Incoherent Scattering Cross Sections Research Articles

Cross sections of neutral-current neutrino scattering on 98,100Mo isotopes

Coherent elastic neutrino–nucleus scattering (CEνNS) is a neutral-current low-energy electro-weak reaction-channel detected recently by the COHERENT experiment at the Oak Ridge National Laboratory (ORNL), USA, in the Spallation Neutron Source facility. The extremely weak signal on the CsI detector of the first experiment and on the liquid Ar of the repeated COHERENT experiment is the energy-recoil due to the neutrino–nucleus interaction, where the nucleus is elastically scattered as a whole while simultaneously the neutrino goes out. Today, several promising nuclear detectors are on the way to be employed in designed and ongoing experiments. In our present work, we provide predictions for incoherent scattering cross sections of low-energy neutrinos on 98,100Mo isotopes obtained with the deformed shell model employed previously for similar predictions in other electroweak processes. We mention that, Mo detector medium has been used previously in the MOON and NEMO double beta decay experiments.

Coherent scattering cross sections of some rare earth compounds at small angles below [formula omitted] for 59.54 keV gamma rays

The angle integrated total scattering cross sections of some rare earth oxides were determined experimentally for 59.54 keV gamma rays in the angular ranges of 0–4°, 0–6°, 0–8°and 0–10°. From the experimental total scattering cross sections, the corresponding angle integrated incoherent scattering cross sections obtained from ENDF library (based on the nonrelativistic Hartree–Fock form factor method) was subtracted to obtain the angle integrated coherent scattering cross sections. The angle integrated coherent scattering cross sections show good agreement with that determined from ENDF data. The effective atomic numbers of the selected rare earth oxides were extracted by applying the ratio of cross section method. The variation of angle integrated coherent scattering cross section with the effective atomic number of the selected compounds have been studied.

The Impulse Approximation Scattering Function and Its Use in Monte Carlo Photon Transport Simulations

The viability of using the impulse approximation scattering function in Monte Carlo photon transport simulations is explored. This scattering function can be constructed from the double differential incoherent scattering cross section developed by Ribberfors and Berggren [Phys. Rev. A., Vol 26, p. 3325 (1982)]. A commonly used method for modeling photon Doppler broadening, which is referred to as the hybrid Doppler broadening method, can also be derived from this cross section. A new photon Doppler broadening method, called the consistent Doppler broadening method, is derived and discussed. This method eliminates some of the commonly employed approximations in the hybrid Doppler broadening method, in part, by using the impulse approximation scattering function. Integrated incoherent cross sections generated using the impulse approximation scattering function and the widely used Waller-Hartree scattering function are in good agreement above 20 keV. Below 20 keV, differences as high as 70% are observed, which differs from the roughly 5% differences observed by Ribberfors [Phys. Rev. A., Vol. 27, p. 3061 (1983)] for some of the materials. Integral and spectral quantities for two problems are also generated using the Monte Carlo photon transport capabilities of the Framework for Research in Nuclear Science and Engineering. Due to the small, relative result differences observed when using the impulse approximation scattering function, it is considered a viable alternative to the Waller-Hartree scattering function. In addition, some small, but expected, differences in spectral fluxes at low energies can be avoided by adopting the consistent Doppler broadening method.

Low-background neutron reflectometry from solid/liquid interfaces

Liquid cells are an increasingly common sample environment for neutron reflectometry experiments and are critical for measuring the properties of materials at solid/liquid interfaces. Background scattering determines the maximum useful scattering vector, and hence the spatial resolution, of the neutron reflectometry measurement. The primary sources of background are the liquid in the cell reservoir and the materials forming the liquid cell itself. Thus, characterization and mitigation of these background sources are necessary for improvements in the signal-to-background ratio and resolution of neutron reflectometry measurements employing liquid cells. Single-crystal silicon is a common material used for liquid cells due to its low incoherent scattering cross section for neutrons, and the path lengths of the neutron beam through silicon can be several centimetres in modern cell designs. Here, a liquid cell is constructed with a sub-50 µm thick liquid reservoir encased in single-crystal silicon. It is shown that, at high scattering vectors, inelastic scattering from silicon represents a significant portion of the scattering background and is, moreover, structured, confounding efforts to correct for it by established background subtraction techniques. A significant improvement in the measurement quality is achieved using energy-analyzed detection. Energy-analyzed detection reduces the scattering background from silicon by nearly an order of magnitude, and from fluids such as air and liquids by smaller but significant factors. Combining thin liquid reservoirs with energy-analyzed detection and the high flux of the CANDOR polychromatic reflectometer at the NIST Center for Neutron Research, a background-subtracted neutron reflectivity smaller than 10−8 from a liquid cell sample is reported.

Polarization analysis for small-angle neutron scattering with a 3He spin filter at a pulsed neutron source

Neutron polarization analysis (NPA) for small-angle neutron scattering (SANS) experiments using a pulsed neutron source was successfully achieved by applying a 3He spin filter as a spin analyzer for the neutrons scattered from the sample. The cell of the 3He spin filter gives a weak small-angle scattering intensity (background) and covers a sufficient solid angle for performing SANS experiments. The relaxation time of the 3He polarization is sufficient for continuous use for approximately 2 days, thus reaching the typical duration required for a complete set of SANS experiments. Although accurate evaluation of the incoherent neutron scattering, which is predominantly attributable to the extremely large incoherent scattering cross section of hydrogen atoms in samples, is difficult using calculations based on the sample elemental composition, the developed NPA approach with consideration of the influence of multiple neutron scattering enabled reliable decomposition of the SANS intensity distribution into the coherent and incoherent scattering components. To date, NPA has not been well established as a standard technique for SANS experiments at pulsed neutron sources such as the Japan Proton Accelerator Research Complex (J-PARC) and the US Spallation Neutron Source. It is anticipated that this work will contribute significantly to the accurate determination of the coherent neutron scattering component for scatterers in various types of organic sample systems in SANS experiments at J-PARC, particularly for systems involving competition between the coherent and incoherent scattering intensity.

Fabrication of nanodiamond-dispersed composite holographic gratings and their light and slow-neutron diffraction properties

We demonstrate the use of nanodiamond in constructing holographic nanoparticle-polymer composite transmission gratings with large saturated refractive index modulation amplitudes at both optical and slow-neutron wavelengths, resulting in efficient control of light and slow-neutron beams. Nanodiamond possesses a high refractive index at optical wavelengths and large coherent and small incoherent scattering cross sections with low absorption at slow-neutron wavelengths. We describe the synthesis of nanodiamond, the preparation of photopolymerizable nanodiamond-polymer composite films, the construction of transmission gratings in nanodiamond-polymer composite films and light optical diffraction experiments. Results of slow-neutron diffraction from such gratings are also presented.

Pocket formula for incoherent scattering cross section

We have achieved a simple empirical formula for incoherent scattering cross section based on the data available in the literature. The present formula produces incoherent scattering cross section values of all atoms for the atomic number range 1 < Z < 100 in the energy range 1 keV < E < 100 GeV with the simple inputs of atomic number (Z) and energy (E) in keV. The percentage of deviation of incoherent scattering cross section of the present formula is less than ±3%. The values produced by the present formula agree well with the experiments. The present formula is useful in the fields of radiation physics and nuclear physics.

ON COHERENT AND INCOHERENT SCATTERING OF FAST CHARGED PARTICLES IN ULTRATHIN CRYSTALS

We consider the fast charged particles scattering in ultrathin crystals on the base of the Born approximation of quantum electrodynamics. The main attention is paid to the question of the scattering cross section splitting into coherent and incoherent components when one of the crystallographic axes and planes is oriented along the direction of particle motion. It is shown that both the coherent and the incoherent components of the scattering cross section considerably depend on the orientation of the crystallographic axes relatively to the incident beam. In particular, it was shown that when particles are scattered by the crystal planes of atoms, the incoherent scattering cross section does not contain the Debye-Waller factor.

How can we derive hydration water dynamics with incoherent neutron scattering and molecular dynamics simulation?

Incoherent neutron scattering (INS) is one of the useful experimental methods for studying protein dynamics at the pico-nanosecond timescale. At this timescale, protein dynamics is highly coupled with hydration, which is observed as protein dynamical transition (PDT). INS is very sensitive to hydrogen atomic dynamics because of the large incoherent scattering cross section of hydrogen atom, and thus, the INS of a hydrated protein provides overall dynamic information about the protein, including hydration water. Separation of hydration water dynamics is essential for understanding hydration-related protein dynamics. H2O/D2O exchange is an effective method in the context of INS experiments for observing the dynamics of protein and hydration water separately. Neutron scattering is directly related to the van Hove space-time correlation function, which can be calculated quantitatively by performing molecular dynamics (MD) simulations. Diffusion and hydrogen bond dynamics of hydration water can be analyzed by performing MD simulation. MD simulation is useful for analyzing the dynamic coupling mechanism in hydration-related protein dynamics from the viewpoint of interpreting INS data because PDT is induced by hydration. In the present work, we demonstrate the methodological advantages of the H2O/D2O exchange technique in INS and the compatibility of INS and MD simulation as tools for studying protein dynamics and hydration water.

Simultaneous Neutron Radiography of Metal Nozzle Geometry and Near-Field Spray

Sprays are prominent in various aerospace propulsion systems, but in-nozzle and near-field flow characteristics are not fully understood. Therefore, various nonintrusive probes have been applied to the measurement of spray characteristics. Such probes include well-known X-ray techniques and, to some extent, less well-known neutron methods, which are particularly useful for the study of flows inside nozzles. Unlike X-rays, for which the penetration depth of heavy metals is limited, neutrons are able to penetrate deeply into some metals, including aluminum, lead, and steel. Neutron imaging also complements X-ray imaging in light element detection, especially hydrogen, due to the large incoherent scattering cross section (80 b, in which ) with hydrogen. Thus, for dense near-field sprays, which combine metal nozzles and hydrogen-based liquids (e.g., hydrocarbon fuels), it is advantageous to use neutrons rather than X-rays for imaging measurements. In this work, proof-of-principle in situ neutron radiography measurements of metal spray nozzles and water sprays were conducted. The neutron results were compared with optical shadowgraph images of the sprays, which showed a good agreement. Additionally, imaging of the nozzle interior geometry and water inside the nozzle was demonstrated, and it was shown that neutron radiography can produce quantitative liquid concentration by two-dimensional snapshot and three-dimensional tomography scans.

The photon interaction cross sections of human cortical bone tissue

The photon interaction cross sections of human cortical bone tissue are computerized differently from the literature by taking into account the effects of molecular interference and smaller values of the scattering angles. The molecular form factors and incoherent scattering functions were also calculated to obtain molecular coherent and incoherent scattering cross sections, respectively. The results are tabulated and compared with references values in literature. It is observed that the theoretical results are in agreement with experimental data.

Effect of component substitution on the atomic dynamics in glass-forming binary metallic melts

We investigate the substitution of early transition metals (Zr, Hf, and Nb) in Ni-based binary glass-forming metallic melts and the impact on structural and dynamical properties by using a combination of neutron scattering, electrostatic levitation (ESL), and isotopic substitution. The self-diffusion coefficients measured by quasielastic neutron scattering (QENS) identify a sluggish diffusion as well as an increased activation energy by almost a factor of 2 for Hf35Ni65 compared to Zr36Ni64. This finding can be explained by the locally higher packing density of Hf atoms in Hf35Ni65 compared to Zr atoms in Zr36Ni64, which has been derived from interatomic distances by analyzing the measured partial structure factors. Furthermore, QENS measurements of liquid Hf35Ni65 prepared with 60Ni, which has a vanishing incoherent scattering cross section, have demonstrated that self-diffusion of Hf is slowed down compared to the concentration weighted self-diffusion of Hf and Ni. This implies a dynamical decoupling between larger Hf and smaller Ni atoms, which can be related to a saturation effect of unequal atomic nearest-neighbor pairs, that was observed recently for Ni-rich compositions in Zr-Ni metallic melts. In order to establish a structure-dynamics relation, measured partial structure factors have been used as an input for mode-coupling theory (MCT) of the glass transition to calculate self-diffusion coefficients for the different atomic components. Remarkably,MCT can reproduce the increased activation energy for Hf35Ni65 as well as the dynamical decoupling between Hf and Ni atoms.

Poster ‐ 18: New features in EGSnrc for photon cross sections

Purpose:To implement two new features in the EGSnrc Monte Carlo system. The first is an option to account for photonuclear attenuation, which can contribute a few percent to the total cross section at the higher end of the energy range of interest to medical physics. The second is an option to use exact NIST XCOM photon cross sections.Methods:For the first feature, the photonuclear total cross sections are generated from the IAEA evaluated data. In the current, first‐order implementation, after a photonuclear event, there is no energy deposition or secondary particle generation. The implementation is validated against deterministic calculations and experimental measurements of transmission signals. For the second feature, before this work, if the user explicitly requested XCOM photon cross sections, EGSnrc still used its own internal incoherent scattering cross sections. These differ by up to 2% from XCOM data between 30 keV and 40 MeV. After this work, exact XCOM incoherent scattering cross sections are an available option. Minor interpolation artifacts in pair and triplet XCOM cross sections are also addressed. The default for photon cross section in EGSnrc is XCOM except for the new incoherent scattering cross sections, which have to be explicitly requested. The photonuclear, incoherent, pair and triplet data from this work are available for elements and compounds for photon energies from 1 keV to 100 GeV.Results:Both features are implemented and validated in EGSnrc.Conclusions: The two features are part of the standard EGSnrc distribution as of version 4.2.3.2.

Investigation of coherent to incoherent scattering cross section ratios of some foil metals depending on the temperature

In this study, it was aimed at examining the cross section ratios of coherent and incoherent scattering depending on the temperature for the elements Cd, In, Sn and Pb by 59.5 keV γ-rays from a 100 mCi 241Am radioisotope point source. The coherent and incoherent cross section of Cd, In, Sn and Pb have been measured by using a Si(Li) solid-state detector at temperature between 30-300 °C. Coherent to incoherent cross section ratios and FWHM (Full width at half maximum) of the elements have been calculated. Temperature-dependent changes of the parameters have been given in the graphical forms. Based on the results obtained, coherent to incoherent cross section ratios of the elements are dependent on the temperature. It is observed that coherent to incoherent cross section ratios of Cd, In, and Pb decrease with increasing temperature. For Sn, first of all coherent and incoherent intensity ratios decrease, then increase and decrease again respectively. To sum up, coherent to incoherent cross section ratios tend to decrease with increasing temperature.

Small angle scattering of 59.54 keV photons by elemental samples in the atomic number region 13 ≤ Z ≤ 82

In the present paper, we report the angle integrated coherent scattering cross sections of some elements at low momentum transfer over four angular ranges for some elements in the atomic number range 13≤Z≤82 for 241Am (59.54 keV) gamma rays. The coherent scattering cross sections were derived from the experimentally measured total (Coherent + incoherent) scattering cross sections for the elements at the energy of interest by subtracting separately the small contribution of the corresponding angle integrated incoherent scattering cross sections. The theoretical angle integrated incoherent scattering cross sections were computed by numerically integrating the values provided in the compilations based on the non-relativistic Hartree-Fock (NRHF) model and the modified form factor (MFF) model for the charge distribution within the atom. The present values of the angle integrated coherent scattering cross sections of the elements Al, Fe, Cu, Zn, Cd, Sn and Pb at 59.54 keV in the angular ranges of (0∘−4∘), (0∘−6∘), (0∘−8∘) and (0°–10°) so obtained are compared with the corresponding theoretical S-matrix data within the range of experimental errors. The root mean square error on the measured cross sections was found to be the lowest for Al at 4.1% and the highest for Pb at 4.9%. For the other elements the error was in between these two values. Possible conclusions are drawn based on the present study.

The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering

Quasielastic incoherent neutron scattering (QENS) has proven to be a versatile tool to study self diffusion of atoms in liquid metals. Here it is shown, that coherent contributions to the signal in the smallq limit appear as aflat and energy independent constant to the QENS signal in single-component liquid metals even for systems with a small incoherent scattering cross section, like aluminum. Container-less processing via electromagnetic or electrostatic levitation devices, especially designed for QENS, enables the in-situ measurement on liquid metallic droplets of sizes between 5mm to 10mm in diameter. This gives access to the study of chemically reactive, refractory metallic melts and extends the accessible temperature range to undercoolings of several hundred Kelvin below the respective melting point. Compared to experiments using a thin-walled crucible giving hollow-cylindrical sample geometry it is shown that multiple scattering on levitated droplets is negligible for the analysis of the self-diffusion coefficient. QENS results of liquid germanium and 73 germanium isotope mixtures, titanium, nickel, copper and aluminum are reviewed. The self-diffusion coefficients of these systems are best described by an Arrhenius-type temperature dependence around their respective melting points.

VSI@ESS: Case study for a vibrational spectroscopy instrument at the european spallation source

Neutron Vibrational Spectroscopy is a well-established experimental technique where elementary excitations at relatively high frequency are detected via inelastic neutron scattering. This technique attracts a high interest in a large fraction of the scientific community in the fields of chemistry, materials science, physics, and biology, since one of its main applications exploits the large incoherent scattering cross section of the proton with respect to all the other elements, whose dynamics can be spectroscopically detected, even if dissolved in very low concentration in materials composed of much heavier atoms. We have proposed a feasibility study for a Vibrational Spectroscopy Instrument (VSI) at the European Spallation Source ESS. Here, we will summarize the preliminary design calculations and the corresponding McStas simulation results for a possible ToF, Inverted Geometry, VSI beamline.

Towards routine study of hydrogenous materials using powder neutron diffraction

Hydrogen (1H) is an element that is ubiquitous in chemistry and materials science. Neutron diffraction is the preferred technique for studying 1H-containing compounds, but is complicated by the high incoherent scattering cross section, which also varies with wavelength. This variation of scattering cross section as a function of wavelength/energy and chemical environment is not well understood.[1-2] This is surprising as it is the largest contributing factor to the scattering properties used in single crystal and powder neutron diffraction experiments to calculate the optimal sample size for hydrogen containing compounds and the tabulated data are given for fixed neutron velocity of 2200 m s-1 (approximately 1.8 Å). The use and current limitations of certain current generation neutron diffraction instruments to probe 1H materials has recently been described.[3] Here, I present work to validate an empirical correction for the incoherent scattering cross section of 1H as a function of incident neutron wavelength in the range 0.5 - 10 Å using continuous source, monochromatic wavelength measurements. The practical use of this is that a, potentially quantitative, correction for all neutron diffraction data, including time-of-flight (TOF) from pulsed sources, as a function of scattering angle and neutron path length will become possible. Implementation of methodology that allows routine H position definition from easily synthesised material (i.e. non-isotopically enriched, and in polycrystalline or small single crystal (≤ 50 μm) form) for both TOF and monochromatic neutron instruments would be both of widespread application. Additionally, i will present work on an instrument concept for a pulsed monochromatic powder diffractometer for the ESS, which will be built in Lund by the end of the current decade. This diffractometer will aim to specialise in the data collection and analysis of hydrogenous materials using a combination of diffraction and inelastic techniques.

Coherent and Incoherent Scattering Cross Sections of Some Lead and Sodium Compounds at Angles below 10° for 241Am Gamma Rays

We report the total (coherent + incoherent) scattering cross sections of some lead and sodium compounds measured at angles less than 10° for 241Am (59.54 keV) gamma rays. The experimental cross sections so obtained are compared with the data interpolated from theoretical compilations based on nonrelativistic Hartree-Fock (NRHF) model for the samples of interest. In the low momentum transfer region studied, it is observed that the nonrelativistic theoretical total scattering cross sections computed using HF form factor and scattering function tabulated by NRHF are quite adequate in explaining the measured total scattering cross sections.

Coherent scattering cross sections of some lanthanides for 241Am and 137Cs gamma rays at low momentum transfer

In this paper, we report the coherent scattering cross sections of some lanthanides at low momentum transfer in four angular ranges of (0°−4°), (0°−6°), (0°−8°) and for 241Am (59.54 keV) and 137Cs (661.6 keV) gamma rays. The coherent scattering cross sections were derived by subtracting the small contribution of the corresponding angle integrated incoherent scattering cross sections from the experimentally measured total (coherent + incoherent) scattering cross sections for the elements and energies of interest. The coherent scattering cross sections were found to agree with the corresponding theoretical cross sections within the range of experimental errors. The theoretical coherent scattering cross sections were computed by numerically integrating the S-matrix data of the elements in the angular ranges of interest. The incoherent scattering cross sections were based on the compilations which make use of the non-relativistic Hartree-Fock (NRHF) model for the atomic charge distribution.