GaN bands is investigated using synchrotron radiation based cross-sectional scanning photoelectron microscopy and spectroscopy on the nonpolar side-facet of a vertically c-axis aligned heterostructure. It shows type-II band configuration with valence band offset of 1.63 ± 0.1 eV and conduction band offset of 1.61 ± 0.1 eV, respectively. Rectification behavior is clearly observed, with a ratio of forward-to-reverse current up to six orders of magnitude when the bias is applied across the p-n junction.

Synchrotron radiation based cross-sectional scanning photoelectron microscopy and spectroscopy of n-ZnO:Al/p-GaN:Mg heterojunction

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

Lee, Kai-Hsuan; Chen, Chia-Hao; Chang, Ping-Chuan

2013-02-18

Al-doped ZnO (AZO) deposited by radio frequency co-sputtering is formed on epitaxial Mg-doped GaN template at room temperature to achieve n-AZO/p-GaN heterojunction. Alignment of AZO and GaN bands is investigated using synchrotron radiation based cross-sectional scanning photoelectron microscopy and spectroscopy on the nonpolar side-facet of a vertically c-axis aligned heterostructure. It shows type-II band configuration with valence band offset of 1.63 {+-} 0.1 eV and conduction band offset of 1.61 {+-} 0.1 eV, respectively. Rectification behavior is clearly observed, with a ratio of forward-to-reverse current up to six orders of magnitude when the bias is applied across the p-n junction.

Influence of magnetite, ilmenite and boron carbide on radiation attenuation of polyester composites

NASA Astrophysics Data System (ADS)

El-Sarraf, M. A.; El-Sayed Abdo, A.

2013-07-01

This work is concerned with studying polyester/ magnetite CUP/Mag (ρ=2.75 g cm-3) and polyester/ ilmenite CUP/Ilm (ρ=2.7 g cm-3) composites for shielding of medical facilities, laboratory hot cells and for various purposes. Mechanical and physical properties such as compressive, flexural and impact strengths, as well as, a.c. electrical conductivity, specific heat, water absorption and porosity have been performed to evaluate the composite capabilities for radiation shielding. A collimated beam from fission 252Cf (100 µg) neutron source and neutron-gamma spectrometer with stilbene scintillator based on the zero cross over method and pulse shape discrimination (P.S.D.) technique have been used to measure neutron and gamma ray spectra. Fluxes of thermal neutrons have been measured using the BF3 detector and thermal neutron detection system. The attenuation parameters, namely macroscopic effective removal cross-section ΣR, total attenuation coefficient µ and macroscopic cross-section Σ of fast neutrons, gamma rays and thermal neutrons respectively have been evaluated. Theoretical calculations using MCNP-4C2 code was used to calculate ΣR,μ and Σ. Also, MERCSF-N program was used to calculate macroscopic effective removal cross-section ΣR. Measured and calculated results were compared and reasonable agreement was found.

Quantum diffraction and shielding effects on the low-energy electron-ion bremsstrahlung in two-component semiclassical plasmas

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

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590

2015-10-15

The quantum diffraction and shielding effects on the low-energy bremsstrahlung process are investigated in two-component semiclassical plasmas. The impact-parameter analysis with the micropotential taking into account the quantum diffraction and shielding effects is employed to obtain the electron-ion bremsstrahlung radiation cross section as a function of the de Broglie wavelength, density parameter, impact parameter, photon energy, and projectile energy. The result shows that the influence of quantum diffraction and shielding strongly suppresses the bremsstrahlung radiation spectrum in semiclassical plasmas. It is found that the quantum diffraction and shielding effects have broaden the photon emission domain. It is also found thatmore » the photon emission domain is almost independent of the radiation photon energy. In addition, it is found that the influence of quantum diffraction and shielding on the bremsstrahlung spectrum decreases with an increase of the projectile energy. The density effect on the electron-ion bremsstrahlung cross section is also discussed.« less

Ionization Cross Sections and Dissociation Channels of the DNA Sugar-Phosphate Backbone by Electron Collisions

NASA Technical Reports Server (NTRS)

Dateo, Christopher; Huo, Winifred M.; Fletcher, Graham D.

2004-01-01

It has been suggested that the genotoxic effects of ionizing radiation in living cells are not caused by the highly energetic incident radiation, but rather are induced by less energetic secondary species generated, the most abundant of which are free electrons.' The secondary electrons will further react to cause DNA damage via indirect and direct mechanisms. Detailed knowledge of these mechanisms is ultimately important for the development of global models of cellular radiation damage. We are studying one possible mechanism for the formation cf DNA strand breaks involving dissociative ionization of the DNA sugar-phosphate backbone induced by secondary electron co!lisions. We will present ionization cross sections at electron collision energies between threshold and 10 KeV using the improved binary encounter dipole (iBED) formulation' Preliminary results of the possible dissociative ionization pathways will be presented. It is speculated that radical fragments produced from the dissociative ionization can further react, providing a possible mechanism for double strand breaks and base damage.

Performance study of galactic cosmic ray shield materials

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; Wilson, John W.; Thibeault, Sheila A.; Nealy, John E.; Badavi, Francis F.; Kiefer, Richard L.

1994-01-01

The space program is faced with two difficult radiation protection issues for future long-term operations. First, retrofit of shield material or conservatism in shield design is prohibitively expensive and often impossible. Second, shielding from the cosmic heavy ions is faced with limited knowledge on the physical properties and biological responses of these radiations. The current status of space shielding technology and its impact on radiation health is discussed herein in terms of conventional protection practice and a test biological response model. The impact of biological response on the selection of optimum materials for cosmic ray shielding is presented in terms of the transmission characteristics of the shield material. Although the systematics of nuclear cross sections are able to demonstrate the relation of exposure risk to shield-material composition, the current uncertainty in-nuclear cross sections will not allow an accurate evaluation of risk reduction. This paper presents a theoretical study of risk-related factors and a pilot experiment to study the effectiveness of choice of shield materials to reduce the risk in space operations.

Importance of Nuclear Physics to NASA's Space Missions

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.

2001-01-01

We show that nuclear physics is extremely important for accurate risk assessments for space missions. Due to paucity of experimental input radiation interaction information it is imperative to develop reliable accurate models for the interaction of radiation with matter. State-of-the-art nuclear cross sections models have been developed at the NASA Langley Research center and are discussed.

[Interventional radiology and radiation therapy].

PubMed

Hadjiev, Janaki

2015-04-26

The revolutionary role of modern cross-sectional imaging, the improved target definition in CT/MRI image guided brachytherapy, the precise topography for applicator and anatomy contribute to a better knowledge and management of tumors and critical organs. Further developments and functional imaging is expected to lead to a broad use of patient tailored therapy in the field of interventional radiation oncology.

Inclusive Prompt Photons from the Color Glass Condensate at NLO

NASA Astrophysics Data System (ADS)

Benić, Sanjin; Fukushima, Kenji; Garcia-Montero, Oscar; Venugopalan, Raju

2018-05-01

The cross-section for photons radiated by quarks in proton-nucleus collisions at collider energies was obtained using the Color Glass Condensate framework, in the dense-dilute kinematics regime. We observe that the inclusive photon cross-section is proportional to all-twist Wilson line correlators in the nucleus. These correlators also appear in quark-pair production; unlike the latter, photon production is insensitive to hadronization uncertainties and therefore more sensitive to multi-parton correlations in the gluon saturation regime of QCD.

Cross-Section Measurements of the Kr86(γ,n) Reaction to Probe the s-Process Branching at Kr85

NASA Astrophysics Data System (ADS)

Raut, R.; Tonchev, A. P.; Rusev, G.; Tornow, W.; Iliadis, C.; Lugaro, M.; Buntain, J.; Goriely, S.; Kelley, J. H.; Schwengner, R.; Banu, A.; Tsoneva, N.

2013-09-01

We have carried out photodisintegration cross-section measurements on Kr86 using monoenergetic photon beams ranging from the neutron separation energy, Sn=9.86MeV, to 13 MeV. We combine our experimental Kr86(γ,n)Kr85 cross section with results from our recent Kr86(γ,γ') measurement below the neutron separation energy to obtain the complete nuclear dipole response of Kr86. The new experimental information is used to predict the neutron capture cross section of Kr85, an important branching point nucleus on the abundance flow path during s-process nucleosynthesis. Our new and more precise Kr85(n,γ)Kr86 cross section allows us to produce more precise predictions of the Kr86 abundance from s-process models. In particular, we find that the models of the s process in asymptotic giant branch stars of mass <1.5M⊙, where the C13 neutron source burns convectively rather than radiatively, represent a possible solution for the highest Kr86∶Kr82 ratios observed in meteoritic stardust SiC grains.

Cross-section measurements of the 86Kr(γ,n) reaction to probe the s-process branching at 85Kr.

PubMed

Raut, R; Tonchev, A P; Rusev, G; Tornow, W; Iliadis, C; Lugaro, M; Buntain, J; Goriely, S; Kelley, J H; Schwengner, R; Banu, A; Tsoneva, N

2013-09-13

We have carried out photodisintegration cross-section measurements on 86Kr using monoenergetic photon beams ranging from the neutron separation energy, S(n) = 9.86  MeV, to 13 MeV. We combine our experimental 86Kr(γ,n)85Kr cross section with results from our recent 86Kr(γ,γ') measurement below the neutron separation energy to obtain the complete nuclear dipole response of 86Kr. The new experimental information is used to predict the neutron capture cross section of 85Kr, an important branching point nucleus on the abundance flow path during s-process nucleosynthesis. Our new and more precise 85Kr(n,γ)86Kr cross section allows us to produce more precise predictions of the 86Kr abundance from s-process models. In particular, we find that the models of the s process in asymptotic giant branch stars of mass <1.5M⊙, where the 13C neutron source burns convectively rather than radiatively, represent a possible solution for the highest 86Kr:82Kr ratios observed in meteoritic stardust SiC grains.

Absolute Total Photoionization Cross Section of C60 in the Range of 25-120 eV: Revisited

NASA Astrophysics Data System (ADS)

Kafle, Bhim P.; Katayanagi, Hideki; Prodhan, Md. Serajul I.; Yagi, Hajime; Huang, Chaoqun; Mitsuke, Koichiro

2008-01-01

The absolute total photoionization cross section σabs,I of gaseous C60 is measured in the photon energy hν range from 25 to 120 eV by photoionization mass spectrometry with synchrotron radiation. The absolute detection efficiencies of photoions in different charge states are evaluated. The present σabs,I curve is combined with the photoabsorption cross section curves of C60 at hν=3.5--26 eV in the literature, after appropriate alterations of the vapor pressure are taken into account. The oscillator strengths are computed from the composite curve to be 178.5 and 230.5 for the hν ranges from 3.5 to 40.8 eV and from 3.5 to 119 eV, respectively. These oscillator strengths agree well with those expected from the Thomas-Kuhn-Reiche sum rule and 60 times the photoabsorption cross section of a carbon atom. Moreover, the present σabs,I curve behaves similarly to the relative photoionization cross section curve reported by Reinköster et al.

Measurements of the 40Ar(n, γ)41Ar radiative-capture cross section between 0.4 and 14.8 MeV

NASA Astrophysics Data System (ADS)

Bhike, Megha; Fallin, B.; Tornow, W.

2014-09-01

The 40Ar(n, γ)41Ar neutron capture cross section has been measured between 0.4 and 14.8 MeV neutron energy using the activation technique. The data are important for estimating backgrounds in argon-based neutrino and dark-matter detectors and in the neutrino-less double-beta decay search GERDA, which uses liquid argon as cooling and shielding medium. For the first time the 40Ar(n, γ)41Ar cross section has been measured for neutron energies above 1 MeV. Our results are compared to the evaluation ENDF/B-VII.1 and the calculated prediction TENDL-2013. The latter agrees very well with the present results.

Application of JAERI quantum molecular dynamics model for collisions of heavy nuclei

NASA Astrophysics Data System (ADS)

Ogawa, Tatsuhiko; Hashimoto, Shintaro; Sato, Tatsuhiko; Niita, Koji

2016-06-01

The quantum molecular dynamics (QMD) model incorporated into the general-purpose radiation transport code PHITS was revised for accurate prediction of fragment yields in peripheral collisions. For more accurate simulation of peripheral collisions, stability of the nuclei at their ground state was improved and the algorithm to reject invalid events was modified. In-medium correction on nucleon-nucleon cross sections was also considered. To clarify the effect of this improvement on fragmentation of heavy nuclei, the new QMD model coupled with a statistical decay model was used to calculate fragment production cross sections of Ag and Au targets and compared with the data of earlier measurement. It is shown that the revised version can predict cross section more accurately.

Latest results from LUNA

NASA Astrophysics Data System (ADS)

Depalo, Rosanna; LUNA Collaboration

2018-01-01

A precise knowledge of the cross section of nuclear fusion reactions is a crucial ingredient in understanding stellar evolution and nucleosynthesis. At stellar temperatures, fusion cross sections are extremely small and difficult to measure. Measuring nuclear cross sections at astrophysical energies is a challenge that triggered a huge amount of experimental work. A breakthrough in this direction was the first operation of an underground accelerator at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Gran Sasso, Italy. The 1400 meters of rocks above the laboratory act as a natural shield against cosmic radiation, suppressing the background by orders of magnitude. The latest results achieved at LUNA are discussed, with special emphasis on the 22Ne(p,γ)23Na reaction. Future perspectives of the LUNA experiment are also illustrated.

Modification and benchmarking of MCNP for low-energy tungsten spectra.

PubMed

Mercier, J R; Kopp, D T; McDavid, W D; Dove, S B; Lancaster, J L; Tucker, D M

2000-12-01

The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x-ray spectra in the 30-150 kV range. Validating the modified code for coupled electron-photon transport with benchmark spectra was supplemented with independent electron-only and photon-only transport benchmarks. Major revisions to the code included the proper treatment of characteristic K x-ray production and scoring, new impact ionization cross sections, and new bremsstrahlung cross sections. Minor revisions included updated photon cross sections, electron-electron bremsstrahlung production, and K x-ray yield. The modified MCNP code is benchmarked to electron backscatter factors, x-ray spectra production, and primary and scatter photon transport.

Statistical Model Analysis of (n,p) Cross Sections and Average Energy For Fission Neutron Spectrum

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

Odsuren, M.; Khuukhenkhuu, G.

2011-06-28

Investigation of charged particle emission reaction cross sections for fast neutrons is important to both nuclear reactor technology and the understanding of nuclear reaction mechanisms. In particular, the study of (n,p) cross sections is necessary to estimate radiation damage due to hydrogen production, nuclear heating and transmutations in the structural materials of fission and fusion reactors. On the other hand, it is often necessary in practice to evaluate the neutron cross sections of the nuclides for which no experimental data are available.Because of this, we carried out the systematical analysis of known experimental (n,p) and (n,a) cross sections for fastmore » neutrons and observed a systematical regularity in the wide energy interval of 6-20 MeV and for broad mass range of target nuclei. To explain this effect using the compound, pre-equilibrium and direct reaction mechanisms some formulae were deduced. In this paper, in the framework of the statistical model known experimental (n,p) cross sections averaged over the thermal fission neutron spectrum of U-235 are analyzed. It was shown that the experimental data are satisfactorily described by the statistical model. Also, in the case of (n,p) cross sections the effective average neutron energy for fission spectrum of U-235 was found to be around 3 MeV.« less

Laminar flow studies of a low-temperature space radiator model using D-shaped tubes

NASA Technical Reports Server (NTRS)

Cintula, T. C.; Prok, G. M.; Johnston, D. B.

1972-01-01

Test results of a low-temperature space radiator model are presented. Radiator performance is evaluated with a low-thermal-conductivity fluid in laminar flow in D-shaped cross-section tubes. The test covered a Reynolds number range from 50 to 4500 and a fluid temperature range from 294 to 414 K (70 to 286 F). For low-temperature radiators, the fluid-to-surface temperature differential was predominately influenced by fluid temperature in laminar flow. Heat transfer and pressure drop for the radiator tube could be predicted within engineering accuracy from existing correlations.

Bubble chambers for experiments in nuclear astrophysics

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

DiGiovine, B.; Henderson, D.; Holt, R. J.

A bubble chamber has been developed to be used as an active target system for low energy nuclear astrophysics experiments. Adopting ideas from dark matter detection with superheated liquids, a detector system compatible with gamma-ray beams has been developed. This detector alleviates some of the limitations encountered in standard measurements of the minute cross sections of interest to stellar environments. While the astrophysically relevant nuclear reaction processes at hydrostatic burning temperatures are dominated by radiative captures, in this experimental scheme we measure the time reversed processes. Such photodisintegrations allow us to compute the radiative capture cross sections when transitions tomore » excited states of the reaction products are negligible. Due to the transformation of phase space, the photodisintegration cross-sections are up to two orders of magnitude higher. The main advantage of the new target-detector system is a density several orders of magnitude higher than conventional gas targets. Also, the detector is virtually insensitive to the gamma-ray beam itself, thus allowing us to detect only the products of the nuclear reaction of interest. The development and the operation as well as the advantages and disadvantages of the bubble chamber are discussed.« less

Factors influencing photoluminescence and photocarrier lifetime in CdSeTe/CdMgTe double heterostructures

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

Swartz, Craig H.; Zaunbrecher, K. N.; Sohal, S.

2016-10-28

CdSeTe/CdMgTe double heterostructures were produced with both n-type and unintentionally doped absorber layers. Measurements of the dependence of photoluminescence intensity on excitation intensity were carried out, as well as measurements of time-resolved photoluminescence decay after an excitation pulse. It was found that decay times under very low photon injection conditions are dominated by a non-radiative Shockley-Read-Hall process described using a recombination center with an asymmetric capture cross section, where the cross section for holes is larger than that for electrons. As a result of the asymmetry, the center effectively extends photoluminescence decay by a hole trapping phenomenon. A reduction inmore » electron capture cross section appeared at doping densities over 10 16cm -3. An analysis of the excitation intensity dependence of room temperature photoluminescence revealed a strong relationship with doping concentration. Here, this allows estimates of the carrier concentration to be made through a non-destructive optical method. Iodine was found to be an effective n-type dopant for CdTe, allowing controllable carrier concentrations without an increased rate of non-radiative recombination.« less

Using Synchrotron Radiation Microtomography to Investigate Multi-scale Three-dimensional Microelectronic Packages

DOE PAGES

Carlton, Holly D.; Elmer, John W.; Li, Yan; ...

2016-04-13

For this study synchrotron radiation micro-­tomography, a non-destructive three-dimensional imaging technique, is employed to investigate an entire microelectronic package with a cross-sectional area of 16 x 16 mm. Due to the synchrotron’s high flux and brightness the sample was imaged in just 3 minutes with an 8.7 μm spatial resolution.

Low activated incore instrument

DOEpatents

Ekeroth, D.E.

1994-04-19

Instrumentation is described for nuclear reactor head-mounted incore instrumentation systems fabricated of low nuclear cross section materials (i.e., zirconium or titanium). The instrumentation emits less radiation than that fabricated of conventional materials. 9 figures.

Analysis of dosimetry from the H.B. Robinson unit 2 pressure vessel benchmark using RAPTOR-M3G and ALPAN

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

Fischer, G.A.

2011-07-01

Document available in abstract form only, full text of document follows: The dosimetry from the H. B. Robinson Unit 2 Pressure Vessel Benchmark is analyzed with a suite of Westinghouse-developed codes and data libraries. The radiation transport from the reactor core to the surveillance capsule and ex-vessel locations is performed by RAPTOR-M3G, a parallel deterministic radiation transport code that calculates high-resolution neutron flux information in three dimensions. The cross-section library used in this analysis is the ALPAN library, an Evaluated Nuclear Data File (ENDF)/B-VII.0-based library designed for reactor dosimetry and fluence analysis applications. Dosimetry is evaluated with the industry-standard SNLRMLmore » reactor dosimetry cross-section data library. (authors)« less

Imaging More Imagining less: An Insight into Knowledge, Attitude and Practice Regarding Radiation Risk on Pregnant Women among Dentists of Ghaziabad - A Cross Sectional Study.

PubMed

Prasad, Monika; Gupta, Ritu; Patthi, Basavaraj; Singla, Ashish; Pandita, Venisha; Kumar, Jishnu Krishna; Malhi, Ravneet; Vashishtha, Vaibhav

2016-07-01

The safety of diagnostic imaging during pregnancy is an important aspect for all clinicians. Pregnant women often do not receive proper dental care as the dentists are not aware of low diagnostic radiation doses involved in dental radiation. To assess awareness of radiation risks on pregnant women among dentists of Ghaziabad city. A total of 268 practicing dentists in Ghaziabad were selected for a questionnaire based cross-sectional study. Data consisted of 18 questions which assessed the knowledge, attitude and practice of dental professionals regarding radiation risks on pregnant women. The questionnaire was distributed and collected personally by the principal investigator. Data was analyzed by Mann Whitney U test and chi-square test. The level of significance was set at p ≤ 0.05. The results showed that the dentists who had attended continuing dental education program had increased level of knowledge regarding radiation effects among pregnant women as compared to the dentists who had not attended continuing dental education programs (p<0.05). Among them who had attended continuing dental education programs 93.3% were aware of the safe dose of radiation and 62% were aware of threshold radiation doses of pregnancy termination. On the contrary there was no significant difference in the knowledge, attitude and practice scores regarding radiation risks on pregnant women based on their academic qualification (p≥0.05). The level of knowledge among dentists was found to be satisfactory, this outcome shows that continuing dental education regarding radiation protection principles and its risks on pregnant women is required to ensure maximum safety both for clinician as well as pregnant women.

Density Functional Theory Calculations of Activation Energies for Non-radiative Carrier Capture by Deep Defect Levels in Semiconductors.

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

Modine, Normand Arthur; Wright, Alan F.; Lee, Stephen R.

Carrier recombination due to defects can have a major impact on device performance. The rate of defect-induced carrier recombination is determined by both defect levels and carrier capture cross-sections. Kohn-Sham density functional theory (DFT) has been widely and successfully used to predict defect levels in semiconductors and insulators, but only recently has work begun to focus on using DFT to determine carrier capture cross-sections. Lang and Henry worked out the fundamental theory of carrier-capture cross-sections in the 1970s and showed that, in most cases, room temperature carrier-capture cross-sections differ between defects primarily due to differences in the carrier capture activationmore » energies. Here, we present an approach to using DFT to calculate carrier capture activation energies that does not depend on perturbation theory or an assumed configuration coordinate, and we demonstrate this approach for the -3/-2 level of the Ga vacancy in wurtzite GaN.« less

Measurement of the 238U(n ,γ ) cross section up to 80 keV with the Total Absorption Calorimeter at the CERN n_TOF facility

NASA Astrophysics Data System (ADS)

Wright, T.; Guerrero, C.; Billowes, J.; Cano-Ott, D.; Mendoza, E.; Altstadt, S.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Barbagallo, M.; Bečvář, F.; Belloni, F.; Berthoumieux, E.; Bosnar, D.; Brugger, M.; Calviño, F.; Calviani, M.; Carrapiço, C.; Cerutti, F.; Chiaveri, E.; Chin, M.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Durán, I.; Dzysiuk, N.; Eleftheriadis, C.; Ferrari, A.; Fraval, K.; Furman, V.; Gómez-Hornillos, M. B.; Ganesan, S.; García, A. R.; Giubrone, G.; Gonçalves, I. F.; González-Romero, E.; Goverdovski, A.; Griesmayer, E.; Gunsing, F.; Gurusamy, P.; Heftrich, T.; Hernández-Prieto, A.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Karadimos, D.; Katabuchi, T.; Ketlerov, V.; Khryachkov, V.; Koehler, P.; Kokkoris, M.; Kroll, J.; Krtička, M.; Lampoudis, C.; Langer, C.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Leong, L. S.; Lerendegui-Marco, J.; Losito, R.; Manousos, A.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Paradela, C.; Pavlik, A.; Perkowski, J.; Praena, J.; Quesada, J. M.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Robles, M.; Roman, F.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Sarmento, R.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tarrío, D.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vermeulen, M. J.; Versaci, R.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Ware, T.; Weigand, M.; Weiss, C.; Žugec, P.; n TOF Collaboration

2017-12-01

The radiative capture cross section of a highly pure (99.999%), 6.125(2) grams and 9.56(5)×10-4 atoms/barn areal density 238U sample has been measured with the Total Absorption Calorimeter (TAC) in the 185 m flight path at the CERN neutron time-of-flight facility n_TOF. This measurement is in response to the NEA High Priority Request list, which demands an accuracy in this cross section of less than 3% below 25 keV. These data have undergone careful background subtraction, with special care being given to the background originating from neutrons scattered by the 238U sample. Pileup and dead-time effects have been corrected for. The measured cross section covers an energy range between 0.2 eV and 80 keV, with an accuracy that varies with neutron energy, being better than 4% below 25 keV and reaching at most 6% at higher energies.

Determination of Spectroscopic Properties of Atmospheric Molecules from High Resolution Vacuum Ultraviolet Cross Section and Wavelength Measurements

NASA Technical Reports Server (NTRS)

Parkinson, W. H.; Yoshino, K.

1999-01-01

We have studied the spectroscopy and the cross sections of the simple molecules of atmospheric interest such as oxygen, nitric oxide, carbon dioxide, and water. We have made cross section measurements on an absolute base without the effects from the limited instrumental resolution. We have used the following different instruments- the grating spectrometer (6.65-m at CfA, 3-m at Photon Factory), VUV Fourier transform spectrometer at Imperial College, and then moved the same one to the Photon Factory. Selection of the instruments depend on the appearance of molecular bands, and their wavelength region. For example, the cross section measurements of Doppler limited bands can been done with the Fourier transform spectrometer at the very high resolution (0.025/ cm resolution). All of these spectroscopic measurements are needed for accurate calculations of the production of atomic oxygen penetration of solar radiation into the Earth's atmosphere, and photochemistry of minor molecules.

Effects of long-term low-level radiation exposure after the Chernobyl catastrophe on immunoglobulins in children residing in contaminated areas: prospective and cross-sectional studies

PubMed Central

2014-01-01

Background After the Chernobyl nuclear incident in 1986, children in the Narodichesky region, located 80 km west of the Chernobyl Power Plant, were exposed to 137Cesium (137Cs). Little is known about the effects of chronic low-level radiation on humoral immune responses in children residing in contaminated areas. Methods In four different approaches we investigated the effect of residential 137Cs exposure on immunoglobulins A, G, M, and specific immunoglobulin E in children. In a dynamic cohort (1993–1998) we included 617 children providing 2,407 repeated measurements; 421 and 523 children in two cross-sectional samples (1997–1998 and 2008–2010, respectively); and 25 participants in a small longitudinal cohort (1997–2010). All medical exams, blood collections, and analyses were conducted by the same team. We used mixed linear models to analyze repeated measurements in cohorts and general linear regression models for cross-sectional studies. Results Residential soil contamination in 2008 was highly correlated with the individual body burden of 137Cs. Serum IgG and IgM concentrations increased between 1993 and 1998. Children with higher 137Cs soil exposure had lower serum IgG levels, which, however, increased in the small cohort assessed between 1997 and 2010. Children within the fourth quintile of 137Cs soil exposure (266–310 kBq/m2) had higher IgM serum concentrations between 1993 and 1998 but these declined between 1997 and 2010. IgA remained stable with median 137Cs exposures related to higher IgA levels, which was corroborated in the cross-sectional study of 2008–2010. Specific IgE against indoor allergens was detected less often in children with higher 137Cs exposure. Conclusions Our findings show radiation-related alterations of immunoglobulins which by themselves do not constitute adverse health effects. Further investigations are necessary to understand how these changes affect health status. PMID:24886042

Monte Carlo study of microdosimetric diamond detectors

NASA Astrophysics Data System (ADS)

Solevi, Paola; Magrin, Giulio; Moro, Davide; Mayer, Ramona

2015-09-01

Ion-beam therapy provides a high dose conformity and increased radiobiological effectiveness with respect to conventional radiation-therapy. Strict constraints on the maximum uncertainty on the biological weighted dose and consequently on the biological weighting factor require the determination of the radiation quality, defined as the types and energy spectra of the radiation at a specific point. However the experimental determination of radiation quality, in particular for an internal target, is not simple and the features of ion interactions and treatment delivery require dedicated and optimized detectors. Recently chemical vapor deposition (CVD) diamond detectors have been suggested as ion-beam therapy microdosimeters. Diamond detectors can be manufactured with small cross sections and thin shapes, ideal to cope with the high fluence rate. However the sensitive volume of solid state detectors significantly deviates from conventional microdosimeters, with a diameter that can be up to 1000 times the height. This difference requires a redefinition of the concept of sensitive thickness and a deep study of the secondary to primary radiation, of the wall effects and of the impact of the orientation of the detector with respect to the radiation field. The present work intends to study through Monte Carlo simulations the impact of the detector geometry on the determination of radiation quality quantities, in particular on the relative contribution of primary and secondary radiation. The dependence of microdosimetric quantities such as the unrestricted linear energy L and the lineal energy y are investigated for different detector cross sections, by varying the particle type (carbon ions and protons) and its energy.

Radiation Effects on the Electrical Properties of MOS Device Materials.

DTIC Science & Technology

1978-02-01

3 Under Contract e ~i8 DAAG39~~ C.0O88 tJTtj~ J b This work _ sponsored by di. Ds~nse Nuclear Aisocy undur Nuclear ~ ffiupons Effucta flussarch...numb •r) Si02, MOS , CMOS Vacuum Ultraviolet Radiation Radiation Hardness Interfac e States Capture Cross Sections 2 ’ ~~’*~~ TRACT (Continu e on...When 0 t e Entered ) Results show that unannealed dry oxides have the lowest interface— state density after irrad iation, making them more desirable

Atomic Processes and Diagnostics of Low Pressure Krypton Plasma

NASA Astrophysics Data System (ADS)

Srivastava, Rajesh; Goyal, Dipti; Gangwar, Reetesh; Stafford, Luc

2015-03-01

Optical emission spectroscopy along with suitable collisional-radiative (CR) model is used in plasma diagnostics. Importance of reliable cross-sections for various atomic processes is shown for low pressure argon plasma. In the present work, radially-averaged Kr emission lines from the 2pi --> 1sj were recorded as a function of pressure from 1 to 50mTorr. We have developed a CR model using our fine-structure relativistic-distorted wave cross sections. The various processes considered are electron-impact excitation, ionization and their reverse processes. The required rate coefficients have been calculated from these cross-sections assuming Maxwellian energy distribution. Electron temperature obtained from the CR model is found to be in good agreement with the probe measurements. Work is supported by IAEA Vienna, DAE-BRNS Mumbai and CSIR, New Delhi.

New physics with ultra-high-energy neutrinos

DOE PAGES

Marfatia, D.; McKay, D. W.; Weiler, T. J.

2015-07-03

Now that PeV neutrinos have been discovered by IceCube, we optimistically entertain the possibility that neutrinos with energy above 100PeV exist. Here, we evaluate the dependence of event rates of such neutrinos on the neutrino-nucleon cross section at observatories that detect particles, atmospheric fluorescence, or Cherenkov radiation, initiated by neutrino interactions. We consider how (i)a simple scaling of the total standard model neutrino-nucleon cross section, (ii) a new elastic neutral current interaction, and (iii) anew completely inelastic interaction, individually impact event rates.

Fluid Dynamic and Stability Analysis of a Thin Liquid Sheet

NASA Technical Reports Server (NTRS)

McMaster, Matthew S.

1992-01-01

Interest in thin sheet flows has recently been renewed due to their potential application in space radiators. Theoretical and experimental studies of the fluid dynamics and stability of thin liquid sheet flows have been carried out in this thesis. A computer program was developed to determine the cross-sectional shape of the edge cylinder given the cross-sectional area of the edge cylinder. A stability analysis was performed on a non-planer liquid sheet. A study was conducted to determine the effects of air resistance on the sheet.

Who was concerned about radiation, food safety, and natural disasters after the great East Japan earthquake and Fukushima catastrophe? A nationwide cross-sectional survey in 2012.

PubMed

Sugimoto, Takashi; Shinozaki, Tomohiro; Naruse, Takashi; Miyamoto, Yuki

2014-01-01

Disaster-related concerns by sub-populations have not been clarified after the great East Japan earthquake and the Fukushima nuclear power plant incidents. This paper assesses who was concerned about radiation, food safety, and natural disasters among the general population in order to buffer such concerns effectively. The hypothesis that women, parents, and family caregivers were most concerned about radiation, food safety, and natural disaster was tested using a varying-intercept multivariable logistic regression with 5809 responses from a nationwide cross-sectional survey random-sampled in March 2012. Many people were at least occasionally concerned about radiation (53.5%), food safety (47.3%), and about natural disaster (69.5%). Women were more concerned than men about radiation (OR = 1.67; 95% CI = 1.35-2.06), food safety (1.70; 1.38-2.10), and natural disasters (1.74; 1.39-2.19). Parents and family care needs were not significant. Married couples were more concerned about radiation (1.53; 1.33-1.77), food safety (1.38; 1.20-1.59), and natural disasters (1.30; 1.12-1.52). Age, child-cohabitation, college-completion, retirement status, homemaker status, and the house-damage certificate of the last disaster were also associated with at least one concern. Participants from the Kanto region were more concerned about radiation (2.08; 1.58-2.74) and food safety (1.30; 1.07-1.59), which demonstrate similar positive associations to participants from Tohoku where a disaster relief act was invoked (3.36; 2.25-5.01 about radiation, 1.49; 1.08-2.06 about food safety). Sectioning the populations by gender and other demographics will clarify prospective targets for interventions, allow for a better understanding of post-disaster concerns, and help communicate relevant information effectively.

Who Was Concerned about Radiation, Food Safety, and Natural Disasters after the Great East Japan Earthquake and Fukushima Catastrophe? A Nationwide Cross-Sectional Survey in 2012

PubMed Central

Sugimoto, Takashi; Shinozaki, Tomohiro; Naruse, Takashi; Miyamoto, Yuki

2014-01-01

Background Disaster-related concerns by sub-populations have not been clarified after the great East Japan earthquake and the Fukushima nuclear power plant incidents. This paper assesses who was concerned about radiation, food safety, and natural disasters among the general population in order to buffer such concerns effectively. Methods The hypothesis that women, parents, and family caregivers were most concerned about radiation, food safety, and natural disaster was tested using a varying-intercept multivariable logistic regression with 5809 responses from a nationwide cross-sectional survey random-sampled in March 2012. Results Many people were at least occasionally concerned about radiation (53.5%), food safety (47.3%), and about natural disaster (69.5%). Women were more concerned than men about radiation (OR = 1.67; 95% CI = 1.35–2.06), food safety (1.70; 1.38–2.10), and natural disasters (1.74; 1.39–2.19). Parents and family care needs were not significant. Married couples were more concerned about radiation (1.53; 1.33–1.77), food safety (1.38; 1.20–1.59), and natural disasters (1.30; 1.12–1.52). Age, child-cohabitation, college-completion, retirement status, homemaker status, and the house-damage certificate of the last disaster were also associated with at least one concern. Participants from the Kanto region were more concerned about radiation (2.08; 1.58–2.74) and food safety (1.30; 1.07–1.59), which demonstrate similar positive associations to participants from Tohoku where a disaster relief act was invoked (3.36; 2.25–5.01 about radiation, 1.49; 1.08–2.06 about food safety). Conclusions Sectioning the populations by gender and other demographics will clarify prospective targets for interventions, allow for a better understanding of post-disaster concerns, and help communicate relevant information effectively. PMID:25181292

Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

NASA Technical Reports Server (NTRS)

James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Bray, I.; Dziczek, D.; Kanik, I.; Ajello, J. M.

1997-01-01

The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range.

Inelastic neutron scattering cross-section measurements on 7Li and 63,65Cu

NASA Astrophysics Data System (ADS)

Nyman, Markus; Belloni, Francesca; Ichinkhorloo, Dagvadorj; Pirovano, Elisa; Plompen, Arjan; Rouki, Chariklia

2017-09-01

The γ-ray production cross section for the 477.6-keV transition in 7Li following inelastic neutron scattering has been measured from the reaction threshold up to 18 MeV. This cross section is interesting as a possible standard for other inelastic scattering measurements. The experiment was conducted at the Geel Electron LINear Accelerator (GELINA) pulsed white neutron source with the Gamma Array for Inelastic Neutron Scattering (GAINS) spectrometer. Previous measurements of this cross section are reviewed and compared with our results. Recently, this cross section has also been calculated using the continuum discretized coupled-channels (CDCC) method. Experiments for studying neutrinoless double-β decay (2β0ν) or other very rare processes require greatly reducing the background radiation level (both intrinsic and external). Copper is a common shielding and structural material, used extensively in experiments such as COBRA, CUORE, EXO, GERDA, and MAJORANA. Understanding the background contribution arising from neutron interactions in Cu is important when searching for very weak experimental signals. Neutron inelastic scattering on natCu was investigated with GAINS. The results are compared with previous experimental data and evaluated nuclear data libraries.

A Physics-Based Engineering Approach to Predict the Cross Section for Advanced SRAMs

NASA Astrophysics Data System (ADS)

Li, Lei; Zhou, Wanting; Liu, Huihua

2012-12-01

This paper presents a physics-based engineering approach to estimate the heavy ion induced upset cross section for 6T SRAM cells from layout and technology parameters. The new approach calculates the effects of radiation with junction photocurrent, which is derived based on device physics. The new and simple approach handles the problem by using simple SPICE simulations. At first, the approach uses a standard SPICE program on a typical PC to predict the SPICE-simulated curve of the collected charge vs. its affected distance from the drain-body junction with the derived junction photocurrent. And then, the SPICE-simulated curve is used to calculate the heavy ion induced upset cross section with a simple model, which considers that the SEU cross section of a SRAM cell is more related to a “radius of influence” around a heavy ion strike than to the physical size of a diffusion node in the layout for advanced SRAMs in nano-scale process technologies. The calculated upset cross section based on this method is in good agreement with the test results for 6T SRAM cells processed using 90 nm process technology.

M ξ, M αβ, M γ and M m X-ray production cross-sections for elements with 71⩽ z⩽92 at 5.96 keV photon energy

NASA Astrophysics Data System (ADS)

Sharma, Manju; Sharma, Veena; Kumar, Sanjeev; Puri, S.; Singh, Nirmal

2006-11-01

The M ξ, M αβ, M γ and M m X-ray production (XRP) cross-sections have been measured for the elements with 71⩽ Z⩽92 at 5.96 keV incident photon energy satisfying EM1< Einc< EL3, where EM1(L3) is the M 1(L 3) subshell binding energy. These XRP cross-sections have been calculated using photoionization cross-sections based on the relativistic Dirac-Hartree-Slater (RDHS) model with three sets of X-ray emission rates, fluorescence, Coster-Kronig and super Coster-Kronig yields based on (i) the non-relativistic Hartree-Slater (NRHS) potential model, (ii) the RDHS model and (iii) the relativistic Dirac-Fock (RDF) model. For the third set, the M i ( i=1-5) subshell fluorescence yields have been calculated using the RDF model-based X-ray emission rates and total widths reevaluated to incorporate the RDF model-based radiative widths. The measured cross-sections have been compared with the calculated values to check the applicability of the physical parameters based on different models.

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

NASA Astrophysics Data System (ADS)

Heays, A. N.; Bosman, A. D.; van Dishoeck, E. F.

2017-06-01

A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic physical processes involved. These have been used to calculate dissociation and ionisation rates, with uncertainties, in a standard ultraviolet interstellar radiation field (ISRF) and for other wavelength-dependent radiation fields, including cool stellar and solar radiation, Lyman-α dominated radiation, and a cosmic-ray induced ultraviolet flux. The new ISRF rates generally agree within 30% with our previous compilations, with a few notable exceptions. Comparison with other databases such as PHIDRATES is made. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic C, and self-shielding column densities. The relative importance of these shielding types depends on the atom or molecule in question and the assumed dust optical properties. All of the new data are publicly available from the Leiden photodissociation and ionisation database. Sensitivity of the calculated rates to variation of temperature and isotope, and uncertainties in measured or calculated cross sections, are tested and discussed. Tests were conducted on the new rates with an interstellar-cloud chemical model, and find general agreement (within a factor of two) in abundances obtained with the previous iteration of the Leiden database assuming an ISRF, and order-of-magnitude variations assuming various kinds of stellar radiation. The newly parameterised dust-shielding factors makes a factor-of-two difference to many atomic and molecular abundances relative to parameters currently in the UDfA and KIDA astrochemical reaction databases. The newly-calculated cosmic-ray induced photodissociation and ionisation rates differ from current standard values up to a factor of 5. Under high temperature and cosmic-ray-flux conditions the new rates alter the equilibrium abundances of abundant dark cloud abundances by up to a factor of two. The partial cross sections for H2O and NH3 photodissociation forming OH, O, NH2 and NH are also evaluated and lead to radiation-field-dependent branching ratios.

Relativistic impulse dynamics.

PubMed

Swanson, Stanley M

2011-08-01

Classical electrodynamics has some annoying rough edges. The self-energy of charges is infinite without a cutoff. The calculation of relativistic trajectories is difficult because of retardation and an average radiation reaction term. By reconceptuallizing electrodynamics in terms of exchanges of impulses rather than describing it by forces and potentials, we eliminate these problems. A fully relativistic theory using photonlike null impulses is developed. Numerical calculations for a two-body, one-impulse-in-transit model are discussed. A simple relationship between center-of-mass scattering angle and angular momentum was found. It reproduces the Rutherford cross section at low velocities and agrees with the leading term of relativistic distinguishable-particle quantum cross sections (Møller, Mott) when the distance of closest approach is larger than the Compton wavelength of the particle. Magnetism emerges as a consequence of viewing retarded and advanced interactions from the vantage point of an instantaneous radius vector. Radiation reaction becomes the local conservation of energy-momentum between the radiating particle and the emitted impulse. A net action is defined that could be used in developing quantum dynamics without potentials. A reinterpretation of Newton's laws extends them to relativistic motion.

Event Generators for Simulating Heavy Ion Interactions of Interest in Evaluating Risks in Human Spaceflight

NASA Technical Reports Server (NTRS)

Wilson, Thomas L.; Pinsky, Lawrence; Andersen, Victor; Empl, Anton; Lee, Kerry; Smirmov, Georgi; Zapp, Neal; Ferrari, Alfredo; Tsoulou, Katerina; Roesler, Stefan;

Spectroscopic properties of Nd3+ doped transparent oxyfluoride glass ceramics.

PubMed

Yu, Yunlong; Chen, Daqin; Ma, En; Wang, Yuansheng; Hu, Zhongjian

2007-07-01

In this paper, the spectroscopic properties of Nd(3+) doped transparent oxyfluoride glass ceramics containing LaF(3) nano-crystals were systematically studied. The formation and distribution of LaF(3) nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd-Ofelt theory, the intensity parameters Omega(t) (t=2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd(3+) were evaluated. Particularly, the effect of Nd(3+) doping level on them was discussed. With the increase of Nd(3+) concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4 micros, 78.3% and 1.86 x 10(-20)cm(2) to 214.7 micros, 39.9% and 1.52 x 10(-20)cm(2), respectively. The comparative study of Nd(3+) spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06 microm emission.

Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS).

PubMed

Einstein, Andrew J; Pascual, Thomas N B; Mercuri, Mathew; Karthikeyan, Ganesan; Vitola, João V; Mahmarian, John J; Better, Nathan; Bouyoucef, Salah E; Hee-Seung Bom, Henry; Lele, Vikram; Magboo, V Peter C; Alexánderson, Erick; Allam, Adel H; Al-Mallah, Mouaz H; Flotats, Albert; Jerome, Scott; Kaufmann, Philipp A; Luxenburg, Osnat; Shaw, Leslee J; Underwood, S Richard; Rehani, Madan M; Kashyap, Ravi; Paez, Diana; Dondi, Maurizio

2015-07-07

To characterize patient radiation doses from nuclear myocardial perfusion imaging (MPI) and the use of radiation-optimizing 'best practices' worldwide, and to evaluate the relationship between laboratory use of best practices and patient radiation dose. We conducted an observational cross-sectional study of protocols used for all 7911 MPI studies performed in 308 nuclear cardiology laboratories in 65 countries for a single week in March-April 2013. Eight 'best practices' relating to radiation exposure were identified a priori by an expert committee, and a radiation-related quality index (QI) devised indicating the number of best practices used by a laboratory. Patient radiation effective dose (ED) ranged between 0.8 and 35.6 mSv (median 10.0 mSv). Average laboratory ED ranged from 2.2 to 24.4 mSv (median 10.4 mSv); only 91 (30%) laboratories achieved the median ED ≤ 9 mSv recommended by guidelines. Laboratory QIs ranged from 2 to 8 (median 5). Both ED and QI differed significantly between laboratories, countries, and world regions. The lowest median ED (8.0 mSv), in Europe, coincided with high best-practice adherence (mean laboratory QI 6.2). The highest doses (median 12.1 mSv) and low QI (4.9) occurred in Latin America. In hierarchical regression modelling, patients undergoing MPI at laboratories following more 'best practices' had lower EDs. Marked worldwide variation exists in radiation safety practices pertaining to MPI, with targeted EDs currently achieved in a minority of laboratories. The significant relationship between best-practice implementation and lower doses indicates numerous opportunities to reduce radiation exposure from MPI globally. © The Author 2015. Published by Oxford University Press on behalf of the European Society of Cardiology.

Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS)

PubMed Central

Einstein, Andrew J.; Pascual, Thomas N. B.; Mercuri, Mathew; Karthikeyan, Ganesan; Vitola, João V.; Mahmarian, John J.; Better, Nathan; Bouyoucef, Salah E.; Hee-Seung Bom, Henry; Lele, Vikram; Magboo, V. Peter C.; Alexánderson, Erick; Allam, Adel H.; Al-Mallah, Mouaz H.; Flotats, Albert; Jerome, Scott; Kaufmann, Philipp A.; Luxenburg, Osnat; Shaw, Leslee J.; Underwood, S. Richard; Rehani, Madan M.; Kashyap, Ravi; Paez, Diana; Dondi, Maurizio

2015-01-01

Aims To characterize patient radiation doses from nuclear myocardial perfusion imaging (MPI) and the use of radiation-optimizing ‘best practices’ worldwide, and to evaluate the relationship between laboratory use of best practices and patient radiation dose. Methods and results We conducted an observational cross-sectional study of protocols used for all 7911 MPI studies performed in 308 nuclear cardiology laboratories in 65 countries for a single week in March–April 2013. Eight ‘best practices’ relating to radiation exposure were identified a priori by an expert committee, and a radiation-related quality index (QI) devised indicating the number of best practices used by a laboratory. Patient radiation effective dose (ED) ranged between 0.8 and 35.6 mSv (median 10.0 mSv). Average laboratory ED ranged from 2.2 to 24.4 mSv (median 10.4 mSv); only 91 (30%) laboratories achieved the median ED ≤ 9 mSv recommended by guidelines. Laboratory QIs ranged from 2 to 8 (median 5). Both ED and QI differed significantly between laboratories, countries, and world regions. The lowest median ED (8.0 mSv), in Europe, coincided with high best-practice adherence (mean laboratory QI 6.2). The highest doses (median 12.1 mSv) and low QI (4.9) occurred in Latin America. In hierarchical regression modelling, patients undergoing MPI at laboratories following more ‘best practices’ had lower EDs. Conclusion Marked worldwide variation exists in radiation safety practices pertaining to MPI, with targeted EDs currently achieved in a minority of laboratories. The significant relationship between best-practice implementation and lower doses indicates numerous opportunities to reduce radiation exposure from MPI globally. PMID:25898845

Soft-Collinear Mode for Jet Rates in Soft-Collinear Effective Theory

DOE PAGES

Chien, Yang-Ting; Lee, Christopher; Hornig, Andrew

2016-01-29

We propose the addition of a new "soft-collinear" mode to soft collinear effective theory (SCET) below the usual soft scale to factorize and resum logarithms of jet radii R in jet cross sections. We consider exclusive 2-jet cross sections in e +e - collisions with an energy veto Λ on additional jets. The key observation is that there are actually two pairs of energy scales whose ratio is R: the transverse momentum QR of the energetic particles inside jets and their total energy Q, and the transverse momentum ΛR of soft particles that are cut out of the jet cones and their energy Λ. The soft-collinear mode is necessary to factorize and resum logarithms of the latter hierarchy. We show how this factorization occurs in the jet thrust cross section for cone and k T-type algorithms at O(α s) and using the thrust cone algorithm at O(αmore » $$2\\atop{s}$$). We identify the presence of hard-collinear, in-jet soft, global (veto) soft, and soft-collinear modes in the jet thrust cross section. We also observe here that the in-jet soft modes measured with thrust are actually the "csoft" modes of the theory SCET +. We dub the new theory with both csoft and soft-collinear modes "SCET ++". We go on to explain the relation between the "unmeasured" jet function appearing in total exclusive jet cross sections and the hard-collinear and csoft functions in measured jet thrust cross sections. We do not resum logs that are non-global in origin, arising from the ratio of the scales of soft radiation whose thrust is measured at Q$${{\\tau}}$$/R and of the soft-collinear radiation at 2ΛR. Their resummation would require the introduction of additional operators beyond those we consider here. The steps we outline here are a necessary part of summing logs of R that are global in nature and have not been factorized and resummed beyond leading-log level previously.« less

Soft-Collinear Mode for Jet Rates in Soft-Collinear Effective Theory

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

Chien, Yang-Ting; Lee, Christopher; Hornig, Andrew

We propose the addition of a new "soft-collinear" mode to soft collinear effective theory (SCET) below the usual soft scale to factorize and resum logarithms of jet radii R in jet cross sections. We consider exclusive 2-jet cross sections in e +e - collisions with an energy veto Λ on additional jets. The key observation is that there are actually two pairs of energy scales whose ratio is R: the transverse momentum QR of the energetic particles inside jets and their total energy Q, and the transverse momentum ΛR of soft particles that are cut out of the jet cones and their energy Λ. The soft-collinear mode is necessary to factorize and resum logarithms of the latter hierarchy. We show how this factorization occurs in the jet thrust cross section for cone and k T-type algorithms at O(α s) and using the thrust cone algorithm at O(αmore » $$2\\atop{s}$$). We identify the presence of hard-collinear, in-jet soft, global (veto) soft, and soft-collinear modes in the jet thrust cross section. We also observe here that the in-jet soft modes measured with thrust are actually the "csoft" modes of the theory SCET +. We dub the new theory with both csoft and soft-collinear modes "SCET ++". We go on to explain the relation between the "unmeasured" jet function appearing in total exclusive jet cross sections and the hard-collinear and csoft functions in measured jet thrust cross sections. We do not resum logs that are non-global in origin, arising from the ratio of the scales of soft radiation whose thrust is measured at Q$${{\\tau}}$$/R and of the soft-collinear radiation at 2ΛR. Their resummation would require the introduction of additional operators beyond those we consider here. The steps we outline here are a necessary part of summing logs of R that are global in nature and have not been factorized and resummed beyond leading-log level previously.« less

Advanced Antennas Enabled by Electromagnetic Metamaterials

DTIC Science & Technology

2014-12-01

radiation patterns of a conical horn antenna and three soft horns with various homogeneous metasurface liners. The maximum cross-polarization level was...inhomogencous metasurface liners covering both the flared horn section and the straight waveguide section. The mctahorn is fed by a circular waveguide...with a diameter of 20 mm. (b) The sizes of the metallic patches at each row of the metasurface in the flared horn section. Both the length and width

Potential scattering in the presence of a static magnetic field and a radiation field of arbitrary polarization

NASA Astrophysics Data System (ADS)

Ferrante, G.; Zarcone, M.; Nuzzo, S.; McDowell, M. R. C.

1982-05-01

Expressions are obtained for the total cross sections for scattering of a charged particle by a potential in the presence of a static uniform magnetic field and a radiation field of arbitrary polarization. For a Coulomb field this is closely related to the time reverse of photoionization of a neutral atom in a magnetic field, including multiphoton effects off-resonance. The model is not applicable when the radiation energy approaches one of the quasi-Landau state separations. The effects of radiation field polarization are examined in detail.

Dissociative excitation of the N(+)(5S) state by electron impact on N2 - Excitation function and quenching

NASA Technical Reports Server (NTRS)

Erdman, P. W.; Zipf, E. C.

1986-01-01

Metastable N(+)(5S) ions were produced in the laboratory by dissociative excitation of N2 with energetic electrons. The resulting radiative decay of the N(+)(5S) state was observed with sufficient resolution to completely resolve the doublet from the nearby N2 molecular radiation. The excitation function was measured from threshold to 500 eV. The cross section peaks at a high electron energy and also exhibits a high threshold energy both of which are typical of dissociative excitation-ionization processes. This finding complicates the explanation of electron impact on N2 as the mechanism for the source of the 2145 A 'auroral mystery feature' by further increasing the required peak cross section. It is suggested that the apparent N(+)(5S) quenching in auroras may be an artifact due to the softening of the electron energy spectrum in the auroral E region.

Study of the process e+e-→π+π-η using initial state radiation

NASA Astrophysics Data System (ADS)

Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Kolomensky, Yu. G.; Fritsch, M.; Koch, H.; Schroeder, T.; Hearty, C.; Mattison, T. S.; McKenna, J. A.; So, R. Y.; Blinov, V. E.; Buzykaev, A. R.; Druzhinin, V. P.; Golubev, V. B.; Kozyrev, E. A.; Kravchenko, E. A.; Onuchin, A. P.; Serednyakov, S. I.; Skovpen, Yu. I.; Solodov, E. P.; Todyshev, K. Yu.; Lankford, A. J.; Gary, J. W.; Long, O.; Eisner, A. M.; Lockman, W. S.; Panduro Vazquez, W.; Chao, D. S.; Cheng, C. H.; Echenard, B.; Flood, K. T.; Hitlin, D. G.; Kim, J.; Li, Y.; Miyashita, T. S.; Ongmongkolkul, P.; Porter, F. C.; Röhrken, M.; Huard, Z.; Meadows, B. T.; Pushpawela, B. G.; Sokoloff, M. D.; Sun, L.; Smith, J. G.; Wagner, S. R.; Bernard, D.; Verderi, M.; Bettoni, D.; Bozzi, C.; Calabrese, R.; Cibinetto, G.; Fioravanti, E.; Garzia, I.; Luppi, E.; Santoro, V.; Calcaterra, A.; de Sangro, R.; Finocchiaro, G.; Martellotti, S.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Rotondo, M.; Zallo, A.; Passaggio, S.; Patrignani, C.; Lacker, H. M.; Bhuyan, B.; Mallik, U.; Chen, C.; Cochran, J.; Prell, S.; Gritsan, A. V.; Arnaud, N.; Davier, M.; Le Diberder, F.; Lutz, A. M.; Wormser, G.; Lange, D. J.; Wright, D. M.; Coleman, J. P.; Gabathuler, E.; Hutchcroft, D. E.; Payne, D. J.; Touramanis, C.; Bevan, A. J.; Di Lodovico, F.; Sacco, R.; Cowan, G.; Banerjee, Sw.; Brown, D. N.; Davis, C. L.; Denig, A. G.; Gradl, W.; Griessinger, K.; Hafner, A.; Schubert, K. R.; Barlow, R. J.; Lafferty, G. D.; Cenci, R.; Jawahery, A.; Roberts, D. A.; Cowan, R.; Robertson, S. H.; Seddon, R. M.; Dey, B.; Neri, N.; Palombo, F.; Cheaib, R.; Cremaldi, L.; Godang, R.; Summers, D. J.; Taras, P.; De Nardo, G.; Sciacca, C.; Raven, G.; Jessop, C. P.; LoSecco, J. M.; Honscheid, K.; Kass, R.; Gaz, A.; Margoni, M.; Posocco, M.; Simi, G.; Simonetto, F.; Stroili, R.; Akar, S.; Ben-Haim, E.; Bomben, M.; Bonneaud, G. R.; Calderini, G.; Chauveau, J.; Marchiori, G.; Ocariz, J.; Biasini, M.; Manoni, E.; Rossi, A.; Batignani, G.; Bettarini, S.; Carpinelli, M.; Casarosa, G.; Chrzaszcz, M.; Forti, F.; Giorgi, M. A.; Lusiani, A.; Oberhof, B.; Paoloni, E.; Rama, M.; Rizzo, G.; Walsh, J. J.; Zani, L.; Smith, A. J. S.; Anulli, F.; Faccini, R.; Ferrarotto, F.; Ferroni, F.; Pilloni, A.; Piredda, G.; Bünger, C.; Dittrich, S.; Grünberg, O.; Heß, M.; Leddig, T.; Voß, C.; Waldi, R.; Adye, T.; Wilson, F. F.; Emery, S.; Vasseur, G.; Aston, D.; Cartaro, C.; Convery, M. R.; Dorfan, J.; Dunwoodie, W.; Ebert, M.; Field, R. C.; Fulsom, B. G.; Graham, M. T.; Hast, C.; Innes, W. R.; Kim, P.; Leith, D. W. G. S.; Luitz, S.; MacFarlane, D. B.; Muller, D. R.; Neal, H.; Ratcliff, B. N.; Roodman, A.; Sullivan, M. K.; Va'vra, J.; Wisniewski, W. J.; Purohit, M. V.; Wilson, J. R.; Randle-Conde, A.; Sekula, S. J.; Ahmed, H.; Bellis, M.; Burchat, P. R.; Puccio, E. M. T.; Alam, M. S.; Ernst, J. A.; Gorodeisky, R.; Guttman, N.; Peimer, D. R.; Soffer, A.; Spanier, S. M.; Ritchie, J. L.; Schwitters, R. F.; Izen, J. M.; Lou, X. C.; Bianchi, F.; De Mori, F.; Filippi, A.; Gamba, D.; Lanceri, L.; Vitale, L.; Martinez-Vidal, F.; Oyanguren, A.; Albert, J.; Beaulieu, A.; Bernlochner, F. U.; King, G. J.; Kowalewski, R.; Lueck, T.; Nugent, I. M.; Roney, J. M.; Sobie, R. J.; Tasneem, N.; Gershon, T. J.; Harrison, P. F.; Latham, T. E.; Prepost, R.; Wu, S. L.; BaBar Collaboration

2018-03-01

We study the process e+e- →π+π- η γ , where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BABAR data sample with an integrated luminosity of 469 fb-1 . Using the π+π-η invariant mass spectrum, we measure the e+e-→π+π- η cross section in the e+e- center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson dominance model with four ρ -like states. We observe 49 ±9 events of the J /ψ decay to π+π- η and measure the product ΓJ /Ψ →e+e-BJ /Ψ →π+π-η=2.34 ±0.4 3stat±0.1 6syst eV .

Radiative Correction to e+e-to e+e- in the Electroweak Theory. I --Cross Sections for Hard Photon Emission--

NASA Astrophysics Data System (ADS)

Tobimatsu, K.; Shimizu, Y.

1985-09-01

Various cross sections for radiative Bhabha scattering, e+e-to e+e-γ, are calculated in the standard electroweak theory. They contain distributions on photon energy dσ/dk, acollinearity angle dσ/dzeta, acoplanarity angle dσ/dψ, photon transverse momentum dσ/dkT and invariant mass of final e-γ system dσ/dMeγ. In the calculation some realistic experimental cuts are imposed on the configuration of final particles and the energies are chosen to be 70, 93 and 150 GeV in accordance with TRISTAN, SLC and LEP. From the results we can see the effect of Z0-boson exchanged in the s- and t-channel and estimate backgrounds to such interesting processes as e+e-toνbar{ν}γ, tilde{γ}tilde{γ}γ and e+e-to e*eto e+e-γ.

Cis- and trans-perfluorodecalin: Infrared spectra, radiative efficiency and global warming potential

NASA Astrophysics Data System (ADS)

Le Bris, Karine; DeZeeuw, Jasmine; Godin, Paul J.; Strong, Kimberly

2017-12-01

Perfluorodecalin (PFD) is a molecule used in various medical applications for its capacity to dissolve gases. This potent greenhouse gas was detected for the first time in the atmosphere in 2005. We present infrared absorption cross-section spectra of a pure vapour of cis- and trans-perfluorodecalin at a resolution of 0.1 cm-1. Measurements were performed in the 560-3000 cm-1 spectral range using Fourier transform spectroscopy. The spectra have been compared with previous experimental data and theoretical calculations by density functional theory. The new experimental absorption cross-sections have been used to calculate a lifetime-corrected radiative efficiency at 300 K of 0.62 W m-2 ppb-1 and 0.57 W.m-2.ppb-1 for the cis and trans isomers respectively. This leads to a 100-year time horizon global warming potential of 8030 for cis-PFD and 7440 for trans-PFD.

Electron and positron interaction with pyrimidine: A theoretical investigation

NASA Astrophysics Data System (ADS)

Sinha, Nidhi; Antony, Bobby

2018-03-01

Pyrimidine (C4H4N2) is considered as the building block of nucleobases, viz., cytosine, thymine and uracil. They provide a blueprint for probing the scattering of radiation by DNA and RNA bases. In this article, we report the elastic and total scattering cross-sections for electron and positron scattering from the pyrimidine molecule, employing a spherical complex optical potential (SCOP) formalism for an extensive energy range of 10 eV to 5 keV. In the case of positron scattering, the original SCOP formalism is modified to adequately solve the positron-target dynamics. Moreover, a reasonable agreement is observed between the present results and other available datasets, for both electron and positron scattering. The cross-sections for electron and positron impact scattering by pyrimidine are necessary input data for codes that seek to simulate radiation damage, and hence are useful to model biomolecular systems.

Measurement of the e + e - → K s 0 K ± π ∓ π 0 and K s 0 K ± π ∓ η cross sections using initial-state radiation

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

Lees, J. P.; Poireau, V.; Tisserand, V.

The processes e + e - → Kmore » $$0\\atop{S}$$ K ±π ∓π 0 and e + e - → K$$0\\atop{S}$$ K ±π ∓η are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb -1 of data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from K* 0(Kπ) 0, K *(892) ± (Kπ) ∓ , and K$$0\\atop{S}$$K ±ρ ∓ are studied. Lastly, the J / ψ is observed in all of these channels, and corresponding branching fractions are measured.« less

Measurement of the e + e - → K s 0 K ± π ∓ π 0 and K s 0 K ± π ∓ η cross sections using initial-state radiation

DOE PAGES

Lees, J. P.; Poireau, V.; Tisserand, V.; ...

2017-05-30

The processes e + e - → Kmore » $$0\\atop{S}$$ K ±π ∓π 0 and e + e - → K$$0\\atop{S}$$ K ±π ∓η are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb -1 of data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from K* 0(Kπ) 0, K *(892) ± (Kπ) ∓ , and K$$0\\atop{S}$$K ±ρ ∓ are studied. Lastly, the J / ψ is observed in all of these channels, and corresponding branching fractions are measured.« less

Extreme UV induced dissociation of amorphous solid water and crystalline water bilayers on Ru(0001)

NASA Astrophysics Data System (ADS)

Liu, Feng; Sturm, J. M.; Lee, Chris J.; Bijkerk, Fred

2016-04-01

The extreme ultraviolet (EUV, λ = 13.5 nm) induced dissociation of water layers on Ru(0001) was investigated. We irradiated amorphous and crystalline water layers on a Ru crystal with EUV light, and measured the surface coverage of remaining water and oxygen as a function of radiation dose by temperature programmed desorption (TPD). The main reaction products are OH and H with a fraction of oxygen from fully dissociated water. TPD spectra from a series of exposures reveal that EUV promotes formation of the partially dissociated water overlayer on Ru. Furthermore, loss of water due to desorption and dissociation is also observed. The water loss cross sections for amorphous and crystalline water are measured at 9 ± 2 × 10- 19 cm2 and 5 ± 1 × 10- 19 cm2, respectively. Comparison between the two cross sections suggests that crystalline water is more stable against EUV induced desorption/dissociation. The dissociation products can oxidize the Ru surface. For this early stage of oxidation, we measured a smaller (compared to water loss) cross section at 2 × 10- 20 cm2, which is 2 orders of magnitude smaller than the photon absorption cross section (at 92 eV) of gas phase water. The secondary electron (SE) contributions to the cross sections are also estimated. From our estimation, SE only forms a small part (20-25%) of the observed photon cross section.

Radiolysis of astrophysical ices by heavy ion irradiation: Destruction cross section measurement

NASA Astrophysics Data System (ADS)

de Barros, A. L. F.; Boduch, P.; Domaracka, A.; Rothard, H.; da Silveira, E. F.

2012-08-01

Many solar system objects, such as planets and their satellites, dust grains in rings, and comets, are known to either be made of ices or to have icy surfaces. These ices are exposed to ionizing radiation including keV, MeV and GeV ions from solar wind or cosmic rays. Moreover, icy dust grains are present in interstellar space and, in particular, in dense molecular clouds. Radiation effects include radiolysis (the destruction of molecules leading to formation of radicals), the formation of new molecules following radiolysis, the desorption or sputtering of atoms or molecules from the surface, compaction of porous ices, and phase changes. This review discusses the application of infrared spectroscopy FTIR to study the evolution of the chemical composition of ices containing the most abundant molecular species found in the solar system and interstellar medium, such as H2O, CO, CO2 and hydrocarbons. We focus on the evolution of chemical composition with ion fluence in order to deduce the corresponding destruction and formation cross sections. Although initial approach focused on product identification, it became increasingly necessary to work toward a comprehensive understanding of ice chemistry. The abundances of these molecules in different phases of ice mantles provide important clues to the chemical processes in dense interstellar clouds, and therefore it is of importance to accurately measure the quantities such as dissociation and formation cross sections of the infrared features of these molecules. We also are able to obtain the scaling of these cross sections with deposited energy.

Photoneutron reactions in astrophysics

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

Varlamov, V. V., E-mail: Varlamov@depni.sinp.msu.ru; Ishkhanov, B. S.; Orlin, V. N.

Among key problems in nuclear astrophysics, that of obtaining deeper insight into the mechanism of synthesis of chemical elements is of paramount importance. The majority of heavy elements existing in nature are produced in stars via radiative neutron capture in so-called s- and r processes, which are, respectively, slow and fast, in relation to competing β{sup −}-decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between {sup 74}Se and {sup 196}Hg and which cannot originate from the aforementioned s- and r-processes. Their production is possible in (γ, n), (γ, p), or (γ, α) photonuclearmore » reactions. In view of this, data on photoneutron reactions play an important role in predicting and describing processes leading to the production of p-nuclei. Interest in determining cross sections for photoneutron reactions in the threshold energy region, which is of particular importance for astrophysics, has grown substantially in recent years. The use of modern sources of quasimonoenergetic photons obtained in processes of inverse Compton laser-radiation scattering on relativistic electronsmakes it possible to reveal rather interesting special features of respective cross sections, manifestations of pygmy E1 and M1 resonances, or the production of nuclei in isomeric states, on one hand, and to revisit the problem of systematic discrepancies between data on reaction cross sections from experiments of different types, on the other hand. Data obtained on the basis of our new experimental-theoretical approach to evaluating cross sections for partial photoneutron reactions are invoked in considering these problems.« less

Radiation characteristics and effective optical properties of dumbbell-shaped cyanobacterium Synechocystis sp.

NASA Astrophysics Data System (ADS)

Heng, Ri-Liang; Pilon, Laurent

2016-05-01

This study presents experimental measurements of the radiation characteristics of unicellular freshwater cyanobacterium Synechocystis sp. during their exponential growth in F medium. Their scattering phase function at 633 nm average spectral absorption and scattering cross-sections between 400 and 750 nm were measured. In addition, an inverse method was used for retrieving the spectral effective complex index of refraction of overlapping or touching bispheres and quadspheres from their absorption and scattering cross-sections. The inverse method combines a genetic algorithm and a forward model based on Lorenz-Mie theory, treating bispheres and quadspheres as projected area and volume-equivalent coated spheres. The inverse method was successfully validated with numerically predicted average absorption and scattering cross-sections of suspensions consisting of bispheres and quadspheres, with realistic size distributions, using the T-matrix method. It was able to retrieve the monomers' complex index of refraction with size parameter up to 11, relative refraction index less than 1.3, and absorption index less than 0.1. Then, the inverse method was applied to retrieve the effective spectral complex index of refraction of Synechocystis sp. approximated as randomly oriented aggregates consisting of two overlapping homogeneous spheres. Both the measured absorption cross-section and the retrieved absorption index featured peaks at 435 and 676 nm corresponding to chlorophyll a, a peak at 625 nm corresponding to phycocyanin, and a shoulder around 485 nm corresponding to carotenoids. These results can be used to optimize and control light transfer in photobioreactors. The inverse method and the equivalent coated sphere model could be applied to other optically soft particles of similar morphologies.

Measurement of emission cross sections for n = 3 → 2 transitions in Neon-like Fe XVII and Ni XIX ions

NASA Astrophysics Data System (ADS)

Lockard, Tom; Brown, Gregory V.; Hell, Natalie; Scofield, J. H.; Beiersdorfer, Peter; Porter, Frederick Scott; Kilbourne, Caroline; Kelley, Richard L.; Leutenegger, Maurice A.; Betancourt-Martinez, Gabriele

2018-06-01

The absolute excitation cross sections of the strong 1s2 2s2 2p51/2 3d3/2 1P1 → 1s2 2s2 2p6 1S0 and 1s2 2s2 2p53/2 3d5/2 3D1 → 1s2 2s2 2p6 1S0 strong resonance and intercombination lines, commonly known as 3C and 3D, have been measured in neon-like Fe16+ and Ni18+. These measurements were carried out at the Lawrence Livermore National Laboratory's EBIT-I electron beam ion trap facility using the EBIT Calorimeter Spectrometer (ECS) quantum microcalorimeter and a flat crystal spectrometer. The absolute excitation cross sections were determined by normalizing the measured spectrum to the X-ray emission from radiative recombination. The direct excitation lines 3C and 3D and radiative recombination (RR) lines were measured simultaneously using the ECS. By normalizing the measured RR flux to their theoretical cross sections, the emission from lines 3C and 3D was made absolute. Using simultaneous measurements from the higher resolution flat crystal spectrometer, it was possible to check for potential blends from lower charge states. Results of our measurements including comparison to theory, will be presented.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Thermal neutron capture cross section for 56Fe(n ,γ )

NASA Astrophysics Data System (ADS)

Firestone, R. B.; Belgya, T.; Krtička, M.; Bečvář, F.; Szentmikloṡi, L.; Tomandl, I.

2017-01-01

The 56Fe(n ,γ ) thermal neutron capture cross section and the 57Fe level scheme populated by this reaction have been investigated in this work. Singles γ -ray spectra were measured with an isotopically enriched 56Fe target using the guided cold neutron beam at the Budapest Reactor, and γ γ -coincidence data were measured with a natural Fe target at the LWR-15 research reactor in Řež, Czech Republic. A detailed level scheme consisting of 448 γ rays populating/depopulating 97 levels and the capture state in 57Fe has been constructed, and ≈99 % of the total transition intensity has been placed. The transition probability of the 352-keV γ ray was determined to be Pγ(352 ) =11.90 ±0.07 per 100 neutron captures. The 57Fe level scheme is substantially revised from earlier work and ≈33 previously assigned levels could not be confirmed while a comparable number of new levels were added. The 57Feγ -ray cross sections were internally calibrated with respect to 1H and 32Sγ -ray cross section standards using iron(III) acetylacetonate (C15H21FeO6) and iron pyrite (FeS2) targets. The thermal neutron cross section for production of the 352-keV γ -ray cross section was determined to be σγ(352 ) =0.2849 ±0.015 b. The total 56Fe(n ,γ ) thermal radiative neutron cross section is derived from the 352-keV γ -ray cross section and transition probability as σ0=2.394 ±0.019 b. A least-squares fit of the γ rays to the level scheme gives the 57Fe neutron separation energy Sn=7646.183 ±0.018 keV.

Cross section measurements of radiative KL2,3 RRS in 24Cr and L3M4,5 RRS in 59Pr for Mn Kα1,2 X-rays

NASA Astrophysics Data System (ADS)

Sharma, Veena; Upmanyu, Arun; Singh, Ranjit; Singh, Gurjot; Sharma, Hitesh; Kumar, Sanjeev; Mehta, D.

2017-06-01

The KL2,3 and L3M4,5 radiative resonant Raman scattering (RRS) cross sections have been measured for the quasimonochromatic Mn Kα1,2 X-rays (5.895 keV) in 24Cr (K-shell level width (ΓK) =1.08 eV) and 59 Pr (L3-subshell level width (ΓL3) =3.60 eV), respectively, using targets in metallic and various chemical forms. The incident Mn Kα1,2 X-ray energy is lower than the K-shell binding energy of 24Cr and L3-subshell binding energy of 59Pr by 94 ΓK (Cr) and 94 ΓL3 (Pr), respectively. The experimental measurements were performed with a low energy Ge detector (LEGe) and a radioactive 55Fe annular source in conjunction with 24Cr absorber. The measured cross section values for the 24Cr and 59 Pr elements in their various oxidation states are found to be same within experimental errors. The measurements were further extended to investigate alignment of the intermediate L3-subshell (J =3/2) virtual vacancy states in 59Pr through angular distribution measurements for RRS photon emission, which is found to be isotropic within experimental errors.

Cross sections for the reactions e + e - → K S 0 K L 0 π 0 , K S 0 K L 0 η , and K S 0 K L 0 π 0 π 0 from events with initial-state radiation

DOE PAGES

Lees, J. P.; Poireau, V.; Tisserand, V.; ...

2017-03-06

Here, we study the processes e + e - → Kmore » $$0\\atop{S}$$ K$$0\\atop{L}$$ π 0 γ , K $$0\\atop{S}$$ K$$0\\atop{L}$$ η γ , and K$$0\\atop{S}$$ K$$0\\atop{L}$$ π 0 π 0 γ , where the photon is radiated from the initial state, providing cross section measurements for the hadronic final states over a continuum of center-of-mass energies. The results are based on 469 fb -1 of data collected at or near the Υ ( 4 S ) resonance with the BABAR detector at SLAC. We present the first measurements of the e + e - → K$$0\\atop{S}$$ K$$0\\atop{L}$$ π 0 , K$$0\\atop{S}$$ K$$0\\atop{L}$$ η , and K$$0\\atop{S}$$ K$$0\\atop{L}$$ π 0π 0 cross sections up to a center-of-mass energy of 4 GeV and study their intermediate resonance structures. We observe J / ψ decays to all of these final states for the first time, present measurements of their J / ψ branching fractions, and search for ψ (2S) decays.« less

The electronic states of cyclopropane studied by VUV absorption and electron energy-loss spectroscopies

NASA Astrophysics Data System (ADS)

Gingell, M.; Mason, N. J.; Walker, I. C.; Marston, G.; Zhao, H.; Siggel, M. R. F.

1999-06-01

Absolute optical (VUV) absorption cross sections for cyclopropane have been measured from 5.0 to 11.2 and 20-40 eV using synchrotron radiation. Also, electron energy-loss (EEL) spectra have been obtained using incident electrons of (a) 150 eV energy scattered through small angles (energy loss 5.0-15 eV) and (b) near-threshold energies scattered through large angles (energy loss 0-10.5 eV). Taken together these confirm that the low-lying excited electronic states of cyclopropane are of Rydberg type and, although spectral bands are diffuse, a known Rydberg series has been extended. Recent computations (Galasso V 1996 Chem. Phys. 206 289) appear to give a good account of the experimental spectrum from threshold to about 11 eV, but these must be extended if valence-excited states are to be characterized. Particular attention has been directed at the evaluation of absolute optical cross sections. These are now believed to be established over the energy ranges 5-15 and 20-40 eV. In the gap region (15-20 eV) second-order radiation may affect the optical measurements. From consideration of second-order effects, and comparison of the present studies with earlier measurements, we propose a best-estimate cross section in this energy region also.

Cross sections for the reactions e + e - → K S 0 K L 0 π 0 , K S 0 K L 0 η , and K S 0 K L 0 π 0 π 0 from events with initial-state radiation

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

Lees, J. P.; Poireau, V.; Tisserand, V.

Here, we study the processes e + e - → Kmore » $$0\\atop{S}$$ K$$0\\atop{L}$$ π 0 γ , K $$0\\atop{S}$$ K$$0\\atop{L}$$ η γ , and K$$0\\atop{S}$$ K$$0\\atop{L}$$ π 0 π 0 γ , where the photon is radiated from the initial state, providing cross section measurements for the hadronic final states over a continuum of center-of-mass energies. The results are based on 469 fb -1 of data collected at or near the Υ ( 4 S ) resonance with the BABAR detector at SLAC. We present the first measurements of the e + e - → K$$0\\atop{S}$$ K$$0\\atop{L}$$ π 0 , K$$0\\atop{S}$$ K$$0\\atop{L}$$ η , and K$$0\\atop{S}$$ K$$0\\atop{L}$$ π 0π 0 cross sections up to a center-of-mass energy of 4 GeV and study their intermediate resonance structures. We observe J / ψ decays to all of these final states for the first time, present measurements of their J / ψ branching fractions, and search for ψ (2S) decays.« less

Amendments to (63)Ni production calculation for Hiroshima by Takamiya et al. and DS02 fluence data by Egbert et al.

PubMed

Takamiya, K; Imanaka, T; Egbert, S D; Rühm, W

2011-05-01

In a previous paper, Takamiya et al. calculated (63)Ni production in copper samples exposed to the Hiroshima atomic bomb. More specifically, they used their experimental cross-section values of the (63)Cu(n,p)(63)Ni reaction and compared the result with that of the corresponding calculation in the radiation dosimetry system DS02, which used another set of cross-section values. These results were different, and the following two reasons were found: typographical errors in several energy boundary values in the DS02 report that was also used in the calculation by Takamiya et al. and an inappropriate assumption on the cross-section values of the low neutron energy region in the calculation by Takamiya et al. These two issues are described and amended in the present report.

MSG-7: Molecular absorption processes related to the penetration of ultraviolet solar radiation into the middle atmosphere

NASA Technical Reports Server (NTRS)

Frederick, J. E.; Blake, A. J.; Freeman, D. E.; Nicholls, R. W.; Ogawa, T.; Simon, P. C.

1983-01-01

The information presently available on the absorption cross sections of O2 and O3 with attention to the application of these data in middle atmospheric science is reviewed. The cross sections values reported by different groups are intercompared in tabular form where feasible, and specific values are recommended when there is a basis for preferring a particular set of results over other available data. When no such basis exists, the differences among published cross sections then serve to indicate a range of uncertainty. In these cases the need for additional work is indicated. Specific topics addressed are the absorption of molecular oxygen at Lyman alpha, in the Schumann-Runge continuum, in the Schumann-Runge bands, and in the Herzberg continuum. For ozone, the Hartley and Huggins bands are considered.

Investigation of the collision line broadening problem as applicable to the NASA Optical Plume Anomaly Detection (OPAD) system, phase 1

NASA Astrophysics Data System (ADS)

Dean, Timothy C.; Ventrice, Carl A.

1995-05-01

As a final report for phase 1 of the project, the researchers are submitting to the Tennessee Tech Office of Research the following two papers (reprinted in this report): 'Collision Line Broadening Effects on Spectrometric Data from the Optical Plume Anomaly System (OPAD),' presented at the 30th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, 27-29 June 1994, and 'Calculation of Collision Cross Sections for Atomic Line Broadening in the Plume of the Space Shuttle Main Engine (SSME),' presented at the IEEE Southeastcon '95, 26-29 March 1995. These papers fully state the problem and the progress made up to the end of NASA Fiscal Year 1994. The NASA OPAD system was devised to predict concentrations of anomalous species in the plume of the Space Shuttle Main Engine (SSME) through analysis of spectrometric data. The self absorption of the radiation of these plume anomalies is highly dependent on the line shape of the atomic transition of interest. The Collision Line Broadening paper discusses the methods used to predict line shapes of atomic transitions in the environment of a rocket plume. The Voigt profile is used as the line shape factor since both Doppler and collisional line broadening are significant. Methods used to determine the collisional cross sections are discussed and the results are given and compared with experimental data. These collisional cross sections are then incorporated into the current self absorbing radiative model and the predicted spectrum is compared to actual spectral data collected from the Stennis Space Center Diagnostic Test Facility rocket engine. The second paper included in this report investigates an analytical method for determining the cross sections for collision line broadening by molecular perturbers, using effective central force interaction potentials. These cross sections are determined for several atomic species with H2, one of the principal constituents of the SSME plume environment, and compared with experimental data.

Improvement and Analysis of the Radiation Response of RADFET Dosimeters

DTIC Science & Technology

1992-06-15

TLD ), silicon p-i-n diode responses and silicon calorimetry (AWE Dosimetry Service). Intensive preparations were made by REM and the experiments were...SUB-GROUP dose: RADFET : tactical dosimetry silicon : metal-oxide- 0705 emiconductor (MOS) field effect transistor (FET) : silicon Idioxide space...1.1 Principle of a dosimetry system, based on the RADFET (radiation-sensitive field-effect transistor) (a) microscopic cross-section of chip (b) chip

Radiological health risks for exploratory class missions in space

NASA Technical Reports Server (NTRS)

Nachtwey, D. Stuart; Yang, Tracy Chui-Hsu

1991-01-01

The radiation risks to crewmembers on missions to the moon and Mars are studied. A graph is presented of the cross section as a function of linear energy transfer (LET) for cell inactivation and neoplastic cell transformation. Alternatives to conventional approaches to radiation protection using dose and Q are presented with attention given to a hybrid of the conventional system for particles with LET less than 100 keV/micron.

Pion Production Data Needed for Space Radiation

NASA Technical Reports Server (NTRS)

Norbury, John W.

2010-01-01

A recent discovery concerning the importance of hadron production in space radiation is that pions can contribute up to twenty percent of the dose from galactic cosmic ray interactions (S. Aghara, S. Blattnig, J. Norbury, R. Singleterry, Nuclear Instruments and Methods, Vol. 267, 2009, p. 1115). Although the contribution for dose equivalent will be smaller, the dose contribution could be important for fluence based radiation models. Pion production cross sections will be an essential ingredient to such models, and it is of interest to investigate the adequacy of the pion production experimental data base for energies relevant to space radiation. The pion production threshold in nucleon - nucleon reactions is at 280 MeV and, in an interesting accident of nature, this lies near the peak of the galactic cosmic ray proton spectrum. Therefore, pion production data are needed from threshold up to energies around 50 GeV/nucleon, where the galactic cosmic ray fluence is of decreasing importance. Total and differential cross section data for pion production in this energy range will be reviewed. The availability and accuracy of theoretical models will also be discussed. It will be shown that there are a significant lack of data in this important energy range and that theoretical models still need improvement.

Modeling thermal infrared (2-14 micrometer) reflectance spectra of frost and snow

NASA Technical Reports Server (NTRS)

Wald, Andrew E.

1994-01-01

Existing theories of radiative transfer in close-packed media assume that each particle scatters independently of its neighbors. For opaque particles, such as are common in the thermal infrared, this assumption is not valid, and these radiative transfer theories will not be accurate. A new method is proposed, called 'diffraction subtraction', which modifies the scattering cross section of close-packed large, opaque spheres to account for the effect of close packing on the diffraction cross section of a scattering particle. This method predicts the thermal infrared reflectance of coarse (greater than 50 micrometers radius), disaggregated granular snow. However, such coarse snow is typically old and metamorphosed, with adjacent grains welded together. The reflectance of such a welded block can be described as partly Fresnel in nature and cannot be predicted using Mie inputs to radiative transfer theory. Owing to the high absorption coefficient of ice in the thermal infrared, a rough surface reflectance model can be used to calculate reflectance from such a block. For very small (less than 50 micrometers), disaggregated particles, it is incorrect in principle to treat diffraction independently of reflection and refraction, and the theory fails. However, for particles larger than 50 micrometers, independent scattering is a valid assumption, and standard radiative transfer theory works.

Calculation of tubular radiators of the automobile type

NASA Technical Reports Server (NTRS)

Richter, L

1926-01-01

We propose to show how to calculate the cooling capacity of all radiators through which the air flows in separate treamlets, whether enclosed in actual tubes or not and whatever cross-sectional shape the tubes may have. The first part will give the fundamental principles for calculating velocity of air in the tubes and the heat exchange by radiation, conduction and convection, and show, by examples, the agreement of the calculation with experiments. In the second part, the effect of the dimensions and conditions of operation on the heat exchange will be systematically investigated.

Computational chemistry and aeroassisted orbital transfer vehicles

NASA Technical Reports Server (NTRS)

Cooper, D. M.; Jaffe, R. L.; Arnold, J. O.

1985-01-01

An analysis of the radiative heating phenomena encountered during a typical aeroassisted orbital transfer vehicle (AOTV) trajectory was made to determine the potential impact of computational chemistry on AOTV design technology. Both equilibrium and nonequilibrium radiation mechanisms were considered. This analysis showed that computational chemistry can be used to predict (1) radiative intensity factors and spectroscopic data; (2) the excitation rates of both atoms and molecules; (3) high-temperature reaction rate constants for metathesis and charge exchange reactions; (4) particle ionization and neutralization rates and cross sections; and (5) spectral line widths.

Hadronic vacuum polarization and e+e- → μ+μ- cross section: Reanalysis with new precise data for σh with 4π final states included

NASA Astrophysics Data System (ADS)

Sauli, Vladimir

2018-05-01

The interference effect between leptonic radiative corrections and hadronic polarization functions is calculated via optical theorem for μ-pair production in vicinity of narrow resonances. Within seven most dominant exclusive channels of the production cross section σh(e+e- → hadrons) one achieves high acuracy which is necessary for the comparison with experiments. The result is compared with KLOE and KLOE2 experiments for μ-μ+ and μ-μ+γ productions at φ and ω/ρ meson energy.

Higgs-differential cross section at NNLO in dimensional regularisation

DOE PAGES

Dulat, Falko; Lionetti, Simone; Mistlberger, Bernhard; ...

2017-07-05

We present an analytic computation of the Higgs production cross section in the gluon fusion channel, which is differential in the components of the Higgs momentum and inclusive in the associated partonic radiation through NNLO in perturbative QCD. Our computation includes the necessary higher order terms in the dimensional regulator beyond the finite part that are required for renormalisation and collinear factorisation at N 3LO. We outline in detail the computational methods which we employ. We present numerical predictions for realistic final state observables, specifically distributions for the decay products of the Higgs boson in the γγ decay channel.

A new multigroup method for cross-sections that vary rapidly in energy

DOE PAGES

Haut, Terry Scot; Ahrens, Cory D.; Jonko, Alexandra; ...

2016-11-04

Here, we present a numerical method for solving the time-independent thermal radiative transfer (TRT) equation or the neutron transport (NT) equation when the opacity (cross-section) varies rapidly in frequency (energy) on the microscale ε; ε corresponds to the characteristic spacing between absorption lines or resonances, and is much smaller than the macroscopic frequency (energy) variation of interest. The approach is based on a rigorous homogenization of the TRT/NT equation in the frequency (energy) variable. Discretization of the homogenized TRT/NT equation results in a multigroup-type system, and can therefore be solved by standard methods.

Radiation and ionization energy loss simulation for the GDH sum rule experiment in Hall-A at Jefferson Lab

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

Yan, Xin -Hu; Ye, Yun -Xiu; Chen, Jian -Ping

2015-07-17

The radiation and ionization energy loss are presented for single arm Monte Carlo simulation for the GDH sum rule experiment in Hall-A at Jefferson Lab. Radiation and ionization energy loss are discussed formore » $$^{12}C$$ elastic scattering simulation. The relative momentum ratio $$\\frac{\\Delta p}{p}$$ and $$^{12}C$$ elastic cross section are compared without and with radiation energy loss and a reasonable shape is obtained by the simulation. The total energy loss distribution is obtained, showing a Landau shape for $$^{12}C$$ elastic scattering. This simulation work will give good support for radiation correction analysis of the GDH sum rule experiment.« less

Fluctuation of a Piston in Vacuum Induced by Thermal Radiation Pressure

NASA Astrophysics Data System (ADS)

Inui, Norio

2017-10-01

We consider the displacement of a piston dividing a vacuum cavity at a finite temperature T induced by fluctuations in the thermal radiation pressure. The correlation function of the thermal radiation pressure is calculated using the theoretical framework developed by Barton, which was first applied to the fluctuation of the Casimir force at absolute zero. We show that the variance of the radiation pressure at a fixed point is proportional to T8 and evaluate the mean square displacement for a piston with a small cross section in a characteristic correlation timescale ħ/(kBT). At room temperature, the contribution of the thermal radiation to the fluctuation is larger than that of the vacuum fluctuation.

Experimental study of the energy dependence of the total cross section for the 6He + natSi and 9Li + natSi reactions

NASA Astrophysics Data System (ADS)

Sobolev, Yu. G.; Penionzhkevich, Yu. E.; Aznabaev, D.; Zemlyanaya, E. V.; Ivanov, M. P.; Kabdrakhimova, G. D.; Kabyshev, A. M.; Knyazev, A. G.; Kugler, A.; Lashmanov, N. A.; Lukyanov, K. V.; Maj, A.; Maslov, V. A.; Mendibayev, K.; Skobelev, N. K.; Slepnev, R. S.; Smirnov, V. V.; Testov, D.

2017-11-01

New experimental measurements of the total reaction cross sections for the 6He + natSi and 9Li + natSi processes in the energy range of 5 to 40 A MeV are presented. A modified transmission method based on high-efficiency detection of prompt n-γ radiation has been used in the experiment. A bump is observed for the first time in the energy dependence σR( E) at E ˜ 10-30 A MeV for the 9Li + natSi reaction, and existence of the bump in σR( E) at E ˜ 10-20 A MeV first observed in the standard transmission experiments is experimentally confirmed for the 6He + natSi reaction. Theoretical analysis of the measured 6He + natSi and 9Li + natSi reaction cross sections is performed within the microscopic double folding model. Disagreement is observed between the experimental and theoretical cross sections in the region of the bump at the energies of 10 to 20 A MeV, which requires further study.

Optical nonlinearities of colloidal InP@ZnS core-shell quantum dots probed by Z-scan and two-photon excited emission

NASA Astrophysics Data System (ADS)

Wawrzynczyk, Dominika; Szeremeta, Janusz; Samoc, Marek; Nyk, Marcin

2015-11-01

Spectrally resolved nonlinear optical properties of colloidal InP@ZnS core-shell quantum dots of various sizes were investigated with the Z-scan technique and two-photon fluorescence excitation method using a femtosecond laser system tunable in the range from 750 nm to 1600 nm. In principle, both techniques should provide comparable results and can be interchangeably used for determination of the nonlinear optical absorption parameters, finding maximal values of the cross sections and optimizing them. We have observed slight differences between the two-photon absorption cross sections measured by the two techniques and attributed them to the presence of non-radiative paths of absorption or relaxation. The most significant value of two-photon absorption cross section σ2 for 4.3 nm size InP@ZnS quantum dot was equal to 2200 GM, while the two-photon excitation action cross section σ2Φ was found to be 682 GM at 880 nm. The properties of these cadmium-free colloidal quantum dots can be potentially useful for nonlinear bioimaging.

Fundamentals of Radiation Dosimetry

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

Bos, Adrie J. J.

The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuringmore » the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.« less

Neutron capture cross-section measurements for 238U between 0.4 and 1.4 MeV

NASA Astrophysics Data System (ADS)

Krishichayan, Fnu; Finch, S. W.; Howell, C. R.; Tonchev, A. P.; Tornow, W.

2017-09-01

Neutron-induced radiative-capture cross-section data of 238U are crucial for fundamental nuclear physics as well as for Stewardship Science, for advanced-fuel-cycle calculations, and for nuclear astrophysics. Based on different techniques, there are a large number of 238U(n, γ) 239U cross-section data available in the literature. However, there is a lack of systematic and consistent measurements in the 0.1 to 3.0 MeV energy range. The goal of the neutron-capture project at TUNL is to provide accurate 238U(n, γ) 239U cross-section data in this energy range. The 238U samples, sandwiched between gold foils of the same size, were irradiated for 8-14 hours with monoenergetic neutrons. To avoid any contribution from thermal neutrons, the 238U and 197Au targets were placed inside of a thin-walled pill-box made of 238U. Finally, the whole pill-box was wrapped in a gold foil as well. After irradiation, the samples were gamma-counted at the TUNL's low-background counting facility using high-efficient HPGe detectors. The 197Au monitor foils were used to calculate the neutron flux. The experimental technique and 238U(n, γ) 239U cross-section results at 6 energies will be discussed during the meeting.

Scattering of Electromagnetic Radiation by ITO Nanoparticles with Various Doping Levels

NASA Astrophysics Data System (ADS)

Bugaev, A. S.; Astapenko, V. A.; Manuilovich, E. S.; Sakhno, S. V.; Khramov, E. S.; Yakovets, A. V.

2018-02-01

The process of scattering of radiation by indium‒tin oxide (ITO) nanoparticles is theoretically studied at various degrees of doping and for different radii of nanoparticles. Qualitative conclusions are made about the character of the dependence of the scattering cross section on the frequency with variation of the particle size and the percentage content of tin. The prospects of using ITO nanoparticles as an active substance in optical sensors are estimated.

Absorption and radiation of nonminimally coupled scalar field from charged BTZ black hole

NASA Astrophysics Data System (ADS)

Huang, Lu; Chen, Juhua; Wang, Yongjiu

2018-06-01

In this paper we investigate the absorption and radiation of nonminimally coupled scalar field from the charged BTZ black hole. We find the analytical expressions for the reflection coefficient, the absorption cross section and the decay rate in strong coupling case. We find that the reflection coefficient is directly governed by Hawking temperature TH, scalar wave frequency ω , Bekenstein-Hawking entropy S_{BH}, angular momentum m and coupling constant ξ.

Self-consistent models for Coulomb heated X-ray pulsar atmospheres

NASA Technical Reports Server (NTRS)

Harding, A.; Meszaros, S. P.; Kirk, J.; Galloway, D.

1983-01-01

Calculations of accreting magnetized neutron star atmospheres heated by the gradual deceleration of protons via Coulomb collisions are presented. Self consistent determinations of the temperature and density structure for different accretion rates are made by assuming hydrostatic equilibrium and energy balance, coupled with radiative transfer. The full radiative transfer in two polarizations, using magnetic cross sections but with cyclotron resonance effects treated approximately, is carried out in the inhomogeneous atmospheres.

Algorithm for Surface of Translation Attached Radiators (A-STAR). Volume 2. Users manual

NASA Astrophysics Data System (ADS)

Medgyesimitschang, L. N.; Putnam, J. M.

1982-05-01

A hierarchy of computer programs implementing the method of moments for bodies of translation (MM/BOT) is described. The algorithm treats the far-field radiation from off-surface and aperture antennas on finite-length open or closed bodies of arbitrary cross section. The near fields and antenna coupling on such bodies are computed. The theoretical development underlying the algorithm is described in Volume 1 of this report.

Evaluation of proton cross-sections for radiation sources in the proton accelerator

NASA Astrophysics Data System (ADS)

Cho, Young-Sik; Lee, Cheol-Woo; Lee, Young-Ouk

2007-08-01

Proton Engineering Frontier Project (PEFP) is currently building a proton accelerator in Korea which consists of a proton linear accelerator with 100 MeV of energy, 20 mA of current and various particle beam facilities. The final goal of this project consists of the production of 1 GeV proton beams, which will be used for various medical and industrial applications as well as for research in basic and applied sciences. Carbon and copper in the proton accelerator for PEPP, through activation, become radionuclides such as 7Be and 64Cu. Copper is a major element of the accelerator components and the carbon is planned to be used as a target material of the beam dump. A recent survey showed that the currently available cross-sections create a large difference from the experimental data in the production of some residual nuclides by the proton-induced reactions for carbon and copper. To more accurately estimate the production of radioactive nuclides in the accelerator, proton cross-sections for carbon and copper are evaluated. The TALYS code was used for the evaluation of the cross-sections for the proton-induced reactions. To obtain the cross-sections which best fits the experimental data, optical model parameters for the neutron, proton and other complex particles such as the deuteron and alpha were successively adjusted. The evaluated cross-sections in this study are compared with the measurements and other evaluations .

Evaluation of the radiation hazard for ion-beam analysis with MeV external proton beams (X-IBA)

NASA Astrophysics Data System (ADS)

Hofsäss, Hans

2018-07-01

MeV ion beams which are extracted into air or He atmosphere are used in many labs for proton-induced X-ray emission (PIXE), proton induced gamma ray emission (PIGE) or Rutherford backscattering (RBS) to analyze samples which are difficult or impossible to handle in vacuum. When MeV proton beams are extracted into air through thin Kapton foils or nowadays thin silicon nitride membranes, the protons will interact with air, as well as elements present in the analyzed samples. Typically the range of MeV protons in air is several cm, in Helium atmosphere several 10 cm and in human skin around 100 μm. Besides the severe radiation hazard in case of a direct exposure of skin with protons, there are a manifold of nuclear reactions or inelastic proton scattering processes which may cause activation of air and target materials but also prompt radiation. The radiation hazard associated with the direct and scattered beam, nuclear reaction products and radionuclide production in air have been discussed in a publication by Doyle et al. in 1991 which was used as a reference in several later publications. I have reevaluated the radiation hazards for external proton beams with up to 4.5 MeV using proton reaction cross sections taken from the JANIS book of proton induced cross sections. The radionuclide production in air is about 3 orders of magnitude lower compared to values given in the 1991 publication. Radionuclide production as well as generation of prompt alpha, gamma and neutron radiation in target materials for elements up to molybdenum is also evaluated.

A cross-sectional study examining the correlation between sunless tanning product use and tanning beliefs and behaviors.

PubMed

Sahn, Rachel E; McIlwain, Mary Jayne; Magee, Kristin H; Veledar, Emir; Chen, Suephy C

2012-04-01

To establish the effect of sunless tanning products on tanning behaviors and to determine characteristics of sunless tanning product users. A cross-sectional survey study conducted between May 30, 2007, and December 4, 2007. The Emory University campus and surrounding locations in Atlanta, Georgia. Four hundred fifteen community and university-affiliated women. Self-reported use of sunless tanning products and UV radiation tanning methods. Forty-eight percent of participants had used sunless tanning products, 70.6% had tanned in the sun, and 26.0% had used tanning beds at least once in the past year. Most participants (92.7%) believed that tanned skin is more attractive than untanned skin, and 79.2% reported feeling better about themselves when tan. Many sunless tanning product users reported decreased frequency of tanning in the sun (36.8%) or in tanning beds (38%) because of product use. Frequent users were more likely to have decreased their UV radiation exposure. Lighter complexion, frequent use of UV radiation tanning methods, feeling better about oneself when tan, and having a history of skin cancer were independently associated with sunless tanning product use. The desire for tanned skin remains strong despite growing awareness of the dangers of UV radiation exposure. In some women, sunless tanning product use is associated with decreased UV radiation tanning frequency, especially in women who use them repeatedly. Improvements in the appearance of sunless tanning product tans may allow wider acceptance by the public and further decreases in UV radiation tanning practices.

Description of Differential Cross Sections for 63Cu + p Nuclear Reactions Induced by High-Energy Cosmic-Ray Protons

NASA Astrophysics Data System (ADS)

Chuvilskaya, T. V.; Shirokova, A. A.

2018-03-01

The results of calculation of 63Cu + p differential cross sections at incident-proton energies between 10 and 200 MeV and a comparative analysis of these results are presented as a continuation of the earlier work of our group on developing methods for calculating the contribution of nuclear reactions to radiative effects arising in the onboard spacecraft electronics under the action of high-energy cosmic-ray protons on 63Cu nuclei (generation of single-event upsets) and as a supplement to the earlier calculations performed on the basis of the TALYS code in order to determine elastic- and inelastic-scattering cross sections and charge, mass, and energy distributions of recoil nuclei (heavy products of the 63Cu + p nuclear reaction). The influence of various mechanisms of the angular distributions of particles emitted in the 63Cu + p nuclear reaction is also discussed.

Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region

NASA Technical Reports Server (NTRS)

Xia, T. J.; Chien, T. S.; Wu, C. Y. Robert; Judge, D. L.

1991-01-01

Using synchrotron radiation as a continuum light source, the photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 have been measured from their respective ionization thresholds to 1060 A. The vibrational constants associated with the nu(2) totally symmetric, out-of-plane bending vibration of the ground electronic state of PH3(+) have been obtained. The cross sections and quantum yields for producing neutral products through photoexcitation of these molecules in the given spectral regions have also been determined. In the present work, autoionization processes were found to be less important than dissociation and predissociation processes in NH3, PH3, and C2H4. Several experimental techniques have been employed in order to examine the various possible systematic errors critically.

Magnetic field effect on photoionization cross-section of hydrogen-like impurity in cylindrical quantum wire

NASA Astrophysics Data System (ADS)

Mughnetsyan, V. N.; Barseghyan, M. G.; Kirakosyan, A. A.

2008-01-01

We consider the photoionization of a hydrogen-like impurity centre in a quantum wire approximated by a cylindrical well of finite depth in a magnetic field directed along the wire axis. The ground state energy and the wave function of the electron localized on on-axis impurity centre are calculated using the variational method. The wave functions and energies of the final states in an one-dimensional conduction subband are also presented. The dependences of photoionization cross-section of a donor centre on magnetic field and frequency of incident radiation both for parallel and perpendicular polarizations and corresponding selection rules for the allowed transitions are found in the dipole approximation. The estimates of photoionization cross-section for various values of wire radius and magnetic field induction for GaAs quantum wire embedded in Ga 1-xAl 1-xAs matrix are given.

Radiation damage annealing mechanisms and possible low temperature annealing in silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.

1980-01-01

The defect responsible for reverse annealing in 2 ohm/cm n(+)/p silicon solar cells was identified. This defect, with energy level at e sub v + 0.30 eV was tentatively identified as a boron oxygen-vacancy complex. Results indicate that its removal could result in significant annealing for 2 ohm/cm and lower resistivity cells at temperatures as low as 200 C. These results were obtained by use of an expression derived from the Shockley-Read-Hall recombination theory which relates measured diffusion length ratios to relative defect concentrations and electron capture cross sections. The relative defect concentrations and one of the required capture cross sections are obtained from Deep Level Transient Spectroscopy. Four additional capture cross sections are obtained using diffusion length data and data from temperature dependent lifetime studied. These calculated results are in reasonable agreement with experimental data.

MSG-7: molecular absorption processes related to the penetration of ultraviolet solar radiation into the middle atmosphere

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

Frederick, J.E.; Blake, A.J.; Freeman, D.E.

1983-07-01

The information presently available on the absorption cross sections of O2 and O3 with attention to the application of these data in middle atmospheric science is reviewed. The cross sections values reported by different groups are intercompared in tabular form where feasible, and specific values are recommended when there is a basis for preferring a particular set of results over other available data. When no such basis exists, the differences among published cross sections then serve to indicate a range of uncertainty. In these cases the need for additional work is indicated. Specific topics addressed are the absorption of molecularmore » oxygen at Lyman alpha, in the Schumann-Runge continuum, in the Schumann-Runge bands, and in the Herzberg continuum. For ozone, the Hartley and Huggins bands are considered.« less

[Experimental investigation of mechanisms of forming RbH by irradiating a Rb+H2 mixture with laser light].

PubMed

Shen, Xiao-Yan; Liu, Jing; Dai, Kang; Shen, Yi-Fan

2008-11-01

The radiation of a laser photoexcited Rb atoms from the ground state to the 5P3/2 level in a mixture of Rb vapor and hydrogen. The energy-pooling collision 5P3/2 + 5P3/2 --> 5S1/2 + 5D producted 5D state. The Rb (5P3/2) density and spatial distribution were mapped by monitoring the absorption of a counter-propagating laser beam, tuned to the 5P3/2 --> 7S1/2 transition, which could be translated parallel to the pump beam. In the presence of radiation trapping, the spontaneous radiation rate is multiplied by the transmission factor T5P3/2 --> 5S1/2, which describes the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed. The T5P3/2 --> 5S1/2 is related to the frequency dependent absorption cross section and the density and spatial distribution of atoms in the level of the transition. The effective radiative rates of the Rb D2 line as a function of the H2 pressure were obtained. These quantities were combined with the measured excited atom density and fluorescence ratio to yield absolute energy-pooling rate coefficient. The quenching collision Rb (5P3/2) + H2 (v = 0) --> Rb(5S) + H2 (v = 2) producted state H2 (v= 2). This process is at least 16 times faster than the Rb (5P3/2) radiative decay rate. The reverse process of this process is relatively unlikely due to their large translational energy defect. The cross section for the process H2 (v = 2) + H2 (v = 0) --> H2 (vn = 1) + H2 (v = 0) + 3 920.2 cm(-1) is 7.7 x 10(-19) cm2. Hence the relaxation rate of this vibrational level is relatively slow and the nuclear spin statistics is conserved. The H2 (v = 2) density was determined by using the cross section for Rb (5P3/2)-H2 quenching. RbH was fromed by the Rb(5D) + H2 and Rb (5P3/2) + H2 (v = 2) reactions and observed by laser absorption. The ratio of 5D --> 5P3/2 to 5P3/2 --> 5S1/2 fluorescence was measured as a function of the H2 density. The absorption of the laser beam tuned to the X1sigma+ --> A1sigma+ line of RbH was also measured as a function of the H2 density. From these measurements we obtained the cross section of 4.02 x 10(-7) cm2 for the process Rb (5D) + H2 --> RbH + H. The cross section for Rb (5P3/2) + H2 (upsilon = 2) --> RbH + H is 1.00 x 10(-8) cm2. This experiment showed that under our experimental conditions, RbH molecules are not created by a direct interaction of Rb(5P) with H2 but through a two-step reaction.

Proposed re-evaluation of the 154Eu thermal ( n, γ) capture cross-section based on spent fuel benchmarking studies

DOE PAGES

Skutnik, Steven E.

2016-09-22

154Eu is a nuclide of considerable importance to both non-destructive measurements of used nuclear fuel assembly burnup as well as for calculating the radiation source term for used fuel storage and transportation. But, recent evidence from code validation studies of spent fuel benchmarks have revealed evidence of a systemic bias in predicted 154Eu inventories when using ENDF/B-VII.0 and ENDF/B-VII.1 nuclear data libraries, wherein Eu-154 is consistently over-predicted on the order of 10% or more. Further, this bias is found to correlate with sample burnup, resulting in a larger departure from experimental measurements for higher sample burnups. Here, the bias in Eu-154 is characterized across eleven spent fuel destructive assay benchmarks from five different assemblies. Based on these studies, possible amendments to the ENDF/B-VII.0 and VII.1 evaluations of the 154Eu (n,γ) 155Eu are explored. By amending the location of the first resolved resonance for the 154Eu radiative capture cross-section (centered at 0.195 eV in ENDF/B-VII.0 and VII.1) to 0.188 eV and adjusting the neutron capture width proportional tomore » $$\\sqrt1/E$$, the amended cross-section evaluation was found to reduce the bias in predicted 154Eu inventories by approximately 5–7%. And while the amended capture cross-section still results in a residual over-prediction of 154Eu (ranging from 2% to 9%), the effect is substantially attenuated compared with the nominal ENDF/B-VII.0 and VII.1 evaluations.« less

Proposed re-evaluation of the 154Eu thermal ( n, γ) capture cross-section based on spent fuel benchmarking studies

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

Skutnik, Steven E.

154Eu is a nuclide of considerable importance to both non-destructive measurements of used nuclear fuel assembly burnup as well as for calculating the radiation source term for used fuel storage and transportation. But, recent evidence from code validation studies of spent fuel benchmarks have revealed evidence of a systemic bias in predicted 154Eu inventories when using ENDF/B-VII.0 and ENDF/B-VII.1 nuclear data libraries, wherein Eu-154 is consistently over-predicted on the order of 10% or more. Further, this bias is found to correlate with sample burnup, resulting in a larger departure from experimental measurements for higher sample burnups. Here, the bias in Eu-154 is characterized across eleven spent fuel destructive assay benchmarks from five different assemblies. Based on these studies, possible amendments to the ENDF/B-VII.0 and VII.1 evaluations of the 154Eu (n,γ) 155Eu are explored. By amending the location of the first resolved resonance for the 154Eu radiative capture cross-section (centered at 0.195 eV in ENDF/B-VII.0 and VII.1) to 0.188 eV and adjusting the neutron capture width proportional tomore » $$\\sqrt1/E$$, the amended cross-section evaluation was found to reduce the bias in predicted 154Eu inventories by approximately 5–7%. And while the amended capture cross-section still results in a residual over-prediction of 154Eu (ranging from 2% to 9%), the effect is substantially attenuated compared with the nominal ENDF/B-VII.0 and VII.1 evaluations.« less

Broadband measurements of aerosol extinction in the ultraviolet spectral region

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Flores, J. M.; Brock, C. A.; Brown, S. S.; Rudich, Y.

2013-04-01

Aerosols influence the Earth's radiative budget by scattering and absorbing incoming solar radiation. The optical properties of aerosols vary as a function of wavelength, but few measurements have reported the wavelength dependence of aerosol extinction cross sections and complex refractive indices. We describe a new laboratory instrument to measure aerosol optical extinction as a function of wavelength, using cavity enhanced spectroscopy with a broadband light source. The instrument consists of two broadband channels which span the 360-390 and 385-420 nm spectral regions using two light emitting diodes (LED) and a grating spectrometer with charge-coupled device (CCD) detector. We determined aerosol extinction cross sections and directly observed Mie scattering resonances for aerosols that are purely scattering (polystyrene latex spheres and ammonium sulfate), slightly absorbing (Suwannee River fulvic acid), and strongly absorbing (nigrosin dye). We describe an approach for retrieving refractive indices as a function of wavelength from the measured extinction cross sections over the 360-420 nm wavelength region. The retrieved refractive indices for PSL and ammonium sulfate agree within uncertainty with the literature values for this spectral region. The refractive index determined for nigrosin is 1.78 (± 0.03) + 0.19 (± 0.08)i at 360 nm and 1.63 (± 0.03) + 0.21 (± 0.05)i at 420 nm. The refractive index determined for Suwannee River fulvic acid is 1.71 (± 0.02) + 0.07 (± 0.06)i at 360 nm and 1.66 (± 0.02) + 0.06 (± 0.04)i at 420 nm. These laboratory results support the potential for a field instrument capable of determining ambient aerosol optical extinction, average aerosol extinction cross section, and complex refractive index as a function of wavelength.

Broadband measurements of aerosol extinction in the ultraviolet spectral region

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Flores, J. M.; Brock, C. A.; Brown, S. S.; Rudich, Y.

2013-01-01

Aerosols influence the Earth's radiative budget by scattering and absorbing incoming solar radiation. The optical properties of aerosols vary as a function of wavelength, but few measurements have reported the wavelength dependence of aerosol extinction cross-sections and complex refractive indices. We describe a new laboratory instrument to measure aerosol optical extinction as a function of wavelength, using cavity enhanced spectroscopy with a broadband light source. The instrument consists of two broadband channels which span the 360-390 and 385-420 nm spectral regions using two light emitting diodes (LED) and a grating spectrometer with charge-coupled device (CCD) detector. We determined aerosol extinction cross-sections and directly observed Mie scattering resonances for aerosols that are purely scattering (polystyrene latex spheres and ammonium sulfate), slightly absorbing (Suwannee River fulvic acid), and strongly absorbing (nigrosin dye). We describe an approach for retrieving refractive indices as a function of wavelength from the measured extinction cross-sections over the 360-420 nm wavelength region. The retrieved refractive indices for PSL and ammonium sulfate agree within uncertainty with literature values for this spectral region. The refractive index determined for nigrosin is 1.78 (±0.03) + 0.19 (±0.08) i at 360 nm and 1.53 (±0.03) + 0.21 (±0.05) i at 420 nm. The refractive index determined for Suwannee River fulvic acid is 1.71 (±0.02) + 0.07 (±0.06) i at 360 nm and 1.66 (±0.02) + 0.06 (±0.04) i at 420 nm. These laboratory results support the potential for a field instrument capable of determining ambient aerosol optical extinction, average aerosol extinction cross-section, and complex refractive index as a function of wavelength.

Radiation damage of biomolecules (RADAM) database development: current status

NASA Astrophysics Data System (ADS)

Denifl, S.; Garcia, G.; Huber, B. A.; Marinković, B. P.; Mason, N.; Postler, J.; Rabus, H.; Rixon, G.; Solov'yov, A. V.; Suraud, E.; Yakubovich, A. V.

2013-06-01

Ion beam therapy offers the possibility of excellent dose localization for treatment of malignant tumours, minimizing radiation damage in normal tissue, while maximizing cell killing within the tumour. However, as the underlying dependent physical, chemical and biological processes are too complex to treat them on a purely analytical level, most of our current and future understanding will rely on computer simulations, based on mathematical equations, algorithms and last, but not least, on the available atomic and molecular data. The viability of the simulated output and the success of any computer simulation will be determined by these data, which are treated as the input variables in each computer simulation performed. The radiation research community lacks a complete database for the cross sections of all the different processes involved in ion beam induced damage: ionization and excitation cross sections for ions with liquid water and biological molecules, all the possible electron - medium interactions, dielectric response data, electron attachment to biomolecules etc. In this paper we discuss current progress in the creation of such a database, outline the roadmap of the project and review plans for the exploitation of such a database in future simulations.

Hard X-ray quiescent emission in magnetars via resonant Compton upscattering

NASA Astrophysics Data System (ADS)

Baring, M. G.; Wadiasingh, Z.; Gonthier, P. L.; Harding, A. K.

2017-12-01

Non-thermal quiescent X-ray emission extending between 10 keV and around 150 keV has been seen in about 10 magnetars by RXTE, INTEGRAL, Suzaku, NuSTAR and Fermi-GBM. For inner magnetospheric models of such hard X-ray signals, inverse Compton scattering is anticipated to be the most efficient process for generating the continuum radiation, because the scattering cross section is resonant at the cyclotron frequency. We present hard X-ray upscattering spectra for uncooled monoenergetic relativistic electrons injected in inner regions of pulsar magnetospheres. These model spectra are integrated over bundles of closed field lines and obtained for different observing perspectives. The spectral turnover energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the turnovers inferred in magnetar hard X-ray tails. Electrons of higher energy still emit most of the radiation below around 1 MeV, except for quasi-equatorial emission locales for select pulse phases. Our spectral computations use a new state-of-the-art, spin-dependent formalism for the QED Compton scattering cross section in strong magnetic fields.

Infrared absorption cross-sections, radiative efficiency and global warming potential of HFC-43-10mee

NASA Astrophysics Data System (ADS)

Le Bris, Karine; DeZeeuw, Jasmine; Godin, Paul J.; Strong, Kimberly

2018-06-01

HFC-43-10mee (C5H2F10) is a substitute for CFC-113, HCFC-141b and methyl chloroform, as well as an alternative to perfluorocarbons with high radiative efficiencies. Recent observations have shown that the global mean tropospheric abundance of HFC-43-10mee has increased steadily from the 1990s to reach 0.211 ppt in 2012. To date, the emission of this compound is not regulated. The radiative efficiency (RE) of HFC-43-10mee has recently been re-evaluated at 0.42 W m-2 ppb-1, giving a 100-year time horizon global warming potential (GWP100) of 1650. However, the initial RE, from which the new values were derived, originated from an unpublished source. We calculated a new RE of 0.36 W m-2 ppb-1 and a GWP100 of 1410 from laboratory absorption cross-section spectra of a pure vapour of HFC-43-10mee. Acquisitions were performed in the 550-3500 cm-1 spectral range using Fourier transform spectroscopy. The results were compared with the broadened spectra from the Pacific Northwest National Laboratory (PNNL) database and with theoretical calculations using density functional theory.

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

NASA Astrophysics Data System (ADS)

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

2018-02-01

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

Extended optical theorem in isotropic solids and its application to the elastic radiation force

NASA Astrophysics Data System (ADS)

Leão-Neto, J. P.; Lopes, J. H.; Silva, G. T.

2017-04-01

In this article, we derive the extended optical theorem for the elastic-wave scattering by a spherical inclusion (with and without absorption) in a solid matrix. This theorem expresses the extinction cross-section, i.e., the time-averaged power extracted from the incoming beam per its intensity, regarding the partial-wave expansion coefficients of the incident and scattered waves. We also establish the connection between the optical theorem and the elastic radiation force by a plane wave in a linear and isotropic solid. We obtain the absorption, scattering, and extinction efficiencies (the corresponding power per characteristic incident intensity per sphere cross-section area) for a plane wave and a spherically focused beam. We discuss to which extent the radiation force theory for plane waves can be used to the focused beam case. Considering an iron sphere embedded in an aluminum matrix, we numerically compute the scattering and elastic radiation force efficiencies. The radiation force on a stainless steel sphere embedded in a tissue-like medium (soft solid) is also computed. In this case, resonances are observed in the force as a function of the sphere size parameter (the wavenumber times the sphere radius). Remarkably, the relative difference between our findings and previous lossless liquid models is about 100% in the long-wavelength limit. Regarding some applications, the obtained results have a direct impact on ultrasound-based elastography techniques and ultrasonic nondestructive testing, as well as implantable devices activated by ultrasound.

A new low-energy bremsstrahlung generator for GEANT4.

PubMed

Peralta, L; Rodrigues, P; Trindade, A; Pia, M G

2005-01-01

The 2BN bremsstrahlung cross section is a well-adapted distribution to describe the radiative processes at low-electron kinetic energy (E(k) < 500 keV). In this work a method to implement this distribution in a Monte Carlo generator is developed.

Transverse vetoes with rapidity cutoff in SCET

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

Hornig, Andrew; Kang, Daekyoung; Makris, Yiannis

We consider di-jet production in hadron collisions where a transverse veto is imposed on radiation for (pseudo-)rapidities in the central region only, where this central region is defined with rapidity cutoff. For the case where the transverse measurement (e.g., transverse energy or min p T for jet veto) is parametrically larger relative to the typical transverse momentum beyond the cutoff, the cross section is insensitive to the cutoff parameter and is factorized in terms of collinear and soft degrees of freedom. The virtuality for these degrees of freedom is set by the transverse measurement, as in typical transverse-momentum dependent observablesmore » such as Drell-Yan, Higgs production, and the event shape broadening. This paper focuses on the other region, where the typical transverse momentum below and beyond the cutoff is of similar size. In this region the rapidity cutoff further resolves soft radiation into (u)soft and soft-collinear radiation with different rapidities but identical virtuality. This gives rise to rapidity logarithms of the rapidity cutoff parameter which we resum using renormalization group methods. We factorize the cross section in this region in terms of soft and collinear functions in the framework of soft-collinear effective theory, then further refactorize the soft function as a convolution of the (u)soft and soft-collinear functions. All these functions are calculated at one-loop order. As an example, we calculate a differential cross section for a specific partonic channel, qq ' → qq ' , for the jet shape angularities and show that the refactorization allows us to resum the rapidity logarithms and significantly reduce theoretical uncertainties in the jet shape spectrum.« less

Transverse vetoes with rapidity cutoff in SCET

DOE PAGES

Hornig, Andrew; Kang, Daekyoung; Makris, Yiannis; ...

2017-12-11

We consider di-jet production in hadron collisions where a transverse veto is imposed on radiation for (pseudo-)rapidities in the central region only, where this central region is defined with rapidity cutoff. For the case where the transverse measurement (e.g., transverse energy or min p T for jet veto) is parametrically larger relative to the typical transverse momentum beyond the cutoff, the cross section is insensitive to the cutoff parameter and is factorized in terms of collinear and soft degrees of freedom. The virtuality for these degrees of freedom is set by the transverse measurement, as in typical transverse-momentum dependent observablesmore » such as Drell-Yan, Higgs production, and the event shape broadening. This paper focuses on the other region, where the typical transverse momentum below and beyond the cutoff is of similar size. In this region the rapidity cutoff further resolves soft radiation into (u)soft and soft-collinear radiation with different rapidities but identical virtuality. This gives rise to rapidity logarithms of the rapidity cutoff parameter which we resum using renormalization group methods. We factorize the cross section in this region in terms of soft and collinear functions in the framework of soft-collinear effective theory, then further refactorize the soft function as a convolution of the (u)soft and soft-collinear functions. All these functions are calculated at one-loop order. As an example, we calculate a differential cross section for a specific partonic channel, qq ' → qq ' , for the jet shape angularities and show that the refactorization allows us to resum the rapidity logarithms and significantly reduce theoretical uncertainties in the jet shape spectrum.« less

Post sunset behavior of the 6300 A atomic oxygen airglow emission

NASA Technical Reports Server (NTRS)

Smith, R. E.

1976-01-01

A theoretical model of the 6300 A OI airglow emission was developed based on the assumptions that both the charged and neutral portions of the Earth's upper atmosphere are in steady state conditions of diffusive equilibrium. Intensities of 6300 A OI emission line were calculated using electron density true height profiles from a standard C-4 ionosonde and exospheric temperatures derived from Fabry-Perot interferometer measurements of the Doppler broadened 6300 A emission line shape as inputs to the model. Reaction rate coefficient values, production mechanism efficiencies, solar radiation fluxes, absorption cross sections, and models of the neutral atmosphere were varied parametrically to establish a set of acceptable inputs which will consistently predict 6300 A emission intensities that closely agree with intensities observed during the post-sunset twilight period by an airglow observatory consisting of a Fabry-Perot interferometer and a turret photometer. Emission intensities that can only result from the dissociative recombination of molecular oxygen ions were observed during the latter portion of the observational period. Theoretical calculations indicate that contamination of the 6300 A OI emission should be on the order of or less than 3 percent; however, these results are very sensitive to the wavelengths of the individual lines and their intensities relative to the 6300 A OI intensity. This combination of a model atmosphere, production mechanism efficiencies, and quenching coefficient values was used when the dissociative photoexcitation and direct impact excitation processes were contributing to the intensity to establish best estimates of solar radiation fluxes in the Schumann--Runge continuum and associated absorption cross sections. Results show that the Jacchia 1971 model of the upper atmosphere combined with the Ackerman recommended solar radiation fluxes and associated absorption cross sections produces theoretically calculated intensities that more closely agree with the observed intensities than all the other combinations.

Comparison of experimentally and theoretically determined radiation characteristics of photosynthetic microorganisms

NASA Astrophysics Data System (ADS)

Kandilian, Razmig; Pruvost, Jérémy; Artu, Arnaud; Lemasson, Camille; Legrand, Jack; Pilon, Laurent

2016-05-01

This paper aims to experimentally and directly validate a recent theoretical method for predicting the radiation characteristics of photosynthetic microorganisms. Such predictions would facilitate light transfer analysis in photobioreactors (PBRs) to control their operation and to maximize their production of biofuel and other high-value products. The state of the art experimental method can be applied to microorganisms of any shape and inherently accounts for their non-spherical and heterogeneous nature. On the other hand, the theoretical method treats the microorganisms as polydisperse homogeneous spheres with some effective optical properties. The absorption index is expressed as the weighted sum of the pigment mass absorption cross-sections and the refractive index is estimated based on the subtractive Kramers-Kronig relationship given an anchor refractive index and wavelength. Here, particular attention was paid to green microalgae Chlamydomonas reinhardtii grown under nitrogen-replete and nitrogen-limited conditions and to Chlorella vulgaris grown under nitrogen-replete conditions. First, relatively good agreement was found between the two methods for determining the mass absorption and scattering cross-sections and the asymmetry factor of both nitrogen-replete and nitrogen-limited C. reinhardtii with the proper anchor point. However, the homogeneous sphere approximation significantly overestimated the absorption cross-section of C. vulgaris cells. The latter were instead modeled as polydisperse coated spheres consisting of an absorbing core containing pigments and a non-absorbing but strongly refracting wall made of sporopollenin. The coated sphere approximation gave good predictions of the experimentally measured integral radiation characteristics of C. vulgaris. In both cases, the homogeneous and coated sphere approximations predicted resonance in the scattering phase function that were not observed experimentally. However, these approximations were sufficiently accurate to predict the fluence rate and local rate of photon absorption in PBRs.

Thermal neutron capture cross sections for 16,171,18O and 2H

NASA Astrophysics Data System (ADS)

Firestone, R. B.; Revay, Zs.

2016-04-01

Thermal neutron capture γ -ray spectra for 16,17,18O and 2H have been measured with guided cold neutron beams from the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) reactor and the Budapest Research Reactor (BRR) on natural and O,1817 enriched D2O targets. Complete neutron capture γ -ray decay schemes for the 16,17,18O(n ,γ ) reactions were measured. Absolute transition probabilities were determined for each reaction by a least-squares fit of the γ -ray intensities to the decay schemes after accounting for the contribution from internal conversion. The transition probability for the 870.76-keV γ ray from 16O(n ,γ ) was measured as Pγ(871 )=96.6 ±0.5 % and the thermal neutron cross section for this γ ray was determined as 0.164 ±0.003 mb by internal standardization with multiple targets containing oxygen and stoichiometric quantities of hydrogen, nitrogen, and carbon whose γ -ray cross sections were previously standardized. The γ -ray cross sections for the O,1817(n ,γ ) and 2H(n ,γ ) reactions were then determined relative to the 870.76-keV γ -ray cross section after accounting for the isotopic abundances in the targets. We determined the following total radiative thermal neutron cross sections for each isotope from the γ -ray cross sections and transition probabilities; σ0(16O )=0.170 ±0.003 mb; σ0(17O )=0.67 ±0.07 mb; σ0(18O )=0.141 ±0.006 mb; and σ0(2H )=0.489 ±0.006 mb.

Depolarization and Scattering of Electromagnetic Waves. Appendices.

DTIC Science & Technology

1986-06-30

for both specular point scattering and Bragg scattering in a self-consistent manner is used to express the total cross section of the flake as a...by Arbitrarily Oriented Composite Rough Surfaces. In this work the full wave approach is used to determine the modu- lations of the like and cross...analyze multiple scattering using the equation of radiative transfer with the general Stokes’ parameters. Our ultimate goal is to develop codes which will

Measurement of the e+e-→π+π-π0π0 cross section using initial-state radiation at BABAR

NASA Astrophysics Data System (ADS)

Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Kolomensky, Yu. G.; Fritsch, M.; Koch, H.; Schroeder, T.; Hearty, C.; Mattison, T. S.; McKenna, J. A.; So, R. Y.; Blinov, V. E.; Buzykaev, A. R.; Druzhinin, V. P.; Golubev, V. B.; Kravchenko, E. A.; Onuchin, A. P.; Serednyakov, S. I.; Skovpen, Yu. I.; Solodov, E. P.; Todyshev, K. Yu.; Lankford, A. J.; Gary, J. W.; Long, O.; Eisner, A. M.; Lockman, W. S.; Panduro Vazquez, W.; Chao, D. S.; Cheng, C. H.; Echenard, B.; Flood, K. T.; Hitlin, D. G.; Kim, J.; Miyashita, T. S.; Ongmongkolkul, P.; Porter, F. C.; Röhrken, M.; Huard, Z.; Meadows, B. T.; Pushpawela, B. G.; Sokoloff, M. D.; Sun, L.; Smith, J. G.; Wagner, S. R.; Bernard, D.; Verderi, M.; Bettoni, D.; Bozzi, C.; Calabrese, R.; Cibinetto, G.; Fioravanti, E.; Garzia, I.; Luppi, E.; Santoro, V.; Calcaterra, A.; de Sangro, R.; Finocchiaro, G.; Martellotti, S.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Rotondo, M.; Zallo, A.; Passaggio, S.; Patrignani, C.; Lacker, H. M.; Bhuyan, B.; Mallik, U.; Chen, C.; Cochran, J.; Prell, S.; Ahmed, H.; Gritsan, A. V.; Arnaud, N.; Davier, M.; Le Diberder, F.; Lutz, A. M.; Wormser, G.; Lange, D. J.; Wright, D. M.; Coleman, J. P.; Gabathuler, E.; Hutchcroft, D. E.; Payne, D. J.; Touramanis, C.; Bevan, A. J.; di Lodovico, F.; Sacco, R.; Cowan, G.; Banerjee, Sw.; Brown, D. N.; Davis, C. L.; Denig, A. G.; Gradl, W.; Griessinger, K.; Hafner, A.; Schubert, K. R.; Barlow, R. J.; Lafferty, G. D.; Cenci, R.; Jawahery, A.; Roberts, D. A.; Cowan, R.; Robertson, S. H.; Dey, B.; Neri, N.; Palombo, F.; Cheaib, R.; Cremaldi, L.; Godang, R.; Summers, D. J.; Taras, P.; de Nardo, G.; Sciacca, C.; Raven, G.; Jessop, C. P.; Losecco, J. M.; Honscheid, K.; Kass, R.; Gaz, A.; Margoni, M.; Posocco, M.; Simi, G.; Simonetto, F.; Stroili, R.; Akar, S.; Ben-Haim, E.; Bomben, M.; Bonneaud, G. R.; Calderini, G.; Chauveau, J.; Marchiori, G.; Ocariz, J.; Biasini, M.; Manoni, E.; Rossi, A.; Batignani, G.; Bettarini, S.; Carpinelli, M.; Casarosa, G.; Chrzaszcz, M.; Forti, F.; Giorgi, M. A.; Lusiani, A.; Oberhof, B.; Paoloni, E.; Rama, M.; Rizzo, G.; Walsh, J. J.; Smith, A. J. S.; Anulli, F.; Faccini, R.; Ferrarotto, F.; Ferroni, F.; Pilloni, A.; Piredda, G.; Bünger, C.; Dittrich, S.; Grünberg, O.; Heß, M.; Leddig, T.; Voß, C.; Waldi, R.; Adye, T.; Wilson, F. F.; Emery, S.; Vasseur, G.; Aston, D.; Cartaro, C.; Convery, M. R.; Dorfan, J.; Dunwoodie, W.; Ebert, M.; Field, R. C.; Fulsom, B. G.; Graham, M. T.; Hast, C.; Innes, W. R.; Kim, P.; Leith, D. W. G. S.; Luitz, S.; Macfarlane, D. B.; Muller, D. R.; Neal, H.; Ratcliff, B. N.; Roodman, A.; Sullivan, M. K.; Va'Vra, J.; Wisniewski, W. J.; Purohit, M. V.; Wilson, J. R.; Randle-Conde, A.; Sekula, S. J.; Bellis, M.; Burchat, P. R.; Puccio, E. M. T.; Alam, M. S.; Ernst, J. A.; Gorodeisky, R.; Guttman, N.; Peimer, D. R.; Soffer, A.; Spanier, S. M.; Ritchie, J. L.; Schwitters, R. F.; Izen, J. M.; Lou, X. C.; Bianchi, F.; de Mori, F.; Filippi, A.; Gamba, D.; Lanceri, L.; Vitale, L.; Martinez-Vidal, F.; Oyanguren, A.; Albert, J.; Beaulieu, A.; Bernlochner, F. U.; King, G. J.; Kowalewski, R.; Lueck, T.; Nugent, I. M.; Roney, J. M.; Sobie, R. J.; Tasneem, N.; Gershon, T. J.; Harrison, P. F.; Latham, T. E.; Prepost, R.; Wu, S. L.; Babar Collaboration

2017-11-01

The process e+e-→π+π-2 π0γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb-1 of data collected around a center-of-mass energy of √{s }=10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel's contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as (gμπ+π-2 π0-2 )/2 =(17.9 ±0.1stat±0.6syst)×10-10 in the energy range 0.85 GeV

Radiative Corrections to e^ + e^ - -> bar tt in Electroweak Theory

NASA Astrophysics Data System (ADS)

Fujimoto, Junpei; Shimizu, Yoshimitsu

The 0(α) radiative corrections to e^ + e^ - -> bar tt are calculated in the standard SU(2)×U(1) theory keeping the top quark mass. The contribution of the hard photon emission is included with suitable experimental cuts. We found that the 1-loop vertex diagrams for the top quark give rise to a fairly large correction in the order of 5% to the differential cross-section. Effects of the Higgs boson exchange are also discussed.

Photoionization of the Buckminsterfullerene Cation.

PubMed

Douix, Suzie; Duflot, Denis; Cubaynes, Denis; Bizau, Jean-Marc; Giuliani, Alexandre

2017-01-05

Photoionization of a buckminsterfullerene ion is investigated using an ion trap and a merged beam setup coupled to synchrotron radiation beamlines and compared to theoretical calculations. Absolute measurements derived from the ion trap experiment allow discrepancies concerning the photoionization cross section of C 60 + to be solved.

A coupled modal-finite element method for the wave propagation modeling in irregular open waveguides.

PubMed

Pelat, Adrien; Felix, Simon; Pagneux, Vincent

2011-03-01

In modeling the wave propagation within a street canyon, particular attention must be paid to the description of both the multiple reflections of the wave on the building facades and the radiation in the free space above the street. The street canyon being considered as an open waveguide with a discontinuously varying cross-section, a coupled modal-finite element formulation is proposed to solve the three-dimensional wave equation within. The originally open configuration-the street canyon open in the sky above-is artificially turned into a close waveguiding structure by using perfectly matched layers that truncate the infinite sky without introducing numerical reflection. Then the eigenmodes of the resulting waveguide are determined by a finite element method computation in the cross-section. The eigensolutions can finally be used in a multimodal formulation of the wave propagation along the canyon, given its geometry and the end conditions at its extremities: initial field condition at the entrance and radiation condition at the output. © 2011 Acoustical Society of America

Study of the process e + e – → π + π – η using initial state radiation

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

Lees, J. P.; Poireau, V.; Tisserand, V.

Here, we study the process e +e –→π +π –ηγ, where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BABAR data sample with an integrated luminosity of 469 fb –1. Using the π +π –η invariant mass spectrum, we measure the e +e –→π +π –η cross section in the e +e – center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson dominance model with four ρ-like states. We observe 49±9 events of the J/ψ decay to π +π –ηmore » and measure the product Γ J/Ψ→e+e–BJ/Ψ→π+π–η=2.34±0.43 stat±0.16 syst eV.« less

Study of the process e + e – → π + π – η using initial state radiation

DOE PAGES

Lees, J. P.; Poireau, V.; Tisserand, V.; ...

2018-03-21

Here, we study the process e +e –→π +π –ηγ, where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BABAR data sample with an integrated luminosity of 469 fb –1. Using the π +π –η invariant mass spectrum, we measure the e +e –→π +π –η cross section in the e +e – center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson dominance model with four ρ-like states. We observe 49±9 events of the J/ψ decay to π +π –ηmore » and measure the product Γ J/Ψ→e+e–BJ/Ψ→π+π–η=2.34±0.43 stat±0.16 syst eV.« less

Monte Carlo studies on photon interactions in radiobiological experiments

PubMed Central

Shahmohammadi Beni, Mehrdad; Krstic, D.; Nikezic, D.

2018-01-01

X-ray and γ-ray photons have been widely used for studying radiobiological effects of ionizing radiations. Photons are indirectly ionizing radiations so they need to set in motion electrons (which are a directly ionizing radiation) to perform the ionizations. When the photon dose decreases to below a certain limit, the number of electrons set in motion will become so small that not all cells in an “exposed” cell population can get at least one electron hit. When some cells in a cell population are not hit by a directly ionizing radiation (in other words not irradiated), there will be rescue effect between the irradiated cells and non-irradiated cells, and the resultant radiobiological effect observed for the “exposed” cell population will be different. In the present paper, the mechanisms underlying photon interactions in radiobiological experiments were studied using our developed NRUphoton computer code, which was benchmarked against the MCNP5 code by comparing the photon dose delivered to the cell layer underneath the water medium. The following conclusions were reached: (1) The interaction fractions decreased in the following order: 16O > 12C > 14N > 1H. Bulges in the interaction fractions (versus water medium thickness) were observed, which reflected changes in the energies of the propagating photons due to traversals of different amount of water medium as well as changes in the energy-dependent photon interaction cross-sections. (2) Photoelectric interaction and incoherent scattering dominated for lower-energy (10 keV) and high-energy (100 keV and 1 MeV) incident photons. (3) The fractions of electron ejection from different nuclei were mainly governed by the photoelectric effect cross-sections, and the fractions from the 1s subshell were the largest. (4) The penetration fractions in general decreased with increasing medium thickness, and increased with increasing incident photon energy, the latter being explained by the corresponding reduction in interaction cross-sections. (5) The areas under the angular distribution curves of photons exiting the medium layer and subsequently undergoing interactions within the cell layer became smaller for larger incident photon energies. (6) The number of cells suffering at least one electron hit increased with the administered dose. For larger incident photon energies, the numbers of cells suffering at least one electron hit became smaller, which was attributed to the reduction in the photon interaction cross-section. These results highlighted the importance of the administered dose in radiobiological experiments. In particular, the threshold administered doses at which all cells in the exposed cell array suffered at least one electron hit might provide hints on explaining the intriguing observation that radiation-induced cancers can be statistically detected only above the threshold value of ~100 mSv, and thus on reconciling controversies over the linear no-threshold model. PMID:29561871

Impact of Track Structure Effects on Shielding and Dosimetry

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Cucinotta, F. A.; Schimmerling, W.; Kim, M. Y.

1999-01-01

Galactic cosmic rays (GCR) consisting of nuclei of all the known elements with kinetic energies extending from tens to millions of MeV pose a significant health hazard to future deep space operations. Even half of the radiation exposures expected in ISS will result from GCR components. The biological actions of these radiations are known to depend on the details of the energy deposition (not just linear energy transfer, LET, but the lateral dispersion of energy deposition about the particle track). Energy deposits in tissues are dominated by the transfer of tens to hundreds of eV to the tissue's atomic electrons. In the case of low LET radiations, the collisions are separated by large dimensions compared to the size of important biomolecular structures. If such events are also separated in time, then the radiation adds little to the background of radicals occurring from ordinary metabolic processes and causes little or no biological injury. Hence, dose rate is a strong determinant of the action of low LET exposures. The GCR exposures are dominated by ions of high charge and energy (HZE) characterized by many collisions with atomic electrons over biomolecular dimensions, resulting in high radical- density events associated with a few isolated ion paths through the cell and minimal dose rate dependence at ordinary exposure levels. The HZE energy deposit declines quickly laterally and merges with the background radical density in the track periphery for which the exact lateral distribution of the energy deposit is the determinant of the biological injury. Although little data exists on human exposures from HZE radiations, limited studies in mice and mammalian cell cultures allow evaluation of the effects of track structure on shield attenuation properties and evaluation of implications for dosimetry. The most complete mammalian cell HZE exposure data sets have been modeled including the C3H10T1/2 survival and transformation data of Yang et al., the V79 survival and mutation data of various groups, and the Harderian gland tumor data of Alpen et al. Model results for the Harderian gland tumor data in comparison with data from Alpen et al. The Harderian target cell initiation cross section compares closely with the transformation cross section found for the C3H10T1/2 cell transformation data of Yang et al. The most notable feature of the cross sections are the multivalued cross sections for a given LET which implies the corresponding relative biological effectiveness (RBE) is dependent not only on the LET but also the ion type. This fact is at variance with the latest ICRP recommended quality factor which is a defined function of only the LET.

Neutron radiative capture reactions on nuclei of relevance to 0νββ, dark matter and neutrino/antineutrino searches

NASA Astrophysics Data System (ADS)

Tornow, W.; Bhike, Megha

2015-05-01

A program is underway at the Triangle Universities Nuclear Laboratory (TUNL) to measure the neutron capture cross section in the 0.5 to 15 MeV energy range on nuclei whose radioactive daughters could potentially create backgrounds in searches for rare events. Here, we refer to neutrino-less double-beta decay and dark-matter searches, and to detectors built for neutrino and/or antineutrino studies. Neutron capture cross-section data obtained by using the activation method are reported for 40Ar, 74,76Ge, 128,130Te and 136Xe and compared to model calculations and evaluations.

Finite-element reentry heat-transfer analysis of space shuttle Orbiter

NASA Technical Reports Server (NTRS)

Ko, William L.; Quinn, Robert D.; Gong, Leslie

1986-01-01

A structural performance and resizing (SPAR) finite-element thermal analysis computer program was used in the heat-transfer analysis of the space shuttle orbiter subjected to reentry aerodynamic heating. Three wing cross sections and one midfuselage cross section were selected for the thermal analysis. The predicted thermal protection system temperatures were found to agree well with flight-measured temperatures. The calculated aluminum structural temperatures also agreed reasonably well with the flight data from reentry to touchdown. The effects of internal radiation and of internal convection were found to be significant. The SPAR finite-element solutions agreed reasonably well with those obtained from the conventional finite-difference method.

The Zero-Degree Detector System for Fragmentation Studies

NASA Technical Reports Server (NTRS)

Adams, J. H., Jr.; Christl, M. J.; Howell, L. W.; Kuznetsov, E.

2006-01-01

The measurement of nuclear fragmentation cross sections requires the detection and identification of individual projectile fragments. If light and heavy fragments are recorded in 'ne same detector, it may be impossible distinguish the signal from the light fragment. To overcome this problem, we have developed the Zero-Degree Detector System. The ZDDS enables the measurement of cross sections for light fragment production by using pixelated detectors to separately measure the signals of each fragment. The system has been used to measure the fragmentation of beams as heavy as Fe at the NASA Space Radiation Laboratory at Brookhaven National Laboratory and the Heavy Ion Medical Accelerator in Chiba, Japan.

Calculated stopping powers of low-energy electrons in some materials of interest in radiation protection.

PubMed

Akande, W

1993-03-01

Stopping powers of low-energy (< 10 keV) electrons in aluminum, copper, cesium, barium, lead, lithium, and uranium were calculated using an analytic method. The interaction of the electrons with the materials were characterized in terms of three cross sections for total ionization and total scattering. Experimental cross section data were collated, where available, for the materials. The expressions were then fitted to the data to obtain the values of the relevant constants in the expressions. This enabled the basic equation of stopping powers of electrons to be evaluated for the materials. Comparison of the results obtained with those of other workers was affected.

Photoabsorption and photodissociation of molecules important in the interstellar medium

NASA Technical Reports Server (NTRS)

Lee, Long C.; Suto, Masako

1991-01-01

The photoabsorption, photodissociation, and fluorescence cross sections of interstellar molecules are measured at 90 to 250 nm. These quantitative optical data are needed for the understanding of the formation and destruction processes of molecules under the intense interstellar UV radiation field. Research covering the following topics is presented: (1) fluorescences from photoexcitation of CH4, CH3OH, and CH3SH; (2) NO gamma emission from photoexcitation of NO; (3) photoexcitation cross sections of aromatic molecules; (4) IR emission from UV excitation of HONO2; (5) IR emission from UV excitation of benzene and methyl-derivitives; and (6) IR emission from UV excitation of polycyclic aromatic hydrocarbon molecules.

Investigation of Activation Cross Sections of the Proton Induced Nuclear Reactions on Natural Iron at Medium Energies

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

Ditroi, F.; Tarkanyi, F.; Csikai, J.

2005-05-24

Iron is one of the most important structural materials in every field of science, technology, industry, etc. Its application in a radiating environment requires the knowledge of accurate excitation functions for the possible reactions in question. By using the Thin Layer Activation technique (TLA) the knowledge of such data is also extremely important even in the case of relative measurements to design the irradiation (irradiation energy, beam intensity, duration) and also for radioactive safety estimations. The cross sections are frequently measured at low energies but there are unsatisfactory and unreliable data in the energy range above 40 MeV.

Investigation of Activation Cross Sections of the Proton Induced Nuclear Reactions on Natural Iron at Medium Energies

NASA Astrophysics Data System (ADS)

Ditrói, F.; Tárkányi, F.; Csikai, J.; Uddin, M. S.; Hagiwara, M.; Baba, M.

2005-05-01

Iron is one of the most important structural materials in every field of science, technology, industry, etc. Its application in a radiating environment requires the knowledge of accurate excitation functions for the possible reactions in question. By using the Thin Layer Activation technique (TLA) the knowledge of such data is also extremely important even in the case of relative measurements to design the irradiation (irradiation energy, beam intensity, duration) and also for radioactive safety estimations. The cross sections are frequently measured at low energies but there are unsatisfactory and unreliable data in the energy range above 40 MeV.

Triple Photoionization of Neon and Argon Near Threshold

NASA Astrophysics Data System (ADS)

Bluett, Jaques B.; Lukić, Dragan; Sellin, Ivan A.; Whitfield, Scott B.; Wehlitz, Ralf

2003-05-01

The threshold behavior of the triple ionization cross-section of neon and argon was investigated using monochromatized synchrotron radiation and ion time-of-flight spectrometry. The Ne^3+ and Ar^3+ cross-sections are found to follow the Wannier power law(G.H. Wannier, Phys. Rev. 90), 817 (1953). consistent with a Wannier exponent of 2.162 predicted by theory. This is also consistent with the findings of Samson and Angel(J.A.R. Samson and G.C. Angel, Phys. Lett. 61), 1584 (1988). for the case of Ne. In the case of argon we find a much shorter range of validity than for neon.

Investigation of the radiation background in the interaction region of the medium-energy electron relativisitic heavy ion collider (MeRHIC)

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

Beebe-Wang,J.

There are three main sources of the radiation background in MeRHIC: forward synchrotron radiation generated upstream of the detector, the direct backward radiation caused by the photons hitting beampipe downstream of the detector, and the indirect secondary radiation caused by hard photons hitting vacuum systems, masks, collimators, absorbers or any other elements in the interaction region. In this paper, we first calculate the primary radiation distribution by employing electromagnetic theory. Then we obtain the direct backward scattering rate by applying the kinematic Born approximation deduced from scattering dynamics. The diffuse scattering cross section is calculated as a function of themore » surface properties of the MeRHIC vacuum system. Finally, the dominating physical processes and minimization of indirect secondary radiation is presented and discussed.« less

Occupational radiation exposure and its health effects on interventional medical workers: study protocol for a prospective cohort study.

PubMed

Ko, Seulki; Chung, Hwan Hoon; Cho, Sung Bum; Jin, Young Woo; Kim, Kwang Pyo; Ha, Mina; Bang, Ye Jin; Ha, Yae Won; Lee, Won Jin

2017-12-15

Although fluoroscopically guided procedures involve a considerably high dose of radiation, few studies have investigated the effects of radiation on medical workers involved in interventional fluoroscopy procedures. Previous research remains in the early stages and has not reached a level comparable with other occupational studies thus far. Furthermore, the study of radiation workers provides an opportunity to estimate health risks at low doses and dose rates of ionising radiation. Therefore, the objectives of this study are (1) to initiate a prospective cohort study by conducting a baseline survey among medical radiation workers who involve interventional fluoroscopy procedures and (2) to assess the effect of occupational radiation exposure and on the overall health status through an in-depth cross-sectional study. Intervention medical workers in Korea will be enrolled by using a self-administered questionnaire survey, and the survey data will be linked with radiation dosimetry data, National Health Insurance claims data, cancer registry and mortality data. After merging these data, the radiation organ dose, lifetime attributable risk due to cancer and the risk per unit dose will be estimated. For the cross-sectional study, approximately 100 intervention radiology department workers will be investigated for blood tests, clinical examinations such as ultrasonography (thyroid and carotid artery scan) and lens opacity, the validation of badge dose and biodosimetry. This study was reviewed and approved by the institutional review board of Korea University (KU-IRB-12-12-A-1). All participants will provide written informed consent prior to enrolment. The findings of the study will be disseminated through peer-reviewed scientific journals, conference presentations, and a report will be submitted to the relevant public health authorities in the Korea Centers for Disease Control and Prevention to help with the development of appropriate research and management policies. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Occupational radiation exposure and its health effects on interventional medical workers: study protocol for a prospective cohort study

PubMed Central

Ko, Seulki; Chung, Hwan Hoon; Cho, Sung Bum; Jin, Young Woo; Kim, Kwang Pyo; Ha, Mina; Bang, Ye Jin; Ha, Yae Won; Lee, Won Jin

2017-01-01

Introduction Although fluoroscopically guided procedures involve a considerably high dose of radiation, few studies have investigated the effects of radiation on medical workers involved in interventional fluoroscopy procedures. Previous research remains in the early stages and has not reached a level comparable with other occupational studies thus far. Furthermore, the study of radiation workers provides an opportunity to estimate health risks at low doses and dose rates of ionising radiation. Therefore, the objectives of this study are (1) to initiate a prospective cohort study by conducting a baseline survey among medical radiation workers who involve interventional fluoroscopy procedures and (2) to assess the effect of occupational radiation exposure and on the overall health status through an in-depth cross-sectional study. Methods and analysis Intervention medical workers in Korea will be enrolled by using a self-administered questionnaire survey, and the survey data will be linked with radiation dosimetry data, National Health Insurance claims data, cancer registry and mortality data. After merging these data, the radiation organ dose, lifetime attributable risk due to cancer and the risk per unit dose will be estimated. For the cross-sectional study, approximately 100 intervention radiology department workers will be investigated for blood tests, clinical examinations such as ultrasonography (thyroid and carotid artery scan) and lens opacity, the validation of badge dose and biodosimetry. Ethics and dissemination This study was reviewed and approved by the institutional review board of Korea University (KU-IRB-12-12-A-1). All participants will provide written informed consent prior to enrolment. The findings of the study will be disseminated through peer-reviewed scientific journals, conference presentations, and a report will be submitted to the relevant public health authorities in the Korea Centers for Disease Control and Prevention to help with the development of appropriate research and management policies. PMID:29248885

Soft-photon emission effects and radiative corrections for electromagnetic processes at very high energies

NASA Technical Reports Server (NTRS)

Gould, R. J.

1979-01-01

Higher-order electromagnetic processes involving particles at ultrahigh energies are discussed, with particular attention given to Compton scattering with the emission of an additional photon (double Compton scattering). Double Compton scattering may have significance in the interaction of a high-energy electron with the cosmic blackbody photon gas. At high energies the cross section for double Compton scattering is large, though this effect is largely canceled by the effects of radiative corrections to ordinary Compton scattering. A similar cancellation takes place for radiative pair production and the associated radiative corrections to the radiationless process. This cancellation is related to the well-known cancellation of the infrared divergence in electrodynamics.

On the absolute photoionization cross section and dissociative photoionization of cyclopropenylidene.

PubMed

Holzmeier, Fabian; Fischer, Ingo; Kiendl, Benjamin; Krueger, Anke; Bodi, Andras; Hemberger, Patrick

2016-04-07

We report the determination of the absolute photoionization cross section of cyclopropenylidene, c-C3H2, and the heat of formation of the C3H radical and ion derived by the dissociative ionization of the carbene. Vacuum ultraviolet (VUV) synchrotron radiation as provided by the Swiss Light Source and imaging photoelectron photoion coincidence (iPEPICO) were employed. Cyclopropenylidene was generated by pyrolysis of a quadricyclane precursor in a 1 : 1 ratio with benzene, which enabled us to derive the carbene's near threshold absolute photoionization cross section from the photoionization yield of the two pyrolysis products and the known cross section of benzene. The cross section at 9.5 eV, for example, was determined to be 4.5 ± 1.4 Mb. Upon dissociative ionization the carbene decomposes by hydrogen atom loss to the linear isomer of C3H(+). The appearance energy for this process was determined to be AE(0K)(c-C3H2; l-C3H(+)) = 13.67 ± 0.10 eV. The heat of formation of neutral and cationic C3H was derived from this value via a thermochemical cycle as Δ(f)H(0K)(C3H) = 725 ± 25 kJ mol(-1) and Δ(f)H(0K)(C3H(+)) = 1604 ± 19 kJ mol(-1), using a previously reported ionization energy of C3H.

Indirect study of 12C(α,γ)16O reaction

NASA Astrophysics Data System (ADS)

Hammache, F.; Oulebsir, N.; Roussel, P.; Pellegriti, M. G.; Audouin, L.; Beaumel, D.; Bouda, A.; Descouvemont, P.; Fortier, S.; Gaudefroy, L.; Kiener, J.; Lefebvre-Schuhl, A.; Tatischeff, V.

2016-01-01

The radiative capture reaction 12C(α,γ)16O plays an important role in helium burning in massive stars and their subsequent evolution [1]. However, despite various experimental studies, the cross section of this reaction at stellar energies remains highly uncertain. The extrapolation down to stellar energy (Ecm˜300 keV) of the measured cross sections at higher energies is made difficult by the overlap of various contributions of which some are badly known such as that of the 2+ (Ex=6.92 MeV) and 1- (Ex=7.12 MeV) sub-threshold states of 16O. Hence, to further investigate the contribution of these two-subthreshold resonances to the 12C(α,γ)16O cross section, a new determination of their a-reduced widths and so their a- spectroscopic-factors was performed using 12C(7Li,t)16O transfer reaction measurements at two incident energies and a detailed DWBA analysis of the data [2]. The measured and calculated differential cross sections are presented as well as the obtained spectroscopic factors and the a- reduced widths as well as the assymptotic normalization constants (ANC) for the 2+ and 1- subthreshold states. Finally, the results obtained from the R-matrix calculations of the 12C(α,γ)16O cross section using our obtained a-reduced widths for the two sub-threshold resonances are presented and discussed.

Photoionization Efficiencies of Five Polycyclic Aromatic Hydrocarbons

DOE PAGES

Johansson, K. Olof; Campbell, Matthew F.; Elvati, Paolo; ...

2017-05-18

We have measured photoionization-efficiency curves for pyrene, fluoranthene, chrysene, perylene, and coronene in the photon energy range of 7.5-10.2 eV and derived their photoionization cross-section curves in this energy range. All measurements were performed using tunable vacuum ultraviolet (VUV) radiation generated at the Advanced Light Source synchrotron at Lawrence Berkeley National Laboratory. The VUV radiation was used for photoionization, and detection was performed using a time-of-flight mass spectrometer. We measured the photoionization efficiency of 2,5-dimethylfuran simultaneously with those of pyrene, fluoranthene, chrysene, perylene, and coronene to obtain references of the photon flux during each measurement from the known photoionization cross-sectionmore » curve of 2,5- dimethylfuran.« less

Sunshine Skyway Bridge monitoring phase I : system assessment and integration recommendations [summary].

DOT National Transportation Integrated Search

2016-10-01

At over five miles long, the Sunshine Skyway Bridge, crossing Tampa Bay where it meets the Gulf of Mexico, is one of the worlds longest cable-stayed bridges. The pier-supported approaches rise to meet the center section where cables radiating from...

Comparative study of Monte Carlo particle transport code PHITS and nuclear data processing code NJOY for recoil cross section spectra under neutron irradiation

NASA Astrophysics Data System (ADS)

Iwamoto, Yosuke; Ogawa, Tatsuhiko

2017-04-01

Because primary knock-on atoms (PKAs) create point defects and clusters in materials that are irradiated with neutrons, it is important to validate the calculations of recoil cross section spectra that are used to estimate radiation damage in materials. Here, the recoil cross section spectra of fission- and fusion-relevant materials were calculated using the Event Generator Mode (EGM) of the Particle and Heavy Ion Transport code System (PHITS) and also using the data processing code NJOY2012 with the nuclear data libraries TENDL2015, ENDF/BVII.1, and JEFF3.2. The heating number, which is the integral of the recoil cross section spectra, was also calculated using PHITS-EGM and compared with data extracted from the ACE files of TENDL2015, ENDF/BVII.1, and JENDL4.0. In general, only a small difference was found between the PKA spectra of PHITS + TENDL2015 and NJOY + TENDL2015. From analyzing the recoil cross section spectra extracted from the nuclear data libraries using NJOY2012, we found that the recoil cross section spectra were incorrect for 72Ge, 75As, 89Y, and 109Ag in the ENDF/B-VII.1 library, and for 90Zr and 55Mn in the JEFF3.2 library. From analyzing the heating number, we found that the data extracted from the ACE file of TENDL2015 for all nuclides were problematic in the neutron capture region because of incorrect data regarding the emitted gamma energy. However, PHITS + TENDL2015 can calculate PKA spectra and heating numbers correctly.

Differential cross section measurements for hadron therapy: 50 MeV/nucleon 12C reactions on H, C, O, Al, and natTi targets

NASA Astrophysics Data System (ADS)

Divay, C.; Colin, J.; Cussol, D.; Finck, Ch.; Karakaya, Y.; Labalme, M.; Rousseau, M.; Salvador, S.; Vanstalle, M.

2017-04-01

During a carbon therapy treatment, the beam undergoes inelastic nuclear reactions leading to the production of secondary fragments. These nuclear interactions tend to delocate a part of the dose into healthy tissues and create a mixed radiation field. In order to accurately estimate the dose deposited into the tissues, the production rate of these fragments all along the beam path have to be taken into account. But the double differential carbon fragmentation cross sections are not well known in the energy range needed for a treatment (up to 400 MeV/nucleon). Therefore, a series of experiments aiming to measure the double differential fragmentation cross sections of carbon on thin targets of medical interest has been started by our collaboration. In March 2015 we performed an experiment to study the fragmentation of a 50 MeV/nucleon 12C beam on thin targets at GANIL. During this experiment, energy and angular cross-section distributions on H, C, O, Al, and natTi have been measured. The experimental set-up will be detailed as well as the systematic error study and all the experimental results will be presented.

Optical nonlinearities of colloidal InP@ZnS core-shell quantum dots probed by Z-scan and two-photon excited emission

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

Wawrzynczyk, Dominika; Szeremeta, Janusz; Samoc, Marek

Spectrally resolved nonlinear optical properties of colloidal InP@ZnS core-shell quantum dots of various sizes were investigated with the Z-scan technique and two-photon fluorescence excitation method using a femtosecond laser system tunable in the range from 750 nm to 1600 nm. In principle, both techniques should provide comparable results and can be interchangeably used for determination of the nonlinear optical absorption parameters, finding maximal values of the cross sections and optimizing them. We have observed slight differences between the two-photon absorption cross sections measured by the two techniques and attributed them to the presence of non-radiative paths of absorption or relaxation.more » The most significant value of two-photon absorption cross section σ{sub 2} for 4.3 nm size InP@ZnS quantum dot was equal to 2200 GM, while the two-photon excitation action cross section σ{sub 2}Φ was found to be 682 GM at 880 nm. The properties of these cadmium-free colloidal quantum dots can be potentially useful for nonlinear bioimaging.« less

The Thermoluminescence Response of Ge-Doped Flat Fibers to Gamma Radiation

PubMed Central

Mat Nawi, Siti Nurasiah Binti; Wahib, Nor Fadira Binti; Zulkepely, Nurul Najua Binti; Amin, Yusoff Bin Mohd; Min, Ung Ngie; Bradley, David Andrew; Md Nor, Roslan Bin; Maah, Mohd Jamil

2015-01-01

Study has been undertaken of the thermoluminescence (TL) yield of various tailor-made flat cross-section 6 mol% Ge-doped silica fibers, differing only in respect of external dimensions. Key TL dosimetric characteristics have been investigated, including glow curves, dose response, sensitivity, fading and reproducibility. Using a 60Co source, the samples were irradiated to doses within the range 1 to 10 Gy. Prior to irradiation, the flat fibers were sectioned into 6 mm lengths, weighed, and annealed at 400 °C for 1 h. TL readout was by means of a Harshaw Model 3500 TLD reader, with TLD-100 chips (LiF:Mg, Ti) used as a reference dosimeter to allow the relative response of the fibers to be evaluated. The fibers have been found to provide highly linear dose response and excellent reproducibility over the range of doses investigated, demonstrating high potential as TL-mode detectors in radiation medicine applications. Mass for mass, the results show the greatest TL yield to be provided by fibers of the smallest cross-section, analysis indicating this to be due to minimal light loss in transport of the TL through the bulk of the silica medium. PMID:26307987

Collisionless dissociation and isotopic enrichment of SF6 using high-powered CO2 laser radiation

NASA Technical Reports Server (NTRS)

Gower, M. C.; Billman, K. W.

1977-01-01

Dissociation of S-32F6 and the resultant isotopic enrichment of S-34F6 using high-powered CO2 laser radiation has been studied with higher experimental sensitivity than previously reported. Enrichment factors have been measured as a function of laser pulse number, wavelength, energy and time duration. A geometry independent dissociation cross section is introduced and measured values are presented. Threshold energy densities, below which no dissociation was observed, were also determined.

Laser stripping of hydrogen atoms by direct ionization

DOE PAGES

Brunetti, E.; Becker, W.; Bryant, H. C.; ...

2015-05-08

Direct ionization of hydrogen atoms by laser irradiation is investigated as a potential new scheme to generate proton beams without stripping foils. The time-dependent Schrödinger equation describing the atom-radiation interaction is numerically solved obtaining accurate ionization cross-sections for a broad range of laser wavelengths, durations and energies. Parameters are identified where the Doppler frequency up-shift of radiation colliding with relativistic particles can lead to efficient ionization over large volumes and broad bandwidths using currently available lasers.

Self-consistent models for Coulomb-heated X-ray pulsar atmospheres

NASA Technical Reports Server (NTRS)

Harding, A. K.; Kirk, J. G.; Galloway, D. J.; Meszaros, P.

1984-01-01

Calculations of accreting magnetized neutron star atmospheres heated by the gradual deceleration of Protons via Coulomb collisions are presented. Self consistent determinations of the temperature and density structure for different accretion rates are made by assuming hydrostatic equilibrium and energy balance, coupled with radiative transfer. The full radiative transfer in two polarizations, using magnetic cross sections but with cyclotron resonance effects treated approximately, is carried out in the inhomogeneous atmospheres. Previously announced in STAR as N84-12012

Laser stripping of hydrogen atoms by direct ionization

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

Brunetti, E.; Becker, W.; Bryant, H. C.

Direct ionization of hydrogen atoms by laser irradiation is investigated as a potential new scheme to generate proton beams without stripping foils. The time-dependent Schrödinger equation describing the atom-radiation interaction is numerically solved obtaining accurate ionization cross-sections for a broad range of laser wavelengths, durations and energies. Parameters are identified where the Doppler frequency up-shift of radiation colliding with relativistic particles can lead to efficient ionization over large volumes and broad bandwidths using currently available lasers.

Oscillator strengths and integral cross sections for the valence-shell excitations of nitric oxide studied by fast electron impact.

PubMed

Xu, Xin; Xu, Long-Quan; Xiong, Tao; Chen, Tao; Liu, Ya-Wei; Zhu, Lin-Fan

2018-01-28

The generalized oscillator strengths for the valence-shell excitations of A 2 Σ + , C 2 Π, and D 2 Σ + electronic-states of nitric oxide have been determined at an incident electron energy of 1500 eV with an energy resolution of 70 meV. The optical oscillator strengths for these transitions have been obtained by extrapolating the generalized oscillator strengths to the limit that the squared momentum transfer approaches to zero, which give an independent cross-check to the previous experimental and theoretical results. The integral cross sections for the valence-shell excitations of nitric oxide have been determined systematically from the threshold to 2500 eV with the aid of the newly developed BE-scaling method for the first time. The present optical oscillator strengths and integral cross sections of the valence-shell excitations of nitric oxide play an important role in understanding many physics and chemistry of the Earth's upper atmosphere such as the radiative cooling, ozone destruction, day glow, aurora, and so on.

The deuterium puzzle in the symmetric universe

NASA Technical Reports Server (NTRS)

Leroy, B.; Nicolle, J. P.; Schatzman, E.

1973-01-01

An attempt was made to use deuterium abundance in the symmetric universe to prove that no nucleosynthesis takes place during annihilation and therefore neutrons were loss before nucleosynthesis. Data cover nucleosynthesis during the radiative era, cross section estimates, maximum abundance of He-4 at the end of nucleosynthesis area, and loss rate.

Implementation of radiation shielding calculation methods. Volume 2: Seminar/Workshop notes

NASA Technical Reports Server (NTRS)

Capo, M. A.; Disney, R. K.

1971-01-01

Detailed descriptions are presented of the input data for each of the MSFC computer codes applied to the analysis of a realistic nuclear propelled vehicle. The analytical techniques employed include cross section data, preparation, one and two dimensional discrete ordinates transport, point kernel, and single scatter methods.

Observation of runaway electron beams by visible color camera in the Experimental Advanced Superconducting Tokamak

NASA Astrophysics Data System (ADS)

Shi, Yuejiang; Fu, Jia; Li, Jiahong; Yang, Yu; Wang, Fudi; Li, Yingying; Zhang, Wei; Wan, Baonian; Chen, Zhongyong

2010-03-01

The synchrotron radiation originated from the energetic runaway electrons has been measured by a visible complementary metal oxide semiconductor camera working in the wavelength ranges of 380-750 nm in the Experimental Advanced Superconducting Tokamak [H. Q. Liu et al., Plasma Phys. Contr. Fusion 49, 995 (2007)]. With a tangential viewing into the plasma in the direction of electron approach on the equatorial plane, the synchrotron radiation from the energetic runaway electrons was measured in full poloidal cross section. The synchrotron radiation diagnostics provides a direct pattern of the runaway beam inside the plasma. The energy and pitch angle of runaway electrons have been obtained according to the synchrotron radiation pattern. A stable shell shape of synchrotron radiation has been observed in a few runaway discharges.

Atomic Data for the K-vacancy States of Fe XXIV

NASA Technical Reports Server (NTRS)

Bautista, M. A.; Mendoza, C.; Kallman, T. R.; Palmeri, P.

2003-01-01

As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of atomic data for K-vacancy states in Fe XXIV. The data sets include: (i) energy levels, line wavelengths, radiative and Auger rates; (ii) inner-shell electron impact excitation rates and (iii) fine structure inner-shell photoionization cross sections. The calculations of energy levels and radiative and Auger rates have involved a detailed study of orbital representations, core relaxation, configuration interaction, relativistic corrections, cancellation effects and semi-empirical corrections. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%. The calculations of collisional excitation and photoionization cross sections take into account the effects of radiation and spectator Auger dampings. In the former, these effects cause significant attenuation of resonances leading to a good agreement with a simpler method where resonances are excluded. In the latter, resonances converging to the K threshold display symmetric profiles of constant width that causes edge smearing.

Atomic Data for the K-Vacancy States of Fe XXIV

NASA Technical Reports Server (NTRS)

Bautista, M. A.; Mendoza, C.; Kallman, T. R.; Palmeri, P.

2002-01-01

As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of atomic data for K-vacancy states in Fe XXIV. The data sets include: (i) energy levels, line wavelengths, radiative and Auger rates; (ii) inner-shell electron impact excitation rates and (iii) fine structure inner-shell photoionization cross sections. The calculations of energy levels and radiative and Auger rates have involved a detailed study of orbital representations, core relaxation, configuration interaction, relativistic corrections, cancellation effects and semi-empirical corrections. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%. The calculations of collisional excitation and photoionization cross sections take into account the effects of radiation and spectator Auger dampings. In the former, these effects cause significant attenuation of resonances leading to a good agreement with a simpler method where resonances are excluded. In the latter, resonances converging to the K threshold display symmetric profiles of constant width that causes edge smearing.

Calculation and Measurement of Low-Energy Radiative Moller Scattering

NASA Astrophysics Data System (ADS)

Epstein, Charles; DarkLight Collaboration

2017-09-01

A number of current nuclear physics experiments have come to rely on precise knowledge of electron-electron (Moller) and positron-electron (Bhabha) scattering. Some of these experiments, having lepton beams on targets containing atomic electrons, use these purely-QED processes as normalization. In other scenarios, with electron beams at low energy and very high intensity, Moller scattering and radiative Moller scattering have such enormous cross-sections that the backgrounds they produce must be understood. In this low-energy regime, the electron mass is also not negligible in the calculation of the cross section. This is important, for example, in the DarkLight experiment (100 MeV). As a result, we have developed a new event generator for the radiative Moller and Bhabha processes, with new calculations that keep all terms of the electron mass. The MIT High Voltage Research Laboratory provides us a unique opportunity to study this process experimentally and compare it with our work, at a low beam energy of 2.5 MeV where the effects of the electron mass are significant. We are preparing a dedicated apparatus consisting of a magnetic spectrometer in order to directly measure this process. An overview of the calculation and the status of the experiment will be presented.

Quantitative photoabsorption and fluorescence spectroscopy of benzene, naphthalene, and some derivatives at 106-295 nm

NASA Technical Reports Server (NTRS)

Suto, Masako; Wang, Xiuyan; Shan, Jun; Lee, L. C.

1992-01-01

Photoabsorption and fluorescence cross sections of benzene, (o-, m-, p-) xylenes, naphthalene, 1-methylnaphthalene, and 2-ethylnaphthalene in the gas phase are measured at 106-295 nm using synchrotron radiation as a light source. Fluorescences are observed from the photoexcitation of benzene and xylenes at 230-280 nm and from naphthalene and its derivatives at 190-295 nm. The absolute fluorescence cross section is determined by calibration with respect to the emission intensity of the NO(A-X) system, for which the fluorescence quantum yield is equal to 1. To cross-check the current calibration method, the quantum yield of the SO2(C-X) system at 220-230 nm was measured since it is about equal to 1. The current quantum-yield data are compared with previously published values measured by different methods.

Radiation exposure and risk assessment for critical female body organs

NASA Technical Reports Server (NTRS)

Atwell, William; Weyland, Mark D.; Hardy, Alva C.

1991-01-01

Space radiation exposure limits for astronauts are based on recommendations of the National Council on Radiation Protection and Measurements. These limits now include the age at exposure and sex of the astronaut. A recently-developed computerized anatomical female (CAF) model is discussed in detail. Computer-generated, cross-sectional data are presented to illustrate the completeness of the CAF model. By applying ray-tracing techniques, shield distribution functions have been computed to calculate absorbed dose and dose equivalent values for a variety of critical body organs (e.g., breasts, lungs, thyroid gland, etc.) and mission scenarios. Specific risk assessments, i.e., cancer induction and mortality, are reviewed.

Computer Model Of Fragmentation Of Atomic Nuclei

NASA Technical Reports Server (NTRS)

Wilson, John W.; Townsend, Lawrence W.; Tripathi, Ram K.; Norbury, John W.; KHAN FERDOUS; Badavi, Francis F.

1995-01-01

High Charge and Energy Semiempirical Nuclear Fragmentation Model (HZEFRG1) computer program developed to be computationally efficient, user-friendly, physics-based program for generating data bases on fragmentation of atomic nuclei. Data bases generated used in calculations pertaining to such radiation-transport applications as shielding against radiation in outer space, radiation dosimetry in outer space, cancer therapy in laboratories with beams of heavy ions, and simulation studies for designing detectors for experiments in nuclear physics. Provides cross sections for production of individual elements and isotopes in breakups of high-energy heavy ions by combined nuclear and Coulomb fields of interacting nuclei. Written in ANSI FORTRAN 77.

Plasmonic nanoparticle chain in a light field: a resonant optical sail.

PubMed

Albaladejo, Silvia; Sáenz, Juan José; Marqués, Manuel I

2011-11-09

Optical trapping and driving of small objects has become a topic of increasing interest in multidisciplinary sciences. We propose to use a chain made of metallic nanoparticles as a resonant light sail, attached by one end point to a transparent object and propelling it by the use of electromagnetic radiation. Driving forces exerted on the chain are theoretically studied as a function of radiation's wavelength and chain's alignments with respect to the direction of radiation. Interestingly, there is a window in the frequency spectrum in which null-torque equilibrium configuration, with minimum geometric cross section, corresponds to a maximum in the driving force.

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

Langguth, K.G.

The theory from MERKLE et al. has been applied to radiation damage in Ni single crytal caused by irradiation with 2MeV $sup 4$He$sup +$ ions. The determined dechanneling cross section sigmasub(d) of the vacancy cluster in Ni was: 4 . 10$sup -15$ cm$sup 2$<=sigmasub(d)<=1.7 . 10$sup -14$cm$sup 2$ for 2MeV $sup 4$He$sup +$. These values are found within the limits of the dechanneling cross sections determined by MERKLE for defect clusters in Au which were between 4 . 10$sup -15$ and 2.4 . 10$sup -14$cm$sup 2$ for the same particles and energies. The average cascade radius was found between 50Amore » and 90A. (FR)« less

First observation of RDEC for gas (N2) targets with F9+

NASA Astrophysics Data System (ADS)

Kumara, P. N. S.; La Mantia, D. S.; Simon, A.; Kayani, A.; Tanis, J. A.

2017-10-01

Radiative double electron capture (RDEC) is a fundamental atomic process predicted to occur in ion-atom collisions. Several attempts were made to show experimental evidence for RDEC after it was introduced theoretically in 1987. The first successful measurements were done for O8+ ions colliding with a thin carbon foil in 2010, followed by measurements for F9+ projectiles incident on carbon. The works reported here are the first observations giving preliminary results for RDEC in collisions of F9+ projectiles with gas (N2) targets. X-rays were observed in the region of interest and an estimation of RDEC cross section was calculated. These cross sections are compared with recent theoretical calculations.

Study of final-state radiation in decays of Z bosons produced in $pp$ collisions at 7 TeV

DOE PAGES

Khachatryan, Vardan

2015-05-29

The differential cross sections for the production of photons in Z→μ +μ -γ decays are presented as a function of the transverse energy of the photon and its separation from the nearest muon. The data for these measurements are collected with the CMS detector and correspond to an integrated luminosity of 4.7 fb -1 of pp collisions at √s=7 TeV delivered by the CERN LHC. The cross sections are compared to simulations with powheg and pythia, where pythia is used to simulate parton showers and final-state photons. These simulations match the data to better than 5%.

Direct processes in 54-MeV Li-7 breakup reactions on C-12 and Au-197 targets, and the extraction of astrophysical cross sections

NASA Astrophysics Data System (ADS)

Gazes, S. B.; Mason, J. E.; Roberts, R. B.; Teichmann, S. G.

1992-01-01

Strong direct processes were observed for elastic breakup in 54-MeV Li-7 + C-12, Au-197 reactions. In the case of C-12, the observed Li-7 to alpha + t direct-breakup yield was significantly larger than predicted by a Coulomb-breakup calculation, indicating the importance of the nuclear field. For Au-197, final-state interactions produced a strong distortion in the fragment energy spectra, as well as a modulation of the coincidence efficiency for different detector geometries. Such Coulomb effects are found to severely complicate the extraction of radiative-capture cross sections from direct-breakup data.

Photodissociation of CS from Excited Rovibrational Levels

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Radiation and chemistry in the stratosphere - Sensitivity to O2 absorption cross sections in the Herzberg continuum

NASA Technical Reports Server (NTRS)

Froidevaux, L.; Yung, Y. L.

1982-01-01

It is suggested that the discrepancies between observed and modeled vertical profiles of such halocarbons as CFCl3, as well as the problem of simultaneously fitting N2O, CH4, CF2Cl2 and CFCl3 profiles with a single eddy diffusion model, are due to an overestimation of the molecular oxygen absorption cross sections in the 200-220 nm spectral region. The replacement of current O2 cross sections in this range with values that are in better agreement with results for the compounds cited leads to N2O, CF2Cl2 and CFCl3 concentration reductions of factors 0.70, 0.62 and 0.19, respectively. Profiles of CH4, H2 and CO remain unchanged, and the predicted concentration of HNO3 above 30 km is reduced by about 50% for yet another improved fit with observations. It is noted that the correction proposed produces a 30% ozone increase near the 20-25 km peak.

Calculation of fast neutron removal cross sections for different lunar soils

NASA Astrophysics Data System (ADS)

Tellili, B.; Elmahroug, Y.; Souga, C.

2014-01-01

The interaction of galactic cosmic rays (GCRs) and solar energetic particles (SEPs) with the lunar surface produces secondary radiations as neutrons. The study of the production and attenuation of these neutrons in the lunar soil is very important to estimate the annual ambient dose equivalent on the lunar surface and for lunar nuclear spectroscopy. Also, understanding the attenuation of fast neutrons in lunar soils can help in measuring of the lunar neutron density profile and to measure the neutron flux on the lunar surface. In this paper, the attenuation of fast neutrons in different lunar soils is investigated. The macroscopic effective removal cross section (ΣR) of fast neutrons was theoretically calculated from the mass removal cross-section values (ΣR/ρ) for various elements in soils. The obtained values of (ΣR) were discussed according to the density. The results show that the attenuation of fast neutrons is more important in the landing sites of Apollo 12 and Luna 16 than the other landing sites of Apollo and Luna missions.

Modelling of micromachining of human tooth enamel by erbium laser radiation

NASA Astrophysics Data System (ADS)

Belikov, A. V.; Skrypnik, A. V.; Shatilova, K. V.

2014-08-01

We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength between the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained.

Challenges in Optical Emission Spectroscopy

NASA Astrophysics Data System (ADS)

Siepa, Sarah; Berger, Birk; Schulze, Julian; Schuengel, Edmund; von Keudell, Achim

2016-09-01

Collisional-radiative models (CRMs) are widely used to investigate plasma properties such as electron density, electron temperature and the form of the electron energy distribution function. In this work an extensive CRM for argon is presented, which models 30 excited states and various kinds of processes including electron impact excitation/de-excitation, radiation and radiation trapping. The CRM is evaluated in several test cases, i.e. inductively and capacitively coupled plasmas at various pressures, powers/voltages and gas admixtures. Deviations are found between modelled and measured spectra. The escape factor as a means of describing radiation trapping is discussed as well as the cross section data for electron impact processes. This work was supported by the Ruhr University Research School PLUS, funded by Germany's Excellence Initiative [DFG GSC 98/3].

Beam shaping of laser diode radiation by waveguides with arbitrary cladding geometry written with fs-laser radiation.

PubMed

Beckmann, Dennis; Schnitzler, Daniel; Schaefer, Dagmar; Gottmann, Jens; Kelbassa, Ingomar

2011-12-05

Waveguides with arbitrary cross sections are written in the volume of Al(2)O(3)-crystals using tightly focused femtosecond laser radiation. Utilizing a scanning system with large numerical aperture, complex cladding geometries are realized with a precision around 0.5 µm and a scanning speed up to 100 mm/s. Individual beam and mode shaping of laser diode radiation is demonstrated by varying the design of the waveguide cladding. The influence of the writing parameters on the waveguide properties are investigated resulting in a numerical aperture of the waveguides in the range of 0.1. This direct laser writing technique enables optical devices which could possibly replace bulky beam shaping setups with an integrated solution.

Heavy-ion-induced sucrose radicals investigated using EPR and UV spectroscopy.

PubMed

Nakagawa, Kouichi; Karakirova, Yordanka; Yordanov, Nicola D

2015-05-01

The potential use of a sucrose dosimeter for estimating both linear energy transfer (LET) and the absorbed dose of heavy ion and X-ray radiation was investigated. The stable free radicals were produced when sucrose was irradiated with heavy ions, such as helium, carbon, silicon and neon ions, and when the X-ray radiation was similar to the obtained electron paramagnetic resonance (EPR) spectra, which were ∼7 mT wide and composed of several hyperfine structures. In addition, the total spin concentration resulting from heavy-ion irradiation increased linearly as the absorbed dose increased, and decreased logarithmically as the LET increased. These empirical relations imply that the LET at a certain dose can be determined from the spin concentration. For sucrose and alanine, both cross-sections following C-ion irradiation with a 50 Gy dose were ∼1.3 × 10(-12) [μm(2)], taking into account the molecular size of the samples. The values of these cross-sections imply that multiple ionizing particles were involved in the production of stable radicals. Furthermore, UV absorbance at 267 nm of an aqueous solution of irradiated sucrose was found to linearly increase with increasing absorbed dose. Therefore, the EPR and UV results suggest that sucrose can be a useful dosimeter for heavy-ion irradiation. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Uncertainty Analysis of Air Radiation for Lunar Return Shock Layers

NASA Technical Reports Server (NTRS)

Kleb, Bil; Johnston, Christopher O.

2008-01-01

By leveraging a new uncertainty markup technique, two risk analysis methods are used to compute the uncertainty of lunar-return shock layer radiation predicted by the High temperature Aerothermodynamic Radiation Algorithm (HARA). The effects of epistemic uncertainty, or uncertainty due to a lack of knowledge, is considered for the following modeling parameters: atomic line oscillator strengths, atomic line Stark broadening widths, atomic photoionization cross sections, negative ion photodetachment cross sections, molecular bands oscillator strengths, and electron impact excitation rates. First, a simplified shock layer problem consisting of two constant-property equilibrium layers is considered. The results of this simplified problem show that the atomic nitrogen oscillator strengths and Stark broadening widths in both the vacuum ultraviolet and infrared spectral regions, along with the negative ion continuum, are the dominant uncertainty contributors. Next, three variable property stagnation-line shock layer cases are analyzed: a typical lunar return case and two Fire II cases. For the near-equilibrium lunar return and Fire 1643-second cases, the resulting uncertainties are very similar to the simplified case. Conversely, the relatively nonequilibrium 1636-second case shows significantly larger influence from electron impact excitation rates of both atoms and molecules. For all cases, the total uncertainty in radiative heat flux to the wall due to epistemic uncertainty in modeling parameters is 30% as opposed to the erroneously-small uncertainty levels (plus or minus 6%) found when treating model parameter uncertainties as aleatory (due to chance) instead of epistemic (due to lack of knowledge).

Nurses', physicians' and radiographers' perceptions of the safety of a nurse prescribing of ionising radiation initiative: A cross-sectional survey.

PubMed

Hyde, Abbey; Coughlan, Barbara; Naughton, Corina; Hegarty, Josephine; Savage, Eileen; Grehan, Jennifer; Kavanagh, Eoin; Moughty, Adrian; Drennan, Jonathan

2016-06-01

A new initiative was introduced in Ireland following legislative changes that allowed nurses with special training to prescribe ionising radiation (X-ray) for the first time. A small number of studies on nurse prescribing of ionising radiation in other contexts have found it to be broadly as safe as ionising radiation prescribing by physicians. Sociological literature on perceptions of safety indicates that these tend to be shaped by the ideological position of the professional rather than based on objective evidence. To describe, compare and analyse perceptions of the safety of a nurse prescribing of ionising radiation initiative across three occupational groups: nursing, radiography and medicine. A cross-sectional survey design. Participants were drawn from a range of clinical settings in Ireland. Respondents were 167 health professionals comprised of 49 nurses, 91 radiographers, and 27 physicians out of a total of 300 who were invited to participate. Non-probability sampling was employed and the survey was targeted specifically at health professionals with a specific interest in, or involvement with, the development of the nurse prescribing of ionising radiation initiative in Ireland. Comparisons of perspectives on the safety of nurse prescribing of ionising radiation across the three occupational groups captured by questionnaire were analysed using the Kruskal-Wallis H test. Pairwise post hoc tests were conducted using the Mann-Whitney U test. While the majority of respondents from all three groups perceived nurse prescribing of ionising radiation to be safe, the extent to which this view was held varied. A higher proportion of nurses was found to display confidence in the safety of nurse prescribing of ionising radiation compared to physicians and radiographers with differences between nurses' perceptions and those of the other two groups being statistically significant. That an occupational patterning emerged suggests that perceptions about safety and risk of nurse prescribing of ionising radiation are socially constructed according to the vantage point of the professional and may not reflect objective measures of safety. These findings need to be considered more broadly in the context of ideological barriers to expanding the role of nurses. Copyright © 2016 Elsevier Ltd. All rights reserved.

The compliance with and knowledge about radiation protection in operating room personnel: a cross-sectional study with a questionnaire.

PubMed

Jentzsch, Thorsten; Pietsch, Christiane M; Stigler, Brigitte; Ramseier, Leonhard E; Seifert, Burkhardt; Werner, Clément M L

2015-09-01

Radiation protection is becoming more important with an ongoing increase in radiation exposure due to the use of X-rays in minimally invasive procedures in orthopaedic and trauma surgeries. However, sufficient education in medical physics and radiation protection can often be improved. A questionnaire consisting of four questions about personal data and ten questions about radiation protection was distributed to lead consultants, consultants, residents, medical students, and medical technical assistants at two institutions, a level 1 trauma center and a children's hospital. This study consisted of 83 participants. The compliance with radiation protection, i.e., usage of a dosimetry, an apron, and a thyroid shield on a regular basis was only seen in 54 %. Participants from the trauma center wore a dosimeter and thyroid shield significantly more often. The regular use of a thyroid shield differed significantly between job positions. It was observed in 80 % of students, but only 15 % of technical assistants. Only 65 % of all knowledge questions were answered correctly. There was a discrepancy between incorrectly answered knowledge questions (35 %) and those marked as uncertain (20 %). Different job positions did not have an impact on the answers to the questions in most instances. The compliance with and the knowledge about radiation protection seems to be unnecessarily low in trauma physicians and technical assistants. The discrepancy in falsely answered questions and those marked as uncertain may suggest that participants may overestimate their knowledge about radiation protection, which is potentially harmful due to the increased radiation exposure. Therefore, we advocate a quick and valuable training of trauma surgeons and medical staff addressing the important preventive measures, some of which are illustrated in the present study. These consist of wearing dosimetry and protection devices, reduction in X-ray duration, preferably antero-posterior C-arm positioning with the image intensifier close to the patient and the surgeon, maximal distance, collimation, and increased voltage. Furthermore, the use of visual feedback on complex and potentially hazardous radiation facts may be useful for training purposes. Cross-sectional study with a questionnaire.

Scaled plane-wave Born cross sections for atoms and molecules

NASA Astrophysics Data System (ADS)

Tanaka, H.; Brunger, M. J.; Campbell, L.; Kato, H.; Hoshino, M.; Rau, A. R. P.

2016-04-01

Integral cross sections for optically allowed electronic-state excitations of atoms and molecules by electron impact, by applying scaled plane-wave Born models, are reviewed. Over 40 years ago, Inokuti presented an influential review of charged-particle scattering, based on the theory pioneered by Bethe forty years earlier, which emphasized the importance of reliable cross-section data from low eV energies to high keV energies that are needed in many areas of radiation science with applications to astronomy, plasmas, and medicine. Yet, with a couple of possible exceptions, most computational methods in electron-atom scattering do not, in general, overlap each other's validity range in the region from threshold up to 300 eV and, in particular, in the intermediate region from 30 to 300 eV. This is even more so for electron-molecule scattering. In fact this entire energy range is of great importance and, to bridge the gap between the two regions of low and high energy, scaled plane-wave Born models were developed to provide reliable, comprehensive, and absolute integral cross sections, first for ionization by Kim and Rudd and then extended to optically allowed electronic-state excitation by Kim. These and other scaling models in a broad, general application to electron scattering from atoms and molecules, their theoretical basis, and their results for cross sections along with comparison to experimental measurements are reviewed. Where possible, these data are also compared to results from other computational approaches.

Development of ORIGEN Libraries for Mixed Oxide (MOX) Fuel Assembly Designs

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

Mertyurek, Ugur; Gauld, Ian C.

In this research, ORIGEN cross section libraries for reactor-grade mixed oxide (MOX) fuel assembly designs have been developed to provide fast and accurate depletion calculations to predict nuclide inventories, radiation sources and thermal decay heat information needed in safety evaluations and safeguards verification measurements of spent nuclear fuel. These ORIGEN libraries are generated using two-dimensional lattice physics assembly models that include enrichment zoning and cross section data based on ENDF/B-VII.0 evaluations. Using the SCALE depletion sequence, burnup-dependent cross sections are created for selected commercial reactor assembly designs and a representative range of reactor operating conditions, fuel enrichments, and fuel burnup.more » The burnup dependent cross sections are then interpolated to provide problem-dependent cross sections for ORIGEN, avoiding the need for time-consuming lattice physics calculations. The ORIGEN libraries for MOX assembly designs are validated against destructive radiochemical assay measurements of MOX fuel from the MALIBU international experimental program. This program included measurements of MOX fuel from a 15 × 15 pressurized water reactor assembly and a 9 × 9 boiling water reactor assembly. The ORIGEN MOX libraries are also compared against detailed assembly calculations from the Phase IV-B numerical MOX fuel burnup credit benchmark coordinated by the Nuclear Energy Agency within the Organization for Economic Cooperation and Development. Finally, the nuclide compositions calculated by ORIGEN using the MOX libraries are shown to be in good agreement with other physics codes and with experimental data.« less

Resonant parametric interference effect in spontaneous bremsstrahlung of an electron in the field of a nucleus and two pulsed laser waves

NASA Astrophysics Data System (ADS)

Lebed', A. A.; Padusenko, E. A.; Roshchupkin, S. P.; Dubov, V. V.

2018-04-01

Electron-nucleus bremsstrahlung in the field of two moderately strong pulsed laser waves in the case of incommensurate frequencies is theoretically studied under resonant conditions. The process is studied in detail in a special kinematic region, where stimulated processes with correlated emission and absorption of photons of the first and second waves become predominant (parametric interference effect). The availability of this region is caused by interference of the first and second laser waves. The correspondence between the emission angle and the final-electron energy is established in this interference kinematic. In this case, the cross-sectional properties are determined by the multiphoton quantum interference parameter, which is proportional to the product of intensities of the first and second waves. The resonant differential cross section of electron-nucleus spontaneous bremsstrahlung with simultaneous registration of both emission angles of the spontaneous photon and the scattered electron can exceed by four or five orders of magnitude the corresponding cross section in the absence of an external field. It was shown for nonrelativistic electrons that the resonant cross section of the studied process in the field of two pulsed laser waves within the interference region in two order of magnitude may exceed corresponding cross sections at other scattering kinematics. The obtained results may be experimentally verified, for example, by scientific facilities at sources of pulsed laser radiation (such as SLAC, FAIR, XFEL, ELI).

Development of ORIGEN Libraries for Mixed Oxide (MOX) Fuel Assembly Designs

DOE PAGES

Mertyurek, Ugur; Gauld, Ian C.

2015-12-24

In this research, ORIGEN cross section libraries for reactor-grade mixed oxide (MOX) fuel assembly designs have been developed to provide fast and accurate depletion calculations to predict nuclide inventories, radiation sources and thermal decay heat information needed in safety evaluations and safeguards verification measurements of spent nuclear fuel. These ORIGEN libraries are generated using two-dimensional lattice physics assembly models that include enrichment zoning and cross section data based on ENDF/B-VII.0 evaluations. Using the SCALE depletion sequence, burnup-dependent cross sections are created for selected commercial reactor assembly designs and a representative range of reactor operating conditions, fuel enrichments, and fuel burnup.more » The burnup dependent cross sections are then interpolated to provide problem-dependent cross sections for ORIGEN, avoiding the need for time-consuming lattice physics calculations. The ORIGEN libraries for MOX assembly designs are validated against destructive radiochemical assay measurements of MOX fuel from the MALIBU international experimental program. This program included measurements of MOX fuel from a 15 × 15 pressurized water reactor assembly and a 9 × 9 boiling water reactor assembly. The ORIGEN MOX libraries are also compared against detailed assembly calculations from the Phase IV-B numerical MOX fuel burnup credit benchmark coordinated by the Nuclear Energy Agency within the Organization for Economic Cooperation and Development. Finally, the nuclide compositions calculated by ORIGEN using the MOX libraries are shown to be in good agreement with other physics codes and with experimental data.« less

Processing and validation of JEFF-3.1.1 and ENDF/B-VII.0 group-wise cross section libraries for shielding calculations

NASA Astrophysics Data System (ADS)

Pescarini, M.; Sinitsa, V.; Orsi, R.; Frisoni, M.

2013-03-01

This paper presents a synthesis of the ENEA-Bologna Nuclear Data Group programme dedicated to generate and validate group-wise cross section libraries for shielding and radiation damage deterministic calculations in nuclear fission reactors, following the data processing methodology recommended in the ANSI/ANS-6.1.2-1999 (R2009) American Standard. The VITJEFF311.BOLIB and VITENDF70.BOLIB finegroup coupled n-γ (199 n + 42 γ - VITAMIN-B6 structure) multi-purpose cross section libraries, based on the Bondarenko method for neutron resonance self-shielding and respectively on JEFF-3.1.1 and ENDF/B-VII.0 evaluated nuclear data, were produced in AMPX format using the NJOY-99.259 and the ENEA-Bologna 2007 Revision of the SCAMPI nuclear data processing systems. Two derived broad-group coupled n-γ (47 n + 20 γ - BUGLE-96 structure) working cross section libraries in FIDO-ANISN format for LWR shielding and pressure vessel dosimetry calculations, named BUGJEFF311.BOLIB and BUGENDF70.BOLIB, were generated by the revised version of SCAMPI, through problem-dependent cross section collapsing and self-shielding from the cited fine-group libraries. The validation results on the criticality safety benchmark experiments for the fine-group libraries and the preliminary validation results for the broad-group working libraries on the PCA-Replica and VENUS-3 engineering neutron shielding benchmark experiments are reported in synthesis.

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

Brown, Nicholas; Burns, Joseph R.

The aftermath of the Tōhoku earthquake and the Fukushima accident has led to a global push to improve the safety of existing light water reactors. A key component of this initiative is the development of nuclear fuel and cladding materials with potentially enhanced accident tolerance, also known as accident-tolerant fuels (ATF). These materials are intended to improve core fuel and cladding integrity under beyond design basis accident conditions while maintaining or enhancing reactor performance and safety characteristics during normal operation. To complement research that has already been carried out to characterize ATF neutronics, the present study provides an initial investigationmore » of the sensitivity and uncertainty of ATF systems responses to nuclear cross section data. ATF concepts incorporate novel materials, including SiC and FeCrAl cladding and high density uranium silicide composite fuels, in turn introducing new cross section sensitivities and uncertainties which may behave differently from traditional fuel and cladding materials. In this paper, we conducted sensitivity and uncertainty analysis using the TSUNAMI-2D sequence of SCALE with infinite lattice models of ATF assemblies. Of all the ATF materials considered, it is found that radiative capture in 56Fe in FeCrAl cladding is the most significant contributor to eigenvalue uncertainty. 56Fe yields significant potential eigenvalue uncertainty associated with its radiative capture cross section; this is by far the largest ATF-specific uncertainty found in these cases, exceeding even those of uranium. We found that while significant new sensitivities indeed arise, the general sensitivity behavior of ATF assemblies does not markedly differ from traditional UO2/zirconium-based fuel/cladding systems, especially with regard to uncertainties associated with uranium. We assessed the similarity of the IPEN/MB-01 reactor benchmark model to application models with FeCrAl cladding. We used TSUNAMI-IP to calculate similarity indices of the application model and IPEN/MB-01 reactor benchmark model. This benchmark was selected for its use of SS304 as a cladding and structural material, with significant 56Fe content. The similarity indices suggest that while many differences in reactor physics arise from differences in design, sensitivity to and behavior of 56Fe absorption is comparable between systems, thus indicating the potential for this benchmark to reduce uncertainties in 56Fe radiative capture cross sections.« less

Feature Extraction Using Attributed Scattering Center Models for Model-Based Automatic Target Recognition (ATR)

DTIC Science & Technology

2005-10-01

section of the coiled arm. Right: measured realized total gain for a square spiral in free space with inductive treatment. . . . . . . . 154 8.5 Initial...appreciable velocities can often be easily separated from clutter returns, slow moving targets of more moderate cross sections can be very difficult to detect...electromagnetic radiation and measuring the energy scattered back. The data obtained as a result of this process is a finite-extent, noisy set of

Variation of the radiative properties during black carbon aging: theoretical and experimental intercomparison

DOE PAGES

He, C.; Liou, K.-N.; Takano, Y.; ...

2015-10-28

A theoretical black carbon (BC) aging model is developed to account for three typical evolution stages, namely, freshly emitted aggregates, BC coated by soluble material, and BC particles undergoing further hygroscopic growth. The geometric-optics surface-wave (GOS) approach is employed to compute the BC single-scattering properties at each aging stage, which are subsequently compared with laboratory measurements. Theoretical calculations are consistent with measurements in extinction and absorption cross sections for fresh BC aggregates with different BC sizes (i.e., mobility diameters of 155, 245, and 320 nm), with differences of ≤ 25 %. The measured optical cross sections for BC coated bymore » sulfuric acid and for that undergoing further hygroscopic growth are generally captured (differences < 30 %) by theoretical calculations using a concentric core-shell structure, with an overestimate in extinction and absorption of the smallest BC size and an underestimate in scattering of the largest BC size. We find that the absorption and scattering cross sections of fresh BC aggregates vary by 20–40 and 50–65 %, respectively, due to the use of upper (1.95–0.79 i) and lower (1.75–0.63 i) bounds of BC refractive index, while the variations are < 20 % in absorption and < 50 % in scattering in the case of coated BC particles. Sensitivity analyses of the BC morphology show that the optical properties of fresh BC aggregates are more sensitive to fractal dimension than primary spherule size. The absorption and scattering cross sections of coated BC particles vary by more than a factor of 2 due to different coating structures. We find an increase of 20–250 % in absorption and a factor of 3–15 in scattering during aging, significantly depending on coating morphology and aging stages. This study suggests that an accurate estimate of BC radiative effects requires the incorporation of a dynamic BC aging process that accounts for realistic coating structures in climate models.« less

Variation of the radiative properties during black carbon aging: theoretical and experimental intercomparison

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

He, C.; Liou, K.-N.; Takano, Y.

A theoretical black carbon (BC) aging model is developed to account for three typical evolution stages, namely, freshly emitted aggregates, BC coated by soluble material, and BC particles undergoing further hygroscopic growth. The geometric-optics surface-wave (GOS) approach is employed to compute the BC single-scattering properties at each aging stage, which are subsequently compared with laboratory measurements. Theoretical calculations are consistent with measurements in extinction and absorption cross sections for fresh BC aggregates with different BC sizes (i.e., mobility diameters of 155, 245, and 320 nm), with differences of ≤ 25 %. The measured optical cross sections for BC coated bymore » sulfuric acid and for that undergoing further hygroscopic growth are generally captured (differences < 30 %) by theoretical calculations using a concentric core-shell structure, with an overestimate in extinction and absorption of the smallest BC size and an underestimate in scattering of the largest BC size. We find that the absorption and scattering cross sections of fresh BC aggregates vary by 20–40 and 50–65 %, respectively, due to the use of upper (1.95–0.79 i) and lower (1.75–0.63 i) bounds of BC refractive index, while the variations are < 20 % in absorption and < 50 % in scattering in the case of coated BC particles. Sensitivity analyses of the BC morphology show that the optical properties of fresh BC aggregates are more sensitive to fractal dimension than primary spherule size. The absorption and scattering cross sections of coated BC particles vary by more than a factor of 2 due to different coating structures. We find an increase of 20–250 % in absorption and a factor of 3–15 in scattering during aging, significantly depending on coating morphology and aging stages. This study suggests that an accurate estimate of BC radiative effects requires the incorporation of a dynamic BC aging process that accounts for realistic coating structures in climate models.« less

Self-consistent ab initio Calculations for Photoionization and Electron-Ion Recombination Using the R-Matrix Method

NASA Astrophysics Data System (ADS)

Nahar, S. N.

2003-01-01

Most astrophysical plasmas entail a balance between ionization and recombination. We present new results from a unified method for self-consistent and ab initio calculations for the inverse processes of photoionization and (e + ion) recombination. The treatment for (e + ion) recombination subsumes the non-resonant radiative recombination and the resonant dielectronic recombination processes in a unified scheme (S.N. Nahar and A.K. Pradhan, Phys. Rev. A 49, 1816 (1994);H.L. Zhang, S.N. Nahar, and A.K. Pradhan, J.Phys.B, 32,1459 (1999)). Calculations are carried out using the R-matrix method in the close coupling approximation using an identical wavefunction expansion for both processes to ensure self-consistency. The results for photoionization and recombination cross sections may also be compared with state-of-the-art experiments on synchrotron radiation sources for photoionization, and on heavy ion storage rings for recombination. The new experiments display heretofore unprecedented detail in terms of resonances and background cross sections and thereby calibrate the theoretical data precisely. We find a level of agreement between theory and experiment at about 10% for not only the ground state but also the metastable states. The recent experiments therefore verify the estimated accuracy of the vast amount of photoionization data computed under the OP, IP and related works. features. Present work also reports photoionization cross sections including relativistic effects in the Breit-Pauli R-matrix (BPRM) approximation. Detailed features in the calculated cross sections exhibit the missing resonances due to fine structure. Self-consistent datasets for photoionization and recombination have so far been computed for approximately 45 atoms and ions. These are being reported in a continuing series of publications in Astrophysical J. Supplements (e.g. references below). These data will also be available from the electronic database TIPTOPBASE (http://heasarc.gsfc.nasa.gov)

A study to compute integrated dpa for neutron and ion irradiation environments using SRIM-2013

NASA Astrophysics Data System (ADS)

Saha, Uttiyoarnab; Devan, K.; Ganesan, S.

2018-05-01

Displacements per atom (dpa), estimated based on the standard Norgett-Robinson-Torrens (NRT) model, is used for assessing radiation damage effects in fast reactor materials. A computer code CRaD has been indigenously developed towards establishing the infrastructure to perform improved radiation damage studies in Indian fast reactors. We propose a method for computing multigroup neutron NRT dpa cross sections based on SRIM-2013 simulations. In this method, for each neutron group, the recoil or primary knock-on atom (PKA) spectrum and its average energy are first estimated with CRaD code from ENDF/B-VII.1. This average PKA energy forms the input for SRIM simulation, wherein the recoil atom is taken as the incoming ion on the target. The NRT-dpa cross section of iron computed with "Quick" Kinchin-Pease (K-P) option of SRIM-2013 is found to agree within 10% with the standard NRT-dpa values, if damage energy from SRIM simulation is used. SRIM-2013 NRT-dpa cross sections applied to estimate the integrated dpa for Fe, Cr and Ni are in good agreement with established computer codes and data. A similar study carried out for polyatomic material, SiC, shows encouraging results. In this case, it is observed that the NRT approach with average lattice displacement energy of 25 eV coupled with the damage energies from the K-P option of SRIM-2013 gives reliable displacement cross sections and integrated dpa for various reactor spectra. The source term of neutron damage can be equivalently determined in the units of dpa by simulating self-ion bombardment. This shows that the information of primary recoils obtained from CRaD can be reliably applied to estimate the integrated dpa and damage assessment studies in accelerator-based self-ion irradiation experiments of structural materials. This study would help to advance the investigation of possible correlations between the damages induced by ions and reactor neutrons.

2nd-order optical model of the isotopic dependence of heavy ion absorption cross sections for radiation transport studies

NASA Astrophysics Data System (ADS)

Cucinotta, Francis A.; Yan, Congchong; Saganti, Premkumar B.

2018-01-01

Heavy ion absorption cross sections play an important role in radiation transport codes used in risk assessment and for shielding studies of galactic cosmic ray (GCR) exposures. Due to the GCR primary nuclei composition and nuclear fragmentation leading to secondary nuclei heavy ions of charge number, Z with 3 ≤ Z ≥ 28 and mass numbers, A with 6 ≤ A ≥ 60 representing about 190 isotopes occur in GCR transport calculations. In this report we describe methods for developing a data-base of isotopic dependent heavy ion absorption cross sections for interactions. Calculations of a 2nd-order optical model solution to coupled-channel solutions to the Eikonal form of the nucleus-nucleus scattering amplitude are compared to 1st-order optical model solutions. The 2nd-order model takes into account two-body correlations in the projectile and target ground-states, which are ignored in the 1st-order optical model. Parameter free predictions are described using one-body and two-body ground state form factors for the isotopes considered and the free nucleon-nucleon scattering amplitude. Root mean square (RMS) matter radii for protons and neutrons are taken from electron and muon scattering data and nuclear structure models. We report on extensive comparisons to experimental data for energy-dependent absorption cross sections for over 100 isotopes of elements from Li to Fe interacting with carbon and aluminum targets. Agreement between model and experiments are generally within 10% for the 1st-order optical model and improved to less than 5% in the 2nd-order optical model in the majority of comparisons. Overall the 2nd-order optical model leads to a reduction in absorption compared to the 1st-order optical model for heavy ion interactions, which influences estimates of nuclear matter radii.

Neutron shielding behavior of thermoplastic natural rubber/boron carbide composites

NASA Astrophysics Data System (ADS)

Mat Zali, Nurazila; Yazid, Hafizal; Megat Ahmad, Megat Harun Al Rashid

2018-01-01

Many shielding materials have been designed against the harm of different types of radiation to the human body. Today, polymer-based lightweight composites have been chosen by the radiation protection industry. In the present study, thermoplastic natural rubber (TPNR) composites with different weight percent of boron carbide (B4C) fillers (0% to 30%) were fabricated as neutron shielding through melt blending method. Neutron attenuation properties of TPNR/B4C composites have been investigated. The macroscopic cross section (Σ), half value layer (HVL) and mean free path length (λ) of the composites have been calculated and the transmission curves have been plotted. The obtained results show that Σ, HVL and λ greatly depend on the B4C content. Addition of B4C fillers into TPNR matrix were found to enhance the macroscopic cross section values thus decrease the mean free path length (λ) and half value layer (HVL) of the composites. The transmission curves exhibited that the neutron transmission of the composites decreased with increasing shielding thickness. These results showed that TPNR/B4C composites have high potential for neutron shielding applications.

Description of Light Ion Production Cross Sections and Fluxes on the Mars Surface using the QMSFRG Model

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Kim, Myung-Hee; Schneider, Irene; Hassler, Donald M.

2006-01-01

The atmosphere of Mars significantly attenuates the heavy ion component of the primary galactic cosmic rays (GCR), however increases the fluence of secondary light ions (neutrons, and hydrogen and helium isotopes) because of particle production processes. We describe results of the quantum multiple scattering fragmentation (QMSFRG) model for the production of light nuclei through the distinct mechanisms of nuclear abrasion and ablation, coalescence, and cluster knockout. The QMSFRG model is shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections. We use the QMSFRG model and the space radiation transport code, HZETRN to make predictions of the light particle environment on the Martian surface at solar minimum and maximum. The radiation assessment detector (RAD) experiment will be launched in 2009 as part of the Mars Science Laboratory (MSL). We make predictions of the expected results for time dependent count-rates to be observed by RAD experiment. Finally, we consider sensitivity assessments of the impact of the Martian atmospheric composition on particle fluxes at the surface.

Quantitative and Isolated Measurement of Far-Field Light Scattering by a Single Nanostructure

NASA Astrophysics Data System (ADS)

Kim, Donghyeong; Jeong, Kwang-Yong; Kim, Jinhyung; Ee, Ho-Seok; Kang, Ju-Hyung; Park, Hong-Gyu; Seo, Min-Kyo

2017-11-01

Light scattering by nanostructures has facilitated research on various optical phenomena and applications by interfacing the near fields and free-propagating radiation. However, direct quantitative measurement of far-field scattering by a single nanostructure on the wavelength scale or less is highly challenging. Conventional back-focal-plane imaging covers only a limited solid angle determined by the numerical aperture of the objectives and suffers from optical aberration and distortion. Here, we present a quantitative measurement of the differential far-field scattering cross section of a single nanostructure over the full hemisphere. In goniometer-based far-field scanning with a high signal-to-noise ratio of approximately 27.4 dB, weak scattering signals are efficiently isolated and detected under total-internal-reflection illumination. Systematic measurements reveal that the total and differential scattering cross sections of a Au nanorod are determined by the plasmonic Fabry-Perot resonances and the phase-matching conditions to the free-propagating radiation, respectively. We believe that our angle-resolved far-field measurement scheme provides a way to investigate and evaluate the physical properties and performance of nano-optical materials and phenomena.

Radiative transfer in a sphere illuminated by a parallel beam - An integral equation approach. [in planetary atmosphere

NASA Technical Reports Server (NTRS)

Shia, R.-L.; Yung, Y. L.

1986-01-01

The problem of multiple scattering of nonpolarized light in a planetary body of arbitrary shape illuminated by a parallel beam is formulated using the integral equation approach. There exists a simple functional whose stationarity condition is equivalent to solving the equation of radiative transfer and whose value at the stationary point is proportional to the differential cross section. The analysis reveals a direct relation between the microscopic symmetry of the phase function for each scattering event and the macroscopic symmetry of the differential cross section for the entire planetary body, and the interconnection of these symmetry relations and the variational principle. The case of a homogeneous sphere containing isotropic scatterers is investigated in detail. It is shown that the solution can be expanded in a multipole series such that the general spherical problem is reduced to solving a set of decoupled integral equations in one dimension. Computations have been performed for a range of parameters of interest, and illustrative examples of applications to planetary problems as provided.

Er{sup 3+}-doped strontium lithium bismuth borate glasses for broadband 1.5 {mu}m emission - optical properties

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

Rajesh, D.; Balakrishna, A.; Ratnakaram, Y. C.

2013-02-05

Strontium lithium bismuth borate glasses (SLBiB) doped with various concentrations of Er{sup 3+} were prepared using conventional melt quench technique and investigated their optical properties. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction and SEM analysis. Optical properties were studied by measuring the optical absorption and near infrared luminescence spectra at room temperature. Judd-Ofelt (J-O) theory has been applied for the f.f transitions of Er{sup 3+} ions to evaluate J-O intensity parameters, {Omega}{lambda} ({lambda} = 2, 4 and 6). Using the J-O intensity parameters, radiative properties such as transition probabilities (A{sub R}), branching ratios ({beta})more » and radiative lifetimes ({tau}) are estimated for certain transitions. From the emission spectra, peak emission-cross sections ({sigma}{sub p}) and products of stimulated emission cross-section and full width at half maximum ({sigma}{sub p} Multiplication-Sign FWHM) were calculated for the observed emission transition, {sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2}.« less

Radiation and scattering from bodies of translation, volume 1

NASA Astrophysics Data System (ADS)

Medgyesi-Mitschang, L. N.

1980-04-01

An analytical formulation, based on the method of moments (MM) is described for solving electromagnetic problems associated with finite-length cylinders of arbitrary cross section, denoted in this report as bodies of translation (BOT). This class of bodies can be used to model structures with noncircular cross sections such as wings, fins, and aircraft fuselages. The theoretical development parallels in part the MM formulation developed earlier by Mautz and Harrington for bodies of revolution (BOR). Like the latter approach, a modal expansion is used to describe the unknown surface currents on the BOT. The present analysis has been developed to treat the far-field radiation and scattering from a BOT excited by active antennas or illuminated by a plane wave of arbitrary polarization and angle of incidence. In addition, the electric and magnetic near-field components are determined in the vicinity of active and passive apertures (slots). Using the Schelkunoff equivalence theorem, the aperture-coupled fields within a BOT are also obtained. The formulation has been implemented by a computer algorithm and validated using accepted data in the literature.

Efficient computation of coherent synchrotron radiation in a rectangular chamber

NASA Astrophysics Data System (ADS)

Warnock, Robert L.; Bizzozero, David A.

2016-09-01

We study coherent synchrotron radiation (CSR) in a perfectly conducting vacuum chamber of rectangular cross section, in a formalism allowing an arbitrary sequence of bends and straight sections. We apply the paraxial method in the frequency domain, with a Fourier development in the vertical coordinate but with no other mode expansions. A line charge source is handled numerically by a new method that rids the equations of singularities through a change of dependent variable. The resulting algorithm is fast compared to earlier methods, works for short bunches with complicated structure, and yields all six field components at any space-time point. As an example we compute the tangential magnetic field at the walls. From that one can make a perturbative treatment of the Poynting flux to estimate the energy deposited in resistive walls. The calculation was motivated by a design issue for LCLS-II, the question of how much wall heating from CSR occurs in the last bend of a bunch compressor and the following straight section. Working with a realistic longitudinal bunch form of r.m.s. length 10.4 μ m and a charge of 100 pC we conclude that the radiated power is quite small (28 W at a 1 MHz repetition rate), and all radiated energy is absorbed in the walls within 7 m along the straight section.

Extracting concentrated guided light.

PubMed

Ries, H; Segal, A; Karni, J

1997-05-01

The maximum concentration of radiation is proportional to the square of the refractive index of the medium in which it propagates. A medium with a high refractive index can also serve as a lightguide for concentrated radiation. However, if concentrated radiation is extracted from one medium, with a high refractive index, to another, whose index is lower (e.g., from fused silica into air), part of the radiation may be lost because of the total internal reflection at the interface. We present polygonal shapes suitable for efficient extraction of the concentrated radiation in a controllable way, without increasing the cross-section area (or diameter) of the lightguide. It is shown analytically and experimentally that the use of a secondary concentrator, followed by such a light extractor, both having a high refractive index, can provide considerably more power to a solar receiver with a specific aperture.

Merging weak and QCD showers with matrix elements

DOE PAGES

Christiansen, Jesper Roy; Prestel, Stefan

2016-01-22

In this study, we present a consistent way of combining associated weak boson radiation in hard dijet events with hard QCD radiation in Drell–Yan-like scatterings. This integrates multiple tree-level calculations with vastly different cross sections, QCD- and electroweak parton-shower resummation into a single framework. The new merging strategy is implemented in the P ythia event generator and predictions are confronted with LHC data. Improvements over the previous strategy are observed. Results of the new electroweak-improved merging at a future 100 TeV proton collider are also investigated.

Origin of reverse annealing in radiation-damaged silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.

1980-01-01

The paper employs relative defect concentrations, energy levels, capture cross sections, and minority carrier diffusion lengths in order to identify the defect responsible for the reverse annealing observed in a radiation damaged n(+)/p silicon solar cell. It is reported that the responsible defect, with the energy level at +0.30 eV, has been tentatively identified as boron-oxygen-vacancy complex. In conclusion, it is shown that removal of this defect could result in significant cell recovery when annealing at temperatures well below the currently required 400 C.

On the measurement of Rayleigh scattering by gases at 6328A

NASA Technical Reports Server (NTRS)

SHARDANAND; Gupta, S. K.

1973-01-01

The problem of laboratory measurements of Rayleigh scattering and depolarization ratio for atoms and molecules in the gaseous state is described. It is shown that, if the scattered radiation measurements are made at two angles, the normal depolarization ratio cannot be determined meaningfully. However, from scattering measurements, the Rayleigh scattering cross sections can be determined accurately. The measurements of Raleigh scattering from He, H2, Ar, O2, and N2 for unpolarized radiation at 6328A are reported and compared with similar measurements at 6943 and 1215.7A.

Merging weak and QCD showers with matrix elements

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

Christiansen, Jesper Roy; Prestel, Stefan

In this study, we present a consistent way of combining associated weak boson radiation in hard dijet events with hard QCD radiation in Drell–Yan-like scatterings. This integrates multiple tree-level calculations with vastly different cross sections, QCD- and electroweak parton-shower resummation into a single framework. The new merging strategy is implemented in the P ythia event generator and predictions are confronted with LHC data. Improvements over the previous strategy are observed. Results of the new electroweak-improved merging at a future 100 TeV proton collider are also investigated.

Mobile technology and social media in the clinical practice of young radiation oncologists: results of a comprehensive nationwide cross-sectional study.

PubMed

Bibault, Jean-Emmanuel; Leroy, Thomas; Blanchard, Pierre; Biau, Julian; Cervellera, Mathilde; Diaz, Olivia; Faivre, Jean Christophe; Fumagalli, Ingrid; Lescut, Nicolas; Martin, Valentine; Pichon, Baptiste; Riou, Olivier; Thureau, Sébastien; Giraud, Philippe

2014-09-01

Social media and mobile technology are transforming the way in which young physicians are learning and practicing medicine. The true impact of such technologies has yet to be evaluated. We performed a nationwide cross-sectional survey to better assess how young radiation oncologists used these technologies. An online survey was sent out between April 24, 2013, and June 1, 2013. All residents attending the 2013 radiation oncology French summer course were invited to complete the survey. Logistic regressions were performed to assess predictors of use of these tools in the hospital on various clinical endpoints. In all, 131 of 140 (93.6%) French young radiation oncologists answered the survey. Of these individuals, 93% owned a smartphone and 32.8% owned a tablet. The majority (78.6%) of the residents owning a smartphone used it to work in their department. A total of 33.5% had more than 5 medical applications installed. Only 60.3% of the residents verified the validity of the apps that they used. In all, 82.9% of the residents had a social network account. Most of the residents in radiation oncology use their smartphone to work in their department for a wide variety of tasks. However, the residents do not consistently check the validity of the apps that they use. Residents also use social networks, with only a limited impact on their relationship with their patients. Overall, this study highlights the irruption and the risks of new technologies in the clinical practice and raises the question of a possible regulation of their use in the hospital. Copyright © 2014 Elsevier Inc. All rights reserved.

Mobile Technology and Social Media in the Clinical Practice of Young Radiation Oncologists: Results of a Comprehensive Nationwide Cross-sectional Study

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

Bibault, Jean-Emmanuel, E-mail: jebibault@gmail.com; French Society of Young Radiation Oncologists; Leroy, Thomas

Purpose: Social media and mobile technology are transforming the way in which young physicians are learning and practicing medicine. The true impact of such technologies has yet to be evaluated. Methods and Materials: We performed a nationwide cross-sectional survey to better assess how young radiation oncologists used these technologies. An online survey was sent out between April 24, 2013, and June 1, 2013. All residents attending the 2013 radiation oncology French summer course were invited to complete the survey. Logistic regressions were performed to assess predictors of use of these tools in the hospital on various clinical endpoints. Results: Inmore » all, 131 of 140 (93.6%) French young radiation oncologists answered the survey. Of these individuals, 93% owned a smartphone and 32.8% owned a tablet. The majority (78.6%) of the residents owning a smartphone used it to work in their department. A total of 33.5% had more than 5 medical applications installed. Only 60.3% of the residents verified the validity of the apps that they used. In all, 82.9% of the residents had a social network account. Conclusions: Most of the residents in radiation oncology use their smartphone to work in their department for a wide variety of tasks. However, the residents do not consistently check the validity of the apps that they use. Residents also use social networks, with only a limited impact on their relationship with their patients. Overall, this study highlights the irruption and the risks of new technologies in the clinical practice and raises the question of a possible regulation of their use in the hospital.« less

A waveguide finite element aided analysis of the wave field on a stationary tyre, not in contact with the ground

NASA Astrophysics Data System (ADS)

Sabiniarz, Patrick; Kropp, Wolfgang

2010-07-01

Although tyre/road noise has been a research subject for more than three decades, there is still no consensus in the literature as to which waves on a tyre are mainly responsible for the radiation of sound during rolling. Even the free vibrational behaviour of a stationary (non-rotating) tyre, not in contact with the ground, is still not well understood in the mid- and high-frequency ranges. Thus, gaining an improved understanding of this behaviour is a natural first step towards illuminating the question of which waves on a rolling tyre contribute to sound radiation. This is the topic of the present paper, in which a model based on the waveguide finite element method (WFEM) is used to study free wave propagation, on a stationary tyre, in the range 0-1500 Hz. In the low-frequency region (0-300 Hz), wave propagation is found to be rather straightforward, with two main wave-types present. Both have cross-section modes involving a nearly rigid motion of the belt. For higher frequencies (300-1500 Hz) the behaviour is more complex, including phenomena such as 'curve veering' and waves for which the phase speed and group speed have opposite signs. Wave-types identified in this region include (i) waves involving mainly sidewall deformation, (ii) belt bending waves, (iii) a wave with significant extensional deformation of the central belt region and (iv) a wave with a 'breathing' cross-section mode. The phase speed corresponding to found waves is computed and their radiation efficiency is discussed, assuming free-field conditions. In a future publication, the tyre model will be used in conjunction with a contact model and a radiation model to investigate the contribution of these waves to radiated sound during rolling.

Comment on "Radiative forcings for 28 potential Archean greenhouse gases" by Byrne and Goldblatt (2014)

DOE PAGES

Kochanov, R. V.; Gordon, I. E.; Rothman, L. S.; ...

2015-08-25

In the recent article by Byrne and Goldblatt, "Radiative forcing for 28 potential Archean greenhouse gases", Clim. Past. 10, 1779–1801 (2014), the authors employ the HITRAN2012 spectroscopic database to evaluate the radiative forcing of 28 Archean gases. As part of the evaluation of the status of the spectroscopy of these gases in the selected spectral region (50–1800 cm -1), the cross sections generated from the HITRAN line-by-line parameters were compared with those of the PNNL database of experimental cross sections recorded at moderate resolution. The authors claimed that for NO 2, HNO 3, H 2CO, H 2O 2, HCOOH, Cmore » 2H 4, CH 3OH and CH 3Br there exist large or sometimes severe disagreements between the databases. In this work we show that for only three of these eight gases a modest discrepancy does exist between the two databases and we explain the origin of the differences. For the other five gases, the disagreements are not nearly at the scale suggested by the authors, while we explain some of the differences that do exist. In summary, the agreement between the HITRAN and PNNL databases is very good, although not perfect. Typically differences do not exceed 10 %, provided that HITRAN data exist for the bands/wavelengths of interest. It appears that a molecule-dependent combination of errors has affected the conclusions of the authors. In at least one case it appears that they did not take the correct file from PNNL (N 2O 4 (dimer)+ NO 2 was used in place of the monomer). Finally, cross sections of HO 2 from HITRAN (which do not have a PNNL counterpart) were not calculated correctly in BG, while in the case of HF misleading discussion was presented there based on the confusion by foreign or noise features in the experimental PNNL spectra.« less

Design of a synchrotron radiation detector for the test beam lines at the Superconducting Super Collider Laboratory

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

Hutton, R.D.

1994-01-01

As part of the particle- and momentum-tagging instrumentation required for the test beam lines of the Superconducting Super Collider (SSC), the synchrotron radiation detector (SRD) was designed to provide electron tagging at momentum above 75 GeV. In a parallel effort to the three test beam lines at the SSC, schedule demands required testing and calibration operations to be initiated at Fermilab. Synchrotron radiation detectors also were to be installed in the NM and MW beam lines at Femilab before the test beam lines at the SSC would become operational. The SRD is the last instrument in a series of threemore » used in the SSC test beam fines. It follows a 20-m drift section of beam tube downstream of the last silicon strip detector. A bending dipole just in of the last silicon strip detector produces the synchrotron radiation that is detected in a 50-mm-square cross section NaI crystal. A secondary scintillator made of Bicron BC-400 plastic is used to discriminate whether it is synchrotron radiation or a stray particle that causes the triggering of the NaI crystal`s photo multiplier tube (PMT).« less

Feasibility of in Vivo SAXS Imaging for Detection of Alzheiemer's Disease

NASA Astrophysics Data System (ADS)

Choi, Mina

Small-angle x-ray scattering (SAXS) imaging has been proposed as a technique to characterize and selectively image structures based on electron density structure which allows for discriminating materials based on their scatter cross sections. This dissertation explores the feasibility of SAXS imaging for the detection of Alzheimer's disease (AD) amyloid plaques. The inherent scatter cross sections of amyloid plaque serve as biomarkers in vivo without the need of injected molecular tags. SAXS imaging can also assist in a better understanding of how these biomarkers play a role in Alzheimer's disease which in turn can lead to the development of more effective disease-modifying therapies. I implement simulations of x-ray transport using Monte Carlo methods for SAXS imaging enabling accurate calculation of radiation dose and image quality in SAXS-computed tomography (CT). I describe SAXS imaging phantoms with tissue-mimicking material and embedded scatter targets as a way of demonstrating the characteristics of SAXS imaging. I also performed a comprehensive study of scattering cross sections of brain tissue from measurements of ex-vivo sections of a wild-type mouse brain and reported generalized cross sections of gray matter, white matter, and corpus callosum obtained and registered by planar SAXS imaging. Finally, I demonstrate the ability of SAXS imaging to locate an amyloid fibril pellet within a brain section. This work contributes to novel application of SAXS imaging for Alzheimer's disease detection and studies its feasibility as an imaging tool for AD biomarkers.

Nonelastic nuclear reactions and accompanying gamma radiation

NASA Technical Reports Server (NTRS)

Snow, R.; Rosner, H. R.; George, M. C.; Hayes, J. D.

1971-01-01

Several aspects of nonelastic nuclear reactions which proceed through the formation of a compound nucleus are dealt with. The full statistical model and the partial statistical model are described and computer programs based on these models are presented along with operating instructions and input and output for sample problems. A theoretical development of the expression for the reaction cross section for the hybrid case which involves a combination of the continuum aspects of the full statistical model with the discrete level aspects of the partial statistical model is presented. Cross sections for level excitation and gamma production by neutron inelastic scattering from the nuclei Al-27, Fe-56, Si-28, and Pb-208 are calculated and compared with avaliable experimental data.

The Computerized Anatomical Man (CAM) model

NASA Technical Reports Server (NTRS)

Billings, M. P.; Yucker, W. R.

1973-01-01

A computerized anatomical man (CAM) model, representing the most detailed and anatomically correct geometrical model of the human body yet prepared, has been developed for use in analyzing radiation dose distribution in man. This model of a 50-percentile standing USAF man comprises some 1100 unique geometric surfaces and some 2450 solid regions. Internal body geometry such as organs, voids, bones, and bone marrow are explicitly modeled. A computer program called CAMERA has also been developed for performing analyses with the model. Such analyses include tracing rays through the CAM geometry, placing results on magnetic tape in various forms, collapsing areal density data from ray tracing information to areal density distributions, preparing cross section views, etc. Numerous computer drawn cross sections through the CAM model are presented.

Broadband computation of the scattering coefficients of infinite arbitrary cylinders.

PubMed

Blanchard, Cédric; Guizal, Brahim; Felbacq, Didier

2012-07-01

We employ a time-domain method to compute the near field on a contour enclosing infinitely long cylinders of arbitrary cross section and constitution. We therefore recover the cylindrical Hankel coefficients of the expansion of the field outside the circumscribed circle of the structure. The recovered coefficients enable the wideband analysis of complex systems, e.g., the determination of the radar cross section becomes straightforward. The prescription for constructing such a numerical tool is provided in great detail. The method is validated by computing the scattering coefficients for a homogeneous circular cylinder illuminated by a plane wave, a problem for which an analytical solution exists. Finally, some radiation properties of an optical antenna are examined by employing the proposed technique.

Measurement of the e+e-→π+π-J/ψ Cross Section Via Initial-State Radiation at Belle

NASA Astrophysics Data System (ADS)

Yuan, C. Z.; Shen, C. P.; Wang, P.; McOnie, S.; Adachi, I.; Aihara, H.; Aulchenko, V.; Aushev, T.; Bahinipati, S.; Balagura, V.; Barberio, E.; Bedny, I.; Bitenc, U.; Bondar, A.; Bozek, A.; Bračko, M.; Brodzicka, J.; Browder, T. E.; Chang, M.-C.; Chang, P.; Chen, A.; Chen, K.-F.; Chen, W. T.; Cheon, B. G.; Chistov, R.; Cho, I.-S.; Choi, Y.; Dalseno, J.; Danilov, M.; Dash, M.; Eidelman, S.; Fratina, S.; Gabyshev, N.; Golob, B.; Ha, H.; Haba, J.; Hayasaka, K.; Hayashii, H.; Hazumi, M.; Heffernan, D.; Hokuue, T.; Hoshi, Y.; Hou, W.-S.; Hsiung, Y. B.; Hyun, H. J.; Iijima, T.; Ikado, K.; Inami, K.; Ishikawa, A.; Itoh, R.; Iwasaki, Y.; Kah, D. H.; Kaji, H.; Kang, J. H.; Katayama, N.; Kawai, H.; Kawasaki, T.; Kichimi, H.; Kim, Y. J.; Kinoshita, K.; Korpar, S.; Križan, P.; Krokovny, P.; Kumar, R.; Kuo, C. C.; Kuzmin, A.; Kwon, Y.-J.; Lee, S. E.; Lesiak, T.; Lin, S.-W.; Liu, Y.; Liventsev, D.; Mandl, F.; Marlow, D.; Matyja, A.; Medvedeva, T.; Mitaroff, W.; Miyabayashi, K.; Miyake, H.; Miyata, H.; Miyazaki, Y.; Mizuk, R.; Mori, T.; Nagasaka, Y.; Nakao, M.; Natkaniec, Z.; Nishida, S.; Nitoh, O.; Ogawa, S.; Ohshima, T.; Okuno, S.; Olsen, S. L.; Ozaki, H.; Pakhlov, P.; Pakhlova, G.; Palka, H.; Park, H.; Park, K. S.; Peak, L. S.; Piilonen, L. E.; Sakai, Y.; Schneider, O.; Schümann, J.; Seidl, R.; Senyo, K.; Sevior, M. E.; Shapkin, M.; Shibuya, H.; Shiu, J.-G.; Shwartz, B.; Singh, J. B.; Sokolov, A.; Somov, A.; Starič, M.; Sumiyoshi, T.; Takasaki, F.; Tanaka, M.; Taylor, G. N.; Teramoto, Y.; Tikhomirov, I.; Uehara, S.; Unno, Y.; Uno, S.; Usov, Y.; Varner, G.; Varvell, K. E.; Vervink, K.; Villa, S.; Vinokurova, A.; Wang, C. C.; Wang, C. H.; Wang, X. L.; Watanabe, Y.; Won, E.; Yabsley, B. D.; Yamaguchi, A.; Yamashita, Y.; Zhang, C. C.; Zhang, Z. P.; Zhilich, V.; Zhulanov, V.; Zupanc, A.

2007-11-01

The cross section for e+e-→π+π-J/ψ between 3.8 and 5.5GeV/c2 is measured using a 548fb-1 data sample collected on or near the Υ(4S) resonance with the Belle detector at KEKB. A peak near 4.25GeV/c2, corresponding to the so called Y(4260), is observed. In addition, there is another cluster of events at around 4.05GeV/c2. A fit using two interfering Breit-Wigner shapes describes the data better than one that uses only the Y(4260), especially for the lower-mass side of the 4.25 GeV enhancement.

Measurement of the radiative capture cross section of the s-process branching points 204Tl and 171Tm at the n_TOF facility (CERN)

NASA Astrophysics Data System (ADS)

Casanovas, A.; Domingo-Pardo, C.; Guerrero, C.; Lerendegui-Marco, J.; Calviño, F.; Tarifeño-Saldivia, A.; Dressler, R.; Heinitz, S.; Kivel, N.; Quesada, J. M.; Schumann, D.; Aberle, O.; Alcayne, V.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Bacak, M.; Barbagallo, M.; Bečvář, F.; Bellia, G.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Busso, M.; Caamaño, M.; Caballero-Ontanaya, L.; Calviani, M.; Cano-Ott, D.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Diakaki, M.; Dietz, M.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Furman, V.; Göbel, K.; Gawlik, A.; Gilardoni, S.; Glodariu, T.; Gonçalves, I. F.; González-Romero, E.; Gunsing, F.; Heyse, J.; Jenkins, D. G.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kimura, A.; Kokkoris, M.; Kopatch, Y.; Krtička, M.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; Meo, S. Lo; Lonsdale, S. J.; Macina, D.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Mingrone, F.; Musumarra, A.; Negret, A.; Nolte, R.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Persanti, L.; Porras, I.; Praena, J.; Radeck, D.; Ramos, D.; Rauscher, T.; Reifarth, R.; Rochman, D.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Simone, S.; Smith, A. G.; Sosnin, N. V.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Talip, T.; Tassan-Got, L.; Tsinganis, A.; Ulrich, J.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T.; Žugec, P.; Köster, U.

2018-05-01

The neutron capture cross section of some unstable nuclei is especially relevant for s-process nucleosynthesis studies. This magnitude is crucial to determine the local abundance pattern, which can yield valuable information of the s-process stellar environment. In this work we describe the neutron capture (n,γ) measurement on two of these nuclei of interest, 204Tl and 171Tm, from target production to the final measurement, performed successfully at the n_TOF facility at CERN in 2014 and 2015. Preliminary results on the ongoing experimental data analysis will also be shown. These results include the first ever experimental observation of capture resonances for these two nuclei.

Radiative transfer theory for active remote sensing of a layer of small ellipsoidal scatterers. [of vegetation

NASA Technical Reports Server (NTRS)

Tsang, L.; Kubacsi, M. C.; Kong, J. A.

1981-01-01

The radiative transfer theory is applied within the Rayleigh approximation to calculate the backscattering cross section of a layer of randomly positioned and oriented small ellipsoids. The orientation of the ellipsoids is characterized by a probability density function of the Eulerian angles of rotation. The radiative transfer equations are solved by an iterative approach to first order in albedo. In the half space limit the results are identical to those obtained via the approach of Foldy's and distorted Born approximation. Numerical results of the theory are illustrated using parameters encountered in active remote sensing of vegetation layers. A distinctive characteristic is the strong depolarization shown by vertically aligned leaves.

Long titanium heat pipes for high-temperature space radiators

NASA Technical Reports Server (NTRS)

Girrens, S. P.; Ernst, D. M.

1982-01-01

Titanium heat pipes are being developed to provide light weight, reliable heat rejection devices as an alternate radiator design for the Space Reactor Power System (SP-100). The radiator design includes 360 heat pipes, each of which is 5.2 m long and dissipates 3 kW of power at 775 K. The radiator heat pipes use potassium as the working fluid, have two screen arteries for fluid return, a roughened surface distributive wicking system, and a D shaped cross section container configuration. A prototype titanium heat pipe, 5.5 m long, was fabricated and tested in space simulating conditions. Results from startup and isothermal operation tests are presented. These results are also compared to theoretical performance predictions that were used to design the heat pipe initially.

Long titanium heat pipes for high-temperature space radiators

NASA Technical Reports Server (NTRS)

Girrens, S. P.; Ernst, D. M.

1982-01-01

Titanium heat pipes are being developed to provide light weight, reliable heat rejection devices as an alternate radiator design for the Space Reactor Power System (SP-100). The radiator design includes 360 heat pipes, each of which is 5.2 m long and dissipates 3 kW of power at 775 K. The radiator heat pipes use potassium as the working fluid, have two screen arteries for fluid return, a roughened surface distributive wicking system, and a D-shaped cross-section container configuration. A prototype titanium heat pipe, 5.5-m long, has been fabricated and tested in space-simulating conditions. Results from startup and isothermal operation tests are presented. These results are also compared to theoretical performance predictions that were used to design the heat pipe initially.

Modelling of micromachining of human tooth enamel by erbium laser radiation

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

Belikov, A V; Skrypnik, A V; Shatilova, K V

We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength betweenmore » the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained. (laser biophotonics)« less

Diffuse reflectance of TiO 2 pigmented paints: Spectral dependence of the average pathlength parameter and the forward scattering ratio

NASA Astrophysics Data System (ADS)

Vargas, William E.; Amador, Alvaro; Niklasson, Gunnar A.

2006-05-01

Diffuse reflectance spectra of paint coatings with different pigment concentrations, normally illuminated with unpolarized radiation, have been measured. A four-flux radiative transfer approach is used to model the diffuse reflectance of TiO2 (rutile) pigmented coatings through the solar spectral range. The spectral dependence of the average pathlength parameter and of the forward scattering ratio for diffuse radiation, are explicitly incorporated into this four-flux model from two novel approximations. The size distribution of the pigments has been taken into account to obtain the averages of the four-flux parameters: scattering and absorption cross sections, forward scattering ratios for collimated and isotropic diffuse radiation, and coefficients involved in the expansion of the single particle phase function in terms of Legendre polynomials.

An integrated radiation physics computer code system.

NASA Technical Reports Server (NTRS)

Steyn, J. J.; Harris, D. W.

1972-01-01

An integrated computer code system for the semi-automatic and rapid analysis of experimental and analytic problems in gamma photon and fast neutron radiation physics is presented. Such problems as the design of optimum radiation shields and radioisotope power source configurations may be studied. The system codes allow for the unfolding of complex neutron and gamma photon experimental spectra. Monte Carlo and analytic techniques are used for the theoretical prediction of radiation transport. The system includes a multichannel pulse-height analyzer scintillation and semiconductor spectrometer coupled to an on-line digital computer with appropriate peripheral equipment. The system is geometry generalized as well as self-contained with respect to material nuclear cross sections and the determination of the spectrometer response functions. Input data may be either analytic or experimental.

Extension of On-Surface Radiation Condition (OSRC) theory to full-vector electromagnetic wave scattering by three-dimensional conducting, dielectric, and coated targets

NASA Astrophysics Data System (ADS)

Taflove, Allen; Umashankar, Korada R.

1993-08-01

This project introduced radiation boundary condition (RBC) and absorbing boundary condition (ABC) theory to the engineering electromagnetics community. An approximate method for obtaining the scattering of 2-D and 3-D bodies, the on-surface radiation condition (OSRC) method, was formulated and validated. RBC's and ABC's were shown to work well at points closer to scatterers than anyone had expected. Finite-difference time domain (FD-TD) methods exploiting these ABC's were pursued for applications in scattering, radiation, penetration, biomedical studies, and nonlinear optics. Multiprocessing supercomputer software was developed for FD-TD, leading to the largest scale detailed electromagnetic wave interaction models ever conducted, including entire jet fighter aircraft modeled for radar cross section (RCS) at UHF frequencies up to 500 MHz.

Atomic and molecular physics in the gas phase

NASA Astrophysics Data System (ADS)

Toburen, L. H.

1990-09-01

The spatial and temporal distributions of energy deposition by high-linear-energy-transfer radiation play an important role in the subsequent chemical and biological processes leading to radiation damage. Because the spatial structures of energy deposition events are of the same dimensions as molecular structures in the mammalian cell, direct measurements of energy deposition distributions appropriate to radiation biology are infeasible. This has led to the development of models of energy transport based on a knowledge of atomic and molecular interactions process that enable one to simulate energy transfer on an atomic scale. Such models require a detailed understanding of the interactions of ions and electrons with biologically relevant material. During the past 20 years there has been a great deal of progress in our understanding of these interactions; much of it coming from studies in the gas phase. These studies provide information on the systematics of interaction cross sections leading to a knowledge of the regions of energy deposition where molecular and phase effects are important and that guide developments in appropriate theory. In this report studies of the doubly differential cross sections, crucial to the development of stochastic energy deposition calculations and track structure simulation, will be reviewed. Areas of understanding are discussed and directions for future work addressed. Particular attention is given to experimental and theoretical findings that have changed the traditional view of secondary electron production for charged particle interactions with atomic and molecular targets.

Fast X-Ray Fluorescence Microtomography of Hydrated Biological Samples

PubMed Central

Lombi, Enzo; de Jonge, Martin D.; Donner, Erica; Kopittke, Peter M.; Howard, Daryl L.; Kirkham, Robin; Ryan, Chris G.; Paterson, David

2011-01-01

Metals and metalloids play a key role in plant and other biological systems as some of them are essential to living organisms and all can be toxic at high concentrations. It is therefore important to understand how they are accumulated, complexed and transported within plants. In situ imaging of metal distribution at physiological relevant concentrations in highly hydrated biological systems is technically challenging. In the case of roots, this is mainly due to the possibility of artifacts arising during sample preparation such as cross sectioning. Synchrotron x-ray fluorescence microtomography has been used to obtain virtual cross sections of elemental distributions. However, traditionally this technique requires long data acquisition times. This has prohibited its application to highly hydrated biological samples which suffer both radiation damage and dehydration during extended analysis. However, recent advances in fast detectors coupled with powerful data acquisition approaches and suitable sample preparation methods can circumvent this problem. We demonstrate the heightened potential of this technique by imaging the distribution of nickel and zinc in hydrated plant roots. Although 3D tomography was still impeded by radiation damage, we successfully collected 2D tomograms of hydrated plant roots exposed to environmentally relevant metal concentrations for short periods of time. To our knowledge, this is the first published example of the possibilities offered by a new generation of fast fluorescence detectors to investigate metal and metalloid distribution in radiation-sensitive, biological samples. PMID:21674049

Measurements of Atomic Rayleigh Scattering Cross-Sections: A New Approach Based on Solid Angle Approximation and Geometrical Efficiency

NASA Astrophysics Data System (ADS)

Rao, D. V.; Takeda, T.; Itai, Y.; Akatsuka, T.; Seltzer, S. M.; Hubbell, J. H.; Cesareo, R.; Brunetti, A.; Gigante, G. E.

Atomic Rayleigh scattering cross-sections for low, medium and high Z atoms are measured in vacuum using X-ray tube with a secondary target as an excitation source instead of radioisotopes. Monoenergetic Kα radiation emitted from the secondary target and monoenergetic radiation produced using two secondary targets with filters coupled to an X-ray tube are compared. The Kα radiation from the second target of the system is used to excite the sample. The background has been reduced considerably and the monochromacy is improved. Elastic scattering of Kα X-ray line energies of the secondary target by the sample is recorded with Hp Ge and Si (Li) detectors. A new approach is developed to estimate the solid angle approximation and geometrical efficiency for a system with experimental arrangement using X-ray tube and secondary target. The variation of the solid angle is studied by changing the radius and length of the collimators towards and away from the source and sample. From these values the variation of the total solid angle and geometrical efficiency is deduced and the optimum value is used for the experimental work. The efficiency is larger because the X-ray fluorescent source acts as a converter. Experimental results based on this system are compared with theoretical estimates and good agreement is observed in between them.

Cross Section Calculations and Comparison to Experiment

NASA Technical Reports Server (NTRS)

Townsend, L. W.; Ford, W. P.; Dewet, W. C.; Werneth, C. M.

2016-01-01

Understanding fragmentation of galactic cosmic ray nuclei in collisions within spacecraft structures and human tissues is an important element in assessing biological risk to crew members from this radiation source. Over the past four decades, various models have been developed to describe these important processes. Some models invoke semi-classical concepts based upon geometric descriptions of collisions between spherical nuclei.

How to assess good candidate molecules for self-activated optical power limiting

NASA Astrophysics Data System (ADS)

Lundén, Hampus; Glimsdal, Eirik; Lindgren, Mikael; Lopes, Cesar

2018-03-01

Reverse saturable absorbers have shown great potential to attenuate laser radiation. Good candidate molecules and various particles have successfully been incorporated into different glass matrices, enabling the creation of self-activated filters against damaging laser radiation. Although the performance of such filters has been impressive, work is still ongoing to improve the performance in a wider range of wavelengths and pulse widths. The purpose of this tutorial is, from an optical engineering perspective, to give an understanding of the strengths and weaknesses of this class of smart materials, how relevant photophysical parameters are measured and influence system performance and comment on the pitfalls in experimental evaluation of materials. A numerical population model in combination with simple physical formulas is used to demonstrate system behavior from a performance standpoint. Geometrical reasoning shows the advantage of reverse saturable absorption over nonlinear scattering due to a fraction of scattered light being recollected by imaging system optics. The numerical population model illustrates the importance of the optical power limiting performance during the leading edge of a nanosecond pulse, which is most strongly influenced by changes in the two-photon absorption cross section and the triplet linear absorption cross section for a modeled Pt-acetylide. This tutorial not only targets optical engineers evaluating reverse saturable absorbing materials but also aims to assist researchers with a chemistry background working on optical power limiting materials. We also present photophysical data for a series of coumarins that can be useful for the determination of quantum yields and two-photon cross sections and show examples of characterization of molecules with excited triplet states.

Viking Lander image analysis of Martian atmospheric dust

NASA Technical Reports Server (NTRS)

Pollack, James B.; Ockert-Bell, Maureen E.; Shepard, Michael K.

1995-01-01

We have reanalyzed three sets of Viking Lander 1 and 2 (VL1 and VL2) images of the Martian atmosphere to better evaluate the radiative properties of the atmospheric dust particles. The properties of interest are the first two moments of the size distribution, the single-scattering albedo, the dust single-scattering phase function, and the imaginary index of refraction. These properties provide a good definition of the influence that the atmospheric dust has on heating of the atmosphere. Our analysis represents a significant improvement over past analyses (Pollack et al. 1977, 1979) by deriving more accurate brightness closer to the sun, by carrying out more precise analyses of the data to acquire the quantities of interest, and by using a better representation of scattering by nonspherical particles. The improvements allow us to better define the diffraction peak and hence the size distribution of the particles. For a lognormal particle size distribution, the first two moments of the size distribution, weighted by the geometric cross section, are found. The geometric cross-section weighted mean radius r(sub eff) is found to be 1.85 +/- 0.3 micrometers at VL2 during northern summer when dust loading was low and 1.52 +/- 0.3 micrometers at VL1 during the first dust storm. In both cases the best cross-section weighted mean variance nu(sub eff) of the size distribution is equal to 0.5 +/- 0.2 micrometers. The changes in size distribution, and thus radiative properties, do not represent a substantial change in solar energy deposition in the atmosphere over the Pollak et al. (1977, 1979) estimates.

Viking Lander image analysis of Martian atmospheric dust

NASA Technical Reports Server (NTRS)

Pollack, James B.; Ockert-Bell, Maureen E.; Shepard, Michael K.

1995-01-01

We have reanalyzed three sets of Viking Lander 1 and 2 (VL1 and VL2) images of the Martian atmosphere to better evaluate the radiative properties of the atmospheric dust particles. The properties of interest are the first two moments of the size distribution, the single-scattering albedo, the dust single-scattering phase function, and the imaginary index of refraction. These properties provide a good definition of the influence that the atmospheric dust has on heating of the atmosphere. Our analysis represents a significant improvement over past analyses (Pollack et al. 1977,1979) by deriving more accurate brightnesses closer to the sun, by carrying out more precise analyses of the data to acquire the quantities of interest, and by using a better representation of scattering by nonspherical particles. The improvements allow us to better define the diffraction peak and hence the size distribution of the particles. For a lognormal particle size distribution, the first two moments of the size distribution, weighted by the geometric cross section, are found. The geometric cross-section weighted mean radius (r(sub eff)) is found to be 1.85 +/- 0.3 microns at VL2 during northern summer when dust loading was low and 1.52 +/- 0.3 microns at VL1 during the first dust storm. In both cases the best cross-section weighted mean variance (nu(eff)) of the size distribution is equal to 0.5 +/- 0.2 microns. The changes in size distribution, and thus radiative properties, do not represent a substantial change in solar energy deposition in the atmosphere over the Pollack et al. (1977,1979) estimates.

Measurement of the e + e - → π + π - π 0 π 0 cross section using initial-state radiation at BABAR

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

Lees, J. P.; Poireau, V.; Tisserand, V.

Here, the process e +e –→π +π –2π 0γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb –1 of data collected around a center-of-mass energy of √s=10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel’s contribution to the leading order hadronic vacuum polarization contribution to the anomalous magneticmore » moment of the muon is calculated as (gπ +π–2π0 μ–2)/2=(17.9 ± 0.1 stat ± 0.6 syst)×10–10 in the energy range 0.85 GeV < E CM < 1.8 GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z 0-pole is determined as Δαπ +π–2π0(M 2 Z)=(4.44 ± 0.02 stat ± 0.14 syst) × 10 –4. Furthermore, intermediate resonances are studied and especially the cross section of the process e +e –→ωπ 0→π +π –2π 0 is measured.« less

Variation of photoluminescence features in Pr{sup 3+} doped lithium-fluoro-borate glass by changing different modifier oxides (MgO, CaO, CdO and PbO)-Judd-Ofelt theory application

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

Balakrishna, A.; Rajesh, D.; Babu, S.

2015-06-24

Pr{sup 3+} (1.0 mol%) doped different modifier oxide based six lithium-fluoro-borate glasses with chemical composition of 49Li{sub 2}B{sub 4}O{sub 7}-20BaF{sub 2}-10NaF-20MO (where M= Mg, Ca, Cd and Pb), 49Li{sub 2}B{sub 4}O{sub 7}-20BaF{sub 2}-10NaF-10MgO-10CaO and 49Li{sub 2}B{sub 4}O{sub 7}-20BaF{sub 2}-10NaF-10CdO-10PbO were prepared by conventional melt quenching technique. Judd-Ofelt theory has been applied for evaluating the Judd-Ofelt intensity parameters for Pr{sup 3+} ion in these glass compositions and are in turn to used to predict radiative properties such as radiative transition probabilities (A{sub T}), branching ratios (β) and stimulated emission cross-section (σ{sub P}). Stimulated emission cross-section (σ{sub p}) of prominent emission transitions,more » {sup 3}P{sub 0}→{sup 3}H{sub 4} and {sup 1}D{sub 2}→{sup 3}H{sub 4} of Pr{sup 3+} ion in all lithium-fluoro-borate glasses were calculated. Among all the emission transitions, {sup 3}P{sub 0}→{sup 3}H{sub 4} posseses higher branching ratio and stimulated emission cross-section in Mg-Ca glass, which leads to the best laser excitation at 487 nm wavelength.« less

Measurement of the e + e - → π + π - π 0 π 0 cross section using initial-state radiation at BABAR

DOE PAGES

Lees, J. P.; Poireau, V.; Tisserand, V.; ...

2017-11-29

Here, the process e +e –→π +π –2π 0γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb –1 of data collected around a center-of-mass energy of √s=10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel’s contribution to the leading order hadronic vacuum polarization contribution to the anomalous magneticmore » moment of the muon is calculated as (gπ +π–2π0 μ–2)/2=(17.9 ± 0.1 stat ± 0.6 syst)×10–10 in the energy range 0.85 GeV < E CM < 1.8 GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z 0-pole is determined as Δαπ +π–2π0(M 2 Z)=(4.44 ± 0.02 stat ± 0.14 syst) × 10 –4. Furthermore, intermediate resonances are studied and especially the cross section of the process e +e –→ωπ 0→π +π –2π 0 is measured.« less

Lasing transition at 1.06 μm emission in Nd3+ -doped borate-based tellurium calcium zinc niobium oxide glasses for high-power solid-state lasers.

PubMed

Ravi, O; Prasad, K; Jain, Rajiv; Venkataswamy, M; Chaurasia, Shivanand; Deva Prasad Raju, B

2017-08-01

The spectroscopic properties of Tellurium Calcium Zinc Niobium oxide Borate (TCZNB) glasses of composition (in mol%) 10TeO 2  + 15CaO + 5ZnO + 10 Nb 2 O 5  + (60 - x)B 2 O 3  + Nd 2 O 3 (x = 0.1, 0.5, 1.0 or 1.5 mol%) have been investigated experimentally. The three phenomenological intensity parameters Ω 2 , Ω 4, Ω 6 have been calculated using the Judd-Ofelt theory and in turn radiative properties such as radiative transition probabilities, emission cross-sections, branching ratios and radiative lifetimes have been estimated. The trend found in the JO intensity parameter is Ω 2  > Ω 6  > Ω 4 If Ω 6  > Ω 4 , the glass system is favourable for the laser emission 4 F 3 /2  →  4 I 11 /2 in the infrared (IR) wavelength. The experimental values of branching ratio of 4 F 3 /2  →  4 I 11 /2 transition indicate favourable lasing action with low threshold power. The evaluated total radiative transition probabilities (A T ), stimulated emission cross-section (σ e ) and gain bandwidth parameters (σ e  × Δλ p ) were compared with earlier reports. An energy level analysis has been carried out considering the experimental energy positions of the absorption and emission bands. Copyright © 2016 John Wiley & Sons, Ltd.

Measurement of fragmentation cross sections of 12C ions on a thin gold target with the FIRST apparatus

NASA Astrophysics Data System (ADS)

Toppi, M.; Abou-Haidar, Z.; Agodi, C.; Alvarez, M. A. G.; Aumann, T.; Balestra, F.; Battistoni, G.; Bocci, A.; Böhlen, T. T.; Boudard, A.; Brunetti, A.; Carpinelli, M.; Cirio, R.; Cirrone, G. A. P.; Cortes-Giraldo, M. A.; Cuttone, G.; de Napoli, M.; Durante, M.; Fernández-García, J. P.; Finck, Ch.; Golosio, B.; Iarocci, E.; Iazzi, F.; Ickert, G.; Introzzi, R.; Juliani, D.; Krimmer, J.; Kummali, A. H.; Kurz, N.; Labalme, M.; Leifels, Y.; Le Fèvre, A.; Leray, S.; Marchetto, F.; Monaco, V.; Morone, M. C.; Nicolosi, D.; Oliva, P.; Paoloni, A.; Piersanti, L.; Pleskac, R.; Randazzo, N.; Rescigno, R.; Romano, F.; Rossi, D.; Rosso, V.; Rousseau, M.; Sacchi, R.; Sala, P.; Salvador, S.; Sarti, A.; Scheidenberger, C.; Schuy, C.; Sciubba, A.; Sfienti, C.; Simon, H.; Sipala, V.; Spiriti, E.; Tropea, S.; Vanstalle, M.; Younis, H.; Patera, V.; FIRST Collaboration

2016-06-01

A detailed knowledge of the light ions interaction processes with matter is of great interest in basic and applied physics. As an example, particle therapy and space radioprotection require highly accurate fragmentation cross-section measurements to develop shielding materials and estimate acute and late health risks for manned missions in space and for treatment planning in particle therapy. The Fragmentation of Ions Relevant for Space and Therapy experiment at the Helmholtz Center for Heavy Ion research (GSI) was designed and built by an international collaboration from France, Germany, Italy, and Spain for studying the collisions of a 12C ion beam with thin targets. The collaboration's main purpose is to provide the double-differential cross-section measurement of carbon-ion fragmentation at energies that are relevant for both tumor therapy and space radiation protection applications. Fragmentation cross sections of light ions impinging on a wide range of thin targets are also essential to validate the nuclear models implemented in MC simulations that, in such an energy range, fail to reproduce the data with the required accuracy. This paper presents the single differential carbon-ion fragmentation cross sections on a thin gold target, measured as a function of the fragment angle and kinetic energy in the forward angular region (θ ≲6° ), aiming to provide useful data for the benchmarking of the simulation softwares used in light ions fragmentation applications. The 12C ions used in the measurement were accelerated at the energy of 400 MeV/nucleon by the SIS (heavy ion synchrotron) GSI facility.

ROVIBRATIONALLY RESOLVED DIRECT PHOTODISSOCIATION THROUGH THE LYMAN AND WERNER TRANSITIONS OF H{sub 2} FOR FUV/X-RAY-IRRADIATED ENVIRONMENTS

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

Gay, C. D.; Porter, R. L.; Stancil, P. C.

Using ab initio potential curves and dipole transition moments, cross-section calculations were performed for the direct continuum photodissociation of H{sub 2} through the B{sup 1}{Sigma}{sup +}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Lyman) and C{sup 1}{Pi}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Werner) transitions. Partial cross-sections were obtained for wavelengths from 100 A to the dissociation threshold between the upper electronic state and each of the 301 bound rovibrational levels v''J'' within the ground electronic state. The resulting cross-sections are incorporated into three representative classes of interstellar gas models: diffuse clouds, photon-dominated regions, and X-ray-dominated regions (XDRs). The models, whichmore » used the CLOUDY plasma/molecular spectra simulation code, demonstrate that direct photodissociation is comparable to fluorescent dissociation (or spontaneous radiative dissociation, the Solomon process) as an H{sub 2} destruction mechanism in intense far-ultraviolet or X-ray-irradiated gas. In particular, changes in H{sub 2} rotational column densities are found to be as large as 20% in the XDR model with the inclusion of direct photodissociation. The photodestruction rate from some high-lying rovibrational levels can be enhanced by pumping from H Ly{beta} due to a wavelength coincidence with cross-section resonances resulting from quasi-bound levels of the upper electronic states. Given the relatively large size of the photodissociation data set, a strategy is described to create truncated, but reliable, cross-section data consistent with the wavelength resolving power of typical observations.« less

Effects of track structure and cell inactivation on the calculation of heavy ion mutation rates in mammalian cells

NASA Technical Reports Server (NTRS)

Cucinotta, F. A.; Wilson, J. W.; Shavers, M. R.; Katz, R.

1996-01-01

It has long been suggested that inactivation severely effects the probability of mutation by heavy ions in mammalian cells. Heavy ions have observed cross sections of inactivation that approach and sometimes exceed the geometric size of the cell nucleus in mammalian cells. In the track structure model of Katz the inactivation cross section is found by summing an inactivation probability over all impact parameters from the ion to the sensitive sites within the cell nucleus. The inactivation probability is evaluated using the dose-response of the system to gamma-rays and the radial dose of the ions and may be equal to unity at small impact parameters for some ions. We show how the effects of inactivation may be taken into account in the evaluation of the mutation cross sections from heavy ions in the track structure model through correlation of sites for gene mutation and cell inactivation. The model is fit to available data for HPRT mutations in Chinese hamster cells and good agreement is found. The resulting calculations qualitatively show that mutation cross sections for heavy ions display minima at velocities where inactivation cross sections display maxima. Also, calculations show the high probability of mutation by relativistic heavy ions due to the radial extension of ions track from delta-rays in agreement with the microlesion concept. The effects of inactivation on mutations rates make it very unlikely that a single parameter such as LET or Z*2/beta(2) can be used to specify radiation quality for heavy ion bombardment.

Comprehensive sets of 124Xe(n ,γ )125Xe and 124Xe(n ,2 n )123Xe cross-section data for assessment of inertial-confinement deuterium-tritium fusion plasma

NASA Astrophysics Data System (ADS)

Bhike, Megha; Fallin, B.; Gooden, M. E.; Ludin, N.; Tornow, W.

2015-01-01

Measurements of the neutron radiative-capture cross section of 124Xe have been performed for the first time for neutron energies above 100 keV. In addition, data for the 124Xe(n ,2 n )123Xe reaction cross section have been obtained from threshold to 14.8 MeV to cover the entire energy range of interest, while previous data existed only at around 14 MeV. The results of these measurements provide the basis for an alternative and sensitive diagnostic tool for investigating properties of the inertial confinement fusion plasma in deuterium-tritium (DT) capsules at the National Ignition Facility located at Lawrence Livermore National Laboratory. Here, areal density ρ R (density × radius) of the fuel, burn asymmetry, and fuel-ablator mix are of special interest. The 124Xe(n ,γ )125Xe reaction probes the down-scattered neutrons, while the 124Xe(n ,2 n )123Xe reaction provides a measure of the 14 MeV direct neutrons.

Radiation Transport in Random Media With Large Fluctuations

NASA Astrophysics Data System (ADS)

Olson, Aaron; Prinja, Anil; Franke, Brian

2017-09-01

Neutral particle transport in media exhibiting large and complex material property spatial variation is modeled by representing cross sections as lognormal random functions of space and generated through a nonlinear memory-less transformation of a Gaussian process with covariance uniquely determined by the covariance of the cross section. A Karhunen-Loève decomposition of the Gaussian process is implemented to effciently generate realizations of the random cross sections and Woodcock Monte Carlo used to transport particles on each realization and generate benchmark solutions for the mean and variance of the particle flux as well as probability densities of the particle reflectance and transmittance. A computationally effcient stochastic collocation method is implemented to directly compute the statistical moments such as the mean and variance, while a polynomial chaos expansion in conjunction with stochastic collocation provides a convenient surrogate model that also produces probability densities of output quantities of interest. Extensive numerical testing demonstrates that use of stochastic reduced-order modeling provides an accurate and cost-effective alternative to random sampling for particle transport in random media.

Cross section of α-induced reactions on iridium isotopes obtained from thick target yield measurement for the astrophysical γ process

NASA Astrophysics Data System (ADS)

Szücs, T.; Kiss, G. G.; Gyürky, Gy.; Halász, Z.; Fülöp, Zs.; Rauscher, T.

2018-01-01

The stellar reaction rates of radiative α-capture reactions on heavy isotopes are of crucial importance for the γ process network calculations. These rates are usually derived from statistical model calculations, which need to be validated, but the experimental database is very scarce. This paper presents the results of α-induced reaction cross section measurements on iridium isotopes carried out at first close to the astrophysically relevant energy region. Thick target yields of 191Ir(α,γ)195Au, 191Ir(α,n)194Au, 193Ir(α,n)196mAu, 193Ir(α,n)196Au reactions have been measured with the activation technique between Eα = 13.4 MeV and 17 MeV. For the first time the thick target yield was determined with X-ray counting. This led to a previously unprecedented sensitivity. From the measured thick target yields, reaction cross sections are derived and compared with statistical model calculations. The recently suggested energy-dependent modification of the α + nucleus optical potential gives a good description of the experimental data.

Single track effects, Biostack and risk assessment

NASA Technical Reports Server (NTRS)

Curtis, S. B.; Chatterjee, A. (Principal Investigator)

1994-01-01

The scientific career of Prof. Bucker has spanned a very exciting period in the fledgling science of Space Radiation Biology. The capability for placing biological objects in space was developed, and the methods for properly packaging, retrieving and analyzing them were worked out. Meaningful results on the effects of radiation were obtained for the first time. In fact, many of the successful techniques and methodologies for handling biological samples were developed in Prof. Bucker's laboratories, as attested by the extensive Biostack program. He was the first to suggest and successfully carry out experiments in space directly aimed at measuring effects of single tracks of high-energy heavy galactic cosmic rays by specifically identifying whether or not the object had been hit by a heavy particle track. Because the "hit" frequencies of heavy galactic cosmic rays to cell nuclei in the bodies of space travelers will be low, it is expected that any effects to humans on the cellular level will be dominated by single-track cell traversals. This includes the most important generally recognized late effect of space radiation exposure: radiation-induced cancer. This paper addresses the single-track nature of the space radiation environment, and points out the importance of single "hits" in the evaluation of radiation risk for long-term missions occurring outside the earth's magnetic field. A short review is made of biological objects found to show increased effects when "hit" by a single heavy charged-particle in space. A brief discussion is given of the most provocative results from the bacterial spore Bacillus subtilis: experimental evidence that tracks can affect biological systems at much larger distances from the trajectory than previously suspected, and that the resultant inactivation cross section in space calculated for this system is very large. When taken at face value, the implication of these results, when compared to those from experiments performed at ground-based accelerators with beams at low energies in the same LET range, is that high-energy particles can exert their influence a surprising distance from their trajectory and the inactivation cross sections are some 20 times larger than expected. Clearly, beams from high-energy heavy-ion accelerators should be used to confirm these results. For those end points that can also be caused by low-LET beams such as high-energy protons, it is important to measure their action cross sections as well. The ratio of the cross sections for a high-LET beam to that of a low-LET beam is an interesting experimental ratio and, we suggest, of more intrinsic interest than the RBE (Relative Biological Effectiveness). It is a measure of the "biological" importance of one particle type relative to another particle type. This ratio will be introduced and given the name RPPE (Relative Per Particle Effectiveness). Values of RPPE have appeared in the literature and will be discussed. A rather well-known value of this quantity (13,520) has been suggested for the RPPE of high-energy iron ions to high-energy protons. This value was suggested by Letaw et al. Nature 330, 709-710 (1987)] we will call it the Letaw limit. It will be discussed in terms of the importance of the heavy-ion component vs light-ion component of the galactic cosmic rays. It is also pointed out, however, that there may be unique effects from single tracks of heavy ions that do not occur from light-ion tracks. For such effects, the concepts of both RBE and RPPE lose their meaning.

Vacuum ultraviolet photoionization cross section of the hydroxyl radical.

PubMed

Dodson, Leah G; Savee, John D; Gozem, Samer; Shen, Linhan; Krylov, Anna I; Taatjes, Craig A; Osborn, David L; Okumura, Mitchio

2018-05-14

The absolute photoionization spectrum of the hydroxyl (OH) radical from 12.513 to 14.213 eV was measured by multiplexed photoionization mass spectrometry with time-resolved radical kinetics. Tunable vacuum ultraviolet (VUV) synchrotron radiation was generated at the Advanced Light Source. OH radicals were generated from the reaction of O( 1 D) + H 2 O in a flow reactor in He at 8 Torr. The initial O( 1 D) concentration, where the atom was formed by pulsed laser photolysis of ozone, was determined from the measured depletion of a known concentration of ozone. Concentrations of OH and O( 3 P) were obtained by fitting observed time traces with a kinetics model constructed with literature rate coefficients. The absolute cross section of OH was determined to be σ(13.436 eV) = 3.2 ± 1.0 Mb and σ(14.193 eV) = 4.7 ± 1.6 Mb relative to the known cross section for O( 3 P) at 14.193 eV. The absolute photoionization spectrum was obtained by recording a spectrum at a resolution of 8 meV (50 meV steps) and scaling to the single-energy cross sections. We computed the absolute VUV photoionization spectrum of OH and O( 3 P) using equation-of-motion coupled-cluster Dyson orbitals and a Coulomb photoelectron wave function and found good agreement with the observed absolute photoionization spectra.

Vacuum ultraviolet photoionization cross section of the hydroxyl radical

NASA Astrophysics Data System (ADS)

Dodson, Leah G.; Savee, John D.; Gozem, Samer; Shen, Linhan; Krylov, Anna I.; Taatjes, Craig A.; Osborn, David L.; Okumura, Mitchio

2018-05-01

The absolute photoionization spectrum of the hydroxyl (OH) radical from 12.513 to 14.213 eV was measured by multiplexed photoionization mass spectrometry with time-resolved radical kinetics. Tunable vacuum ultraviolet (VUV) synchrotron radiation was generated at the Advanced Light Source. OH radicals were generated from the reaction of O(1D) + H2O in a flow reactor in He at 8 Torr. The initial O(1D) concentration, where the atom was formed by pulsed laser photolysis of ozone, was determined from the measured depletion of a known concentration of ozone. Concentrations of OH and O(3P) were obtained by fitting observed time traces with a kinetics model constructed with literature rate coefficients. The absolute cross section of OH was determined to be σ(13.436 eV) = 3.2 ± 1.0 Mb and σ(14.193 eV) = 4.7 ± 1.6 Mb relative to the known cross section for O(3P) at 14.193 eV. The absolute photoionization spectrum was obtained by recording a spectrum at a resolution of 8 meV (50 meV steps) and scaling to the single-energy cross sections. We computed the absolute VUV photoionization spectrum of OH and O(3P) using equation-of-motion coupled-cluster Dyson orbitals and a Coulomb photoelectron wave function and found good agreement with the observed absolute photoionization spectra.

Measurements of integrated and differential cross sections for isolated photon pair production in p p collisions at s = 8 TeV with the ATLAS detector

DOE PAGES

Aaboud, M.; Aad, G.; Abbott, B.; ...

2017-06-27

A measurement of the production cross section for two isolated photons in proton-proton collisions at a center-of-mass energy ofmore » $$\\sqrt{s}$$ = 8 TeV is presented. The results are based on an integrated luminosity of 20.2 fb -1 recorded by the ATLAS detector at the Large Hadron Collider. The measurement considers photons with pseudorapidities satisfying |η γ| < 1.37 or 1.56 < |η γ| < 2.37 and transverse energies of respectively E$$γ\\atop{T,1}$$ > 40 GeV and E$$γ\\atop{T,2}$$ > 30 GeV for the two leading photons ordered in transverse energy produced in the interaction. The background due to hadronic jets and electrons is subtracted using data-driven techniques. The fiducial cross sections are corrected for detector effects and measured differentially as a function of six kinematic observables. The measured cross section integrated within the fiducial volume is 16.8 ± 0.8 pb . Lastly, the data are compared to fixed-order QCD calculations at next-to-leading-order and next-to-next-to-leading-order accuracy as well as next-to-leading-order computations including resummation of initial-state gluon radiation at next-to-next-to-leading logarithm or matched to a parton shower, with relative uncertainties varying from 5% to 20%.« less

Radiation pressure: A possible cause for the superrotation of the Venusian atmosphere

NASA Technical Reports Server (NTRS)

Krause, J. L.

1992-01-01

The superrotation of the venusian atmosphere relative to the planet's surface has long been known. Yet the process by which this vigorous circulation is maintained is poorly understood. The purpose of this report is to show that a mechanism by which the solar radiation interacts with the cloudy atmosphere of Venus could be the principle cause of the superrotation. It has been long known that Venus has a high albedo due to the scattering (similar to the reflection process) of solar radiation by the cloud droplets in its atmosphere. The radiation not scattered, but intercepted by the planet and its atmosphere, is mainly absorbed within the cloud layers. Therefore, momentum (equal, more or less, to that of the solar radiation intercepted) is continually transferred to the venusian atmosphere. The atmospheric system presents a symmetrical surface (same radiation-matter interaction) toward the solar radiation at its morning and evening limbs. If the cross-sectional areas at both limbs were equal, the momentum transfer at the morning limb would decelerate the atmosphere's rotation while at the evening limb the same transfer would accelerate the rotation an equal amount. The net result of this is that the overall rate of rotation would be unchanged. Such a symmetrical configuration is not likely since the atmosphere must be warmed as it rotates across the planet's day hemisphere and cooled as it rotates across the planet's night hemisphere. This warming and cooling must result in a formation of an asymmetrical configuration. It is apparent that the momentum transfer at the evening limb must be greater than that at the morning limb because the atmosphere's greater cross section at the evening limb intercepts a greater amount of solar radiation. It should be noted that very little of the solar radiation is transmitted through the cloud layers, especially at or near the limbs where the atmospheric path length of the radiation is long. This net momentum transfer must be continually added to the angular momentum of the atmospheric system at the same time angular momentum is continually removed from the atmosphere by the frictional drag imposed on the atmosphere by the slowly rotating planet's surface. This completes the description of this mechanism.

Thermocapillary Convection in Liquid Droplets

NASA Technical Reports Server (NTRS)

1986-01-01

The purpose of this video is to understand the effects of surface tension on fluid convection. The fluid system chosen is the liquid sessile droplet to show the importance in single crystal growth, the spray drying and cooling of metal, and the advance droplet radiators of the space stations radiators. A cross sectional representation of a hemispherical liquid droplet under ideal conditions is used to show internal fluid motion. A direct simulation of buoyancy-dominant convection and surface tension-dominant convection is graphically displayed. The clear differences between two mechanisms of fluid transport, thermocapillary convection, and bouncy dominant convection is illustrated.

Sequential two-photon double ionization of noble gases by circularly polarized XUV radiation

NASA Astrophysics Data System (ADS)

Gryzlova, E. V.; Grum-Grzhimailo, A. N.; Kuzmina, E. I.; Strakhova, S. I.

2014-10-01

Photoelectron angular distributions (PADs) and angular correlations between two emitted electrons in sequential two-photon double ionization (2PDI) of atoms by circularly polarized radiation are studied theoretically. In particular, the sequential 2PDI of the valence n{{p}6} shell in noble gas atoms (neon, argon, krypton) is analyzed, accounting for the first-order corrections to the dipole approximation. Due to different selection rules in ionization transitions, the circular polarization of photons causes some new features of the cross sections, PADs and angular correlation functions in comparison with the case of linearly polarized photons.

Transport methods and interactions for space radiations

NASA Technical Reports Server (NTRS)

Wilson, John W.; Townsend, Lawrence W.; Schimmerling, Walter S.; Khandelwal, Govind S.; Khan, Ferdous S.; Nealy, John E.; Cucinotta, Francis A.; Simonsen, Lisa C.; Shinn, Judy L.; Norbury, John W.

1991-01-01

A review of the program in space radiation protection at the Langley Research Center is given. The relevant Boltzmann equations are given with a discussion of approximation procedures for space applications. The interaction coefficients are related to solution of the many-body Schroedinger equation with nuclear and electromagnetic forces. Various solution techniques are discussed to obtain relevant interaction cross sections with extensive comparison with experiments. Solution techniques for the Boltzmann equations are discussed in detail. Transport computer code validation is discussed through analytical benchmarking, comparison with other codes, comparison with laboratory experiments and measurements in space. Applications to lunar and Mars missions are discussed.

Neutron radiative capture cross section of Cu,6563 between 0.4 and 7.5 MeV

NASA Astrophysics Data System (ADS)

Newsome, I.; Bhike, M.; Krishichayan, Tornow, W.

2018-04-01

Natural copper is commonly used as cooling and shielding medium in detector arrangements designed to search for neutrinoless double-β decay. Neutron-induced background reactions on copper could potentially produce signals that are indistinguishable from the signals of interest. The present work focuses on radiative neutron capture experiments on Cu,6563 in the 0.4 to 7.5 MeV neutron energy range. The new data provide evaluations and model calculations with benchmark data needed to extend their applicability in predicting background rates in neutrinoless double-β decay experiments.

Development of Liquid Crystal Spatial Light Modulators for mid-IR Radiation, Addressed by Visible Radiation

DTIC Science & Technology

2002-10-01

POTENTIAL ENERGY DISTRIBUTION, % Further tables contain the frequencies of the most intense oscillations and the impact to the potential energy of atoms...0.96 µm diode pumping) 2F5/2 2F7/2 3H4 -23- In the Fig.3.1 is shown the working scheme of the active medium Yb- Pr:YLF(BYF). Energy , absorbed by... absorbed energy – 1 J, laser transition cross-section – σ = 2x10-21 cm2 [17]. Fig.3.4. Dependence of gain increment (kL) upon ytterbium concentration in

Spatially controlled, in situ synthesis of polymers

DOEpatents

Caneba, Gerard T.; Tirumala, Vijaya Raghavan; Mancini, Derrick C.; Wang, Hsien-Hau

2005-03-22

An in situ polymer microstructure formation method. The monomer mixture is polymerized in a solvent/precipitant through exposure to ionizing radiation in the absence any chemical mediators. If an exposure mask is employed to block out certain regions of the radiation cross section, then a patterned microstructure is formed. The polymerization mechanism is based on the so-called free-radical retrograde-precipitation polymerization process, in which polymerization occurs while the system is phase separating above the lower critical solution temperature. This method was extended to produce a crosslinked line grid-pattern of poly (N-isopropylacrylamide), which has been known to have thermoreversible properties.

Multimodality management of soft tissue tumors in the extremity

PubMed Central

Crago, Aimee M.; Lee, Ann Y.

2016-01-01

Most extremity soft tissue sarcomas present as a painless mass. Workup should generally involve cross-sectional imaging with MRI, as well as a core biopsy for pathologic diagnosis. Limb-sparing surgery is the standard of care, and may be supplemented with radiation for histologic subtypes at higher risk for local recurrence and chemotherapy for those at higher risk for distant metastases. This article reviews the work-up and surgical approach to extremity soft tissue sarcomas, as well as the role for radiation and chemotherapy, with particular attention given to the distinguishing characteristics of some of the most common subtypes. PMID:27542637

Heat transfer mechanism with thin filaments including ceramic high temperature heat exchanger

DOEpatents

Im, K.H.; Ahluwalia, R.K.

1994-10-18

A radiative heat transfer mechanism in a furnace is described having burners through which pulverized coal and air are burned producing combustion gases and contaminants. A plurality of elongated conduits are positioned inside the furnace proximate to the burners generally parallel to the flow of combustion gases in the furnace. A plurality of thin filaments are inside each of the elongated hollow conduits, the filaments having diameters in the range of from about 1 micrometer to about 1,000 micrometers and having an infrared radiation cross-section sufficient to cause the filaments to heat upon exposure to infrared radiation. Blower mechanism is associated with the elongated conduits for limiting the amount of soot and ash which deposit on the conduits to preserve the radiative and convective transfer of heat energy from the combustion gases to the conduits. 7 figs.

Heat transfer mechanism with thin filaments including ceramic high temperature heat exchanger

DOEpatents

Im, Kwan H.; Ahluwalia, Rajesh K.

1994-01-01

A radiative heat transfer mechanism in a furnace having burners through which pulverized coal and air are burned producing combustion gases and contaminants. A plurality of elongated conduits are positioned inside the furnace proximate to the burners generally parallel to the flow of combustion gases in the furnace. A plurality of thin filaments are inside each of the elongated hollow conduits, the filaments having diameters in the range of from about 1 micrometer to about 1,000 micrometers and having an infrared radiation cross-section sufficient to cause the filaments to heat upon exposure to infrared radiation. Blower mechanism is associated with the elongated conduits for limiting the amount of soot and ash which deposit on the conduits to preserve the radiative and convective transfer of heat energy from the combustion gases to the conduits.

Single photoionization of the Zn II ion in the photon energy range 17.5-90.0 eV: experiment and theory

NASA Astrophysics Data System (ADS)

Hinojosa, G.; Davis, V. T.; Covington, A. M.; Thompson, J. S.; Kilcoyne, A. L. D.; Antillón, A.; Hernández, E. M.; Calabrese, D.; Morales-Mori, A.; Juárez, A. M.; Windelius, O.; McLaughlin, B. M.

2017-10-01

Measurements of the single-photoionization cross-section of Cu-like Zn+ ions are reported in the energy (wavelength) range 17.5 eV (708 Å) to 90 eV (138 Å). The measurements on this trans-Fe element were performed at the Advanced Light Source synchrotron radiation facility in Berkeley, California at a photon energy resolution of 17 meV using the photon-ion merged-beams end-station. Below 30 eV, the spectrum is dominated by excitation autoionizing resonance states. The experimental results are compared with large-scale photoionization cross-section calculations performed using a Dirac Coulomb R-matrix approximation. Comparisons are made with previous experimental studies, resonance states are identified and contributions from metastable states of Zn+ are determined.

Photoionization of Ne8+

NASA Astrophysics Data System (ADS)

Pindzola, M. S.; Abdel-Naby, Sh. A.; Robicheaux, F.; Colgan, J.

2014-05-01

Single and double photoionization cross sections for Ne8+ are calculated using a non-perturbative fully relativistic time-dependent close-coupling method. A Bessel function expansion is used to include both dipole and quadrupole effects in the radiation field interaction and the repulsive interaction between electrons includes both the Coulomb and Gaunt interactions. The fully correlated ground state of Ne8+ is obtained by solving a time-independent inhomogeneous set of close-coupled equations. Propagation of the time-dependent close-coupled equations yields single and double photoionization cross sections for Ne8+ at energies easily accessible at advanced free electron laser facilities. This work was supported in part by grants from NSF and US DoE. Computational work was carried out at NERSC in Oakland, California, NICS in Knoxville, Tennessee, and OLCF in Oak Ridge, Tennessee.

Dissociative Excitation of Acetylene Induced by Electron Impact: Excitation-emission Cross-sections

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

Országh, Juraj; Danko, Marián; Čechvala, Peter

The optical emission spectrum of acetylene excited by monoenergetic electrons was studied in the range of 190–660 nm. The dissociative excitation and dissociative ionization associated with excitation of the ions initiated by electron impact were dominant processes contributing to the spectrum. The spectrum was dominated by the atomic lines (hydrogen Balmer series, carbon) and molecular bands (CH(A–X), CH(B–X), CH{sup +}(B–A), and C{sub 2}). Besides the discrete transitions, we have detected the continuum emission radiation of ethynyl radical C{sub 2}H(A–X). For most important lines and bands of the spectrum we have measured absolute excitation-emission cross sections and determined the energy thresholdsmore » of the particular dissociative channels.« less

N(+)-N and O(+)-O interaction energies, dipole transition moments, and transport cross sections

NASA Technical Reports Server (NTRS)

Partridge, H.; Stallcop, J. R.

1986-01-01

Complete sets of ion-atom interaction energies have been computed for nitrogen and oxygen with accurate large scale structure calculations. The computed energies agree well with the accurate potential curves available from spectroscopic measurement. The state functions from the nitrogen calculations have been applied to determine the transition moment for all allowed dipole transitions. These results can be combined to compute a detailed radiation spectrum such as that required to define the highly nonequilibrium environment of aeroassisted orbital transfer vehicle (AOTV). The long-range interaction energies have been used to determine the ion-atom resonance charge exchange cross sections that are important for transport processes such as diffusion. A calculation to determine reliable transport properties for energies that include the AOTV temperature range from these computed properties is described.

Physical processes in the strong magnetic fields of accreting neutron stars

NASA Technical Reports Server (NTRS)

Meszaros, P.

1984-01-01

Analytical formulae are fitted to observational data on physical processes occurring in strong magnetic fields surrounding accreting neutron stars. The propagation of normal modes in the presence of a quantizing magnetic field is discussed in terms of a wave equation in Fourier space, quantum electrodynamic effects, polarization and mode ellipticity. The results are applied to calculating the Thomson scattering, bremsstrahlung and Compton scattering cross-sections, which are a function of the frequency, angle and polarization of the magnetic field. Numerical procedures are explored for solving the radiative transfer equations. When applied to modeling X ray pulsars, a problem arises in the necessity to couple the magnetic angle and frequency dependence of the cross-sections with the hydrodynamic equations. The use of time-dependent averaging and approximation techniques is indicated.

Calculation of the total electron excitation cross section in the Born approximation using Slater wave functions for the Li (2s yields 2p), Li (2s yields 3p), Na (3s yields 4p), Mg (3p yields 4s), Ca (4s yields 4p) and K (4s yields 4p) excitations. M.S. Thesis

NASA Technical Reports Server (NTRS)

Simsic, P. L.

1974-01-01

Excitation of neutral atoms by inelastic scattering of incident electrons in gaseous nebulae were investigated using Slater Wave functions to describe the initial and final states of the atom. Total cross sections using the Born Approximation are calculated for: Li(2s yields 2p), Na(3s yields 4p), k(4s yields 4p). The intensity of emitted radiation from gaseous nebulae is also calculated, and Maxwell distribution is employed to average the kinetic energy of electrons.

Prognostic significance of lesion size for glioblastoma multiforme.

PubMed

Reeves, G I; Marks, J E

1979-08-01

From March 1974 to December 1976, 56 patients with glioblastoma multiforme had precraniotomy computed tomography (CT) scans from which the lesion size was determined by measuring the cross-sectional area. Thirty-two patients underwent surgery followed by irradiation, and 24 had surgery followed by irradiation and chemotherapy. There was no difference in survival between the 16 patients with small lesions and the 16 patients with large lesions in the surgery plus radiation alone group, nor in the 16 patients with small and 8 patients with large lesions in the surgery, radiation and chemotherapy group. Minimum follow-up was one year. Other possible prognostic factors including age, tumor grade, radiation dose, and performance status were comparable for each subgroup. Lesion size in glioblastoma multiforme appears unrelated to prognosis.

Particle Methods for Simulating Atomic Radiation in Hypersonic Reentry Flows

NASA Astrophysics Data System (ADS)

Ozawa, T.; Wang, A.; Levin, D. A.; Modest, M.

2008-12-01

With a fast reentry speed, the Stardust vehicle generates a strong shock region ahead of its blunt body with a temperature above 60,000 K. These extreme Mach number flows are sufficiently energetic to initiate gas ionization processes and thermal and chemical ablation processes. The nonequilibrium gaseous radiation from the shock layer is so strong that it affects the flowfield macroparameter distributions. In this work, we present the first loosely coupled direct simulation Monte Carlo (DSMC) simulations with the particle-based photon Monte Carlo (p-PMC) method to simulate high-Mach number reentry flows in the near-continuum flow regime. To efficiently capture the highly nonequilibrium effects, emission and absorption cross section databases using the Nonequilibrium Air Radiation (NEQAIR) were generated, and atomic nitrogen and oxygen radiative transport was calculated by the p-PMC method. The radiation energy change calculated by the p-PMC method has been coupled in the DSMC calculations, and the atomic radiation was found to modify the flow field and heat flux at the wall.

Structural-electrical coupling optimisation for radiating and scattering performances of active phased array antenna

NASA Astrophysics Data System (ADS)

Wang, Congsi; Wang, Yan; Wang, Zhihai; Wang, Meng; Yuan, Shuai; Wang, Weifeng

2018-04-01

It is well known that calculating and reducing of radar cross section (RCS) of the active phased array antenna (APAA) are both difficult and complicated. It remains unresolved to balance the performance of the radiating and scattering when the RCS is reduced. Therefore, this paper develops a structure and scattering array factor coupling model of APAA based on the phase errors of radiated elements generated by structural distortion and installation error of the array. To obtain the optimal radiating and scattering performance, an integrated optimisation model is built to optimise the installation height of all the radiated elements in normal direction of the array, in which the particle swarm optimisation method is adopted and the gain loss and scattering array factor are selected as the fitness function. The simulation indicates that the proposed coupling model and integrated optimisation method can effectively decrease the RCS and that the necessary radiating performance can be simultaneously guaranteed, which demonstrate an important application value in engineering design and structural evaluation of APAA.

Investigation of Noise and Vibration in Tires Through Analytical Modeling, Tests and Simulations

NASA Astrophysics Data System (ADS)

Cao, Rui

Tire noise and vibration is an interesting topic, with more and more people paying attention to this issue. Tire noise can both propagate into the vehicle interior and radiate directly toward the immediate environment. Tire noise is not only related to vehicle passengers' comfort but also affects the residential or working area near highways, especially in high population density regions. The emerging electric vehicles also emphasize tires' role in vehicle Noise Vibration and Harshness (NVH) since power-train noises are significantly reduced. The study in this research focuses on the noise and vibration of tires from the low to high frequency range, typically from 60 kHz to 2 kHz. From the analytical point of view, forced vibration of a fully coupled 2D structural-acoustical model is presented and a 3D structural model is also investigated for various input conditions. Both circumferential and cross-sectional shearing motions in the analytical tire models can be observed. Static tire surface mobilities were also measured to verify the findings from the developed models. On the experimental side, the loading effect on tire noise radiation was studied, where applied loads ranged from 500 lbs to 1300 lbs. Results indicate that sound radiation is usually proportional to the loading, except between 1.1 kHz to 1.7 kHz where the load-noise relation is reversed. In addition, tire noise generated by road surface discontinuities was also studied experimentally. As expected, a broadband increase of the noise spectrum can be observed below 1 kHz compared to the noise on a continuous surface. However, the difference tends to diminish above 1 kHz except in a certain narrow frequency band depending on the particular tire tested. High frequency waves and motions in tire cross-sectional directions were identified as occurring in the frequency range of interest. A two-dimensional cross-sectional analytical tire model was proposed for further investigations, in order to verify the relation among high frequency tire noise properties and the fast propagating waves and cross-sectional motions in tires. Finally, a fully coupled finite element tire-wheel model was developed to simulate the tire deformation under static vertical loading and to explore the influence of various excitation forces. The forces or accelerations, depending on the boundary conditions, at the wheel center can be calculated from the tire model up to 500 Hz. The results can be potentially used as input for vehicle full body simulations, thus accelerating the optimization process of new product development.

REACTION $pi$$sup -$ + p $Yields$ $pi$$sup -$ + $pi$$sup +$ + n FROM 360 TO 800 Mev

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

Kirz, J.; Schwartz, J.; Tripp, R.D.

1963-10-31

The reaction ceramic materia /sup -/ + p ons in pyrolyti ceramic materia /sup -/ + ceramic materia /sup +/ + n is sLLawrence Radiation Laboratory's 72-in. hydrogen bubble chamber. Events are located by scanning the pictures for ceramic materia /sup +/ tracks. Cross sections, Dalitz plots, and ceramic materia /sup +/ ceramic materia /sup -/ d please delete abstract 26339

NUCFRG2: An evaluation of the semiempirical nuclear fragmentation database

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Tripathi, R. K.; Cucinotta, F. A.; Shinn, J. L.; Badavi, F. F.; Chun, S. Y.; Norbury, J. W.; Zeitlin, C. J.; Heilbronn, L.; Miller, J.

1995-01-01

A semiempirical abrasion-ablation model has been successful in generating a large nuclear database for the study of high charge and energy (HZE) ion beams, radiation physics, and galactic cosmic ray shielding. The cross sections that are generated are compared with measured HZE fragmentation data from various experimental groups. A research program for improvement of the database generator is also discussed.

Gamma-Ray background spectrum and annihilation rate in the baryon-symmetric big-bang cosmology

NASA Technical Reports Server (NTRS)

Puget, J. L.

1973-01-01

An attempt was made to extract experimental data on baryon symmetry by observing annihilation products. Specifically, gamma rays and neutrons with long mean free paths were analyzed. Data cover absorption cross sections and radiation background of the 0.511 MeV gamma rays from positron annihilations and the 70 MeV gamma rays from neutral pion decay.

Advanced Physical Models and Numerical Methods for High Enthalpy and Plasma Flows Applied to Hypersonics

DTIC Science & Technology

2011-07-28

4874–48??, 1970. [16] R. O. Jung , J. B. Boffard, L. W. Anderson, and C. C. Lin. Electron-impact excitation cross sections from the xenon j = 2...Journal of Quantitative Spectroscopy and Radiative Transfer, 5(2):503– 510, 1965. [35] O. Zatsarinny and K. Bartschat. B -spline Breit- Pauli R-matrix

Radiation doses and neutron irridation effects on human cells based on calculations

NASA Astrophysics Data System (ADS)

Radojevic, B. B.; Cukavac, M.; Jovanovic, D.

In general, main aim of our paper is to follow influence of neutron's radiation on materials, but one of possible applications of fast neutrons in therapeutical reasons i.e. their influence on carcinom cells of difficuilt geometries in human bodies too. Interactions between neutrons and human cells of tissue are analysed here. We know that the light nuclei of hydrogen, nitrogen, carbon, and oxygen are main constituents of human cells, and that different nuclear models are usually used to present interactions of nuclear particles with mentioned elements. Some of most widely used pre-equilibrium nuclear models are: intranuclear cascade model (ICN), Harp-Miller-Berne (HMB), geometry-dependent hybrid (GDH) and exciton models (EM). In this paper is studied and calculated the primary energetic spectra of the secundary particles (neutrons, protons, and gamas) emitted from this interactions, and followed by corresponding integral cross sections, based on exciton model (EM). The total emission cross-section is the sum of emissions in all stages of energies. Obtained spectra for interactions type of (n, n'), (n, p), and (n, ?), for various incident neutron energies in the interval from 3 MeV up to 30 MeV are analysed too. Some results of calculations are presented here.

Relativistic Many-Body Approach to Calculating Radiation and Autoionization Probabilities, Electron Collision Strengths For Multicharged Ions in a Plasma: Debae Approximation

NASA Astrophysics Data System (ADS)

Glushkov, Alexander; Loboda, Andrey; Nikola, Ludmila

2011-10-01

We present the uniform energy approach, formally based on the gauge-invariant relativistic many-body perturbation theory for the calculation of the radiative and autoionization probabilities, electron collision strengths and rate coefficients in a multicharged ions (in a collisionally pumped plasma). An account for the plasma medium influence is carried out within a Debae shielding approach. The aim is to study, in a uniform manner, elementary processes responsible for emission-line formation in a plasma. The energy shift due to the collision is arisen at first in the second PT order in the form of integral on the scattered electron energy. The cross-section is linked with imaginary part of the scattering energy shift. The electron collision excitation cross-sections and rate coefficients for some plasma Ne-, Ar-like multicharged ions are calculated within relativistic energy approach. We present the results of calculation the autoionization resonances energies and widths in heavy He-like multicharged ions and rare-earth atoms of Gd and Tm. To test the results of calculations we compare the obtained data for some Ne-like ions with other authors' calculations and available experimental data for a wide range of plasma conditions.

Structural and luminescence studies of Ho{sup 3+}-doped zinc-aluminium-sodium-phosphate (ZANP) glasses

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

Brahmachary, K.; Rajesh, D.; Ratnakaram, Y. C., E-mail: ratnakaramsvu@gmail.com

Trivalent holmium doped zinc-aluminium-sodium-phosphate (ZANP) glasses were prepared by conventional melt-quenching technique and characterized for their structural and luminescence properties. The amorphous nature, elemental analysis and thermal stability of the glasses were studied by using X-ray diffraction, energy dispersive spectrum and differential scanning calorimetry analysis, respectively. The absorption and fluorescence spectra have been recorded at room temperature. Based on the absorption spectra, the Judd-Ofelt parameters and radiative parameters such as spontaneous transition probabilities (A{sub R}), branching ratios (β{sub R}), radiative lifetimes (τ{sub R}) were calculated and discussed. From the emission spectra emission peak positions (λ{sub P}), effective bandwidths (Δλ{sub eff})more » and stimulated emission cross-sections (σ{sub P}) were calculated for the observed emission transitions,{sup 5}S{sub 2} ({sup 5}F{sub 4}→{sup 5}I{sub 8}) and {sup 5}F{sub 5}→{sup 5}I{sub 8} in all the glass samples. The stimulated emission cross-section is higher for ZANPHo10 glass matrix and so it may be useful for laser excitation.« less

Monte Carlo track structure for radiation biology and space applications

NASA Technical Reports Server (NTRS)

Nikjoo, H.; Uehara, S.; Khvostunov, I. G.; Cucinotta, F. A.; Wilson, W. E.; Goodhead, D. T.

2001-01-01

Over the past two decades event by event Monte Carlo track structure codes have increasingly been used for biophysical modelling and radiotherapy. Advent of these codes has helped to shed light on many aspects of microdosimetry and mechanism of damage by ionising radiation in the cell. These codes have continuously been modified to include new improved cross sections and computational techniques. This paper provides a summary of input data for ionizations, excitations and elastic scattering cross sections for event by event Monte Carlo track structure simulations for electrons and ions in the form of parametric equations, which makes it easy to reproduce the data. Stopping power and radial distribution of dose are presented for ions and compared with experimental data. A model is described for simulation of full slowing down of proton tracks in water in the range 1 keV to 1 MeV. Modelling and calculations are presented for the response of a TEPC proportional counter irradiated with 5 MeV alpha-particles. Distributions are presented for the wall and wall-less counters. Data shows contribution of indirect effects to the lineal energy distribution for the wall counters responses even at such a low ion energy.

A laboratory study of the lambda 2145 A auroral mystery feature

NASA Technical Reports Server (NTRS)

Erdman, P. W.; Espy, P. J.; Zipf, E. C.

1980-01-01

The prominent emission feature near 2145 A in the ultraviolet spectrum of an aurora has been tentatively identified by Dick (1978) as the doublet lines, 2139.68 A and 2143.55 A, emitted by metastable N+(5S) ions, and dissociative excitation of N2 by electron impact with a cross section greater than or equal to 2 x 10 to the -18th sq cm has been proposed as the source of this species. A detailed laboratory study of dissociative excitation is described that suggests two alternative viewpoints of this process: (1) If the calculated radiative lifetime for the N+(5S) state (4.4 microsec) is correct, then the N+(5S) dissociative excitation cross section is less than 3 x 10 to the -21st sq cm. Thus, a new N+(5S) source mechanism would have to be found in order to account for the auroral data. (2) If dissociative excitation does form N+(5S) ions efficiently, then the laboratory and field observations imply a radiative lifetime for this state of more than 10 msec, thus suggesting that there are major errors in the lifetime computation.

Benchmarked analyses of gamma skyshine using MORSE-CGA-PC and the DABL69 cross-section set

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

Reichert, P.T.; Golshani, M.

1991-01-01

Design for gamma-ray skyshine is a common consideration for a variety of nuclear and accelerator facilities. Many of these designs can benefit from a more accurate and complete treatment than can be provided by simple skyshine analysis tools. Those methods typically require a number of conservative, simplifying assumptions in modeling the radiation source and shielding geometry. This paper considers the benchmarking of one analytical option. The MORSE-CGA Monte Carlo radiation transport code system provides the capability for detailed treatment of virtually any source and shielding geometry. Unfortunately, the mainframe computer costs of MORSE-CGA analyses can prevent cost-effective application to smallmore » projects. For this reason, the MORSE-CGA system was converted to run on IBM personal computer (PC)-compatible computers using the Intel 80386 or 80486 microprocessors. The DLC-130/DABL69 cross-section set (46n,23g) was chosen as the most suitable, readily available, broad-group library. The most important reason is the relatively high (P{sub 5}) Legendre order of expansion for angular distribution. This is likely to be beneficial in the deep-penetration conditions modeled in some skyshine problems.« less

Parallel and series FED microstrip array with high efficiency and low cross polarization

NASA Technical Reports Server (NTRS)

Huang, John (Inventor)

1995-01-01

A microstrip array antenna for vertically polarized fan beam (approximately 2 deg x 50 deg) for C-band SAR applications with a physical area of 1.7 m by 0.17 m comprises two rows of patch elements and employs a parallel feed to left- and right-half sections of the rows. Each section is divided into two segments that are fed in parallel with the elements in each segment fed in series through matched transmission lines for high efficiency. The inboard section has half the number of patch elements of the outboard section, and the outboard sections, which have tapered distribution with identical transmission line sections, terminated with half wavelength long open-circuit stubs so that the remaining energy is reflected and radiated in phase. The elements of the two inboard segments of the two left- and right-half sections are provided with tapered transmission lines from element to element for uniform power distribution over the central third of the entire array antenna. The two rows of array elements are excited at opposite patch feed locations with opposite (180 deg difference) phases for reduced cross-polarization.

Radiation and scattering from bodies of translation. Volume 2: User's manual, computer program documentation

NASA Astrophysics Data System (ADS)

Medgyesi-Mitschang, L. N.; Putnam, J. M.

1980-04-01

A hierarchy of computer programs implementing the method of moments for bodies of translation (MM/BOT) is described. The algorithm treats the far-field radiation and scattering from finite-length open cylinders of arbitrary cross section as well as the near fields and aperture-coupled fields for rectangular apertures on such bodies. The theoretical development underlying the algorithm is described in Volume 1. The structure of the computer algorithm is such that no a priori knowledge of the method of moments technique or detailed FORTRAN experience are presupposed for the user. A set of carefully drawn example problems illustrates all the options of the algorithm. For more detailed understanding of the workings of the codes, special cross referencing to the equations in Volume 1 is provided. For additional clarity, comment statements are liberally interspersed in the code listings, summarized in the present volume.

Compton Scattering Cross Sections in Strong Magnetic Fields: Advances for Neutron Star Applications

NASA Astrophysics Data System (ADS)

Ickes, Jesse; Gonthier, Peter L.; Eiles, Matthew; Baring, Matthew G.; Wadiasingh, Zorawar

2014-08-01

Various telescopes including RXTE, INTEGRAL, Suzaku and Fermi have detected steady non-thermal X-ray emission in the 10 ~ 200 keV band from strongly magnetic neutron stars known as magnetars. Magnetic inverse Compton scattering is believed to be a leading candidate for the production of this intense X-ray radiation. Generated by electrons possessing ultra-relativistic energies, this leads to attractive simplifications of the magnetic Compton cross section. We have recently addressed such a case by developing compact analytic expressions using correct spin-dependent widths acquired through the implementation of Sokolov & Ternov (ST) basis states, focusing specifically on ground state-to-ground state scattering. Such scattering in magnetar magnetospheres can cool electrons down to mildly-relativistic energies. Moreover, soft gamma-ray flaring in magnetars may well involve strong Comptonization in expanding clouds of mildly-relativistic pairs. These situations necessitate the development of more general magnetic scattering cross sections, where the incoming photons acquire substantial incident angles relative to the field in the rest frame of the electron, and the intermediate state can be excited to arbitrary Landau levels. Here, we highlight results from such a generalization using ST formalism. The cross sections treat the plethora of harmonic resonances associated with various cyclotron transitions between Landau states. Polarization dependence of the cross section for the four scattering modes is illustrated and compared with the non-relativistic Thompson cross section with classical widths. Results will find application to various neutron star problems, including computation of Eddington luminosities and polarization mode-switching rates in transient magnetar fireballs.We express our gratitude for the generous support of Michigan Space Grant Consortium, the National Science Foundation (grants AST-0607651, AST-1009725, AST-1009731 and PHY/DMR-1004811), and the NASA Astrophysics Theory Program through grants NNX06AI32G, NNX09AQ71G and NNX10AC59A.

Commentary: exciting new developments in fast neutron cross sections and dosimetry

NASA Astrophysics Data System (ADS)

Bielajew, A. F.; Chadwick, M. B.

1998-12-01

The field of fast neutron therapy, and to some extent the practice of radiation protection in the vicinity of medical linear accelerators, requires accurate physical data. The paucity of physical data for neutron cross sections above about 15 MeV in low- Z materials is best exemplified (and somewhat exaggerated!) in the late Herb Attix's standard textbook Introduction to Radiological Physics and Radiation Dosimetry (Attix 1986). On page 464, the contributions to kerma in tissue from neutrons stops abruptly shortly above about 15 MeV. Photon and electron dosimetry has benefited from a well established and highly cohesive relationship between measurement and theory due to the enormous success of quantum electrodynamics. In contrast, measurements in the field of neutron radiotherapy have benefited less from theory because of the complexity of the quantum mechanics of nuclear structure, especially for light elements. This is because the nuclear levels are widely spaced at low excitation energies unlike for heavy elements where the energy level spacing is more dense and statistical assumptions can be applied with success. This means that accurate measurements are crucial for guiding and testing theoretical development. Measurements contributing to the field of fast neutron dosimetry are few and far between. Amazingly, in this issue of Physics in Medicine and Biology there are two such contributions! The paper by Benck, Slypen, Meulders and Corcalciuc (1998) entitled `Experimental double differential cross sections and derived kerma factors for oxygen at incident neutron energies from reaction thresholds to 65 MeV' reports on a set of measurements of the doubly-differential cross sections (energy and angle) for fast neutrons on for 9 energies between 25 and 65 MeV. The reaction channels measured were (n, px), (n, dx), (n, tx) and (n, x). These cross sections were then integrated to produce partial and total kerma factors. There are several features of this paper that are particularly exciting: The quality of the measurements on oxygen appears to have taken a significant leap forward in comparison with the only other experimental studies (Subramanian et al 1983, 1986). In particular, a comprehensive angular range is covered, allowing a more accurate angle-integration of the data, and good statistics are obtained. Much of the cross section experimental data appears to either support or contradict the relatively recent theoretical calculations of Brenner and Prael (1989) and Chadwick and Young (1996). In a few cases the discrepancies between measurement and theory are so large as to motivate more theoretical development in this area. The agreement between the measured kerma factors and theoretical values is excellent. The second paper by Binns, DeLuca Jr, Maughan and Kota (1998) entitled `Direct determination of kerma for a d(48.5)+Be therapy beam' describes a direct measurement of the kerma ratio, , of muscle tissue to A-150 plastic for the fast neutron therapy facility of Harper Hospital in Detroit, Michigan. The measured value of was found to be - a significant departure from that determined using the currently accepted dosimetry protocol (ICRU 1989) (a value of 0.95). This measurement can also be used to test the accuracy of theoretical predictions, since the kerma ratio can be calculated by averaging the theoretical kerma factor ratios over the neutron spectrum at Harper Hospital, which can be estimated from radiation transport simulations of the Be+ d neutron source. Deviations between theory and experiment will stimulate future studies to better understand the cross sections, kerma factors, and neutron spectra. These new measurements described in this issue of Physics in Medicine and Biology raise the standard in fast neutron dosimetry and also make fundamental contributions to the understanding of nuclear structure and reaction mechanisms. It is indeed remarkable and satisfying that the demands of a very practical field like medical physics can issue scientific challenges in even the most basic disciplines, and that the basic sciences rise to the challenge with enthusiasm. References Attix F H 1986 Introduction to Radiological Physics and Radiation Dosimetry (New York: Wiley) Benck S, Slypen I, Meulders J P and Corcalciuc V 1998 Experimental double differential cross sections and derived kerma factors for oxygen at incident neutron energies from reaction thresholds to 65 MeV Phys. Med. Biol. 43 3427-47 Binns P J, DeLuca Jr P M, Maughan R L and Kota C 1998 Direct determination of kerma for a d(48.5)+Be therapy beam Phys. Med. Biol. 43 3449-57 Brenner D J and Prael R R 1989 Calculated differential secondary-particle production cross-sections after nonelastic neutron interactions with carbon and oxygen between 15 and 60 MeV Atomic and Nuclear Data Tables 41 71-99 Chadwick M B and Young P G 1996 Calculation and evaluation of cross sections and kerma factors for neutrons up to 100 MeV on and Nucl. Sci. Eng. 123 1-16 ICRU 1989 Clinical neutron dosimetry part I: determination of absorbed dose in a patient treated by external beams of fast neutrons ICRU Report 45 (Washington, DC: ICRU) Subramanian T S et al 1983 Double differential inclusive hydrogen and helium spectra from neutron-induced reactions on carbon at 27.4, 39.7 and 60.7 MeV Phys. Rev. C 28 521-8 Subramanian T S et al 1986 Double differential inclusive hydrogen and helium spectra from neutron-induced reactions on carbon at 27.4, 39.7 and 60.7 MeV: oxygen and nitrogen Phys. Rev. C 34 1580-7

Differential cross sections for electron-impact excitation of the electronic states of pyrimidine

NASA Astrophysics Data System (ADS)

Brunger, Michael; Jones, Darryl; Bellm, Susan

2012-06-01

Pyrimidine (C4N2H4) is an important molecule, as it forms the basis of larger biomolecules, such as the DNA bases thymine, cytosine and uracil. There is a pressing demand for low-energy electron scattering data from such biological analogs in order to model radiation induced damage [1]. We therefore present the first measurements for absolute differential cross section data for low-energy electron-impact excitation of the electronic states of pyrimidine. The present measurements were performed using a crossed-beam apparatus [2] for incident electron energies ranging between 15 to 50eV while covering a 10 to 90^o angular range. Here the absolute scale has been determined through a normalisation to the recently measured elastic scattering differential cross section data for pyrimidine [3]. [1] F. Ferreira da Silva, D. Almeida, G. Martins, A. R. Milosavljevic, B. P. Marinkovic, S. V. Hoffmann, N. J. Mason, Y. Nunes, G. Garcia and P. Limao-Vieira, Phys Chem Chem Phys 12, 6717 (2010). [2] M. J. Brunger and P. J. O. Teubner, Phys Rev A 41, 1413 (1990). [3] P. Palihawadana, J. Sullivan, M. Brunger, C. Winstead, V. McKoy, G. Garcia, F. Blanco and S. Buckman, Phys Rev A 84, 062702 (2011).

Temperature dependent absorption cross-sections of O2-O2 collision pairs between 340 and 630 nm and at atmospherically relevant pressure.

PubMed

Thalman, Ryan; Volkamer, Rainer

2013-10-07

The collisions between two oxygen molecules give rise to O4 absorption in the Earth atmosphere. O4 absorption is relevant to atmospheric transmission and Earth's radiation budget. O4 is further used as a reference gas in Differential Optical Absorption Spectroscopy (DOAS) applications to infer properties of clouds and aerosols. The O4 absorption cross section spectrum of bands centered at 343, 360, 380, 446, 477, 532, 577 and 630 nm is investigated in dry air and oxygen as a function of temperature (203-295 K), and at 820 mbar pressure. We characterize the temperature dependent O4 line shape and provide high precision O4 absorption cross section reference spectra that are suitable for atmospheric O4 measurements. The peak absorption cross-section is found to increase at lower temperatures due to a corresponding narrowing of the spectral band width, while the integrated cross-section remains constant (within <3%, the uncertainty of our measurements). The enthalpy of formation is determined to be ΔH(250) = -0.12 ± 0.12 kJ mol(-1), which is essentially zero, and supports previous assignments of O4 as collision induced absorption (CIA). At 203 K, van der Waals complexes (O(2-dimer)) contribute less than 0.14% to the O4 absorption in air. We conclude that O(2-dimer) is not observable in the Earth atmosphere, and as a consequence the atmospheric O4 distribution is for all practical means and purposes independent of temperature, and can be predicted with an accuracy of better than 10(-3) from knowledge of the oxygen concentration profile.

Compton Scattering Cross Sections in Strong Magnetic Fields: Advances for Neutron Star Applications

NASA Astrophysics Data System (ADS)

Eiles, Matthew; Gonthier, P. L.; Baring, M. G.; Wadiasingh, Z.

2013-04-01

Various telescopes including RXTE, INTEGRAL and Suzaku have detected non-thermal X-ray emission in the 10 - 200 keV band from strongly magnetic neutron stars. Inverse Compton scattering, a quantum-electrodynamical process, is believed to be a leading candidate for the production of this intense X-ray radiation. Magnetospheric conditions are such that electrons may well possess ultra-relativistic energies, which lead to attractive simplifications of the cross section. We have recently addressed such a case by developing compact analytic expressions using correct spin-dependent widths and Sokolov & Ternov (ST) basis states, focusing specifically on ground state-to-ground state scattering. However, inverse Compton scattering can cool electrons down to mildly-relativistic energies, necessitating the development of a more general case where the incoming photons acquire nonzero incident angles relative to the field in the rest frame of the electron, and the intermediate state can be excited to arbitrary Landau levels. In this paper, we develop results pertaining to this general case using ST formalism, and treating the plethora of harmonic resonances associated with various cyclotron transitions between Landau states. Four possible scattering modes (parallel-parallel, perpendicular-perpendicular, parallel-perpendicular, and perpendicular-parallel) encapsulate the polarization dependence of the cross section. We present preliminary analytic and numerical investigations of the magnitude of the extra Landau state contributions to obtain the full cross section, and compare these new analytic developments with the spin-averaged cross sections, which we develop in parallel. Results will find application to various neutron star problems, including computation of Eddington luminosities in the magnetospheres of magnetars. We express our gratitude for the generous support of the Michigan Space Grant Consortium, of the National Science Foundation (REU and RUI), and the NASA Astrophysics Theory and Fundamental Program.

Re-examination of a Classic Experiment to Measure the Positronium-Helium Cross Section

NASA Technical Reports Server (NTRS)

Drachman, Richard J.; DiRienzi, Joseph

1998-01-01

In 1975, before the advent of positronium beams, a clever experiment was carried out in an attempt to measure low-energy Ps-atom scattering cross-sections, especially that of Ps-He. A series of parallel thin plates was placed in the vessel containing the sample of gas, and positrons were allowed to enter the chamber from a radioactive source. The time spectrum of annihilation radiation was observed in the traditional way, and the pickoff annihilation due to thermalized Ps striking one of the plates was to be the special feature of the experiment. Using a diffusion analysis the authors derived cross- sections for several gases, and for helium the value obtained was sigma = 0.0166 pi(alpha)(sub o, sup 2). Even then this value was thought to be very much too small, while recent measurements and some calculations suggest a more reasonable value would be sigma = 3 to 13 pi(alpha)(sub o,sup 2). It has always been puzzling that an apparently well-designed experiment should give such an unsatisfactory result. We have now re-examined the analysis of the data with some interesting consequences which may explain the discrepancy. Two main observations support our re-analysis. First, we note that the mean free path for Ps-He scattering would be quite long if the cross-section were as small as that quoted above; the diffusion method itself would seem to be questionable. For the larger values, however, there would be no such problem. Second, it was assumed that when the annihilation rate had settled down and was following an exponential decay curve the asymptotic solution of the diffusion equation had been reached. We find, instead, that a superposition of exponentials can accurately represent the decay curve, consistent with the higher cross-section value.

Evaluated cross-section libraries and kerma factors for neutrons up to 100 MeV on {sup 12}C

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

Chadwick, M.B.; Blann, M.; Cox, L.

1995-04-11

A program is being carried out at Lawrence Livermore National Laboratory to develop high-energy evaluated nuclear data libraries for use in Monte Carlo simulations of cancer radiation therapy. In this report we describe evaluated cross sections and kerma factors for neutrons with incident energies up to 100 MeV on {sup 12}C. The aim of this effort is to incorporate advanced nuclear physics modeling methods, with new experimental measurements, to generate cross section libraries needed for an accurate simulation of dose deposition in fast neutron therapy. The evaluated libraries are based mainly on nuclear model calculations, benchmarked to experimental measurements wheremore » they exist. We use the GNASH code system, which includes Hauser-Feshbach, preequilibrium, and direct reaction mechanisms. The libraries tabulate elastic and nonelastic cross sections, angle-energy correlated production spectra for light ejectiles with A{le}and kinetic energies given to light ejectiles and heavy recoil fragments. The major steps involved in this effort are: (1) development and validation of nuclear models for incident energies up to 100 MeV; (2) collation of experimental measurements, including new results from Louvain-la-Nueve and Los Alamos; (3) extension of the Livermore ENDL formats for representing high-energy data; (4) calculation and evaluation of nuclear data; and (5) validation of the libraries. We describe the evaluations in detail, with particular emphasis on our new high-energy modeling developments. Our evaluations agree well with experimental measurements of integrated and differential cross sections. We compare our results with the recent ENDF/B-VI evaluation which extends up to 32 MeV.« less

Measurement of the neutron-capture cross section of 76Ge and 74Ge below 15 MeV and its relevance to 0 νββ decay searches of 76Ge

NASA Astrophysics Data System (ADS)

Bhike, Megha; Fallin, B.; Krishichayan; Tornow, W.

2015-02-01

The neutron radiative-capture cross section of 76Ge was measured between 0.4 and 14.8 MeV using the activation technique. Germanium samples with the isotopic abundance of ∼ 86%76Ge and ∼ 14%74Ge used in the 0 νββ searches by the GERDA and Majorana Collaborations were irradiated with monoenergetic neutrons produced at eleven energies via the 3H (p , n)3He, 2H (d , n)3He and 3H (d , n)4He reactions. Previously, data existed only at thermal energies and at 14 MeV. As a by-product, capture cross-section data were also obtained for 74Ge at neutron energies below 8 MeV. Indium and gold foils were irradiated simultaneously for neutron fluence determination. High-resolution γ-ray spectroscopy was used to determine the γ-ray activity of the daughter nuclei of interest. For the 76Ge total capture cross section the present data are in good agreement with the TENDL-2013 model calculations and the ENDF/B-VII.1 evaluations, while for the 74Ge (n , γ)75Ge reaction, the present data are about a factor of two larger than predicted. It was found that the 74Ge (n , γ)75Ge yield in the High-Purity Germanium (HPGe) detectors used by the GERDA and Majorana Collaborations is only about a factor of two smaller than the 76Ge (n , γ)77Ge yield due to the larger cross section of the former reaction.

New measurement of G_E/GM for the proton

NASA Astrophysics Data System (ADS)

Segel, Ralph

2003-10-01

Recent polarization transfer measurements of the ratio of the proton electric to magnetic form factor, G E /G_M, find μ_pG E /GM = 1 - 0.13Q ^2 while a long series of L-T separations are fit by μ_pG_E/GM ≈ 1. Jefferson Lab experiment E01-001 used a new technique for making L-T separations that greatly reduces the dominant systematic uncertainties present in previous determinations. Protons from ep scattering were measured over a wide range in ɛ at Q^2 = 2.64, 3.20 and 4.10 GeV^2 and, simultaneously, protons scattered at Q^2 = 0.5 GeV^2 were measured over a small range in ɛ. The Q^2 = 0.5 GeV^2 measurements provided an internal monitor and only kinematic factors and ratios of simultaneously measured cross sections enter into the determinations of G_E/G_M. Measuring the proton cross sections has the advantage that for the same Q^2, count rates change very little with ɛ and also proton momentum is the same at all ɛ thus eliminating the effect of any momentum-dependent inefficiencies. Neither of these is true for L-T separations performed by measuring electron cross sections. Furthermore, the radiative corrections for the proton cross sections are a factor of about 2.5 smaller. All previous L-T separations measured electron cross sections and none had the advantage of an internal monitor. Therefore, the results of E01-001 stringently test whether systematic uncertainties in previous L-T separations may have been sufficient to explain the discrepancy with the recent polarization transfer results.

Measurement of the neutron-capture cross section of ⁷⁶Ge and ⁷⁴Ge below 15 MeV and its relevance to 0νββ decay searches of ⁷⁶Ge

DOE PAGES

Bhike, Megha; Fallin, B.; Krishichayan, none; ...

2015-02-01

The neutron radiative-capture cross section of ⁷⁶Ge was measured between 0.4 and 14.8 MeV using the activation technique. Germanium samples with the isotopic abundance of ~86% ⁷⁶Ge and ~14% ⁷⁴Ge used in the 0νββ searches by the GERDA and Majorana Collaborations were irradiated with monoenergetic neutrons produced at eleven energies via the ³H(p,n)³He, ²H(d,n)³He and ³H(d,n)⁴He reactions. Previously, data existed only at thermal energies and at 14 MeV. As a by-product, capture cross-section data were also obtained for ⁷⁴Ge at neutron energies below 8 MeV. Indium and gold foils were irradiated simultaneously for neutron fluence determination. High-resolution γ-ray spectroscopy wasmore » used to determine the γ-ray activity of the daughter nuclei of interest. For the ⁷⁶Ge total capture cross section the present data are in good agreement with the TENDL-2013 model calculations and the ENDF/B-VII.1 evaluations, while for the ⁷⁴Ge(n,γ)⁷⁵Ge reaction, the present data are about a factor of two larger than predicted. It was found that the ⁷⁴Ge(n,γ)⁷⁵Ge yield in the High-Purity Germanium (HPGe) detectors used by the GERDA and Majorana Collaborations is only about a factor of two smaller than the ⁷⁶Ge(n,γ)⁷⁷Ge yield due to the larger cross section of the former reaction.« less

Measurement of the neutron-capture cross section of ⁷⁶Ge and ⁷⁴Ge below 15 MeV and its relevance to 0νββ decay searches of ⁷⁶Ge

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

Bhike, Megha; Fallin, B.; Krishichayan, none

The neutron radiative-capture cross section of ⁷⁶Ge was measured between 0.4 and 14.8 MeV using the activation technique. Germanium samples with the isotopic abundance of ~86% ⁷⁶Ge and ~14% ⁷⁴Ge used in the 0νββ searches by the GERDA and Majorana Collaborations were irradiated with monoenergetic neutrons produced at eleven energies via the ³H(p,n)³He, ²H(d,n)³He and ³H(d,n)⁴He reactions. Previously, data existed only at thermal energies and at 14 MeV. As a by-product, capture cross-section data were also obtained for ⁷⁴Ge at neutron energies below 8 MeV. Indium and gold foils were irradiated simultaneously for neutron fluence determination. High-resolution γ-ray spectroscopy wasmore » used to determine the γ-ray activity of the daughter nuclei of interest. For the ⁷⁶Ge total capture cross section the present data are in good agreement with the TENDL-2013 model calculations and the ENDF/B-VII.1 evaluations, while for the ⁷⁴Ge(n,γ)⁷⁵Ge reaction, the present data are about a factor of two larger than predicted. It was found that the ⁷⁴Ge(n,γ)⁷⁵Ge yield in the High-Purity Germanium (HPGe) detectors used by the GERDA and Majorana Collaborations is only about a factor of two smaller than the ⁷⁶Ge(n,γ)⁷⁷Ge yield due to the larger cross section of the former reaction.« less

Radiative neutron capture on 242Pu in the resonance region at the CERN n_TOF-EAR1 facility

NASA Astrophysics Data System (ADS)

Lerendegui-Marco, J.; Guerrero, C.; Mendoza, E.; Quesada, J. M.; Eberhardt, K.; Junghans, A. R.; Krtička, M.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Barros, S.; Bečvář, F.; Beinrucker, C.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Furman, V.; Göbel, K.; García, A. R.; Gawlik, A.; Glodariu, T.; Gonçalves, I. F.; González-Romero, E.; Goverdovski, A.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heftrich, T.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kavrigin, P.; Ketlerov, V.; Khryachkov, V.; Kimura, A.; Kivel, N.; Kokkoris, M.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Musumarra, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, J. I.; Praena, J.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Smith, A. G.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Warren, S.; Weigand, M.; Weiss, C.; Wolf, C.; Woods, P. J.; Wright, T.; Žugec, P.; n TOF Collaboration

2018-02-01

The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with uranium to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. However, an extensive use of MOX fuels, in particular in fast reactors, requires more accurate capture and fission cross sections for some Pu isotopes. In the case of 242Pu there are sizable discrepancies among the existing capture cross-section measurements included in the evaluations (all from the 1970s) resulting in an uncertainty as high as 35% in the fast energy region. Moreover, postirradiation experiments evaluated with JEFF-3.1 indicate an overestimation of 14% in the capture cross section in the fast neutron energy region. In this context, the Nuclear Energy Agency (NEA) requested an accuracy of 8% in this cross section in the energy region between 500 meV and 500 keV. This paper presents a new time-of-flight capture measurement on 242Pu carried out at n_TOF-EAR1 (CERN), focusing on the analysis and statistical properties of the resonance region, below 4 keV. The 242Pu(n ,γ ) reaction on a sample containing 95(4) mg enriched to 99.959% was measured with an array of four C6D6 detectors and applying the total energy detection technique. The high neutron energy resolution of n_TOF-EAR1 and the good statistics accumulated have allowed us to extend the resonance analysis up to 4 keV, obtaining new individual and average resonance parameters from a capture cross section featuring a systematic uncertainty of 5%, fulfilling the request of the NEA.

Annular convective-radiative fins with a step change in thickness, and temperature-dependent thermal conductivity and heat transfer coefficient

NASA Astrophysics Data System (ADS)

Barforoush, M. S. M.; Saedodin, S.

2018-01-01

This article investigates the thermal performance of convective-radiative annular fins with a step reduction in local cross section (SRC). The thermal conductivity of the fin's material is assumed to be a linear function of temperature, and heat transfer coefficient is assumed to be a power-law function of surface temperature. Moreover, nonzero convection and radiation sink temperatures are included in the mathematical model of the energy equation. The well-known differential transformation method (DTM) is used to derive the analytical solution. An exact analytical solution for a special case is derived to prove the validity of the obtained results from the DTM. The model provided here is a more realistic representation of SRC annular fins in actual engineering practices. Effects of many parameters such as conduction-convection parameters, conduction-radiation parameter and sink temperature, and also some parameters which deal with step fins such as thickness parameter and dimensionless parameter describing the position of junction in the fin on the temperature distribution of both thin and thick sections of the fin are investigated. It is believed that the obtained results will facilitate the design and performance evaluation of SRC annular fins.

Optical absorption and photoluminescence properties of Er3+ doped mixed alkali borate glasses.

PubMed

Ratnakaram, Y C; Kumar, A Vijaya; Naidu, D Tirupathi; Rao, J L

2005-07-01

An investigations of the optical absorption and fluorescence spectra of 0.2 mol% Er2O3 in mixed alkali borate glasses of the type 67.8B2O3 x xLi2O(32-x)Na2O, 67.8B2O3 x xLi2O(32-x)K2O and 67.8B2O3 x xNa2O(32-x)K2O (where x = 8, 12, 16, 20 and 24) are presented. The glasses were obtained by quenching melts consisting of H3BO3, Li2CO3, Na2CO3, K2CO3 and Er2O3 (950-1100 degrees C, 1.5-2 h) between two brass plates. Spectroscopic parameters like Racah (E1, E2 and E3), spin-orbit (xi(4f)) and configuration interaction (alpha) parameters are deduced as function of x. Using Judd-Ofelt theory, Judd-Ofelt intensity parameters (omega2, omega4 and omega6) are obtained. Radiative and non-radiative transition rates (A(T) and W(MPR)), radiative lifetimes (tauR), branching ratios (beta) and integrated absorption cross-sections (sigma) have been computed for certain excited states of Er3+ in these mixed alkali borate glasses. Emission spectra have been studied for all the three Er3+ doped mixed alkali borate glasses. The present paper throws light on the trends observed in the intensity parameters, radiative lifetimes, branching ratios and emission cross-sections as a function of x in these borate glasses, keeping in view the effect of mixed alkalies in borate glasses.

Hard alpha-keratin degradation inside a tissue under high flux X-ray synchrotron micro-beam: a multi-scale time-resolved study.

PubMed

Leccia, Emilie; Gourrier, Aurélien; Doucet, Jean; Briki, Fatma

2010-04-01

X-rays interact strongly with biological organisms. Synchrotron radiation sources deliver very intense X-ray photon fluxes within micro- or submicro cross-section beams, resulting in doses larger than the MGy. The relevance of synchrotron radiation analyses of biological materials is therefore questionable since such doses, million times higher than the ones used in radiotherapy, can cause huge damages in tissues, with regard to not only DNA, but also proteic and lipid organizations. Very few data concerning the effect of very high X-ray doses in tissues are available in the literature. We present here an analysis of the structural phenomena which occur when the model tissue of human hair is irradiated by a synchrotron X-ray micro-beam. The choice of hair is supported by its hierarchical and partially ordered keratin structure which can be analysed inside the tissue by X-ray diffraction. To assess the damages caused by hard X-ray micro-beams (1 microm(2) cross-section), short exposure time scattering SAXS/WAXS patterns have been recorded at beamline ID13 (ESRF) after various irradiation times. Various modifications of the scattering patterns are observed, they provide fine insight of the radiation damages at various hierarchical levels and also unexpectedly provide information about the stability of the various hierarchical structural levels. It appears that the molecular level, i.e. the alpha helices which are stabilized by hydrogen bonds and the alpha-helical coiled coils which are stabilized by hydrophobic interactions, is more sensitive to radiation than the supramolecular architecture of the keratin filament and the filament packing within the keratin associated proteins matrix, which is stabilized by disulphide bonds. (c) 2009 Elsevier Inc. All rights reserved.

Ionization Cross Sections and Dissociation Channels of DNA Bases by Electron Collisions

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Dateo, Christopher E.; Fletcher, Graham D.

2004-01-01

Free secondary electrons are the most abundant secondary species in ionizing radiation. Their role in DNA damage, both direct and indirect, is an active area of research. While indirect damage by free radicals, particularly by the hydroxyl radical generated by electron collision with water. is relatively well studied, damage by direct electron collision with DNA is less well understood. Only recently Boudaiffa et al. demonstrated that electrons at energies well below ionization thresholds can induce substantial yields of single- and double-strand breaks in DNA by a resonant, dissociative attachment process. This study attracted renewed interest in electron collisions with DNA, especially in the low energy region. At higher energies ionization becomes important. While Monte Carlo track simulations of radiation damage always include ionization, the probability of dissociative ionization, i.e., simultaneous ionization and dissociation, is ignored. Just like dissociative attachment, dissociative ionization may be an important contributor to double-strand breaks since the radicals and ions produced by dissociative ionization, located in the vicinity of the DNA coil, can readily interact with other parts of the DNA. Using the improved binary-encounter dipole (iBED) formulation, we calculated the ionization cross sections of the four DNA bases, adenine, cytosine, guanine, and thymine, by electrons at energies from threshold to 1 KeV. The present calculation gives cross sections approximately 20% lower than the results by Bemhardt and Paretzke using the Deutsch-Mark and Binary-Encounter-Bethe (BEB) formalisms. The difference is most likely due to the lack of a shielding term in the dipole potential used in the Deutsch-Mark and BEB formalisms. The dissociation channels of ionization for the bases are currently being studied.

The e{sup +}e{sup -}{yields}2({pi}{sup +}{pi}{sup -}){pi}{sup 0}, 2({pi}{sup +}{pi}{sup -}){eta}, K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0} and K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{eta} cross sections measured with initial-state radiation

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

Aubert, B.; Bona, M.; Boutigny, D.

We study the processes e{sup +}e{sup -}{yields}2({pi}{sup +}{pi}{sup -}){pi}{sup 0}{gamma}, 2({pi}{sup +}{pi}{sup -}){eta}{gamma}, K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0}{gamma} and K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{eta}{gamma} with the hard photon radiated from the initial state. About 20 000, 4300, 5500, and 375 fully reconstructed events, respectively, are selected from 232 fb{sup -1} of BABAR data. The invariant mass of the hadronic final state defines the effective e{sup +}e{sup -} center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct e{sup +}e{sup -} measurements, currently available only for the {eta}{pi}{sup +}{pi}{supmore » -} and {omega}{pi}{sup +}{pi}{sup -} submodes of the e{sup +}e{sup -}{yields}2({pi}{sup +}{pi}{sup -}){pi}{sup 0} channel. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from e{sup +}e{sup -}{yields}{omega}(782){pi}{sup +}{pi}{sup -} and study the {omega}(1420) and {omega}(1650) resonances. In the charmonium region, we observe the J/{psi} in all these final states and several intermediate states, as well as the {psi}(2S) in some modes, and we measure the corresponding branching fractions.« less

First cross-section measurements of the reactions Ag,109107(p ,γ )Cd,110108 at energies relevant to the p process

NASA Astrophysics Data System (ADS)

Khaliel, A.; Mertzimekis, T. J.; Asimakopoulou, E.-M.; Kanellakopoulos, A.; Lagaki, V.; Psaltis, A.; Psyrra, I.; Mavrommatis, E.

2017-09-01

Background: One of the primary objectives of the field of Nuclear Astrophysics is the study of the elemental and isotopic abundances in the universe. Although significant progress has been made in understanding the mechanisms behind the production of a large number of nuclides in the isotopic chart, there are still many open questions regarding a number of neutron-deficient nuclei, the p nuclei. To that end, experimentally deduced nuclear reaction cross sections can provide invaluable input to astrophysical models. Purpose: The reactions Ag,109107(p ,γ )Cd,110108 have been studied at energies inside the astrophysically relevant energy window in an attempt to provide experimental data required for the testing of reaction-rate predictions in terms of the statistical model of Hauser-Feshbach around the p nucleus 108Cd. Methods: The experiments were performed with in-beam γ -ray spectroscopy with proton beams accelerated by the Tandem Van de Graaff Accelerator at NCSR "Demokritos" impinging a target of natural silver. A set of high-purity germanium detectors was employed to record the emitted radiation. Results: A first set of total cross-section measurements in radiative proton-capture reactions involving Ag,109107, producing the p -nucleus 108Cd, inside the astrophysically relevant energy window is reported. The experimental results are compared to theoretical calculations, using talys. An overall good agreement between the data and the theoretical calculations has been found. Conclusions: The results reported in this work add new information to the relatively unexplored p process. The present measurements can serve as a reference point in understanding the nuclear parameters in the related astrophysical environments and for future theoretical modeling and experimental works.

Diphoton production at the LHC: a QCD study up to NNLO

NASA Astrophysics Data System (ADS)

Catani, Stefano; Cieri, Leandro; de Florian, Daniel; Ferrera, Giancarlo; Grazzini, Massimiliano

2018-04-01

We consider the production of prompt-photon pairs at the LHC and we report on a study of QCD radiative corrections up to the next-to-next-to-leading order (NNLO). We present a detailed comparison of next-to-leading order (NLO) results obtained within the standard and smooth cone isolation criteria, by studying the dependence on the isolation parameters. We highlight the role of different partonic subprocesses within the two isolation criteria, and we show that they produce large radiative corrections for both criteria. Smooth cone isolation is a consistent procedure to compute QCD radiative corrections at NLO and beyond. If photon isolation is sufficiently tight, we show that the NLO results for the two isolation procedures are consistent with each other within their perturbative uncertainties. We then extend our study to NNLO by using smooth cone isolation. We discuss the impact of the NNLO corrections and the corresponding perturbative uncertainties for both fiducial cross sections and distributions, and we comment on the comparison with some LHC data. Throughout our study we remark on the main features that are produced by the kinematical selection cuts that are applied to the photons. In particular, we examine soft-gluon singularities that appear in the perturbative computations of the invariant mass distribution of the photon pair, the transverse-momentum spectra of the photons, and the fiducial cross section with asymmetric and symmetric photon transverse-momentum cuts, and we present their behaviour in analytic form.

Structural and luminescence properties of Dy3+ doped bismuth phosphate glasses for greenish yellow light applications

NASA Astrophysics Data System (ADS)

Damodaraiah, S.; Reddy Prasad, V.; Babu, S.; Ratnakaram, Y. C.

2017-05-01

Different compositions of (5, 10, 15 and 20 mol%) of bismuth and different concentrations (0.5, 1.0, 1.5 and 2.0 mol%) of Dy3+ ion doped bismuth phosphate (BiP) glasses were synthesized by melt-quenching technique. The structural characterization was accomplished by XRD, SEM with EDS, FTIR, FT-Raman and 31P MAS NMR spectroscopy. The optical properties were studied using absorption and photoluminescence spectroscopy. Different structural groups were identified using FTIR and FT-Raman spectra. The depolymerization of metaphosphate chains are described by the decrease of Q2 tetrahedral sites allowing the formation of pyrophosphate groups (Q1) revealed by 31P MAS NMR spectroscopic investigations. Judd-Ofelt intensity parameters Ωλ (λ = 2, 4 and 6) were evaluated from absorption spectra. Radiative parameters such as radiative lifetimes (τR), integrated absorption cross-sections (Σ) and branching ratios (βR) were calculated using Judd-Ofelt intensity parameters. From photoluminescence spectra, experimental branching ratios (βexp) and stimulated emission cross-sections (σP) were calculated for all the observed emission transitions of prepared glasses. The decay profiles for 4F9/2 level were recorded and fit exponential for 0.5 mol% and non-exponential for higher concentrations of Dy3+ due to non-radiative energy transfer among excited Dy3+ ions. The CIE chromaticity co-ordinates have been calculated from the luminescence spectra which confirmed greenish yellow light emission.

Photoproduction and Radiative Decay of η' Meson in CLAS at Jlab

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

Mbianda Njencheu, Georgie

In this work the η' meson photoproduction cross sections as well as the distribution of the di-pion invariant mass, m(π+π-), in the radiative decay mode n' -> π+π-γ have been measured using the CLAS detector at the Thomas Jefferson National Accelerator Facility using tagged incident photons in the center-of-mass energy range 1.96 GeV - 2.72 GeV. The measurements are performed on a liquid hydrogen target in the reaction γ π -> π η'(η'-> π+π-γ). The analysis is based on the highest statistics collected in this decay channel in comparison to other experiments reported so far. The n' photoproduction cross sectionsmore » measured with radiative decay are in a good agreement with results of previous publication from the same data set in CLAS obtained through η' -> π+π-γ decay mode. Two free parameters, α and Β, are extracted from a model-independent fit to the m(π+π-) distribution and their values are found to agree well with recent theoretical expectations. The results of both parameters confirm the existence of the box anomaly, ρ-ω mixing and effects of the a2(1320) tensor meson in the radiative decay of η'.« less

Radiation cross-linking in ultra-high molecular weight polyethylene for orthopaedic applications

NASA Astrophysics Data System (ADS)

Oral, Ebru; Muratoglu, Orhun K.

2007-12-01

The motivation for radiation cross-linking of ultra-high molecular weight polyethylene (UHMWPE) is to increase its wear resistance to be used as bearing surfaces for total joint arthroplasty. However, radiation also leaves behind long-lived residual free radicals in this polymer, the reactions of which can detrimentally affect mechanical properties. In this review, we focus on the radiation cross-linking and oxidative stability of first and second generation highly cross-linked UHMWPEs developed in our laboratory.

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

Seo, Dongcheol; Peterson, B. J.; Lee, Seung Hun

The resistive bolometers have been successfully installed in the midplane of L-port in Korea Superconducting Tokamak Advanced Research (KSTAR) device. The spatial and temporal resolutions, 4.5 cm and {approx}1 kHz, respectively, enable us to measure the radial profile of the total radiated power from magnetically confined plasma at a high temperature through radiation and neutral particles. The radiated power was measured at all shots. Even at low plasma current, the bolometer signal was detectable. The electron cyclotron resonance heating (ECH) has been used in tokamak for ECH assisted start-up and plasma control by local heating and current drive. The detectorsmore » of resistive bolometer, near the antenna of ECH, are affected by electron cyclotron wave. The tomographic reconstruction, using the Phillips-Tikhonov regularization method, will be carried out for a major radial profile of the radiation emissivity of the circular cross-section plasma.« less

Demonstration of Hybrid Multilayer Insulation for Fixed Thickness Applications

NASA Technical Reports Server (NTRS)

Johnson, Wesley; Fesmire, James; Heckle, Wayne

2015-01-01

Once on orbit, high performing insulation systems for cryogenic systems need just as good radiation (optical) properties as conduction properties. This requires the use of radiation shields with low conductivity spacers in between. By varying the height and cross-sectional area of the spacers between the radiation shields, the relative radiation and conduction heat transfers can be manipulated. However, in most systems, there is a fixed thickness or volume allocated to the insulation. In order to understand how various combinations of different multilayer insulation (MLI) systems work together and further validate thermal models of such a hybrid MLI set up, test data is needed. The MLI systems include combinations of Load Bearing MLI (LB-MLI) and traditional MLI. To further simulate the space launch vehicle case wherein both ambient pressure and vacuum environments are addressed, different cold-side thermal insulation substrates were included for select tests.

Study of high speed complex number algorithms. [for determining antenna for field radiation patterns

NASA Technical Reports Server (NTRS)

Heisler, R.

1981-01-01

A method of evaluating the radiation integral on the curved surface of a reflecting antenna is presented. A three dimensional Fourier transform approach is used to generate a two dimensional radiation cross-section along a planer cut at any angle phi through the far field pattern. Salient to the method is an algorithm for evaluating a subset of the total three dimensional discrete Fourier transform results. The subset elements are selectively evaluated to yield data along a geometric plane of constant. The algorithm is extremely efficient so that computation of the induced surface currents via the physical optics approximation dominates the computer time required to compute a radiation pattern. Application to paraboloid reflectors with off-focus feeds in presented, but the method is easily extended to offset antenna systems and reflectors of arbitrary shapes. Numerical results were computed for both gain and phase and are compared with other published work.

Polycyclic aromatic hydrocarbon optical properties and contribution to the acceleration of stellar outflows

NASA Technical Reports Server (NTRS)

Cherchneff, Isabelle; Barker, John R.; Tielens, Alexander G. G. M.

1991-01-01

The optical constants of four polycyclic aromatic hydrocarbon (PAH) molecules (benzene, pyrene, pentacene, and coronene) are determined from their measured laboratory absorption spectra. The Planck mean of the radiation pressure cross section is computed for each molecule and for amorphous carbon (AC) grains, and semiempirically estimated for large PAH molecules up to 400 carbon atoms. Assuming that PAHs are present in carbon-rich stellar outflows, the radiation pressure forces acting on them are calculated and compared with the radiation forces on AC particles. The results show that PAHs possess very different optical properties from AC grains. Small PAHs may experience an 'inverse greenhouse' effect in the inner part of the envelope, as they decouple from the gas close to the photosphere. The radiation pressure force on PAHs is always much less than the force at work on AC grains, and PAH molecules do not affect significantly the dynamics of the outflow.

Search for magnetic monopoles in lunar material.

NASA Technical Reports Server (NTRS)

Eberhard, P. H.; Ross, R. R.; Alvarez, L. W.; Watt, R. D.

1971-01-01

A search for magnetic monopoles in lunar material has been performed by the electromagnetic measurement of the magnetic charge of samples. All measurements were found consistent with zero charge for all samples and inconsistent with any other value allowed by the Dirac theory. Upper limits are determined for the monopole flux in cosmic radiation and for the pair-production cross section in proton-nucleon collisions.

A simple and fast method for computing the relativistic Compton Scattering Kernel for radiative transfer

NASA Technical Reports Server (NTRS)

Kershaw, David S.; Prasad, Manoj K.; Beason, J. Douglas

1986-01-01

The Klein-Nishina differential cross section averaged over a relativistic Maxwellian electron distribution is analytically reduced to a single integral, which can then be rapidly evaluated in a variety of ways. A particularly fast method for numerically computing this single integral is presented. This is, to the authors' knowledge, the first correct computation of the Compton scattering kernel.

LABCEDE Fluorescence Investigations

DTIC Science & Technology

1988-08-01

the B state is preferentially formed in lower energy spin states, either by direct electron impact or by radiative cascade. However, comparison with dir... impact excitation cross sections for these states at 4.5 kV are small and much of the excitation comes from lower energy secondary electrons created by... impact and energy pooling are significantly different. Experimentally, the C-state vibrational distribution is accurately determined from the spectrum

Blois 5: Experimental summary

NASA Astrophysics Data System (ADS)

Albrow, M. G.

1993-09-01

The author gives a summary talk of the best experimental data given at the 5th Blois Workshop on Elastic and Diffractive Scattering. He addresses the following eight areas in his talk: total and elastic cross sections; single diffractive excitation; electron-proton scattering; di-jets and rapidity gaps; areas of future study; spins and asymmetries; high-transverse momentum and masses at the Tevatron; and disoriented chiral condensates and cosmic radiation.

Assessment of radiation protection practices among radiographers in Lagos, Nigeria.

PubMed

Eze, Cletus Uche; Abonyi, Livinus Chibuzo; Njoku, Jerome; Irurhe, Nicholas Kayode; Olowu, Oluwabola

2013-11-01

Use of ionising radiation in diagnostic radiography could lead to hazards such as somatic and genetic damages. Compliance to safe work and radiation protection practices could mitigate such risks. The aim of the study was to assess the knowledge and radiation protection practices among radiographers in Lagos, Nigeria. The study was a prospective cross sectional survey. Convenience sampling technique was used to select four x-ray diagnostic centres in four tertiary hospitals in Lagos metropolis. Data were analysed with Epi- info software, version 3.5.1. Average score on assessment of knowledge was 73%. Most modern radiation protection instruments were lacking in all the centres studied. Application of shielding devices such as gonad shield for protection was neglected mostly in government hospitals. Most x-ray machines were quite old and evidence of quality assurance tests performed on such machines were lacking. Radiographers within Lagos metropolis showed an excellent knowledge of radiation protection within the study period. Adherence to radiation protection practices among radiographers in Lagos metropolis during the period studied was, however, poor. Radiographers in Lagos, Nigeria should embrace current trends in radiation protection and make more concerted efforts to apply their knowledge in protecting themselves and patients from harmful effects of ionising radiation.

Fractal scaling laws of black carbon aerosol and their influence on spectral radiative properties

NASA Astrophysics Data System (ADS)

Tiwari, S.; Chakrabarty, R. K.; Heinson, W.

2016-12-01

Current estimates of the direct radiative forcing for Black Carbon (BC) aerosol span over a poorly constrained range between 0.2 and 1 W.m-2. To improve this large uncertainty, tighter constraints need to be placed on BC's key wavelength-dependent optical properties, namely, the absorption (MAC) and scattering (MSC) cross sections per unit mass and hemispherical upscatter fraction (β; a dimensionless scattering directionality parameter). These parameters are very sensitive to changes in particle morphology and complex refractive index nindex. Their interplay determines the magnitude of net positive or negative radiative forcing efficiencies. The current approach among climate modelers for estimating MAC and MSC values of BC is from their optical cross-sections calculated assuming spherical particle morphology with homogeneous, constant-valued refractive index in the visible solar spectrum. The β values are typically assumed to be a constant across this spectrum. This approach, while being computationally inexpensive and convenient, ignores the inherent fractal morphology of BC and its scaling behaviors, and resulting optical properties. In this talk, I will present recent results from my laboratory on determination of the fractal scaling laws of BC aggregate packing density and its complex refractive index for size spanning across three orders of magnitude, and their effects on spectral (Visible-infrared wavelength) scaling of MAC, MSC, and β values. Our experiments synergistically combined novel BC generation techniques, aggregation models, contact-free multi-wavelength optical measurements, and electron microscopy analysis. The scale dependence of nindex on aggregate size followed power-law exponents of -1.4 and -0.5 for sub- and super-micron size aggregates, respectively. The spherical Rayleigh-optics approximation limits, used by climate models for spectral extrapolation of BC optical cross-sections and deconvolution of multi-species mixing ratios, are redefined using the concept of phase shift parameter. I will highlight the importance of size-dependent β values and its role in offsetting the strong light absorbing nature of BC. Finally, the errors introduced in forcing efficiency calculations of BC by assuming spherical homogeneous morphology will be evaluated.

{{\\rm{H}}}_{2}\\,X{}^{1}{{\\rm{\\Sigma }}}_{g}^{+}-c{}^{3}{{\\rm{\\Pi }}}_{u} Excitation by Electron Impact: Energies, Spectra, Emission Yields, Cross-sections, and H(1s) Kinetic Energy Distributions

NASA Astrophysics Data System (ADS)

Liu, Xianming; Shemansky, Donald E.; Yoshii, Jean; Liu, Melinda J.; Johnson, Paul V.; Malone, Charles P.; Khakoo, Murtadha A.

2017-10-01

The c{}3{{{\\Pi }}}u state of the hydrogen molecule has the second largest triplet-state excitation cross-section, and plays an important role in the heating of the upper thermospheres of outer planets by electron excitation. Precise energies of the H2, D2, and HD c{}3{{{\\Pi }}}u-(v,N) levels are calculated from highly accurate ab initio potential energy curves that include relativistic, radiative, and empirical non-adiabatic corrections. The emission yields are determined from predissociation rates and refined radiative transition probabilities. The excitation function and excitation cross-section of the c{}3{{{\\Pi }}}u state are extracted from previous theoretical calculations and experimental measurements. The emission cross-section is determined from the calculated emission yield and the extracted excitation cross-section. The kinetic energy (E k ) distributions of H atoms produced via the predissociation of the c{}3{{{\\Pi }}}u state, the c{}3{{{\\Pi }}}u- - b{}3{{{Σ }}}u+ dissociative emission by the magnetic dipole and electric quadrupole, and the c{}3{{{\\Pi }}}u - a{}3{{{Σ }}}g+ - b{}3{{{Σ }}}u+ cascade dissociative emission by the electric dipole are obtained. The predissociation of the c{}3{{{\\Pi }}}u+ and c{}3{{{\\Pi }}}u- states both produce H(1s) atoms with an average E k of ˜4.1 eV/atom, while the c{}3{{{\\Pi }}}u- - b{}3{{{Σ }}}u+ dissociative emissions by the magnetic dipole and electric quadrupole give an average E k of ˜1.0 and ˜0.8 eV/atom, respectively. The c{}3{{{\\Pi }}}u - a{}3{{{Σ }}}g+ - b{}3{{{Σ }}}u+ cascade and dissociative emission gives an average E k of ˜1.3 eV/atom. On average, each H2 excited to the c{}3{{{\\Pi }}}u state in an H2-dominated atmosphere deposits ˜7.1 eV into the atmosphere while each H2 directly excited to the a{}3{{{Σ }}}g+ and d{}3{{{\\Pi }}}u states contribute ˜2.3 and ˜3.3 eV, respectively, to the atmosphere. The spectral distribution of the calculated continuum emission arising from the X{}1{{{Σ }}}g+ - c{}3{{{\\Pi }}}u excitation is significantly different from that of direct a{}3{{{Σ }}}g+ or d{}3{{{\\Pi }}}u excitations.

Reducing Cross-Polarized Radiation From A Microstrip Antenna

NASA Technical Reports Server (NTRS)

Huang, John

1991-01-01

Change in configuration of feed of nominally linearly polarized microstrip-patch transmitting array antenna reduces cross-polarized component of its radiation. Patches fed on opposing sides, in opposite phases. Combination of spatial symmetry and temporal asymmetry causes copolarized components of radiation from fundamental modes of patches to reinforce each other and cross-polarized components of radiation from higher-order modes to cancel each other.

Monte Carlo simulation of proton track structure in biological matter

DOE PAGES

Quinto, Michele A.; Monti, Juan M.; Weck, Philippe F.; ...

2017-05-25

Here, understanding the radiation-induced effects at the cellular and subcellular levels remains crucial for predicting the evolution of irradiated biological matter. In this context, Monte Carlo track-structure simulations have rapidly emerged among the most suitable and powerful tools. However, most existing Monte Carlo track-structure codes rely heavily on the use of semi-empirical cross sections as well as water as a surrogate for biological matter. In the current work, we report on the up-to-date version of our homemade Monte Carlo code TILDA-V – devoted to the modeling of the slowing-down of 10 keV–100 MeV protons in both water and DNA –more » where the main collisional processes are described by means of an extensive set of ab initio differential and total cross sections.« less

Influence of depositional environment in fossil teeth: a micro-XRF and XAFS study

NASA Astrophysics Data System (ADS)

Zougrou, I. M.; Katsikini, M.; Pinakidou, F.; Papadopoulou, L.; Tsoukala, E.; Paloura, E. C.

2014-04-01

The formation of metal-rich phases during the fossilization of vertebrate fossil teeth, recovered from various deposition environments in northern Greece, is studied by means of synchrotron radiation X-ray fluorescence (SR-XRF) as well as Fe and Mn K edge X-ray absorption fine structure (XAFS) spectroscopy. XRF line-scans from the samples' cross-sections revealed different contamination paths for Mn and Fe. The two-dimensional XRF maps illustrate the spatial distribution of P, Ca, Mn and Fe as well as the precipitation of Fe-rich phases in cementum, dentin and dentinal tubules. Goethite, lepidocrocite and ferrihydrite were detected in the samples' cross-section by means of Fe K edge EXAFS spectroscopy. Moreover the Fe and Mn K edge EXAFS revealed the presence of vivianite and birnessite (MnO2) on the external surface of two samples.

Kinetics of color center formation in silica irradiated with swift heavy ions: Thresholding and formation efficiency

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

Manzano-Santamaria, J.; Euratom/CIEMAT Fusion Association, Madrid; Olivares, J.

2012-10-08

We have determined the cross-section {sigma} for color center generation under single Br ion impacts on amorphous SiO{sub 2}. The evolution of the cross-sections, {sigma}(E) and {sigma}(S{sub e}), show an initial flat stage that we associate to atomic collision mechanisms. Above a certain threshold value (S{sub e} > 2 keV/nm), roughly coinciding with that reported for the onset of macroscopic disorder (compaction), {sigma} shows a marked increase due to electronic processes. In this regime, a energetic cost of around 7.5 keV is necessary to create a non bridging oxygen hole center-E Prime (NBOHC/E Prime ) pair, whatever the input energy.more » The data appear consistent with a non-radiative decay of self-trapped excitons.« less

Rate-coefficients and polarization results for the electron-impact excitation of Ar+ ion

NASA Astrophysics Data System (ADS)

Srivastava, Rajesh; Dipti, Dipti

2016-05-01

A fully relativistic distorted wave theory has been employed to study the electron impact excitation in Ar+ ion. Results have been obtained for the excitation cross-sections and rate-coefficients for the transitions from the ground state 3p5 (J = 3/2) to fine-structure levels of excited states 3p4 4 s, 3p4 4 p , 3p4 5 s, 3p4 5 p, 3p4 3 d and 3p4 4 d. Polarization of the radiation following the excitation has been calculated using the obtained magnetic sub-level cross-sections. Comparison of the present rate-coefficients is also done with the previously reported theoretical results for some unresolved fine structure transitions. Work is supported by DAE-BRNS Mumbai and CSIR, New Delhi.

HZETRN: A heavy ion/nucleon transport code for space radiations

NASA Technical Reports Server (NTRS)

Wilson, John W.; Chun, Sang Y.; Badavi, Forooz F.; Townsend, Lawrence W.; Lamkin, Stanley L.

1991-01-01

The galactic heavy ion transport code (GCRTRN) and the nucleon transport code (BRYNTRN) are integrated into a code package (HZETRN). The code package is computer efficient and capable of operating in an engineering design environment for manned deep space mission studies. The nuclear data set used by the code is discussed including current limitations. Although the heavy ion nuclear cross sections are assumed constant, the nucleon-nuclear cross sections of BRYNTRN with full energy dependence are used. The relation of the final code to the Boltzmann equation is discussed in the context of simplifying assumptions. Error generation and propagation is discussed, and comparison is made with simplified analytic solutions to test numerical accuracy of the final results. A brief discussion of biological issues and their impact on fundamental developments in shielding technology is given.

The HITRAN 2008 Molecular Spectroscopic Database

NASA Technical Reports Server (NTRS)

Rothman, Laurence S.; Gordon, Iouli E.; Barbe, Alain; Benner, D. Chris; Bernath, Peter F.; Birk, Manfred; Boudon, V.; Brown, Linda R.; Campargue, Alain; Champion, J.-P.;

Monte Carlo simulation of proton track structure in biological matter

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

Quinto, Michele A.; Monti, Juan M.; Weck, Philippe F.

Here, understanding the radiation-induced effects at the cellular and subcellular levels remains crucial for predicting the evolution of irradiated biological matter. In this context, Monte Carlo track-structure simulations have rapidly emerged among the most suitable and powerful tools. However, most existing Monte Carlo track-structure codes rely heavily on the use of semi-empirical cross sections as well as water as a surrogate for biological matter. In the current work, we report on the up-to-date version of our homemade Monte Carlo code TILDA-V – devoted to the modeling of the slowing-down of 10 keV–100 MeV protons in both water and DNA –more » where the main collisional processes are described by means of an extensive set of ab initio differential and total cross sections.« less

Analysis of the Browns Ferry Unit 3 irradiation experiments. Final report

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

Simmons, G.L.

1984-11-01

The results of the analysis of two experiments performed at the Browns Ferry-3 reactor are presented. These calculations utilize state-of-the-art neutron transport techniques and a new neutron cross-section library that has been developed for LWR applications. The calculations agree well with the experimental data obtained in irradiations inside the reactor vessel. For the measurements performed in the reactor cavity, the calculations agree well at the reactor midplane. Accurate determination of the axial distribution of the neutron fluence in the reactor cavity depends on having a concise representation of the axial-void distribution in the core. Detailed data are presented describing themore » procedures used in the generation of the new cross-section library that has been named SAILOR. This library is available from the Radiation-Shielding Information Center.« less

Combining the absorptive and radiative loss in metasurfaces for multi-spectral shaping of the electromagnetic scattering.

PubMed

Pan, Wenbo; Huang, Cheng; Pu, Mingbo; Ma, Xiaoliang; Cui, Jianhua; Zhao, Bo; Luo, Xiangang

2016-02-19

The absorptive and radiative losses are two fundamental aspects of the electromagnetic responses, which are widely occurring in many different systems such as waveguides, solar cells, and antennas. Here we proposed a metasurface to realize the control of the absorptive and radiative loss and to reduce the radar cross section (RCS) in multi-frequency bands. The anti-phase gradient and absorptive metasurfaces were designed that consists of metallic square patch and square loop structure inserted with resistors, acting as an phase gradient material in the X and Ku band, while behaving as an absorber in the S band. The simulation and experiment results verified the double-band, wideband and polarization-independent RCS reduction by the absorptive and anti-phase gradient metasurfaces.

Perturbed effects at radiation physics

NASA Astrophysics Data System (ADS)

Külahcı, Fatih; Şen, Zekâi

2013-09-01

Perturbation methodology is applied in order to assess the linear attenuation coefficient, mass attenuation coefficient and cross-section behavior with random components in the basic variables such as the radiation amounts frequently used in the radiation physics and chemistry. Additionally, layer attenuation coefficient (LAC) and perturbed LAC (PLAC) are proposed for different contact materials. Perturbation methodology provides opportunity to obtain results with random deviations from the average behavior of each variable that enters the whole mathematical expression. The basic photon intensity variation expression as the inverse exponential power law (as Beer-Lambert's law) is adopted for perturbation method exposition. Perturbed results are presented not only in terms of the mean but additionally the standard deviation and the correlation coefficients. Such perturbation expressions provide one to assess small random variability in basic variables.

Measurements of event properties and multi-differential jet cross sections and impact of CMS measurements on Proton Structure and QCD parameters

NASA Astrophysics Data System (ADS)

Kaur, Anterpreet

2018-01-01

We present results on the measurements of characteristics of events with jets including jet-charge, investigations of shapes and jet mass distributions. The measurements are compared to theoretical predictions including those matched to parton shower and hadronization. Multi-differential jet cross sections are also presented over a wide range in transverse momenta from inclusive jets to multi-jet final states. These measurements have an impact on the determination of the strong coupling constant as well as on parton distribution functions (PDFs) and are helpful in the treatment of heavy flavours in QCD analyses. We also show angular correlations in multi-jet events at highest center-of-mass energies and compare the measurements to theoretical predictions including higher order parton radiation and coherence effects. Measurements of cross sections of jet and top-quark pair production are in particular sensitive to the gluon distribution in the proton, while the electroweak boson production - inclusive or associated with charm or beauty quarks - gives insight into the flavour separation of the proton sea and to the treatment of heavy quarks in PDF-related studies.

A subleading operator basis and matching for gg → H

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

Moult, Ian; Stewart, Iain W.; Vita, Gherardo

The Soft Collinear Effective Theory (SCET) is a powerful framework for studying factorization of amplitudes and cross sections in QCD. While factorization at leading power has been well studied, much less is known at subleading powers in the λ << 1 expansion. In SCET subleading soft and collinear corrections to a hard scattering process are described by power suppressed operators, which must be fixed case by case, and by well established power suppressed Lagrangians, which correct the leading power dynamics of soft and collinear radiation. Here we present a complete basis of power suppressed operators for gg → H, classifyingmore » all operators which contribute to the cross section at O(λ 2), and showing how helicity selection rules significantly simplify the construction of the operator basis. We perform matching calculations to determine the tree level Wilson coefficients of our operators. These results are useful for studies of power corrections in both resummed and fixed order perturbation theory, and for understanding the factorization properties of gauge theory amplitudes and cross sections at subleading power. As one example, our basis of operators can be used to analytically compute power corrections for N -jettiness subtractions for gg induced color singlet production at the LHC.« less

Intrinsic hybrid modes in a corrugated conical horn

NASA Astrophysics Data System (ADS)

Dendane, A.; Arnold, J. M.

1988-08-01

Computational requirements for the generation of intrinsic modes in a nonseparable waveguide geometry requiring a full vector field description with anistropic impedance boundaries were derived. Good agreement is shown between computed and measured radiation patterns in copolar and crosspolar configurations. This agreement establishes that the intrinsic mode correctly accounts for the local normal mode conversion which takes place along the horn in a conventional mode coupling scheme, at least for cone semiangles up to 15 deg. The advantage of the intrinsic mode formulation over the conventional mode-coupling theory is that, to construct a single intrinsic mode throughout the horn, only one local normal mode field is required at each cross section, whereas mode conversion from the HE11 mode would require all the HE1n modes to be known at each cross section. The intrinsic mode accounts also for fields which would appear as backward modes in coupled-mode theory. A complete coupled-mode theory solution requires the inversion of a large matrix at each cross section, whereas the intrinsic mode can be constructed explicitly using a simple Fourier-like integral; the perturbation solution of Dragone (1977) is difficult to make rigorous.

Testing of the ABBN-RF multigroup data library in photon transport calculations

NASA Astrophysics Data System (ADS)

Koscheev, Vladimir; Lomakov, Gleb; Manturov, Gennady; Tsiboulia, Anatoly

2017-09-01

Gamma radiation is produced via both of nuclear fuel and shield materials. Photon interaction is known with appropriate accuracy, but secondary gamma ray production known much less. The purpose of this work is studying secondary gamma ray production data from neutron induced reactions in iron and lead by using MCNP code and modern nuclear data as ROSFOND, ENDF/B-7.1, JEFF-3.2 and JENDL-4.0. Results of calculations show that all of these nuclear data have different photon production data from neutron induced reactions and have poor agreement with evaluated benchmark experiment. The ABBN-RF multigroup cross-section library is based on the ROSFOND data. It presented in two forms of micro cross sections: ABBN and MATXS formats. Comparison of group-wise calculations using both ABBN and MATXS data to point-wise calculations with the ROSFOND library shows a good agreement. The discrepancies between calculation and experimental C/E results in neutron spectra are in the limit of experimental errors. For the photon spectrum they are out of experimental errors. Results of calculations using group-wise and point-wise representation of cross sections show a good agreement both for photon and neutron spectra.

A subleading operator basis and matching for gg → H

DOE PAGES

Moult, Ian; Stewart, Iain W.; Vita, Gherardo

2017-07-01

The Soft Collinear Effective Theory (SCET) is a powerful framework for studying factorization of amplitudes and cross sections in QCD. While factorization at leading power has been well studied, much less is known at subleading powers in the λ << 1 expansion. In SCET subleading soft and collinear corrections to a hard scattering process are described by power suppressed operators, which must be fixed case by case, and by well established power suppressed Lagrangians, which correct the leading power dynamics of soft and collinear radiation. Here we present a complete basis of power suppressed operators for gg → H, classifyingmore » all operators which contribute to the cross section at O(λ 2), and showing how helicity selection rules significantly simplify the construction of the operator basis. We perform matching calculations to determine the tree level Wilson coefficients of our operators. These results are useful for studies of power corrections in both resummed and fixed order perturbation theory, and for understanding the factorization properties of gauge theory amplitudes and cross sections at subleading power. As one example, our basis of operators can be used to analytically compute power corrections for N -jettiness subtractions for gg induced color singlet production at the LHC.« less

Total Ionizing Dose Influence on the Single-Event Upset Sensitivity of 130-nm PD SOI SRAMs

NASA Astrophysics Data System (ADS)

Zheng, Qiwen; Cui, Jiangwei; Liu, Mengxin; Zhou, Hang; Liu, Mohan; Wei, Ying; Su, Dandan; Ma, Teng; Lu, Wu; Yu, Xuefeng; Guo, Qi; He, Chengfa

2017-07-01

Effect of total ionizing dose (TID) on single-event upset (SEU) hardness of 130 nm partially depleted (PD) silicon-on-insulator (SOI) static random access memories (SRAMs) is investigated in this paper. The measurable synergistic effect of TID on SEU sensitivity of 130-nm PD SOI SRAM was observed in our experiment, even though that is far less than micrometer and submicrometer devices. Moreover, SEU cross section after TID irradiation has no dependence on the data pattern that was applied during TID exposure: SEU cross sections are characterized by TID data pattern and its complement data pattern are decreased consistently rather than a preferred state and a nonpreferred state as micrometer and sub-micrometer SRAMs. The memory cell test structure allowing direct measurement of static noise margin (SNM) under standby operation was designed using identical memory cell layout of SRAM. Direct measurement of the memory cell SNM shows that both data sides' SNM is decreased by TID, indicating that SEU cross section of 130-nm PD SOI SRAM will be increased by TID. And, the decreased SNM is caused by threshold shift in memory cell transistors induced by “radiation-induced narrow channel effect”.

A formula for calculating theoretical photoelectron fluxes resulting from the He/+/ 304 A solar spectral line

NASA Technical Reports Server (NTRS)

Richards, P. G.; Torr, D. G.

1981-01-01

A simplified method for the evaluation of theoretical photoelectron fluxes in the upper atmosphere resulting from the solar radiation at 304 A is presented. The calculation is based on considerations of primary and cascade (secondary) photoelectron production in the two-stream model, where photoelectron transport is described by two electron streams, one moving up and one moving down, and of loss rates due to collisions with neutral gases and thermal electrons. The calculation is illustrated for the case of photoelectrons at an energy of 24.5 eV, and it is noted that the 24.5-eV photoelectron flux may be used to monitor variations in the solar 304 A flux. Theoretical calculations based on various ionization and excitation cross sections of Banks et al. (1974) are shown to be in generally good agreement with AE-E measurements taken between 200 and 235 km, however the use of more recent, larger cross sections leads to photoelectron values a factor of two smaller than observations but in agreement with previous calculations. It is concluded that a final resolution of the photoelectron problem may depend on a reevaluation of the inelastic electron collision cross sections.