Observations of thermal and suprathermal tail ions from WIND

Science.gov (United States)

Randol, B. M.; Christian, E. R.; Wilson, L. B., III

2016-12-01

The velocity distribution function (VDF) of solar wind protons (as well as other ion populations) is comprised of a thermal Maxwellian core and an accelerated suprathermal tail, beginning at around 1 keV in the frame co-moving with solar wind bulk velocity. The form of the suprathermal tail is a power law in phase space density, f, vs. speed, v, such that f / vγ, where γ is the power law index. This commonly observed index is of particular interest because no traditional theory predicts its existence. We need more data in order to test these theories. The general shape is of interest because it is kappa-like. We show combined observations from three different instruments on the WIND spacecraft: 3DP/PLSP, STICS, and 3DP/SST/Open. These data stretch from 102 to 107 eV in energy, encompassing both the thermal and suprathermal proton populations. We show further evidence for this kappa-like distribution and report on our progress on fitting of empirical functions to these data.

Heating and generation of suprathermal particles at collisionless shocks

International Nuclear Information System (INIS)

Thomsen, M.F.

1985-01-01

Collisionless plasma shocks are different from ordinary collisional fluid shocks in several important respects. They do not in general heat the electrons and ions equally, nor do they produce Maxwellian velocity distributions downstream. Furthermore, they commonly generate suprathermal particles which propagate into the upstream region, giving advance warning of the presence of the shock and providing a ''seed'' population for further acceleration to high energies. Recent space observations and theory have revealed a great deal about the heating mechanisms which occur in collisionless shocks and about the origin of the various suprathermal particle populations which are found in association with them. An overview of the present understanding of these subjects is presented herein. 83 refs., 8 figs

Investigation of the role of electron cyclotron resonance heating and magnetic configuration on the suprathermal ion population in the stellarator TJ-II using a luminescent probe

Science.gov (United States)

Martínez, M.; Zurro, B.; Baciero, A.; Jiménez-Rey, D.; Tribaldos, V.

2018-02-01

Numerous observation exist of a population of high energetic ions with energies well above the corresponding thermal values in plasmas generated by electron cyclotron resonance (ECR) heating in TJ-II stellarator and in other magnetically confined plasmas devices. In this work we study the impact of ECR heating different conditions (positions and powers) on fast ions escaping from plasmas in the TJ-II stellarator. For this study, an ion luminescent probe operated in counting mode is used to measure the energy distribution of suprathermal ions, in the range from 1 to 30 keV. It is observed that some suprathermal ions characteristics (such as temperature, particle and energy fluxes) are related directly with the gyrotron power and focus position of the heating beam in the plasma. Moreover, it is found that suprathermal ion characteristics vary during a magnetic configuration scan (performed along a single discharge). By investigating the suprathermal ions escaping from plasmas generated using two gyrotrons, one with fixed power and the other modulated (on/off) at low frequency (10 Hz), the de-confinement time of the suprathermal ions can be measured, which is of the order of a few milliseconds (power balance is used to understand the de-confinement times in terms of the interaction of suprathermal ions and plasma components. This model also can be used to interpret experimental results of energy loss due to suprathermal ions. Finally, observations of increases (peaks) in the population of escaping suprathermal ions, which are well localized at discrete energies, is documented, these peaks being observed in the energy distributions along a discharge.

Generation of Suprathermal Electrons by Collective Processes in Collisional Plasma

Science.gov (United States)

Tigik, S. F.; Ziebell, L. F.; Yoon, P. H.

2017-11-01

The ubiquity of high-energy tails in the charged particle velocity distribution functions (VDFs) observed in space plasmas suggests the existence of an underlying process responsible for taking a fraction of the charged particle population out of thermal equilibrium and redistributing it to suprathermal velocity and energy ranges. The present Letter focuses on a new and fundamental physical explanation for the origin of suprathermal electron velocity distribution function (EVDF) in a collisional plasma. This process involves a newly discovered electrostatic bremsstrahlung (EB) emission that is effective in a plasma in which binary collisions are present. The steady-state EVDF dictated by such a process corresponds to a Maxwellian core plus a quasi-inverse power-law tail, which is a feature commonly observed in many space plasma environments. In order to demonstrate this, the system of self-consistent particle- and wave-kinetic equations are numerically solved with an initially Maxwellian EVDF and Langmuir wave spectral intensity, which is a state that does not reflect the presence of EB process, and hence not in force balance. The EB term subsequently drives the system to a new force-balanced steady state. After a long integration period it is demonstrated that the initial Langmuir fluctuation spectrum is modified, which in turn distorts the initial Maxwellian EVDF into a VDF that resembles the said core-suprathermal VDF. Such a mechanism may thus be operative at the coronal source region, which is characterized by high collisionality.

Spatial variations in the suprathermal ion distributions during substorms in the plasma sheet

International Nuclear Information System (INIS)

Kistler, L.M.; Moebius, E.; Klecker, B.; Gloeckler, G.; Ipavich, F.M.; Hamilton, D.C.

1990-01-01

Using data from AMPTE IRM and AMPTE CCE, the authors have determined the pre- and post-injection suprathermal energy spectra for the ion species H + , O + , He + , and He ++ for six events in which substorm-associated particle injections are observed in both the near-Earth plasma sheet and farther down the tail. They find similar spectral changes in both locations, with the spectra becoming harder with the injection. Post-injection, the flux decreases exponentially with radial distance. Approximately the same gradient is observed in all species. In addition, they find that although the O + /H + and the He ++ /H + ratios increase with energy per charge, the ratios are approximately the same at the same energy per charge at the two spacecraft. The observations are difficult to explain either with a model in which the ions are accelerated at a neutral line and transported toward Earth or with a model in which the ions are accelerated in the near-Earth region by current disruption/diversion and transported down the tail. In either case, the ions would have to be transported throughout the tail without much energization or deenergization in order to explain the energy per charge correlations. Further, earthward transport without energization would not lead to the observed radial gradient. A combination of these acceleration mechanisms, a disturbance that propagates throughout the plasma sheet, or a more global mechanism may explain the observations

Ignition and burn propagation with suprathermal electron auxiliary heating

International Nuclear Information System (INIS)

Han Shensheng; Wu Yanqing

2000-01-01

The rapid development in ultrahigh-intensity lasers has allowed the exploration of applying an auxiliary heating technique in inertial confinement fusion (ICF) research. It is hoped that, compared with the 'standard fast ignition' scheme, raising the temperature of a hot-spot over the ignition threshold based on the shock-heated temperature will greatly reduce the required output energy of an ignition ultrahigh-intensity pulse. One of the key issues in ICF auxiliary heating is: how can we transport the exogenous energy efficiently into the hot-spot of compressed DT fuel? A scheme is proposed with three phases. First, a partial-spherical-shell capsule, such as double-conical target, is imploded as in the conventional approach to inertial fusion to assemble a high-density fuel configuration with a hot-spot of temperature lower than the ignition threshold. Second, a hole is bored through the shell outside the hot-spot by suprathermal electron explosion boring. Finally, the fuel is ignited by suprathermal electrons produced in the high-intensity ignition laser-plasma interactions. Calculations with a simple hybrid model show that the new scheme can possibly lead to ignition and burn propagation with a total drive energy of a few tens of kilojoules and an output energy as low as hundreds of joules for a single ignition ultrahigh-intensity pulse. (author)

Stair-Step Particle Flux Spectra on the Lunar Surface: Evidence for Nonmonotonic Potentials?

Science.gov (United States)

Collier, Michael R.; Newheart, Anastasia; Poppe, Andrew R.; Hills, H. Kent; Farrell, William M.

2016-01-01

We present examples of unusual "stair-step" differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e.,potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface-based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote-sensing orbiter observations on the Moon's exospheric and electrostatic properties.

SUPRATHERMAL ELECTRONS AT SATURN'S BOW SHOCK

International Nuclear Information System (INIS)

Masters, A.; Dougherty, M. K.; Sulaiman, A. H.; Sergis, N.; Stawarz, L.; Fujimoto, M.; Coates, A. J.

2016-01-01

The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach number) than these SNR shocks. However, the Cassini spacecraft has shown that the shock standing in the solar wind sunward of Saturn (Saturn's bow shock) can occasionally reach this high-Mach number astrophysical regime. In this regime Cassini has provided the first in situ evidence for electron acceleration under quasi-parallel upstream magnetic conditions. Here we present the full picture of suprathermal electrons at Saturn's bow shock revealed by Cassini . The downstream thermal electron distribution is resolved in all data taken by the low-energy electron detector (CAPS-ELS, <28 keV) during shock crossings, but the higher energy channels were at (or close to) background. The high-energy electron detector (MIMI-LEMMS, >18 keV) measured a suprathermal electron signature at 31 of 508 crossings, where typically only the lowest energy channels (<100 keV) were above background. We show that these results are consistent with the theory in which the “injection” of thermal electrons into an acceleration process involves interaction with whistler waves at the shock front, and becomes possible for all upstream magnetic field orientations at high Mach numbers like those of the strong shocks around young SNRs. A future dedicated study will analyze the rare crossings with evidence for relativistic electrons (up to ∼1 MeV).

SUPRATHERMAL ELECTRONS AT SATURN'S BOW SHOCK

Energy Technology Data Exchange (ETDEWEB)

Masters, A.; Dougherty, M. K. [The Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom); Sulaiman, A. H. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Sergis, N. [Office of Space Research and Technology, Academy of Athens, Soranou Efesiou 4, 11527 Athens (Greece); Stawarz, L. [Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Krakow (Poland); Fujimoto, M. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Coates, A. J., E-mail: a.masters@imperial.ac.uk [Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking RH5 6NT (United Kingdom)

2016-07-20

The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach number) than these SNR shocks. However, the Cassini spacecraft has shown that the shock standing in the solar wind sunward of Saturn (Saturn's bow shock) can occasionally reach this high-Mach number astrophysical regime. In this regime Cassini has provided the first in situ evidence for electron acceleration under quasi-parallel upstream magnetic conditions. Here we present the full picture of suprathermal electrons at Saturn's bow shock revealed by Cassini . The downstream thermal electron distribution is resolved in all data taken by the low-energy electron detector (CAPS-ELS, <28 keV) during shock crossings, but the higher energy channels were at (or close to) background. The high-energy electron detector (MIMI-LEMMS, >18 keV) measured a suprathermal electron signature at 31 of 508 crossings, where typically only the lowest energy channels (<100 keV) were above background. We show that these results are consistent with the theory in which the “injection” of thermal electrons into an acceleration process involves interaction with whistler waves at the shock front, and becomes possible for all upstream magnetic field orientations at high Mach numbers like those of the strong shocks around young SNRs. A future dedicated study will analyze the rare crossings with evidence for relativistic electrons (up to ∼1 MeV).

5-D simulation study of suprathermal electron transport in non-axisymmetric plasmas

International Nuclear Information System (INIS)

Murakami, S.; Idei, H.; Kubo, S.; Nakajima, N.; Okamoto, M.; Gasparino, U.; Maassberg, H.; Rome, M.; Marushchenko, N.

2000-01-01

ECRH driven transport of suprathermal electrons is studied in non-axisymmetric plasmas using a new Monte Carlo simulation technique in 5-D phase space. Two different phases of the ECRH driven transport of suprathermal electrons can be seen. The first is a rapid convective phase due to the direct radial motion of trapped electrons and the second is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile in W7-AS is clarified. The ECRH driven flux is also evaluated and considered in relation to the 'electron root' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity, and thus the observed electron root feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. A possible scenario for this type of electron root is considered for the LHD plasma. (author)

5D simulation study of suprathermal electron transport in non-axisymmetric plasmas

International Nuclear Information System (INIS)

Murakami, S.; Idei, H.; Kubo, S.; Nakajima, N.; Okamoto, M.; Gasparino, U.; Maassberg, H.; Rome, M.; Marushchenko, N.

1999-01-01

ECRH-driven transport of suprathermal electrons is studied in non-axisymmetric plasmas using a new Monte Carlo simulation technique in 5D phase space. Two different phases of the ECRH-driven transport of suprathermal electrons can be seen; one is a rapid convective phase due to the direct radial motion of trapped electrons and the other is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile is clarified in W7-AS. The ECRH driven flux is also evaluated and put in relation with the 'electron root' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity and, thus, the observed 'electron root' feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. The possible scenario of this 'ECRH-driven electron root' is considered in the LHD plasma. (author)

On the propagation of hydromagnetic waves in a plasma of thermal and suprathermal components

Science.gov (United States)

Kumar, Nagendra; Sikka, Himanshu

2007-12-01

The propagation of MHD waves is studied when two ideal fluids, thermal and suprathermal gases, coupled by magnetic field are moving with the steady flow velocity. The fluids move independently in a direction perpendicular to the magnetic field but gets coupled along the field. Due to the presence of flow in suprathermal and thermal fluids there appears forward and backward waves. All the forward and backward modes propagate in such a way that their rate of change of phase speed with the thermal Mach number is same. It is also found that besides the usual hydromagnetic modes there appears a suprathermal mode which propagates with faster speed. Surface waves are also examined on an interface formed with composite plasma (suprathermal and thermal gases) on one side and the other is a non-magnetized plasma. In this case, the modes obtained are two or three depending on whether the sound velocity in thermal gas is equal to or greater than the sound velocity in suprathermal gas. The results lead to the conclusion that the interaction of thermal and suprathermal components may lead to the occurrence of an additional mode called suprathermal mode whose phase velocity is higher than all the other modes.

Electron cyclotron heating and supra-thermal electron dynamics in the TCV Tokamak

Energy Technology Data Exchange (ETDEWEB)

Gnesin, S.

2011-10-15

This thesis is concerned with the physics of supra-thermal electrons in thermonuclear, magnetically confined plasmas. Under a variety of conditions, in laboratory as well as space plasmas, the electron velocity distribution function is not in thermodynamic equilibrium owing to internal or external drives. Accordingly, the distribution function departs from the equilibrium Maxwellian, and in particular generally develops a high-energy tail. In tokamak plasmas, this occurs especially as a result of injection of high-power electromagnetic waves, used for heating and current drive, as well as a result of internal magnetohydrodynamic (MHD) instabilities. The physics of these phenomena is intimately tied to the properties and dynamics of this supra-thermal electron population. This motivates the development of instrumental apparatus to measure its properties as well as of numerical codes to simulate their dynamics. Both aspects are reflected in this thesis work, which features advanced instrumental development and experimental measurements as well as numerical modeling. The instrumental development consisted of the complete design of a spectroscopic and tomographic system of four multi-detector hard X-ray (HXR) cameras for the TCV tokamak. The goal is to measure bremsstrahlung emission from supra-thermal electrons with energies in the 10-300 keV range, with the ultimate aim of providing the first full tomographic reconstruction at these energies in a noncircular plasma. In particular, supra-thermal electrons are generated in TCV by a high-power electron cyclotron heating (ECH) system and are also observed in the presence of MHD events, such as sawtooth oscillations and disruptive instabilities. This diagnostic employs state-of-the-art solid-state detectors and is optimized for the tight space requirements of the TCV ports. It features a novel collimator concept that combines compactness and flexibility as well as full digital acquisition of the photon pulses, greatly

Electron cyclotron heating and supra-thermal electron dynamics in the TCV Tokamak

International Nuclear Information System (INIS)

Gnesin, S.

2011-10-01

This thesis is concerned with the physics of supra-thermal electrons in thermonuclear, magnetically confined plasmas. Under a variety of conditions, in laboratory as well as space plasmas, the electron velocity distribution function is not in thermodynamic equilibrium owing to internal or external drives. Accordingly, the distribution function departs from the equilibrium Maxwellian, and in particular generally develops a high-energy tail. In tokamak plasmas, this occurs especially as a result of injection of high-power electromagnetic waves, used for heating and current drive, as well as a result of internal magnetohydrodynamic (MHD) instabilities. The physics of these phenomena is intimately tied to the properties and dynamics of this supra-thermal electron population. This motivates the development of instrumental apparatus to measure its properties as well as of numerical codes to simulate their dynamics. Both aspects are reflected in this thesis work, which features advanced instrumental development and experimental measurements as well as numerical modeling. The instrumental development consisted of the complete design of a spectroscopic and tomographic system of four multi-detector hard X-ray (HXR) cameras for the TCV tokamak. The goal is to measure bremsstrahlung emission from supra-thermal electrons with energies in the 10-300 keV range, with the ultimate aim of providing the first full tomographic reconstruction at these energies in a noncircular plasma. In particular, supra-thermal electrons are generated in TCV by a high-power electron cyclotron heating (ECH) system and are also observed in the presence of MHD events, such as sawtooth oscillations and disruptive instabilities. This diagnostic employs state-of-the-art solid-state detectors and is optimized for the tight space requirements of the TCV ports. It features a novel collimator concept that combines compactness and flexibility as well as full digital acquisition of the photon pulses, greatly

MAVEN SupraThermal and Thermal Ion Compostion (STATIC) Instrument

Science.gov (United States)

McFadden, J. P.; Kortmann, O.; Curtis, D.; Dalton, G.; Johnson, G.; Abiad, R.; Sterling, R.; Hatch, K.; Berg, P.; Tiu, C.; Gordon, D.; Heavner, S.; Robinson, M.; Marckwordt, M.; Lin, R.; Jakosky, B.

2015-12-01

The MAVEN SupraThermal And Thermal Ion Compostion (STATIC) instrument is designed to measure the ion composition and distribution function of the cold Martian ionosphere, the heated suprathermal tail of this plasma in the upper ionosphere, and the pickup ions accelerated by solar wind electric fields. STATIC operates over an energy range of 0.1 eV up to 30 keV, with a base time resolution of 4 seconds. The instrument consists of a toroidal "top hat" electrostatic analyzer with a 360° × 90° field-of-view, combined with a time-of-flight (TOF) velocity analyzer with 22.5° resolution in the detection plane. The TOF combines a -15 kV acceleration voltage with ultra-thin carbon foils to resolve H+, He^{++}, He+, O+, O2+, and CO2+ ions. Secondary electrons from carbon foils are detected by microchannel plate detectors and binned into a variety of data products with varying energy, mass, angle, and time resolution. To prevent detector saturation when measuring cold ram ions at periapsis (˜10^{1 1} eV/cm2 s sr eV), while maintaining adequate sensitivity to resolve tenuous pickup ions at apoapsis (˜103 eV/cm2 s sr eV), the sensor includes both mechanical and electrostatic attenuators that increase the dynamic range by a factor of 103. This paper describes the instrument hardware, including several innovative improvements over previous TOF sensors, the ground calibrations of the sensor, the data products generated by the experiment, and some early measurements during cruise phase to Mars.

5D simulation study of suprathermal electron transport in non-axisymmetric plasmas

International Nuclear Information System (INIS)

Murakami, S.; Idei, H.; Kubo, S.; Nakajima, N.; Okamoto, M.; Gasparino, U.; Maassberg, H.; Rome, M.; Marushchenko, N.

2001-01-01

ECRH-driven transport of is studied in using a new Monte Carlo simulation technique in 5D phase space. Two different phases of the ECRH-driven transport of suprathermal electrons can be seen; one is a rapid convective phase due to the direct radial motion of trapped electrons and the other is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile is clarified in W7-AS. The ECRH driven flux is also evaluated and put in relation with the ''electron root'' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity and, thus, the observed ''electron root'' feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. The possible scenario of this ''ECRH-driven electron root'' is considered in the LHD plasma. (author)

New Measurements of Suprathermal Ions, Energetic Particles, and Cosmic Rays in the Outer Heliosphere from the New Horizons PEPSSI Instrument

Science.gov (United States)

Hill, M. E.; Kollmann, P.; McNutt, R. L., Jr.; Stern, A.; Weaver, H. A., Jr.; Young, L. A.; Olkin, C.; Spencer, J. R.

2017-12-01

During the period from January 2012 to December 2017 the New Horizons spacecraft traveled from 22 to 41 AU from the Sun, making nearly continuous interplanetary plasma and particle measurements utilizing the SWAP and PEPSSI instruments. We report on newly extended measurements from PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation) that now bring together suprathermal particles above 2 keV/nuc (including interstellar pickup ions), energetic particles with H, He, and O composition from 30 keV to 1 MeV, and cosmic rays above 65 MeV (with effective count-rate-limited upper energy of 1 GeV). Such a wide energy range allows us to look at the solar wind structures passing over the spacecraft, the energetic particles that are often accelerated by these structures, and the suppression of cosmic rays resulting from the increased turbulence inhibiting cosmic ray transport to the spacecraft position (i.e., Forbush decreases). This broad perspective provides simultaneous, previously unattainable diagnostics of outer heliospheric particle dynamics and acceleration. Besides the benefit of being recent, in-ecliptic measurements, unlike the historic Voyager 1 and 2 spacecraft, these PEPSSI observations are also totally unique in the suprathermal range; in this region only PEPSSI can span the suprathermal range, detecting a population that is a linchpin to understanding the outer heliosphere.

Opacity broadening and interpretation of suprathermal CO linewidths: Macroscopic turbulence and tangled molecular clouds

Science.gov (United States)

Hacar, A.; Alves, J.; Burkert, A.; Goldsmith, P.

2016-06-01

Context. Since their first detection in the interestellar medium, (sub-)millimeter line observations of different CO isotopic variants have routinely been employed to characterize the kinematic properties of the gas in molecular clouds. Many of these lines exhibit broad linewidths that greatly exceed the thermal broadening expected for the low temperatures found within these objects. These observed suprathermal CO linewidths are assumed to originate from unresolved supersonic motions inside clouds. Aims: The lowest rotational J transitions of some of the most abundant CO isotopologues, 12CO and 13CO, are found to present large optical depths. In addition to well-known line saturation effects, these large opacities present a non-negligible contribution to their observed linewidths. Typically overlooked in the literature, in this paper we aim to quantify the impact of these opacity broadening effects on the current interpretation of the CO suprathermal line profiles. Methods: Combining large-scale observations and LTE modeling of the ground J = 1-0 transitions of the main 12CO, 13CO, C18O isotopologues, we have investigated the correlation of the observed linewidths as a function of the line opacity in different regions of the Taurus molecular cloud. Results: Without any additional contributions to the gas velocity field, a large fraction of the apparently supersonic (ℳ ~ 2-3) linewidths measured in both 12CO and 13CO (J = 1-0) lines can be explained by the saturation of their corresponding sonic-like, optically thin C18O counterparts assuming standard isotopic fractionation. Combined with the presence of multiple components detected in some of our C18O spectra, these opacity effects also seem to be responsible for most of the highly supersonic linewidths (ℳ > 8-10) detected in some of the broadest 12CO and 13CO spectra in Taurus. Conclusions: Our results demonstrate that most of the suprathermal 12CO and 13CO linewidths reported in nearby clouds like Taurus

Quiet-time Suprathermal (~0.1-1.5 keV) Electrons in the Solar Wind

Science.gov (United States)

Tao, Jiawei; Wang, Linghua; Zong, Qiugang; Li, Gang; Salem, Chadi S.; Wimmer-Schweingruber, Robert F.; He, Jiansen; Tu, Chuanyi; Bale, Stuart D.

2016-03-01

We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ˜0.1-1.5 keV to a Kappa distribution function with an index κ and effective temperature Teff. We also calculate the number density n and average energy Eavg of strahl and halo electrons by integrating the electron measurements between ˜0.1 and 1.5 keV. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity).

Electron energy-loss spectra in molecular fluorine

Science.gov (United States)

Nishimura, H.; Cartwright, D. C.; Trajmar, S.

1979-01-01

Electron energy-loss spectra in molecular fluorine, for energy losses from 0 to 17.0 eV, have been taken at incident electron energies of 30, 50, and 90 eV and scattering angles from 5 to 140 deg. Features in the spectra above 11.5 eV energy loss agree well with the assignments recently made from optical spectroscopy. Excitations of many of the eleven repulsive valence excited electronic states are observed and their location correlates reasonably well with recent theoretical results. Several of these excitations have been observed for the first time and four features, for which there are no identifications, appear in the spectra.

Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability

Directory of Open Access Journals (Sweden)

C. Krafft

Full Text Available Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field, the fan instability can excite VLF waves (whistlers and lower hybrid waves with characteristics close to those observed in space experiments.

Key words. Space plasma physics (waves and instabilities – Radio Science (waves in plasma – Solar physics, astrophysics and astronomy (radio emissions

Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability

Directory of Open Access Journals (Sweden)

C. Krafft

2003-07-01

Full Text Available Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field, the fan instability can excite VLF waves (whistlers and lower hybrid waves with characteristics close to those observed in space experiments.Key words. Space plasma physics (waves and instabilities – Radio Science (waves in plasma – Solar physics, astrophysics and astronomy (radio emissions

Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines

Directory of Open Access Journals (Sweden)

P. Guio

Full Text Available In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV of the total electron population can excite or damp these Langmuir waves above the thermal equilibrium, resulting in an enhancement of the intensity of the lines above the thermal level. The presence of photo-electrons also modifies the dielectric response function of the plasma from the Maxwellian and thus influences the Doppler frequency of the plasma lines. In this paper, we present a high time-resolution plasma-line data set collected on the Eiscat VHF radar. The analysed data are compared with a model that includes the effect of a suprathermal electron population calculated by a transport code. By comparing the intensity of the analysed plasma lines data to our model, we show that two sharp peaks in the electron suprathermal distribution in the energy range 20-30 eV causes an increased Landau damping around 24.25 eV and 26.25 eV. We have identified these two sharp peaks as the effect of the photoionisation of N₂ and O by the intense flux of monochromatic HeII radiation of wavelength 30.378 nm (40.812 eV created in the chromospheric network and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift velocity for a Maxwellian plasma is actually a shift of the Doppler frequency of the plasma lines due to suprathermal electrons.

Key words. Ionosphere (electric fields and currents; solar radiation and cosmic ray effects

Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines

Directory of Open Access Journals (Sweden)

P. Guio

1999-07-01

Full Text Available In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV of the total electron population can excite or damp these Langmuir waves above the thermal equilibrium, resulting in an enhancement of the intensity of the lines above the thermal level. The presence of photo-electrons also modifies the dielectric response function of the plasma from the Maxwellian and thus influences the Doppler frequency of the plasma lines. In this paper, we present a high time-resolution plasma-line data set collected on the Eiscat VHF radar. The analysed data are compared with a model that includes the effect of a suprathermal electron population calculated by a transport code. By comparing the intensity of the analysed plasma lines data to our model, we show that two sharp peaks in the electron suprathermal distribution in the energy range 20-30 eV causes an increased Landau damping around 24.25 eV and 26.25 eV. We have identified these two sharp peaks as the effect of the photoionisation of N2 and O by the intense flux of monochromatic HeII radiation of wavelength 30.378 nm (40.812 eV created in the chromospheric network and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift velocity for a Maxwellian plasma is actually a shift of the Doppler frequency of the plasma lines due to suprathermal electrons.Key words. Ionosphere (electric fields and currents; solar radiation and cosmic ray effects

Design energy spectra for Turkey

OpenAIRE

López Almansa, Francisco; Yazgan, Ahmet Utku; Benavent Climent, Amadeo

2012-01-01

This work proposes design energy spectra in terms of velocity, derived through linear dynamic analyses on Turkish registers and intended for regions with design peak acceleration 0.3 g or higher. In the long and mid period ranges the analyses are linear, taking profit of the rather insensitivity of the spectra to the structural parameters other than the fundamental period; in the short period range, the spectra are more sensitive to the structural parameters and nonlinear analyses would be re...

Effect of ion suprathermality on arbitrary amplitude dust acoustic waves in a charge varying dusty plasma

International Nuclear Information System (INIS)

Tribeche, Mouloud; Mayout, Saliha; Amour, Rabia

2009-01-01

Arbitrary amplitude dust acoustic waves in a high energy-tail ion distribution are investigated. The effects of charge variation and ion suprathermality on the large amplitude dust acoustic (DA) soliton are then considered. The correct suprathermal ion charging current is rederived based on the orbit motion limited approach. In the adiabatic case, the variable dust charge is expressed in terms of the Lambert function and we take advantage of this transcendental function to show the existence of rarefactive variable charge DA solitons involving cusped density humps. The dust charge variation leads to an additional enlargement of the DA soliton, which is less pronounced as the ions evolve far away from Maxwell-Boltzmann distribution. In the nonadiabatic case, the dust charge fluctuation may provide an alternate physical mechanism causing anomalous dissipation the strength of which becomes important and may prevail over that of dispersion as the ion spectral index κ increases. Our results may provide an explanation for the strong spiky waveforms observed in auroral electric field measurements by Ergun et al.[Geophys. Res. Lett. 25, 2025 (1998)].

Suprathermal electron studies in the TCV tokamak: Design of a tomographic hard-x-ray spectrometer

International Nuclear Information System (INIS)

Gnesin, S.; Coda, S.; Decker, J.; Peysson, Y.

2008-01-01

Electron cyclotron resonance heating and electron cyclotron current drive, disruptive events, and sawtooth activity are all known to produce suprathermal electrons in fusion devices, motivating increasingly detailed studies of the generation and dynamics of this suprathermal population. Measurements have been performed in the past years in the tokamak a configuration variable (TCV) tokamak using a single pinhole hard-x-ray (HXR) camera and electron-cyclotron-emission radiometers, leading, in particular, to the identification of the crucial role of spatial transport in the physics of ECCD. The observation of a poloidal asymmetry in the emitted suprathermal bremsstrahlung radiation motivates the design of a proposed new tomographic HXR spectrometer reported in this paper. The design, which is based on a compact modified Soller collimator concept, is being aided by simulations of tomographic reconstruction. Quantitative criteria have been developed to optimize the design for the greatly variable shapes and positions of TCV plasmas.

Revealing low-energy part of the beta spectra

International Nuclear Information System (INIS)

Selvi, S.; Celiktas, C.

2002-01-01

An effective method is proposed to separate electronic noise from the beta-particle spectra revealing lower energy part of the spectra. The available methods for reducing the noise problem cut the noise along with the low-energy part of the beta spectra by using a discriminator. Our setup eliminates this undesirable effect by shifting the noise toward the lowest energy scale leaving the low-energy part of spectra undisturbed. We achieved this noise-pulse-separation by treating the noise as a pulse so that we can exploit the application of the pulse-shape analyzer equipment used for pulse shape identification of particles and rejection of defective pulses. To the best of our knowledge this method of the noise separation is a novel approach

Suprathermal electron loss cone distributions in the solar wind: Ulysses observations

International Nuclear Information System (INIS)

Phillips, J. L.; Feldman, W. C.; Gosling, J. T.; Hammond, C. M.; Forsyth, R. J.

1996-01-01

We present observations by the Ulysses solar wind plasma experiment of a new class of suprathermal electron signatures. At low solar latitudes and heliocentric distances beyond 3.37 AU Ulysses encountered seven intervals, ranging in duration from 1 hour to 22 hours, in which the suprathermal distributions included an antisunward field-aligned beam and a return population with a flux dropout typically spanning ±60 deg. from the sunward field-aligned direction. All events occurred between the forward and reverse shocks or waves bounding corotating interaction regions (CIRs). The observations support a scenario in which the sunward-moving electrons result from reflection of the prevailing antisunward field-aligned beam at magnetic field compressions downstream from the spacecraft, with wide loss cones caused by the relatively weak mirror ratio. This hypothesis requires that the field magnitude within the CIRs actually increased locally with increasing field-aligned distance from the Sun

Program package for processing energy spectra of gamma radiation

International Nuclear Information System (INIS)

Stejskalova, E.

1985-01-01

A library of programs for processing energy spectra of nuclear radiation using an ICL 4-72 computer is described. The library is available at the computer centre of the Prague universities and bears the acronym JADSPE. The programs perform the computation of positions, areas and half-widths of lines in the energy spectrum of the radiation, they give a graphic representation of the course of energy spectra on the printer and on the CALCOMP recorder; they also perform the addition or subtraction of energy spectra with possible aligning of the beginnings or ends of the spectra or of maximums of chosen lines. A model function in the form of a symmetric Gaussian function is used for the computation of parameters of spectral lines, and the variation of the background with energy is assumed to be linear. (author)

Electron beam-plasma interaction and electron-acoustic solitary waves in a plasma with suprathermal electrons

Science.gov (United States)

Danehkar, A.

2018-06-01

Suprathermal electrons and inertial drifting electrons, so called electron beam, are crucial to the nonlinear dynamics of electrostatic solitary waves observed in several astrophysical plasmas. In this paper, the propagation of electron-acoustic solitary waves (EAWs) is investigated in a collisionless, unmagnetized plasma consisting of cool inertial background electrons, hot suprathermal electrons (modeled by a κ-type distribution), and stationary ions. The plasma is penetrated by a cool electron beam component. A linear dispersion relation is derived to describe small-amplitude wave structures that shows a weak dependence of the phase speed on the electron beam velocity and density. A (Sagdeev-type) pseudopotential approach is employed to obtain the existence domain of large-amplitude solitary waves, and investigate how their nonlinear structures depend on the kinematic and physical properties of the electron beam and the suprathermality (described by κ) of the hot electrons. The results indicate that the electron beam can largely alter the EAWs, but can only produce negative polarity solitary waves in this model. While the electron beam co-propagates with the solitary waves, the soliton existence domain (Mach number range) becomes narrower (nearly down to nil) with increasing the beam speed and the beam-to-hot electron temperature ratio, and decreasing the beam-to-cool electron density ratio in high suprathermality (low κ). It is found that the electric potential amplitude largely declines with increasing the beam speed and the beam-to-cool electron density ratio for co-propagating solitary waves, but is slightly decreased by raising the beam-to-hot electron temperature ratio.

Microwave heating and diagnostic of suprathermal electrons in an overdense stellarator plasma

International Nuclear Information System (INIS)

Stange, Torsten

2014-01-01

The resonant coupling of microwaves into a magnetically confined plasma is one of the fundamental methods for the heating of such plasmas. Identifying and understanding the processes of the heating of overdense plasmas, in which the wave propagation is generally not possible because the wave frequency is below the plasma frequency, is becoming increasingly important for high density fusion plasmas. This work focuses on the heating of overdense plasmas in the WEGA stellarator. The excitation of electron Bernstein waves, utilizing the OXB-conversion process, provides a mechanism for the wave to reach the otherwise not accessible resonant absorption layer. In WEGA these OXB-heated plasmas exhibit a suprathermal electron component with energies up to 80 keV. The fast electrons are located in the plasma center and have a Maxwellian energy distribution function within the soft X-ray related energy range. The corresponding averaged energy is a few keV. The OXB-discharges are accompanied by a broadband microwave radiation spectrum with radiation temperatures of the order of keV. Its source was identified as a parametric decay of the heating wave and has no connection to the suprathermal electron component. For the detailed investigation of the microwave emission, a quasioptical mirror system, optimized for the OX-conversion, has been installed. Based on the measurement of the broadband microwave stray radiation of the decay process, the OX-conversion efficiency has been determined to 0.56 being in good agreement with full-wave calculations. In plasmas without an electron cyclotron resonance, corresponding to the wave frequency used, non-resonant heating mechanisms have been identified in the overdense plasma regions. Whistler waves or R-like waves are the only propagable wave types within the overdense plasmas. The analysis of the heating efficiency in dependence on the magnetic flux density leads to tunneling as the most probable coupling mechanism. For the determination

QUIET-TIME SUPRATHERMAL (∼0.1–1.5 keV) ELECTRONS IN THE SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Tao, Jiawei; Wang, Linghua; Zong, Qiugang; He, Jiansen; Tu, Chuanyi [School of Earth and Space Science, Peking University, Beijing 100871 (China); Li, Gang [Department of Physics and CSPAR, University of Alabama in Huntsville, Alabama 35899 (United States); Salem, Chadi S.; Bale, Stuart D. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Wimmer-Schweingruber, Robert F., E-mail: wanglhwang@gmail.com [Institute for Experimental and Applied Physics, University of Kiel, Leibnizstrasse 11, D-24118 Kiel (Germany)

2016-03-20

We present a statistical survey of the energy spectrum of solar wind suprathermal (∼0.1–1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ∼0.1–1.5 keV to a Kappa distribution function with an index κ and effective temperature T{sub eff}. We also calculate the number density n and average energy E{sub avg} of strahl and halo electrons by integrating the electron measurements between ∼0.1 and 1.5 keV. We find a strong positive correlation between κ and T{sub eff} for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity)

Study on Properties of Energy Spectra of the Molecular Crystals

Science.gov (United States)

Pang, Xiao-Feng; Chen, Xiang-Rong

The energy-spectra of nonlinear vibration of molecular crystals such as acetanilide have been calculated by using discrete nonlinear Schrödinger equation appropriate to the systems, containing various interactions. The energy levels including higher excited states are basically consistent with experimental values obtained by infrared absorption and Raman scattering in acetanilide. We further give the features of distribution of the energy-spectra for the acetanilide. Using the energy spectra we also explained well experimental results obtained by Careri et al..

Beta-energy averaging and beta spectra

International Nuclear Information System (INIS)

Stamatelatos, M.G.; England, T.R.

1976-07-01

A simple yet highly accurate method for approximately calculating spectrum-averaged beta energies and beta spectra for radioactive nuclei is presented. This method should prove useful for users who wish to obtain accurate answers without complicated calculations of Fermi functions, complex gamma functions, and time-consuming numerical integrations as required by the more exact theoretical expressions. Therefore, this method should be a good time-saving alternative for investigators who need to make calculations involving large numbers of nuclei (e.g., fission products) as well as for occasional users interested in restricted number of nuclides. The average beta-energy values calculated by this method differ from those calculated by ''exact'' methods by no more than 1 percent for nuclides with atomic numbers in the 20 to 100 range and which emit betas of energies up to approximately 8 MeV. These include all fission products and the actinides. The beta-energy spectra calculated by the present method are also of the same quality

SUPRATHERMAL ELECTRONS IN THE SOLAR CORONA: CAN NONLOCAL TRANSPORT EXPLAIN HELIOSPHERIC CHARGE STATES?

International Nuclear Information System (INIS)

Cranmer, Steven R.

2014-01-01

There have been several ideas proposed to explain how the Sun's corona is heated and how the solar wind is accelerated. Some models assume that open magnetic field lines are heated by Alfvén waves driven by photospheric motions and dissipated after undergoing a turbulent cascade. Other models posit that much of the solar wind's mass and energy is injected via magnetic reconnection from closed coronal loops. The latter idea is motivated by observations of reconnecting jets and also by similarities of ion composition between closed loops and the slow wind. Wave/turbulence models have also succeeded in reproducing observed trends in ion composition signatures versus wind speed. However, the absolute values of the charge-state ratios predicted by those models tended to be too low in comparison with observations. This Letter refines these predictions by taking better account of weak Coulomb collisions for coronal electrons, whose thermodynamic properties determine the ion charge states in the low corona. A perturbative description of nonlocal electron transport is applied to an existing set of wave/turbulence models. The resulting electron velocity distributions in the low corona exhibit mild suprathermal tails characterized by ''kappa'' exponents between 10 and 25. These suprathermal electrons are found to be sufficiently energetic to enhance the charge states of oxygen ions, while maintaining the same relative trend with wind speed that was found when the distribution was assumed to be Maxwellian. The updated wave/turbulence models are in excellent agreement with solar wind ion composition measurements

Cluster observations of particle acceleration up to supra-thermal energies in the cusp region related to low-frequency wave activity – possible implications for the substorm initiation process

Directory of Open Access Journals (Sweden)

T. A. Fritz

2008-03-01

Full Text Available The purpose of our study is to investigate the way particles are accelerated up to supra-thermal energies in the cusp diamagnetic cavities. For this reason we have examined a number of Cluster cusp crossings, originally identified by Zhang et al. (2005, for the years 2001 and 2002 using data from RAPID, STAFF, EFW, CIS, PEACE, and FGM experiments. In the present study we focus on two particular cusp crossings on 25 March 2002 and on 10 April 2002 which demonstrate in a clear way the general characteristics of the events in our survey. Both events exhibit very sharp spatial boundaries seen both in CNO (primarily single-charged oxygen of ionospheric origin based on CIS observations and H+ flux increases within the RAPID energy range with the magnetic field intensity being anti-correlated. Unlike the first event, the second one shows also a moderate electron flux increase. The fact that the duskward electric field Ey has relatively low values <5 mV/m while the local wave activity is very intense provides a strong indication that particle energization is caused primarily by wave-particle interactions. The wave power spectra and propagation parameters during these cusp events are examined in detail. It is concluded that the high ion fluxes and at the same time the presence or absence of any sign of energization in the electrons clearly shows that the particle acceleration depends on the wave power near the local particle gyrofrequency and on the persistence of the wave-particle interaction process before particles escape from cusp region. Furthermore, the continuous existence of energetic O+ ions suggests that energetic O+ populations are of spatial nature at least for the eight events that we have studied so far.

Aircraft Measurements of Atmospheric Kinetic Energy Spectra

DEFF Research Database (Denmark)

Lundtang Petersen, Erik; Lilly, D. K.

1983-01-01

Wind velocity data obtained from a jet airliner are used to construct kinetic energy spectra over the range of wavelengths from 2.5 to 2500 km. The spectra exhibit an approximate -5/3 slope for wavelengths of less than about 150 km, steepening to about -2.2 at larger scales. These results support...

Origin and Properties of Quiet-time 0.11–1.28 MeV Nucleon{sup −1} Heavy-ion Population Near 1 au

Energy Technology Data Exchange (ETDEWEB)

Dayeh, M. A.; Desai, M. I.; Ebert, R. W. [Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX 78238 (United States); Mason, G. M. [Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723 (United States); Farahat, A., E-mail: maldayeh@swri.edu [Department of Physics, College of Applied and Supporting Studies, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

2017-02-01

Using measurements from the Advanced Composition Explorer /Ultra-Low Energy Isotope Spectrometer near 1 au, we surveyed the composition and spectra of heavy ions (He-through-Fe) during quiet times from 1998 January 1 to 2015 December 31 at suprathermal energies between ∼0.11 and ∼1.28 MeV nucleon{sup −1}. The selected time period covers the maxima of solar cycles 23 and 24 and the extended solar minimum in between. We find the following. (1) The number of quiet hours in each year correlates well with the sunspot number, year 2009 was the quietest for about 82% of the time. (2) The composition of the quiet-time suprathermal heavy-ion population ({sup 3}He, C-through-Fe) correlates well with the level of solar activity, exhibiting SEP-like composition signatures during solar maximum, and CIR- or solar wind-like composition during solar minimum. (3) The heavy-ion (C–Fe) spectra exhibit suprathermal tails at energies of 0.11–0.32 MeV nucleon{sup −1} with power-law spectral indices ranging from 1.40 to 2.97. Fe spectra soften (steepen, i.e., spectral index increases) smoothly with increasing energies compared with Fe, indicating a rollover behavior of Fe at higher energies (0.45–1.28 MeV nucleon{sup −1}). (4) Spectral indices of Fe and O do not appear to exhibit clear solar cycle dependence. (2) and (3) imply that during IP quiet times and at energies above ∼0.1 MeV nucleon{sup −1}, the IP medium is dominated by material from prior solar and interplanetary events. We discuss the implications of these extended observations in the context of the current understanding of the suprathermal ion population near 1 au.

Effect of suprathermal electrons on the impurity ionization state

International Nuclear Information System (INIS)

Ochando, M A; Medina, F; Zurro, B; McCarthy, K J; Pedrosa, M A; Baciero, A; Rapisarda, D; Carmona, J M; Jimenez, D

2006-01-01

The effect of electron cyclotron resonance heating induced suprathermal electron tails on the ionization of iron impurities in magnetically confined plasmas is investigated. The behaviour of plasma emissivity immediately after injection provides evidence of a spatially localized 'shift' towards higher charge states of the impurity. Bearing in mind that the non-inductive plasma heating methods generate long lasting non-Maxwellian distribution functions, possible implications on the deduced impurity transport coefficients, when fast electrons are present, are discussed

Properties of Energy Spectra of Molecular Crystals Investigated by Nonlinear Theory

Science.gov (United States)

Pang, Xiao-Feng; Zhang, Huai-Wu

We calculate the quantum energy spectra of molecular crystals, such as acetanilide, by using discrete nonlinear Schrodinger equation, containing various interactions, appropriate to the systems. The energy spectra consist of many energy bands, in each energy band there are a lot of energy levels including some higher excited states. The result of energy spectrum is basically consistent with experimental values obtained by infrared absorption and Raman scattering in acetanilide and can also explain some experimental results obtained by Careri et al. Finally, we further discuss the influences of variously characteristic parameters on the energy spectra of the systems.

Effects of peripheral physical phenomena on ECE spectra

International Nuclear Information System (INIS)

Airoldi, A.; Ramponi, G.

1993-01-01

In large fusion Tokamaks the measurement of the Electron Cyclotron Emission (ECE) from the low field side, perpendicularly viewing chord, is by now a standard way of obtaining the radial electron temperature profile. In high temperature plasmas the condition of large optical thickness for the second harmonic X-mode may be easily satisfied even for frequencies corresponding to the edge plasma region, allowing the temperature profile to be inferred. Recent experimental observations of enhanced emission at frequencies associated with the extreme edge of the profile in H-mode JET plasmas have been interpreted as the effect of a small fraction of suprathermal electrons. It is well known that the ECE spectra are very sensitive to the presence of non-thermal electron components, thus it is important to interpret the ECE signals as an indication of the possible deviation of the electron distribution function from a 'pure' Maxwellian and to discern under which conditions they are a good measure of the plasma thermal energy. (author) 3 refs., 6 figs

Study of the thermal and suprathermal electron density fluctuations of the plasma in the Focus experiment

International Nuclear Information System (INIS)

Jolas, A.

1981-10-01

An experiment on Thomson scattering of ruby laser light by the electrons of a plasma produced by an intense discharge between the electrodes of a coaxial gun in a gas at low pressure has been carried out. It is shown that the imploding plasma is made up of layers with different characteristics: a dense plasma layer where the density fluctuations are isotropic and have a thermal level, and a tenuous plasma layer where the fluctuations are anisotropic, and strongly suprathermal. The suprathermal fluctuations are attributed to microscopic instabilities generated by the electric current circulating in the transition zone where the magnetic field penetrates the plasma [fr

MAGNETIC ENERGY SPECTRA IN SOLAR ACTIVE REGIONS

International Nuclear Information System (INIS)

Abramenko, Valentyna; Yurchyshyn, Vasyl

2010-01-01

Line-of-sight magnetograms for 217 active regions (ARs) with different flare rates observed at the solar disk center from 1997 January until 2006 December are utilized to study the turbulence regime and its relationship to flare productivity. Data from the SOHO/MDI instrument recorded in the high-resolution mode and data from the BBSO magnetograph were used. The turbulence regime was probed via magnetic energy spectra and magnetic dissipation spectra. We found steeper energy spectra for ARs with higher flare productivity. We also report that both the power index, α, of the energy spectrum, E(k) ∼ k -α , and the total spectral energy, W = ∫E(k)dk, are comparably correlated with the flare index, A, of an AR. The correlations are found to be stronger than those found between the flare index and the total unsigned flux. The flare index for an AR can be estimated based on measurements of α and W as A = 10 b (αW) c , with b = -7.92 ± 0.58 and c = 1.85 ± 0.13. We found that the regime of the fully developed turbulence occurs in decaying ARs and in emerging ARs (at the very early stage of emergence). Well-developed ARs display underdeveloped turbulence with strong magnetic dissipation at all scales.

Energy spectra of hadrons and leptons in the atmosphere

International Nuclear Information System (INIS)

Butkevich, A.V.; Dedenko, L.G.; Zheleznykh, I.M.; Kiryushkin, V.P.; Sobolevskij, N.M.

1982-01-01

Differential energy spectra of hadrons were calculated in the energy range of 10 11 -10 15 eV in the Earth atmosphere at depths of 60, 260, 690 and 1000 gxcm -2 . The Nickolski spectrum has the best agreement with experiment at a depth of 60 gxcm -2 . At high depths the Grigorov spectrum is less intensive, and the Nickolski and Rayan spectra agree with experiment without errors. Calculations of low energy neutrino fluxes in the atmospehere are given. Total fluxes of muon and electron neutrinos at neutrino energies Esub(γ) -2 xs -1 , correspondingly

Suprathermal Electron Generation and Channel Formation by an Ultrarelativistic Laser Pulse in an Underdense Preformed Plasma

International Nuclear Information System (INIS)

Malka, G.; Gaillard, R.; Miquel, J.L.; Rousseaux, C.; Bonnaud, G.; Busquet, M.; Lours, L.; Fuchs, J.; Pepin, H.; Fuchs, J.; Amiranoff, F.; Baton, S.D.

1997-01-01

Relativistic electrons are produced, with energies up to 20MeV, by the interaction of a high-intensity subpicosecond laser pulse (1 μm , 300 fs , 10 19 W/cm 2 ) with an underdense plasma. Two suprathermal electron populations appear with temperatures of 1 and 3MeV. In the same conditions, the laser beam transmission is increased up to 20% 30%. We observe both features along with the evidence of laser pulse channeling. A fluid model predicts a strong self-focusing of the pulse. Acceleration in the enhanced laser field seems the most likely mechanism leading to the second electron population. copyright 1997 The American Physical Society

Suprathermal ions in the solar wind from the Voyager spacecraft: Instrument modeling and background analysis

International Nuclear Information System (INIS)

Randol, B M; Christian, E R

2015-01-01

Using publicly available data from the Voyager Low Energy Charged Particle (LECP) instruments, we investigate the form of the solar wind ion suprathermal tail in the outer heliosphere inside the termination shock. This tail has a commonly observed form in the inner heliosphere, that is, a power law with a particular spectral index. The Voyager spacecraft have taken data beyond 100 AU, farther than any other spacecraft. However, during extended periods of time, the data appears to be mostly background. We have developed a technique to self-consistently estimate the background seen by LECP due to cosmic rays using data from the Voyager cosmic ray instruments and a simple, semi-analytical model of the LECP instruments

ON THE REMOTE DETECTION OF SUPRATHERMAL IONS IN THE SOLAR CORONA AND THEIR ROLE AS SEEDS FOR SOLAR ENERGETIC PARTICLE PRODUCTION

Energy Technology Data Exchange (ETDEWEB)

Laming, J. Martin; Moses, J. Daniel; Ko, Yuan-Kuen [Space Science Division, Naval Research Laboratory, Code 7684, Washington, DC 20375 (United States); Ng, Chee K. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Rakowski, Cara E.; Tylka, Allan J. [NASA/GSFC Code 672, Greenbelt, MD 20771 (United States)

2013-06-10

Forecasting large solar energetic particle (SEP) events associated with shocks driven by fast coronal mass ejections (CMEs) poses a major difficulty in the field of space weather. Besides issues associated with CME initiation, the SEP intensities are difficult to predict, spanning three orders of magnitude at any given CME speed. Many lines of indirect evidence point to the pre-existence of suprathermal seed particles for injection into the acceleration process as a key ingredient limiting the SEP intensity of a given event. This paper outlines the observational and theoretical basis for the inference that a suprathermal particle population is present prior to large SEP events, explores various scenarios for generating seed particles and their observational signatures, and explains how such suprathermals could be detected through measuring the wings of the H I Ly{alpha} line.

ON THE REMOTE DETECTION OF SUPRATHERMAL IONS IN THE SOLAR CORONA AND THEIR ROLE AS SEEDS FOR SOLAR ENERGETIC PARTICLE PRODUCTION

International Nuclear Information System (INIS)

Laming, J. Martin; Moses, J. Daniel; Ko, Yuan-Kuen; Ng, Chee K.; Rakowski, Cara E.; Tylka, Allan J.

2013-01-01

Forecasting large solar energetic particle (SEP) events associated with shocks driven by fast coronal mass ejections (CMEs) poses a major difficulty in the field of space weather. Besides issues associated with CME initiation, the SEP intensities are difficult to predict, spanning three orders of magnitude at any given CME speed. Many lines of indirect evidence point to the pre-existence of suprathermal seed particles for injection into the acceleration process as a key ingredient limiting the SEP intensity of a given event. This paper outlines the observational and theoretical basis for the inference that a suprathermal particle population is present prior to large SEP events, explores various scenarios for generating seed particles and their observational signatures, and explains how such suprathermals could be detected through measuring the wings of the H I Lyα line.

A system to measure suprathermal electron distribution functions in toroidal plasmas by electron cyclotron wave absorption

International Nuclear Information System (INIS)

Boyd, D.A.; Skiff, F.; Gulick, S.

1997-01-01

A two-chord, four-beam suprathermal electron diagnostic has been installed on TdeV (B>1.5 T, R=0.86 m, a=0.25 m). Resonant absorption of extraordinary mode electron cyclotron waves is measured to deduce the chordal averaged suprathermal electron distribution function amplitude at the resonant momentum. Simultaneously counterpropagating beams permit good refractive loss cancellation. A nonlinear frequency sweep leads to a concentration of appropriately propagating power in a narrow range of time of flight, thus increasing the signal-to-noise ratio and facilitating the rejection of spurious reflections. Numerous measurements of electron distribution functions have been obtained during lower-hybrid current-drive experiments. copyright 1997 American Institute of Physics

Quasar energy distributions. I. Soft X-ray spectra of quasars

International Nuclear Information System (INIS)

Wilkes, B.J.; Elvis, M.

1987-01-01

As the initial stage of a study of quasar energy distributions (QEDs), Einstein IPC spectra of 24 quasars are presented. These are combined with previously reported IPC spectra to form a sample of 33 quasars with well-determined soft X-ray slopes. A correlation analysis shows that radio loudness, rather than redshift or luminosity, is fundamentally related to the X-ray slope. This correlation is not followed by higher energy spectra of active galaxies. Two components are required to explain both sets of results. The best-fit column densities are systematically smaller than the Galactic values. The same effect is not present in a sample of BL Lac objects, implying that the effect is intrinsic to the quasars and is caused by a low-energy turnup in the quasar spectra. 74 references

Shaping the solar wind electron temperature anisotropy by the interplay of core and suprathermal populations

Science.gov (United States)

Shaaban Hamd, S. M.; Lazar, M.; Poedts, S.; Pierrard, V.; Štverák

2017-12-01

We present the results of an advanced parametrization of the temperature anisotropy of electrons in the slow solar wind and the electromagnetic instabilities resulting from the interplay of their thermal core and suprathermal halo populations. A large set of observational data (from the Ulysses, Helios and Cluster missions) is used to parametrize these components and establish their correlations. Comparative analysis demonstrates for the first time a particular implication of the suprathermal electrons which are less dense but hotter than thermal electrons. The instabilities are significantly stimulated by the interplay of the core and halo populations, leading to lower thresholds which shape the observed limits of the temperature anisotropy for both the core and halo populations. This double agreement strongly suggests that the selfgenerated instabilities play the major role in constraining the electron anisotropy.

Nonlinear dust acoustic waves in a charge varying dusty plasma with suprathermal electrons

International Nuclear Information System (INIS)

Tribeche, Mouloud; Bacha, Mustapha

2010-01-01

Arbitrary amplitude dust acoustic waves in a dusty plasma with a high-energy-tail electron distribution are investigated. The effects of charge variation and electron deviation from the Boltzmann distribution on the dust acoustic soliton are then considered. The dust charge variation makes the dust acoustic soliton more spiky. The dust grain surface collects less electrons as the latter evolves far away from their thermodynamic equilibrium. The dust accumulation caused by a balance of the electrostatic forces acting on the dust grains is more effective for lower values of the electron spectral index. Under certain conditions, the dust charge fluctuation may provide an alternate physical mechanism causing anomalous dissipation, the strength of which becomes important and may prevail over that of dispersion as the suprathermal character of the plasma becomes important. Our results may explain the strong spiky waveforms observed in auroral plasmas.

Energy of auroral electrons and Z mode generation

Science.gov (United States)

Krauss-Varban, D.; Wong, H. K.

1990-01-01

The present consideration of Z-mode radiation generation, in light of observational results indicating that the O mode and second-harmonic X-mode emissions can prevail over the X-mode fundamental radiation when suprathermal electron energy is low, gives attention to whether the thermal effect on the Z-mode dispersion can be equally important, and whether the Z-mode can compete for the available free-energy source. It is found that, under suitable circumstances, the growth rate of the Z-mode can be substantial even for low suprathermal auroral electron energies. Growth is generally maximized for propagation perpendicular to the magnetic field.

Bench mark spectra for high-energy neutron dosimetry

International Nuclear Information System (INIS)

Dierckx, R.

1986-01-01

To monitor radiation damage experiments, activation detectors are commonly used. The precision of the results obtained by the multiple foil analysis is largely increased by the intercalibration in bench-mark spectra. This technique is already used in dosimetry measurements for fission reactors. To produce neutron spectra similar to fusion reactor and high-energy high-intensity neutron sources (d-Li or spallation), accelerators can be used. Some possible solutions as p-Be and d-D 2 O neutron sources, useful as bench-mark spectra are described. (author)

Calculation of quantum-mechanical system energy spectra using path integrals

International Nuclear Information System (INIS)

Evseev, A.M.; Dmitriev, V.P.

1977-01-01

A solution of the Feynman quantum-mechanical integral connecting a wave function (psi (x, t)) at a moment t+tau (tau → 0) with the wave function at the moment t is provided by complex variable substitution and subsequent path integration. Time dependence of the wave function is calculated by the Monte Carlo method. The Fourier inverse transformation of the wave function by path integration calculated has been applied to determine the energy spectra. Energy spectra are presented of a hydrogen atom derived from wave function psi (x, t) at different x, as well as boson energy spectra of He, Li, and Be atoms obtained from psi (x, t) at X = O

On the origin of very-high-energy photons in astrophysics: a short introduction to acceleration and radiation physics

International Nuclear Information System (INIS)

Lemoine, M.; Pelletier, G.

2015-01-01

Powerful astrophysical sources produce non-thermal spectra of very-high-energy photons, with generic power-law distributions, through various radiative processes of charged particles, e.g., synchrotron radiation, inverse Compton processes, and hadronic interactions. Those charged particles have themselves been accelerated to ultra-relativistic energies in intense electromagnetic fields in the source. In many cases, the exact acceleration scheme is not known, but standard scenarios, such as Fermi mechanisms and reconnection processes are generally considered as prime suspects for the conversion of bulk kinetic or electromagnetic energy into a power law of supra-thermal particles. This paper proposes a short introduction to the various acceleration and radiative processes which shape the distributions of very-high-energy photons (E > 100 MeV) in astrophysics. (authors)

Ripple enhanced transport of suprathermal alpha particles

International Nuclear Information System (INIS)

Tani, K.; Takizuka, T.; Azumi, M.

1986-01-01

The ripple enhanced transport of suprathermal alpha particles has been studied by the newly developed Monte-Carlo code in which the motion of banana orbit in a toroidal field ripple is described by a mapping method. The existence of ripple-resonance diffusion has been confirmed numerically. We have developed another new code in which the radial displacement of banana orbit is given by the diffusion coefficients from the mapping code or the orbit following Monte-Carlo code. The ripple loss of α particles during slowing down has been estimated by the mapping model code as well as the diffusion model code. From the comparison of the results with those from the orbit-following Monte-Carlo code, it has been found that all of them agree very well. (author)

Energy spectra of odd nuclei in the generalized model

Directory of Open Access Journals (Sweden)

I. O. Korzh

2015-04-01

Full Text Available Based on the generalized nuclear model, energy spectra of the odd nuclei of such elements as 25Mg, 41K, and 65Cu are determined, and the structure of wave functions of these nuclei in the excited and normal states is studied. High quality in determining the energy spectra is possible due to the accurate calculations of all elements of the energy matrix. It is demonstrated that the structure of the wave functions so determined provides the possibility to more accurately select the nuclear model and the method for calculating the nucleon cross-sections of the inelastic scattering of nucleons by odd nuclei.

Temperatures of fragment kinetic energy spectra

International Nuclear Information System (INIS)

Bauer, W.

1995-01-01

Multifragmentation reactions without large compression in the initial state (proton-induced reactions, reverse kinematics, projectile fragmentation) are examined, and it is verified quantitatively that the high temperatures obtained from fragment kinetic energy spectra and lower temperatures obtained from observables such as level population or isotope ratios can be understood in a common framework

Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

Directory of Open Access Journals (Sweden)

P. Guio

Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.

Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines

Directory of Open Access Journals (Sweden)

P. Guio

1998-10-01

Full Text Available The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.Key words. Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response function

Energy spectra variations of high energy electrons in magnetic storms observed by ARASE and HIMAWARI

Science.gov (United States)

Takashima, T.; Higashio, N.; Mitani, T.; Nagatsuma, T.; Yoshizumi, M.

2017-12-01

The ARASE spacecraft was launched in December 20, 2016 to investigate mechanisms for acceleration and loss of relativistic electrons in the radiation belts during space storms. The six particle instruments with wide energy range (a few eV to 10MeV) are onboard the ARASE spacecraft. Especially, two particle instruments, HEP and XEP observe high energy electron with energy range from 70keV to over 10Mev. Those instruments observed several geomagnetic storms caused by coronal hole high speed streams or coronal mass ejections from March in 2017. The relativistic electrons in the outer radiation belt were disappeared/increased and their energy spectra were changed dynamically in some storms observed by XEP/HEP onboard the ARASE spacecraft. In the same time, SEDA-e with energy range 200keV-4.5MeV for electron on board the HIMAWARI-8, Japanese weather satellite on GEO, observed increase of relativistic electron in different local time. We will report on energy spectra variations of high energy electrons including calibrations of differential flux between XEP and HEP and discuss comparisons with energy spectra between ARAE and HIMAWARI that observed each storm in different local time.

Suprathermal electron studies in Tokamak plasmas by means of diagnostic measurements and modeling

International Nuclear Information System (INIS)

Kamleitner, J.

2015-01-01

To achieve reactor-relevant conditions in a tokamak plasma, auxiliary heating systems are required and can be realized by waves injected in the plasma that heat ions or electrons. Electron cyclotron resonant heating (ECRH) is a very flexible and robust technique featuring localized power deposition and current drive (CD) capabilities. Its fundamental principles are well understood and the application of ECRH is a proven and established tool; electron cyclotron current drive (ECCD) is regularly used to develop advanced scenarios and control magneto-hydrodynamics (MHD) instabilities in the plasma by tailoring the current profile. There remain important open questions, such as the phase space dynamics, the observed radial broadening of the supra-thermal electron distribution function and discrepancies in predicted and experimental CD efficiency. A main goal is to improve the understanding of wave-particle interaction in plasmas and current drive mechanisms. This was accomplished by combined experimental and numerical studies, strongly based on the conjunction of hard X-ray (HXR) Bremsstrahlung measurements and Fokker-Planck modelling, characterizing the supra-thermal electron population. The hard X-ray tomographic spectrometer (HXRS) diagnostic was developed to perform these studies by investigating spatial HXR emission asymmetries in the co- and counter-current directions and within the poloidal plane. The system uses cadmium-telluride detectors and digital acquisition to store the complete time history of incoming photon pulses. An extensive study of digital pulse processing algorithms was performed and its application allows the HXRS to handle high count rates in a noisy tokamak environment. Numerical tools were developed to improve the time resolution by conditional averaging and to obtain local information with the general tomographic inversion package. The interfaces of the LUKE code and the well-established CQL3D Fokker-Planck code to the Tokamak a

Calculated and experimental low-loss electron energy loss spectra of dislocations in diamond and GaN

CERN Document Server

Jones, R; Gutiérrez-Sosa, A; Bangert, U; Heggie, M I; Blumenau, A T; Frauenheim, T; Briddon, P R

2002-01-01

First-principles calculations of electron energy loss (EEL) spectra for bulk GaN and diamond are compared with experimental spectra acquired with a scanning tunnelling electron microscope offering ultra-high-energy resolution in low-loss energy spectroscopy. The theoretical bulk low-loss EEL spectra, in the E sub g to 10 eV range, are in good agreement with experimental data. Spatially resolved spectra from dislocated regions in both materials are distinct from bulk spectra. The main effects are, however, confined to energy losses lying above the band edge. The calculated spectra for low-energy dislocations in diamond are consistent with the experimental observations, but difficulties remain in understanding the spectra of threading dislocations in GaN.

Statistics of counter-streaming solar wind suprathermal electrons at solar minimum: STEREO observations

Directory of Open Access Journals (Sweden)

B. Lavraud

2010-01-01

Full Text Available Previous work has shown that solar wind suprathermal electrons can display a number of features in terms of their anisotropy. Of importance is the occurrence of counter-streaming electron patterns, i.e., with "beams" both parallel and anti-parallel to the local magnetic field, which is believed to shed light on the heliospheric magnetic field topology. In the present study, we use STEREO data to obtain the statistical properties of counter-streaming suprathermal electrons (CSEs in the vicinity of corotating interaction regions (CIRs during the period March–December 2007. Because this period corresponds to a minimum of solar activity, the results are unrelated to the sampling of large-scale coronal mass ejections, which can lead to CSE owing to their closed magnetic field topology. The present study statistically confirms that CSEs are primarily the result of suprathermal electron leakage from the compressed CIR into the upstream regions with the combined occurrence of halo depletion at 90° pitch angle. The occurrence rate of CSE is found to be about 15–20% on average during the period analyzed (depending on the criteria used, but superposed epoch analysis demonstrates that CSEs are preferentially observed both before and after the passage of the stream interface (with peak occurrence rate >35% in the trailing high speed stream, as well as both inside and outside CIRs. The results quantitatively show that CSEs are common in the solar wind during solar minimum, but yet they suggest that such distributions would be much more common if pitch angle scattering were absent. We further argue that (1 the formation of shocks contributes to the occurrence of enhanced counter-streaming sunward-directed fluxes, but does not appear to be a necessary condition, and (2 that the presence of small-scale transients with closed-field topologies likely also contributes to the occurrence of counter-streaming patterns, but only in the slow solar wind prior to

The sub-bandgap energy loss satellites in the RIXS spectra of beryllium compounds

International Nuclear Information System (INIS)

Kuusik, I.; Kaeaembre, T.; Kooser, K.; Pustovarov, V.; Ivanov, V.; Kukk, E.; Kikas, A.

2011-01-01

Research highlights: → Be 1s RIXS spectra have been measured in Be containing crystals phenakite and chrysoberyl. → A strong energy loss sideband to the elastic scattering peak similar to BeO is found in both minerals. → Additionally the Si 2p RIXS spectra of phenakite also show a strong energy loss sideband to the elastic scattering peak. → The energy loss shoulder appears to result from lattice relaxation in the absorption site. - Abstract: Resonant X-ray inelastic scattering spectra have been measured in BeO, phenakite (Be 2 SiO 4 ) and chrysoberyl (BeAl 2 O 4 ) with the excitation energy near the beryllium K edge. The RIXS spectra excited in the vicinity of the Be 1s core resonance show two principal features: the scattering on a valence excitation (which at higher excitation energies verges into the characteristic K α emission), and a remarkably strong energy loss sideband to the elastic scattering peak. The energy loss shoulder appears to result from lattice relaxation in the absorption site. The comparison of the RIXS spectra of phenakite, chrysoberyl and BeO shows that the strength of the low energy sideband differs greatly; it is strongest in BeO and weakest in phenakite. The Si 2p RIXS spectra of phenakite also display a similar strong sub-bandgap energy loss tail. To gain further insight to this process, transitions in a system with a single vibrational mode have been modelled. The phonon relaxation has been simulated empirically by 'smearing' the photoabsortion-populated vibrational levels with lower levels. This simple model is able to qualitatively explain this wide energy loss shoulder.

The sub-bandgap energy loss satellites in the RIXS spectra of beryllium compounds

Energy Technology Data Exchange (ETDEWEB)

Kuusik, I., E-mail: ivar@fi.tartu.ee [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Kaeaembre, T. [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Kooser, K. [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Department of Physics and Astronomy, University of Turku, Turku (Finland); Pustovarov, V.; Ivanov, V. [Ural State Technical University-UPI, Yekaterinburg (Russian Federation); Kukk, E. [Department of Physics and Astronomy, University of Turku, Turku (Finland); Kikas, A. [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia)

2011-07-15

Research highlights: {yields} Be 1s RIXS spectra have been measured in Be containing crystals phenakite and chrysoberyl. {yields} A strong energy loss sideband to the elastic scattering peak similar to BeO is found in both minerals. {yields} Additionally the Si 2p RIXS spectra of phenakite also show a strong energy loss sideband to the elastic scattering peak. {yields} The energy loss shoulder appears to result from lattice relaxation in the absorption site. - Abstract: Resonant X-ray inelastic scattering spectra have been measured in BeO, phenakite (Be{sub 2}SiO{sub 4}) and chrysoberyl (BeAl{sub 2}O{sub 4}) with the excitation energy near the beryllium K edge. The RIXS spectra excited in the vicinity of the Be 1s core resonance show two principal features: the scattering on a valence excitation (which at higher excitation energies verges into the characteristic K{sub {alpha}} emission), and a remarkably strong energy loss sideband to the elastic scattering peak. The energy loss shoulder appears to result from lattice relaxation in the absorption site. The comparison of the RIXS spectra of phenakite, chrysoberyl and BeO shows that the strength of the low energy sideband differs greatly; it is strongest in BeO and weakest in phenakite. The Si 2p RIXS spectra of phenakite also display a similar strong sub-bandgap energy loss tail. To gain further insight to this process, transitions in a system with a single vibrational mode have been modelled. The phonon relaxation has been simulated empirically by 'smearing' the photoabsortion-populated vibrational levels with lower levels. This simple model is able to qualitatively explain this wide energy loss shoulder.

Contribution of recently measured nuclear data to reactor antineutrino energy spectra predictions

Directory of Open Access Journals (Sweden)

Fallot M.

2013-12-01

Full Text Available This paper attempts to summarize the actual problematic of reactor antineutrino energy spectra in the frame of fundamental and applied neutrino physics. Nuclear physics is an important ingredient of reactor antineutrino experiments. These experiments are motivated by neutrino oscillations, i.e. the measure of the θ13 mixing angle. In 2011, after a new computation of the reactor antineutrino energy spectra, based on the conversion of integral data of the beta spectra from 235U, and 239;241Pu, a deficit of reactor antineutrinos measured by short baseline experiments was pointed out. This is called the “reactor anomaly”, a new puzzle in the neutrino physics area. Since then, numerous new experimental neutrino projects have emerged. In parallel, computations of the antineutrino spectra independant from the ILL data would be desirable. One possibility is the use of the summation method, summing all the contributions of the fission product beta decay branches that can be found in nuclear databases. Studies have shown that in order to obtain reliable summation antineutrino energy spectra, new nuclear physics measurements of selected fission product beta decay properties are required. In these proceedings, we will present the computation methods of reactor antineutrino energy spectra and the impact of recent beta decay measurements on summation method spectra. The link of these nuclear physics studies with short baseline line oscillation search will be drawn and new neutrino physics projects at research reactors will be briefly presented.

Perturbative description of inclusive energy spectra

Energy Technology Data Exchange (ETDEWEB)

Lupia, S. [Max-Planck-Institut fuer Physik, Muenchen (Germany). Werner-Heisenberg-Institut

1996-03-01

The recent LEP-1.5 data of charged particle inclusive energy spectra are analyzed within the analytical QCD approach based on modified leading log approximation plus local parton hadron duality. The shape, the position of the maximum and the cumulant moments of the inclusive energy spectrum are well described within this model. The sensitivity of the results to the running of the coupling is pointed out. A scaling law for the one-particle invariant density E dn/d{sup 3}p at small momenta is observed, consistently with the predictions of colour coherence in soft gluon bremsstrahlung. (orig.).

Perturbative description of inclusive energy spectra

International Nuclear Information System (INIS)

Lupia, S.

1996-01-01

The recent LEP-1.5 data of charged particle inclusive energy spectra are analyzed within the analytical QCD approach based on modified leading log approximation plus local parton hadron duality. The shape, the position of the maximum and the cumulant moments of the inclusive energy spectrum are well described within this model. The sensitivity of the results to the running of the coupling is pointed out. A scaling law for the one-particle invariant density E dn/d 3 p at small momenta is observed, consistently with the predictions of colour coherence in soft gluon bremsstrahlung. (orig.)

Measurement of time-dependent fast neutron energy spectra in a depleted uranium assembly

International Nuclear Information System (INIS)

Whittlestone, S.

1980-10-01

Time-dependent neutron energy spectra in the range 0.6 to 6.4 MeV have been measured in a depleted uranium assembly. By selecting windows in the time range 0.9 to 82 ns after the beam pulse, it was possible to observe the change of the neutron energy distributions from spectra of predominantly 4 to 6 MeV neutrons to spectra composed almost entirely of fission neutrons. The measured spectra were compared to a Monte Carlo calculation of the experiment using the ENDF/B-IV data file. At times and energies at which the calculation predicted a fission spectrum, the experiment agreed with the calculation, confirming the accuracy of the neutron spectroscopy system. However, the presence of discrepancies at other times and energies suggested that there are significant inconsistencies in the inelastic cross sections in the 1 to 6 MeV range. The time response generated concurrently with the energy spectra was compared to the Monte Carlo calculation. From this comparison, and from examination of time spectra measured by other workers using 235 U and 237 Np fission detectors, it would appear that there are discrepancies in the ENDF/B-IV cross sections below 1 MeV. The predicted decay rates were too low below and too high above 0.8 MeV

Observations of discrete energy loss effects in spectra of positrons reflected from solid surfaces

International Nuclear Information System (INIS)

Dale, J.M.; Hulett, L.D.; Pendyala, S.

1980-01-01

Surfaces of tungsten and silicon have been bombarded with monoenergetic beams of positrons and electrons. Spectra of reflected particles show energy loss tails with discrete peaks at kinetic energies about 15 eV lower than that of the elastic peaks. In the higher energy loss range for tungsten, positron spectra show fine structure that is not apparent in the electron spectra. This suggests that the positrons are losing energy through mechanisms different from that of the electrons

D-D neutron energy-spectra measurements in Alcator C

International Nuclear Information System (INIS)

Pappas, D.S.; Wysocki, F.J.; Furnstahl, R.J.

1982-08-01

Measurements of energy spectra of neutrons produced during high density (anti n/sub e/ > 2 x 10 14 cm -3 ) deuterium discharges have been performed using a proton-recoil (NE 213) spectrometer. A two foot section of light pipe (coupling the scintillator and photomultiplier) was used to extend the scintillator into a diagnostic viewing port to maximize the neutron detection efficiency while not imposing excessive magnetic shielding requirements. A derivative unfolding technique was used to deduce the energy spectra. The results showed a well defined peak at 2.5 MeV which was consistent with earlier neutron flux measurements on Alcator C that indicated the neutrons were of thermonuclear origin

78 FR 35658 - Spectra Energy Corp., Application for a New or Amended Presidential Permit

Science.gov (United States)

2013-06-13

... Express into a limited liability corporation, Express Holdings (USA), LLC. Spectra plans to assign 40% of...-traded master limited partnership. Spectra Energy has control over Spectra Energy Partners, LP; it indirectly owns 58% of the ownership interests in the limited partnership and also indirectly owns 100% of...

EVOLUTION OF MAGNETIC HELICITY AND ENERGY SPECTRA OF SOLAR ACTIVE REGIONS

International Nuclear Information System (INIS)

Zhang, Hongqi; Brandenburg, Axel; Sokoloff, D. D.

2016-01-01

We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field to estimate the magnetic energy and helicity spectra as well as current helicity spectra of two individual active regions (NOAA 11158 and NOAA 11515) and the change of the spectral indices during their development as well as during the solar cycle. The departure of the spectral indices of magnetic energy and current helicity from 5/3 are analyzed, and it is found that it is lower than the spectral index of the magnetic energy spectrum. Furthermore, the fractional magnetic helicity tends to increase when the scale of the energy-carrying magnetic structures increases. The magnetic helicity of NOAA 11515 violates the expected hemispheric sign rule, which is interpreted as an effect of enhanced field strengths at scales larger than 30–60 Mm with opposite signs of helicity. This is consistent with the general cycle dependence, which shows that around the solar maximum the magnetic energy and helicity spectra are steeper, emphasizing the large-scale field

EVOLUTION OF MAGNETIC HELICITY AND ENERGY SPECTRA OF SOLAR ACTIVE REGIONS

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hongqi [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Brandenburg, Axel [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden); Sokoloff, D. D., E-mail: hzhang@bao.ac.cn [Department of Physics, Moscow University, 119992 Moscow (Russian Federation)

2016-03-10

We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field to estimate the magnetic energy and helicity spectra as well as current helicity spectra of two individual active regions (NOAA 11158 and NOAA 11515) and the change of the spectral indices during their development as well as during the solar cycle. The departure of the spectral indices of magnetic energy and current helicity from 5/3 are analyzed, and it is found that it is lower than the spectral index of the magnetic energy spectrum. Furthermore, the fractional magnetic helicity tends to increase when the scale of the energy-carrying magnetic structures increases. The magnetic helicity of NOAA 11515 violates the expected hemispheric sign rule, which is interpreted as an effect of enhanced field strengths at scales larger than 30–60 Mm with opposite signs of helicity. This is consistent with the general cycle dependence, which shows that around the solar maximum the magnetic energy and helicity spectra are steeper, emphasizing the large-scale field.

Energy spectra of primary knock-on atoms under neutron irradiation

International Nuclear Information System (INIS)

Gilbert, M.R.; Marian, J.; Sublet, J.-Ch.

2015-01-01

Materials subjected to neutron irradiation will suffer from a build-up of damage caused by the displacement cascades initiated by nuclear reactions. Previously, the main “measure” of this damage accumulation has been through the displacements per atom (dpa) index, which has known limitations. This paper describes a rigorous methodology to calculate the primary atomic recoil events (often called the primary knock-on atoms or PKAs) that lead to cascade damage events as a function of energy and recoiling species. A new processing code SPECTRA-PKA combines a neutron irradiation spectrum with nuclear recoil data obtained from the latest nuclear data libraries to produce PKA spectra for any material composition. Via examples of fusion relevant materials, it is shown that these PKA spectra can be complex, involving many different recoiling species, potentially differing in both proton and neutron number from the original target nuclei, including high energy recoils of light emitted particles such as α-particles and protons. The variations in PKA spectra as a function of time, neutron field, and material are explored. The application of PKA spectra to the quantification of radiation damage is exemplified using two approaches: the binary collision approximation and stochastic cluster dynamics, and the results from these different models are discussed and compared. - Highlights: • Recoil cross-section matrices under neutron irradiation are generated. • Primary knock-on atoms (PKA) spectra are calculated for fusion relevant materials. • Variation in PKA spectra due to changes in geometry are considered. • Inventory simulations to consider time-evolution in PKA spectra. • Damage quantification using damage functions from different approximations.

Measurements of time dependent energy spectra of neutrons in a small graphite assembly

International Nuclear Information System (INIS)

Fujita, Yoshiaki; Sakamoto, Shigeyasu; Aizawa, Otohiko; Takahashi, Akito; Sumita, Kenji.

1975-01-01

The time-dependent energy spectra of neutrons have been measured in a small 30x30x30 cm 3 graphite assembly by means of the linac-chopper method, with a view to establishing experimental evidence that there is no asymptotic spectrum in such a small assembly, and in order to study the non-asymptotic behavior of neutrons. The arrangement of a polyethylene pre-moderator adjacent to the assembly made the measurements possible with the improvement obtained thereby of the neutron counting statistics. It was indicated from calculation that the presence of the pre-moderator had little effect - at least above the Bragg cut-off energy - on the evolution in time of the energy spectra of neutrons in the graphite assembly. The experimental results indicated very probable disappearance of asymptotic spectra, and revealed significant enhancement of trapping at Bragg energies with the lapse of time. This is consistent with the results of pulsed neutron experiments in small assemblies conducted by Takahashi et al., and falls in line with de Saussure's approximation. The spectra in the graphite assembly showed significant space dependence, the spectra becoming harder with increasing distance from the pre-moderator. This hardening may be attributed to the relatively faster propagation of higher energy neutrons. (auth.)

Simulation of electron energy loss spectra of nanomaterials with linear-scaling density functional theory

International Nuclear Information System (INIS)

Tait, E W; Payne, M C; Ratcliff, L E; Haynes, P D; Hine, N D M

2016-01-01

Experimental techniques for electron energy loss spectroscopy (EELS) combine high energy resolution with high spatial resolution. They are therefore powerful tools for investigating the local electronic structure of complex systems such as nanostructures, interfaces and even individual defects. Interpretation of experimental electron energy loss spectra is often challenging and can require theoretical modelling of candidate structures, which themselves may be large and complex, beyond the capabilities of traditional cubic-scaling density functional theory. In this work, we present functionality to compute electron energy loss spectra within the onetep linear-scaling density functional theory code. We first demonstrate that simulated spectra agree with those computed using conventional plane wave pseudopotential methods to a high degree of precision. The ability of onetep to tackle large problems is then exploited to investigate convergence of spectra with respect to supercell size. Finally, we apply the novel functionality to a study of the electron energy loss spectra of defects on the (1 0 1) surface of an anatase slab and determine concentrations of defects which might be experimentally detectable. (paper)

Trajectory resolved analysis of LEIS energy spectra: Neutralization and surface structure

International Nuclear Information System (INIS)

Beikler, Robert; Taglauer, Edmund

2001-01-01

For a quantitative evaluation of low-energy ion scattering (LEIS) data with respect to surface composition and structure a detailed analysis of the energy spectra is required. This includes the identification of multiple scattering processes and the determination of ion survival probabilities. We analyzed scattered ion energy spectra by using the computer code MARLOWE for which we developed a new analysis routine that allows to record energy distributions in dependence of the number of projectile-target atom collisions, in dependence of the distance of closest approach, or in dependence of the scattering crystalline layer. This procedure also permits the determination of ion survival probabilities by applying simple collision-dependent neutralization models. Experimental energy spectra for various projectile (He + , Ne + , Na + ) and target (transition metals, oxides) combinations are well reproduced and quantitative results for ion survival probabilities are obtained. These are largely in agreement with results obtained for bimetallic crystal surfaces obtained in a different way. Such MARLOWE calculations are also useful for the identification of structure relevant processes. This is shown exemplarily for the reconstructed Au(1 1 0) surface including a possibility to determine the (1x2)→(1x1) transition temperature

Beta spectra. II-Positron spectra

International Nuclear Information System (INIS)

Grau, A.; Garcia-Torano, E.

1981-01-01

Using the Fermi theory of beta decay, the beta spectra for 30 positron emitters have been computed, introducing a correction factor for unique forbidden transitions. The spectra are ploted vs. energy, once normalised, and tabulated with the related Fermi functions. The average and median energies are calculated. (author)

Kinetic energy and scalar spectra in high Rayleigh number axially homogeneous buoyancy driven turbulence

Science.gov (United States)

Pawar, Shashikant S.; Arakeri, Jaywant H.

2016-06-01

Kinetic energy and scalar spectra from the measurements in high Rayleigh number axially homogeneous buoyancy driven turbulent flow are presented. Kinetic energy and concentration (scalar) spectra are obtained from the experiments wherein density difference is created using brine and fresh water and temperature spectra are obtained from the experiments in which heat is used. Scaling of the frequency spectra of lateral and longitudinal velocity near the tube axis is closer to the Kolmogorov-Obukhov scaling, while the scalar spectra show some evidence of dual scaling, Bolgiano-Obukhov scaling followed by Obukhov-Corrsin scaling. These scalings are also observed in the corresponding second order spatial structure functions of velocity and concentration fluctuations.

Study of profile control and suprathermal electron production with lower hybrid waves

International Nuclear Information System (INIS)

Soeldner, F.X.; Brambilla, M.; Leuterer, F.; Muenich, M.

1986-05-01

In this study the coupling of LH waves to suprathermal electrons, the LH current drive efficiency and the mechanism for sawtooth stabilisation will be discussed. A wide data base has been obtained by the LH experiments on Alcator C, ASDEX, FT; JFT-2M, JIPPT-IIU, Petula, PLT, Versator, WT II during the last years and important aspects as the scaling of global current drive efficiency are satisfactorily described by theory. We mainly rely here on experimental results from ASDEX and comparison with theoretical calculations by Fisch and Karney. (orig.)

Energy-loss spectra of charged particles in the presence of charge exchange: Addendum on 6Li spectra

International Nuclear Information System (INIS)

Glazov, Lev; Sigmund, Peter

2000-01-01

Charge-dependent energy-loss spectra for swift Li ions penetrating thin carbon foils have been evaluated theoretically. As in our earlier study on He ions we reproduce the main features in experimental data by Ogawa and coworkers, but calculated spectra are narrower than measured, mainly because of limited experimental resolution. Comments are made on a theoretical study by Balashov and coworkers who analysed the same experimental data but arrived at very different conclusions

Suprathermal electron environment of comet 67P/Churyumov-Gerasimenko: Observations from the Rosetta Ion and Electron Sensor

Science.gov (United States)

Clark, G.; Broiles, T. W.; Burch, J. L.; Collinson, G. A.; Cravens, T.; Frahm, R. A.; Goldstein, J.; Goldstein, R.; Mandt, K.; Mokashi, P.; Samara, M.; Pollock, C. J.

2015-11-01

Context. The Rosetta spacecraft is currently escorting comet 67P/Churyumov-Gerasimenko until its perihelion approach at 1.2 AU. This mission has provided unprecedented views into the interaction of the solar wind and the comet as a function of heliocentric distance. Aims: We study the interaction of the solar wind and comet at large heliocentric distances (>2 AU) using data from the Rosetta Plasma Consortium Ion and Electron Sensor (RPC-IES). From this we gain insight into the suprathermal electron distribution, which plays an important role in electron-neutral chemistry and dust grain charging. Methods: Electron velocity distribution functions observed by IES fit to functions used to previously characterize the suprathermal electrons at comets and interplanetary shocks. We used the fitting results and searched for trends as a function of cometocentric and heliocentric distance. Results: We find that interaction of the solar wind with this comet is highly turbulent and stronger than expected based on historical studies, especially for this weakly outgassing comet. The presence of highly dynamical suprathermal electrons is consistent with observations of comets (e.g., Giacobinni-Zinner, Grigg-Skjellerup) near 1 AU with higher outgassing rates. However, comet 67P/Churyumov-Gerasimenko is much farther from the Sun and appears to lack an upstream bow shock. Conclusions: The mass loading process, which likely is the cause of these processes, plays a stronger role at large distances from the Sun than previously expected. We discuss the possible mechanisms that most likely are responsible for this acceleration: heating by waves generated by the pick-up ion instability, and the admixture of cometary photoelectrons.

BETA SPECTRA. I. Negatrons spectra

International Nuclear Information System (INIS)

Grau Malonda, A.; Garcia-Torano, E.

1978-01-01

Using the Fermi theory of beta decay, the beta spectra for 62 negatrons emitters have been computed introducing a correction factor for unique forbidden transitions. These spectra are plotted vs. energy, once normal i sed, and tabulated with the related Fermi functions. The average and median energies are calculated. (Author)

Energy spectra of neutrons accompanying the emission fission of 238U

International Nuclear Information System (INIS)

Smirenkin, G.N.; Lovchikova, G.N.; Trufanov, A.M.; Svirin, M.I.; Polyakov, A.V.; Vinogradov, V.A.; Dmitriev, V.D.; Boykov, G.S.

1996-01-01

The spectra of fission neutrons emitted from 238U are measured for the first time by the time-of-flight method at incident-neutron energies of 16.0 and 17.7 MeV. Analysis of the neutron spectra shows that experimental results at incident-neutron energies of 14.7, 16.0, and 17.7 MeV (above the threshold of chance fission) differ significantly from those obtained at a neutron energy of 2.9 MeV (below the threshold of chance fission). Owing to the prefission emission of neutrons, the observed spectra of neutrons from emission fission exhibit a characteristic growth of the neutron yield in both hard and soft sections of the spectrum of secondary neutrons. This growth manifests itself as a step in the first case and as a rise in the second case, where it results in a noticeable excess of neutrons over the statistical-model predictions for E<2 MeV. The first feature in the spectra of neutrons from emission fission can be associated with the nonequilibrium decay of an excited fissile nucleus. On the contrary, the origin of the second feature has yet to be clarified. Additional measurements of angular distributions of secondary neutrons may prove helpful in this respect

Interplanetary ions during an energetic storm particle event - The distribution function from solar wind thermal energies to 1.6 MeV

Science.gov (United States)

Gosling, J. T.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Zwickl, R. D.; Paschmann, G.; Sckopke, N.; Hynds, R. J.

1981-01-01

An ion velocity distribution function of the postshock phase of an energetic storm particle (ESP) event is obtained from data from the ISEE 2 and ISEE 3 experiments. The distribution function is roughly isotropic in the solar wind frame from solar wind thermal energies to 1.6 MeV. The ESP event studied (8/27/78) is superposed upon a more energetic particle event which was predominantly field-aligned and which was probably of solar origin. The observations suggest that the ESP population is accelerated directly out of the solar wind thermal population or its quiescent suprathermal tail by a stochastic process associated with shock wave disturbance. The acceleration mechanism is sufficiently efficient so that approximately 1% of the solar wind population is accelerated to suprathermal energies. These suprathermal particles have an energy density of approximately 290 eV cubic centimeters.

Generation of suprathermal electrons during plasma current startup by lower hybrid waves in a tokamak

International Nuclear Information System (INIS)

Ohkubo, K.; Toi, K.; Kawahata, K.

1984-10-01

Suprathermal electrons which carry a seed current are generated by non-resonant parametric decay instability during initial phase of lower hybrid current startup in the JIPP T-IIU tokamak. From the numerical analysis, it is found that parametrically excited lower hybrid waves at lower side band can bridge the spectral gap between the thermal velocity and the low velocity end in the pump power spectrum. (author)

Derivation of electron and photon energy spectra from electron beam central axis depth dose curves

Energy Technology Data Exchange (ETDEWEB)

Deng Jun [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States)]. E-mail: jun@reyes.stanford.edu; Jiang, Steve B.; Pawlicki, Todd; Li Jinsheng; Ma, C.M. [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States)

2001-05-01

A method for deriving the electron and photon energy spectra from electron beam central axis percentage depth dose (PDD) curves has been investigated. The PDD curves of 6, 12 and 20 MeV electron beams obtained from the Monte Carlo full phase space simulations of the Varian linear accelerator treatment head have been used to test the method. We have employed a 'random creep' algorithm to determine the energy spectra of electrons and photons in a clinical electron beam. The fitted electron and photon energy spectra have been compared with the corresponding spectra obtained from the Monte Carlo full phase space simulations. Our fitted energy spectra are in good agreement with the Monte Carlo simulated spectra in terms of peak location, peak width, amplitude and smoothness of the spectrum. In addition, the derived depth dose curves of head-generated photons agree well in both shape and amplitude with those calculated using the full phase space data. The central axis depth dose curves and dose profiles at various depths have been compared using an automated electron beam commissioning procedure. The comparison has demonstrated that our method is capable of deriving the energy spectra for the Varian accelerator electron beams investigated. We have implemented this method in the electron beam commissioning procedure for Monte Carlo electron beam dose calculations. (author)

The effect of work function changes on secondary ion energy spectra

International Nuclear Information System (INIS)

Wittmaack, K.

1983-01-01

The effect of work function changes on experimental secondary ion energy spectra is discussed. In agreement with theory the measured ion intensities frequently exhibit an exponential work function dependence. However, the predicted velocity dependence is only observed at fairly high secondary ion energies. In the absence of a velocity dependence of the degree of ionization measured shifts of energy spectra reflect work function changes directly. Various instrumental problems are shown to aggravate a detailed comparison between experiment and theory. Significant artefacts must be expected if the extraction field is of the order of or less than the lateral field induced by a work function difference between the bombarded spot and the surrounding sample surface. (Auth.)

Energy Spectra of Abundant Cosmic-ray Nuclei in Sources, According to the ATIC Experiment

Energy Technology Data Exchange (ETDEWEB)

Panov, A. D.; Sokolskaya, N. V.; Zatsepin, V. I., E-mail: panov@dec1.sinp.msu.ru [Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow, 119991 (Russian Federation)

2017-03-01

One of the main results of the ATIC (Advanced Thin Ionization Calorimeter) experiment is a collection of energy spectra of abundant cosmic-ray nuclei: protons, He, C, O, Ne, Mg, Si, and Fe measured in terms of energy per particle in the energy range from 50 GeV to tens of teraelectronvolts. In this paper, the ATIC energy spectra of abundant primary nuclei are back-propagated to the spectra in sources in terms of magnetic rigidity using a leaky-box approximation of three different GALPROP-based diffusion models of propagation that fit the latest B/C data of the AMS-02 experiment. It is shown that the results of a comparison of the slopes of the spectra in sources are weakly model dependent; therefore the differences of spectral indices are reliable data. A regular growth of the steepness of spectra in sources in the range of magnetic rigidity of 50–1350 GV is found for a charge range from helium to iron. This conclusion is statistically reliable with significance better than 3.2 standard deviations. The results are discussed and compared to the data of other modern experiments.

Neutron energy spectra produced by α-bombardment of light elements in thick targets

International Nuclear Information System (INIS)

Jacobs, G.J.H.

1982-01-01

The aim of the work, presented in this thesis, is to determine energy spectra of neutrons produced by α-particle bombardment of thick targets containing light elements. These spectra are required for nuclear waste management. The set-up of the neutron spectrometer is described, and its calibration discussed. Absolute efficiencies were determined at various neutron energies, using monoenergetic neutrons produced with the Van de Graaff accelerator in pulsed mode. The additional calibration of the neutron spectrometer as proton-recoil spectrometer was carried out primarily for future applications in measurements where no pulsed neutron source is available or the neutron flux density is too low. The basis for an accurate uncertainty analysis is made by the determination of the covariance matrix for the uncertainties in the efficiencies. The determination of the neutron energy spectra from time-of-flight and from proton-recoil measurements is described. A comparison of the results obtained from the two different types of measurements is made. The experimentally determined spectra were compared with spectra calculated from stopping powers and theoretically determined cross sections. These cross sections were calculated from optical model parameters and level parameters using the Hauser-Feshbach formalism. Measurements were carried out on thick targets of silicon, aluminium, magnesium, carbon, boron nitride, calcium fluoride, aluminium oxide, silicon oxide and uranium oxide at four different α-particle energies. (Auth.)

Neutron energy spectra from the thick target 9Be(d,n)10B reaction

International Nuclear Information System (INIS)

Whittlestone, S.

1976-12-01

The energy spectrum of neutrons emitted when deuterons impinge on a thick beryllium target has been measured using an NE213 scintillation detector and the time-of-flight technique. Spectra were measured at angles of 0, 30, 45, 60, 90, 120 and 150 0 for deuteron energies of 1.4, 1.8, 2.3 and 2.8 MeV. Tables are presented of these angle-dependent energy spectra, the angle-integrated energy dependent yeidls, and the total neutron yield as a function of deuteron energy. (author)

WSEAT Shock Testing Margin Assessment Using Energy Spectra Final Report.

Energy Technology Data Exchange (ETDEWEB)

Sisemore, Carl; Babuska, Vit; Booher, Jason

2018-02-01

Several programs at Sandia National Laboratories have adopted energy spectra as a metric to relate the severity of mechanical insults to structural capacity. The purpose being to gain insight into the system's capability, reliability, and to quantify the ultimate margin between the normal operating envelope and the likely system failure point -- a system margin assessment. The fundamental concern with the use of energy metrics was that the applicability domain and implementation details were not completely defined for many problems of interest. The goal of this WSEAT project was to examine that domain of applicability and work out the necessary implementation details. The goal of this project was to provide experimental validation for the energy spectra based methods in the context of margin assessment as they relate to shock environments. The extensive test results concluded that failure predictions using energy methods did not agree with failure predictions using S-N data. As a result, a modification to the energy methods was developed following the form of Basquin's equation to incorporate the power law exponent for fatigue damage. This update to the energy-based framework brings the energy based metrics into agreement with experimental data and historical S-N data.

Two-proton energy spectra of 12O nucleus

International Nuclear Information System (INIS)

Teruya, N.

2010-01-01

Full text: The two-proton radioactivity has attracted stimulating discussion concerning the competing mechanisms for the decay process. Some nuclei (like 45 Fe, 41 Ni and 54 Zn are considered as genuine ground-state two-proton emitter because the only possibility is the simultaneous channel, but others nuclei (as 12 O) can also have the sequential decay, in this case, the energy levels of the intermediary one-proton emitter nuclei plays an important role to the competition with the simultaneous decay mode. In this work we have calculated the energy spectra of 12 O, including ground state and excited states up to 5 MeV of energy, and the two-proton energy difference spectrum for the ground state decay. Our preliminary results estimates the energy peak and width of resonant excited states and contributions of simultaneous and sequential channels for ground state decay. The calculation method is based on the statistical analysis for two-proton decaying modes presented in previous work. For events generated by sequential channels, the energy levels of intermediary 11 N nucleus can dominate the first proton emission, depending on the proximity between the ground states of both nuclei, 11 N and 12 O , in particular, if the ground state of 11 N is broad and its energy is far away from that of 12 O, the sequential decay occurs via the tail of the ground state of 11 O. The decay of 12 O resonant ground state and higher energy excited resonances are investigated through the analysis of the experimental data for the two-proton emission process. The two proton decay spectra have been considered in a statistical calculation framework, by using the decay energy distribution and taken into account the intermediate states of 11 N resonant structures for the sequential channels. For simultaneous decay channel we construct a symmetric distribution similarly to Goldansky's proposition in Nucl. Phys. A19, 482 (1960). (author)

Initial electron energy spectra in water irradiated by photons with energies to 1 GeV

International Nuclear Information System (INIS)

Todo, A.S.; Hiromoto, G.; Turner, J.E.; Hamm, R.N.; Wright, H.A.

1984-02-01

This work was undertaken to provide basic physical data for use in the dosimetry of high-energy photons. Present and future sources of such photons are described, and the relevant literature is reviewed and summarized. Calculations were performed with a Monte Carlo computer code, PHOEL-3, which is also described. Tables of initial electron and positron energies are presented for monoenergetic photons undergoing single interactions in water. Photon energies to 1 GeV are treated. The code treats explicitly the production of electron-positron pairs, Compton scattering, photoelectric absorption, and the emission of Auger electrons following the occurrence of K-shell vacancies in oxygen. The tables give directly the information needed to specify the absolute single-collision kerma in water, which approximates tissue, at each photon energy. Results for continuous photon energy spectra can be obtained by using linear interpolation with the tables. (Continuous spectra can also be used directly in PHOEL-3.) The conditions under whch first-collision kerma approximate absorbed dose are discussed. A formula is given for estimating bremsstrahlung energy loss, one of the principal differences between kerma and absorbed dose in practical cases. 31 references, 4 figures, 18 tables

Energy spectra of quantum rings.

Science.gov (United States)

Fuhrer, A; Lüscher, S; Ihn, T; Heinzel, T; Ensslin, K; Wegscheider, W; Bichler, M

2001-10-25

Quantum mechanical experiments in ring geometries have long fascinated physicists. Open rings connected to leads, for example, allow the observation of the Aharonov-Bohm effect, one of the best examples of quantum mechanical phase coherence. The phase coherence of electrons travelling through a quantum dot embedded in one arm of an open ring has also been demonstrated. The energy spectra of closed rings have only recently been studied by optical spectroscopy. The prediction that they allow persistent current has been explored in various experiments. Here we report magnetotransport experiments on closed rings in the Coulomb blockade regime. Our experiments show that a microscopic understanding of energy levels, so far limited to few-electron quantum dots, can be extended to a many-electron system. A semiclassical interpretation of our results indicates that electron motion in the rings is governed by regular rather than chaotic motion, an unexplored regime in many-electron quantum dots. This opens a way to experiments where even more complex structures can be investigated at a quantum mechanical level.

Proposal of energy spectra for earthquake resistant design based on turkish registers

OpenAIRE

Yazgan, Ahmet Utku

2012-01-01

This work proposes design energy spectra in terms of an equivalent velocity, intended for regions with design peak acceleration 0.3 g or higher. These spectra have been derived through linear and nonlinear dynamic analyses on a number of Turkish selected strong ground motion records. In the long and mid period ranges the analyses are linear, taking profit of the rather insensitivity of the spectra to the structural parameters other than the fundamental period; conversely, in the short period ...

Measurement and modelling of suprathermal electron bursts generated in front of a lower hybrid antenna

Czech Academy of Sciences Publication Activity Database

Gunn, J. P.; Fuchs, Vladimír; Petržílka, Václav; Ekedahl, A.; Fedorczak, N.; Goniche, M.; Hillairet, J.

2016-01-01

Roč. 56, č. 3 (2016), č. článku 036004. ISSN 0029-5515 R&D Projects: GA MŠk(CZ) LM2011021 Institutional support: RVO:61389021 Keywords : lower hybrid * scrape off layer * SOL turbulence * Landau damping * suprathermal electrons Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.307, year: 2016 http://iopscience.iop.org/article/10.1088/0029-5515/56/3/036004

Electronic energy spectra in antiferromagnetic media with broken reciprocity

International Nuclear Information System (INIS)

Vitebsky, I.; Edelkind, J.; Bogachek, E.N.; Scherbakov, A.G.; Landman, U.

1997-01-01

Electronic energy spectra var-epsilon(q) of antiferromagnetically ordered media may display nonreciprocity; that is, the energies corresponding to Bloch states with wave numbers q and -q may be different. In this paper a simple Kronig-Penney model, which includes a staggered microscopic magnetic and electric fields of the proper symmetry, is employed to estimate the magnitude of nonreciprocity effects in systems such as antiferromagnetically ordered crystals as well as periodical layered structures. copyright 1997 The American Physical Society

Development of a BaF2 scintillation spectrometer for evaluation of photon energy spectra in workplaces around nuclear facilities

International Nuclear Information System (INIS)

Urabe, Itsumasa; Yoshimoto, Taka-aki; Kobayashi, Katsuhei; Akiyoshi, Tsunekazu; Tsujimoto, Tadashi; Nakashima, Yoshiyuki; Oda, Keiji.

1997-01-01

A BaF 2 scintillation spectrometer has been constructed for the determination of photon energy spectra in workplaces around nuclear facilities. Energy absorption spectra by the BaF 2 detector were calculated with the EGS4 Monte Carlo code in the energy region from 0.1 to 100 MeV and a response matrix of the spectrometer was obtained from the energy absorption spectra, of which the energy resolutions were modified to fit to the experimental results. With the irradiation experiments using neutron-capture gamma rays and those from radioactive sources, it became clear that photon energy spectra can be evaluated within an error of about 10% in the energy region 0.1 MeV to a few tens of megaelectronvolts. (author)

Monte Carlo calculations of neutron and gamm-ray energy spectra for fusion-reactor shield design: comparison with experiment

International Nuclear Information System (INIS)

Santoro, R.T.; Barnes, J.M.

1983-08-01

Neutron and gamma-ray spectra resulting from the interactions of approx. 14-MeV neutrons in laminated slabs of stainless steel type-304 and borated polyethylene have been calculated using the Monte Carlo code MCNP. The calculated spectra are compared with measured data as a function of slab thickness and material composition and as a function of detector location behind the slabs. Comparisons of the differential energy spectra are made for neutrons with energies above 850 keV and for gamma rays with energies above 750 keV. The measured neutron spectra and those calculated using Monte Carlo methods agree within 5% to 50% depending on the slab thickness and composition and neutron energy. The agreement between the measured and calculated gamma-ray energy spectra is also within this range. The MCNP data are also in favorable agreement with attenuated data calculated previously by discrete ordinates transport methods and the Monte Carlo code SAM-CE

Quiet-time 0.04 - 2 MeV/nucleon Ions at 1 AU in Solar Cycles 23 and 24

Science.gov (United States)

Zeldovich, M. A.; Logachev, Y. I.; Kecskeméty, K.

2018-01-01

The fluxes of 3He, 4He, C, O, and Fe ions at low energies (about 0.04 - 2 MeV/nucleon) are studied during quiet periods in Solar Cycles (SC) 23 and 24 using data from the ULEIS/ACE instrument. In selecting quiet periods (the definition is given in Section 2.1), additional data from EPHIN/SOHO and EPAM/ACE were also used. The analysis of the ion energy spectra and their relative abundances shows that their behavior is governed by their first-ionization potential. Substantial differences in the ion energy spectra in two consecutive solar cycles are observed during the quiet periods selected. Quiet-time fluxes are divided into three distinct types according to the {˜} 80 - 320 keV/nucleon Fe/O ratio. Our results confirm the earlier observation that these types of suprathermal particles have different origins, that is, they represent different seed populations that are accelerated by different processes. Except for the solar activity minimum, the Fe/O ratio during quiet-time periods correspond either to the abundances of ions in particle fluxes accelerated in impulsive solar flares or to the mean abundances of elements in the solar corona. At the activity minimum, this ratio takes on values that are characteristic for the solar wind. These results indicate that the background fluxes of low-energy particles in the ascending, maximum, and decay phases of the solar cycle include significant contributions from both coronal particles accelerated to suprathermal energies and ions accelerated in small impulsive solar flares rich in Fe, while the contribution of remnants from earlier SEP events cannot be excluded. The comparison of suprathermal ion abundances during the first five years of SC 23 and SC 24 suggests that the quiet-time and non-quiet fluxes of Fe and 3He were lower in SC 24.

The high energy X-ray spectra of supernova remnants

Science.gov (United States)

Pravdo, S. H.; Nugent, J. J.

The results of fitting an ionization-nonequilibrium (INE) model to the high-energy (above 5-keV) X-ray spectra of the young supernova remnants Cas A and Tycho are presented. As an additional constraint, the models must simultaneously fit lower-energy, higher-resolution data. For Cas A, a single INE component cannot adequately reproduce the features for the entire X-ray spectrum because the ionization structure of iron ions responsible for the K emission is inconsistent with that of the ions responsible for the lower-energy lines, and the flux of the highest-energy X-rays is underestimated. The iron K line and the high-energy continuum could arise from the same INE component, but the identification of this component with either the blast wave or the ejecta in the standard model is difficult. In Tycho, the high-energy data rule out a class of models for the lower-energy data which have too large a continuum contribution.

Quasiparticle energies, excitons, and optical spectra of few-layer black phosphorus

International Nuclear Information System (INIS)

Tran, Vy; Fei, Ruixiang; Yang, Li

2015-01-01

We report first-principles GW–Bethe–Salpeter-equation (BSE) studies of excited-state properties of few-layer black phosphorus (BP) (phosphorene). With improved GW computational methods, we obtained converged quasiparticle band gaps and optical absorption spectra by the single-shot (G 0 W 0 ) procedure. Moreover, we reveal fine structures of anisotropic excitons, including the series of one-dimensional like wave functions, spin singlet–triplet splitting, and electron–hole binding energy spectra by solving BSE. An effective-mass model is employed to describe these electron–hole pairs, shedding light on estimating the exciton binding energy of anisotropic two-dimensional semiconductors without expensive ab initio simulations. Finally, the anisotropic optical response of BP is explained by using optical selection rules based on the projected single-particle density of states at band edges. (paper)

Stereo ENA Imaging of the Ring Current and Multi-point Measurements of Suprathermal Particles and Magnetic Fields by TRIO-CINEMA

Science.gov (United States)

Lin, R. P.; Sample, J. G.; Immel, T. J.; Lee, D.; Horbury, T. S.; Jin, H.; SEON, J.; Wang, L.; Roelof, E. C.; Lee, E.; Parks, G. K.; Vo, H.

2012-12-01

The TRIO (Triplet Ionospheric Observatory) - CINEMA (Cubesat for Ions, Neutrals, Electrons, & Magnetic fields) mission consists of three identical 3-u cubesats to provide high sensitivity, high cadence, stereo measurements of Energetic Neutral Atoms (ENAs) from the Earth's ring current with ~1 keV FWHM energy resolution from ~4 to ~200 keV, as well as multi-point in situ measurements of magnetic fields and suprathermal electrons (~2 -200 keV) and ions (~ 4 -200 keV) in the auroral and ring current precipitation regions in low Earth orbit (LEO). A new Suprathermal Electron, Ion, Neutral (STEIN) instrument, using a 32-pixel silicon semiconductor detector with an electrostatic deflection system to separate ENAs from ions and from electrons below 30 keV, will sweep over most of the sky every 15 s as the spacecraft spins at 4 rpm. In addition, inboard and outboard (on an extendable 1m boom) miniature magnetoresistive sensor magnetometers will provide high cadence 3-axis magnetic field measurements. An S-band transmitter will be used to provide ~8 kbps orbit-average data downlink to the ~11m diameter antenna of the Berkeley Ground Station.The first CINEMA (funded by NSF) is scheduled for launch on August 14, 2012 into a 65 deg. inclination LEO. Two more identical CINEMAs are being developed by Kyung Hee University (KHU) in Korea under the World Class University (WCU) program, for launch in November 2012 into a Sun-synchronous LEO to form TRIO-CINEMA. A fourth CINEMA is being developed for a 2013 launch into LEO. This LEO constellation of nanosatellites will provide unique measurements highly complementary to NASA's RBSP and THEMIS missions. Furthermore, CINEMA's development of miniature particle and magnetic field sensors, and cubesat-size spinning spacecraft may be important for future constellation space missions. Initial results from the first CINEMA will be presented if available.

Optimization and energy spectra of x-ray to be used for imaging

International Nuclear Information System (INIS)

Nakamori, Nobuyuki; Kanamori, Hitoshi

1979-01-01

The relations of the spectra of X-ray used for diagnosis to the absorbed dose of patients and X-ray information are now being investigated by a number of investigators. Here the problems and the trends of the investigations at present are described. Advent of semiconductor detectors has improved the accuracy of measuring X-ray spectra very rapidly. However, since the semiconductor detectors themselves utilize X-ray photon absorption, calibration curves must be prepared for obtaining the true X-ray spectra. Though there are methods of theoretically determining X-ray spectra, no definite theoretical formula is found. Thus, the derivation of an empirical equation based on measured data would be the most fundamental problem. Interactions in an object and the change of X-ray spectra are described on the case of monochromatic and continuous X-ray irradiation. As mentioned above, beam hardening occurs when X-ray enters a matter deep, because the interactions between X-ray and the matter depend upon the photon energy. There are a few methods for correcting the variation of CT (computed tomography) number due to beam hardening. However, prior to this, there are two methods of representing continuous X-ray with single energy, and the unification of the methods or a new way of defining X-ray quality is needed. It has been and is always desirable that monochromatic X-ray source becomes to be useable, and various methods are proposed. (Wakatsuki, Y.)

Proton and alpha evaporation spectra in low energy 12 C and 16 O ...

Indian Academy of Sciences (India)

The spectra are compared with the statistical model calculations. The shapes of the calculated spectra are in agreement with experimental data except for the alpha spectrum in the 12C+93Nb reaction at 40 MeV. The observed evaporation bump is at ∼ 2 MeV lower energy compared to the calculated one. This discrepancy ...

Proton and alpha evaporation spectra in low energy 12C and 16O ...

Indian Academy of Sciences (India)

75 MeV. The spectra are compared with the statistical model calculations. The shapes of the calculated spectra are in agreement with experimental data except for the alpha spectrum in the 12C+93Nb reaction at 40 MeV. The observed evaporation bump is at ~2. MeV lower energy compared to the calculated one.

Atmospheric proton and deuterium energy spectra determination with the MASS2 experiment

Energy Technology Data Exchange (ETDEWEB)

Grimani, C.; Brunetti, M.T.; Codino, A.; Finetti, N. [Perugia Univ. (Italy)]|[INFN, Perugia (Italy); Papini, P.; Massimo Brancaccio, F. [Florence Univ. (Italy)]|[INFN, Florence (Italy); Basini, G.; Bongiorno, F. [INFN, Laboratori Nazionali di Frascati, Rome (Italy); Golden, R.L. [New Mexico State Univ., Las Cruces, NM (United States). Particle Astrophysics Lab.; Hof, M. [Siegen Univ. (Germany). Fachbereich Physik

1995-09-01

The energy spectra of atmospheric-secondary protons and deuterium nuclei have been measured during the September 23, 1991, balloon flight of the NMSU/Wizard - MASS2 instrument. The apparatus was launched from Fort Sumner, New Mexico. The geomagnetic cutoff at the launch site is about 4.5 GV/c. The instrument was flown for 9.8 hours at an altitude of over 100,000 feet. Particles detected below the geomagnetic cutoff have been produced mainly by the interactions of the primary cosmic rays with the atmosphere. The measurement of cosmic ray energy spectra below the geomagnetic cutoff provide direct insights into the particle production mechanism and allows comparison to atmospheric cascade calculations.

Electron spectra resulting from autoionization in low-energy Li+ + He collisions

International Nuclear Information System (INIS)

Yagishita, A.; Wakiya, K.; Takayanagi, T.; Suzuki, H.; Koike, F.

1979-09-01

Spectra of electrons ejected from doubly excited states of helium have been extensively measured at several observation angles fro impact with lithium ions at energies lower than 5 KeV. ''Molecular-autoionization'' spectra have been found at forward observation angles, and analyzed in terms of the Gerber-Niehaus theory with modification. The spectral shapes of atomic-autoionization peaks have been discussed in relation to both the Barker-Berry effect and the Doppler effect. Excitation cross sections of autoionizing states have been determined by a new method that uses simultaneous impact of ions and electrons. (author)

FITPULS: a code for obtaining analytic fits to aggregate fission-product decay-energy spectra

International Nuclear Information System (INIS)

LaBauve, R.J.; George, D.C.; England, T.R.

1980-03-01

The operation and input to the FITPULS code, recently updated to utilize interactive graphics, are described. The code is designed to retrieve data from a library containing aggregate fine-group spectra (150 energy groups) from fission products, collapse the data to few groups (up to 25), and fit the resulting spectra along the cooling time axis with a linear combination of exponential functions. Also given in this report are useful results for aggregate gamma and beta spectra from the decay of fission products released from 235 U irradiated with a pulse (10 -4 s irradiation time) of thermal neutrons. These fits are given in 22 energy groups that are the first 22 groups of the LASL 25-group decay-energy group structure, and the data are expressed both as MeV per fission second and particles per fission second; these pulse functions are readily folded into finite fission histories. 65 figures, 11 tables

Effects of ionization and ion loss on dust ion- acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

Science.gov (United States)

Tribeche, Mouloud; Mayout, Saliha

2016-07-01

The combined effects of ionization, ion loss and electron suprathermality on dust ion- acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg- de Vries (dK-- dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK- dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the DIA solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

Low-energy photons in high-energy photon fields--Monte Carlo generated spectra and a new descriptive parameter.

Science.gov (United States)

Chofor, Ndimofor; Harder, Dietrich; Willborn, Kay; Rühmann, Antje; Poppe, Björn

2011-09-01

The varying low-energy contribution to the photon spectra at points within and around radiotherapy photon fields is associated with variations in the responses of non-water equivalent dosimeters and in the water-to-material dose conversion factors for tissues such as the red bone marrow. In addition, the presence of low-energy photons in the photon spectrum enhances the RBE in general and in particular for the induction of second malignancies. The present study discusses the general rules valid for the low-energy spectral component of radiotherapeutic photon beams at points within and in the periphery of the treatment field, taking as an example the Siemens Primus linear accelerator at 6 MV and 15 MV. The photon spectra at these points and their typical variations due to the target system, attenuation, single and multiple Compton scattering, are described by the Monte Carlo method, using the code BEAMnrc/EGSnrc. A survey of the role of low energy photons in the spectra within and around radiotherapy fields is presented. In addition to the spectra, some data compression has proven useful to support the overview of the behaviour of the low-energy component. A characteristic indicator of the presence of low-energy photons is the dose fraction attributable to photons with energies not exceeding 200 keV, termed P(D)(200 keV). Its values are calculated for different depths and lateral positions within a water phantom. For a pencil beam of 6 or 15 MV primary photons in water, the radial distribution of P(D)(200 keV) is bellshaped, with a wide-ranging exponential tail of half value 6 to 7 cm. The P(D)(200 keV) value obtained on the central axis of a photon field shows an approximately proportional increase with field size. Out-of-field P(D)(200 keV) values are up to an order of magnitude higher than on the central axis for the same irradiation depth. The 2D pattern of P(D)(200 keV) for a radiotherapy field visualizes the regions, e.g. at the field margin, where changes of

Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

International Nuclear Information System (INIS)

Goldston, R.J.; Towner, H.H.

1980-02-01

Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, beam ions become trapped in local magnetic wells near their banana tips due to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, near-perpendicular untrapped ions are captured (again near a banana tip) due to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced variable lingering period near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity α* identical with epsilon/sin theta/Nqdelta is of order unity or smaller

Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

International Nuclear Information System (INIS)

Goldston, R.J.; Towner, H.H.

1981-01-01

Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, ions become trapped in local magnetic wells near their banana tips owing to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, ions are captured (again near a banana tip) owing to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced 'variable lingering period' near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity α* is identical with epsilonsinthetaNqdelta is of order unity or smaller. (author)

Calculation of low-energy reactor neutrino spectra reactor for reactor neutrino experiments

Energy Technology Data Exchange (ETDEWEB)

Riyana, Eka Sapta; Suda, Shoya; Ishibashi, Kenji; Matsuura, Hideaki [Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Kyushu (Japan); Katakura, Junichi [Dept. of Nuclear System Safety Engineering, Nagaoka University of Technology, Nagaoka (Japan)

2016-06-15

Nuclear reactors produce a great number of antielectron neutrinos mainly from beta-decay chains of fission products. Such neutrinos have energies mostly in MeV range. We are interested in neutrinos in a region of keV, since they may take part in special weak interactions. We calculate reactor antineutrino spectra especially in the low energy region. In this work we present neutrino spectrum from a typical pressurized water reactor (PWR) reactor core. To calculate neutrino spectra, we need information about all generated nuclides that emit neutrinos. They are mainly fission fragments, reaction products and trans-uranium nuclides that undergo negative beta decay. Information in relation to trans-uranium nuclide compositions and its evolution in time (burn-up process) were provided by a reactor code MVP-BURN. We used typical PWR parameter input for MVP-BURN code and assumed the reactor to be operated continuously for 1 year (12 months) in a steady thermal power (3.4 GWth). The PWR has three fuel compositions of 2.0, 3.5 and 4.1 wt% {sup 235}U contents. For preliminary calculation we adopted a standard burn-up chain model provided by MVP-BURN. The chain model treated 21 heavy nuclides and 50 fission products. The MVB-BURN code utilized JENDL 3.3 as nuclear data library. We confirm that the antielectron neutrino flux in the low energy region increases with burn-up of nuclear fuel. The antielectron-neutrino spectrum in low energy region is influenced by beta emitter nuclides with low Q value in beta decay (e.g. {sup 241}Pu) which is influenced by burp-up level: Low energy antielectron-neutrino spectra or emission rates increase when beta emitters with low Q value in beta decay accumulate. Our result shows the flux of low energy reactor neutrinos increases with burn-up of nuclear fuel.

Interaction of supra-thermal ions with turbulence in a magnetized toroidal plasma

International Nuclear Information System (INIS)

Plyushchev, G.

2009-01-01

This thesis addresses the interaction of a supra-thermal ion beam with turbulence in the simple magnetized toroidal plasma of TORPEX. The first part of the Thesis deals with the ohmic assisted discharges on TORPEX. The aim of these discharges is the investigation of the open to closed magnetic field line transition. The relevant magnetic diagnostics were developed. Ohmic assisted discharges with a maximum plasma current up to 1 kA are routinely obtained. The equilibrium conditions on the vacuum magnetic field configuration were investigated. In the second part of the Thesis, the design of the fast ion source and detector are discussed. The accelerating electric field needed for the fast ion source was optimized. The fast ion source was constructed and commissioned. To detect the fast ions a specially designed gridded energy analyzer was used. The electron energy distribution function was obtained to demonstrate the efficiency of the detector. The experiments with the fast ion beam were conducted in different plasma regions of TORPEX. In the third part of the Thesis, numerical simulations are used to interpret the measured fast ion beam behavior. It is shown that a simple single particle equation of motion explains the beam behavior in the experiments in the absence of plasma. To explain the fast ion beam experiments with the plasma a turbulent electric field must be used. The model that takes into account this turbulent electrical field qualitatively explains the shape of the fast ion current density profile in the different plasma regions of TORPEX. The vertically elongated fast ion current density profiles are explained by a spread in the fast ion velocity distribution. The theoretically predicted radial fast ion beam spreading due to the turbulent electric field was observed in the experiment. (author)

SUPRATHERMAL ELECTRON STRAHL WIDTHS IN THE PRESENCE OF NARROW-BAND WHISTLER WAVES IN THE SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Kajdič, P. [Instituto de Geofísica, Universidad Nacional Autónoma de México, Mexico City (Mexico); Alexandrova, O.; Maksimovic, M.; Lacombe, C. [LESIA, Observatoire de Paris, PSL Research University, CNRS, UPMC UniversitéParis 06, Université Paris-Diderot, 5 Place Jules Janssen, F-92190 Meudon (France); Fazakerley, A. N., E-mail: primoz@geofisica.unam.mx [Mullard Space Science Laboratory, University College London (United Kingdom)

2016-12-20

We perform the first statistical study of the effects of the interaction of suprathermal electrons with narrow-band whistler mode waves in the solar wind (SW). We show that this interaction does occur and that it is associated with enhanced widths of the so-called strahl component. The latter is directed along the interplanetary magnetic field away from the Sun. We do the study by comparing the strahl pitch angle widths in the SW at 1 AU in the absence of large scale discontinuities and transient structures, such as interplanetary shocks, interplanetary coronal mass ejections, stream interaction regions, etc. during times when the whistler mode waves were present and when they were absent. This is done by using the data from two Cluster instruments: Spatio Temporal Analysis of Field Fluctuations experiment (STAFF) data in the frequency range between ∼0.1 and ∼200 Hz were used for determining the wave properties and Plasma Electron And Current Experiment (PEACE) data sets at 12 central energies between ∼57 eV (equivalent to ∼10 typical electron thermal energies in the SW, E{sub T}) and ∼676 eV (∼113 E{sub T}) for pitch angle measurements. Statistical analysis shows that, during the intervals with the whistler waves, the strahl component on average exhibits pitch angle widths between 2° and 12° larger than during the intervals when these waves are not present. The largest difference is obtained for the electron central energy of ∼344 eV (∼57 ET).

SUPRATHERMAL ELECTRON STRAHL WIDTHS IN THE PRESENCE OF NARROW-BAND WHISTLER WAVES IN THE SOLAR WIND

International Nuclear Information System (INIS)

Kajdič, P.; Alexandrova, O.; Maksimovic, M.; Lacombe, C.; Fazakerley, A. N.

2016-01-01

We perform the first statistical study of the effects of the interaction of suprathermal electrons with narrow-band whistler mode waves in the solar wind (SW). We show that this interaction does occur and that it is associated with enhanced widths of the so-called strahl component. The latter is directed along the interplanetary magnetic field away from the Sun. We do the study by comparing the strahl pitch angle widths in the SW at 1 AU in the absence of large scale discontinuities and transient structures, such as interplanetary shocks, interplanetary coronal mass ejections, stream interaction regions, etc. during times when the whistler mode waves were present and when they were absent. This is done by using the data from two Cluster instruments: Spatio Temporal Analysis of Field Fluctuations experiment (STAFF) data in the frequency range between ∼0.1 and ∼200 Hz were used for determining the wave properties and Plasma Electron And Current Experiment (PEACE) data sets at 12 central energies between ∼57 eV (equivalent to ∼10 typical electron thermal energies in the SW, E T ) and ∼676 eV (∼113 E T ) for pitch angle measurements. Statistical analysis shows that, during the intervals with the whistler waves, the strahl component on average exhibits pitch angle widths between 2° and 12° larger than during the intervals when these waves are not present. The largest difference is obtained for the electron central energy of ∼344 eV (∼57 ET).

The energy spectra of anomalous oxygen at the time of two successive solar minima

CERN Document Server

Kondratyeva, M A; Tretyakova, S P; Zhuravlev, D A

1999-01-01

The energy spectra of anomalous oxygen have been determined from nuclear track detectors exposed aboard the Earth-orbiting satellites at altitudes ranging from approx 250-400 km in two consecutive solar minimum periods of 1986-1987 and 1994-1995 with opposite polarity of the solar magnetic field. A comparison of the spectra shows no contradiction to current drift models.

Measurement and analysis of leakage neutron energy spectra around the Kinki University Reactor, UTR-KINKI

CERN Document Server

Ogawa, Y; Sagawa, H; Tsujimoto, T

2002-01-01

The highly sensitive cylindrical multi-moderator type neutron spectrometer was constructed for measurement of low level environmental neutrons. This neutron spectrometer was applied for the determination of leakage neutron energy spectra around the Kinki University Reactor. The analysis of the leakage neutron energy spectra was performed by MCNP Monte Carlo code. From the obtained results, the agreement between the MCNP predictions and the experimentally determined values is fairly good, which indicates the MCNP model is correctly simulating the UTR-KINKI.

Estimation of the sea level muon spectra at different zenith angles below 10 TeV energy

CERN Document Server

Mitra, M; Pal, P B; Bhattacharya, D P

2001-01-01

The moderate energy primary cosmic ray nucleon spectrum has been calculated from the direct measurements of Webber et al. (1987), Seo et al. (1992) and Menn et al. (1997). Along with the other results surveyed by Swordy (1993). Using these directly measured primary mass composition results all particle primary nucleon energy spectrum has been constructed using superposition model to estimate the energy spectra of muons from the decay of the cosmic ray non-prompt and prompt mesons in the atmosphere. The Z-factors have been estimated from the CERN LEBC-EHS on the Lorentz invariant cross section results on pp to pi /sup +or-/X and pp to K/sup +or-/X inclusive reactions and FNAL data on pi /sup +or-/p to pi /sup +or-/X reactions, and duly corrected for A-A collisions. Using these Z-factors the meson energy spectra in the atmosphere have been calculated. The sea level muon energy spectra at zenith angles 0 degrees , 45 degrees , 72 degrees , and 75 degrees have been derived from the decay of non-prompt mesons by a...

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation.

Science.gov (United States)

Moix, Jeremy M; Ma, Jian; Cao, Jianshu

2015-03-07

A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters.

Measurement of crosstalk contamination in dual isotope imaging by means of energy spectra and images

International Nuclear Information System (INIS)

Kojima, Akihiro; Tsuji, Akinori; Ohyama, Yoichi; Nabeshima, Mitsuko; Kira, Tomohiro; Nakashima, Rumi; Tomiguchi, Seiji; Takahashi, Mutsumasa; Matsumoto, Masanori.

1994-01-01

The purpose of this study was to estimate the value of crosstalk contamination ratio (CTR) by analyzing energy spectra and scintigraphic images using a phantom and three radionuclides of 201 Tl, 99m Tc and 123 I. A 2 cm x 2 cm plate source filled with single radionuclide was placed in a water tank and its depth changed from 0 cm to 10 cm. Energy spectra and planar images were obtained using a gamma camera with either a low-energy (150 keV) or a medium-energy (200 keV) collimator. The value of CTR was calculated for two combinations : 1) 201 Tl and 99m Tc and 2) 201 Tl and 123 I. The energy window width at a photopeak was 20% for each radionuclide. The data were analyzed in two regions: a region where primary photons were mainly included in (region 1, 2 cm x 2 cm) and a region where both primary and scattered photons were included in (region 2, 10 cm x 10 cm). The results from analyses of the images showed that the CTR of Tl/Tc and Tl/I (0.064-0.101) were almost equal to those of Tc/Tl and I/Tl (0.056-0.148) for the region 1, but the CTR of Tl/Tc and Tl/I (0.212-0.381) were 2 times greater than those of Tc/Tl and I/Tl (0.092-0.172) for the region 2. Furthermore, these results showed good agreement between the CTR by energy spectra and those by images. For imaging with 123 I the medium-energy collimator had less blur than the low-energy collimator, in particular for the smaller source-to-collimator distance. In conclusion, the crosstalk contamination in dual-isotope study affects quantification of two radionuclides' activities. Our results are useful to evaluate images acquired using the dual-isotope technique and develop a new correction method for such crosstalk contamination by analyzing the energy spectra and images obtained. (author)

Comparison of species-resolved energy spectra from ACE EPAM and Van Allen Probes RBSPICE

Science.gov (United States)

Patterson, J.; Manweiler, J. W.; Armstrong, T. P.; Lanzerotti, L. J.; Gerrard, A. J.; Gkioulidou, M.

2013-12-01

We present a comparison between energy spectra measured by the Advanced Composition Explorer (ACE) Electron Proton Alpha Monitor (EPAM) instrument and the Van Allen Probe Ion Composition Experiment (RBSPICE) for two significant and distinct events in early 2013. The first is an impulsive solar particle event on March 17th. While intense, this event presented no significant surprises in terms of its composition or anisotropy characteristics, thus providing a good baseline for response of the trapped radiation belts as observed by the Van Allen Probes. The second solar event occurred late May 22nd and early May 23rd. This event has a much greater concentration of medium and heavy ions than the St. Patrick's Day event, as well as having very peculiar energy spectra with evidence of two distinct populations. During the St. Patrick's Day Event, the energy spectra for helium, carbon, oxygen, neon, silicon, and iron all show the same spectral power law slope -3.1. The event shows strong anisotropy with intensities differing by a factor of four for both protons and Z>1 ions. The late May event also has strong anisotropy, and in the same directions as the St. Patrick's Day Event, but with very different composition and energy spectra. The spectra are much harder with power law spectral slopes of -0.5. Additionally, there is a significant spectral bump at 3 MeV/nuc for helium that is not present in the spectra of the heavier ions. The intensities of the heavier ions, however, show an increase that is an order of magnitude greater than the increase seen for helium. The March 17 RBSPICE observations show multiple injection events lasting for less than an hour each during the Van Allen Probes B apogees. These injections are seen in protons as well as Helium and only somewhat observed in Oxygen. Spectral slopes for the observations range from approximately -5 during quiet times to double peaked events with a spectral slope of approximately -2 at the beginning of the injection

Effects of ionization and ion loss on dust ion-acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

Energy Technology Data Exchange (ETDEWEB)

Mayout, Saliha; Gougam, Leila Ait [Faculty of Physics, Theoretical Physics Laboratory, Plasma Physics Group, University of Bab-Ezzouar, USTHB, B.P. 32, El Alia, Algiers 16111 (Algeria); Tribeche, Mouloud, E-mail: mouloudtribeche@yahoo.fr, E-mail: mtribeche@usthb.dz [Faculty of Physics, Theoretical Physics Laboratory, Plasma Physics Group, University of Bab-Ezzouar, USTHB, B.P. 32, El Alia, Algiers 16111 (Algeria); Algerian Academy of Sciences and Technologies, Algiers (Algeria)

2016-03-15

The combined effects of ionization, ion loss, and electron suprathermality on dust ion-acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg-de Vries (dK–dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK-dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the dust ion-acoustic solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

Effects of ionization and ion loss on dust ion-acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

International Nuclear Information System (INIS)

Mayout, Saliha; Gougam, Leila Ait; Tribeche, Mouloud

2016-01-01

The combined effects of ionization, ion loss, and electron suprathermality on dust ion-acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg-de Vries (dK–dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK-dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the dust ion-acoustic solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

Energy-loss of He ions in carbon allotropes studied by elastic resonance in backscattering spectra

Energy Technology Data Exchange (ETDEWEB)

Tosaki, Mitsuo, E-mail: tosaki.mitsuo.3v@kyoto-u.ac.jp [Radioisotope Research Center, Kyoto University, Kyoto 606-8501 (Japan); Rauhala, Eero [Department of Physics, University of Helsinki (Finland)

2015-10-01

Backscattering spectra for {sup 4}He ions incident on carbon allotropes have been measured in the energy range from 4.30 to 4.95 MeV in steps of 50–100 keV at scattering angles of 106° and 170°. We used three carbon allotropes: graphite, diamond and amorphous carbon. For all these allotropes, we can observe the sharp ({sup 4}He, {sup 12}C) elastic nuclear resonance at the He ion energy of 4.265 MeV in the backscattering spectra. By varying the incident He energy, we have systematically analyzed the profiles of the resonance peaks to study the energy-loss processes: stopping cross-sections and energy-loss straggling around the interesting region of the stopping maximum at about 500 keV. We focus on the resonance profiles and investigate an allotropic effect concerning the energy-loss. Furthermore, an energy bunching effect on the straggling is presented and the mechanism is discussed.

High-energy kink in the single-particle spectra of cuprates

International Nuclear Information System (INIS)

Cojocaru, S.; Citro, R.; Marinaro, M.

2008-01-01

Within a phenomenological model where electrons are coupled to a bosonic mode in a generic form of damped oscillator, we analyze the high-energy kink recently observed in ARPES experiments on cuprates. It is shown that the model allows to describe the main anomalous features found in experiments, such as the broad incoherent spectral weight, the 'waterfall dispersion', its doping and temperature dependence. In contrast to the low-energy kink, presence of significant damping is required to account for the anomalies. The 'bosonic mode' is related to the incoherent excitation peak observed in optical conductivity spectra of cuprates

High-energy kink in the single-particle spectra of cuprates

Energy Technology Data Exchange (ETDEWEB)

Cojocaru, S. [Dipartimento di Fisica ' E. R. Caianiello' and C.N.I.S.M., Universita degli Studi di Salerno, Via S. Allende, I-84081 Baronissi (Italy); Institute of Applied Physics, Chisinau 2028 (Moldova, Republic of); Citro, R. [Dipartimento di Fisica ' E. R. Caianiello' and C.N.I.S.M., Universita degli Studi di Salerno, Via S. Allende, I-84081 Baronissi (Italy)], E-mail: citro@sa.infn.it; Marinaro, M. [Dipartimento di Fisica ' E. R. Caianiello' and C.N.I.S.M., Universita degli Studi di Salerno, Via S. Allende, I-84081 Baronissi (Italy); I.I.A.S.S., Via G. Pellegrino, n. 19 84019 Vietri sul Mare (Italy)

2008-04-01

Within a phenomenological model where electrons are coupled to a bosonic mode in a generic form of damped oscillator, we analyze the high-energy kink recently observed in ARPES experiments on cuprates. It is shown that the model allows to describe the main anomalous features found in experiments, such as the broad incoherent spectral weight, the 'waterfall dispersion', its doping and temperature dependence. In contrast to the low-energy kink, presence of significant damping is required to account for the anomalies. The 'bosonic mode' is related to the incoherent excitation peak observed in optical conductivity spectra of cuprates.

Inclusive spectra of mesons with large transverse momenta in proton-nuclear collisions at high energies

International Nuclear Information System (INIS)

Lykasov, G.I.; Sherkhonov, B.Kh.

1982-01-01

Basing on the proposed earlier quark model of hadron-nucleus processes with large transverse momenta psub(perpendicular) the spectra of π +- , K +- meson production with large psub(perpendicular) in proton-nucleus collisions at high energies are calculated. The performed comparison of their dependence of the nucleus-target atomic number A with experimental data shows a good agreement. Theoretical and experimental ratios of inclusive spectra of K +- and π +- mesons in the are compared. Results of calculations show a rather good description of experimental data on large psub(perpendicular) meson production at high energies

Simulation of the energy spectra of original versus recombined H2+ molecular ions transmitted through thin foils

International Nuclear Information System (INIS)

Barriga-Carrasco, Manuel D.; Garcia-Molina, Rafael

2004-01-01

This work presents the results of computer simulations for the energy spectra of original versus recombined H 2 + molecular ions transmitted through thin amorphous carbon foils, for a broad range of incident energies. A detailed description of the projectile motion through the target has been done, including nuclear scattering and Coulomb repulsion as well as electronic self-retarding and wake forces; the two latter are calculated in the dielectric formalism framework. Differences in the energy spectra of recombined and original transmitted H 2 + molecular ions clearly appear in the simulations, in agreement with the available experimental data. Our simulation code also differentiates the contributions due to original and to recombined H 2 + molecular ions when the energy spectra contain both contributions, a feature that could be used for experimental purposes in estimating the ratio between the number of original and recombined H 2 + molecular ions transmitted through thin foils

Measurements of energy spectra of fast electrons from PF-1000 in the upstream and downstream directions

Energy Technology Data Exchange (ETDEWEB)

Kwiatkowski, R.; Czaus, K.; Skladnik-Sadowska, E.; Malinowski, K.; Zebrowski, J. [The Andrzej Soltan Institute for Nuclear Studies (IPJ), 05-400 Otwock-Swierk (Poland); Sadowski, M.J. [The Andrzej Soltan Institute for Nuclear Studies (IPJ), 05-400 Otwock-Swierk (Poland); Karpinski, L.; Paduch, M.; Scholz, M. [Institute of Plasma Physics and Laser Microfusion (IPPLM), 01-497 Warsaw (Poland); Kubes, P. [Czech Technical University (CVUT), 166-27 Prague, (Czech Republic)

2011-07-01

The paper describes measurements of energy spectra of electrons emitted in the upstream direction along the symmetry-axis of the PF-1000 facility, operated with the deuterium filling at 21 kV, 290 kJ. The measurements were performed with a magnetic analyzer. The same analyzer was used to measure also electron beams emitted in along the symmetry-axis in the downstream direction. The recorded spectra showed that the electron-beams emitted in the upstream direction have energies in the range from about 40 keV to about 800 keV, while those in the downstream direction have energies in the range from about 60 keV to about 200 keV. These spectra confirm that in the PF (Plasma Focus) plasma column there appear strong local fields accelerating charged particles in different directions. This document is composed of a paper and a poster. (authors)

Numerical calculation of 'actual' radial profile of ion temperature from 'measured' energy spectra of charge-exchanged neutrals

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Kazuo; Hiraki, Naoji; Toi, Kazuo; Itoh, Satoshi

1984-10-01

The energy spectra of charge-exchanged neutrals are observed in the TRIAM-1 tokamak by vertical scanning of the neutral energy analyzer. The ''apparent'' ion temperature obtained directly from the energy spectrum observed in the peripheral region is much higher than that predicted by neoclassical transport theory. The ''actual'' ion temperature profile is derived numerically from the energy spectra observed at various positions taking into account the wall-reflection effect of neutrals and the impermeability of the plasma. As a result, the ''actual'' ion temperature profile is found to agree well with that predicted by neoclassical transport theory.

Numerical calculation of 'actual' radial profile of ion temperature from 'measured' energy spectra of charge-exchanged neutrals

International Nuclear Information System (INIS)

Nakamura, Kazuo; Hiraki, Naoji; Toi, Kazuo; Itoh, Satoshi

1984-01-01

The energy spectra of charge-exchanged neutrals are observed in the TRIAM-1 tokamak by vertical scanning of the neutral energy analyzer. The ''apparent'' ion temperature obtained directly from the energy spectrum observed in the peripheral region is much higher than that predicted by neoclassical transport theory. The ''actual'' ion temperature profile is derived numerically from the energy spectra observed at various positions taking into account the wall-reflection effect of neutrals and the impermeability of the plasma. As a result, the ''actual'' ion temperature profile is found to agree well with that predicted by neoclassical transport theory. (author)

Solar Energetic Particle Spectra

Science.gov (United States)

Ryan, J. M.; Boezio, M.; Bravar, U.; Bruno, A.; Christian, E. R.; de Nolfo, G. A.; Martucci, M.; Mergè, M.; Munini, R.; Ricci, M.; Sparvoli, R.; Stochaj, S.

2017-12-01

We report updated event-integrated spectra from several SEP events measured with PAMELA. The measurements were made from 2006 to 2014 in the energy range starting at 80 MeV and extending well above the neutron monitor threshold. The PAMELA instrument is in a high inclination, low Earth orbit and has access to SEPs when at high latitudes. Spectra have been assembled from these high-latitude measurements. The field of view of PAMELA is small and during the high-latitude passes it scans a wide range of asymptotic directions as the spacecraft orbits. Correcting for data gaps, solid angle effects and improved background corrections, we have compiled event-integrated intensity spectra for twenty-eight SEP events. Where statistics permit, the spectra exhibit power law shapes in energy with a high-energy exponential roll over. The events analyzed include two genuine ground level enhancements (GLE). In those cases the roll-over energy lies above the neutron monitor threshold ( 1 GV) while the others are lower. We see no qualitative difference between the spectra of GLE vs. non-GLE events, i.e., all roll over in an exponential fashion with rapidly decreasing intensity at high energies.

Studies of cluster X-ray sources. Energy spectra for the Perseus, Virgo, and Coma clusters

International Nuclear Information System (INIS)

Kellogg, E.; Baldwin, J.R.; Koch, D.

1975-01-01

We present the final Uhuru X-ray differential-energy spectra for the Perseus, Virgo, and Coma clusters of galaxies. The power-law and isothermal bremsstrahlung model forms, both with a low-energy cutoff, are given. For bremsstrahlung, the energy-dependent Gaunt factor is calculated by an improved method. The spectra, best fits to the Uhuru 2-10 keV data, are also compared with other observations of these sources in the energy range 0.1-100 keV. For Perseus, the data above 20 keV favor the bremsstrahlung fit marginally. For Virgo, the data of Catura et al. between 0.25 and 1.0 keV clearly favor the bremsstrahlung curve. For Coma, the weakest of the three sources, the data are less precise, but there is some evidence for a low-energy turnover or cutoff. The implications of such a cutoff are discussed briefly

Suprathermal electron production in laser-irradiated Cu targets characterized by combined methods of x-ray imaging and spectroscopy

Czech Academy of Sciences Publication Activity Database

Renner, Oldřich; Šmíd, Michal; Batani, D.; Antonelli, L.

2016-01-01

Roč. 58, č. 7 (2016), 1-8, č. článku 075007. ISSN 0741-3335 R&D Projects: GA MŠk LQ1606; GA MŠk EF15_008/0000162; GA MŠk(CZ) LD14089 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : laser- plasma interaction * inertial confinement fusion * suprathermal electron Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.392, year: 2016

A physical mechanism producing suprathermal populations and initiating substorms in the Earth's magnetotail

Directory of Open Access Journals (Sweden)

D. V. Sarafopoulos

2008-06-01

Full Text Available We suggest a candidate physical mechanism, combining there dimensional structure and temporal development, which is potentially able to produce suprathermal populations and cross-tail current disruptions in the Earth's plasma sheet. At the core of the proposed process is the "akis" structure; in a thin current sheet (TCS the stretched (tail-like magnetic field lines locally terminate into a sharp tip around the tail midplane. At this sharp tip of the TCS, ions become non-adiabatic, while a percentage of electrons are accumulated and trapped: The strong and transient electrostatic electric fields established along the magnetic field lines produce suprathermal populations. In parallel, the tip structure is associated with field aligned and mutually attracted parallel filamentary currents which progressively become more intense and inevitably the structure collapses, and so does the local TCS. The mechanism is observationally based on elementary, almost autonomous and spatiotemporal entities that correspond each to a local thinning/dipolarization pair having duration of ~1 min. Energetic proton and electron populations do not occur simultaneously, and we infer that they are separately accelerated at local thinnings and dipolarizations, respectively. In one example energetic particles are accelerated without any dB/dt variation and before the substorm expansion phase onset. A particular effort is undertaken demonstrating that the proposed acceleration mechanism may explain the plasma sheet ratio Ti/Te≈7. All our inferences are checked by the highest resolution datasets obtained by the Geotail Energetic Particles and Ion Composition (EPIC instrument. The energetic particles are used as the best diagnostics for the accelerating source. Near Earth (X≈10 RE selected events support our basic concept. The proposed mechanism seems to reveal a fundamental building block of the substorm phenomenon and may be the basic process/structure, which is now

Characteristic electron energy loss spectra in SiC buried layers formed by C+ implantation into crystalline silicon

International Nuclear Information System (INIS)

Yan Hui; Chen Guanghua; Kwok, R.W.M.

1998-01-01

SiC buried layers were synthesized by a metal vapor vacuum arc ion source, with C + ions implanted into crystalline Si substrates. According to X-ray photoelectron spectroscopy, the characteristic electron energy loss spectra of the SiC buried layers were studied. It was found that the characteristic electron energy loss spectra depend on the profiles of the carbon content, and correlate well with the order of the buried layers

Electronic energy transfer through non-adiabatic vibrational-electronic resonance. II. 1D spectra for a dimer

Science.gov (United States)

Tiwari, Vivek; Jonas, David M.

2018-02-01

Vibrational-electronic resonance in photosynthetic pigment-protein complexes invalidates Förster's adiabatic framework for interpreting spectra and energy transfer, thus complicating determination of how the surrounding protein affects pigment properties. This paper considers the combined effects of vibrational-electronic resonance and inhomogeneous variations in the electronic excitation energies of pigments at different sites on absorption, emission, circular dichroism, and hole-burning spectra for a non-degenerate homodimer. The non-degenerate homodimer has identical pigments in different sites that generate differences in electronic energies, with parameters loosely based on bacteriochlorophyll a pigments in the Fenna-Matthews-Olson antenna protein. To explain the intensity borrowing, the excited state vibrational-electronic eigenvectors are discussed in terms of the vibrational basis localized on the individual pigments, as well as the correlated/anti-correlated vibrational basis delocalized over both pigments. Compared to those in the isolated pigment, vibrational satellites for the correlated vibration have the same frequency and precisely a factor of 2 intensity reduction through vibrational delocalization in both absorption and emission. Vibrational satellites for anti-correlated vibrations have their relaxed emission intensity reduced by over a factor 2 through vibrational and excitonic delocalization. In absorption, anti-correlated vibrational satellites borrow excitonic intensity but can be broadened away by the combination of vibronic resonance and site inhomogeneity; in parallel, their vibronically resonant excitonic partners are also broadened away. These considerations are consistent with photosynthetic antenna hole-burning spectra, where sharp vibrational and excitonic satellites are absent. Vibrational-excitonic resonance barely alters the inhomogeneously broadened linear absorption, emission, and circular dichroism spectra from those for a

Constrained energy minimization applied to apparent reflectance and single-scattering albedo spectra: a comparison

Science.gov (United States)

Resmini, Ronald G.; Graver, William R.; Kappus, Mary E.; Anderson, Mark E.

1996-11-01

Constrained energy minimization (CEM) has been applied to the mapping of the quantitative areal distribution of the mineral alunite in an approximately 1.8 km2 area of the Cuprite mining district, Nevada. CEM is a powerful technique for rapid quantitative mineral mapping which requires only the spectrum of the mineral to be mapped. A priori knowledge of background spectral signatures is not required. Our investigation applies CEM to calibrated radiance data converted to apparent reflectance (AR) and to single scattering albedo (SSA) spectra. The radiance data were acquired by the 210 channel, 0.4 micrometers to 2.5 micrometers airborne Hyperspectral Digital Imagery Collection Experiment sensor. CEM applied to AR spectra assumes linear mixing of the spectra of the materials exposed at the surface. This assumption is likely invalid as surface materials, which are often mixtures of particulates of different substances, are more properly modeled as intimate mixtures and thus spectral mixing analyses must take account of nonlinear effects. One technique for approximating nonlinear mixing requires the conversion of AR spectra to SSA spectra. The results of CEM applied to SSA spectra are compared to those of CEM applied to AR spectra. The occurrence of alunite is similar though not identical to mineral maps produced with both the SSA and AR spectra. Alunite is slightly more widespread based on processing with the SSA spectra. Further, fractional abundances derived from the SSA spectra are, in general, higher than those derived from AR spectra. Implications for the interpretation of quantitative mineral mapping with hyperspectral remote sensing data are discussed.

Dynamical and many-body correlation effects in the kinetic energy spectra of isotopes produced in nuclear multifragmentation

Science.gov (United States)

Souza, S. R.; Donangelo, R.; Lynch, W. G.; Tsang, M. B.

2018-03-01

The properties of the kinetic energy spectra of light isotopes produced in the breakup of a nuclear source and during the de-excitation of its products are examined. The initial stage, at which the hot fragments are created, is modeled by the statistical multifragmentation model, whereas the Weisskopf-Ewing evaporation treatment is adopted to describe the subsequent fragment de-excitation, as they follow their classical trajectories dictated by the Coulomb repulsion among them. The energy spectra obtained are compared to available experimental data. The influence of the fusion cross section entering into the evaporation treatment is investigated and its influence on the qualitative aspects of the energy spectra turns out to be small. Although these aspects can be fairly well described by the model, the underlying physics associated with the quantitative discrepancies remains to be understood.

Energy spectra of vibron and cluster models in molecular and nuclear systems

Science.gov (United States)

Jalili Majarshin, A.; Sabri, H.; Jafarizadeh, M. A.

2018-03-01

The relation of the algebraic cluster model, i.e., of the vibron model and its extension, to the collective structure, is discussed. In the first section of the paper, we study the energy spectra of vibron model, for diatomic molecule then we derive the rotation-vibration spectrum of 2α, 3α and 4α configuration in the low-lying spectrum of 8Be, 12C and 16O nuclei. All vibrational and rotational states with ground and excited A, E and F states appear to have been observed, moreover the transitional descriptions of the vibron model and α-cluster model were considered by using an infinite-dimensional algebraic method based on the affine \\widehat{SU(1,1)} Lie algebra. The calculated energy spectra are compared with experimental data. Applications to the rotation-vibration spectrum for the diatomic molecule and many-body nuclear clusters indicate that there are solvable models and they can be approximated very well using the transitional theory.

Proton energy spectra during ground level enhancements as measured by EPHIN aboard SOHO

Energy Technology Data Exchange (ETDEWEB)

Heber, Bernd; Kuehl, Patrick; Klassen, Andreas; Dresing, Nina [Christian-Albrechts-Universitaet zu Kiel, 24118 Kiel (Germany); Gomez-Herrero, Raul [Universidad de Alcala (Spain)

2016-07-01

Ground Level Enhancements (GLEs) are solar energetic particle (SEP) events that are recorded by ground-based instrumentation. The energy of the particles is so high that they produce secondary particles in the Earth's atmosphere, i.e. protons and neutrons, which are detected as sudden increases in cosmic ray intensities measured by e.g. neutron monitors. Since the launch of SOHO in December 1995 the neutron monitor network recorded 16 GLEs. The Electron Proton Helium INstrument on board SOHO has been designed to measure protons and helium up to 53 MeV/nucleon as well as electrons up to 8.3 MeV. Above these energies, particles penetrate all detector elements and thus, a separation between different particle species becomes more complicated. Recently we developed a method that allows deriving the energy spectrum for penetrating protons up to more than 1 GeV. In this contribution we present the proton energy spectra and time profiles of above mentioned GLEs and compare them to previous measurements. Although there are differences of up to a factor two the overall shape of the energy spectra agree surprisingly well. Thus it has been demonstrated that EPHIN measurements are a valuable tool for understanding GLE.

BETA SPECTRA. I. Negatrons spectra; ESPECTROS BETA. I. Espectros simples de negatrones

Energy Technology Data Exchange (ETDEWEB)

Grau Malonda, A; Garcia-Torano, E

1978-07-01

Using the Fermi theory of beta decay, the beta spectra for 62 negatrons emitters have been computed introducing a correction factor for unique forbidden transitions. These spectra are plotted vs. energy, once normal i sed, and tabulated with the related Fermi functions. The average and median energies are calculated. (Author)

Energy spectra and wave function of trigonometric Rosen-Morse potential as an effective quantum chromodynamics potential in D-dimensions

Energy Technology Data Exchange (ETDEWEB)

Deta, U. A., E-mail: utamaalan@yahoo.co.id [Theoretical Physics Group, Physics Department of Post Graduate Program, Sebelas Maret University, Jl. Ir. Sutami 36A, Surakarta 57126, Indonesia and Physics Department, State University of Surabaya, Jl. Ketintang, Surabaya 60231 (Indonesia); Suparmi,; Cari,; Husein, A. S.; Yuliani, H.; Khaled, I. K. A.; Luqman, H.; Supriyanto [Theoretical Physics Group, Physics Department of Post Graduate Program, Sebelas Maret University, Jl. Ir. Sutami 36A, Surakarta 57126 (Indonesia)

2014-09-30

The Energy Spectra and Wave Function of Schrodinger equation in D-Dimensions for trigonometric Rosen-Morse potential were investigated analytically using Nikiforov-Uvarov method. This potential captures the essential traits of the quark-gluon dynamics of Quantum Chromodynamics. The approximate energy spectra are given in the close form and the corresponding approximate wave function for arbitrary l-state (l ≠ 0) in D-dimensions are formulated in the form of differential polynomials. The wave function of this potential unnormalizable for general case. The wave function of this potential unnormalizable for general case. The existence of extra dimensions (centrifugal factor) and this potential increase the energy spectra of system.

Modelling of non-thermal electron cyclotron emission during ECRH

International Nuclear Information System (INIS)

Tribaldos, V.; Krivenski, V.

1990-01-01

The existence of suprathermal electrons during Electron Cyclotron Resonance Heating experiments in tokamaks is today a well established fact. At low densities the creation of large non-thermal electron tails affects the temperature profile measurements obtained by 2 nd harmonic, X-mode, low-field side, electron cyclotron emission. At higher densities suprathermal electrons can be detected by high-field side emission. In electron cyclotron current drive experiments a high energy suprathermal tail, asymmetric in v, is observed. Non-Maxwellian electron distribution functions are also typically observed during lower-hybrid current drive experiments. Fast electrons have been observed during ionic heating by neutral beams as well. Two distinct approaches are currently used in the interpretation of the experimental results: simple analytical models which reproduce some of the expected non-Maxwellian characteristics of the electron distribution function are employed to get a qualitative picture of the phenomena; sophisticated numerical Fokker-Planck calculations give the electron distribution function from which the emission spectra are computed. No algorithm is known to solve the inverse problem, i.e. to compute the electron distribution function from the emitted spectra. The proposed methods all relay on the basic assumption that the electron distribution function has a given functional dependence on a limited number of free parameters, which are then 'measured' by best fitting the experimental results. Here we discuss the legitimacy of this procedure. (author) 7 refs., 5 figs

Study of optical and electronic properties of nickel from reflection electron energy loss spectra

Science.gov (United States)

Xu, H.; Yang, L. H.; Da, B.; Tóth, J.; Tőkési, K.; Ding, Z. J.

2017-09-01

We use the classical Monte Carlo transport model of electrons moving near the surface and inside solids to reproduce the measured reflection electron energy-loss spectroscopy (REELS) spectra. With the combination of the classical transport model and the Markov chain Monte Carlo (MCMC) sampling of oscillator parameters the so-called reverse Monte Carlo (RMC) method was developed, and used to obtain optical constants of Ni in this work. A systematic study of the electronic and optical properties of Ni has been performed in an energy loss range of 0-200 eV from the measured REELS spectra at primary energies of 1000 eV, 2000 eV and 3000 eV. The reliability of our method was tested by comparing our results with the previous data. Moreover, the accuracy of our optical data has been confirmed by applying oscillator strength-sum rule and perfect-screening-sum rule.

Radiation spectra of high-energy electrons in monocrystals of various thickness and orientation

International Nuclear Information System (INIS)

Avakyan, R.O.; Agan'yants, A.O.; Akopov, N.Z.; Vartanov, Yu.A.; Vartapetyan, G.A.; Lebedev, A.N.; Mirzoyan, R.M.; Taroyan, S.P.; Danagulyan, S.S.

1982-01-01

Yield of photons with energies 20-200 MeV at motion of the 4.7 GeV electron beam in parallel to the axis of a diamond crystal exceeds substantially the corresponding yield from a disoriented target. A similarity is observed in the radiation spectra within the crystal thickness range of 100- 610 mkm. The radiation yield is suppressed at certain energies of the γ quanta [ru

Determining the band gap and mean kinetic energy of atoms from reflection electron energy loss spectra

International Nuclear Information System (INIS)

Vos, M.; Marmitt, G. G.; Finkelstein, Y.; Moreh, R.

2015-01-01

Reflection electron energy loss spectra from some insulating materials (CaCO 3 , Li 2 CO 3 , and SiO 2 ) taken at relatively high incoming electron energies (5–40 keV) are analyzed. Here, one is bulk sensitive and a well-defined onset of inelastic excitations is observed from which one can infer the value of the band gap. An estimate of the band gap was obtained by fitting the spectra with a procedure that includes the recoil shift and recoil broadening affecting these measurements. The width of the elastic peak is directly connected to the mean kinetic energy of the atom in the material (Doppler broadening). The experimentally obtained mean kinetic energies of the O, C, Li, Ca, and Si atoms are compared with the calculated ones, and good agreement is found, especially if the effect of multiple scattering is taken into account. It is demonstrated experimentally that the onset of the inelastic excitation is also affected by Doppler broadening. Aided by this understanding, we can obtain a good fit of the elastic peak and the onset of inelastic excitations. For SiO 2 , good agreement is obtained with the well-established value of the band gap (8.9 eV) only if it is assumed that the intensity near the edge scales as (E − E gap ) 1.5 . For CaCO 3 , the band gap obtained here (7 eV) is about 1 eV larger than the previous experimental value, whereas the value for Li 2 CO 3 (7.5 eV) is the first experimental estimate

Energy spectra and charge composition of galactic cosmic rays measured in ATIC-2 experiment

International Nuclear Information System (INIS)

Zatsepin, V.I.; Bat'kov, K.E.; Bashindzhagyan, G.L.

2004-01-01

The ATIC (Advanced Thin Ionization Calorimeter) balloon experiment is intended for measuring the energy spectra of the galactic cosmic rays with the individual resolution by the charge from protons to iron within the energy range from 50 GeV up to 100 TeV. The silicon detector matrix, making it possible to solve on the inverse current by means of the detector charge high segmentation, was applied for the first time in the high-energy cosmic rays for the charge measurement. The ATIC completed two successful flights in the Antarctica since 28.12.2000 up to 13.01.2001 (the ATIC-1 test flight) and since 29.12.2002 up to 18.01.2003 (the ATIC-2 scientific flight). The current state of the analysis of the spectra, measured in the ATIC-2 scientific flight, are presented in this work and the obtained results are compared with the model forecasts results [ru

Determination of fast neutrons energy spectra by Monte-Carlo Method

International Nuclear Information System (INIS)

Chetaine, A.

1986-01-01

Two computation codes based on the Monte-Carlo method are established for studying the spectrometry of neutrons with 14 Mev as initial energy. The spectra are determined, on one hand, around a neutron generator Ti-T target and, on the other hand, in a big paraffin cylinder. One code allows to determine the spectrum of neutrons irradiating the sample at various distances from the Ti-T target versus accelerator parameters: high voltage, atomic or molecular nature of deuterons beam, target thickness and materials surrounding the target. The other code determines neutron spectra at various positions inside and outside the 30 x 30 cm paraffin cylinder. The validity of the procedure used in these codes is verified by determining the spectrum of neutrons crossing a big surface, using the procedure in question and using direct simulation method. The biasing procedure used in the two codes permits to have results with good statistics from a reduced number of drawings. 70 figs.; 62 refs.; 1 tab. (author)

Determination of the low energy spectra in the superstring theory

International Nuclear Information System (INIS)

Rausch de Traubenberg, M.

1990-01-01

There is one solution to the superstring theory in 10 dimensions (SO(32) ou E8xE8) but in a 4-dimensions space, there are plenty of solutions, so a classification is necessary. The author has used a formulation named fermionic, where the solution is easy to build and he has developed a program in terms of formal calculation (REDUCE). In a first time, this program verifies the constraints induced by the modular invariance and then reproduces the low energy spectra

Estimation of sea level muon energy spectrum at high latitude from the latest primary nucleon spectra near the top of the atmosphere

CERN Document Server

Haldar, T K; Bhattacharya, D P; 10.1023/A:1024822518795

2003-01-01

Vertical muon energy spectra at sea level have been estimated from a directly measured primary cosmic-ray nucleon spectrum. The hadronic energy moments have been calculated from the CERN LEBC EHS data on the Lorentz invariant cross-section results on pp to pi /sup +or-/X and pp to K/sup +or-/X inclusive reactions and are duly corrected for A-A collisions. Finally, the sea level muon energy spectra have been calculated from the decay of conventional mesons, using standard formulation. The estimated muon spectra are found to be in good agreement with the directly measured muon spectra obtained from different experiments. (32 refs).

Neutron energy spectra calculations in the low power research reactor

International Nuclear Information System (INIS)

Omar, H.; Khattab, K.; Ghazi, N.

2011-01-01

The neutron energy spectra have been calculated in the fuel region, inner and outer irradiation sites of the zero power research reactor using the MCNP-4C code and the combination of the WIMS-D/4 transport code for generation of group constants and the three-dimensional CITATION diffusion code for core analysis calculations. The neutron energy spectrum has been divided into three regions and compared with the proposed empirical correlations. The calculated thermal and fast neutron fluxes in the low power research reactor MNSR inner and outer irradiation sites have been compared with the measured results. Better agreements have been noticed between the calculated and measured results using the MCNP code than those obtained by the CITATION code. (author)

Ion distribution dynamics near the Earth's bow shock: first measurements with the 2D ion energy spectrometer CORALL on the INTERBALL/Tail-probe satellite

Directory of Open Access Journals (Sweden)

Yu. I. Yermolaev

1997-05-01

Full Text Available The dynamics of the ion distribution function near the Earth's bow shock is studied on the basis of quasi-3D measurements of ion energy spectra in the range of 30–24200 eV/q with the Russian-Cuban CORALL instrument on the INTERBALL/Tail-probe satellite. The instrument was designed for observations of magnetospheric plasma and measures ions, in an angular range of 36°–144° from the Earth-Sun direction. Ion populations generated by the Earth bow shock are often observed upstream from the bow shock. In the solar-wind stream compressed and heated by the passing of very dense magnetic cloud (CME, two types of these ion populations were measured upstream and before the bow shock crossing on 25 August 1995 at 07:37 UT. Both populations were observed in the energy range above 2 keV. At ~06:20 UT, when the angle between the direction of the interplanetary magnetic field and normal to the bow shock VBn was ≃ 43° the instrument observed a narrow, fast (~800 km/s field-aligned beam moving from the Earth. At ~07:30, when Bn ≃ 28°, the wide ion pitch-angle distribution was observed. A similar suprathermal ion population is observed in the magnetosheath simultaneously with the solar-wind ion population being heated and deflected from the Sun-Earth direction. The similarity of observations during the mentioned time-interval and under usual solar-wind conditions allows us to conclude that types of suprathermal ion populations upstream and downstream from the bow shock do not depend on the solar-wind disturbance generated by magnetic cloud.

Energy spectra unfolding of fast neutron sources using the group method of data handling and decision tree algorithms

Energy Technology Data Exchange (ETDEWEB)

Hosseini, Seyed Abolfazl, E-mail: sahosseini@sharif.edu [Department of Energy Engineering, Sharif University of Technology, Tehran 8639-11365 (Iran, Islamic Republic of); Afrakoti, Iman Esmaili Paeen [Faculty of Engineering & Technology, University of Mazandaran, Pasdaran Street, P.O. Box: 416, Babolsar 47415 (Iran, Islamic Republic of)

2017-04-11

Accurate unfolding of the energy spectrum of a neutron source gives important information about unknown neutron sources. The obtained information is useful in many areas like nuclear safeguards, nuclear nonproliferation, and homeland security. In the present study, the energy spectrum of a poly-energetic fast neutron source is reconstructed using the developed computational codes based on the Group Method of Data Handling (GMDH) and Decision Tree (DT) algorithms. The neutron pulse height distribution (neutron response function) in the considered NE-213 liquid organic scintillator has been simulated using the developed MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). The developed computational codes based on the GMDH and DT algorithms use some data for training, testing and validation steps. In order to prepare the required data, 4000 randomly generated energy spectra distributed over 52 bins are used. The randomly generated energy spectra and the simulated neutron pulse height distributions by MCNPX-ESUT for each energy spectrum are used as the output and input data. Since there is no need to solve the inverse problem with an ill-conditioned response matrix, the unfolded energy spectrum has the highest accuracy. The {sup 241}Am-{sup 9}Be and {sup 252}Cf neutron sources are used in the validation step of the calculation. The unfolded energy spectra for the used fast neutron sources have an excellent agreement with the reference ones. Also, the accuracy of the unfolded energy spectra obtained using the GMDH is slightly better than those obtained from the DT. The results obtained in the present study have good accuracy in comparison with the previously published paper based on the logsig and tansig transfer functions. - Highlights: • The neutron pulse height distribution was simulated using MCNPX-ESUT. • The energy spectrum of the neutron source was unfolded using GMDH. • The energy spectrum of the neutron source was

Determining the band gap and mean kinetic energy of atoms from reflection electron energy loss spectra

Energy Technology Data Exchange (ETDEWEB)

Vos, M. [Atomic and Molecular Physics Laboratories, Research School of Physics and Engineering, Australian National University, Canberra ACT (Australia); Marmitt, G. G. [Atomic and Molecular Physics Laboratories, Research School of Physics and Engineering, Australian National University, Canberra ACT (Australia); Instituto de Fisica da Universidade Federal do Rio Grande do Sul, Avenida Bento Goncalves 9500, 91501-970 Porto Alegre, RS (Brazil); Finkelstein, Y. [Nuclear Research Center — Negev, Beer-Sheva 84190 (Israel); Moreh, R. [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel)

2015-09-14

Reflection electron energy loss spectra from some insulating materials (CaCO{sub 3}, Li{sub 2}CO{sub 3}, and SiO{sub 2}) taken at relatively high incoming electron energies (5–40 keV) are analyzed. Here, one is bulk sensitive and a well-defined onset of inelastic excitations is observed from which one can infer the value of the band gap. An estimate of the band gap was obtained by fitting the spectra with a procedure that includes the recoil shift and recoil broadening affecting these measurements. The width of the elastic peak is directly connected to the mean kinetic energy of the atom in the material (Doppler broadening). The experimentally obtained mean kinetic energies of the O, C, Li, Ca, and Si atoms are compared with the calculated ones, and good agreement is found, especially if the effect of multiple scattering is taken into account. It is demonstrated experimentally that the onset of the inelastic excitation is also affected by Doppler broadening. Aided by this understanding, we can obtain a good fit of the elastic peak and the onset of inelastic excitations. For SiO{sub 2}, good agreement is obtained with the well-established value of the band gap (8.9 eV) only if it is assumed that the intensity near the edge scales as (E − E{sub gap}){sup 1.5}. For CaCO{sub 3}, the band gap obtained here (7 eV) is about 1 eV larger than the previous experimental value, whereas the value for Li{sub 2}CO{sub 3} (7.5 eV) is the first experimental estimate.

Experimental characterization of the neutron spectra generated by a high-energy clinical LINAC

Energy Technology Data Exchange (ETDEWEB)

Amgarou, K., E-mail: khalil.amgarou@uab.e [Institut de Radioprotection et de Surete Nucleaire (IRSN), Laboratoire de Metrologie et de Dosimetrie des Neutrons, F-13115 Saint Paul-Lez-Durance (France); Lacoste, V.; Martin, A. [Institut de Radioprotection et de Surete Nucleaire (IRSN), Laboratoire de Metrologie et de Dosimetrie des Neutrons, F-13115 Saint Paul-Lez-Durance (France)

2011-02-11

The production of unwanted neutrons by electron linear accelerators (LINACs) has attracted a special attention since the early 50s. The renewed interest in this topic during the last years is due mainly to the increased use of such machines in radiotherapy. Specially, in most of developing countries where many old teletherapy irradiators, based on {sup 60}Co and {sup 137}Cs radioactive sources, are being replaced with new LINAC units. The main objective of this work is to report the results of an experimental characterization of the neutron spectra generated by a high-energy clinical LINAC. Measurements were carried out, considering four irradiation configurations, by means of our recently developed passive Bonner sphere spectrometer (BSS) using pure gold activation foils as central detectors. This system offers the possibility to measure neutrons over a wide energy range (from thermal up to a few MeV) at pulsed, intense and complex mixed n-{gamma} fields. A two-step unfolding method that combines the NUBAY and MAXED codes was applied to derive the final neutron spectra as well as their associated integral quantities (in terms of total neutron fluence and ambient dose equivalent rates) and fluence-averaged energies.

Preliminary investigations of Monte Carlo Simulations of neutron energy and LET spectra for fast neutron therapy facilities

International Nuclear Information System (INIS)

Kroc, T.K.

2009-01-01

No fast neutron therapy facility has been built with optimized beam quality based on a thorough understanding of the neutron spectrum and its resulting biological effectiveness. A study has been initiated to provide the information necessary for such an optimization. Monte Carlo studies will be used to simulate neutron energy spectra and LET spectra. These studies will be bench-marked with data taken at existing fast neutron therapy facilities. Results will also be compared with radiobiological studies to further support beam quality ptimization. These simulations, anchored by this data, will then be used to determine what parameters might be optimized to take full advantage of the unique LET properties of fast neutron beams. This paper will present preliminary work in generating energy and LET spectra for the Fermilab fast neutron therapy facility.

Interatomic scattering in energy dependent photoelectron spectra of Ar clusters

Energy Technology Data Exchange (ETDEWEB)

Patanen, M.; Benkoula, S.; Nicolas, C.; Goel, A. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Antonsson, E. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Physikalische und Theoretische Chemie Institut für Chemie und Biochemie, Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin (Germany); Neville, J. J. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick E3B 6E2 (Canada); Miron, C., E-mail: Catalin.Miron@synchrotron-soleil.fr [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Extreme Light Infrastructure - Nuclear Physics (ELI-NP), ‘Horia Hulubei’ National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125 Măgurele, Jud. Ilfov (Romania)

2015-09-28

Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon clusters are recorded over an extended range of photon energies. The Ar 2p intensity ratios between atomic argon and clusters’ surface and bulk components reveal oscillations similar to photoelectron extended X-ray absorption fine structure signal (PEXAFS). We demonstrate here that this technique allows us to analyze separately the PEXAFS signals from surface and bulk sites of free-standing, neutral clusters, revealing a bond contraction at the surface.

Energy spectra in $p$-shell $\\Lambda$ hypernuclei and $^{19}_{\\Lambda}\\textrm{F}$ and spin-dependent $\\Lambda N$ interactions

OpenAIRE

Kanada-En'yo, Yoshiko; Isaka, Masahiro; Motoba, Toshio

2018-01-01

Energy spectra of $0s$-orbit $\\Lambda$ states in $p$-shell $\\Lambda$ hypernuclei ($^{A}_\\Lambda Z$) and those in $^{19}_{\\Lambda}\\textrm{F}$ are studied with the microscopic cluster model and antisymmetrized molecular dynamics using the $G$-matrix effective $\\Lambda N$ ($\\Lambda NG$) interactions. Spin-dependent terms of the ESC08a version of the $\\Lambda NG$ interactions are tested and phenomenologically tuned to reproduce observed energy spectra in $p$-shell $^{A}_\\Lambda Z$. Spin-dependent...

Non-Hermitian systems of Euclidean Lie algebraic type with real energy spectra

Science.gov (United States)

Dey, Sanjib; Fring, Andreas; Mathanaranjan, Thilagarajah

2014-07-01

We study several classes of non-Hermitian Hamiltonian systems, which can be expressed in terms of bilinear combinations of Euclidean-Lie algebraic generators. The classes are distinguished by different versions of antilinear (PT)-symmetries exhibiting various types of qualitative behaviour. On the basis of explicitly computed non-perturbative Dyson maps we construct metric operators, isospectral Hermitian counterparts for which we solve the corresponding time-independent Schrödinger equation for specific choices of the coupling constants. In these cases general analytical expressions for the solutions are obtained in the form of Mathieu functions, which we analyze numerically to obtain the corresponding energy spectra. We identify regions in the parameter space for which the corresponding spectra are entirely real and also domains where the PT symmetry is spontaneously broken and sometimes also regained at exceptional points. In some cases it is shown explicitly how the threshold region from real to complex spectra is characterized by the breakdown of the Dyson maps or the metric operator. We establish the explicit relationship to models currently under investigation in the context of beam dynamics in optical lattices.

Derivation of the radial profile of ion temperature from the measured energy spectra of charge-exchanged neutrals

Energy Technology Data Exchange (ETDEWEB)

Nakamura, K; Hiraki, N; Toi, K; Itoh, S

1980-01-01

In the TRIAM-1 tokamak the energy spectra of charge-exchanged neutrals are observed by scanning the neutral energy analyzer vertically. The measured ion temperature obtained from the only energy spectrum observed in the peripheral region is much higher than that predicted by the neoclassical transport theory because of reflection (backscattering) of neutrals at the wall. The actual ion temperature profile is derived from all observed energy spectra by the numerical code in which a wall-reflection effect of neutrals and an impermeability of plasma are taken into account. The reflection coefficient is adjusted so that the calculated ion temperature profile should be the best fit for the ion temperatures measured by the Doppler broadening of the visible lines He II 4686 A and H-alpha at the relevant radial positions.

Study of electron transition energies between anions and cations in spinel ferrites using differential UV–vis absorption spectra

International Nuclear Information System (INIS)

Xue, L.C.; Wu, L.Q.; Li, S.Q.; Li, Z.Z.; Tang, G.D.; Qi, W.H.; Ge, X.S.; Ding, L.L.

2016-01-01

It is very important to determine electron transition energies (E_t_r) between anions and different cations in order to understand the electrical transport and magnetic properties of a material. Many authors have analyzed UV–vis absorption spectra using the curve (αhν)"2 vs E, where α is the absorption coefficient and E(=hν) is the photon energy. Such an approach can give only two band gap energies for spinel ferrites. In this paper, using differential UV–vis absorption spectra, dα/dE vs E, we have obtained electron transition energies (E_t_r) between the anions and cations, Fe"2"+ and Fe"3"+ at the (A) and [B] sites and Ni"2"+ at the [B] sites for the (A)[B]_2O_4 spinel ferrite samples Co_xNi_0_._7_−_xFe_2_._3O_4 (0.0≤x≤0.3), Cr_xNi_0_._7Fe_2_._3_−_xO_4 (0.0≤x≤0.3) and Fe_3O_4. We suggest that the differential UV–vis absorption spectra should be accepted as a general analysis method for determining electron transition energies between anions and cations.

Transverse energy distribution, charged particle multiplicities and spectra in 16O-nucleus collisions

International Nuclear Information System (INIS)

Sunier, J.W.

1987-01-01

The HELIOS (High Energy Lepton and Ion Spectrometer) experiment, installed at the CERN Super Proton Synchrotron, proposes to examine in details the physical properties of a state of high energy created in nuclei by ultra-relativistic nucleus-nucleus collisions. It is generally believed that, at high densities or temperatures, a phase transition to a plasma of quark and gluons will occur. The dynamic of the expansion of such a plasma and its subsequent condensation into a hadron gas should markedly affect the composition and momentum distribution of the emerging particles and photons. The HELIOS experimental setup therefore combines 4π calorimetric coverage with measurements of inclusive particle spectra, two particle correlations, low and high mass lepton pairs and photons. The emphasis is placed on transverse energy flow (E/sub T/) measurements with good energy resolution, and the ability to trigger the acquisition of data in a variety of E/sub T/ ranges, thereby selecting the impact parameter or the violence of the collisions. This short note presents HELIOS results, for the most part still preliminary, on 16 O-nucleus collisions at the incident energies of 60 and 200 GeV per nucleon. The E/sub T/ distributions from Al, Ag and W targets are discussed and compared to the associated charged particle multiplicities from W. Charged particle and (converted) photon spectra measured with the external magnetic spectrometer are compared for 16 O + W and p + W collisions at 200 GeV per nucleon. 5 refs., 7 figs

Calculations of the energy spectra of Zn, Ga and Ge isotopes by the shell model

International Nuclear Information System (INIS)

Sakakura, M.; Shikata, Y.; Arima, A.; Sebe, T.

1979-01-01

The effective Hamiltonian which was determined empirically by Koops and Glaudemans is tested in shell model calculations for the 65-68 Zn, 67-69 Ga, and 68-70 Ge nuclei in the full (1p 3 / 2 , 0f 5 / 2 , 1p 1 / 2 )n space. The resulting energy spectra are compared with the experimental spectra and results of previous calculations. The overall agreement with experiment is as satisfactory for these nuclei as for the Ni and Cu isotopes, by which the Hamiltonian was determined. It is noticed that the spectra of 67 Zn and 67 , 69 Ga calculated in this work are similar to those provided by the Alaga model. (orig.) [de

Simulations of the Fe K α Energy Spectra from Gravitationally Microlensed Quasars

Energy Technology Data Exchange (ETDEWEB)

Krawczynski, H. [Physics Department and McDonnell Center for the Space Sciences, Washington University in St. Louis, 1 Brookings Drive, CB 1105, St. Louis, MO 63130 (United States); Chartas, G., E-mail: krawcz@wustl.edu [Department of Physics and Astronomy, College of Charleston, Charleston, SC 29424 (United States)

2017-07-10

The analysis of the Chandra X-ray observations of the gravitationally lensed quasar RX J1131−1231 revealed the detection of multiple and energy-variable spectral peaks. The spectral variability is thought to result from the microlensing of the Fe K α emission, selectively amplifying the emission from certain regions of the accretion disk with certain effective frequency shifts of the Fe K α line emission. In this paper, we combine detailed simulations of the emission of Fe K α photons from the accretion disk of a Kerr black hole with calculations of the effect of gravitational microlensing on the observed energy spectra. The simulations show that microlensing can indeed produce multiply peaked energy spectra. We explore the dependence of the spectral characteristics on black hole spin, accretion disk inclination, corona height, and microlensing amplification factor and show that the measurements can be used to constrain these parameters. We find that the range of observed spectral peak energies of QSO RX J1131−1231 can only be reproduced for black hole inclinations exceeding 70° and for lamppost corona heights of less than 30 gravitational radii above the black hole. We conclude by emphasizing the scientific potential of studies of the microlensed Fe K α quasar emission and the need for more detailed modeling that explores how the results change for more realistic accretion disk and corona geometries and microlensing magnification patterns. A full analysis should furthermore model the signal-to-noise ratio of the observations and the resulting detection biases.

Determination of the optical absorption spectra of thin layers from their photoacoustic spectra

Science.gov (United States)

Bychto, Leszek; Maliński, Mirosław; Patryn, Aleksy; Tivanov, Mikhail; Gremenok, Valery

2018-05-01

This paper presents a new method for computations of the optical absorption coefficient spectra from the normalized photoacoustic amplitude spectra of thin semiconductor samples deposited on the optically transparent and thermally thick substrates. This method was tested on CuIn(Te0.7Se0.3)2 thin films. From the normalized photoacoustic amplitude spectra, the optical absorption coefficient spectra were computed with the new formula as also with the numerical iterative method. From these spectra, the value of the energy gap of the thin film material and the type of the optical transitions were determined. From the experimental optical transmission spectra, the optical absorption coefficient spectra were computed too, and compared with the optical absorption coefficient spectra obtained from photoacoustic spectra.

Interplanetary ions during an energetic storm particle event: The distribution function from solar wind thermal energies to 1.6 MeV

International Nuclear Information System (INIS)

Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.; Zwickl, R.D.; Paschmann, G.; Sckopke, N.; Hynds, R.J.

1981-01-01

Data from the Los Alamos Scientific Laboratory/Max-Planck-Institut fast plasma experiment on Isee 2 have been combined with data from the European Space Agency/Imperial College/Space Research Laboratory low-energy proton experiment on Isee 3 to obtain for the first time an ion velocity distribution function f(v) extending from solar wind energies (-1 keV) to 1.6 MeV during the postshock phase of an energetic storm particle (ESP) event. This study reveals that f(v) of the ESP population is roughly isotropic in the solar wind frame from solar wind thermal energies out to 1.6 MeV. Emerging smoothly out of the solar wind thermal distribution, the ESP f(v) initially falls with increasing energy as E/sup -2.4/ in the solar wind frame. Above about 40 keV no single power law exponent adequately describes the energy dependence of f(v) in the solar wind frame. Above approx.200 keV in both the spacecraft frame and the solar wind frame, f(v) can be described by an exponential in speed (f(v)proportionale/sup -v/v//sub o/) with v/sub o/ = 1.05 x 10 8 cm s -1 . The ESP event studied (August 27, 1978) was superposed upon a more energetic particle event which was predominantly field-aligned and which was probably of solar origin. Our observations suggest that the ESP population is accelerated directly out of the solar wind thermal population or its quiescent suprathermal tail by a stochastic process associated with the shock wave disturbance. The acceleration mechanism is sufficiently efficient that approx.1% of the solar wind population is accelerated to suprathermal energies. These suprathermal particles have an energy density of approx.290 eV cm -3

Calculated microdose spectra for intermediate energy neutrons (1 to 100 keV)

International Nuclear Information System (INIS)

Al-Affan, I.A.M.; Watt, D.E.

1983-01-01

Basic formulae for calculation of energy deposition events due to insiders, starters, stoppers and crossers, using the continuous slowing down approximation have been modified to allow for the enhanced energy deposition in spherical volumes due to elastic scattering interactions which reduce the penetration depth of the charged particle recoils. Energy deposition spectra have been obtained for energies of 1, 10, 50, 100 keV in 0.2 μm and 1 μm tissue-equivalent spheres. From these, frequency and dose distributions in lineal energy and in specific energy density have been calculated. Also calculated for different neutron energies are values of zeta, the energy average of event size, as a function of the diameter of the sensitive site. The structure of the energy event distributions can be interpreted in terms of the basic physics. The effect of the modifications to the basic formulae is to increase the number of energy deposition events due to insiders and to decrease the number of starters, stoppers and crossers. The degree of the effect increases with decreasing neutron energy, increasing sphere size, and the change is most significant for low energy deposition events. (author)

Calculated microdose spectra for intermediate energy neutrons (1 to 100 keV)

Energy Technology Data Exchange (ETDEWEB)

Al-Affan, I.A.M.; Watt, D.E. (Dundee Univ. (UK). Dept. of Medical Biophysics); Colautti, P.; Talpo, G. (Laboratori Nazionali dell' Infn, 35020, Legnaro (Padova) (Italy))

1983-01-01

Basic formulae for calculation of energy deposition events due to insiders, starters, stoppers and crossers, using the continuous slowing down approximation have been modified to allow for the enhanced energy deposition in spherical volumes due to elastic scattering interactions which reduce the penetration depth of the charged particle recoils. Energy deposition spectra have been obtained for energies of 1, 10, 50, 100 keV in 0.2 ..mu..m and 1 ..mu..m tissue-equivalent spheres. From these, frequency and dose distributions in lineal energy and in specific energy density have been calculated. Also calculated for different neutron energies are values of zeta, the energy average of event size, as a function of the diameter of the sensitive site. The structure of the energy event distributions can be interpreted in terms of the basic physics. The effect of the modifications to the basic formulae is to increase the number of energy deposition events due to insiders and to decrease the number of starters, stoppers and crossers. The degree of the effect increases with decreasing neutron energy, increasing sphere size, and the change is most significant for low energy deposition events.

Derivation of the radial profile of ion temperature from the 'measured' energy spectra of charge-exchanged neutrals

International Nuclear Information System (INIS)

Nakamura, Kazuo; Hiraki, Naoji; Toi, Kazuo; Itoh, Satoshi

1980-01-01

In the TRIAM-1 tokamak the energy spectra of charge-exchanged neutrals are observed by scanning the neutral energy analyzer vertically. The ''measured'' ion temperature obtained from only energy spectrum observed in the peripheral region is much higher than that predicted by the neoclassical transport theory because of reflection (backscattering) of neutrals at the wall. The ''actual'' ion temperature profile is derived from all observed energy spectra by using the numerical code in which a wall-reflection effect of neutrals and an impermeability of plasma are taken into account. In this numerical analysis, the reflection coefficient is adjusted so that the above calculated ion temperature profile should be best fit for the ion temperatures measured by the Doppler broadening of the visible lines HeII 4686 A and H sub(α) at the relevant radial positions. (author)

Derivation of the radial profile of ion temperature from the 'measured' energy spectra of charge-exchanged neutrals

Energy Technology Data Exchange (ETDEWEB)

Nakamura, K; Hiraki, N; Toi, K; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1980-07-01

In the TRIAM-1 tokamak the energy spectra of charge-exchanged neutrals are observed by scanning the neutral energy analyzer vertically. The ''measured'' ion temperature obtained from only energy spectrum observed in the peripheral region is much higher than that predicted by the neoclassical transport theory because of reflection (backscattering) of neutrals at the wall. The ''actual'' ion temperature profile is derived from all observed energy spectra by using the numerical code in which a wall-reflection effect of neutrals and an impermeability of plasma are taken into account. In this numerical analysis, the reflection coefficient is adjusted so that the above calculated ion temperature profile should be best fit for the ion temperatures measured by the Doppler broadening of the visible lines HeII 4686 A and H sub(..cap alpha..) at the relevant radial positions.

1012 - 1015 eV interaction deduced from energy spectra of gamma-ray and hadrons at airplane altitude

International Nuclear Information System (INIS)

Takahashi, Yoshiyuki

1978-01-01

The present paper deals with the latest results of the spectral measurements of high energy cosmic ray performed on an airplane with an emulsion chamber. The hadronic component together with the gamma-ray component were observed in the region of gamma energy not smaller than 30 GeV and gamma energy sum not larger than 40 TeV. It was observed that the integral spectra of hadronic showers showed less steep power than those obtained at mountain stations. On the other hand, the integral spectra of gamma-ray in the energy region from 40 GeV to 40 TeV showed steeper power than those of hadronic component. The zenith angle distributions of hadrons and gamma-ray were inspected, and it was confirmed that the observed distributions were well reproduced by the theoretical curves with the appropriate attenuation length. (Yoshimori, M.)

Neutron flux density and secondary-particle energy spectra at the 184-inch synchrocyclotron medical facility

International Nuclear Information System (INIS)

Smith, A.R.; Schimmerling, W.; Henson, A.M.; Kanstein, L.L.; McCaslin, J.B.; Stephens, L.D.; Thomas, R.H.; Ozawa, J.; Yeater, F.W.

1978-07-01

Helium ions, with an energy of 920 MeV, produced by the 184-inch synchrocyclotron of the Lawrence Berkeley Laboratory are now being used in a pilot series to determine their efficacy in the treatment of tumors of large volume. The techniques for production of the large uniform radiation fields required for these treatments involve the use of beam-limiting collimators and energy degraders. Interaction of the primary beam with these beam components produces secondary charged particles and neutrons. The sources of neutron production in the beam transport system of the alpha-particle beam have been identified and their magnitudes have been determined. Measurements with activation detectors and pulse counters of differing energy responses have been used to determine secondary particle spectra at various locations on the patient table. These spectra are compared to a calculation of neutron production based on best estimates derived from published cross sections. Agreement between the calculated spectra and those derived from experimental measurements is obtained (at the 10 to 20% level) when the presence of charged particles is taken into account. The adsorbed dose in soft tissue is not very sensitive to the shape of the incident neutron energy spectrum, and the values obtained from unfolding the experimental measurements agree with the values obtained from the calculated spectra within the estimated uncertainty of +-25%. These values are about 3 x 10 -3 rad on the beam axis and about 1 x 10 -3 rad at 20 cm or more from the beam axis, per rad deposited by the incident alpha-particle beam. Estimates of upper limit dose to the lens of the eye and red bone marrow are approximately 10 rad and approximately 1 rad, respectively, for a typical treatment plan. The absorbed dose to the lens of the eye is thus well below the threshold value for cataractogenesis estimated for fission neutrons. An upper limit for the risk of leukemia is estimated to be approximately 0.04%

Peculiarities of approximation for reactor neutron energy spectra during computerized simulation of radiation defects

International Nuclear Information System (INIS)

Kupchishin, A.A.; Kupchishin, A.I.; Stusik, G.; Omarbekova, Zh.

2001-01-01

Peculiarities of approximation for reactor neutron energy spectra during radiation defects computerized simulation were discussed. Approximation of neutron spectra N(E) was carried out by N(E)=α·exp(-β·E)·sh(γ·E) formula (1), where α, β, γ - approximation coefficients. In the capacity of operating reactor data experimental data on 235 U and 239 Pu were applied. The algorithm was designed, and acting soft ware for spectra parameters calculation was developed. The following values of approximation parameters were obtained: α=80.8; β=0.935;γ=2.04 (for uranium and plutonium these coefficients are less distinguishing). Then with use of formula 1 and α, β, γ coefficients the approximation curves were constructed. These curves satisfactorily describe existing experimental data and allowing to use its for radiation defects simulation in the reactor materials

The cyclopropene radical cation: Rovibrational level structure at low energies from high-resolution photoelectron spectra

Energy Technology Data Exchange (ETDEWEB)

Vasilatou, K.; Michaud, J. M.; Baykusheva, D.; Grassi, G.; Merkt, F. [Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zurich (Switzerland)

2014-08-14

The cyclopropene radical cation (c-C{sub 3}H{sub 4}{sup +}) is an important but poorly characterized three-membered-ring hydrocarbon. We report on a measurement of the high-resolution photoelectron and photoionization spectra of cyclopropene and several deuterated isotopomers, from which we have determined the rovibrational energy level structure of the X{sup ~+} {sup 2}B{sub 2} ground electronic state of c-C{sub 3}H{sub 4}{sup +} at low energies for the first time. The synthesis of the partially deuterated isotopomers always resulted in mixtures of several isotopomers, differing in their number of D atoms and in the location of these atoms, so that the photoelectron spectra of deuterated samples are superpositions of the spectra of several isotopomers. The rotationally resolved spectra indicate a C{sub 2v}-symmetric R{sub 0} structure for the ground electronic state of c-C{sub 3}H{sub 4}{sup +}. Two vibrational modes of c-C{sub 3}H{sub 4}{sup +} are found to have vibrational wave numbers below 300 cm{sup −1}, which is surprising for such a small cyclic hydrocarbon. The analysis of the isotopic shifts of the vibrational levels enabled the assignment of the lowest-frequency mode (fundamental wave number of ≈110 cm{sup −1} in c-C{sub 3}H{sub 4}{sup +}) to the CH{sub 2} torsional mode (ν{sub 8}{sup +}, A{sub 2} symmetry) and of the second-lowest-frequency mode (≈210 cm{sup −1} in c-C{sub 3}H{sub 4}{sup +}) to a mode combining a CH out-of-plane with a CH{sub 2} rocking motion (ν{sub 15}{sup +}, B{sub 2} symmetry). The potential energy along the CH{sub 2} torsional coordinate is flat near the equilibrium structure and leads to a pronounced anharmonicity.

Statistical properties of Fermi GBM GRBs' spectra

Science.gov (United States)

Rácz, István I.; Balázs, Lajos G.; Horvath, Istvan; Tóth, L. Viktor; Bagoly, Zsolt

2018-03-01

Statistical studies of gamma-ray burst (GRB) spectra may result in important information on the physics of GRBs. The Fermi GBM catalogue contains GRB parameters (peak energy, spectral indices, and intensity) estimated fitting the gamma-ray spectral energy distribution of the total emission (fluence, flnc), and during the time of the peak flux (pflx). Using contingency tables, we studied the relationship of the models best-fitting pflx and flnc time intervals. Our analysis revealed an ordering of the spectra into a power law - Comptonized - smoothly broken power law - Band series. This result was further supported by a correspondence analysis of the pflx and flnc spectra categorical variables. We performed a linear discriminant analysis (LDA) to find a relationship between categorical (spectral) and model independent physical data. LDA resulted in highly significant physical differences among the spectral types, that is more pronounced in the case of the pflx spectra, than for the flnc spectra. We interpreted this difference as caused by the temporal variation of the spectrum during the outburst. This spectral variability is confirmed by the differences in the low-energy spectral index and peak energy, between the pflx and flnc spectra. We found that the synchrotron radiation is significant in GBM spectra. The mean low-energy spectral index is close to the canonical value of α = -2/3 during the peak flux. However, α is ˜ -0.9 for the spectra of the fluences. We interpret this difference as showing that the effect of cooling is important only for the fluence spectra.

Non-Hermitian systems of Euclidean Lie algebraic type with real energy spectra

International Nuclear Information System (INIS)

Dey, Sanjib; Fring, Andreas; Mathanaranjan, Thilagarajah

2014-01-01

We study several classes of non-Hermitian Hamiltonian systems, which can be expressed in terms of bilinear combinations of Euclidean–Lie algebraic generators. The classes are distinguished by different versions of antilinear (PT)-symmetries exhibiting various types of qualitative behaviour. On the basis of explicitly computed non-perturbative Dyson maps we construct metric operators, isospectral Hermitian counterparts for which we solve the corresponding time-independent Schrödinger equation for specific choices of the coupling constants. In these cases general analytical expressions for the solutions are obtained in the form of Mathieu functions, which we analyze numerically to obtain the corresponding energy spectra. We identify regions in the parameter space for which the corresponding spectra are entirely real and also domains where the PT symmetry is spontaneously broken and sometimes also regained at exceptional points. In some cases it is shown explicitly how the threshold region from real to complex spectra is characterized by the breakdown of the Dyson maps or the metric operator. We establish the explicit relationship to models currently under investigation in the context of beam dynamics in optical lattices. -- Highlights: •Different PT-symmetries lead to qualitatively different systems. •Construction of non-perturbative Dyson maps and isospectral Hermitian counterparts. •Numerical discussion of the eigenvalue spectra for one of the E(2)-systems. •Established link to systems studied in the context of optical lattices. •Setup for the E(3)-algebra is provided

Calculation of neutron and gamma ray energy spectra for fusion reactor shield design: comparison with experiment

International Nuclear Information System (INIS)

Santoro, R.T.; Alsmiller, R.G. Jr.; Barnes, J.M.; Chapman, G.T.

1980-08-01

Integral experiments that measure the transport of approx. 14 MeV D-T neutrons through laminated slabs of proposed fusion reactor shield materials have been carried out. Measured and calculated neutron and gamma ray energy spectra are compared as a function of the thickness and composition of stainless steel type 304, borated polyethylene, and Hevimet (a tungsten alloy), and as a function of detector position behind these materials. The measured data were obtained using a NE-213 liquid scintillator using pulse-shape discrimination methods to resolve neutron and gamma ray pulse height data and spectral unfolding methods to convert these data to energy spectra. The calculated data were obtained using two-dimensional discrete ordinates radiation transport methods in a complex calculational network that takes into account the energy-angle dependence of the D-T neutrons and the nonphysical anomalies of the S/sub n/ method

Bibliography on atomic energy levels and spectra. Special pub., Jul 1971--Jun 1975

International Nuclear Information System (INIS)

Hagan, L.

1977-01-01

This is the first supplement to the NBS Special Publication 363, 'Bibliography on Atomic Energy Levels and Spectra, July 1968 through June 1971,' and it covers the most recent literature from July 1971 through June 1975. It contains approximately 2150 references classified by subject for individual atoms and atomic ions. A number index identifies the references. An author index is included. References included contain data on energy levels, classified lines, wavelengths, Zeeman effect, Stark effect, hyperfine structure, isotope shift, ionization potentials, or theory which gives results for specific atoms or atomic ions

A Monte Carlo study of the energy spectra and transmission characteristics of scattered radiation from x-ray computed tomography.

Science.gov (United States)

Platten, David John

2014-06-01

Existing data used to calculate the barrier transmission of scattered radiation from computed tomography (CT) are based on primary beam CT energy spectra. This study uses the EGSnrc Monte Carlo system and Epp user code to determine the energy spectra of CT scatter from four different primary CT beams passing through an ICRP 110 male reference phantom. Each scatter spectrum was used as a broad-beam x-ray source in transmission simulations through seventeen thicknesses of lead (0.00-3.50 mm). A fit of transmission data to lead thickness was performed to obtain α, β and γ parameters for each spectrum. The mean energy of the scatter spectra were up to 12.3 keV lower than that of the primary spectrum. For 120 kVp scatter beams the transmission through lead was at least 50% less than predicted by existing data for thicknesses of 1.5 mm and greater; at least 30% less transmission was seen for 140 kVp scatter beams. This work has shown that the mean energy and half-value layer of CT scatter spectra are lower than those of the corresponding primary beam. The transmission of CT scatter radiation through lead is lower than that calculated with currently available data. Using the data from this work will result in less lead shielding being required for CT scanner installations.

Quark-gluon structure of the pomeron and the rise of inclusive spectra at high energies

International Nuclear Information System (INIS)

Kaidalov, A.V.

1982-01-01

The topological expansion and the nodel of a colour tube are used for the calculation of inclusive hadronic spectra in the central region. The higher-order terms of the 1/Nsub(f)-expansion, which correspond to the contribution of the poliperipheral diagrams are taken into account. It is shown that the intrinsic motion of quarks inside colliding hadrons leads to the rise of inclusive spectra with energy in the central region. The model gives a good quantitative description of the effects observed recently at the CERN SPS Collider

Proceedings of the symposium on measurements of neutron energy spectra using recoil proton proportional counters

International Nuclear Information System (INIS)

Urabe, Itsumasa

1986-01-01

This is a report of the symposium on measurements of neutron energy spectra using recoil proton proportional counters held at the Research Reactor Institute of Kyoto University on January 27 in 1986. An energy resolution, wall effects of response functions, n · γ discrimination methods and other fundamental properties of recoil proton counters are discussed for a new development of an application of this counter. (author)

Orbital momentum profiles and binding energy spectra for the complete valence shell of molecular fluorine

Energy Technology Data Exchange (ETDEWEB)

Zheng, Y.; Brion, C.E. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemistry; Brunger, M.J.; Zhao, K.; Grisogono, A.M.; Braidwood, S.; Weigold, E. [Flinders Univ. of South Australia, Adelaide, SA (Australia). Electronic Structure of Materials Centre; Chakravorty, S.J.; Davidson, E.R. [Indiana Univ., Bloomington, IN (United States). Dept. of Chemistry; Sgamellotti, A. [Univ di Perugia (Italy). Dipartimento di Chimica; von Niessen, W. [Technische Univ. Braunschweig (Germany). Inst fuer Physikalische

1996-01-01

The first electronic structural study of the complete valence shell binding energy spectrum of molecular fluorine, encompassing both the outer and inner valence regions, is reported. These binding energy spectra as well as the individual orbital momentum profiles have been measured using an energy dispersive multichannel electron momentum spectrometer at a total energy of 1500 eV, with an energy resolution of 1.5 eV and a momentum resolution of 0.1 a.u. The measured binding energy spectra in the energy range of 14-60 eV are compared with the results of ADC(4) many-body Green`s function and also direct-Configuration Interaction (CI) and MRSD-CI calculations. The experimental orbital electron momentum profiles are compared with SCF theoretical profiles calculated using the target Hartree-Fock approximation with a range of basis sets and with Density Functional Theory predictions in the target Kohn-Sham approximation with non-local potentials. The truncated (aug-cc-pv5z) Dunning basis sets were used for the Density Functional Theory calculations which also include some treatment of correlation via the exchange and correlation potentials. Comparisons are also made with the full ion-neutral overlap amplitude calculated with MRSD-CI wave functions. Large, saturated basis sets (199-GTO) were employed for both the high level SCF near Hartree-Fock limit and MRSD-CI calculations to investigate the effects of electron correlation and relaxation. 66 refs., 9 tabs., 9 figs.

Orbital momentum profiles and binding energy spectra for the complete valence shell of molecular fluorine

International Nuclear Information System (INIS)

Zheng, Y.; Brion, C.E.; Brunger, M.J.; Zhao, K.; Grisogono, A.M.; Braidwood, S.; Weigold, E.; Chakravorty, S.J.; Davidson, E.R.; Sgamellotti, A.; von Niessen, W.

1996-01-01

The first electronic structural study of the complete valence shell binding energy spectrum of molecular fluorine, encompassing both the outer and inner valence regions, is reported. These binding energy spectra as well as the individual orbital momentum profiles have been measured using an energy dispersive multichannel electron momentum spectrometer at a total energy of 1500 eV, with an energy resolution of 1.5 eV and a momentum resolution of 0.1 a.u. The measured binding energy spectra in the energy range of 14-60 eV are compared with the results of ADC(4) many-body Green's function and also direct-Configuration Interaction (CI) and MRSD-CI calculations. The experimental orbital electron momentum profiles are compared with SCF theoretical profiles calculated using the target Hartree-Fock approximation with a range of basis sets and with Density Functional Theory predictions in the target Kohn-Sham approximation with non-local potentials. The truncated (aug-cc-pv5z) Dunning basis sets were used for the Density Functional Theory calculations which also include some treatment of correlation via the exchange and correlation potentials. Comparisons are also made with the full ion-neutral overlap amplitude calculated with MRSD-CI wave functions. Large, saturated basis sets (199-GTO) were employed for both the high level SCF near Hartree-Fock limit and MRSD-CI calculations to investigate the effects of electron correlation and relaxation. 66 refs., 9 tabs., 9 figs

Equivalent half-value thickness and mean energies of filtered X-ray bremsstrahlung spectra

International Nuclear Information System (INIS)

Seelentag, W.W.; Panzer, W.

1980-01-01

X-ray beam qualities are often conveniently described by half-value thicknesses (in connection with tube voltage and filtration). Aluminium and copper are commonly used as half-value thickness materials, and either material may be used in a large intermediate energy range. Data comparisons frequently require conversions from values in Al to values in Cu. Equivalent half-value thicknesses for polychromatic radiations depend on the shapes of the spectra, but spectrometry is too expensive for routine application. Half-value thicknesses in both Al and Cu have been determined for some 250 spectra (tube potentials 10 to 300 kV). The results are tabulated, and these results together with a nomogram enable conversion with an accuracy of better than +- 5% in most cases. (UK)

Neutron dose and energy spectra measurements at Savannah River Plant

International Nuclear Information System (INIS)

Brackenbush, L.W.; Soldat, K.L.; Haggard, D.L.; Faust, L.G.; Tomeraasen, P.L.

1987-08-01

Because some workers have a high potential for significant neutron exposure, the Savannah River Plant (SRP) contracted with Pacific Northwest Laboratory (PNL) to verify the accuracy of neutron dosimetry at the plant. Energy spectrum and neutron dose measurements were made at the SRP calibrations laboratory and at several other locations. The energy spectra measurements were made using multisphere or Bonner sphere spectrometers, 3 He spectrometers, and NE-213 liquid scintillator spectrometers. Neutron dose equivalent determinations were made using these instruments and others specifically designed to determine dose equivalent, such as the tissue equivalent proportional counter (TEPC). Survey instruments, such as the Eberline PNR-4, and the thermoluminescent dosimeter (TLD)-albedo and track etch dosimeters (TEDs) were also used. The TEPC, subjectively judged to provide the most accurate estimation of true dose equivalent, was used as the reference for comparison with other devices. 29 refs., 43 figs., 13 tabs

A parametric model to describe neutron spectra around high-energy electron accelerators and its application in neutron spectrometry with Bonner Spheres

Science.gov (United States)

Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo

2010-03-01

Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.

A parametric model to describe neutron spectra around high-energy electron accelerators and its application in neutron spectrometry with Bonner Spheres

International Nuclear Information System (INIS)

Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo

2010-01-01

Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.

Measurements of proton energy spectra using a radiochromic film stack

Science.gov (United States)

Filkins, T. M.; Steidle, Jessica; Ellison, D. M.; Steidle, Jeffrey; Freeman, C. G.; Padalino, S. J.; Fiksel, G.; Regan, S. P.; Sangster, T. C.

2014-10-01

The energy spectrum of protons accelerated from the rear-side of a thin foil illuminated with ultra-intense laser light from the OMEGA EP laser system at the University of Rochester's Laboratory for Laser Energetics (LLE) was measured using a stack of radiochromic film (RCF). The film stack consisted of four layers of Gafchromic HD-V2 film and four layers of Gafchromic MD-V2-55 film. Aluminum foils of various thicknesses were placed between each piece of RCF in the stack. This arrangement allowed protons with energies of 30 MeV to reach the back layer of RCF in the stack. The stack was placed in the detector plane of a Thomson parabola ion energy (TPIE) spectrometer. Each piece of film in the stack was scanned using a commercially available flat-bed scanner (Epson 10000XL). The resulting optical density was converted into proton fluence using an absolute calibration of the RCF obtained at the SUNY Geneseo 1.7 MV Pelletron accelerator laboratory. In these calibration measurements, the sensitivity of the radiochromic film was measured using monoenergetic protons produced by the accelerator. Details of the analysis procedure and the resulting proton energy spectra will be presented. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics.

The determination of neutron energy spectra of radioisotope sources

International Nuclear Information System (INIS)

Lutkin, J.E.

1975-08-01

The neutron energy spectrum of a 241 Am-Be radioisotope neutron source has been determined by use of a time of flight neutron spectrometer; this spectrometer not being subject to the same uncertainties as a scintillation spectrometer. Neutron spectra have been determined using a scintillation spectrometer with which the effects of instrumental uncertainties, particularly the pulse shape discrimination have been assessed. In the course of the development of the time flight spectrometer a zero crossover pulse shape discrimination system was developed in order to reduce the unwanted background. Using this system a quantitative survey of pulse shape discrimination with experimental and commercial liquid and plastic organic scintillators were carried out. In addition the pulse shape discrimination properties of inorganic scintillators were also examined. (author)

Changes in the DRIFT Spectra of Softwood Materials Irradiated by UV-laser as a Function of Energy

Directory of Open Access Journals (Sweden)

BARTA, Edit

2005-01-01

Full Text Available We investigated energy dependence of the effect of UV-laser irradiation on the DRIFT spectra of softwood samples. Changes in the spectra of softwoods have been studied with 248.5 nm wavelength of UV-laser radiation. To monitor the energy dependence, different number of laser impulses were directed towards the sample’s surface. The dependence on energy of different bands can be listed into four groups. Broad absorption bands, which belong to the same chemical groups located at various positions, do not show consistent changes due to the absorption of different energy dozes. The intensity of OH bands for the treated samples can be higher or lower depending on the amount of radiation energy. In the CHn and in the band of non-conjugated carbonyl groups only absorption increase can be observed. Bands resulting from only one chemical component, and containing no other absorption maxima around them, uniformly decreased. The regions where the band of a chemical component lies next to another one, showed no consistent changes during the irradiation. The initial decrease was followed by increase.

Source Population and Acceleration Location of Suprathermal Heavy Ions in Corotating Interaction Regions

Energy Technology Data Exchange (ETDEWEB)

Filwett, R. J.; Desai, M. I. [University of Texas at San Antonio, San Antonio, TX (United States); Dayeh, M. A.; Broiles, T. W. [Southwest Research Institute, San Antonio, TX (United States)

2017-03-20

We have analyzed the ∼20–320 keV nucleon{sup −1} suprathermal (ST) heavy ion abundances in 41 corotating interaction regions (CIRs) observed by the Wind spacecraft from 1995 January to 2008 December. Our results are: (1) the CIR Fe/CNO and NeS/CNO ratios vary with the sunspot number, with values being closer to average solar energetic particle event values during solar maxima and lower than nominal solar wind values during solar minima. The physical mechanism responsible for the depleted abundances during solar minimum remains an open question. (2) The Fe/CNO increases with energy in the 6 events that occurred during solar maximum, while no such trends are observed for the 35 events during solar minimum. (3) The Fe/CNO shows no correlation with the average solar wind speed. (4) The Fe/CNO is well correlated with the corresponding upstream ∼20–320 keV nucleon{sup −1} Fe/CNO and not with the solar wind Fe/O measured by ACE in 31 events. Using the correlations between the upstream ∼20–40 keV nucleon{sup −1} Fe/CNO and the ∼20–320 keV nucleon{sup −1} Fe/CNO in CIRs, we estimate that, on average, the ST particles traveled ∼2 au along the nominal Parker spiral field line, which corresponds to upper limits for the radial distance of the source or acceleration location of ∼1 au beyond Earth orbit. Our results are consistent with those obtained from recent surveys, and confirm that CIR ST heavy ions are accelerated more locally, and are at odds with the traditional viewpoint that CIR ions seen at 1 au are bulk solar wind ions accelerated between 3 and 5 au.

Observation of luminescent spectra in low energy ion-neutral collisions. Progress report, June 1, 1976--May 31, 1978

International Nuclear Information System (INIS)

Leventhal, J.J.

1978-01-01

The experiments reported provide detailed information on the fundamental nature of energy transfer processes in ion-molecule or atom-molecule collisions. By combining ion beam techniques with emission spectroscopy, data are obtained which directly lead to internal energy state distributions of atomic and molecular products of these collisions. Data are in the form of emission spectra from nascent energetically excited species formed in the energy transfer process. Changes in the collision-produced spectra as a function of beam kinetic energy yield information on the extent of energy conversion (kinetic → internal) in the collision process. Some of the specific energy transfer processes studied are applicable to the problem of achieving inverted energy level populations in high pressure gas lasers. Also discussed are experiments designed to test theoretical models which predict product energy partitioning in molecular collisions. Because experimentally determined energy state distributions deviate substantially from the predicted distributions it is concluded that additional theoretical work is needed. A simple model was developed which qualitatively reproduces the important features of the data. This model, which is considerably more general than those previously available is outlined and briefly discussed

Exciton spectra and energy band structure of Cu{sub 2}ZnSiSe{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Guc, M., E-mail: gmax@phys.asm.md [Institute of Applied Physics, Academy of Sciences of Moldova, Academiei Str. 5, Chisinau MD 2028, Republic of Moldova (Moldova, Republic of); Levcenko, S. [Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Dermenji, L. [Institute of Applied Physics, Academy of Sciences of Moldova, Academiei Str. 5, Chisinau MD 2028, Republic of Moldova (Moldova, Republic of); Gurieva, G. [Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Schorr, S. [Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Free University Berlin, Institute of Geological Sciences, Malteserstr. 74-100, Berlin (Germany); Syrbu, N.N. [Technical University of Moldova, Chisinau MD-2004, Republic of Moldova (Moldova, Republic of); Arushanov, E. [Institute of Applied Physics, Academy of Sciences of Moldova, Academiei Str. 5, Chisinau MD 2028, Republic of Moldova (Moldova, Republic of)

2014-02-25

Highlights: • Reflection spectra of Cu{sub 2}ZnSiSe{sub 4} were studied for E ⊥ c and E || c light polarizations. • Four excitonic series are revealed in the reflection spectra at 10 K. • Model of exciton dispersion and the presence of a dead-layer. • Exciton Rydberg energies and free carriers effective masses were calculated. • Reflectivity for E ⊥ c and E || c were analyzed in the region 3–6 eV at 300 K. -- Abstract: Exciton spectra are studied in Cu{sub 2}ZnSiSe{sub 4} single crystals at 10 and 300 K by means of reflection spectroscopy. The exciton parameters, dielectric constant and free carriers effective masses are deduced from experimental spectra by calculations in the framework of a model taking into account the spatial dispersion and the presence of a dead-layer. The structure found in the reflectivity was analyzed and related to the theoretical electronic band structure of close related Cu{sub 2}ZnSiS{sub 4} semiconductor.

Energy spectra and asymmetry of charged particle emission in the muon minus capture by nuclei

International Nuclear Information System (INIS)

Balandin, M.P.; Grebenyuk, V.M.; Sinov, V.G.; Konin, A.D.

1978-01-01

Energy spectra of separated-by-mass single-charged particles at the capture of 130 MeV negative muons by carbon, oxygen, magnesium and sulphur have been measured. The experimental results are compared with the theoretical calculations at the assumption of preequilibrium decay of collective states described by the hydrodynamical model. The measurement of asymmetry of charged particle emission in sulphur and megnesium was carried out by hte method of muon spin precession in a magnetic field. Theoretical curves describe correctly the exponential spectra character, but the yields obtained are 2-3 times less than the experimental results

Portable instrument for measuring neutron energy spectra and neutron dose in a mixed n-γ field

International Nuclear Information System (INIS)

Daniels, C. J.; Silberberg, J. L.

1980-01-01

A portable high-speed neutron spectrometer consists of an organic scintillator, a true zero-crossing pulse shape discriminator, a 1 MHZ conversion-rate multichannel analyzer, an 8-bit microcomputer, and appropriate displays. The device can be used to measure neutron energy spectra and kerma rate in intense n- gamma radiation fields in which the neutron energy is from 5 to 15 MEV

Measurement of charge and energy spectra of heavy nuclei aboard Cosmos-936 artificial Earth satellite

International Nuclear Information System (INIS)

Dashin, S.A.; Marennyy, A.M.; Gertsen, G.P.

1982-07-01

Charge and energy spectra of heavy charged particles were measured. Measurements were performed by a package of dielectric track detectors mounted behind the shield of 60-80 kg m to the minus second power thick. The charge of nuclei was determined from the complete track length. A group of 1915 tracks of nuclei with Z 6 in the energy range 100-450 MeV/nuclon were identified. The differential charge spectrum of nuclei with 6 Z 28 and the energy spectrum of nuclei of the iron group were built

Local secondary-electron emission spectra of graphite and gold surfaces obtained using the Scanning Probe Energy Loss Spectrometer (SPELS)

International Nuclear Information System (INIS)

Lawton, J J; Pulisciano, A; Palmer, R E

2009-01-01

Secondary-electron emission (SEE) spectra have been obtained with the Scanning Probe Energy Loss Spectrometer at a tip-sample distance of only 50 nm. Such short working distances are required for the best theoretical spatial resolution (<10 nm). The SEE spectra of graphite, obtained as a function of tip bias voltage, are shown to correspond to unoccupied states in the electronic band structure. The SEE spectra of thin gold films demonstrate the capability of identifying (carbonaceous) surface contamination with this technique.

Local secondary-electron emission spectra of graphite and gold surfaces obtained using the Scanning Probe Energy Loss Spectrometer (SPELS)

Energy Technology Data Exchange (ETDEWEB)

Lawton, J J; Pulisciano, A; Palmer, R E, E-mail: R.E.Palmer@bham.ac.u [Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom)

2009-11-25

Secondary-electron emission (SEE) spectra have been obtained with the Scanning Probe Energy Loss Spectrometer at a tip-sample distance of only 50 nm. Such short working distances are required for the best theoretical spatial resolution (<10 nm). The SEE spectra of graphite, obtained as a function of tip bias voltage, are shown to correspond to unoccupied states in the electronic band structure. The SEE spectra of thin gold films demonstrate the capability of identifying (carbonaceous) surface contamination with this technique.

Study of the energy spectra of the major ion species in the ring-current region of the magnetosphere during geomagnetic storms

International Nuclear Information System (INIS)

Kistler, L.M.

1987-01-01

Using the University of Maryland/Max Planck Institute for Aeronomy Charge Energy Mass (CHEM) spectrometer on the AMPTE Charge Composition Explorer (CCE) spacecraft, the author examined the near-equatorial storm-time energy spectra of four major magnetospheric ions, H + , O + , He + , and He ++ over the energy range 1-300 keV/e in the L-range 3-6. The data were obtained during the main phase of all geomagnetic storms with minimum Dst less than -50 in the time period September 1984 to November 1985. During this period, the orbit of the CCE precessed such that the full range of local times was covered. When the spectra are organized by local time, certain features emerge. In particular, there is a dip in the spectra of all ions at 10-20 keV/e in the drawn-to-noon sector, while in the noon-to-dusk sector the proton distribution function drops off sharply below ∼5 keV. These spectra were compared with those predicted by a model of ion drift and loss in the magnetosphere. It was found that the spectra are most consistent with a Volland-Stern electric field with γ = 2 and with a rotation of the nominal dawn-to-dusk electric field eastward by two hours local time

Deconvolution of overlapping features in electron energy-loss spectra: the determination of absolute differential cross sections for electron-impact excitation of electronic states of molecules

International Nuclear Information System (INIS)

Campbell, L.; Brunger, M.J.; Teubner, O.J.P.; Mojarrabi, B.

1996-06-01

A set of three computer programs is reported which allow for the deconvolution of overlapping molecular electronic state structure in electron energy-loss spectra, even in highly perturbed systems. This procedure enables extraction of absolute differential cross sections for electron-impact excitation of electronic states of diatomic molecules from electron energy-loss spectra. The first code in the sequence uses the Rydberg-Klein-Rees procedure to generate potential energy curves from spectroscopic constants, while the second calculates Franck-Condon factors by numerical solution of the Schroedinger equation, given the potential energy curves. The third, given these Franck-Condon factors, the previously calculated relevant energies for the vibrational levels of the respective electronic states and the experimental energy-loss spectra, extracts the differential cross sections for each state. Each program can be run independently, or the three can run in sequence to determine these cross sections from the spectroscopic constants and the experimental energy-loss spectra. The application of these programs to the specific case of electron scattering from nitric oxide (NO) is demonstrated. 25 refs., 2 tabs., 2 figs

Systematics of gamma-ray energy spectra for classification of workplaces around a nuclear facility

International Nuclear Information System (INIS)

Urabe, Itsumasa; Tsujimoto, Tadashi; Katsurayama, Kousuke

1988-01-01

Radiation dosimetry in workplaces has been carried out both for assurance of the doses complying with the acceptable values and for improvement of protection methods to minimise detriments of the exposed population. This means that it is very important not only to determine dosimetric quantities in workplaces but also to know features of radiation levels because information for radiation protection can often be derived from the radiometric quantities. Classification of workplaces based on the feature of gamma-ray energy spectra is one of the practical ways to realise radiation protection being taken into consideration of the radiometric quantities. Furthermore, demarcation of workplaces based on these radiometric quantities may be effective for improvement of radiation protection practice such as estimation of radiation doses, designing of radiation shields and other activities. From these points of view, gamma-ray energy spectra have been determined in various workplaces in nuclear facilities, and systematics of gamma-ray fields were tried for classification of workplaces on the basis of the feature appeared in health physical quantities such as effective dose equivalents and responses of dosemeters

Accurate Quasiparticle Spectra from the T-Matrix Self-Energy and the Particle-Particle Random Phase Approximation.

Science.gov (United States)

Zhang, Du; Su, Neil Qiang; Yang, Weitao

2017-07-20

The GW self-energy, especially G 0 W 0 based on the particle-hole random phase approximation (phRPA), is widely used to study quasiparticle (QP) energies. Motivated by the desirable features of the particle-particle (pp) RPA compared to the conventional phRPA, we explore the pp counterpart of GW, that is, the T-matrix self-energy, formulated with the eigenvectors and eigenvalues of the ppRPA matrix. We demonstrate the accuracy of the T-matrix method for molecular QP energies, highlighting the importance of the pp channel for calculating QP spectra.

Measurement of very forward neutron energy spectra for 7 TeV proton--proton collisions at the Large Hadron Collider

CERN Document Server

Adriani, O.; Bonechi, L.; Bongi, M.; Castellini, G.; D'Alessandro, R.; Del Prete, M.; Haguenauer, M.; Itow, Y.; Kasahara, K.; Kawade, K.; Makino, Y.; Masuda, K.; Matsubayashi, E.; Menjo, H.; Mitsuka, G.; Muraki, Y.; Okuno, Y.; Papini, P.; Perrot, A-L.; Ricciarini, S.; Sako, T.; Sakurai, N.; Sugiura, Y.; Suzuki, T.; Tamura, T.; Tiberio, A.; Torii, S.; Tricomi, A.; Turner, W.C.; Zhou, Q.D.

2015-01-01

The Large Hadron Collider forward (LHCf) experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC $\\sqrt{s}$ = 7 TeV proton--proton collisions with the pseudo-rapidity $\\eta$ ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the difference in the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results and the DPMJET 3.04 model describes our results well at the lower pseudo-...

Large-scale kinetic energy spectra from Eulerian analysis of EOLE wind data

Science.gov (United States)

Desbois, M.

1975-01-01

A data set of 56,000 winds determined from the horizontal displacements of EOLE balloons at the 200 mb level in the Southern Hemisphere during the period October 1971-February 1972 is utilized for the computation of planetary- and synoptic-scale kinetic energy space spectra. However, the random distribution of measurements in space and time presents some problems for the spectral analysis. Two different approaches are used, i.e., a harmonic analysis of daily wind values at equi-distant points obtained by space-time interpolation of the data, and a correlation method using the direct measurements. Both methods give similar results for small wavenumbers, but the second is more accurate for higher wavenumbers (k above or equal to 10). The spectra show a maximum at wavenumbers 5 and 6 due to baroclinic instability and then decrease for high wavenumbers up to wavenumber 35 (which is the limit of the analysis), according to the inverse power law k to the negative p, with p close to 3.

Measurement of discrete energy-level spectra in individual chemically synthesized gold nanoparticles

DEFF Research Database (Denmark)

Kuemmeth, Ferdinand; Bolotin, Kirill I; Shi, Su-Fei

2008-01-01

We form single-electron transistors from individual chemically synthesized gold nanoparticles, 5-15 nm in diameter, with monolayers of organic molecules serving as tunnel barriers. These devices allow us to measure the discrete electronic energy levels of individual gold nanoparticles that are......, by virtue of chemical synthesis, well-defined in their composition, size and shape. We show that the nanoparticles are nonmagnetic and have spectra in good accord with random-matrix-theory predictions taking into account strong spin-orbit coupling....

Bumping structure of initial energy density distributions and peculiarities of pion spectra in A + A collisions

International Nuclear Information System (INIS)

Borysova, M.S.

2012-01-01

The effect of a fluctuating bumping structure of the initial conditions on spectra and the collective evolution of matter created in heavy-ion collisions in the frameworks of the Hydro-Kinetic Model is investigated. As motivated by the glasma-flux-tube scenario, the initial conditions are modeled by the set of four high energy-density tube-like fluctuations with longitudinally homogeneous structure within some space-rapidity region in a boost-invariant 2D geometry. It was found that the presence of transversally bumping tube-like fluctuations in initial conditions strongly affects the hydrodynamic evolution and leads to emergence of conspicuous structures in the calculated pion spectra. It was observed that the 4 tube initial configuration generates a four-peak structure in the final azimuthal distributions of one-particle spectra.

Testing electric field models using ring current ion energy spectra from the Equator-S ion composition (ESIC instrument

Directory of Open Access Journals (Sweden)

L. M. Kistler

Full Text Available During the main and early recovery phase of a geomagnetic storm on February 18, 1998, the Equator-S ion composition instrument (ESIC observed spectral features which typically represent the differences in loss along the drift path in the energy range (5–15 keV/e where the drift changes from being E × B dominated to being gradient and curvature drift dominated. We compare the expected energy spectra modeled using a Volland-Stern electric field and a Weimer electric field, assuming charge exchange along the drift path, with the observed energy spectra for H⁺ and O⁺. We find that using the Weimer electric field gives much better agreement with the spectral features, and with the observed losses. Neither model, however, accurately predicts the energies of the observed minima.

Key words. Magnetospheric physics (energetic particles trapped; plasma convection; storms and substorms

Quantitative analysis of reflection electron energy loss spectra to determine electronic and optical properties of Fe–Ni alloy thin films

International Nuclear Information System (INIS)

Tahir, Dahlang; Oh, Sukh Kun; Kang, Hee Jae; Tougaard, Sven

2016-01-01

Highlights: • Electronic and optical properties of Fe-Ni alloy thin films grown on Si (1 0 0) were studied via quantitative analyses of reflection electron energy loss spectra (REELS). • The energy loss functions (ELF) are dominated by a plasmon peak at 23.6 eV for Fe and moves gradually to lower energies in Fe-Ni alloys towards the bulk plasmon energy of Ni at 20.5 eV. • Fe has a strong effect on the dielectric and optical properties of Fe-Ni alloy thin films even for an alloy with 72% Ni. Electronic and optical properties of Fe-Ni alloy thin films grown on Si (1 0 0) were studied via quantitative analyses of reflection electron energy loss spectra (REELS). - Abstract: Electronic and optical properties of Fe–Ni alloy thin films grown on Si (1 0 0) by ion beam sputter deposition were studied via quantitative analyses of reflection electron energy loss spectra (REELS). The analysis was carried out by using the QUASES-XS-REELS and QUEELS-ε(k,ω)-REELS softwares to determine the energy loss function (ELF) and the dielectric functions and optical properties by analyzing the experimental spectra. For Ni, the ELF shows peaks around 3.6, 7.5, 11.7, 20.5, 27.5, 67 and 78 eV. The peak positions of the ELF for Fe_2_8Ni_7_2 are similar to those of Fe_5_1Ni_4_9, even though there is a small peak shift from 18.5 eV for Fe_5_1Ni_4_9 to 18.7 eV for Fe_2_8Ni_7_2. A plot of n, k, ε_1, and ε_2 shows that the QUEELS-ε(k,ω)-REELS software for analysis of REELS spectra is useful for the study of optical properties of transition metal alloys. For Fe–Ni alloy with high Ni concentration (Fe_2_8Ni_7_2), ε_1, and ε_2 have strong similarities with those of Fe. This indicates that the presence of Fe in the Fe–Ni alloy thin films has a strong effect.

Alpha-particle energy spectra measured at forward angles in heavy-ion-induced reactions

International Nuclear Information System (INIS)

Borcea, C.; Cierlic, E.; Kalpakchieva, R.; Oganessian, Yu.Ts.; Penionzhkevich, Yu.E.

1980-01-01

Energy spectra have been measured for α-particles emitted in the bombardment of 159 Tb, 181 Ta, 197 Au, and 232 Th nuclei by 20 Ne, 22 Ne, and 40 Ar projectiles. The reaction products emitted in the angular range (0+-2)deg relative to the beam direction were analyzed using a magnetic spectrometer and detected by means of a semiconductor ΔE-E telescope. It was found that in all cases the experimentally measured maximum α-particle energy almost amounts to the maximum possible value calculated from the reaction energy balance for a two-body exit channel. A correlation was found between the measured absolute cross section in different target-projectile combinations and the α-particle binding energy in the target nuclei. On the basis of the obtained results a conclusion has been drawn that the α-particles are emitted in the early stage of the reaction

Why is solar cycle 24 an inefficient producer of high-energy particle events?

Science.gov (United States)

Vainio, Rami; Raukunen, Osku; Tylka, Allan J.; Dietrich, William F.; Afanasiev, Alexandr

2017-08-01

Aims: The aim of the study is to investigate the reason for the low productivity of high-energy SEPs in the present solar cycle. Methods: We employ scaling laws derived from diffusive shock acceleration theory and simulation studies including proton-generated upstream Alfvén waves to find out how the changes observed in the long-term average properties of the erupting and ambient coronal and/or solar wind plasma would affect the ability of shocks to accelerate particles to the highest energies. Results: Provided that self-generated turbulence dominates particle transport around coronal shocks, it is found that the most crucial factors controlling the diffusive shock acceleration process are the number density of seed particles and the plasma density of the ambient medium. Assuming that suprathermal populations provide a fraction of the particles injected to shock acceleration in the corona, we show that the lack of most energetic particle events as well as the lack of low charge-to-mass ratio ion species in the present cycle can be understood as a result of the reduction of average coronal plasma and suprathermal densities in the present cycle over the previous one.

Nuclear Neutrino Spectra in Late Stellar Evolution

Science.gov (United States)

Misch, G. Wendell; Sun, Yang; Fuller, George

2018-05-01

Neutrinos are the principle carriers of energy in massive stars, beginning from core carbon burning and continuing through core collapse and after the core bounce. In fact, it may be possible to detect neutrinos from nearby pre-supernova stars. Therefore, it is of great interest to understand the neutrino energy spectra from these stars. Leading up to core collapse, beginning around core silicon burning, nuclei become dominant producers of neutrinos, particularly at high neutrino energy, so a systematic study of nuclear neutrino spectra is desirable. We have done such a study, and we present our sd-shell model calculations of nuclear neutrino energy spectra for nuclei in the mass number range A = 21 - 35. Our study includes neutrinos produced by charged lepton capture, charged lepton emission, and neutral current nuclear deexcitation. Previous authors have tabulated the rates of charged current nuclear weak interactions in astrophysical conditions, but the present work expands on this not only by providing neutrino energy spectra, but also by including the heretofore untabulated neutral current de-excitation neutrino pairs.

Kinetic energy spectra, vertical resolution and dissipation in high-resolution atmospheric simulations.

Science.gov (United States)

Skamarock, W. C.

2017-12-01

We have performed week-long full-physics simulations with the MPAS global model at 15 km cell spacing using vertical mesh spacings of 800, 400, 200 and 100 meters in the mid-troposphere through the mid-stratosphere. We find that the horizontal kinetic energy spectra in the upper troposphere and stratosphere does not converge with increasing vertical resolution until we reach 200 meter level spacing. Examination of the solutions indicates that significant inertia-gravity waves are not vertically resolved at the lower vertical resolutions. Diagnostics from the simulations indicate that the primary kinetic energy dissipation results from the vertical mixing within the PBL parameterization and from the gravity-wave drag parameterization, with smaller but significant contributions from damping in the vertical transport scheme and from the horizontal filters in the dynamical core. Most of the kinetic energy dissipation in the free atmosphere occurs within breaking mid-latitude baroclinic waves. We will briefly review these results and their implications for atmospheric model configuration and for atmospheric dynamics, specifically that related to the dynamics associated with the mesoscale kinetic energy spectrum.

Modeling of X-ray images and energy spectra produced by stepping lightning leaders

OpenAIRE

Xu , Wei; Marshall , Robert A.; Celestin , Sébastien; Pasko , Victor P.

2017-01-01

International audience; Recent ground-based measurements at the International Center for Lightning Research and Testing (ICLRT) have greatly improved our knowledge of the energetics, fluence, and evolution of X-ray emissions during natural cloud-to-ground (CG) and rocket-triggered lightning flashes. In this paper, using Monte Carlo simulations and the response matrix of unshielded detectors in the Thunderstorm Energetic Radiation Array (TERA), we calculate the energy spectra of X-rays as woul...

Correlations Between Variations in Solar EUV and Soft X-Ray Irradiance and Photoelectron Energy Spectra Observed on Mars and Earth

Science.gov (United States)

Peterson, W. K.; Brain, D. A.; Mitchell, D. L.; Bailey, S. M.; Chamberlin, P. C.

2013-01-01

Solar extreme ultraviolet (EUV; 10-120 nm) and soft X-ray (XUV; 0-10 nm) radiation are major heat sources for the Mars thermosphere as well as the primary source of ionization that creates the ionosphere. In investigations of Mars thermospheric chemistry and dynamics, solar irradiance models are used to account for variations in this radiation. Because of limited proxies, irradiance models do a poor job of tracking the significant variations in irradiance intensity in the EUV and XUV ranges over solar rotation time scales when the Mars-Sun-Earth angle is large. Recent results from Earth observations show that variations in photoelectron energy spectra are useful monitors of EUV and XUV irradiance variability. Here we investigate photoelectron energy spectra observed by the Mars Global Surveyor (MGS) Electron Reflectometer (ER) and the FAST satellite during the interval in 2005 when Earth, Mars, and the Sun were aligned. The Earth photoelectron data in selected bands correlate well with calculations based on 1 nm resolution observations above 27 nm supplemented by broadband observations and a solar model in the 0-27 nm range. At Mars, we find that instrumental and orbital limitations to the identifications of photoelectron energy spectra in MGS/ER data preclude their use as a monitor of solar EUV and XUV variability. However, observations with higher temporal and energy resolution obtained at lower altitudes on Mars might allow the separation of the solar wind and ionospheric components of electron energy spectra so that they could be used as reliable monitors of variations in solar EUV and XUV irradiance than the time shifted, Earth-based, F(10.7) index currently used.

Correlations between variations in solar EUV and soft X-ray irradiance and photoelectron energy spectra observed on Mars and Earth

Science.gov (United States)

Peterson, W. K.; Brain, D. A.; Mitchell, D. L.; Bailey, S. M.; Chamberlin, P. C.

2013-11-01

extreme ultraviolet (EUV; 10-120 nm) and soft X-ray (XUV; 0-10 nm) radiation are major heat sources for the Mars thermosphere as well as the primary source of ionization that creates the ionosphere. In investigations of Mars thermospheric chemistry and dynamics, solar irradiance models are used to account for variations in this radiation. Because of limited proxies, irradiance models do a poor job of tracking the significant variations in irradiance intensity in the EUV and XUV ranges over solar rotation time scales when the Mars-Sun-Earth angle is large. Recent results from Earth observations show that variations in photoelectron energy spectra are useful monitors of EUV and XUV irradiance variability. Here we investigate photoelectron energy spectra observed by the Mars Global Surveyor (MGS) Electron Reflectometer (ER) and the FAST satellite during the interval in 2005 when Earth, Mars, and the Sun were aligned. The Earth photoelectron data in selected bands correlate well with calculations based on 1 nm resolution observations above 27 nm supplemented by broadband observations and a solar model in the 0-27 nm range. At Mars, we find that instrumental and orbital limitations to the identifications of photoelectron energy spectra in MGS/ER data preclude their use as a monitor of solar EUV and XUV variability. However, observations with higher temporal and energy resolution obtained at lower altitudes on Mars might allow the separation of the solar wind and ionospheric components of electron energy spectra so that they could be used as reliable monitors of variations in solar EUV and XUV irradiance than the time shifted, Earth-based, F10.7 index currently used.

Energy spectra and E2 transition rates of 124—130Ba

Science.gov (United States)

Sabri, H.; Seidi, M.

2016-10-01

In this paper, we have studied the energy spectra and B(E2) values of 124—130Ba isotopes in the shape phase transition region between the spherical and gamma unstable deformed shapes. We have used a transitional interacting Boson model (IBM), Hamiltonian which is based on affine SU(1,1) Lie algebra in the both IBM-1 and 2 versions and also the Catastrophe theory in combination with a coherent state formalism to generate energy surfaces and determine the exact values of control parameters. Our results for control parameters suggest a combination of U(5) and SO(6) dynamical symmetries in this isotopic chain. Also, the theoretical predictions can be rather well reproduce the experimental counterparts, when the control parameter is approached to the SO(6) limit.

Energetic Proton Spectra Measured by the Van Allen Probes

Science.gov (United States)

Summers, Danny; Shi, Run; Engebretson, Mark J.; Oksavik, Kjellmar; Manweiler, Jerry W.; Mitchell, Donald G.

2017-10-01

We test the hypothesis that pitch angle scattering by electromagnetic ion cyclotron (EMIC) waves can limit ring current proton fluxes. For two chosen magnetic storms, during 17-20 March 2013 and 17-20 March 2015, we measure proton energy spectra in the region 3 ≤ L ≤ 6 using the RBSPICE-B instrument on the Van Allen Probes. The most intense proton spectra are observed to occur during the recovery periods of the respective storms. Using proton precipitation data from the POES (NOAA and MetOp) spacecraft, we deduce that EMIC wave action was prevalent at the times and L-shell locations of the most intense proton spectra. We calculate limiting ring current proton energy spectra from recently developed theory. Comparisons between the observed proton energy spectra and the theoretical limiting spectra show reasonable agreement. We conclude that the measurements of the most intense proton spectra are consistent with self-limiting by EMIC wave scattering.

RCI Simulation for EUV spectra from Sn ions

International Nuclear Information System (INIS)

Kagawa, T; Tanuma, H; Ohashi, H; Nishihara, K

2007-01-01

Using the relativistic-configuration-interaction atomic structure code, RCI simulations for EUV spectra from Sn 10+ , Sn 11+ and Sn 12+ ions are carried out, where it is assumed that each ion is embedded in a LTE plasma with the electron temperature of 30 eV. To make clear assignment of the measured spectra, the value of the excitation energy limit, which is introduced to limit the number of excited states in the simulation, is changed to see the excitation-energy-limit dependence of the spectral shape. The simulated spectra are obtained as a superposition of line intensities due to all possible transitions between two states whose excitation energy from the ground state is lower than the excitation energy limit assumed. The RCI simulated spectra are compared to the spectra measured with the chargeexchange- collision experiment in which a rare gas such as Xe or He as a target is bombarded by a charge-selected tin ion. Applicability of the LTE model to a decay model in the charge exchange collision experiment is also discussed

Transverse momentum spectra of hadrons in p + p collisions at CERN SPS energies from the UrQMD transport model

Science.gov (United States)

Ozvenchuk, V.; Rybicki, A.

2018-05-01

The UrQMD transport model, version 3.4, is used to study the new experimental data on transverse momentum spectra of π±, K±, p and p bar produced in inelastic p + p interactions at SPS energies, recently published by the NA61/SHINE Collaboration. The comparison of model predictions to these new measurements is presented as a function of collision energy for central and forward particle rapidity intervals. In addition, the inverse slope parameters characterizing the transverse momentum distributions are extracted from the predicted spectra and compared to the corresponding values obtained from NA61/SHINE distributions, as a function of particle rapidity and collision energy. A complex pattern of deviations between the experimental data and the UrQMD model emerges. For charged pions, the fair agreement visible at top SPS energies deteriorates with the decreasing energy. For charged K mesons, UrQMD significantly underpredicts positive kaon production at lower beam momenta. It also underpredicts the central rapidity proton yield at top collision energy and overpredicts antiproton production at all considered energies. We conclude that the new experimental data analyzed in this paper still constitute a challenge for the present version of the model.

Coda-derived source spectra, moment magnitudes and energy-moment scaling in the western Alps

Science.gov (United States)

Morasca, P.; Mayeda, K.; Malagnini, L.; Walter, William R.

2005-01-01

A stable estimate of the earthquake source spectra in the western Alps is obtained using an empirical method based on coda envelope amplitude measurements described by Mayeda et al. for events ranging between MW~ 1.0 and ~5.0. Path corrections for consecutive narrow frequency bands ranging between 0.3 and 25.0 Hz were included using a simple 1-D model for five three-component stations of the Regional Seismic network of Northwestern Italy (RSNI). The 1-D assumption performs well, even though the region is characterized by a complex structural setting involving strong lateral variations in the Moho depth. For frequencies less than 1.0 Hz, we tied our dimensionless, distance-corrected coda amplitudes to an absolute scale in units of dyne cm by using independent moment magnitudes from long-period waveform modelling for three moderate magnitude events in the region. For the higher frequencies, we used small events as empirical Green's functions, with corner frequencies above 25.0 Hz. For each station, the procedure yields frequency-dependent corrections that account for site effects, including those related to fmax, as well as to S-to-coda transfer function effects. After the calibration was completed, the corrections were applied to the entire data set composed of 957 events. Our findings using the coda-derived source spectra are summarized as follows: (i) we derived stable estimates of seismic moment, M0, (and hence MW) as well as radiated S-wave energy, (ES), from waveforms recorded by as few as one station, for events that were too small to be waveform modelled (i.e. events less than MW~ 3.5); (ii) the source spectra were used to derive an equivalent local magnitude, ML(coda), that is in excellent agreement with the network averaged values using direct S waves; (iii) scaled energy, , where ER, the radiated seismic energy, is comparable to results from other tectonically active regions (e.g. western USA, Japan) and supports the idea that there is a fundamental

Total bremsstrahlung spectra of thick lead compounds produced by {sup 90}Sr beta emitter in photon energy region of 10–100 keV

Energy Technology Data Exchange (ETDEWEB)

Sharma, Suhansar Jit [Department of Physics, B.B.S.B Polytechnic, Fatehgarh Sahib, Punjab (India); Singh, Tajinder, E-mail: tajindersingh2k9@gmail.com [Department of Physics, Mata Gujri College, Fatehgarh Sahib, Punjab (India); Singh, Doordarshi [Department of Mechanical Engineering, B.B.S.B Engineering College, Fatehgarh Sahib, Punjab (India); Singh, Amrit [Department of Physics, Baba Ajay Singh Khalsa College, Gurdas Nangal, Gurdaspur, Punjab (India); Dhaliwal, A.S. [Department of Physics, Sant Longowal Institute of Engineering & Technology, Longowal (Sangrur), Punjab (India)

2017-06-15

Highlights: • Total bremsstrahlung spectra in thick targets of Pb compounds by {sup 90}Sr in energy range 10–100 keV. • Experimental results show better agreement with the model which includes PB in SA up to 30 keV. • At higher photon energy region 30–100 keV the model which describes OB is more accurate. • Experimental results show positive deviations from the entire models at higher energy end spectrum. - Abstract: The total bremsstrahlung spectra in the thick targets of lead acetate trihydrate (Pb(CH{sub 3}COO){sub 2}·3H{sub 2}O), lead nitrate Pb(NO{sub 3}){sub 2} and lead chloride (PbCl{sub 2}) produced by {sup 90}Sr beta particles have been investigated in the photon energy region of 10–100 keV. The experimental bremsstrahlung spectra have been compared with the theoretical models Elwert corrected (non relativistic) Bethe Heitler theory, modified Elwert factor (relativistic) Bethe Heitler theory for ordinary bremsstrahlung and modified Elwert factor (relativistic) Bethe Heitler theory which includes polarization bremsstrahlung in the stripped atom approximation. The experimental results show better agreement with theoretical model that includes polarization bremsstrahlung in stripped approximation in the photon energy region below 30 keV. However, at higher photon energy region 30–100 keV, the theoretical model which describes ordinary bremsstrahlung is more accurate to describe the experimental bremsstrahlung spectra. The experimental results show positive deviations from the entire theoretical models at higher energy end of the spectrum. The results indicate that polarization bremsstrahlung plays important role in the formation of total bremsstrahlung spectra in lead compounds produced by continuous beta particles at low photon energy region of 10–30 keV.

Wavelength Detuning Cross-Beam Energy Transfer Mitigation Scheme for Direct-Drive: Modeling and Evidence from National Ignition Facility Implosions

Science.gov (United States)

Marozas, J. A.

2017-10-01

Cross-beam energy transfer (CBET) has been shown to significantly reduce the laser absorption and implosion speed in direct-drive implosion experiments on OMEGA and the National Ignition Facility (NIF). Mitigating CBET assists in achieving ignition-relevant hot-spot pressures in deuterium-tritium cryogenic OMEGA implosions. In addition, reducing CBET permits lower, more hydrodynamically stable, in-flight aspect ratio ignition designs with smaller nonuniformity growth during the acceleration phase. Detuning the wavelengths of the crossing beams is one of several techniques under investigation at the University of Rochester to mitigate CBET. This talk will describe these techniques with an emphasis on wavelength detuning. Recent experiments designed and predicted using multidimensional hydrodynamic simulations including CBET on the NIF have exploited the wavelength arrangement of the NIF beam geometry to demonstrate CBET mitigation through wavelength detuning in polar-direct-drive (PDD) implosions. Shapes and trajectories inferred from time-resolved x-ray radiography of the imploding shell, scattered-light spectra, and hard x-ray spectra generated by suprathermal electrons all indicate a reduction in CBET. These results and their implications for direct-drive ignition will be presented and discussed. In addition, hydrodynamically scaled ignition-relevant designs for OMEGA implosions exploiting wavelength detuning will be presented. Changes required to the OMEGA laser to permit wavelength detuning will be discussed. Future plans for PDD on the NIF including more-uniform implosions with CBET mitigation will be explored. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Measurement of neutron energy spectra for Eg=23.1 and 26.6 MeV mono-energetic photon induced reaction on natC using laser electron photon beam at NewSUBARU

Science.gov (United States)

Itoga, Toshiro; Nakashima, Hiroshi; Sanami, Toshiya; Namito, Yoshihito; Kirihara, Yoichi; Miyamoto, Shuji; Takemoto, Akinori; Yamaguchi, Masashi; Asano, Yoshihiro

2017-09-01

Photo-neutron energy spectra for Eg=23.1 and 26.6 MeV mono-energetic photons on natC were measured using laser Compton scattering facility at NewSUBARU BL01. The photon energy spectra were evaluated through measurements and simulations with collimator sizes and arrangements for the laser electron photon. The neutron energy spectra for the natC(g,xn) reaction were measured at 60 degrees in horizontal and 90 degrees in horizontal and vertical with respect to incident photon. The spectra show almost isotropic angular distribution and flat energy distribution from detection threshold to upper limit defined by reaction Q-value.

Independent component analysis: A new possibility for analysing series of electron energy loss spectra

International Nuclear Information System (INIS)

Bonnet, Nogl; Nuzillard, Danielle

2005-01-01

A complementary approach is proposed for analysing series of electron energy-loss spectra that can be recorded with the spectrum-line technique, across an interface for instance. This approach, called blind source separation (BSS) or independent component analysis (ICA), complements two existing methods: the spatial difference approach and multivariate statistical analysis. The principle of the technique is presented and illustrations are given through one simulated example and one real example

ITER Plasma at Electron Cyclotron Frequency Domain: Stimulated Raman Scattering off Gould-Trivelpiece Modes and Generation of Suprathermal Electrons and Energetic Ions

Science.gov (United States)

Stefan, V. Alexander

2011-04-01

Stimulated Raman scattering in the electron cyclotron frequency range of the X-Mode and O-Mode driver with the ITER plasma leads to the ``tail heating'' via the generation of suprathermal electrons and energetic ions. The scattering off Trivelpiece-Gould (T-G) modes is studied for the gyrotron frequency of 170GHz; X-Mode and O-Mode power of 24 MW CW; on-axis B-field of 10T. The synergy between the two-plasmon decay and Raman scattering is analyzed in reference to the bulk plasma heating. Supported in part by Nikola TESLA Labs, La Jolla, CA

Photon energy dependent intensity variations observed in Auger spectra of free argon clusters

International Nuclear Information System (INIS)

Lundwall, M; Lindblad, A; Bergersen, H; Rander, T; Oehrwall, G; Tchaplyguine, M; Peredkov, S; Svensson, S; Bjoerneholm, O

2006-01-01

Photon energy dependent intensity variations are experimentally observed in the L 2,3 M 2,3 M 2,3 Auger spectra of argon clusters. Two cluster sizes are examined in the present study. Extrinsic scattering effects, both elastic and inelastic, involving the photoelectron are discussed and suggested as the explanation of the variations in the Auger signal. The atoms in the first few coordination shells surrounding the core-ionized atom are proposed to be the main targets for the scattering processes

Distortions in power spectra of digitized signals - II: Suggested solution

International Nuclear Information System (INIS)

Njau, E.C.

1982-04-01

In Part I of this report we developed analytical expressions which represent exactly the energy density spectra of ''digitization processes'' that are essentially involved in spectral analysis of continuous signals. Besides, we related the spectral energy density of each digitization process to the parameters of the exact spectral energy density of the corresponding signal. On this basis, we briefly discussed the forms of distortions (or false structures) which are present in normally computed power spectra when the corresponding spectra of the digitization processes are not sufficiently decoupled from or nullified in the computed spectra. The biggest worry with regard to these distortions is not only that they may mask the actual information contained in the original signal, but also they may tempt the researcher to establish false characteristics about the signal involved. It is, in this context, that any reasonable method that could be used (even conditionally) to pinpoint false structures in computed power spectra would be both timely and useful. A simple, handy guidance through which some portions of computed energy density spectra which are dominated by the false structures mentioned above, can be located is presented herein. Equations are presented which give the various frequencies at which false peaks may be located in such ''contaminated'' portions of computed energy density spectra. The occurrence of frequency shifts in computed power spectra is also briefly discussed. (author)

Accurate atom-solid kinetic energy shifts from the simultaneous measurement of the KLL Auger spectra for Na, Mg, Al and Si

International Nuclear Information System (INIS)

Aksela, S; Turunen, P; Kantia, T; Aksela, H

2011-01-01

KLL Auger-energy shifts between free atoms and their solid surfaces were determined from spectra measured simultaneously in identical experimental conditions. Essentially, the shift values obtained for Na, Mg, Al and Si were more accurate than those achieved by combining the results from separate vapour and solid measurements. Using atomic Auger energies and determined shifts, reliable absolute solid state Auger energies with respect to the vacuum level were also obtained. Experimental shift values were also compared with calculations obtained with the excited atom model. 2s and 2p binding energy shifts were estimated from recent high resolution and due to open shell strongly split vapour phase spectra and corresponding published solid state results. Also, the question of the extent to which the 2s and 2p shifts deviate has been discussed here. (paper)

Analytic and numerical calculations of quantum synchrotron spectra from relativistic electron distributions

International Nuclear Information System (INIS)

Brainerd, J.J.; Petrosian, V.

1987-01-01

Calculations are performed numerically and analytically of synchrotron spectra for thermal and power-law electron distributions using the single-particle synchrotron power spectrum derived from quantum electrodynamics. It is found that the photon energy at which quantum effects appear is proportional to temperature and independent of field strength for thermal spectra; quantum effects introduce an exponential roll-off away from the classical spectra. For power law spectra, the photon energy at which quantum effects appear is inversely proportional to the magnetic field strength; quantum effects produce a steeper power law than is found classically. The results are compared with spectra derived from the classical power spectrum with an energy cutoff ensuring conservation of energy. It is found that an energy cutoff is generally an inadequate approximation of quantum effects for low photon energies and for thermal spectra, but gives reasonable results for high-energy emission from power-law electron distributions. 17 references

Effect of isospin degree of freedom on transverse momentum spectra

International Nuclear Information System (INIS)

Kaur, Sukhjit; Swati

2013-01-01

We study the effect of isospin degree of freedom, incident energy as well as system mass on the behavior of transverse momentum spectra, dN/p t dp t , of neutrons and protons. We find that most of the nucleons suffer soft collisions. The effect of isospin degree of freedom on transverse spectra diminishes with the increase in the incident energy. In Fermi energy region, transverse momentum spectra of both protons and neutrons show sensitivity toward the density dependence of symmetry energy. (author)

Resonance spin memory in low-energy gamma-ray spectra from Sb, Tb, Ho and Ta odd-odd compound nuclei

International Nuclear Information System (INIS)

Olejniczak, U.; Gundorin, N.A.; Pikelner, L.B.; Serov, D.G.; Przytula, M.

2002-01-01

The low-energy gamma-ray spectra from neutron resonance capture with natural samples of Sb, Tb, Ho and Ta were measured using a HPGe detector at the IBR-30 pulsed reactor (JINR, Dubna). The resonance spin memory effect in the spectra from the odd-odd compound nuclei of 122 Sb, 160 Tb and 166 Ho was found to be quite distinct. For the 182 Ta compound nucleus it proved to be rather weak

Measurement of neutron energy spectra for Eg=23.1 and 26.6 MeV mono-energetic photon induced reaction on natC using laser electron photon beam at NewSUBARU

Directory of Open Access Journals (Sweden)

Itoga Toshiro

2017-01-01

Full Text Available Photo-neutron energy spectra for Eg=23.1 and 26.6 MeV mono-energetic photons on natC were measured using laser Compton scattering facility at NewSUBARU BL01. The photon energy spectra were evaluated through measurements and simulations with collimator sizes and arrangements for the laser electron photon. The neutron energy spectra for the natC(g,xn reaction were measured at 60 degrees in horizontal and 90 degrees in horizontal and vertical with respect to incident photon. The spectra show almost isotropic angular distribution and flat energy distribution from detection threshold to upper limit defined by reaction Q-value.

Galactic Cosmic-Ray Energy Spectra and Composition during the 2009-2010 Solar Minimum Period

Science.gov (United States)

Lave, K. A.; Wiedenbeck, Mark E.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Israel, M. H..; Leske, R. A.; Mewaldt, R. A.;

Conductance spectra of asymmetric ferromagnet/ferromagnet/ferromagnet junctions

Energy Technology Data Exchange (ETDEWEB)

Pasanai, K., E-mail: krisakronmsu@gmail.com

2017-01-15

A theory of tunneling spectroscopy of ferromagnet/ferromagnet/ferromagnet junctions was studied. We applied a delta-functional approximation for the interface scattering properties under a one-dimensional system of a free electron approach. The reflection and transmission probabilities were calculated in the ballistic regime, and the conductance spectra were then calculated using the Landauer formulation. The magnetization directions were set to be either parallel (P) or anti-parallel (AP) alignments, for comparison. We found that the conductance spectra was suppressed when increasing the interfacial scattering at the interfaces. Moreover, the electron could exhibit direct transmission when the thickness was rather thin. Thus, there was no oscillation in this case. However, in the case of a thick layer the conductance spectra oscillated, and this oscillation was most prominent when the middle layer thickness increased. In the case of direct transmission, the conductance spectra of P and AP systems were definitely suppressed with increased exchange energy of the middle ferromagnet. This also refers to an increase in the magnetoresistance of the junction. In the case of oscillatory behavior, the positions of the resonance peaks were changed as the exchange energy was changed. - Highlights: • The conductance spectra of a FM/FM/FM junction were calculated. • The conductance spectra were suppressed by the exchange energy. • The exchange energy and the potential strength play similar roles in the junctions.

Conductance spectra of asymmetric ferromagnet/ferromagnet/ferromagnet junctions

International Nuclear Information System (INIS)

Pasanai, K.

2017-01-01

A theory of tunneling spectroscopy of ferromagnet/ferromagnet/ferromagnet junctions was studied. We applied a delta-functional approximation for the interface scattering properties under a one-dimensional system of a free electron approach. The reflection and transmission probabilities were calculated in the ballistic regime, and the conductance spectra were then calculated using the Landauer formulation. The magnetization directions were set to be either parallel (P) or anti-parallel (AP) alignments, for comparison. We found that the conductance spectra was suppressed when increasing the interfacial scattering at the interfaces. Moreover, the electron could exhibit direct transmission when the thickness was rather thin. Thus, there was no oscillation in this case. However, in the case of a thick layer the conductance spectra oscillated, and this oscillation was most prominent when the middle layer thickness increased. In the case of direct transmission, the conductance spectra of P and AP systems were definitely suppressed with increased exchange energy of the middle ferromagnet. This also refers to an increase in the magnetoresistance of the junction. In the case of oscillatory behavior, the positions of the resonance peaks were changed as the exchange energy was changed. - Highlights: • The conductance spectra of a FM/FM/FM junction were calculated. • The conductance spectra were suppressed by the exchange energy. • The exchange energy and the potential strength play similar roles in the junctions.

Theoretical photoionization spectra in the UV photon energy range for a Mg-like Al+ ion

International Nuclear Information System (INIS)

Kim, Dae-Soung; Kim, Young Soon

2008-01-01

In the present work, we report the photoionization cross sections of the Al + ion calculated for the photon energy range 20-26 eV and 30-50 eV. We have expanded our previous calculation (2007 J. Phys. Soc. Japan 76 014302) with an optimized admixture of the initial ground state 3s 21 S and exited states 3s3p 1,3 P, 3s3d 1,3 D and 3s4s 1,3 S, and obtained significantly improved predictions for the main background and autoionizing resonance structures of the reported experimental spectra. The absolute measurements of the photoionization cross sections of the Al + ion in these energy ranges have been performed by West et al (2001 Phys. Rev. A 63 052719), and they reported that the prominent peaks around 21 eV were attributed to the effects of the significant influence of the small fraction of the fourth-order radiation with energies around 84 eV from the synchrotron source. In our previous work, the main shape for these cross sections was calculated assuming an admixture of initial 3s 21 S and 3s3p 3 P states, only with a rough overall estimate for the experimental spectra in the photon energy range 20-26 eV, and without these peaks around 21 eV. The report of the experimental assignment attributes these peaks to the excitation of a 2p electron from the core. However, our present results with the new admixture reveal similar peaks without considering the possibility of the core excitation

Differential dpa calculations with SPECTRA-PKA

Science.gov (United States)

Gilbert, M. R.; Sublet, J.-Ch.

2018-06-01

The processing code SPECTRA-PKA produces energy spectra of primary atomic recoil events (or primary knock-on atoms, PKAs) for any material composition exposed to an irradiation spectrum. Such evaluations are vital inputs for simulations aimed at understanding the evolution of damage in irradiated material, which is generated in cascade displacement events initiated by PKAs. These PKA spectra present the full complexity of the input (to SPECTRA-PKA) nuclear data-library evaluations of recoil events. However, the commonly used displacements per atom (dpa) measure, which is an integral measure over all possible recoil events of the displacement damage dose, is still widely used and has many useful applications - as both a comparative and correlative quantity. This paper describes the methodology employed that allows the SPECTRA-PKA code to evaluate dpa rates using the energy-dependent recoil (PKA) cross section data used for the PKA distributions. This avoids the need for integral displacement kerma cross sections and also provides new insight into the relative importance of different reaction channels (and associated different daughter residual and emitted particles) to the total integrated dpa damage dose. Results are presented for Fe, Ni, W, and SS316. Fusion dpa rates are compared to those in fission, highlighting the increased contribution to damage creation in the former from high-energy threshold reactions.

Simulations of the neutron energy-spectra at the Olympus Gate Environmental Monitoring Station due to historical Bevatron operations

International Nuclear Information System (INIS)

Donahue, R.J.; Thomas, R.H.; Zeman, G.H.

2001-01-01

Offsite neutron fluences resulting from Bevatron operations reached a maximum in 1959, prior to the addition of a permanent concrete roof shield, which was constructed in 1962. From the first operation of the Bevatron measurements of neutron fluence were made at locations around the perimeter of the Lawrence Berkeley National Laboratory (LBNL) campus. Since the late 1950's measurements made at several locations, and particularly at the site of what is now called the Olympus Gate Environmental Monitoring Station, have been routinely reported and published. Early measurements were used to establish the shape of the neutron-energy spectrum from which an energy-averaged fluence-to-dose equivalent conversion coefficient could be derived. This conversion coefficient was then applied to a measured total neutron fluence to obtain the appropriate dose equivalent quantity required by regulation. Recent work by Thomas et al. (2000) have compared the early conversion coefficients used in the sixties with those accepted today and suggest suggested that ''the dose equivalents reported in the late fifties and early sixties were conservative by factors between two and four. In any current review of the historical data, therefore it would be prudent to reduce the reported dose equivalents by at least a factor of two.'' However, that analysis was based on the ''state of the art'' neutron energy-spectra of the '60s. This paper provides a detailed knowledge of the neutron energy spectrum at the site boundary paper thus removing any uncertainty in the analysis of Thomas et al., which might be caused by the use of the early neutron energy-spectra. Detailed Monte Carlo analyses of the interactions of 6.2 GeV protons in thick, medium-A targets are described. In the computer simulations, neutrons produced were allowed to scatter in the atmosphere. Detailed neutron energy spectra were calculated at a distance and elevation corresponding to the location of the Olympus Gate EMS. Both older

Gamma-ray Output Spectra from 239 Pu Fission

International Nuclear Information System (INIS)

Ullmann, John

2015-01-01

Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239 Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-ray multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution

Correction of measured charged-particle spectra for energy losses in the target - A comparison of three methods

CERN Document Server

Soederberg, J; Alm-Carlsson, G; Olsson, N

2002-01-01

The experimental facility, MEDLEY, at the The Svedberg Laboratory in Uppsala, has been constructed to measure neutron-induced charged-particle production cross-sections for (n, xp), (n, xd), (n, xt), (n, x sup 3 He) and (n, x alpha) reactions at neutron energies up to 100 MeV. Corrections for the energy loss of the charged particles in the target are needed in these measurements, as well as for loss of particles. Different approaches have been used in the literature to solve this problem. In this work, a stripping method is developed, which is compared with other methods developed by Rezentes et al. and Slypen et al. The results obtained using the three codes are similar and they could all be used for correction of experimental charged-particle spectra. Statistical fluctuations in the measured spectra cause problems independent of the applied technique, but the way to handle it differs in the three codes.

Numerical and Experimental Identification of Seven-Wire Strand Tensions Using Scale Energy Entropy Spectra of Ultrasonic Guided Waves

Directory of Open Access Journals (Sweden)

Ji Qian

2018-01-01

Full Text Available Accurate identification of tension in multiwire strands is a key issue to ensure structural safety and durability of prestressed concrete structures, cable-stayed bridges, and hoist elevators. This paper proposes a method to identify strand tensions based on scale energy entropy spectra of ultrasonic guided waves (UGWs. A numerical method was first developed to simulate UGW propagation in a seven-wire strand, employing the wavelet transform to extract UGW time-frequency energy distributions for different loadings. Mode separation and frequency band loss of L(0,1 were then found for increasing tension, and UGW scale energy entropy spectra were extracted to establish a tension identification index. A good linear relationship was found between the proposed identification index and tensile force, and effects of propagation distance and propagation path were analyzed. Finally, UGWs propagation was examined experimentally for a long seven-wire strand to investigate attenuation and long distance propagation. Numerical and experimental results verified that the proposed method not only can effectively identify strand tensions but can also adapt to long distance tests for practical engineering.

Application of direct peak analysis to energy dispersive x-ray fluorescence spectra

International Nuclear Information System (INIS)

Nielson, K.K.

1977-07-01

A modified Covell method for direct peak analysis has been applied to energy dispersive x-ray fluorescence spectra. The method is background independent and is well-suited to computerized data reduction. It provides acceptable precision, minimizes errors from instrumental gain shift, and permits peak overlap correction. Peak overlap errors exhibit both positive and negative nodes as a function of peak separation distance, and are corrected using concentration ratios determined from thin, single-element standards. Peak precisions and overlaps are evaluated as a function of window width to aid in width selection. Least-square polynomial smoothing prior to peak analysis significantly improves peak area precisions without significantly affecting their accuracies

Absorption spectra of AA-stacked graphite

International Nuclear Information System (INIS)

Chiu, C W; Lee, S H; Chen, S C; Lin, M F; Shyu, F L

2010-01-01

AA-stacked graphite shows strong anisotropy in geometric structures and velocity matrix elements. However, the absorption spectra are isotropic for the polarization vector on the graphene plane. The spectra exhibit one prominent plateau at middle energy and one shoulder structure at lower energy. These structures directly reflect the unique geometric and band structures and provide sufficient information for experimental fitting of the intralayer and interlayer atomic interactions. On the other hand, monolayer graphene shows a sharp absorption peak but no shoulder structure; AA-stacked bilayer graphene has two absorption peaks at middle energy and abruptly vanishes at lower energy. Furthermore, the isotropic features are expected to exist in other graphene-related systems. The calculated results and the predicted atomic interactions could be verified by optical measurements.

Statistical theory for calculating energy spectra of β-delayed neutrons

International Nuclear Information System (INIS)

Kawano, Toshihiko; Moeller, Peter; Wilson, William B.

2008-01-01

Theoretical β-delayed neutron spectra are calculated based on the Quasi-particle Random Phase Approximation (QRPA) and the Hauser-Feshbach statistical model. Neutron emissions from an excited daughter nucleus after β-decay to the granddaughter residual are more accurately calculated than previous evaluations, including all the microscopic nuclear structure information, such as a Gamow-Teller strength distribution and discrete states in the granddaughter. The calculated delayed-neutron spectra reasonably agree with those evaluations in the ENDF decay library, which are based on experimental data. The model was adopted to generate the delayed-neutron spectra for all 271 precursors. (authors)

Quantum synchrotron spectra from semirelativistic electrons in teragauss magnetic fields

International Nuclear Information System (INIS)

Brainerd, J.J.

1987-01-01

Synchrotron spectra are calculated from quantum electrodynamic transition rates for thermal and power-law electron distributions. It is shown that quantum effects appear in thermal spectra when the photon energy is greater than the electron temperature, and in power-law spectra when the electron energy in units of the electron rest mass times the magnetic field strength in units of the critical field strength is of order unity. These spectra are compared with spectra calculated from the ultrarelativistic approximation for synchrotron emission. It is found that the approximation for the power-law spectra is good, and the approximation for thermal spectra produces the shape of the spectrum accurately but fails to give the correct normalization. Single photon pair creation masks the quantum effects for power-law distributions, so only modifications to thermal spectra are important for gamma-ray bursts. 13 references

Moments, magnitudes, and radiated energies of non-volcanic tremor near Cholame, CA, from ground motion spectra at UPSAR

Science.gov (United States)

Fletcher, J. B.; McGarr, A.

2011-08-01

By averaging the spectra of events within two episodes of tremor (on Jan. 21 and 24, 2005) across the 12 stations of UPSAR, we improved the S/N sufficiently to define source spectra. Analysis of eleven impulsive events revealed attenuation-corrected spectra of displacement similar to those of earthquakes, with a low-frequency plateau, a corner frequency, and a high frequency decay proportional to f-2. Seismic moments, M0, estimated from these spectra range from about 3 to 10 × 1011 N-m or moment magnitudes in the range 1.6 to 1.9. The corner frequencies range from 2.6 to 7.2 Hz and, if interpreted in the same way as for earthquakes, indicate low stress drops that vary from 0.001 to 0.04 MPa. Seismic energies, estimated from the ground motion spectra, vary from 0.2 × 105 to 4.4 × 105 J, or apparent stresses in the range 0.002 to 0.02 MPa. The low stress parameters are consistent with a weak fault zone in the lower crust at the depth of tremor. In contrast, the same analysis on a micro-earthquake, located near Cholame (depth = 10.3 km), revealed a stress drop of 0.5 MPa and an apparent stress of 0.02 MPa. Residual spectra from ω-2 model fits to the displacement spectra of the non-volcanic tremor events show peaks near 4 Hz that are not apparent in the spectra for the microearthquake nor for the spectrum of earth noise. These spectral peaks may indicate that tremor entails more than shear failure reminiscent of mechanisms, possibly entailing fluid flow, associated with volcanic tremor or deep volcanic earthquakes.

Optical properties and energy spectra of donors in Gasub(x)Insub(1-x)P

International Nuclear Information System (INIS)

Berndt, V.; Kopylov, A.A.; Pikhtin, A.N.

1977-01-01

Impurity optical absorption is studied in n-Gasub(x)Insub(1-x)P for compositions with indirect band structure. For the first time the photoionization bands of shallow donor centers have been observed in semiconductor solid solutions. Analysis of spectra has shown the electron transitions to excited states of donor to contribute considerably to absorption. A simple theoretical model is presented to explain the shift of ionization energy of silicon donor and the variation in shape of the impurity absorption band

Displacement cross sections and PKA spectra: tables and applications

International Nuclear Information System (INIS)

Doran, D.G.; Graves, N.J.

1976-12-01

Damage energy cross sections to 20 MeV are given for aluminum, vanadium, chromium, iron, nickel, copper, zirconium, niobium, molybdenum, tantalum, tungsten, lead, and 18Cr10Ni stainless steel. They are based on ENDF/B-IV nuclear data and the Lindhard energy partition model. Primary knockon atom (PKA) spectra are given for aluminum, iron, niobium, tantalum, and lead for neutron energies up to 15 MeV at approximately one-quarter lethargy intervals. The contributions of various reactions to both the displacement cross sections (taken to be proportional to the damage energy cross sections) and the PKA spectra are presented graphically. Spectral-averaged values of the displacement cross sections are given for several spectra, including approximate maps for the Experimental Breeder Reactor-II (EBR-II) and several positions in the Fast Test Reactor (FTR). Flux values are included to permit estimation of displacement rates. Graphs show integral PKA spectra for the five metals listed above for neutron spectra corresponding to locations in the EBR-II, the High Flux Isotope Reactor (HFIR), and a conceptual fusion reactor (UWMAK-I). Detailed calculations are given only for cases not previously documented. Uncertainty estimates are included

Statistical analysis of suprathermal electron drivers at 67P/Churyumov-Gerasimenko

Science.gov (United States)

Broiles, Thomas W.; Burch, J. L.; Chae, K.; Clark, G.; Cravens, T. E.; Eriksson, A.; Fuselier, S. A.; Frahm, R. A.; Gasc, S.; Goldstein, R.; Henri, P.; Koenders, C.; Livadiotis, G.; Mandt, K. E.; Mokashi, P.; Nemeth, Z.; Odelstad, E.; Rubin, M.; Samara, M.

2016-11-01

We use observations from the Ion and Electron Sensor (IES) on board the Rosetta spacecraft to study the relationship between the cometary suprathermal electrons and the drivers that affect their density and temperature. We fit the IES electron observations with the summation of two kappa distributions, which we characterize as a dense and warm population (˜10 cm-3 and ˜16 eV) and a rarefied and hot population (˜0.01 cm-3 and ˜43 eV). The parameters of our fitting technique determine the populations' density, temperature, and invariant kappa index. We focus our analysis on the warm population to determine its origin by comparing the density and temperature with the neutral density and magnetic field strength. We find that the warm electron population is actually two separate sub-populations: electron distributions with temperatures above 8.6 eV and electron distributions with temperatures below 8.6 eV. The two sub-populations have different relationships between their density and temperature. Moreover, the two sub-populations are affected by different drivers. The hotter sub-population temperature is strongly correlated with neutral density, while the cooler sub-population is unaffected by neutral density and is only weakly correlated with magnetic field strength. We suggest that the population with temperatures above 8.6 eV is being heated by lower hybrid waves driven by counterstreaming solar wind protons and newly formed, cometary ions created in localized, dense neutral streams. To the best of our knowledge, this represents the first observations of cometary electrons heated through wave-particle interactions.

Quasi-monoenergetic neutron energy spectra for 246 and 389 MeV (7)Li(p,n) reactions at angles from 0 degrees to 300 degrees

CERN Document Server

Iwamoto, Y; Nakamura, T; Nakashima, H; Mares, V; Itoga, T; Matsumoto, T; Nakane, Y; Feldbaumer, E; Jaegerhofer, L; Pioch, C; Tamii, A; Satoh, D; Masuda, A; Sato, T; Iwase, H; Yashima, H; Nishiyama, J; Hagiwara, M; Hatanaka, K; Sakamoto, Y

2011-01-01

The authors measured the neutron energy spectra of a quasi-monoenergetic (7)Li(p,n) neutron source with 246 and 389 MeV protons set at seven angles (0 degrees, 2.5 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees and 30 degrees), using a time-of-flight (TOF) method employing organic scintillators NE213 at the Research Center for Nuclear Physics (RCNP) of Osaka University. The energy spectra of the source neutrons were precisely deduced down to 2 MeV at 0 degrees and 10 MeV at other angles. The cross-sections of the peak neutron production reaction at 0 degrees were on the 35-40 mb line of other experimental data, and the peak neutron angular distribution agreed well with the Taddeucci formula. Neutron energy spectra below 100 MeV at all angles were comparable, but the shapes of the continuum above 150 MeV changed considerably with the angle. In order to consider the correction required to derive the response in the peak region from the measured total response for high-energy neutron monitors such as DAR...

Neutron Energy Spectra from Neutron Induced Fission of 235U at 0.95 MeV and of 238U at 1.35 and 2.02 MeV

Energy Technology Data Exchange (ETDEWEB)

Almen, E; Holmqvist, B; Wiedling, T

1971-09-15

The shapes of fission neutron spectra are of interest for power reactor calculations. Recently it has been suggested that the neutron induced fission spectrum of 235U may be harder than was earlier assumed. For this reason measurements of the neutron spectra of some fissile isotopes are in progress at our laboratory. This report will present results from studies of the energy spectra of the neutrons emitted in the neutron induced fission of 235U and 238U. The measurements were performed at an incident neutron energy of 0.95 MeV for 235U and at energies of 1.35 and 2.02 MeV for 238U using time-of-flight techniques. The time-of-flight spectra were only analysed at energies higher than those of the incident neutrons and up to about 10 MeV. Corrections for neutron attenuation in the uranium samples were calculated using a Monte Carlo program. The corrected fission neutron spectra were fitted to Maxwellian temperature distributions. For 235U a temperature of 1.27 +- 0.01 MeV gives the best fit to the experimental data and for 238U the corresponding values are 1.29 +- 0.03 MeV at 1.35 MeV and 1.29 +- 0.02 MeV at 2.02 MeV

Double photoionisation spectra of molecules

CERN Document Server

Eland, John

2017-01-01

This book contains spectra of the doubly charged positive ions (dications) of some 75 molecules, including the major constituents of terrestrial and planetary atmospheres and prototypes of major chemical groups. It is intended to be a new resource for research in all areas of molecular spectroscopy involving high energy environments, both terrestrial and extra-terrestrial. All the spectra have been produced by photoionisation using laboratory lamps or synchrotron radiation and have been measured using the magnetic bottle time-of-flight technique by coincidence detection of correlated electron pairs. Full references to published work on the same species are given, though for several molecules these are the first published spectra. Double ionisation energies are listed and discussed in relation to the molecular electronic structure of the molecules. A full introduction to the field of molecular double ionisation is included and the mechanisms by which double photoionisation can occur are examined in detail. A p...

Energy Dispersion in Solar Ion Events over 4 Orders of Magnitude: SOHO/COSTEP and Wind/STICS

Science.gov (United States)

Kunow, Horst W.; Posner, A.

2003-07-01

The ma jority of solar particle events in the COSTEP observational range of 4 75 MeV/n reveals nucleon energy disp ersion (NED), implying a flare-associated particle acceleration mechanism. Towards lower energies, the situation changes somewhat. Only in a minority of solar energetic particle (SEP) events can the effect of NED be followed into the lower keV range. We analyse the reasons for the distinctly different types of particle transport of >10 keV suprathermal up to 100 MeV energetic ions and conclude that the mean free path depends on rigidity.

The troposphere-to-stratosphere transition in kinetic energy spectra and nonlinear spectral fluxes as seen in ECMWF analyses

Science.gov (United States)

Burgess, A. B. H.; Erler, A. R.; Shepherd, T. G.

2012-04-01

We present spectra, nonlinear interaction terms, and fluxes computed for horizontal wind fields from high-resolution meteorological analyses made available by ECMWF for the International Polar Year. Total kinetic energy spectra clearly show two spectral regimes: a steep spectrum at large scales and a shallow spectrum in the mesoscale. The spectral shallowing appears at ~200 hPa, and is due to decreasing rotational power with height, which results in the shallower divergent spectrum dominating in the mesoscale. The spectra we find are steeper than those observed in aircraft data and GCM simulations. Though the analyses resolve total spherical harmonic wavenumbers up to n = 721, effects of dissipation on the fluxes and spectra are visible starting at about n = 200. We find a weak forward energy cascade and a downscale enstrophy cascade in the mesoscale. Eddy-eddy nonlinear kinetic energy transfers reach maximum amplitudes at the tropopause, and decrease with height thereafter; zonal mean-eddy transfers dominate in the stratosphere. In addition, zonal anisotropy reaches a minimum at the tropopause. Combined with strong eddy-eddy interactions, this suggests flow in the tropopause region is very active and bears the greatest resemblance to isotropic turbulence. We find constant enstrophy flux over a broad range of wavenumbers around the tropopause and in the upper stratosphere. A relatively constant spectral enstrophy flux at the tropopause suggests a turbulent inertial range, and that the enstrophy flux is resolved. A main result of our work is its implications for explaining the shallow mesoscale spectrum observed in aircraft wind measurements, GCM studies, and now meteorological analyses. The strong divergent component in the shallow mesoscale spectrum indicates unbalanced flow, and nonlinear transfers decreasing quickly with height are characteristic of waves, not turbulence. Together with the downscale flux of energ y through the shallow spectral range, these

Time-resolved suprathermal x-rays

International Nuclear Information System (INIS)

Lee, P.H.Y.; Rosen, M.D.

1978-01-01

Temporally resolved x-ray spectra in the range of 1 to 20 keV have been obtained from gold disk targets irradiated by 1.06 μm laser pulses from the Argus facility. The x-ray streak camera used for the measurement has been calibrated for streak speed and dynamic range by using an air-gap Fabry-Perot etalon, and the instrument response has been calibrated using a multi-range monoenergetic x-ray source. The experimental results indicate that we are able to observe the ''hot'' x-ray temperature evolve in time and that the experimentally observed values can be qualitatively predicted by LASNEX code computations when the inhibited transport model is used

The spanwise spectra in wall-bounded turbulence

Science.gov (United States)

Wang, Hong-Ping; Wang, Shi-Zhao; He, Guo-Wei

2018-06-01

The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation (DNS) of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the near-wall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number Re_τ can be as low as 1000. The properties of the inner and outer peaks in the spanwise spectra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.

Application of a Bonner sphere spectrometer for determination of the energy spectra of neutrons generated by ≈1 MJ plasma focus

Czech Academy of Sciences Publication Activity Database

Králík, M.; Krása, Josef; Velyhan, Andriy; Scholz, M.; Ivanova-Stanik, I.M.; Bienkowska, B.; Miklaszewski, R.; Schmidt, H.; Řezáč, K.; Klír, D.; Kravárik, J.; Kubeš, P.

2010-01-01

Roč. 81, č. 11 (2010), 113503/1-113503/5 ISSN 0034-6748 R&D Projects: GA MŠk LA08024 Grant - others:FP-6 EU(XE) RITA-CT2006-26095 Institutional research plan: CEZ:AV0Z10100523 Keywords : plasma focus * fusion DD neutrons * Bonner sphere spectrometer * energy spectra of scattered neutrons * unfolded and calculated spectra Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.598, year: 2010

Tests of the GIC and Measurements of Angular Distributions and Energy Spectra for 58Ni（n,p）58Co Reaction at 4.1 MeV

Institute of Scientific and Technical Information of China (English)

Yu.M.Gledenov; M.Sedysheva; G.Khuukhenkhuu

1997-01-01

<正>On the basis of measurements of double differential cross sections for （n,α） reactions in 5-7 MeV neutron energy region using gridded ionization chamber （GIC）, we constructed a new GIC which, compared with the old ones, can bear higher pressure and makes it possible to measure （n,p） reactions up to 6 MeV and （n,xα） reactions up to 20 MeV. To test the new chamber, the saturation property for argon and krypton mixed with a few percent CO2 was studied using 241Am and compound Pu α source and tritium from 6Li(nth,t)4He, and the two dimensional spectra for 241Am and Pu α source, 6Li(nth,t)4He and H（n,p） reactions were measured. The measured energy spectra and angular distributions for α and tritium are reasonable, and the derived data for α, proton and tritium in argon and krypton from the measured spectra data were compared with the calculated ones. They are in good agreement. The angular distributions and energy spectra for 58Ni（n,p）58Co reaction at 4.1 MeV neutron energy were m

Measurement of energy spectra of charged particles emitted after the absorption of stopped negative pions in carbon

International Nuclear Information System (INIS)

Mechtersheimer, G.

1978-06-01

The energy spectra of charged particles (p,d,t, 3 He, 4 He and Li-nuclei) emitted after the absorption of stopped negative pions in carbon targets of different thickness (1.227, 0.307, 0.0202 g/cm 2 ) have been measured from the experimental threshold energy of about 0.5 MeV up to the kinematical limit of about 100 MeV. The experiments have been carried out at the biomedical pion channel πE3 of the Swiss Institute of Nuclear Research (SIN). (orig.) [de

Photoelectron spectra and electronic structure of some spiroborate complexes

Energy Technology Data Exchange (ETDEWEB)

Vovna, V.I.; Tikhonov, S.A.; Lvov, I.B., E-mail: lvov.ib@dvfu.ru; Osmushko, I.S.; Svistunova, I.V.; Shcheka, O.L.

2014-12-15

Highlights: • The electronic structure of three spiroborate complexes—boron 1,2-dioxyphenylene β-diketonates has been investigated. • UV and X-ray photoelectron spectra have been interpreted. • DFT calculations have been used for interpretation of spectral bands. • The binding energy of nonequivalent carbon and oxygen atoms were measured. • The structure of X-ray photoelectron spectra of the valence electrons is in good agreement with the energies and composition of Kohn–Sham orbitals. - Abstract: The electronic structure of the valence and core levels of three spiroborate complexes – boron 1,2-dioxyphenylene β-diketonates – has been investigated by methods of UV and X-ray photoelectron spectroscopy and quantum chemical density functional theory. The ionization energy of π- and n-orbitals of the dioxyphenylene fragment and β-diketonate ligand were measured from UV photoelectron spectra. This made it possible to determine the effect of substitution of one or two methyl groups by the phenyl in diketone on the electronic structure of complexes. The binding energy of nonequivalent carbon and oxygen atoms were measured from X-ray photoelectron spectra. The results of calculations of the energy of the valence orbitals of complexes allowed us to refer bands observed in the spectra of the valence electrons to the 2s-type levels of carbon and oxygen.

Inclusive sum rules and spectra of neutrons at the ISR

International Nuclear Information System (INIS)

Grigoryan, A.A.

1975-01-01

Neutron spectra in pp collisions at ISR energies are studied in the framework of sum rules for inclusive processes. The contributions of protons, π- and E- mesons to the energy sum rule are calculated at √5 = 53 GeV. It is shown by means of this sum rule that the spectra of neutrons at the ISR are in contradiction with the spectra of other particles also measured at the ISR

Probing dark energy with cluster counts and cosmic shear power spectra: including the full covariance

International Nuclear Information System (INIS)

Takada, Masahiro; Bridle, Sarah

2007-01-01

Several dark energy experiments are available from a single large-area imaging survey and may be combined to improve cosmological parameter constraints and/or test inherent systematics. Two promising experiments are cosmic shear power spectra and counts of galaxy clusters. However, the two experiments probe the same cosmic mass density field in large-scale structure, therefore the combination may be less powerful than first thought. We investigate the cross-covariance between the cosmic shear power spectra and the cluster counts based on the halo model approach, where the cross-covariance arises from the three-point correlations of the underlying mass density field. Fully taking into account the cross-covariance, as well as non-Gaussian errors on the lensing power spectrum covariance, we find a significant cross-correlation between the lensing power spectrum signals at multipoles l∼10 3 and the cluster counts containing halos with masses M∼>10 14 M o-dot . Including the cross-covariance for the combined measurement degrades and in some cases improves the total signal-to-noise (S/N) ratios up to ∼±20% relative to when the two are independent. For cosmological parameter determination, the cross-covariance has a smaller effect as a result of working in a multi-dimensional parameter space, implying that the two observables can be considered independent to a good approximation. We also discuss the fact that cluster count experiments using lensing-selected mass peaks could be more complementary to cosmic shear tomography than mass-selected cluster counts of the corresponding mass threshold. Using lensing selected clusters with a realistic usable detection threshold ((S/N) cluster ∼6 for a ground-based survey), the uncertainty on each dark energy parameter may be roughly halved by the combined experiments, relative to using the power spectra alone

IMP-8 observations of the spectra, composition, and variability of solar heavy ions at high energies relevant to manned space missions

International Nuclear Information System (INIS)

Tylka, Allan J.; Dietrich, William F.

1999-01-01

In more than 25 years of almost continuous observations, the University of Chicago's Cosmic Ray Telescope (CRT) on IMP-8 has amassed a unique database on high-energy solar heavy ions of potential relevance to manned spaceflight. In the very largest particle events, IMP-8/CRT has even observed solar Fe ions above the Galactic cosmic ray background up to ∼800 MeV/nucleon, an energy sufficiently high to penetrate nearly 25 g/cm 2 of shielding. IMP-8/CRT observations show that high-energy heavy-ion spectra are often surprisingly hard power laws, without the exponential roll-offs suggested by stochastic acceleration fits to lower energy measurements alone. Also, in many solar particle events the Fe/O ratio grows with increasing energy, contrary to the notion that ions with higher mass-to-charge ratios should be less abundant at higher energies. Previous studies of radiation hazards for manned spaceflight have often assumed heavy-ion composition and steeply-falling energy spectra inconsistent with these observations. Conclusions based on such studies should therefore be re-assessed. The significant event-to-event variability observed in the high-energy solar heavy ions also has important implications for strategies in building probabilistic models of solar particle radiation hazards

Multifractal spectra in shear flows

Science.gov (United States)

Keefe, L. R.; Deane, Anil E.

1989-01-01

Numerical simulations of three-dimensional homogeneous shear flow and fully developed channel flow, are used to calculate the associated multifractal spectra of the energy dissipation field. Only weak parameterization of the results with the nondimensional shear is found, and this only if the flow has reached its asymptotic development state. Multifractal spectra of these flows coincide with those from experiments only at the range alpha less than 1.

Calculation of Self-consistent Radial Electric Field in Presence of Convective Electron Transport in a Stellarator

International Nuclear Information System (INIS)

Kernbichler, W.; Heyn, M.F.; Kasilov, S.V.

2003-01-01

Convective transport of supra-thermal electrons can play a significant role in the energy balance of stellarators in case of high power electron cyclotron heating. Here, together with neoclassical thermal particle fluxes also the supra-thermal electron flux should be taken into account in the flux ambipolarity condition, which defines the self-consistent radial electric field. Since neoclassical particle fluxes are non-linear functions of the radial electric field, one needs an iterative procedure to solve the ambipolarity condition, where the supra-thermal electron flux has to be calculated for each iteration. A conventional Monte-Carlo method used earlier for evaluation of supra-thermal electron fluxes is rather slow for performing the iterations in reasonable computer time. In the present report, the Stochastic Mapping Technique (SMT), which is more effective than the conventional Monte Carlo method, is used instead. Here, the problem with a local monoenergetic supra-thermal particle source is considered and the effect of supra-thermal electron fluxes on both, the self-consistent radial electric field and the formation of different roots of the ambipolarity condition are studied

Use of orthonormal polynomial expansion method to the description of the energy spectra of biological liquids

International Nuclear Information System (INIS)

Bogdanova, N.B.; Todorov, S.T.; Ososkov, G.A.

2015-01-01

Orthonormal polynomial expansion method (OPEM) is applied to the data obtained by the method of energy spectra to the liquid of the biomass of wheat in the case when herbicides are used. Since the biomass of a biological object contains liquid composed mainly of water, the method of water spectra is applicable to this case as well. For comparison, the similar data obtained from control sample consisting of wheat liquid without the application of herbicides are shown. The total variance OPEM is involved including errors in both dependent and independent variables. Special criteria are used for evaluating the optimal polynomial degree and the number of iterations. The presented numerical results show good agreement with the experimental data. The developed analysis frame is of interest for future analysis in theoretical ecology.

Re-hardening of hadron transverse mass spectra in relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Ohnishi, A.; Otuka, N.; Sahu, P.K.; Isse, M.; Nara, Y.

2001-01-01

We analyze the spectra of pions and protons in heavy-ion collisions at relativistic energies from 2 A GeV to 65 + 65 A GeV by using a jet-implemented hadron-string cascade model. In this energy region, hadron transverse mass spectra first show softening until SPS energies, and re-hardening may emerge at RHIC energies. Since hadronic matter is expected to show only softening at higher energy densities, this re-hardening of spectra can be interpreted as a good signature of the quark-gluon plasma formation. (author)

FT-Raman, FT-IR spectra and total energy distribution of 3-pentyl-2,6-diphenylpiperidin-4-one: DFT method.

Science.gov (United States)

Subashchandrabose, S; Saleem, H; Erdogdu, Y; Rajarajan, G; Thanikachalam, V

2011-11-01

FT-Raman and FT-IR spectra were recorded for 3-pentyl-2,6-diphenylpiperidin-4-one (PDPO) sample in solid state. The equilibrium geometries, harmonic vibrational frequencies, infrared and the Raman scattering intensities were computed using DFT/6-31G(d,p) level. Results obtained at this level of theory were used for a detailed interpretation of the infrared and Raman spectra, based on the total energy distribution (TED) of the normal modes. Molecular parameters such as bond lengths, bond angles and dihedral angles were calculated and compared with X-ray diffraction data. This comparison was good agreement. The intra-molecular charge transfer was calculated by means of natural bond orbital analysis (NBO). Hyperconjugative interaction energy was more during the π-π* transition. Energy gap of the molecule was found using HOMO and LUMO calculation, hence the less band gap, which seems to be more stable. Atomic charges of the carbon, nitrogen and oxygen were calculated using same level of calculation. Copyright © 2011 Elsevier B.V. All rights reserved.

Dante-unfolding code for energy spectra evaluation

International Nuclear Information System (INIS)

Petilli, M.

1979-01-01

The code DANTE, using the last square method in unfolding for dosimetry purpose, solves the neutron spectra evaluation problem starting by activity measurements. The code DANTE introduced for the first time the correlation between available data by mean of flux and activity variance-covariance matrices and the error propagation. In the present report the solution method is detailed described

Neutron and photon spectra in LINACs

International Nuclear Information System (INIS)

Vega-Carrillo, H.R.; Martínez-Ovalle, S.A.; Lallena, A.M.; Mercado, G.A.; Benites-Rengifo, J.L.

2012-01-01

A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10 –6 and 1 MeV. Neutron and the Bremsstrahlung spectra show the same features regardless of the linac voltage. - Highlights: ► With MCNPX code realistic models of two LINACs were built. ► Photon and neutron spectra below the flattening filter and at the isocenter were calculated. ► Neutron spectrum at the flattening filter was compared against the Tosi et al. source-term model. ► Tosi et al. model underestimates the neutron contribution below 1 MeV. ► Photon spectra look alike to those published in literature.

Model-independent evaluation of recoils channeling impact on visible energy spectra in dark matter particles crystalline detectors

International Nuclear Information System (INIS)

Dyuldya, S.V.; Bratchenko, M.I.

2012-01-01

Proposed is a direct method of Dark Matter crystalline scintillation detectors calibration by means of an atomistic molecular dynamics modeling of their responses to ∼10 keV recoil atoms. Simulations show that the recoils channeling exists in NaI lattice with probabilities of ∼5 - 15 %. It does not affect the mean values of quenching factors but gives rise to high visible energy spectral tails absent in disordered detectors. As a result, the lattice ordering manifests the ∼100 % effect on NaI(Tl) visible energy spectra at 2-6 keV window

Attached flow structure and streamwise energy spectra in a turbulent boundary layer

Science.gov (United States)

Srinath, S.; Vassilicos, J. C.; Cuvier, C.; Laval, J.-P.; Stanislas, M.; Foucaut, J.-M.

2018-05-01

On the basis of (i) particle image velocimetry data of a turbulent boundary layer with large field of view and good spatial resolution and (ii) a mathematical relation between the energy spectrum and specifically modeled flow structures, we show that the scalings of the streamwise energy spectrum E11(kx) in a wave-number range directly affected by the wall are determined by wall-attached eddies but are not given by the Townsend-Perry attached eddy model's prediction of these spectra, at least at the Reynolds numbers Reτ considered here which are between 103 and 104. Instead, we find E11(kx) ˜kx-1 -p where p varies smoothly with distance to the wall from negative values in the buffer layer to positive values in the inertial layer. The exponent p characterizes the turbulence levels inside wall-attached streaky structures conditional on the length of these structures. A particular consequence is that the skin friction velocity is not sufficient to scale E11(kx) for wave numbers directly affected by the wall.

Density functional theory calculations of energy-loss carbon near-edge spectra of small diameter armchair and zigzag nanotubes: Core-hole, curvature, and momentum-transfer orientation effects

International Nuclear Information System (INIS)

Titantah, J.T.; Lamoen, D.; Jorissen, K.

2004-01-01

We perform density functional theory calculations on a series of armchair and zigzag nanotubes of diameters less than 1 nm using the all-electron full-potential(-linearized)-augmented-plane-wave method. Emphasis is laid on the effects of curvature, the electron-beam orientation, and the inclusion of the core hole on the carbon electron-energy-loss K edge. The electron-energy-loss near-edge spectra of all the studied tubes show strong curvature effects compared to that of flat graphene. The curvature-induced π-σ hybridization is shown to have a more drastic effect on the electronic properties of zigzag tubes than on those of armchair tubes. We show that the core-hole effect must be accounted for in order to correctly reproduce electron-energy-loss measurements. We also find that the energy-loss near-edge spectra of these carbon systems are dominantly dipole selected and that they can be expressed simply as a proportionality with the local momentum projected density of states, thus portraying the weak energy dependence of the transition matrix elements. Compared to graphite, we report a reduction in the anisotropy as seen on the energy-loss near-edge spectra of carbon nanotubes

Computed secondary-particle energy spectra following nonelastic neutron interactions with 12C for En between 15 and 60 MeV: Comparisons of results from two calculational methods

International Nuclear Information System (INIS)

Dickens, J.K.

1991-04-01

The organic scintillation detector response code SCINFUL has been used to compute secondary-particle energy spectra, dσ/dE, following nonelastic neutron interactions with 12 C for incident neutron energies between 15 and 60 MeV. The resulting spectra are compared with published similar spectra computed by Brenner and Prael who used an intranuclear cascade code, including alpha clustering, a particle pickup mechanism, and a theoretical approach to sequential decay via intermediate particle-unstable states. The similarities of and the differences between the results of the two approaches are discussed. 16 refs., 44 figs., 2 tabs

Hadronic energy spectra from nuclear collisions: Effects from collective transverse flow and the phase transition to quark matter

International Nuclear Information System (INIS)

Heinz, U.

1988-11-01

I give an overview of the processes determining the shape of energy spectra of hadrons emitted in relativistic nuclear collisions, and discuss how one can extract from them information on the presence of collective transverse flow and on the transition to quark-gluon matter in such collisions. 6 refs., 3 figs

Planck early results. XV. Spectral energy distributions and radio continuum spectra of northern extragalactic radio sources

DEFF Research Database (Denmark)

Aatrokoski, J.; Lähteenmäki, A.; Lavonen, N.

2011-01-01

Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multifrequency data. The nine Planck frequencies, from 30 to 857 GHz......, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase...... of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data...

Study of soft X-ray energy spectra from gas-puff Z-pinch plasma

International Nuclear Information System (INIS)

Zou Xiaobing; Wang Xinxin; Zhang Guixin; Han Min; Luo Chengmu

2006-01-01

A ROSS-FILTER-PIN spectrometer in the spectral range of 0.28 keV-1.56 keV was developed to study the soft X-ray radiation emitted from gas-puff Z-pinch plasma. It is composed of five channels covering the energy interval of interest without gaps. Soft X-ray spectral energy cuts were determined by the L absorption edges of selected filter elements (K absorption edges being used for light filter elements), and the optimum thickness of filter material was designed using computer code. To minimize the residual sensitivity outside the sensitivity range of each channel, element of the first filter was added into the second filter of all the Ross pair. To diminish the area of each filter, PIN detector with small sensitive area of 1 mm 2 was adopted for the spectrometer. A filter with small area is easy to fabricate and would be helpful to withstand the Z-pinch discharge shock wave. With this ROSS-FILTER-PIN spectrometer, the energy spectra of soft X-ray from a small gas-puff Z-pinch were investigated, and the correlation between the soft X-ray yield and the plasma implosion state was also studied. (authors)

Experiments on studying solar cosmic radiation nuclear composition and energy spectra on the Prognoz-9 sattelite

International Nuclear Information System (INIS)

Belyakov, S.A.; Gordeev, Yu.P.; Denisov, Yu.I.; Kolesov, G.Ya; Podorol'skij, A.N.; Nikitin, B.A.

1986-01-01

Performances of the SKI-1 device installed on board the artificial satellite of the Earth ''Prognoz-9'' and intended for measurements of a nuclear component of solar cosmic radiation are considered. The device permits to determine intensites of proton fluxes in the 10-30, 30-60, 60-90 and 90-120 MeV energy ranges and nuclei with charges z=1-30 and the following energies: 5-20 MeV for 1 H and 4 He nuclei, 10-26 MeV for C nuclei, 12-42 MeV for O nuclei, 23-80 MeV for Fe nuclei. The SKI-1 comprises two similar telescopes. The telescope includes 4 silicon semiconducting detectors. Energy spectra of solar cosmic radiation and data characterizing time dependence of their intensity are given

Eigenvalue-dependent neutron energy spectra: Definitions, analyses, and applications

International Nuclear Information System (INIS)

Cacuci, D.G.; Ronen, Y.; Shayer, Z.; Wagschal, J.J.; Yeivin, Y.

1982-01-01

A general qualitative analysis of spectral effects that arise from solving the kappa-, α-, γ-, and sigma-eigenvalue formulations of the neutron transport equation for nuclear systems that deviate (to first order) from criticality is presented. Hierarchies of neutron spectra softness are established and expressed concisely in terms of the newly introduced spatialdependent local spectral indices for the core and for the reflector. It is shown that each hierarchy is preserved, regardless of the nature of the specific physical mechanism that cause the system to deviate from criticality. Qualitative conclusions regarding the general behavior of the spectrum-dependent integral spectral indices and ICRs corresponding to the kappa-, α-, γ-, and sigma-eigenvalue formalisms are also presented. By defining spectral indices separately for the core and for the reflector, it is possible to account for the characteristics of neutron spectra in both the core and the reflector. The distinctions between the spectra in the core and in the reflector could not have been accounted for by using a single type of spectral index (e.g., a spectral index for the entire system or a spectral index solely for the core)

A method for unfolding high-energy scintillation gamma-ray spectra up to 8 MeV

International Nuclear Information System (INIS)

Dymke, N.; Hofmann, B.

1982-01-01

In unfolding a high-energy scintillation gamma-ray spectrum up to 8 MeV with the help of a response matrix, the means of linear algebra fail if the matrix is ill conditioned. In such cases, unfolding could be accomplished by means of a mathematical method based on a priori knowledge of the photon spectrum to be expected. The method which belongs to the class of regularization techniques was tested on in-situ gamma-ray spectra of 16 N recorded in a nuclear power plant near the primary circuit, using an 1.5 x 1.5 in. NaI(Tl) scintillation detector. For one regularized unfolding the results were presented in the form of an energy and a dose-rate spectrum. (author)

Precise Wavelengths and Energy Levels for the Spectra of Cr I, Mn I, and Mn III, and Branching Fractions for the Spectra of Fe II and Cr II

Science.gov (United States)

Nave, Gillian

I propose to measure wavelengths and energy levels for the spectra of Cr I, Mn I, and Mn III covering the wavelength range 80 nm to 5500 nm, and oscillator strengths for Fe II and Cr II in the region 120 nm to 2500 nm. I shall also produce intensity calibrated atlases and linelists of the iron-neon and chromium-neon hollow cathode lamps that can be compared with astrophysical spectra. The spectra will be obtained from archival data from spectrometers at NIST and Kitt Peak National Observatory and additional experimental observations as necessary from Fourier transform (FT) and grating spectrometers at NIST. The wavelength uncertainty of the strong lines will be better than 1 part in 10^7. The radiometric calibration of the spectra will be improved in order to reduce the uncertainty of measured oscillator strengths in the near UV region and extend the wavelength range of these measurements down to 120 nm. These will complement and support the measurements of lifetimes and branching fractions by J. E. Lawler in the near UV region. An intensive effort by NIST and Imperial College London that was partly funded by previous NASA awards has resulted in comprehensive analyses of the spectra of Fe II, Cr II and Cu II, with similar analyses of Mn II, Ni II, and Sc II underway. The species included in this proposal will complete the analysis of the first two ionization stages of the elements titanium through nickel using the same techniques, and add the spectrum of Mn III - one of the most important doubly-ionized elements. The elements Cr I and Mn I give large numbers of spectral lines in spectra of cool stars and important absorption lines in the interstellar medium. The spectrum of Mn III is important in chemically peculiar stars and can often only be studied in the UV region. Analyses of many stellar spectra depend on comprehensive analyses of iron-group elements and are hampered by incomplete spectroscopic data. As a result of many decades of work by the group at the

ION INJECTION AT QUASI-PARALLEL SHOCKS SEEN BY THE CLUSTER SPACECRAFT

International Nuclear Information System (INIS)

Johlander, A.; Vaivads, A.; Khotyaintsev, Yu. V.; Retinò, A.; Dandouras, I.

2016-01-01

Collisionless shocks in space plasma are known to be capable of accelerating ions to very high energies through diffusive shock acceleration (DSA). This process requires an injection of suprathermal ions, but the mechanisms producing such a suprathermal ion seed population are still not fully understood. We study acceleration of solar wind ions resulting from reflection off short large-amplitude magnetic structures (SLAMSs) in the quasi-parallel bow shock of Earth using in situ data from the four Cluster spacecraft. Nearly specularly reflected solar wind ions are observed just upstream of a SLAMS. The reflected ions are undergoing shock drift acceleration (SDA) and obtain energies higher than the solar wind energy upstream of the SLAMS. Our test particle simulations show that solar wind ions with lower energy are more likely to be reflected off the SLAMS, while high-energy ions pass through the SLAMS, which is consistent with the observations. The process of SDA at SLAMSs can provide an effective way of accelerating solar wind ions to suprathermal energies. Therefore, this could be a mechanism of ion injection into DSA in astrophysical plasmas

Energy spectra of protons emitted in the p+Xe→p+... interactions at 2.34 GeV/c and π-+Xe→p+... at 9 GeV/c

International Nuclear Information System (INIS)

Slovinskij, B.; Mulas, Eh.

1981-01-01

The energy spectra of protons (ESP) emitted in reactions p+Xe→kp+... at 2.34 GeV/c (k=1-9) and π - +Xe→kp+... at 9 GeV/c (k=1-17) have been studied. An evidence has been obtained for a unified description of those spectra by an exponential dependence of the invariant cross sections upon the kinetic energy independently of the proton emission angle. It is found that the ESP temperature becomes independent of the proton emission frequency when the energy of the interaction induced hadron is greater than approximately 3 GeV [ru

IDEN2-A program for visual identification of spectral lines and energy levels in optical spectra of atoms and simple molecules

Science.gov (United States)

Azarov, V. I.; Kramida, A.; Vokhmentsev, M. Ya.

2018-04-01

The article describes a Java program that can be used in a user-friendly way to visually identify spectral lines observed in complex spectra with theoretically predicted transitions between atomic or molecular energy levels. The program arranges various information about spectral lines and energy levels in such a way that line identification and determination of positions of experimentally observed energy levels become much easier tasks that can be solved fast and efficiently.

Elemental Spectra from the CREAM-I Flight

CERN Document Server

Ahn, Hoseok; Bagliesi, M G; Beatty, J J; Bigongiari, G; Boyle, P J; Childers, J T; Conklin, N B; Coutu, S; Duvernois, M A; Ganel, O; Han, J H; Jeon, J A; Kim, K C; Lee, J K; Lee, M H; Lutz, L; Maestro, P; Malinine, A; Marrocchesi, P S; Minnick, S; Mognet, S I; Nam, S; Nutter, S; Park, I H; Park, N H; Seo, E S; Sina, R; Swordy, S; Wakely, S P; Wu, J; Yang, J; Yoon, Y S; Zei, R; Zinn, S Y

2007-01-01

The Cosmic Ray Energetics And Mass (CREAM) instrument is a balloon-borne experiment designed to measure the composition and energy spectra of cosmic rays of charge Z = 1 to 26 up to an energy of ∼1015 eV. CREAM had two successful flights on long-duration balloons (LDB) launched from McMurdo Station, Antarctica, in December 2004 and December 2005. CREAM achieves a substantial measurement redundancy by employing multiple detector systems, namely a Timing Charge Detector (TCD), a Silicon Charge Detector (SCD), and a Cherenkov Detector (CD) for particle identification, and a Transition Radiation Detector (TRD) and a sampling tungsten/scintillating-fiber ionization calorimeter (CAL) for energy measurement. In this paper, preliminary energy spectra of various elements measured with CAL/SCD during the first 42-day flight are presented.

Catalogue of neutron spectra

International Nuclear Information System (INIS)

Buxerolle, M.; Massoutie, M.; Kurdjian, J.

1987-09-01

Neutron dosimetry problems have arisen as a result of developments in the applications of nuclear energy. The largest number of possible irradiation situations has been collected: they are presented in the form of a compilation of 44 neutron spectra. Diagrams show the variations of energy fluence and energy fluence weighted by the dose equivalent/fluence conversion factor, with the logarithm of the corresponding energy. The equivalent dose distributions are presented as percentages for the following energy bins: 0.01 eV/0.5 eV/50 keV/1 MeV/5 MeV/15 MeV. The dose equivalent, the mean energy and the effective energy for the dose equivalent for 1 neutron cm -2 are also given [fr

Rich magneto-absorption spectra of AAB-stacked trilayer graphene.

Science.gov (United States)

Do, Thi-Nga; Shih, Po-Hsin; Chang, Cheng-Peng; Lin, Chiun-Yan; Lin, Ming-Fa

2016-06-29

A generalized tight-binding model is developed to investigate the feature-rich magneto-optical properties of AAB-stacked trilayer graphene. Three intragroup and six intergroup inter-Landau-level (inter-LL) optical excitations largely enrich magneto-absorption peaks. In general, the former are much higher than the latter, depending on the phases and amplitudes of LL wavefunctions. The absorption spectra exhibit single- or twin-peak structures which are determined by quantum modes, LL energy spectra and Fermion distribution. The splitting LLs, with different localization centers (2/6 and 4/6 positions in a unit cell), can generate very distinct absorption spectra. There exist extra single peaks because of LL anti-crossings. AAB, AAA, ABA, and ABC stackings considerably differ from one another in terms of the inter-LL category, frequency, intensity, and structure of absorption peaks. The main characteristics of LL wavefunctions and energy spectra and the Fermi-Dirac function are responsible for the configuration-enriched magneto-optical spectra.

Tensor decompositions for the analysis of atomic resolution electron energy loss spectra

Energy Technology Data Exchange (ETDEWEB)

Spiegelberg, Jakob; Rusz, Ján [Department of Physics and Astronomy, Uppsala University, Box 516, S-751 20 Uppsala (Sweden); Pelckmans, Kristiaan [Department of Information Technology, Uppsala University, Box 337, S-751 05 Uppsala (Sweden)

2017-04-15

A selection of tensor decomposition techniques is presented for the detection of weak signals in electron energy loss spectroscopy (EELS) data. The focus of the analysis lies on the correct representation of the simulated spatial structure. An analysis scheme for EEL spectra combining two-dimensional and n-way decomposition methods is proposed. In particular, the performance of robust principal component analysis (ROBPCA), Tucker Decompositions using orthogonality constraints (Multilinear Singular Value Decomposition (MLSVD)) and Tucker decomposition without imposed constraints, canonical polyadic decomposition (CPD) and block term decompositions (BTD) on synthetic as well as experimental data is examined. - Highlights: • A scheme for compression and analysis of EELS or EDX data is proposed. • Several tensor decomposition techniques are presented for BSS on hyperspectral data. • Robust PCA and MLSVD are discussed for denoising of raw data.

A supra-thermal energetic particle detector /STEP/ for composition measurements in the range of about 20 keV/nucleon to 1 MeV/nucleon

Science.gov (United States)

Mason, G. M.; Gloeckler, G.

1981-01-01

A novel detector system is described, employing a time-of-flight versus residual energy technique which allows measurement of particle composition (H-Fe), energy spectra and anisotropies in an energy range unaccessible with previously flown sensors. Applications of this method to measurements of the solar wind ion composition are also discussed.

Gamma-ray emission spectra from spheres with 14 MeV neutron source

International Nuclear Information System (INIS)

Yamamoto, Junji; Kanaoka, Takeshi; Murata, Isao; Takahashi, Akito; Sumita, Kenji

1989-01-01

Energy spectra of neutron-induced gamma-rays emitted from spherical samples were measured using a 14 MeV neutron source. The samples in use were LiF, Teflon:(CF 2 ) n , Si, Cr, Mn, Co, Cu, Nb, Mo, W and Pb. A diameter of the sphere was either 40 or 60 cm. The gamma-ray energy in the emission spectra covered the range from 500 keV to 10 MeV. Measured spectra were compared with transport calculations using the nuclear data files of JENDL-3T and ENDF/B-IV. The agreements between the measurements and the JENDL-3T calculations were good in the emission spectra for the low energy gamma-rays from inelastic scattering. (author)

DLTS spectra of silicon diodes with p+-n-junction irradiated with high energy krypton ions

Directory of Open Access Journals (Sweden)

Nikolai A. Poklonski

2016-06-01

Full Text Available p+-n-Diodes have been studied. The diodes were manufactured on wafers (thickness 460 μm, (111 plane of uniformly phosphorus doped float-zone-grown single-crystal silicon. The resistivity of silicon was 90 Ω cm and the phosphorus concentration was 5×1013 cm−3. The diodes were irradiated with 250 MeV krypton ions. The irradiation fluence was 108 cm−2. Deep-level transient spectroscopy (DLTS was used to examine the defects induced by high energy krypton ion implantation. The DLTS spectra were recorded at a frequency of 1 MHz in the 78–290 K temperature range. The capacity-voltage characteristics have been measured at a reverse bias voltage from 0 to −19 V at a frequency of 1 MHz. We show that the main irradiation-induced defects are A-centers and divacancies. The behavior of DLTS spectra in the 150–260 K temperature range depends essentially on the emission voltage Ue. The variation of Ue allows us to separate the contributions of different defects into the DLTS spectrum in the 150–260 K temperature range. We show that, in addition to A-centers and divacancies, irradiation produces multivacancy complexes with the energy level Et = Ec−(0.5±0.02 eV and an electron capture cross section of ~4×10–13 cm2.

Peak center and area estimation in gamma-ray energy spectra using a Mexican-hat wavelet

Energy Technology Data Exchange (ETDEWEB)

Qin, Zhang-jian; Chen, Chuan; Luo, Jun-song; Xie, Xing-hong; Ge, Liang-quan [School of Information Science & Technology, Chengdu University of Technology, Chengdu (China); Wu, Qi-fan [Department of Engineering Physics, Tsinghua University, Beijing (China)

2017-06-21

Wavelet analysis is commonly used to detect and localize peaks within a signal, such as in Gamma-ray energy spectra. This paper presents a peak area estimation method based on a new wavelet analysis. Another Mexican Hat Wavelet Signal (MHWS) named after the new MHWS is obtained with the convolution of a Gaussian signal and a MHWS. During the transform, the overlapping background on the Gaussian signal caused by Compton scattering can be subtracted because the impulse response function MHWS is a second-order smooth function, and the amplitude of the maximum within the new MHWS is the net height corresponding to the Gaussian signal height, which can be used to estimate the Gaussian peak area. Moreover, the zero-crossing points within the new MHWS contain the information of the Gaussian variance whose valve should be obtained when the Gaussian peak area is estimated. Further, the new MHWS center is also the Gaussian peak center. With that distinguishing feature, the channel address of a characteristic peak center can be accurately obtained which is very useful in the stabilization of airborne Gamma energy spectra. In particular, a method for determining the correction coefficient k is given, where the peak area is calculated inaccurately because the value of the scale factor in wavelet transform is too small. The simulation and practical applications show the feasibility of the proposed peak center and area estimation method.

The Effects of Interplanetary Transport in the Event-intergrated Solar Energetic Particle Spectra

Energy Technology Data Exchange (ETDEWEB)

Zhao, Lulu; Zhang, Ming; Rassoul, Hamid K., E-mail: lzhao@fit.edu [Physics and Space Sciences Department, Florida Institute of Technology, Melbourne, FL 32901 (United States)

2017-02-10

Previous investigations on the energy spectra of solar energetic particle (SEP) events revealed that the energy spectra observed at 1 au often show double power laws with break energies from one to tens of MeV/nuc. In order to determine whether the double power-law features result from the SEP source or the interplanetary transport process from the Sun to 1 au, we separately analyze the SEP spectra in the decay phase, during which the transport effect is minimum. In this paper, we reported three events observed by the Interplanetary Monitory Platform 8 spacecraft, which occurred on 1977 September 19, November 22, and 1979 March 1. For the first two events, the event-integrated spectra of protons possess double power-law profiles with break energies in a range of several MeV to tens of MeV, while the spectra integrated in the decay (reservoir) phase yield single power laws. Moreover, a general trend from a double power law at the rising phase to a single power law at the decay phase is observed. For the third event, both the event-integrated and the reservoir spectra show double power-law features. However, the difference between the low- and high-energy power-law indices is smaller for the reservoir spectrum than the event-integrated spectrum. These features were reproduced by solving the 1D diffusion equation analytically and we suggest that the transport process, especially the diffusion process, plays an important role in breaking the energy spectra.

He-like spectra from laboratory plasmas and solar flares

International Nuclear Information System (INIS)

Kato, Takako

1990-01-01

The X-ray spectra of He-like ions from tokamaks and solar flares have been measured. Several physical parameters of plasma can be derived from the X-ray spectra of He-like ions. The ion temperature can be derived from the doppler width of a resonance line. The electron temperature is obtained from the intensity ratio of dielectronic satellite lines to a resonance line. The energy level for the prominent lines is shown. The line q is produced mainly by the inner-shell excitation of Li-like ions, and line beta is produced by the inner-shell excitation of Be-like ions. The intensity ratios give the ion density ratios. The intensities of the intercombination and the forbidden lines are affected by the recombination from H-like ions. The synthetic spectra including excitation, ionization and recombination processes are fitted to the measurement. In this paper, the He-like X-ray spectra of the titanium ions from TFTR tokamak plasma and of the iron ions from solar flares are discussed, paying attention to the presence of high energy electrons which affect the spectra and ionization balance. Atomic data, the spectra from the TFTR tokamak, the spectra from solar flares and so on are described. (K.I.)

Neutron energy spectra of sup 2 sup 5 sup 2 Cf, Am-Be source and of the D(d,n) sup 3 He reaction

CERN Document Server

Sang Tae Park

2003-01-01

The neutron energy spectrum of the following sources were measured using a fast neutron spectrometer with the NE-213 liquid scintillator: sup 2 sup 5 sup 2 Cf, Am-Be and D(d,n) sup 3 He reaction from a 3 MeV Pelletron accelerator in Tokyo Institute of Technology. The measured proton recoil pulse height data of sup 2 sup 5 sup 2 Cf, Am-Be and D(d,n) sup 3 He were unfolded using the mathematical program to obtain the neutron energy spectrum. The sup 2 sup 5 sup 2 Cf and Am-Be neutron energy spectra were measured and the results obtained showed a good agreement with the spectra usually published in the literature. The neutron energy spectrum from D(d,n) sup 3 He was measured and the results obtained also showed a good agreement with the calculation by time of flight (TOF) methods. (author)

Photon and photoneutron spectra produced in radiotherapy Linacs

International Nuclear Information System (INIS)

Vega C, H. R.; Martinez O, S. A.; Benites R, J. L.; Lallena, A. M.

2011-10-01

A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10 -6 and 1 MeV. Neutron and Bremsstrahlung spectra show the same features regardless of the linac voltage. The amount of photons and neutrons produced by the 15 MV linac is smaller than that found for the 18 MV linac. As expected, Bremsstrahlung spectra ends according to the voltage used to accelerate the electrons. (Author)

Photon and photoneutron spectra produced in radiotherapy Linacs

Energy Technology Data Exchange (ETDEWEB)

Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Martinez O, S. A. [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Av. Central del Norte Km. 1, Via Paipa Tunja, Boyaca (Colombia); Benites R, J. L. [Universidad Autonoma de Nayarit, Postgrado CBAP, Carretera Tepic Compostela Km. 9, Xalisco, Nayarit (Mexico); Lallena, A. M., E-mail: fermineutron@yahoo.com [Universida de Granada, Departamento de Fisica Atomica, Molecular y Nuclear, E-18071 Granada (Spain)

2011-10-15

A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10{sup -6} and 1 MeV. Neutron and Bremsstrahlung spectra show the same features regardless of the linac voltage. The amount of photons and neutrons produced by the 15 MV linac is smaller than that found for the 18 MV linac. As expected, Bremsstrahlung spectra ends according to the voltage used to accelerate the electrons. (Author)

Nuclear composition and energy spectra in the 1969 April 12 solar-particle event.

Science.gov (United States)

Bertsch, D. L.; Fichtel, C. E.; Reames, D. V.

1972-01-01

Measurement of the charge composition for several of the multicharged nuclei and the energy spectra for hydrogen, helium, and medium (6 less than or equal to Z less than or equal to 9) nuclei in the Apr. 12, 1969, solar-particle event. The energy/nucleon spectral shape of the medium nuclei was again the same as that of the helium nuclei, and the ratio of these two species was consistent with the present best average of 58 plus or minus 5. By combining the results obtained here with previous work, improved estimates of the Ne/O and Mg/O values of 0.16 plus or minus 0.03 and 0.056 plus or minus 0.014, respectively, were obtained. Silicon and sulfur abundances relative to O were determined to be 0.208 plus or minus 0.008 plus or minus 0.006, respectively, and 85% confidence upper limits for Ar and Ca relative to O of 0.017 and 0.010 were obtained. Previously, these last four nuclei had only been listed as a group.

Program LEPS to addition of gamma spectra from germanium detectors

International Nuclear Information System (INIS)

Romero, L.

1986-01-01

The LEP program, written in FORTRAN IV, performs the addition of two spectra, collected with different detectors, from the same sample. This application, adds the two gamma spectra obtained from two opposite LEPS Germanium Detectors (Low Energy Photon Spectrometer), correcting the differences (channel/energy) between both two spectra, and fitting them before adding. The total-spectrum is recorded at the computer memory as a single spectrum. The necessary equipment, to run this program is: - Two opposite germanium detectors, with their associate electronics. - Multichannel analyzer (2048 memory channel minimum) - Computer on-line interfacing to multichannel analyzer. (Author) 4 refs

Atomic Spectra Database (ASD)

Science.gov (United States)

SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

Comparative study of Monte Carlo particle transport code PHITS and nuclear data processing code NJOY for PKA energy spectra and heating number under neutron irradiation

International Nuclear Information System (INIS)

Iwamoto, Y.; Ogawa, T.

2016-01-01

The modelling of the damage in materials irradiated by neutrons is needed for understanding the mechanism of radiation damage in fission and fusion reactor facilities. The molecular dynamics simulations of damage cascades with full atomic interactions require information about the energy distribution of the Primary Knock on Atoms (PKAs). The most common process to calculate PKA energy spectra under low-energy neutron irradiation is to use the nuclear data processing code NJOY2012. It calculates group-to-group recoil cross section matrices using nuclear data libraries in ENDF data format, which is energy and angular recoil distributions for many reactions. After the NJOY2012 process, SPKA6C is employed to produce PKA energy spectra combining recoil cross section matrices with an incident neutron energy spectrum. However, intercomparison with different processes and nuclear data libraries has not been studied yet. Especially, the higher energy (~5 MeV) of the incident neutrons, compared to fission, leads to many reaction channels, which produces a complex distribution of PKAs in energy and type. Recently, we have developed the event generator mode (EGM) in the Particle and Heavy Ion Transport code System PHITS for neutron incident reactions in the energy region below 20 MeV. The main feature of EGM is to produce PKA with keeping energy and momentum conservation in a reaction. It is used for event-by-event analysis in application fields such as soft error analysis in semiconductors, micro dosimetry in human body, and estimation of Displacement per Atoms (DPA) value in metals and so on. The purpose of this work is to specify differences of PKA spectra and heating number related with kerma between different calculation method using PHITS-EGM and NJOY2012+SPKA6C with different libraries TENDL-2015, ENDF/B-VII.1 and JENDL-4.0 for fusion relevant materials

Neutron spectra unfolding in Bonner spheres spectrometry using neural networks

International Nuclear Information System (INIS)

Kardan, M.R.; Setayeshi, S.; Koohi-Fayegh, R.; Ghiassi-Nejad, M.

2003-01-01

The neural network method has been used for the unfolding of neutron spectra in neutron spectrometry by Bonner spheres. A back propagation algorithm was used for training of neural networks 4mm x 4 mm bare LiI(Eu) and in a polyethylene sphere set: 2, 3, 4, 5, 6, 7, 8, 10, 12, 18 inch diameter have been used for unfolding of neutron spectra. Neural networks were trained by 199 sets of neutron spectra, which were subdivided into 6, 8, 10, 12, 15 and 20 energy bins and for each of them an appropriate neural network was designed and trained. The validation was performed by the 21 sets of neutron spectra. A neural network with 10 energy bins which had a mean value of error of 6% for dose equivalent estimation of spectra in the validation set showed the best results. The obtained results show that neural networks can be applied as an effective method for unfolding neutron spectra especially when the main target is neutron dosimetry. (author)

Fluctuations in transverse energy and multiplicity, energy densities, and neutral pion spectra in nucleus-nucleus collissions at 200 GeV/nucleon

International Nuclear Information System (INIS)

Plasil, F.; Albrecht, R.; Awes, T.C.

1989-01-01

The main goal of the CERN heavy-ion experiments is the search for an indication that the predicted state of deconfined quarks and gluons, the quark-gluon plasma (QGP), has been produced. The quantity most crucial to the probability of QGP formation is the thermalized energy density attained during the heavy-ion reaction. The amount of energy radiated transverse to the beam direction is the experimental quantity which is believed to be a measure of the amount of energy deposition in the reaction, and hence to reflect the energy density attained. In this presentation we consider the systematics of transverse energy production at CERN SPS energies, and we use the results to make estimates, under various assumptions, of attained energy densities. Measurements of direct photons and lepton pairs are considered to be among the most promising methods for studies of the QGP. In contrast to hadrons, direct photons are not expected to undergo any interactions after their creation. The WA80 collaboration has undertaken the measurement of direct photons, which is a difficult task due to the presence of a high background of photons from the decay of neutral pions. The π 0 spectra themselves, however, provide us with the opportunity to study the excited reaction zone during the hadronization phase. We present here measurements of neutral pions produced in 16 O + Au collisions at 200 GeV/nucleon. 22 refs., 11 figs

Measurement of prompt neutron spectra from the "2"3"9Pu(n, f ) fission reaction for incident neutron energies from 1 to 200 MeV

International Nuclear Information System (INIS)

Chatillon, A.; Belier, G.; Granier, T.; Laurent, B.; Morillon, B.; Taieb, J.; Haight, R.C.; Devlin, M.; Nelson, R.O.; Noda, R.S.; O'Donnell, J.M.

2014-01-01

Prompt fission neutron spectra in the neutron-induced fission of "2"3"9Pu have been measured for incident neutron energies from 1 to 200 MeV at the Los Alamos Neutron Science Center. Mean energies deduced from the prompt fission neutron spectra (PFNS) lead to the observation of the opening of the second chance fission at 7 MeV and to indications for the openings of fission channels of third and fourth chances. Moreover, the general trend of the measured PFNS is well reproduced by the different models. The comparison between data and models presents, however, two discrepancies. First, the prompt neutron mean energy seems constant for neutron energy, at least up to 7 MeV, whereas in the theoretical calculations it is continuously increasing. Second, data disagree with models on the shape of the high energy part of the PFNS, where our data suggest a softer spectrum than the predictions. (authors)

Hadronic spectra from collisions of heavy nuclei

International Nuclear Information System (INIS)

Jacobs, P.

1997-03-01

Hadronic spectra from collisions of heavy ions at ultrarelativistic energies are discussed, concentrating on recent measurements at the SPS of central Pb+Pb collisions at 158 GeV/nucleon, which are compared to collisions of lighter ions and at lower beam energies. Baryon stopping is seen to be larger for heavier systems and lower energies. Total yields of pions and kaons scale with the number of participants in central collisions at the SPS; in particular, the K/π ratio is constant between central S+S and Pb+Pb at the SPS. Transverse mass spectra indicate significantly larger radial flow for the heavier systems. At midrapidity, an enhancement of - >/ + > and - >/ + > at low P T are best explained by final state Coulomb interaction with the residual charge of the fireball

New Fe i Level Energies and Line Identifications from Stellar Spectra. II. Initial Results from New Ultraviolet Spectra of Metal-poor Stars

Energy Technology Data Exchange (ETDEWEB)

Peterson, Ruth C. [SETI Institute and Astrophysical Advances, 607 Marion Place, Palo Alto, CA 94301 (United States); Kurucz, Robert L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Ayres, Thomas R., E-mail: peterson@ucolick.org [Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309-0389 (United States)

2017-04-01

The Fe i spectrum is critical to many areas of astrophysics, yet many of the high-lying levels remain uncharacterized. To remedy this deficiency, Peterson and Kurucz identified Fe i lines in archival ultraviolet and optical spectra of metal-poor stars, whose warm temperatures favor moderate Fe i excitation. Sixty-five new levels were recovered, with 1500 detectable lines, including several bound levels in the ionization continuum of Fe i. Here, we extend the previous work by identifying 59 additional levels, with 1400 detectable lines, by incorporating new high-resolution UV spectra of warm metal-poor stars recently obtained by the Hubble Space Telescope Imaging Spectrograph. We provide gf values for these transitions, both computed as well as adjusted to fit the stellar spectra. We also expand our spectral calculations to the infrared, confirming three levels by matching high-quality spectra of the Sun and two cool stars in the H -band. The predicted gf values suggest that an additional 3700 Fe i lines should be detectable in existing solar infrared spectra. Extending the empirical line identification work to the infrared would help confirm additional Fe i levels, as would new high-resolution UV spectra of metal-poor turnoff stars below 1900 Å.

IUPAC critical evaluation of the rotational–vibrational spectra of water vapor, Part III: Energy levels and transition wavenumbers for H216O

International Nuclear Information System (INIS)

Tennyson, Jonathan; Bernath, Peter F.; Brown, Linda R.; Campargue, Alain; Császár, Attila G.; Daumont, Ludovic; Gamache, Robert R.; Hodges, Joseph T.; Naumenko, Olga V.; Polyansky, Oleg L.; Rothman, Laurence S.; Vandaele, Ann Carine; Zobov, Nikolai F.; Al Derzi, Afaf R.; Fábri, Csaba; Fazliev, Alexander Z.; Furtenbacher, Tibor

2013-01-01

This is the third of a series of articles reporting critically evaluated rotational–vibrational line positions, transition intensities, and energy levels, with associated critically reviewed labels and uncertainties, for all the main isotopologues of water. This paper presents experimental line positions, experimental-quality energy levels, and validated labels for rotational–vibrational transitions of the most abundant isotopologue of water, H 2 16 O. The latest version of the MARVEL (Measured Active Rotational–Vibrational Energy Levels) line-inversion procedure is used to determine the rovibrational energy levels of the electronic ground state of H 2 16 O from experimentally measured lines, together with their self-consistent uncertainties, for the spectral region up to the first dissociation limit. The spectroscopic network of H 2 16 O containstwo components, an ortho (o) and a para (p) one. For o-H 2 16 O and p-H 2 16 O, experimentally measured, assigned, and labeled transitions were analyzed from more than 100 sources. The measured lines come from one-photon spectra recorded at room temperature in absorption, from hot samples with temperatures up to 3000 K recorded in emission, and from multiresonance excitation spectra which sample levels up to dissociation. The total number of transitions considered is 184 667 of which 182 156 are validated: 68 027 between para states and 114 129 ortho ones. These transitions give rise to 18 486 validated energy levels, of which 10 446 and 8040 belong to o-H 2 16 O and p-H 2 16 O, respectively. The energy levels, including their labeling with approximate normal-mode and rigid-rotor quantum numbers, have been checked against ones determined from accurate variational nuclear motion computations employing exact kinetic energy operators as well as against previous compilations of energy levels. The extensive list of MARVEL lines and levels obtained are deposited in the supplementary data of this paper, as well as in a

Impact of environmentally induced fluctuations on quantum mechanically mixed electronic and vibrational pigment states in photosynthetic energy transfer and 2D electronic spectra

Energy Technology Data Exchange (ETDEWEB)

Fujihashi, Yuta; Ishizaki, Akihito, E-mail: ishizaki@ims.ac.jp [Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki 444-8585 (Japan); Fleming, Graham R. [Department of Chemistry, University of California, Berkeley and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2015-06-07

Recently, nuclear vibrational contribution signatures in two-dimensional (2D) electronic spectroscopy have attracted considerable interest, in particular as regards interpretation of the oscillatory transients observed in light-harvesting complexes. These transients have dephasing times that persist for much longer than theoretically predicted electronic coherence lifetime. As a plausible explanation for this long-lived spectral beating in 2D electronic spectra, quantum-mechanically mixed electronic and vibrational states (vibronic excitons) were proposed by Christensson et al. [J. Phys. Chem. B 116, 7449 (2012)] and have since been explored. In this work, we address a dimer which produces little beating of electronic origin in the absence of vibronic contributions, and examine the impact of protein-induced fluctuations upon electronic-vibrational quantum mixtures by calculating the electronic energy transfer dynamics and 2D electronic spectra in a numerically accurate manner. It is found that, at cryogenic temperatures, the electronic-vibrational quantum mixtures are rather robust, even under the influence of the fluctuations and despite the small Huang-Rhys factors of the Franck-Condon active vibrational modes. This results in long-lasting beating behavior of vibrational origin in the 2D electronic spectra. At physiological temperatures, however, the fluctuations eradicate the mixing, and hence, the beating in the 2D spectra disappears. Further, it is demonstrated that such electronic-vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics, despite contributing to the enhancement of long-lived quantum beating in 2D electronic spectra, contrary to speculations in recent publications.

Earthquake source scaling and self-similarity estimation from stacking P and S spectra

Science.gov (United States)

Prieto, GermáN. A.; Shearer, Peter M.; Vernon, Frank L.; Kilb, Debi

2004-08-01

We study the scaling relationships of source parameters and the self-similarity of earthquake spectra by analyzing a cluster of over 400 small earthquakes (ML = 0.5 to 3.4) recorded by the Anza seismic network in southern California. We compute P, S, and preevent noise spectra from each seismogram using a multitaper technique and approximate source and receiver terms by iteratively stacking the spectra. To estimate scaling relationships, we average the spectra in size bins based on their relative moment. We correct for attenuation by using the smallest moment bin as an empirical Green's function (EGF) for the stacked spectra in the larger moment bins. The shapes of the log spectra agree within their estimated uncertainties after shifting along the ω-3 line expected for self-similarity of the source spectra. We also estimate corner frequencies and radiated energy from the relative source spectra using a simple source model. The ratio between radiated seismic energy and seismic moment (proportional to apparent stress) is nearly constant with increasing moment over the magnitude range of our EGF-corrected data (ML = 1.8 to 3.4). Corner frequencies vary inversely as the cube root of moment, as expected from the observed self-similarity in the spectra. The ratio between P and S corner frequencies is observed to be 1.6 ± 0.2. We obtain values for absolute moment and energy by calibrating our results to local magnitudes for these earthquakes. This yields a S to P energy ratio of 9 ± 1.5 and a value of apparent stress of about 1 MPa.

Measurement of neutron energy spectra of PuO[sub 2]-UO[sub 2] mixed oxide fuel and penetrated through surrounding lead-acryl shield

Energy Technology Data Exchange (ETDEWEB)

Nakao, Noriaki; Tsujimura, Norio; Nakamura, Takashi (Tohoku Univ., Sendai (Japan). Cyclotron and Radioisotope Center); Momose, Takumaro; Ninomiya, Kazushige; Ishiguro; Hideharu

1993-12-01

The energy spectra of neutrons emitted from an aluminum can containing PuO[sub 2]-UO[sub 2] mixed oxide fuel and penetrated through a 35mm thick lead-acryl shield surrounding the can, were measured with the NE-213 organic liquid scintillator, the proton recoil proportional counter and the multi-moderator [sup 3]He spectrometer (Bonner Ball). The measured results were compared with the results calculated by the MORSE-CG Monte Carlo code on the basis of source neutron yields obtained by the ORIGEN-2 code and the source energy spectrum cited from the reference data. The agreement between these two was pretty good. The dose equivalents were then calculated from thus-obtained energy spectra and the flux-to-dose conversion factor and showed good agreement with the data measured with the neutron dose-equivalent counters (rem counters). Since the published data on energy spectrum of mixed oxide fuel are very scarce, these results can be useful as basic data for shielding design study and radiation control of nuclear fuel facilities. (author).

Evaluation of double differential yield as used for representation of neutron spectra

International Nuclear Information System (INIS)

Solieman, A.H.M.; Comsan, M.N.H.

2002-01-01

The neutron intensity for TOF spectra representation has, until now, only been expressed in terms of double differential yield; number of neutrons per unit charge per unit solid angle per unit neutron energy interval (i.e. neutron intensity at a given resolving power). For accelerator-based neutron sources, the double differential yield - in terms of neutron energy interval - is found to be affected by the kinematics of the neutron producing reaction, to produce intensity irrelevant spectra. The results affect not only the applications that depend on relative neutron intensities, but also the applications that depend on the neutron intensity-weighted integration of the neutron spectra (e.g. neutron average energy calculation, and dose calculation using kerma factors). Other definition of the double differential yield - in terms of projectile energy loss - is suggested to avoid the drawbacks of the old definition. The neutron spectra that are driven using the two definitions are discussed

Neutron spectra produced by moderating an isotopic neutron source

International Nuclear Information System (INIS)

Carrillo Nunnez, Aureliano; Vega Carrillo, Hector Rene

2001-01-01

A Monte Carlo study has been carried out to determine the neutron spectra produced by an isotopic neutron source inserted in moderating media. Most devices used for radiation protection have a response strongly dependent on neutron energy. ISO recommends several neutron sources and monoenergetic neutron radiations, but actual working situations have broad spectral neutron distributions extending from thermal to MeV energies, for instance, near nuclear power plants, medical applications accelerators and cosmic neutrons. To improve the evaluation of the dosimetric quantities, is recommended to calibrate the radiation protection devices in neutron spectra which are nearly like those met in practice. In order to complete the range of neutron calibrating sources, it seems useful to develop several wide spectral distributions representative of typical spectra down to thermal energies. The aim of this investigation was to use an isotopic neutron source in different moderating media to reproduce some of the neutron fields found in practice. MCNP code has been used during calculations, in these a 239PuBe neutron source was inserted in H2O, D2O and polyethylene moderators. Moderators were modeled as spheres and cylinders of different sizes. In the case of cylindrical geometry the anisotropy of resulting neutron spectra was calculated from 0 to 2 . From neutron spectra dosimetric features were calculated. MCNP calculations were validated by measuring the neutron spectra of a 239PuBe neutron source inserted in a H2O cylindrical moderator. The measurements were carried out with a multisphere neutron spectrometer with a 6LiI(Eu) scintillator. From the measurements the neutron spectrum was unfolded using the BUNKIUT code and the UTA4 response matrix. Some of the moderators with the source produce a neutron spectrum close to spectra found in actual applications, then can be used during the calibration of radiation protection devices

Electron impact spectra of some mono-olefinic hydrocarbonsa)

International Nuclear Information System (INIS)

Johnson, K.E.; Johnston, D.B.; Lipsky, S.

1979-01-01

Electron impact spectra of ethylene, propylene, isobutene, trans-butene, cis-butene, trimethylethylene, and tetramethylethylene have been obtained at scattering angles of 0 0 and 90 0 and at impact energies from approx. =20 to 150 eV. The spectra scan an energy-loss region from 2.5--15 eV. All of the observed Rydberg transitions of the methyl derivatives are correlated to corresponding Rydberg transitions of ethylene. The missing π→3p transitions of ethylene are tentatively located via this correlation. Evidence is also presented for assigning the N→3R' system of ethylene (at 8.26 eV) to a π→3p/sub x/ transition. Possible assignments of some broad continua above approx. =8--9eV as sigma→π* and sigma→sigma* transitions are considered. In agreement with other reported large-angle electron impact spectra, no evidence is obtained for transitions that could be assigned to triplet Rydberg states. However the π→π* triplet transitions are all clearly located with transition energies in good agreement with those obtained by a variety of other techniques

Fast neutron spectra determination by threshold activation detectors using neural networks

International Nuclear Information System (INIS)

Kardan, M.R.; Koohi-Fayegh, R.; Setayeshi, S.; Ghiassi-Nejad, M.

2004-01-01

Neural network method was used for fast neutron spectra unfolding in spectrometry by threshold activation detectors. The input layer of the neural networks consisted of 11 neurons for the specific activities of neutron-induced nuclear reaction products, while the output layers were fast neutron spectra which had been subdivided into 6, 8, 10, 12, 15 and 20 energy bins. Neural network training was performed by 437 fast neutron spectra and corresponding threshold activation detector readings. The trained neural network have been applied for unfolding 50 spectra, which were not in training sets and the results were compared with real spectra and unfolded spectra by SANDII. The best results belong to 10 energy bin spectra. The neural network was also trained by detector readings with 5% uncertainty and the response of the trained neural network to detector readings with 5%, 10%, 15%, 20%, 25% and 50% uncertainty was compared with real spectra. Neural network algorithm, in comparison with other unfolding methods, is very fast and needless to detector response matrix and any prior information about spectra and also the outputs have low sensitivity to uncertainty in the activity measurements. The results show that the neural network algorithm is useful when a fast response is required with reasonable accuracy

Extraction of level density and γ strength function from primary γ spectra

International Nuclear Information System (INIS)

Schiller, A.; Bergholt, L.; Guttormsen, M.; Melby, E.; Rekstad, J.; Siem, S.

2000-01-01

We present a new iterative procedure to extract the level density and the γ strength function from primary γ spectra for energies close up to the neutron binding energy. The procedure is tested on simulated spectra and on data from the 173 Yb( 3 He,α) 172 Yb reaction

Global characteristics of atomic spectra and their use for the analysis of spectra. IV. Configuration interaction effects

International Nuclear Information System (INIS)

Kucas, S.; Jonauskas, V.; Karazija, R.

1997-01-01

For pt.III see ibid., vol.52, p.639, 1995. Changes of the moments of atomic spectrum due to configuration interaction (CI), the CI strength, the average shift of the energy of a level due to its interaction with all levels of distant configuration and other global characteristics of CI effects in atoms are systematised and their expressions presented. The results of the calculation of those characteristics for the energy level spectra of the 3s3p 3 + 3s 2 3p3d configurations in Si isoelectronic series, 3p 5 3d N + 3p 6 3d N-2 4p + 3p 6 3d N-2 4f (N = 5, 6, 7, 8) in Cr, Mn, Fe and Co isoelectronic series, ns 2 np N + np N+2 at n = 2 - 5 and N = 2 - 4 in neutral atoms as well as for the characteristic emission spectra corresponding to the 3p 5 3d 9 + 3d 7 4p → 3d 8 transitions as well as for the Auger M 4.3 N 1 N 2.3 spectra in Kr and N 4.5 O 1 O 2.3 in Xe are given and compared with the same characteristics of the more complete experimental spectra. (orig.)

Are there nuclear contributions to gamma ray burst spectra

International Nuclear Information System (INIS)

Matz, S.M.; Chupp, E.L.; Forrest, D.J.; Share, G.H.; Nolan, P.L.; Rieger, E.

1984-01-01

We have examined the spectra of 38 γ-ray bursts observed by the Gamma Ray Spectrometer (GRS) on the Solar Maximum Mission (SMM) satellite for evidence of a nuclear contribution to the high energy flux. A sum of spectra from the nine bursts with detectable flux >4 MeV suggests but does not require a drop-off above 7 MeV. A cutoff between 7 and 8 MeV is consistent with a high energy spectrum dominated by nuclear lines

CompAZ Parametrization of the Luminosity Spectra for the Photon Collider

CERN Document Server

Zarnecki, A F

2003-01-01

A simple model, based on the analytical formula for the Compton scattering, is proposed to describe the realistic photon-energy spectra for the Photon Collider at TESLA. Parameters of the model are obtained from the full simulation of the beam by V. Telnov, which includes nonlinear corrections and contributions of higher order processes. Photon energy distribution and polarization, in the high energy part of the spectra, are well reproduced. Our model can be used for a Monte Carlo simulation of gamma-gamma events at various energies and for direct cross-section calculations.

Planck Early Results. XV. Spectral Energy Distributions and Radio Continuum Spectra of Northern Extragalactic Radio Sources

Science.gov (United States)

Aatrokoski, J.; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Amaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.;

New Gener. High-Energy Spectra of the Blazar 3C 279 with XMM-Newton and GLAST

Science.gov (United States)

Collmar, Werner

2007-10-01

We propose two 20 ksec XMM-Newton observations of the X-ray bright gamma-ray blazar 3C~279 simultaneous with GLAST/LAT. The main goal is to measure its X-ray properties (spectrum, variability) in order to (1) improve our knowledge on the X-ray emission of the blazar, and (2) to supplement and correlate them to simultaneous GLAST/LAT Gamma-ray observations (30 MeV-300 GeV). Simultaneous GLAST observations of 3C 279 are guaranteed (assuming proper operation then). The high-energy data will be supplemented by ground-based measurements, adding finally up to multifrequency spectra which have unprecedented accuracy and will extend up to high-energy gamma-rays. Such high-quality SEDs will provide severe constraints on their modeling and have the potential to discriminate among models.

Unusual features of proton and α-spectra from low-energy heavy-ion ...

Indian Academy of Sciences (India)

Home; Journals; Pramana – Journal of Physics; Volume 75; Issue 1. Unusual features ... Keywords. Proton and α-spectra; heavy-ion reaction; broad structures; nuclear level density. ... The broad structures in the -spectra cannot be fully explained within the statistical model even with the enhanced level density. In this case ...

Construction of Hamiltonians by supervised learning of energy and entanglement spectra

Science.gov (United States)

Fujita, Hiroyuki; Nakagawa, Yuya O.; Sugiura, Sho; Oshikawa, Masaki

2018-02-01

Correlated many-body problems ubiquitously appear in various fields of physics such as condensed matter, nuclear, and statistical physics. However, due to the interplay of the large number of degrees of freedom, it is generically impossible to treat these problems from first principles. Thus the construction of a proper model, namely, effective Hamiltonian, is essential. Here, we propose a simple supervised learning algorithm for constructing Hamiltonians from given energy or entanglement spectra. We apply the proposed scheme to the Hubbard model at the half-filling, and compare the obtained effective low-energy spin model with several analytic results based on the high-order perturbation theory, which have been inconsistent with each other. We also show that our approach can be used to construct the entanglement Hamiltonian of a quantum many-body state from its entanglement spectrum as well. We exemplify this using the ground states of the S =1 /2 two-leg Heisenberg ladders. We observe a qualitative difference between the entanglement Hamiltonians of the two phases (the Haldane and the rung singlet phase) of the model due to the different origin of the entanglement. In the Haldane phase, we find that the entanglement Hamiltonian is nonlocal by nature, and the locality can be restored by introducing the anisotropy and turning the ground state into the large-D phase. Possible applications to the model construction from experimental data and to various problems of strongly correlated systems are discussed.

Electron distribution functions in Io plasma torus

International Nuclear Information System (INIS)

Boev, A.G.

2003-01-01

Electron distribution functions measured by the Voyager 1 in different shares of the Io plasma torus are explained. It is proved that their suprathermal tails are formed by the electrical field induced by the 'Jupiter wind'. The Maxwellian parts of all these spectra characterize thermal equilibrium populations of electrons and the radiation of exited ions

The new NIST atomic spectra database

International Nuclear Information System (INIS)

Kelleher, D.E.; Martin, W.C.; Wiese, W.L.; Sugar, J.; Fuhr, J.R.; Olsen, K.; Musgrove, A.; Mohr, P.J.; Reader, J.; Dalton, G.R.

1999-01-01

The new atomic spectra database (ASD), Version 2.0, of the National Institute of Standards and Technology (NIST) contains significantly more data and covers a wider range of atomic and ionic transitions and energy levels than earlier versions. All data are integrated. It also has a new user interface and search engine. ASD contains spectral reference data which have been critically evaluated and compiled by NIST. Version 2.0 contains data on 900 spectra, with about 70000 energy levels and 91000 lines ranging from about 1 Aangstroem to 200 micrometers, roughly half of which have transition probabilities with estimated uncertainties. References to the NIST compilations and original data sources are listed in the ASD bibliography. A detailed ''Help'' file serves as a user's manual, and full search and filter capabilities are provided. (orig.)

Synchrotron brightness distribution of turbulent radio jets

International Nuclear Information System (INIS)

Henriksen, R.N.; Bridle, A.H.; Chan, K.L.

1982-01-01

In this paper we introduce the notion of radio jets as turbulent mixing regions. We further propose that the essential small-scale viscous dissipation in these jets is by Lighthill emission of MHD waves and by their subsequent strong damping due, at least partly, to gyroresonant acceleration of suprathermal particles. The equilibrium eddy, wave, and particle spectra are not found exactly in this paper but the problem is defined and rough estimates of the spectra are given to aid in the observational interpretation

Automated complex spectra processing of actinide α-radiation

International Nuclear Information System (INIS)

Anichenkov, S.V.; Popov, Yu.S.; Tselishchev, I.V.; Mishenev, V.B.; Timofeev, G.A.

1989-01-01

Earlier described algorithms of automated processing of complex α - spectra of actinides with the use of Ehlektronika D3-28 computer line, connected with ICA-070 multichannel amplitude pulse analyzer, were realized. The developed program enables to calculated peak intensity and the relative isotope content, to conduct energy calibration of spectra, to calculate peak center of gravity and energy resolution, to perform integral counting in particular part of the spectrum. Error of the method of automated processing depens on the degree of spectrum complication and lies within the limits of 1-12%. 8 refs.; 4 figs.; 2 tabs

Effect of source encapsulation on the energy spectra of sup 192 Ir and sup 137 Cs seed sources

Energy Technology Data Exchange (ETDEWEB)

Thomason, C [Wisconsin Univ., Madison, WI (USA). Dept. of Medical Physics; Mackie, T R [Wisconsin Univ., Madison, WI (USA). Dept. of Medical Physics Wisconsin Univ., Madison, WI (USA). Dept. of Human Oncology; Lindstrom, M J [Wisconsin Univ., Madison, WI (USA). Biostatistics Center

1991-04-01

The effect of source encapsulation on the energy spectra of {sup 192}Ir and {sup 137}Cs seed sources, both with stainless steel and with platinum encapsulation, was determined from results of Monte Carlo simulation. The fractional scatter dose around these sources has also been determined from Monte Carlo simulation. The platinum-encapsulated {sup 192}Ir source exhibited greater attenuation of the primary spectrum, as expected, and, consistent with this greater attenuation, exhibited more scattered radiation. Significantly less scatter was seen with the {sup 137}Cs source than with either {sup 192}Ir source, as is consistent with the higher-energy photons from {sup 137}Cs. (author).

Effect of γ-softness on continuum gamma-ray spectra

International Nuclear Information System (INIS)

Hamamoto, I.; Onishi, N.

1985-01-01

In the case that a nuclear system has a large fluctuation in the direction of triaxiality, we examine the possible feature expected to appear in the continuum gamma-ray spectra, especially a possibility of the filling in the central valley of the two-dimensional gamma-energy coincidence spectra. (orig.)

Mass spectrometric evidence for suprathermal ionization in an inductively coupled argon plasma

International Nuclear Information System (INIS)

Houk, R.S.; Svec, H.J.; Fassel, V.A.

1981-01-01

Mass spectra have been obtained of species in the axial channel of an inductively coupled argon plasma by extracting ions from the inductively coupled plasma into a vacuum system housing a quadrupole mass spectrometer. Ionization temperatures (T/sub ion/) are obtained from relative count rates of m/z-resolved ions according to two general types of ionization equilibrium considerations: (a) the radio of doubly/singly charged ions of the same element, and (b) the ratio of singly charged ions from two elements of different ionization energy. The T/sub ion/ values derived from measurement of Ar +2 /Ar + , Ba +2 /Ba + , Sr +2 /Sr + , and Cd + /I + are all greater than those expected from excitation temperatures measured by other workers. The latter three values for T/sub ion/ are in reasonable agreement with values obtained by optical spectrometry for a variety of argon inductively coupled plasmas

The structure of BPS spectra

Science.gov (United States)

Longhi, Pietro

In this thesis we develop and apply novel techniques for analyzing BPS spectra of supersymmetric quantum field theories of class S. By a combination of wall-crossing, spectral networks and quiver methods we explore the BPS spectra of higher rank four-dimensional N = 2 super Yang-Mills, uncovering surprising new phenomena. Focusing on the SU(3) case, we prove the existence of wild BPS spectra in field theory, featuring BPS states of higher spin whose degeneracies grow exponentially with the energy. The occurrence of wild BPS states is surprising because it appears to be in tension with physical expectations on the behavior of the entropy as a function of the energy scale. The solution to this puzzle comes from realizing that the size of wild BPS states grows rapidly with their mass, and carefully analyzing the volume-dependence of the entropy of BPS states. We also find some interesting structures underlying wild BPS spectra, such as a Regge-like relation between the maximal spin of a BPS multiplet and the square of its mass, and the existence of a universal asymptotic distribution of spin-j irreps within a multiplet of given charge. We also extend the spectral networks construction by introducing a refinement in the topological classification of 2d-4d BPS states, and identifying their spin with a topological invariant known as the "writhe of soliton paths". A careful analysis of the 2d-4d wall-crossing behavior of this refined data reveals that it is described by motivic Kontsevich-Soibelman transformations, controlled by the Protected Spin Character, a protected deformation of the BPS index encoding the spin of BPS states. Our construction opens the way for the systematic study of refined BPS spectra in class S theories. We apply it to several examples, including ones featuring wild BPS spectra, where we find an interesting relation between spectral networks and certain functional equations. For class S theories of A 1 type, we derive an alternative technique for

Non-universal spectra of ultra-high energy cosmic ray primaries and secondaries in a structured universe

International Nuclear Information System (INIS)

Sigl, Guenter

2007-01-01

Analytical calculations of extra-galactic cosmic ray spectra above ∼ 10 17 eV are often performed assuming continuous source distributions, giving rise to spectra that depend little on the propagation mode, be it rectilinear or diffusive. We perform trajectory simulations for proton primaries in the probably more realistic case of discrete sources with a density of ∼ 10 -5 Mpc -3 . We find two considerable non-universal effects that depend on source distributions and magnetic fields: First, the primary extra-galactic cosmic ray flux can become strongly suppressed below a few 10 18 eV due to partial confinement in magnetic fields surrounding sources. Second, the secondary photon to primary cosmic ray flux ratio between ≅ 3 x 10 18 eV and ≅ 10 20 eV decreases with decreasing source density and increasing magnetization. As a consequence, in acceleration scenarios for the origin of highest energy cosmic rays the fraction of secondary photons may be difficult to detect even for experiments such as Pierre Auger. The cosmogenic neutrino flux does not significantly depend on source density and magnetization. (author)

Power spectra of currents off Bombay

Digital Repository Service at National Institute of Oceanography (India)

Varkey, M.J.

Current measurements were carried out using a recording current meter across the continental shelf off Bombay, Maharashtra, India at 4 stations from an anchored ship. Power spectra were computed for selected lengths of records. Spectral energy...

EBS/C proton spectra from a virgin diamond crystal

Energy Technology Data Exchange (ETDEWEB)

Erich, M., E-mail: marko.erich@gmail.com [Laboratory of Physics, Vinča Institute of Nuclear Sciences, University of Belgrade, PO Box 552, Belgrade (Serbia); Kokkoris, M. [Department of Physics, National Technical University of Athens, Zografou Campus 157 80, Athens (Greece); Fazinić, S. [Laboratory for Ion Beam Interactions, Department of Experimental Physics, Institute Ruđer Bošković, Bijenička cesta 54, 10000 Zagreb (Croatia); Petrović, S. [Laboratory of Physics, Vinča Institute of Nuclear Sciences, University of Belgrade, PO Box 552, Belgrade (Serbia)

2016-08-15

In the present work, elastic backscattering channeling spectra, EBS/C, of protons in a 〈1 0 0〉 diamond crystal were experimentally and theoretically studied via a new computer simulation code. Proton incident energies for EBS/C spectra were in the energy range from 1.0 MeV to 1.9 MeV. The energy range was chosen in order to explore a distinct strong resonance of the {sup 12}C(p,p{sub 0}){sup 12}C elastic scattering at 1737 keV. The computer simulation code applied for the fitting of the experimental spectra in the random mode was compared with the corresponding SIMNRA results. In the channeling mode, it assumes a Gompertz type sigmoidal dechanneling function, which has two fitting parameters, x{sub c} and k, the dechanneling range and rate, respectively. It also uses α, ratio of the channeling to random energy losses, as a fitting parameter. It was observed that x{sub c} increases, k decreases and α stays relatively constant with the proton incident energy. These observations confirm the physical interpretation of the fitting parameters. Also, they constitute the basics for the further development of the code for the quantification of induced amorphization and depth profiling of implanted ions.

Lα1 satellites in X-ray emission spectra of higher - Z elements

International Nuclear Information System (INIS)

Poonia, S.

2004-01-01

Full text: The X-ray satellite spectra arising due to 2p 3/2 -1 3x -1 - 3x -1 3d -1 (x ≡ s, p, d) transition array, in elements with Z 74 to 92, have been calculated. While the energies of various transitions of the array have been determined by using available Hartree-Fock-Slater data on 1s -1 - 2p -1 3x -1 and 2p 3/2 -1 - 3x -1 , 3x' -1 Auger transition energies and their relative intensities have been estimated by considering cross - sections of singly ionized 2x -1 (x ≡ s, p) states and then of subsequent Coster-Kronig and shake off processes. The calculated spectra have been compared with the measured satellite energies in Lα1 spectra. Their intense peaks have been identified as the observed satellite lines. The one to one correspondence between the peaks in calculated spectra and the satellites in measured spectra has been established on the basis of the agreement between the separations in the peak energies and those in the measured satellite energies. It has been established that three satellites observed in the Lα 1 region of the X-ray spectra of various elements and named α', α ix and α x in order of increasing energy are mainly emitted by 2p 3/2 -1 3d -1 - 3d -2 transitions. It is observed that the satellite α' in all these spectra can be assigned to the superposition of 3 F 4 - 3 F 4 transition and that this must be most intense one out of all these satellites, contributing in order of decreasing intensity. The line α ix , has been assigned to mainly the 1 F 3 - 1 G 4 , 1 P 1 - 1 D 2 and 1 F 3 - 1 D 2 transitions. Finally, the satellite α x , reported in the spectra of elements with Z = 74-92, has been associated with the transition 3 D 3 - 3 F 4 . The possible contributions of other transitions of the 2p 3/2 -1 3x -1 - 3x -1 3d -1 (x ≡ s, p, d) array having appreciable intensities, have also been discussed

Monte Carlo Simulations of Electron Energy-Loss Spectra with the Addition of Fine Structure from Density Functional Theory Calculations.

Science.gov (United States)

Attarian Shandiz, Mohammad; Guinel, Maxime J-F; Ahmadi, Majid; Gauvin, Raynald

2016-02-01

A new approach is presented to introduce the fine structure of core-loss excitations into the electron energy-loss spectra of ionization edges by Monte Carlo simulations based on an optical oscillator model. The optical oscillator strength is refined using the calculated electron energy-loss near-edge structure by density functional theory calculations. This approach can predict the effects of multiple scattering and thickness on the fine structure of ionization edges. In addition, effects of the fitting range for background removal and the integration range under the ionization edge on signal-to-noise ratio are investigated.

Database for Simulation of Electron Spectra for Surface Analysis (SESSA)Database for Simulation of Electron Spectra for Surface Analysis (SESSA)

Science.gov (United States)

SRD 100 Database for Simulation of Electron Spectra for Surface Analysis (SESSA)Database for Simulation of Electron Spectra for Surface Analysis (SESSA) (PC database for purchase)   This database has been designed to facilitate quantitative interpretation of Auger-electron and X-ray photoelectron spectra and to improve the accuracy of quantitation in routine analysis. The database contains all physical data needed to perform quantitative interpretation of an electron spectrum for a thin-film specimen of given composition. A simulation module provides an estimate of peak intensities as well as the energy and angular distributions of the emitted electron flux.

Silicon Drift Detector response function for PIXE spectra fitting

Science.gov (United States)

Calzolai, G.; Tapinassi, S.; Chiari, M.; Giannoni, M.; Nava, S.; Pazzi, G.; Lucarelli, F.

2018-02-01

The correct determination of the X-ray peak areas in PIXE spectra by fitting with a computer program depends crucially on accurate parameterization of the detector peak response function. In the Guelph PIXE software package, GUPIXWin, one of the most used PIXE spectra analysis code, the response of a semiconductor detector to monochromatic X-ray radiation is described by a linear combination of several analytical functions: a Gaussian profile for the X-ray line itself, and additional tail contributions (exponential tails and step functions) on the low-energy side of the X-ray line to describe incomplete charge collection effects. The literature on the spectral response of silicon X-ray detectors for PIXE applications is rather scarce, in particular data for Silicon Drift Detectors (SDD) and for a large range of X-ray energies are missing. Using a set of analytical functions, the SDD response functions were satisfactorily reproduced for the X-ray energy range 1-15 keV. The behaviour of the parameters involved in the SDD tailing functions with X-ray energy is described by simple polynomial functions, which permit an easy implementation in PIXE spectra fitting codes.

Systematic evaluation of prompt neutron spectra in fission

International Nuclear Information System (INIS)

Osawa, Takaaki

1995-01-01

To create the nuclear data fail JEND-32, the prompt fission neutron spectra X(E) of 233 U, 235 U, 238 U and 239 Pu were reevaluated and some improvement were added to the calculation models. We tried to extend the calculation method of fission spectra of nuclides with poor measurement data in consideration of increasing the importance of nuclear data of minor actinoids. We improved and extended the following five points. (1) On JENDL-3.1, the fission spectra of principal fissible materials had been calculated by the Modland-Nix model which the neutron emissions of fragments were calculated under the approximation of the constant inverse process cross section. In the paper, the spectra were calculated by the use of the inverse process cross section depend on the energy obtained by the calculation of the optical model. The result showed the increase of low energy components and the softening effect of spectra (2) On JENDL-3.1, the all fission processes were assumed to undergo (n,f) reaction. In the paper, they were calculated by the multi-chance fission such as (n, n'f), (n, 2nf) and (n, 3nf) etc. Softening of the spectra (En > 6 MeV) was obtained by this method. (3) The level density parameter (LDP) has been assumed as a = A/C in either case of light fragment (LF) and heavy fragment (HF) in the original Madland-Nix model. But we used LDP based on the Ignatyuk model under consideration of the shell effects of nuclear fragments, hence the neutron spectra of heavy fragments were hardening. (4) Nuclear temperature of both fragments had been assumed to be the same at original model, but now R T = Tm/TmH was derived to calculate them. The ratio of middle/both side components of spectra was changed. (5) Unknown neutron fission spectra of minor actinide were able to the assumed on the basis of Moriyama-Ohnishi model. (S.Y.)

Time-of-flight spectrometer for the measurement of gamma correlated neutron spectra

International Nuclear Information System (INIS)

Andriashin, A.V.; Devkin, B.V.; Lychagin, A.A.; Minko, J.V.; Mironov, A.N.; Nesterenko, V.S.; Sztaricskai, T.; Petoe, G.; Vasvary, L.

1986-01-01

A time-of-flight spectrometer for the measurement of gamma correlated neutron spectra from (n,xnγ) reactions is described. The operation and the main parameters are discussed. The resolution in the neutron channel is 2.2 ns/m at the 150 keV neutron energy threshold. A simultaneous measurement of the time-of-flight and amplitude distributions makes it possible to study gamma correlated neutron spectra as well as the prompt gamma spectra in coincidence with selected energy neutrons. In order to test the spectrometer, measurements of the neutron spectrum in coincidence with the 846 keV gamma line of 56 Fe were carried out at an incident neutron energy of 14.1 MeV. (Auth.)

Interpretation of monoclinic hafnia valence electron energy-loss spectra by time-dependent density functional theory

Science.gov (United States)

Hung, L.; Guedj, C.; Bernier, N.; Blaise, P.; Olevano, V.; Sottile, F.

2016-04-01

We present the valence electron energy-loss spectrum and the dielectric function of monoclinic hafnia (m -HfO2) obtained from time-dependent density-functional theory (TDDFT) predictions and compared to energy-filtered spectroscopic imaging measurements in a high-resolution transmission-electron microscope. Fermi's golden rule density-functional theory (DFT) calculations can capture the qualitative features of the energy-loss spectrum, but we find that TDDFT, which accounts for local-field effects, provides nearly quantitative agreement with experiment. Using the DFT density of states and TDDFT dielectric functions, we characterize the excitations that result in the m -HfO2 energy-loss spectrum. The sole plasmon occurs between 13 and 16 eV, although the peaks ˜28 and above 40 eV are also due to collective excitations. We furthermore elaborate on the first-principles techniques used, their accuracy, and remaining discrepancies among spectra. More specifically, we assess the influence of Hf semicore electrons (5 p and 4 f ) on the energy-loss spectrum, and find that the inclusion of transitions from the 4 f band damps the energy-loss intensity in the region above 13 eV. We study the impact of many-body effects in a DFT framework using the adiabatic local-density approximation (ALDA) exchange-correlation kernel, as well as from a many-body perspective using "scissors operators" matched to an ab initio G W calculation to account for self-energy corrections. These results demonstrate some cancellation of errors between self-energy and excitonic effects, even for excitations from the Hf 4 f shell. We also simulate the dispersion with increasing momentum transfer for plasmon and collective excitation peaks.

Production spectra of zero-degree neutral particles measured by the LHCf experiment

Directory of Open Access Journals (Sweden)

Tiberio A.

2017-01-01

In this paper, latest published physics results from p-p and p-Pb collisions (at √s = 7, 2.76 TeV and sNN = 5.02 TeV, respectively compared with Monte Carlo predictions of DPMJET, EPOS, PYTHIA, QGSJET and SIBYLL event generators will be presented. In particular, the inclusive energy spectra of neutrons in p-p collisions and the transverse and longitudinal momentum spectra of neutral pions for different pseudo-rapidity ranges in p-p and p-Pb collisions will be shown; then, test of Feynman scaling hypothesis using neutral pion spectra will be discussed. Preliminary results of photon inclusive energy spectra in p-p collisions at √s = 13 TeV will be also presented.

Resonant Ni and Fe KLL Auger spectra photoexcited from NiFe alloys

International Nuclear Information System (INIS)

Koever, L.; Cserny, I.; Berenyi, Z.; Egri, S.; Novak, M.

2005-01-01

Complete text of publication follows. KLL Auger spectra of 3d transition metal atoms in solid environment, measured using high energy resolution, give an insight into the details of the local electronic structure surrounding the particular atoms emitting the signal Auger electrons. Fine tuning the energy of the exciting monochromatic photons across the K-absorption edge, features characteristic to resonant phenomena can be identified in the spectra. The shapes of the resonantly photoexcited KLL Auger spectra induced from 3d transition metals and alloys are well interpreted by the single step model of the Auger process, based on the resonant scattering theory. The peak shapes are strongly influenced by the 4p partial density of unoccupied electronic states around the excited atom. High energy resolution studies of KLL Auger spectra of 3d transition metals using laboratory X-ray sources, however, request very demanding experiments and yield spectra of limited statistical quality making the evaluation of the fine details in the spectra difficult. The Tunable High Energy XPS (THE- XPS) instrument at BW2 offers optimum photon x and energy resolution for spectroscopy of deep core Auger transitions. For the present measurements high purity polycrystalline Ni and Fe sheets as well as NiFe alloy samples of different compositions (Ni 80 Fe 20 , Ni 50 Fe 50 , Ni 20 Fe 80 ) were used. The surfaces of the samples were cleaned by in-situ argon ion sputtering. The measurements of the Ni and Fe KL 23 L 23 Auger spectra of the metal and alloy samples were performed with the THE-XPS instrument using high electron energy resolution (0.2 eV). In Fig.1, the measured Fe KL 23 L 23 spectrum, photoexcited at the Fe K absorption edge from Fe metal, is compared with the respective spectrum excited from a Ni 50 Fe 50 alloy. A significant broadening of the 1 D 2 peak and an enhancement of the spectral intensity at the low energy loss part of this peak observed in the alloy sample, while the

Conductance spectra of asymmetric ferromagnet/ferromagnet/ferromagnet junctions

Science.gov (United States)

Pasanai, K.

2017-01-01

A theory of tunneling spectroscopy of ferromagnet/ferromagnet/ferromagnet junctions was studied. We applied a delta-functional approximation for the interface scattering properties under a one-dimensional system of a free electron approach. The reflection and transmission probabilities were calculated in the ballistic regime, and the conductance spectra were then calculated using the Landauer formulation. The magnetization directions were set to be either parallel (P) or anti-parallel (AP) alignments, for comparison. We found that the conductance spectra was suppressed when increasing the interfacial scattering at the interfaces. Moreover, the electron could exhibit direct transmission when the thickness was rather thin. Thus, there was no oscillation in this case. However, in the case of a thick layer the conductance spectra oscillated, and this oscillation was most prominent when the middle layer thickness increased. In the case of direct transmission, the conductance spectra of P and AP systems were definitely suppressed with increased exchange energy of the middle ferromagnet. This also refers to an increase in the magnetoresistance of the junction. In the case of oscillatory behavior, the positions of the resonance peaks were changed as the exchange energy was changed.

The TDF System for Thermonuclear Plasma Reaction Rates, Mean Energies and Two-Body Final State Particle Spectra

International Nuclear Information System (INIS)

Warshaw, S I

2001-01-01

The rate of thermonuclear reactions in hot plasmas as a function of local plasma temperature determines the way in which thermonuclear ignition and burning proceeds in the plasma. The conventional model approach to calculating these rates is to assume that the reacting nuclei in the plasma are in Maxwellian equilibrium at some well-defined plasma temperature, over which the statistical average of the reaction rate quantity σv is calculated, where σ is the cross-section for the reaction to proceed at the relative velocity v between the reacting particles. This approach is well-understood and is the basis for much nuclear fusion and astrophysical nuclear reaction rate data. The Thermonuclear Data File (TDF) system developed at the Lawrence Livermore National Laboratory (Warshaw 1991), which is the topic of this report, contains data on the Maxwellian-averaged thermonuclear reaction rates for various light nuclear reactions and the correspondingly Maxwellian-averaged energy spectra of the particles in the final state of those reactions as well. This spectral information closely models the output particle and energy distributions in a burning plasma, and therefore leads to more accurate computational treatments of thermonuclear burn, output particle energy deposition and diagnostics, in various contexts. In this report we review and derive the theoretical basis for calculating Maxwellian-averaged thermonuclear reaction rates, mean particle energies, and output particle spectral energy distributions for these reactions in the TDF system. The treatment of the kinematics is non-relativistic. The current version of the TDF system provides exit particle energy spectrum distributions for two-body final state reactions only. In a future report we will discuss and describe how output particle energy spectra for three- and four-body final states can be developed for the TDF system. We also include in this report a description of the algorithmic implementation of the TDF

Core-level spectra and binding energies of transition metal nitrides by non-destructive x-ray photoelectron spectroscopy through capping layers

Energy Technology Data Exchange (ETDEWEB)

Greczynski, G., E-mail: grzgr@ifm.liu.se [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping (Sweden); Primetzhofer, D. [Department of Physics and Astronomy, The Ångström Laboratory, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Lu, J.; Hultman, L. [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-581 83 Linköping (Sweden)

2017-02-28

Highlights: • First non-destructive measurements of XPS core level binding energies for group IVb-VIb transition metal nitrides are presented. • All films are grown under the same conditions and analyzed in the same instrument, providing a useful reference for future XPS studies. • Extracted core level BE values are more reliable than those obtained from sputter-cleaned N-deficient surfaces. • Comparison to Ar+-etched surfaces reveals that even mild etching conditions result in the formation of a nitrogen-deficient surface layer. • The N/metal concentration ratios from capped samples are found to be 25-90% higher than those from the corresponding ion-etched surfaces. - Abstract: We present the first measurements of x-ray photoelectron spectroscopy (XPS) core level binding energies (BE:s) for the widely-applicable group IVb-VIb polycrystalline transition metal nitrides (TMN’s) TiN, VN, CrN, ZrN, NbN, MoN, HfN, TaN, and WN as well as AlN and SiN, which are common components in the TMN-based alloy systems. Nitride thin film samples were grown at 400 °C by reactive dc magnetron sputtering from elemental targets in Ar/N{sub 2} atmosphere. For XPS measurements, layers are either (i) Ar{sup +} ion-etched to remove surface oxides resulting from the air exposure during sample transfer from the growth chamber into the XPS system, or (ii) in situ capped with a few nm thick Cr or W overlayers in the deposition system prior to air-exposure and loading into the XPS instrument. Film elemental composition and phase content is thoroughly characterized with time-of-flight elastic recoil detection analysis (ToF-E ERDA), Rutherford backscattering spectrometry (RBS), and x-ray diffraction. High energy resolution core level XPS spectra acquired with monochromatic Al Kα radiation on the ISO-calibrated instrument reveal that even mild etching conditions result in the formation of a nitrogen-deficient surface layer that substantially affects the extracted binding energy

Core-level spectra and binding energies of transition metal nitrides by non-destructive x-ray photoelectron spectroscopy through capping layers

International Nuclear Information System (INIS)

Greczynski, G.; Primetzhofer, D.; Lu, J.; Hultman, L.

2017-01-01

Highlights: • First non-destructive measurements of XPS core level binding energies for group IVb-VIb transition metal nitrides are presented. • All films are grown under the same conditions and analyzed in the same instrument, providing a useful reference for future XPS studies. • Extracted core level BE values are more reliable than those obtained from sputter-cleaned N-deficient surfaces. • Comparison to Ar+-etched surfaces reveals that even mild etching conditions result in the formation of a nitrogen-deficient surface layer. • The N/metal concentration ratios from capped samples are found to be 25-90% higher than those from the corresponding ion-etched surfaces. - Abstract: We present the first measurements of x-ray photoelectron spectroscopy (XPS) core level binding energies (BE:s) for the widely-applicable group IVb-VIb polycrystalline transition metal nitrides (TMN’s) TiN, VN, CrN, ZrN, NbN, MoN, HfN, TaN, and WN as well as AlN and SiN, which are common components in the TMN-based alloy systems. Nitride thin film samples were grown at 400 °C by reactive dc magnetron sputtering from elemental targets in Ar/N 2 atmosphere. For XPS measurements, layers are either (i) Ar + ion-etched to remove surface oxides resulting from the air exposure during sample transfer from the growth chamber into the XPS system, or (ii) in situ capped with a few nm thick Cr or W overlayers in the deposition system prior to air-exposure and loading into the XPS instrument. Film elemental composition and phase content is thoroughly characterized with time-of-flight elastic recoil detection analysis (ToF-E ERDA), Rutherford backscattering spectrometry (RBS), and x-ray diffraction. High energy resolution core level XPS spectra acquired with monochromatic Al Kα radiation on the ISO-calibrated instrument reveal that even mild etching conditions result in the formation of a nitrogen-deficient surface layer that substantially affects the extracted binding energy values. These

Principal spectra describing magnetooptic permittivity tensor in cubic crystals

Energy Technology Data Exchange (ETDEWEB)

Hamrlová, Jana [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Legut, Dominik [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Veis, Martin [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Pištora, Jaromír [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Hamrle, Jaroslav, E-mail: jaroslav.hamrle@vsb.cz [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Department of Physics, VSB – Technical University of Ostrava, 17. listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic)

2016-12-15

We provide unified phenomenological description of magnetooptic effects being linear and quadratic in magnetization. The description is based on few principal spectra, describing elements of permittivity tensor up to the second order in magnetization. Each permittivity tensor element for any magnetization direction and any sample surface orientation is simply determined by weighted summation of the principal spectra, where weights are given by crystallographic and magnetization orientations. The number of principal spectra depends on the symmetry of the crystal. In cubic crystals owning point symmetry we need only four principal spectra. Here, the principal spectra are expressed by ab initio calculations for bcc Fe, fcc Co and fcc Ni in optical range as well as in hard and soft x-ray energy range, i.e. at the 2p- and 3p-edges. We also express principal spectra analytically using modified Kubo formula.

Time evolution of the characteristic electron energy losses spectra of the electrons scattered on polycrystal samples of Al mechanically cleaned in vacuum

International Nuclear Information System (INIS)

Szczesny, R.; Baranowski, A.; Beliczynski, J.

1982-01-01

Measurements by the reflection technique of characteristic electron energy losses (CEEL) with a primary electron beam of energy E 0 =1 keV have been carried out on polycrystal samples of Al. The sample surfaces have been mechanically cleaned in a dinamical vacuum of the order 10 -6 Tr before each measurement. The CEEL spectra have been corrected for the resolving power of the apparatus by the deconvolution method. We have ascertained that the measuring technique and elaboration data method are useful for quickly obtaining the plasmon energy loss spectrum for an investigated material. (author)

Measurements of the prompt neutron spectra in 233U, 235U, 239Pu thermal neutron fission in the energy range of 0.01-5 MeV and in 252Cf spontaneous fission in the energy range of 0.01-10 MeV

International Nuclear Information System (INIS)

Starostov, B.I.; Semenov, A.F.; Nefedov, V.N.

1978-01-01

The measurement results on the prompt neutron spectra in 233 U, 235 U, 239 Pu thermal neutron fission in the energy range of 0.01-5 MeV and in 252 Cf spontaneous fission in the energy range of 0.01-10 MeV are presented. The time-of-flight method was used. The exceeding of the spectra over the Maxwell distributions is observed at E 252 Cf neutron fission spectra. The spectra analysis was performed after normalization of the spectra and corresponding Maxwell distributions for one and the same area. In the range of 0.05-0.22 MeV the yield of 235 U + nsub(t) fission neutrons is approximately 8 and approximately 15 % greater than the yield of 252 Cf and 239 Pu + nsub(t) fission neutrons, respectively. In the range of 0.3-1.2 MeV the yield of 235 U + nsub(t) fission neutrons is 8 % greater than the fission neutron yield in case of 239 Pu + nsub(t) fission. The 235 U + nsub(t) and 233 U + nsub(t) fission neutron spectra do not differ from one another in the 0.05-0.6 MeV range

Coordinated observations of electron energy spectra and electrostatic cyclotron waves during diffuse auroras

International Nuclear Information System (INIS)

Fontaine, D.; Perraut, S.; Cornilleau-Wehrlin, N.; Aparicio, B.; Bosqued, J.M.; Rodgers, D.

1986-01-01

An auroral precipitation event lasting several hours in the dusk sector on June 2, 1982 is studied in conjunction with three instruments: the EISCAT European Incoherent Scatter radar based in Scandinavia, the GEOS-2 European geostationary spacecraft, and the ARCAD-3 French-Soviet polar spacecraft. Electron energy spectra between about 1 and 10 keV, computed from EISCAT measurements, were in agreement, during a diffuse aurora period, with direct observations onboard ARCAD-3, and also with the plasma sheet component (3-10 keV) measured onboard GEOS-2 and available at large pitch-angles. This last comparison suggested the quasi-isotropy of equatorial electron fluxes. The electrostatic electron cyclotron harmonic waves, also observed onboard GEOS-2, were not found to be intense enough to cause by themselves the strong pitch-angle diffusion of electrons of a few keV

Secondary graviton spectra and waterfall-like fields

OpenAIRE

Giovannini, Massimo

2010-01-01

The secondary spectra of the gravitons induced by a waterfall-like field are computed and the general bounds on the spectral energy density of the tensor modes of the geometry are translated into explicit constraints on the amplitude and slope of the waterfall spectrum. The obtained results are compared with the primary gravitational wave spectra of the concordance model and of its neighboring extensions as well as with the direct Ligo/Virgo bounds on stochastic backgrounds of relic gravitons...

Proposal and Evaluation of Subordinate Standard Solar Irradiance Spectra for Applications in Solar Energy Systems

Energy Technology Data Exchange (ETDEWEB)

Habte, Aron M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jessen, Wilko [German Aerospace Center (DLR); Wilbert, Stefan [German Aerospace Center (DLR); Gueymard, Christian A. [Solar Consulting Services; Polo, Jesus [CIEMAT; Bian, Zeqiang [China Meteorological Administration; Driesse, Anton [Photovoltaic Performance Labs; Marzo, Aitor [University of Antofagasta; Armstrong, Peter [Masdar Institute of Science & Technology; Vignola, Frank [University of Oregon; Ramirez, Lourdes [CIEMAT

2018-04-01

Reference solar irradiance spectra are needed to specify key parameters of solar technologies such as photovoltaic cell efficiency, in a comparable way. The IEC 60904-3 and ASTM G173 standards present such spectra for Direct Normal Irradiance (DNI) and Global Tilted Irradiance (GTI) on a 37 degrees tilted sun-facing surface for one set of clear-sky conditions with an air mass of 1.5 and low aerosol content. The IEC/G173 standard spectra are the widely accepted references for these purposes. Hence, the authors support the future replacement of the outdated ISO 9845 spectra with the IEC spectra within the ongoing update of this ISO standard. The use of a single reference spectrum per component of irradiance is important for clarity when comparing and rating solar devices such as PV cells. However, at some locations the average spectra can differ strongly from those defined in the IEC/G173 standards due to widely different atmospheric conditions and collector tilt angles. Therefore, additional subordinate standard spectra for other atmospheric conditions and tilt angles are of interest for a rough comparison of product performance under representative field conditions, in addition to using the main standard spectrum for product certification under standard test conditions. This simplifies the product selection for solar power systems when a fully-detailed performance analysis is not feasible (e.g. small installations). Also, the effort for a detailed yield analyses can be reduced by decreasing the number of initial product options. After appropriate testing, this contribution suggests a number of additional spectra related to eight sets of atmospheric conditions and tilt angles that are currently considered within ASTM and ISO working groups. The additional spectra, called subordinate standard spectra, are motivated by significant spectral mismatches compared to the IEC/G173 spectra (up to 6.5%, for PV at 37 degrees tilt and 10-15% for CPV). These mismatches

Measurement of day and night neutrino energy spectra at SNO and constraints on neutrino mixing parameters

International Nuclear Information System (INIS)

Ahmad, Q.R.; Bullard, T.V.; Cox, G.A.; Duba, C.A.; Formaggio, J.A.; Germani, J.V.; Hamian, A.A.; Hazama, R.; Heeger, K.M.; Howe, M.; Kazkaz, K.; Manor, J.; Meijer Drees, R.; Orrell, J.L.; Schaffer, K.K.; Smith, M.W.E.; Steiger, T.D.; Stonehill, L.C.; Allen, R.C.; Buehler, G.

2002-01-01

The Sudbury Neutrino Observatory (SNO) has measured day and night solar neutrino energy spectra and rates. For charged current events, assuming an undistorted 8 B spectrum, the night minus day rate is 14.0%±6.3% +1.5 -1.4 % of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the ν e asymmetry is found to be 7.0%±4.9% +1.3 -1.2 % . A global solar neutrino analysis in terms of matter-enhanced oscillations of two active flavors strongly favors the large mixing angle solution

Proton and Helium Spectra from the CREAM-III Flight

Energy Technology Data Exchange (ETDEWEB)

Yoon, Y. S.; Han, J. H.; Kim, K. C.; Kim, M. H.; Lee, M. H.; Lee, S. E. [Institute for Physical Science and Technology, University of Maryland, College Park, MD, 20742 (United States); Anderson, T.; Conklin, N. B.; Coutu, S.; Mognet, S. I. [Department of Physics, Penn State University, University Park, PA 16802 (United States); Barrau, A.; Derome, L. [Laboratoire de Physique Subatomique et Cosmologie, Grenoble (France); Jeon, J. A.; Lee, H. Y.; Lee, J.; Park, I. H. [Department of Physics, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Link, J. T.; Mitchell, J. W. [Astrophysics Space Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Menchaca-Rocha, A. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico (Mexico); Nutter, S. [Department of Physics, Northern Kentucky University, Highland Heights, KY 41099 (United States); and others

2017-04-10

Primary cosmic-ray elemental spectra have been measured with the balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment since 2004. The third CREAM payload (CREAM-III) flew for 29 days during the 2007–2008 Antarctic season. Energies of incident particles above 1 TeV are measured with a calorimeter. Individual elements are clearly separated with a charge resolution of ∼0.12 e (in charge units) and ∼0.14 e for protons and helium nuclei, respectively, using two layers of silicon charge detectors. The measured proton and helium energy spectra at the top of the atmosphere are harder than other existing measurements at a few tens of GeV. The relative abundance of protons to helium nuclei is 9.53 ± 0.03 for the range of 1 TeV/n to 63 TeV/n. This ratio is considerably smaller than other measurements at a few tens of GeV/n. The spectra become softer above ∼20 TeV. However, our statistical uncertainties are large at these energies and more data are needed.

Energy spectra analysis of the four-layer DOI detector for the brain PET scanner: jPET-D4

International Nuclear Information System (INIS)

Yoshida, Eiji; Kitamura, Keishi; Tsuda, Tomoaki; Shibuya, Kengo; Yamaya, Taiga; Inadama, Naoko; Hasegawa, Tomoyuki; Murayama, Hideo

2006-01-01

A depth of interaction (DOI) detector is being developed for the brain PET scanner, jPET-D4. We introduce a light output correction procedure to compensate for variations among the crystal elements in the DOI detector. Under uniform irradiation with 511 keV gamma rays, we estimate the light output of each crystal element by identifying each crystal element, and generate a look-up table (LUT) for light output correction. We evaluate the energy resolution of all crystal elements. The energy resolution of 16% is achieved after light output correction for all crystal elements. The DOI detector can correct light output variations that are related to the DOI. We analyze the crystal position dependence of the energy spectra due to inter-crystal scattering among the multiple crystal elements in the DOI detector. It is highly possible that gamma rays interacting with central crystal elements in the crystal array are absorbed by surrounding crystal elements and the Compton part of the energy spectrum is decreased. Inter-crystal scattering has less impact on the energy resolution of the DOI detector

Exciton spectra of mixed LiH1-xDx crystals

International Nuclear Information System (INIS)

Plekhanov, V.G.

1989-01-01

The results of low-tempertaure experimental investigation of exciton spectra of pure surface of mixed crystals LiH 1-x d x forming the continuous series of a solved solution are presented. The long-wave reflection spectra is formed, as in pure crystals, by excitons of a large radius. The developed structure of spectra of exciton luminiscence consisting mainly of LO-lines, testifies to the intraband Frelich mechanism of free exciton scattering by LO-phonos, playing the considerable role in renormalization of the exciton Rydberg and the energy of interband transitions. Increase of the concentration of deuterium in mixed crystals causes a short-wave shift in the reflection spectrum and luminescence and continuous decrease of LO-phonon energy together with the increase of Rydberg exciton

Krypton K-shell X-ray spectra recorded by the HENEX spectrometer

Energy Technology Data Exchange (ETDEWEB)

Seely, J.F. [Naval Research Laboratory, Space Science Division, Washington DC 20375 (United States)]. E-mail: john.seely@nrl.navy.mil; Back, C.A. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Constantin, C. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Lee, R.W. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Chung, H.-K. [Lawrence Livermore National Laboratory, Livermore CA 94550 (United States); Hudson, L.T. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Szabo, C.I. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Henins, A. [National Institute of Standards and Technology, Gaithersburg MD 20899 (United States); Holland, G.E. [SFA Inc., 9315 Largo Drive West Suite 200, Largo MD 20774 (United States); Atkin, R. [Tiger Innovations, L.L.C., 3610 Vacation Lane, Arlington VA 22207 (United States); Marlin, L. [Naval Research Laboratory, Space Science Division, Washington DC 20375 (United States)

2006-05-15

High-resolution X-ray spectra were recorded by the High-Energy Electronic X-ray (HENEX) spectrometer from a variety of targets irradiated by the Omega laser at the Laboratory for Laser Energetics. The HENEX spectrometer utilizes four reflection crystals covering the 1-20keV energy range and one quartz(10-11) transmission crystal (Laue geometry) covering the 11-40keV range. The time-integrated spectral images were recorded on five CMOS X-ray detectors. In the spectra recorded from krypton-filled gasbag and hohlraum targets, the helium-like K-shell transitions n=1-2, 1-3, and 1-4 appeared in the 13-17keV energy range. A number of additional spectral features were observed at energies lower than the helium-like n=1-3 and n=1-4 transitions. Based on computational simulations of the spectra using the FLYCHK/FLYSPEC codes, which included opacity effects, these additional features are identified to be inner-shell transitions from the Li-like through N-like krypton charge states. The comparisons of the calculated and observed spectra indicate that these transitions are characteristic of the plasma conditions immediately after the laser pulse when the krypton density is 2x10{sup 18}cm{sup -3} and the electron temperature is in the range 2.8-3.2keV. These spectral features represent a new diagnostic for the charge state distribution, the density and electron temperature, and the plasma opacity. Laboratory experiments indicate that it is feasible to record K-shell spectra from gold and higher Z targets in the >60keV energy range using a Ge(220) transmission crystal.

Time-of-flight spectrometer for the measurement of gamma correlated neutron spectra

International Nuclear Information System (INIS)

Andryashin, A.V.; Devlein, B.V.; Lychagin, A.A.; Minko, Y.V.; Mironov, A.N.; Nesterenko, V.S.

1986-01-01

A time-of-flight spectrometer for the measurement of gamma correlated neutron spectra form (n,xnγ) reactions is described. The operation and the main parameters are discussed. The resolution in the neutron channel is 2.2 ns/m at the 150 keV neutron energy threshold. A simultaneous measurement of the time-of-flight and amplitude distributions makes it possible to study gamma correlated neutron spectra as well as the prompt gamma spectra in coincidence with selected energy neutrons. In order to test the spectrometer, measurements of the neutron spectrum in coincidence with the 846 keV gamma line of 56 Fe were carried out at an incident neutron energy of 14.1 MeV. (author). 3 figs., 6 refs

High-energy X-ray spectra of Cygnus XR-1 observed from OSO 8

Science.gov (United States)

Dolan, J. F.; Crannell, C. J.; Dennis, B. R.; Frost, K. J.; Orwig, L. E.

1979-01-01

X-ray spectra of Cygnus XR-1 were measured with the scintillation spectrometer aboard the OSO 8 satellite during a period of one-and-one-half to three weeks in each of the years from 1975 to 1977. Typical spectra of the source between 15 and 250 keV are presented and the spectra are found to be well represented by a single power-law expression whose photon number spectral index is different for the two intensity states that were considered. The observed pivoting effect is consistent with two-temperature accretion disk models of the X-ray emitting region.

Seismic spectra of events at regional distances

International Nuclear Information System (INIS)

Springer, D.L.; Denny, M.D.

1976-01-01

About 40 underground nuclear explosions detonated at the Nevada Test Site (NTS) were chosen for analysis of their spectra and any relationships they might have to source parameters such as yield, depth of burial, etc. The sample covered a large yield range (less than 20 kt to greater than 1 Mt). Broadband (0.05 to 20 Hz) data recorded by the four-station seismic network operated by Lawrence Livermore Laboratory were analyzed in a search for unusual explosion signatures in their spectra. Long time windows (total wave train) as well as shorter windows (for instance, P/sub n/) were used as input to calculate the spectra. Much variation in the spectra of the long windows is typical although some gross features are similar, such as a dominant peak in the microseismic window. The variation is such that selection of corner frequencies is impractical and yield scaling could not be determined. Spectra for one NTS earthquake showed more energy in the short periods (less than 1 sec) as well as in the long periods (greater than 8 sec) compared to those for NTS explosions

Absorption spectra for collinear (nonreactive) H3: Comparison between quantal and classical calculations

International Nuclear Information System (INIS)

Engel, V.; Bacic, Z.; Schinke, R.; Shapiro, M.

1985-01-01

Absorption spectra for the collinear (nonreactive) H+H 2 →H/sup number-sign/ 3 →H+H 2 are calculated quantum mechanically, using the Siegbahn--Liu--Truhlar--Horowitz (SLTH) ab initio potential and a model H( 3 surface as the ground and excited H 3 surface, respectively. They are compared to classical spectra previously computed by Mayne, Poirier, and Polanyi using the same potential energy surfaces [J. Chem. Phys. 80, 4025 (1984)]. The spectra are calculated at several collision energies and for both H+H 2 (v = 0) and H+H 2 (v = 1). The quantal and classical spectra are shown to agree with respect to basic features and trends. Nevertheless, the two sets of spectra differ considerably in their overall appearance because of some purely quantum aspects of the H+H 2 system

On the energy deposition into the plasma for an inverted fireball geometry

Science.gov (United States)

Levko, Dmitry; Gruenwald, Johannes

2017-10-01

Energy deposition into a plasma for an inverted fireball geometry is studied using a self-consistent two-dimensional Particle-in-Cell Monte Carlo collision model. In this model, the cathode is a pin which injects the fixed electron current and the anode is a hollow metal tube covered with the metal grid. We obtain an almost constant ratio between the densities of plasmas generated in the cathode-grid gap and inside the hollow anode. The results of the simulations show that there is no energy exchange between the beam and plasma electrons at low emission currents. For increasing current, however, we observe the increasing coupling between the electron beam and the thermal plasma electrons. This leads to the heating of plasma electrons and the generation of the so-called supra-thermal electrons.

The holistic analysis of gamma-ray spectra in instrumental neutron activation analysis

Energy Technology Data Exchange (ETDEWEB)

Blaauw, M

1993-11-15

The subject is the computerized analysis of the gamma-ray spectra in INAA. This analysis can be separated in three parts: The conversion of the spectra to information on {gamma}-ray energies and their relative intensities (spectrum reduction), the determination of the relation between the intensity of a {gamma}-ray and the amount of the corresponding element present in the sample (standardization) and the attribution of the {gamma}-ray energies to the elements, including the subsequent computation of the amounts of the elements (interpretation). A {gamma}-ray spectrum can be considered to be the linear sum of the {gamma}-ray spectra of the individual radionuclides present in the sample. Knowing the relative activities of the different radionuclides that may be produced by activation of a single element, a {gamma}-ray spectrum in INAA can also be considered to be the linear sum of the spectra of the elements. This principle has hitherto not been used in INAA to analyze the spectra by linear least squares methods, using all {gamma}-ray energies observed in the spectrum. The implementation of this `holistic` approach required that attention be paid to both spectrum reduction, standardization and interpretation. The thesis describes the methods developed for the holistic analysis of {gamma}-ray spectra in INAA, and present results of experimental comparisons between the holistic and other approaches. (orig./HP).

The holistic analysis of gamma-ray spectra in instrumental neutron activation analysis

International Nuclear Information System (INIS)

Blaauw, M.

1993-01-01

The subject is the computerized analysis of the gamma-ray spectra in INAA. This analysis can be separated in three parts: The conversion of the spectra to information on γ-ray energies and their relative intensities (spectrum reduction), the determination of the relation between the intensity of a γ-ray and the amount of the corresponding element present in the sample (standardization) and the attribution of the γ-ray energies to the elements, including the subsequent computation of the amounts of the elements (interpretation). A γ-ray spectrum can be considered to be the linear sum of the γ-ray spectra of the individual radionuclides present in the sample. Knowing the relative activities of the different radionuclides that may be produced by activation of a single element, a γ-ray spectrum in INAA can also be considered to be the linear sum of the spectra of the elements. This principle has hitherto not been used in INAA to analyze the spectra by linear least squares methods, using all γ-ray energies observed in the spectrum. The implementation of this 'holistic' approach required that attention be paid to both spectrum reduction, standardization and interpretation. The thesis describes the methods developed for the holistic analysis of γ-ray spectra in INAA, and present results of experimental comparisons between the holistic and other approaches. (orig./HP)

A high-resolution neutron spectra unfolding method using the Genetic Algorithm technique

CERN Document Server

Mukherjee, B

2002-01-01

The Bonner sphere spectrometers (BSS) are commonly used to determine the neutron spectra within various nuclear facilities. Sophisticated mathematical tools are used to unfold the neutron energy distribution from the output data of the BSS. This paper highlights a novel high-resolution neutron spectra-unfolding method using the Genetic Algorithm (GA) technique. The GA imitates the biological evolution process prevailing in the nature to solve complex optimisation problems. The GA method was utilised to evaluate the neutron energy distribution, average energy, fluence and equivalent dose rates at important work places of a DIDO class research reactor and a high-energy superconducting heavy ion cyclotron. The spectrometer was calibrated with a sup 2 sup 4 sup 1 Am/Be (alpha,n) neutron standard source. The results of the GA method agreed satisfactorily with the results obtained by using the well-known BUNKI neutron spectra unfolding code.

Virtual photon spectra for finite nuclei

International Nuclear Information System (INIS)

Wolynec, E.; Martins, M.N.

1988-01-01

The experimental results of an isochromat of the virtual photon spectrum, obtained by measuring the number of ground-state protons emitted by the 16.28 MeV isobaric analogue state in 90 Zr as a function of electron incident energy in the range 17-105 MeV, are compared with the values predicted by a calculation of the E1 DWBA virtual photon spectra for finite nuclei. It is found that the calculations are in excellent agreement with the experimental results. The DWBA virtual photon spectra for finite nuclei for E2 and M1 multipoles are also assessed. (author) [pt

Fast neutron spectra unfolding with SAND-11 and maximum likelihoed methods

International Nuclear Information System (INIS)

Bondars, Kh.Ya.; Kamnev, V.A.; Lapenas, A.A.; Troshin, V.S.

1980-01-01

Mutual comparison of the methods SAND-II and maximal likeness for neutron spectra determination are represented. Spectra were restored according to the measures reaction rate of ten activation detectors using the device B-2 of the reactor BR-5 behind two thicknesses of steel-graphite shielding: Z=6.5 cm and Z=42.5 cm. The influence of earlier information on the results of neutron spectra determination was studied. Differential and integral energy dependences of neutron flux density for three initial spectra and two cross section libraries (BGS-1 and ZACRSS) are presented. The both methods yield close differential spectra (discrepancies < 10 %) when identical cross section libraries and reference spectra are used

EVIDENCE FOR SECONDARY EMISSION AS THE ORIGIN OF HARD SPECTRA IN TeV BLAZARS

International Nuclear Information System (INIS)

Zheng, Y. G.; Kang, T.

2013-01-01

We develop a model for the possible origin of hard, very high energy (VHE) spectra from a distant blazar. In the model, both the primary photons produced in the source and secondary photons produced outside it contribute to the observed high-energy γ-ray emission. That is, the primary photons are produced through the synchrotron self-Compton process, and the secondary photons are produced through high-energy proton interactions with background photons along the line of sight. We apply the model to a characteristic case of VHE γ-ray emission in the distant blazar 1ES 1101-232. Assuming suitable electron and proton spectra, we obtain excellent fits to the observed spectra of this blazar. This indicated that the surprisingly low attenuation of the high-energy γ-rays, especially the shape of the VHE γ-ray tail of the observed spectra, can be explained by secondary γ-rays produced in interactions of cosmic-ray protons with background photons in intergalactic space.

The thick-target 9Be(d,n) neutron spectra for deuteron energies between 2.6 and 7.0-MeV

International Nuclear Information System (INIS)

Meadows, J.W.

1991-11-01

The measurement of the zero deg. neutron spectra and yields from deuterons incident on thick beryllium metal targets is described. 235 U and 238 U fission ion chambers were used as neutron detectors to span the neutron energy range above 0.05-MeV with a time resolution of ≤ 3 nanosec. Measurements were made for incident deuteron energies from 2.6 to 7.0-MeV, at 0.4-MeV intervals, using time-of-flight techniques with flight paths of 2.7 and 6.8 meters. The results are presented in graphical form and in tables

Determination of the fast neutrons spectra by the Elastic scattering method (n, p)

International Nuclear Information System (INIS)

Elizalde D, J.

1973-01-01

This work consists in determining the fast neutron spectra emitted by a Pu-Be isotopic source. The implemented technique is based in the spectrometry (n, p). This consists in making to fall on a fast neutrons beams (polyenergetic) over a thin film of hydrogenated material, detecting the spectra of emitted protons at a fix angle. The polyethylene film and the used solid state detector are inside of a vacuum chamber. The detector is placed at 30 degree with respect to direction of the incident neutrons beam. The protons spectra is stored in a multichannel. the energy is obtained with the prior calibration of the system. The data processing involves the transformation of the protons spectra observed at the falling on neutrons spectra over the film. The energy of the neutrons is related with that of the protons, according to the collision kinematical equations. The cross section of elastic collision of the neutrons with the hydrogen atoms is obtained from literature. Applying these relations to the observed spectra it is obtained the falling on neutron spectra over the film. (Author)

The secondary neutrons spectra of 235U, 238U for incident energy range 1-2.5 MeV

International Nuclear Information System (INIS)

Kornilov, N.V.; Kagalenko, A.B.; Balitsky, A.V.; Baryba, V.Ja.; Androsenko, P.A.; Androsenko, A.A.

1993-01-01

Spectra of inelastic scattered neutrons and fission neutrons were measured with neutron time of flight spectrometer. The solid tritium target was used as a neutron source. The energy distribution of neutrons on the sample was calculated with Monte-Carlo code, taking into account interaction income protons inside target and reaction kinematics. The detector efficiency was determined with 252 Cf source. The multiple scattering and absorption corrections were calculated with codes packet BRAND. Our results confirm ENDF/B-6 data library. (author)

Emission Spectra of Hydrogen-Seeded Helium Arcjets

National Research Council Canada - National Science Library

Welle, R

2000-01-01

.... This work reports on a recent set of experiments in which emission spectra of the plume of a helium arcjet were acquired and analyzed to obtain information on the internal energy modes of the arcjet...

Electronic Raman spectra in iron-based superconductors with two-orbital model

International Nuclear Information System (INIS)

Lu Hongyan; Wang Da; Chen San; Wang Wei; Gong Pifeng

2011-01-01

Electronic Raman spectra were calculated in orbital space in a microscopic theory. Both Raman spectra and spectra weight were presented. Raman spectra for the gap symmetries are different from each other. The results can help decide the gap symmetry by comparing with experiments. Electronic Raman spectra in iron-based superconductors with two-orbital model is discussed. In the orbital space, some possible pairing symmetries of the gap are selected. To further discriminate them, electronic Raman spectra and spectra weight at Fermi surface (FS) which helps understand the Raman spectra are calculated in each case. From the low energy threshold, the number of Raman peaks, and the low frequency power law behavior, we can judge whether it is full gap or nodal gap, and even one gap or multi-gaps. The results provide useful predictions for comparison with experiments.

Electron correlation effects in the (e,2e) valence separation energy spectra of krypton

International Nuclear Information System (INIS)

Fuss, I.; Glass, R.; McCarthy, I.E.; Minchinton, A.; Weigold, E.

1981-04-01

Separation energy spectra and momentum distributions for the valence orbitals of krypton have been obtained at a total electron energy of 1200eV using (e,2e) spectroscopy with symmetric kinematics. The spectroscopic strength of the 4s orbital is found to be significantly split among ion states ranging into the continuum, whereas the spectroscopic strength of the 4p ground state transition is found to be essentially unity. The momentum distributions for the 4p -1 and 4s -1 transitions are well described by the corresponding Hartree-Fock ground state orbital momentum distributions. A number of configuration interaction calculations using predominantly the 4s4p 6 and 4s 2 4p 4 4d ( 2 Ssub(1/2)) configurations, have been carried out for the main 4s - 1 ion eigenstates. The results, although confirming severe splitting of the 4s -1 spectroscopic strength, over-estimate the 4s4p 6 component of the lowest 2 S level in the ion. The data provides a sensitive test of the variational determination of the parameters of pseudostates representing configurations not treated explicitly

Measurement of neutron spectra for photonuclear reaction with linearly polarized photons

Directory of Open Access Journals (Sweden)

Kirihara Yoichi

2017-01-01

Full Text Available Spectra of neutrons produced by a photonuclear reaction from a 197Au target were measured using 16.95 MeV linearly and circularly polarized photon beams at NewSUBARU-BL01 using a time-of-flight method. The difference in the neutron spectra between the cases of a linearly and circularly polarized photon was measured. The difference in the neutron yield increased with the neutron energy and was approximately threefold at the maximum neutron energy. In a direction perpendicular to that of the linear polarization, the neutron yields decreased as the neutron energy increased.

Spectra of elementary excitations of fullerenes C60 and electron irradiation effect

International Nuclear Information System (INIS)

Gordeev, Yu.S.; Mikushkin, V.M.; Shnitov, V.V.

2000-01-01

The electron-stimulated changes in the spectra of the fullerenes C 60 elementary excitations are determined. They are manifested in decreasing the π-plasmon energy, the forbidden zone width, the HOMO-LUMO transition energy and also in smoothing the corresponding peculiarities of the spectra. The observed red shifts are connected with collectivization of the part of the π-electrons, formation of chemically-bound neighbouring molecules (polymerization) and with the corresponding increase in the part of the sp 3 -hybridized electrons. The spectra of the characteristic energy losses of the fullerene electrons, unperturbed by the polymerization process, are measured. The multipole structure of the (σ + π) plasmon and the exciton peculiarity, which manifests high sensitivity to the electron impact and may be used for the fullerene initial structure characterization, is identified [ru

ANA - a program for evaluation of gamma spectra from environmental samples

International Nuclear Information System (INIS)

Mishev, P.

1993-01-01

The program aims at for evaluation of gamma spectra, collected in different multichannel analyzers. It provides file format conversion from most popular file spectra formats. The program includes: spectra visualization; energy and shape calibration; efficiency calibration; automatic peak search; resolving of multiplets and peak calculations, based on program KATOK; isotope library; isotope identification and activity calculations. Three types of efficiency calibrations are possible: spline approximation; two branches logarithmic approximation; and polynomial approximation based on orthonormal polynomials. The suggestions of the International Atomic Energy Agency were taken into account in development of the algorithms. The program allows batch spectra processing appropriate for routine tasks and user controlled evaluations. Calculations of lower detection limits of some user defined isotopes are also possible. The program calculates precisely the statistical uncertainties of the final results. The error sources taken into account are: standard source activity errors, efficiency approximation errors and current measurement errors. (author)

Measurement of thermal neutron spectra using LINAC in Japan Atomic Energy Research Institute (JAERI)

International Nuclear Information System (INIS)

Akino, Fujiyoshi

1982-01-01

The exact grasp of thermal neutron spectra in a core region is very important for obtaining accurate thermal neutron group constants in the calculation for the nuclear design of a reactor core. For the accurate grasp of thermal neutron spectra, the capability of thermal neutron spectra to describe the moderator cross-sections for thermal neutron scattering is a key factor. Accordingly, 0 deg angular thermal neutron spectra were measured by the time of flight (TOF) method using the JAERI LINAC as a pulsed neutron source, for light water system added with Cd and In, high temperature graphite system added with boron, and light water-natural uranium heterogeneous multiplication system among the reactor moderators of light water or graphite systems. First, the equations to give the time of flight and neutron flux by TOF method were analyzed, and several corrections were investigated, such as those for detector efficiency, background, the transmission coefficient of air and the Al window of a flight tube, mean emission time of neutrons, and the distortion effect of re-entrant hole on thermal neutron spectra. Then, the experimental system, results and calculation were reported for the experiments on the above three moderator systems. Finally, the measurement of fast neutron spectra in natural uranium system and that of the efficiency of a 6 Li glass scintillator detector are described. (Wakatsuki, Y.)

NaI(Tl) electron energy resolution

CERN Document Server

Mengesha, W

2002-01-01

NaI(Tl) electron energy resolution eta sub e was measured using the Modified Compton Coincidence Technique (MCCT). The MCCT allowed detection of nearly monoenergetic internal electrons resulting from the scattering of incident 662 keV gamma rays within a primary NaI(Tl) detector. Scattered gamma rays were detected using a secondary HPGe detector in a coincidence mode. Measurements were carried out for electron energies ranging from 16 to 438 keV, by varying the scattering angle. Measured HPGe coincidence spectra were deconvolved to determine the scattered energy spectra from the NaI(Tl) detector. Subsequently, the NaI(Tl) electron energy spectra were determined by subtracting the energy of scattered spectra from the incident source energy (662 keV). Using chi-squared minimization, iterative deconvolution of the internal electron energy spectra from the measured NaI(Tl) spectra was then used to determine eta sub e at the electron energy of interest. eta sub e values determined using this technique represent va...

Classical Trajectories and Quantum Spectra

Science.gov (United States)

Mielnik, Bogdan; Reyes, Marco A.

1996-01-01

A classical model of the Schrodinger's wave packet is considered. The problem of finding the energy levels corresponds to a classical manipulation game. It leads to an approximate but non-perturbative method of finding the eigenvalues, exploring the bifurcations of classical trajectories. The role of squeezing turns out decisive in the generation of the discrete spectra.

Comparison of (alpha, n) thick-target neutron yields and spectra from ORIGEN-S and SOURCES

International Nuclear Information System (INIS)

Brown, T.H.; Wilson, W.B.; Perry, R.T.; Charlton, W.S.

1998-01-01

Both ORIGEN-S and SOURCES generate thick-target neutron yields and energy spectra from (α,n) reactions in homogeneous materials. SOURCES calculates yield and spectra for any material containing α-emitting and (α,n) target elements by simulating reaction physics, using α-emission energy spectra, elemental stopping cross sections, (α,n) cross sections for target nuclei, and branching fractions to produce-nuclide energy levels. This methodology results in accurate yield and spectra. ORIGEN-S has two options for calculating yields and spectra. The UO 2 option (default) estimates yields and spectra assuming the input α-emitters to be infinitely dilute in UO 2 . The borosilicate-glass option estimates yields from the total input material composition and generates spectra purportedly representative of spectra generated by 238 Pu, 241 Am, 242 Cm, and 244 Cm infinitely dilute in borosilicate glass, even if none of these four α-emitters are present in the input material composition. Because yields from the borosilicate-glass option in ORIGEN-S are based on entire input material composition and are reasonably accurate, the same is often assumed to be true for spectra. The input/output functionality of the borosilicate-glass option, along with ambiguity in ORIGEN-S documentation, gives the incorrect impression that spectra representative of input compositions are generated. This impression is reinforced by wide usage of the SCALE code system and its ORIGEN-S module and their sponsorship by the US Nuclear Regulatory Commission

A measurement of the absolute energy spectra of galactic cosmic rays during the 1976-77 solar minimum

Science.gov (United States)

Derrickson, J. H.; Parnell, T. A.; Austin, R. W.; Selig, W. J.; Gregory, J. C.

An instrument designed to measure elemental cosmic ray abundances from boron to nickel in the energy region 0.5-2.0 GeV/nucl was flown on a high altitude balloon from Sioux Falls, South Dakota, on 30 September through 1 October 1976 at an average atmospheric depth of about 5 g/sq cm. Differential energy spectra of B, C, N, O, Ne, Mg, Si and Fe, extrapolated to the top of the atmosphere, were measured. The float altitude exposure of 17 h ended near Alpena, Michigan. The flight trajectory maintained a north easterly heading out of Sioux Falls traversing the upper midwest region between 84 and 97 deg west longitude while remaining between 43.5 and 45 deg north latitude. The maximum vertical cut-off for this flight path was 1.77 GV or 0.35 GeV/nucl.

Analysis of high-frequency energy in long-term average spectra of singing, speech, and voiceless fricatives.

Science.gov (United States)

Monson, Brian B; Lotto, Andrew J; Story, Brad H

2012-09-01

The human singing and speech spectrum includes energy above 5 kHz. To begin an in-depth exploration of this high-frequency energy (HFE), a database of anechoic high-fidelity recordings of singers and talkers was created and analyzed. Third-octave band analysis from the long-term average spectra showed that production level (soft vs normal vs loud), production mode (singing vs speech), and phoneme (for voiceless fricatives) all significantly affected HFE characteristics. Specifically, increased production level caused an increase in absolute HFE level, but a decrease in relative HFE level. Singing exhibited higher levels of HFE than speech in the soft and normal conditions, but not in the loud condition. Third-octave band levels distinguished phoneme class of voiceless fricatives. Female HFE levels were significantly greater than male levels only above 11 kHz. This information is pertinent to various areas of acoustics, including vocal tract modeling, voice synthesis, augmentative hearing technology (hearing aids and cochlear implants), and training/therapy for singing and speech.

Power-law to Power-law Mapping of Blazar Spectra from Intergalactic Absorption

International Nuclear Information System (INIS)

Stecker, F W; Scully, S T

2007-01-01

We have derived a useful analytic approximation for determining the effect of intergalactic absorption on the γ-ray spectra of TeV blazars the energy range 0.2 TeV γ γ ) is approximately logarithmic. The effect of this energy dependence is to steepen intrinsic source spectra such that a source with an approximate power-law spectral index Γ s is converted to one with an observed spectral index Γ o ≅ Γ s + ΔΓ(z) where ΔΓ(z) is a linear function of z in the redshift range 0.05-0.4. We apply this approximation to the spectra of 7 TeV blazars

Diversity of soft X-ray spectra in quasars

International Nuclear Information System (INIS)

Elvis, M.; Wilkes, B.J.; Tananbaum, H.

1985-01-01

Soft X-ray spectra for three quasars obtained with the Einstein Imaging Proportional Counter covering the 0.1-4.0 keV band are reported. Power-law fits to these spectra have best-fit energy indices of 1.2 +0.6 or -0.2, for the quasar NAB 0205 + 024, 0.6 +0.3 or -0.2 for the quasar B2 1028 + 313, and 2.2 + or -0.4 for the quasar PG 1211 + 143. None of the quasars shows any evidence for a column density of cold matter in excess of the galactic values. The derived spectra demonstrate that there is no single universal power law slope for quasar X-ray spectra. The implications of these results for the X-ray background, X-ray continuum emission mechanisms, and the production of the optical/UV emission lines are briefly discussed. 46 references

A new compact solid-state neutral particle analyser at ASDEX Upgrade: Setup and physics modeling

Energy Technology Data Exchange (ETDEWEB)

Schneider, P. A.; Blank, H.; Geiger, B.; Mank, K.; Martinov, S.; Ryter, F.; Weiland, M.; Weller, A. [Max-Planck-Institut für Plasmaphysik, Garching (Germany)

2015-07-15

At ASDEX Upgrade (AUG), a new compact solid-state detector has been installed to measure the energy spectrum of fast neutrals based on the principle described by Shinohara et al. [Rev. Sci. Instrum. 75, 3640 (2004)]. The diagnostic relies on the usual charge exchange of supra-thermal fast-ions with neutrals in the plasma. Therefore, the measured energy spectra directly correspond to those of confined fast-ions with a pitch angle defined by the line of sight of the detector. Experiments in AUG showed the good signal to noise characteristics of the detector. It is energy calibrated and can measure energies of 40-200 keV with count rates of up to 140 kcps. The detector has an active view on one of the heating beams. The heating beam increases the neutral density locally; thereby, information about the central fast-ion velocity distribution is obtained. The measured fluxes are modeled with a newly developed module for the 3D Monte Carlo code F90FIDASIM [Geiger et al., Plasma Phys. Controlled Fusion 53, 65010 (2011)]. The modeling allows to distinguish between the active (beam) and passive contributions to the signal. Thereby, the birth profile of the measured fast neutrals can be reconstructed. This model reproduces the measured energy spectra with good accuracy when the passive contribution is taken into account.

Neutron Energy Spectra and Yields from the 7Li(p,n) Reaction for Nuclear Astrophysics

Science.gov (United States)

Tessler, M.; Friedman, M.; Schmidt, S.; Shor, A.; Berkovits, D.; Cohen, D.; Feinberg, G.; Fiebiger, S.; Krása, A.; Paul, M.; Plag, R.; Plompen, A.; Reifarth, R.

2016-01-01

Neutrons produced by the 7Li(p, n)7Be reaction close to threshold are widely used to measure the cross section of s-process nucleosynthesis reactions. While experiments have been performed so far with Van de Graaff accelerators, the use of RF accelerators with higher intensities is planned to enable investigations on radioactive isotopes. In parallel, high-power Li targets for the production of high-intensity neutrons at stellar energies are developed at Goethe University (Frankfurt, Germany) and SARAF (Soreq NRC, Israel). However, such setups pose severe challenges for the measurement of the proton beam intensity or the neutron fluence. In order to develop appropriate methods, we studied in detail the neutron energy distribution and intensity produced by the thick-target 7Li(p,n)7Be reaction and compared them to state-of- the-art simulation codes. Measurements were performed with the bunched and chopped proton beam at the Van de Graaff facility of the Institute for Reference Materials and Measurements (IRMM) using the time-of-flight (TOF) technique with thin (1/8") and thick (1") detectors. The importance of detailed simulations of the detector structure and geometry for the conversion of TOF to a neutron energy is stressed. The measured neutron spectra are consistent with those previously reported and agree well with Monte Carlo simulations that include experimentally determined 7Li(p,n) cross sections, two-body kinematics and proton energy loss in the Li-target.

Cross sections and differential spectra for reactions of 2-20 MeV neutrons on /sup nat/Cr

International Nuclear Information System (INIS)

Blann, M.; Komoto, T.T.

1988-01-01

This report summarizes product yields, secondary n,p and α spectra, and γ-ray spectra calculated for incident neutrons of 2 to 20 MeV on /sup nat/Cr targets. Results are all from the code ALICE, using the version ALISO which does weighting of results for targets which are a mix of isotopes. Where natural isotopic targets are involved, yields and n,p,α spectra will be reported weighted over isotopic yields. Gamma-ray spectra, however, will be reported for the most abundant isotope. We present product yields versus incident neutron energy, n,p,α spectra versus incident neutron energy, and calculated γ-ray spectra

Finite temperature effects on the X-ray absorption spectra of energy related materials

Science.gov (United States)

Pascal, Tod; Prendergast, David

2014-03-01

We elucidate the role of room-temperature-induced instantaneous structural distortions in the Li K-edge X-ray absorption spectra (XAS) of crystalline LiF, Li2SO4, Li2O, Li3N and Li2CO3 using high resolution X-ray Raman spectroscopy (XRS) measurements and first-principles density functional theory calculations within the eXcited electron and Core Hole (XCH) approach. Based on thermodynamic sampling via ab-initio molecular dynamics (MD) simulations, we find calculated XAS in much better agreement with experiment than those computed using the rigid crystal structure alone. We show that local instantaneous distortion of the atomic lattice perturbs the symmetry of the Li 1 s core-excited-state electronic structure, broadening spectral line-shapes and, in some cases, producing additional spectral features. This work was conducted within the Batteries for Advanced Transportation Technologies (BATT) Program, supported by the U.S. Department of Energy Vehicle Technologies Program under Contract No. DE-AC02-05CH11231.

X-ray absorption spectra and emission spectra of plasmas

International Nuclear Information System (INIS)

Peng Yonglun; Yang Li; Wang Minsheng; Li Jiaming

2002-01-01

The author reports a theoretical method to calculate the resolved absorption spectra and emission spectra (optically thin) of hot dense plasmas. Due to its fully relativistic treatment incorporated with the quantum defect theory, it calculates the absorption spectra and emission spectra for single element or multi-element plasmas with little computational efforts. The calculated absorption spectra of LTE gold plasmas agree well with the experimental ones. It also calculates the optical thin emission spectra of LTE gold plasmas, which is helpful to diagnose the plasmas of relevant ICF plasmas. It can also provide the relevant parameters such as population density of various ionic stages, precise radiative properties for ICF studies

Funny hills in pion spectra from heavy-ion collisions

International Nuclear Information System (INIS)

Rasmussen, J.O.

1982-03-01

A discussion of some of the systematic features of the pion spectra in heavy-ions reactions is given. A discussion of the hills and valleys in heavy ion pion spectra that show up at the lower pion energies is given. The following topics are discussed: (1) three kinds of funny hills; (2) π - / + ratios near center of mass; (3) new Monte Carlo studies of charged pion spectra; and (4) pion orbiting about fireballs and Bose-Einstein behavior as explanation for the mid-rapidity P/sub perpendicular to/ approx. = 0.4 to 0.5 m/sub π/c hill

Investigation of IR absorption spectra of oral cavity bacteria

Science.gov (United States)

Belikov, Andrei V.; Altshuler, Gregory B.; Moroz, Boris T.; Pavlovskaya, Irina V.

1996-12-01

The results of comparative investigation for IR and visual absorption spectra of oral cavity bacteria are represented by this paper. There are also shown the main differences in absorption spectra of such pure bacteria cultures as : E- coli, Candida, Staph, Epidermidis, and absorption spectra of bacteria colonies cultured in tooth root canals suspected to harbour several endodontical problems. The results of experimental research targeted to investigate an effect of such combined YAG:Nd and YAG:Cr; Tm; Ho laser parameters like: wavelength, energy density, average power and etc., to oral cavity bacteria deactivation are given finally.

Vibrationally resolved photoelectron spectra of lower diamondoids: A time-dependent approach

Science.gov (United States)

Xiong, Tao; Włodarczyk, Radosław; Gallandi, Lukas; Körzdörfer, Thomas; Saalfrank, Peter

2018-01-01

Vibrationally resolved lowest-energy bands of the photoelectron spectra (PES) of adamantane, diamantane, and urotropine were simulated by a time-dependent correlation function approach within the harmonic approximation. Geometries and normal modes for neutral and cationic molecules were obtained from B3LYP hybrid density functional theory (DFT). It is shown that the simulated spectra reproduce the experimentally observed vibrational finestructure (or its absence) quite well. Origins of the finestructure are discussed and related to recurrences of autocorrelation functions and dominant vibrations. Remaining quantitative and qualitative errors of the DFT-derived PES spectra refer to (i) an overall redshift by ˜0.5 eV and (ii) the absence of satellites in the high-energy region of the spectra. The former error is shown to be due to the neglect of many-body corrections to ordinary Kohn-Sham methods, while the latter has been argued to be due to electron-nuclear couplings beyond the Born-Oppenheimer approximation [Gali et al., Nat. Commun. 7, 11327 (2016)].

Tunneling spectra of graphene on copper unraveled

DEFF Research Database (Denmark)

Zhang, Xin; Stradi, Daniele; Liu, Lei

2016-01-01

mechanisms, etc. The interpretation of the spectra can be complicated, however. Specifically for graphene grown on copper, there have been conflicting reports of tunneling spectra. A clear understanding of the mechanisms behind the variability is desired. In this work, we have revealed that the root cause...... of the variability in tunneling spectra is the variation in graphene-substrate coupling under various experimental conditions, providing a salutary perspective on the important role of 2D material-substrate interactions. The conclusions are drawn from measured data and theoretical calculations for monolayer, AB......-stacked bilayer, and twisted bilayer graphene coexisting on the same substrates in areas with and without intercalated oxygen, demonstrating a high degree of consistency. The Van Hove singularities of the twisted graphene unambiguously indicate the Dirac energy between them, lending strong evidence to our...

Core Level Spectra of Organic Molecules Adsorbed on Graphene

Directory of Open Access Journals (Sweden)

Abhilash Ravikumar

2018-03-01

Full Text Available We perform first principle calculations based on density functional theory to investigate the effect of the adsorption of core-excited organic molecules on graphene. We simulate Near Edge X-ray absorption Fine Structure (NEXAFS and X-ray Photoemission Spectroscopy (XPS at the N and C edges for two moieties: pyridine and the pyridine radical on graphene, which exemplify two different adsorption characters. The modifications of molecular and graphene energy levels due to their interplay with the core-level excitation are discussed. We find that upon physisorption of pyridine, the binding energies of graphene close to the adsorption site reduce mildly, and the NEXAFS spectra of the molecule and graphene resemble those of gas phase pyridine and pristine graphene, respectively. However, the chemisorption of the pyridine radical is found to significantly alter these core excited spectra. The C 1s binding energy of the C atom of graphene participating in chemisorption increases by ∼1 eV, and the C atoms of graphene alternate to the adsorption site show a reduction in the binding energy. Analogously, these C atoms also show strong modifications in the NEXAFS spectra. The NEXAFS spectrum of the chemisorbed molecule is also modified as a result of hybridization with and screening by graphene. We eventually explore the electronic properties and magnetism of the system as a core-level excitation is adiabatically switched on.

Measurement of spectra for intra-oral X-ray beams using biological materials as attenuator

International Nuclear Information System (INIS)

Zenóbio, Madelon A.F.; Nogueira-Tavares, Maria S.; Zenóbio, Elton G.; Squair, Peterson Lima; Santos, Marcus A.P.; Silva, Teógenes A. da

2011-01-01

In diagnostic radiology, the radiation interaction probability in matter is a strong function of the X-ray energy. The knowledge of the X-ray energy spectral distribution allows optimizing the radiographic imaging system in order to obtain high quality images with as low as reasonably achievable patient doses. In this study, transmitted X-ray spectra through dentin and enamel that are existing materials in intra-oral radiology were experimentally determined in an X-ray equipment with 40–70 kV variable range. Dentin and enamel samples with 0.4–3.8 and 0.6–2.6 mm thick were used as attenuators. X-ray transmitted spectra were measured with XR-100T model CdTe detector and half-value layers (HVL) were determined. Characteristics of both dentin and enamel transmitted spectra showed that they have differences in the penetration power in matter and in the spectrum distribution. The results will be useful for phantom developments based on dentin and enamel for image quality control in dental radiology. - Highlights: ► The X-ray energy spectral distribution, optimize the radiographic imaging system. Transmitted X-ray spectra through dentin and enamel were experimentally determined. X-ray transmitted spectra were measured (XR-100T model CdTe detector). The transmitted spectra showed differences in the penetration power and spectrum distribution. Dentin and enamel transmitted spectra will be useful for phantom developments.

Kβ spectra of heliumlike chromium from an electron-beam ion trap

International Nuclear Information System (INIS)

Decaux, V.; Beiersdorfer, P.; Elliott, S.; Osterheld, A.

1993-01-01

Kβ spectra of heliumlike chromium have been recorded using the Livermore electron-beam ion trap (EBIT) with a high-resolution Bragg crystal spectrometer in the von Hamos configuration, in the wavelong range from 1.870 Angstrom. Measurements have been made both for direct excitation at an electron beam energy of 8 k and dielectronic recombination around the KLM resonance energy of 5 keV. In order to evaluate the resonance strength the lithiumlike dielectronic satellites, we used a data routine technique to accumulate spectra at 15 different beam energies between 4.96 and 5.28 keV. Results are compared to theoretical calculations using the multiconfiguration parametric potential method

Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

Science.gov (United States)

Wadiasingh, Zorawar; Baring, Matthew G.; Gonthier, Peter L.; Harding, Alice K.

2018-02-01

Hard, nonthermal, persistent pulsed X-ray emission extending between 10 and ∼150 keV has been observed in nearly 10 magnetars. For inner-magnetospheric models of such emission, resonant inverse Compton scattering of soft thermal photons by ultrarelativistic charges is the most efficient production mechanism. We present angle-dependent upscattering spectra and pulsed intensity maps for uncooled, relativistic electrons injected in inner regions of magnetar magnetospheres, calculated using collisional integrals over field loops. Our computations employ a new formulation of the QED Compton scattering cross section in strong magnetic fields that is physically correct for treating important spin-dependent effects in the cyclotron resonance, thereby producing correct photon spectra. The spectral cutoff energies are sensitive to the choices of observer viewing geometry, electron Lorentz factor, and scattering kinematics. We find that electrons with energies ≲15 MeV will emit most of their radiation below 250 keV, consistent with inferred turnovers for magnetar hard X-ray tails. More energetic electrons still emit mostly below 1 MeV, except for viewing perspectives sampling field-line tangents. Pulse profiles may be singly or doubly peaked dependent on viewing geometry, emission locale, and observed energy band. Magnetic pair production and photon splitting will attenuate spectra to hard X-ray energies, suppressing signals in the Fermi-LAT band. The resonant Compton spectra are strongly polarized, suggesting that hard X-ray polarimetry instruments such as X-Calibur, or a future Compton telescope, can prove central to constraining model geometry and physics.

The MeV spectra of gamma-ray bursts measured with COMPTEL

International Nuclear Information System (INIS)

Hoover, A.S.; Kippen, R.M.; McConnell, M.L.

2005-01-01

The past decade has produced a wealth of observational data on the energy spectra of prompt emission from gamma-ray bursts. Most of the data cover the energy range from a few to several hundred KeV. One set of higher energy observations comes from the Imaging Compton Telescope COMPTEL on the Compton Observatory, which measured in the energy range from 0.75 to 30 MeV. We analyzed the full 9.2 years COMPTEL data to reveal the significant detection of 44 gamma-ray bursts. We present preliminary results obtained in the process of preparing a final catalog of the spectral analysis of these events. In addiction, we compare the COMPTEL spectra to simultaneous BATSE measurements for purposes of cross-calibration

Spatial structure of kinetic energy spectra in LES simulations of flow in an offshore wind farm

Science.gov (United States)

Fruh, Wolf-Gerrit; Creech, Angus

2017-04-01

The evolution of wind turbine and wind farm wakes was investigated numerically for the case of Lillgrund wind farm consisting of a tightly packed array of 48 turbines. The simulations for a number of wind directions at a free wind speed of just under the rated wind speed in a neutrally stable atmosphere were carried out using Large-Eddy Simulations with the adaptive Finite-Element CFD solver Fluidity. The results were interpolated from the irregularly spaced mesh nodes onto a regular grid with comparable spatial resolution at horizontal slices at various heights. To investigate the development of the wake as the flow evolves through the array, spectra of the kinetic energy in sections perpendicular to the wind directions within the wake and to the sides of the array were calculated. This paper will present the key features and spectral slopes of the flow as a function of downstream distance from the front turbine through and beyond the array. The main focus will be on the modification of the spectra as the flow crosses a row of turbines followed by its decay in the run-up to the next row, but we will also present to wake decay of the wind farm wake downstream of the array.

Long-term MST radar observations of vertical wave number spectra of gravity waves in the tropical troposphere over Gadanki (13.5° N, 79.2° E: comparison with model spectra

Directory of Open Access Journals (Sweden)

S. Vijaya Bhaskara Rao

2008-06-01

Full Text Available The potential utility of Mesosphere-Stratosphere-Troposphere (MST radar measurements of zonal, meridional and vertical winds for divulging the gravity wave vertical wave number spectra is discussed. The data collected during the years 1995–2004 are used to obtain the mean vertical wave number spectra of gravity wave kinetic energy in the tropical troposphere over Gadanki (13.5° N, 79.2° E. First, the climatology of 3-dimensional wind components is developed using ten years of radar observations, for the first time, over this latitude. This climatology brought out the salient features of background tropospheric winds over Gadanki. Further, using the second order polynomial fit as background, the day-to-day wind anomalies are estimated. These wind anomalies in the 4–14 km height regions are used to estimate the profiles of zonal, meridional and vertical kinetic energy per unit mass, which are then used to estimate the height profile of total kinetic energy. Finally, the height profiles of total kinetic energy are subjected to Fourier analysis to obtain the monthly mean vertical wave number spectra of gravity wave kinetic energy. The monthly mean vertical wave number spectra are then compared with a saturation spectrum predicted by gravity wave saturation theory. A slope of 5/3 is used for the model gravity wave spectrum estimation. In general, the agreement is good during all the months. However, it is noticed that the model spectrum overestimates the PSD at lower vertical wave numbers and underestimates it at higher vertical wave numbers, which is consistently observed during all the months. The observed discrepancies are attributed to the differences in the slopes of theoretical and observed gravity wave spectra. The slopes of the observed vertical wave number spectra are estimated and compared with the model spectrum slope, which are in good agreement. The estimated slopes of the observed monthly vertical wave number spectra are in the

Prompt fission neutron spectra of n + 235U above the (n, nf) fission threshold

International Nuclear Information System (INIS)

Shu Nengchuan; Chen Yongjing; Liu Tingjin; Jia Min

2015-01-01

Calculations of prompt fission neutron spectra (PFNS) from the 235 U(n, f) reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n, xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n, xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n, nf) or (n, 2nf) reactions influences the PFNS shape, and the neutron spectra of the (n, xnf) fission-channel are soft compared with the neutron spectra of the (n, f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case. (authors)

Analysis of the neutron energy spectra from the sup(208)Pb (p,n) sup(208)Bi reaction at Esub(p)=200 MeV

International Nuclear Information System (INIS)

Ershov, S.N.; Fayans, S.A.; Gareev, F.A.; Pyatov, N.I.

1986-01-01

Microscopic calculation of the small-angle neutron energy spectra from the 208 Pb (p, n) 208 Bi reaction at Esub(p)=200 MeV are presented. It is shown that the distorted-wave impulse approximation and the microscopic theory of finite Fermi systems can be employed for describing the low-energy excitation region 0 <= Q <= 30 MeV with small momentum transfers. A quantitative estimate is obtained for the local charge of quasiparticles esub(q)[σtau]=0.8 that characterizes the quenching of the integral strength of spin-flip low-energy transitions and the relevant effects are discussed

Spallation Neutron Emission Spectra in Some Amphoter Target Nuclei by Proton Beam Up to 140 MeV Energy

International Nuclear Information System (INIS)

Yildirim, G.

2008-01-01

In the present study, the (p,xn) reaction neutron-emission spectra for some amphoter target nuclei as 27 A l, 64 Z n, 120 S n, and 208 P b were investigated up to 140 MeV incident proton energy. The pre-equilibrium calculations were calculated by using the hybrid model, the geometry dependent hybrid model, the full exciton model and the cascade exciton model. The reaction equilibrium component was calculated with a traditional compound nucleus model developed by Weisskopf Ewing. Calculation results have been discussed and compared with the available experimental data in literature

3D spectrum imaging of multi-wall carbon nanotube coupled π-surface modes utilising electron energy-loss spectra acquired using a STEM/Enfina system

International Nuclear Information System (INIS)

Seepujak, A.; Bangert, U.; Gutierrez-Sosa, A.; Harvey, A.J.; Blank, V.D.; Kulnitskiy, B.A.; Batov, D.V.

2005-01-01

Numerous studies have utilised electron energy-loss (EEL) spectra acquired in the plasmon (2-10 eV) regime in order to probe delocalised π-electronic states of multi-wall carbon nanotubes (MWCNTs). Interpretation of electron energy loss (EEL) spectra of MWCNTs in the 2-10 eV regime. Carbon (accepted for publication); Blank et al. J. Appl. Phys. 91 (2002) 1657). In the present contribution, EEL spectra were acquired from a 2D raster defined on a bottle-shaped MWCNT, using a Gatan UHV Enfina system attached to a dedicated scanning transmission electron microscope (STEM). The technique utilised to isolate and sequentially filter each of the volume and surface resonances is described in detail. Utilising a scale for the intensity of a filtered mode enables one to 'see' the distribution of each resonance in the raster. This enables striking 3D resonance-filtered spectrum images (SIs) of π-collective modes to be observed. Red-shift of the lower energy split π-surface resonance provides explicit evidence of π-surface mode coupling predicted for thin graphitic films (Lucas et al. Phys. Rev. B 49 (1994) 2888). Resonance-filtered SIs are also compared to non-filtered SIs with suppressed surface contributions, acquired utilising a displaced collector aperture. The present filtering technique is seen to isolate surface contributions more effectively, and without the significant loss of statistics, associated with the displaced collector aperture mode. Isolation of collective modes utilising 3D resonance-filtered spectrum imaging, demonstrates a valuable method for 'pinpointing' the location of discrete modes in irregularly shaped nanostructures

A measurement of the absolute energy spectra of galactic cosmic rays during the 1976-77 solar minimum

International Nuclear Information System (INIS)

Derrickson, J.H.; Parnell, T.A.; Austin, R.W.; Selig, W.J.

1992-01-01

An instrument designed to measure elemental cosmic ray abundances from boron to nickel in the energy region 0.5-2.0 GeV nucl -1 was flown on a high altitude balloon from Sioux Falls, South Dakota, on 30 September through 1 October 1976 at an average atmospheric depth of ∼5 g cm -2 . Differential energy spectra of B, C, N, O, Ne, Mg, Si and Fe, extrapolated to the top of the atmosphere, were measured. The float altitude exposure of 17 h ended near Alpena, Michigan. The flight trajectory maintained a north easterly heading out of Sioux Falls traversing the upper mid-west region between 84 o and 97 o west longitude while remaining between 43.5 o and 45 o north latitude. The maximum vertical cut-off for this flight path was 1.77 GV or 0.35 GeV nucl -1 . (author)