Incident Energy Range Research Articles

Nucleon inelastic scattering cross sections on O16 and Si28

This paper reports cross-section measurements of the ($n,{n}^{\ensuremath{'}}$) and ($p,{p}^{\ensuremath{'}}$) reactions on $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$ at Geel Electron Linear Accelerator and at the 9-MV Tandem Accelerator of Horia Hulubei National Institute for Physics and Nuclear Engineering, respectively. The main purpose was to measure the neutron- and proton-induced inelastic $\ensuremath{\gamma}$-production cross sections for all observed transitions in $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, followed by the calculation of the corresponding total inelastic cross section. The results are compared with theoretical calculations performed using the talys 1.9 code, evaluated nuclear data, and previously reported experimental data. The broader goal of this work is to study whether and to what extent the neutron-induced inelastic cross sections of these nuclei can be inferred from those obtained using suitable charged particle reactions. We show that, by making use of the formal similarities between the neutron- and the proton-target optical model potentials and isospin symmetry in mirror nuclei, one can develop a procedure that combines experimental proton-induced inelastic cross sections with theoretical calculations to infer neutron inelastic cross sections. For $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, the precision associated with this procedure is around 10--20% for most of the incident energy range.

Accurate atomic momentum integrals and Compton profiles

Analytical expressions for integrals involving momentum density have been developed, and an algorithm for the efficient computation of Compton profiles (CPs) based in those equations is reported. The performance of the algorithm is tested by computing the CPs of atoms from helium to xenon for a wide range of incident photon energies. Calculations have been made at Hartree–Fock level (HF), using three different Slater basis sets, showing a good agreement with the experimental results.

Neutron measurements from the interaction of a thick Ta target with protons at different energies

Neutron dosimetry and spectrometry with a Ta target is of concern in an accelerator environment considering its enormous use in a proton accelerator. The Ta target has a unique advantage considering the generation of short half lived radionuclides upon interaction with protons. This advantage extends its use as the beam stopping material at various locations of an accelerator. However, this target has a varied range of reactions to produce neutrons and prompt gammas depending on proton energies. So in the present work, the neutron spectra were generated at various incident proton energies and neutron ambient dose equivalents were estimated close to the target projectile interaction at 90°with respect to the incident beam direction. A comparison of the spectral nature and doses were also done with measurements made by our earlier studies carried out at 0°. The comparison clearly showed that, apart from an increase in the low energy neutron yields at 90°, the overall yield distribution remains similar at both 0°and 90°angles with respect to the incoming beam direction. The ratio of the ambient neutron dose equivalent is found to reduce by a factor of 3–4 at 90°compared to 0°over the entire incident proton energy range. So, the dose equivalent ratio at two angles can be considered as independent of the incident projectile energy.

Positronium formation in positron-helium collisions in Debye plasma

SynopsisPositronium formation processes in positron-helium collisions with Debye potentials are studied using the screening approximation model in incident energy range from the threshold to 100 eV for screening parameters μ=0.00-0.25.

Positronium formation in collisions between positrons and Rb, Cs atoms with screened Coulomb interaction

SynopsisPositronium formation processes in collisions between positrons and Rb, Cs atoms with Debye potentials are studied using the screening approximation model for screening parameters μ=0.00-0.25 at incident energy range 2-60 eV.

Study of pre-equilibrium contributions in proton spectra of 59Co(n,xp) reaction using TALYS-1.9

In the present study we have calculated the proton spectra of 59Co(n,xp) using TALYS-1.9. TALYS uses all major reaction mechanisms like compound, pre-equilibrium and direct reactions. The contribution from compound nuclear reaction is calculated using optical model calculations. For pre-equilibrium contributions we have used two particle exciton model. The results from the present work suggests the presence of significant pre-equilibrium emission components in the 59Co(n,xp) system within the range of incident projectile energies from 37.5 to 62.7 MeV.

Low energy (6-18 eV) electron scattering from condensed thymidine (dT) III: absolute electronic excitation cross sections.

Absolute cross sections (CSs) for electronic excitation by low-energy electron (LEE) scattering, from condensed thymidine (dT) in the 6-18 eV incident energy range, were measured by high-resolution electron energy loss spectroscopy (HREELS). Various electron energy loss (EEL) spectra were acquired using 1 ML of dT condensed on a multilayer film of Ar held at about 20 K under ultra-high vacuum (∼1 × 10-11 Torr). dT is one of the most complex DNA constituents to be studied by HREELS and these spectra provide the first LEE energy-loss data for electronic excitation of a nucleoside. CSs for transitions to the states 13A', 13A'', 23A', 21A', 33A', 23A'', 43A', 33A'', 53A' and 51A' of dT were extracted from the EEL spectra. These states correlate to those previously measured for the thymine moiety. Two broad resonances are observed in the energy dependence of the CSs at around 8 and 10 eV; these energies are close to those found in earlier gas- and solid-phase studies on the interaction of LEEs with dT, thymine and related molecules. A quantitative comparison between the electronic CSs of dT and those of thymine and tetrahydrofuran indicates that no variation is induced in the electronic CSs of thymine upon chemically binding to a deoxyribose group.

Experiments with neutron induced neutron emission from U-235, Pu-239, and graphite

A neutron induced neutron emission experiment was conducted as the Los Alamos Neutron Science Center (LANSCE) facility at Los Alamos National Laboratory (LANL). In this experiment, a sample was placed in a well collimated neutron beam and was surrounded by an array of 28 fast neutron detectors (EJ-309). The experiment was performed with a neutron flight path of 21.5 m from the source to the sample, and 1 m from the sample to the detectors. The neutron emission from the sample was measured as a function of neutron time of flight covering an incident energy range from 0.7- 20 MeV. The samples included U-235, Pu-239, carbon (graphite), and blanks that matched the encapsulation of the sample. The measured samples were constantly cycled in and out of the neutron beam. This type of experiment measures neutron emission from all reactions occurring in the sample such as fission and elastic and inelastic scattering. Similar to the methodology previously developed at RPI [1], the measurements were compared with detailed simulations of the experiment using different cross section evaluations for the sample. The observed differences can be attributed to the evaluated neutron cross section and angular distributions. The carbon sample was used as a reference to validate both the experiment and simulation methodology and showed good agreement between experiments and simulations. A review of the experimental setup, analysis methods, and some of the results will be presented.

Toward a reliable description of (p,pN) reactions in the distorted-wave impulse approximation

Background: Proton-induced nucleon knockout $(p,pN)$ reactions have been successfully used to study the single-particle nature of stable nuclei in normal kinematics with the distorted-wave impulse approximation (DWIA) framework. Recently, these reactions have been applied to rare-isotope beams at intermediate energies in inverse kinematics to study the quenching of spectroscopic factors.Purpose: Our goal is to investigate the effects of various corrections and uncertainties within the standard DWIA formalism on the $(p,pN)$ cross sections. The consistency of the extracted reduction factors between DWIA and other methods is also evaluated.Method: We analyze the $(p,2p)$ and $(p,pn)$ reaction data measured at the ${\mathrm{R}}^{3}\mathrm{B}$-LAND setup at GSI for carbon, nitrogen, and oxygen isotopes in the incident energy range of 300--450 MeV/u. Cross sections and reduction factors are calculated by using the DWIA method. The transverse momentum distribution of the $^{12}\mathrm{C}(p,2p)^{11}\mathrm{B}$ reaction is also investigated.Results: We have found that including the nonlocality corrections and the M\o{}ller factor affects the cross sections considerably. The proton-neutron asymmetry dependence of reduction factors extracted by the DWIA calculation is very weak and consistent with those given by other reaction methods and ab initio structure calculations.Conclusions: The results found in this work provide a detailed investigation of the DWIA method for $(p,pN)$ reactions at intermediate energies. They also suggest that some higher-order effects, which is essential for an accurate cross-section description at large recoil momentum, is missing in the current DWIA and other reaction models.

Scattering of e± from N2 in the energy range 1 eV–10 keV

The differential, integrated elastic, inelastic, total, momentum transfer, viscosity, and ionisation cross sections for electron and positron scattering from the homonuclear diatomic nitrogen molecule over an incident energy range of 1 eV–10 keV are calculated using the additivity rule. Dirac partial wave analysis is employed to calculate the cross sections of the constituent atoms of molecules, using a complex optical model potential (OPM). Comparison of our results of the additivity rule with the available experimental data and other theoretical predictions is presented. Our findings produce reasonable results in intermediate and high energies.

Advances in Analysis of Microcalorimeter Gamma-Ray Spectra

Microcalorimeters based on transition-edge sensors (TESs) have been successfully deployed in numerous spectroscopic instruments that operate over a large range of incident photon energies. TES microcalorimeter arrays combine unmatched energy resolution with broadband spectral coverage and high quantum efficiency. An important application requiring these characteristics is nondestructive isotopic analysis via gamma-ray spectroscopy of the complex mixtures of actinide isotopes found in the nuclear fuel cycle. Steady progress has been made over the last ten years to develop TES microcalorimeter instruments for this application, leading to arrays that demonstrate significantly better energy resolution than the state-of-the-art high-purity germanium (HPGe) sensors. However, further algorithm development and automation of the data analysis procedure have been required to bring these systems closer to being ready for production use. In this article, we describe recent advances in data analysis techniques for gamma-ray data acquired with microcalorimeter systems. In particular, we discuss new approaches to automated calibration of our spectra, and a new approach for quantifying the uncertainty of peak area estimation for isolated peaks. Our data analysis pipeline has also been automated, requiring minimal manual intervention for full processing of data sets, with performance that is sufficient to allow future deployment of real-time spectrum generation. We show that, using this pipeline, we are able to achieve ~0.25% statistical uncertainty in isotope ratios, which indicates that if systematic errors are controlled, microcalorimeter arrays can achieve better than 1% total uncertainty in these measurements.

A study on the validity of the first Born approximation for high-energy electron scattering with nitrogen molecules

The first Born approximation is one of the most extensively used principles to deal with scattering processes, especially for fast projectiles. In the case of fast electron scattering, an empirical criterion has been proposed and widely accepted that a good match among the fast electron scattering results with higher and higher incident electron energies is enough to demonstrate the validity of the first Born approximation. However, it is found that the mutually agreed experimental generalized oscillator strength of our electron scattering measurement and the cited ones of the and states of nitrogen at a wide range of incident electron energies is obviously smaller than the generalized oscillator strength obtained by our vibronically resolved inelastic x-ray scattering experiment, in which the first Born approximation is always satisfied. Such a phenomenon indicates that the empirical criterion is not strict, and our understanding of electron scattering with multi-electron system is far from complete.

A compact and energy-efficient ultrasound receiver using PTAT reference circuit

Portable and embedded ultrasound applications require energy-efficient receivers that can operate over a wide range of incident ultrasonic energy. In this paper we show that by directly injecting the ultrasonic signal into a proportional-to-absolute-temperature (PTAT) reference circuit, the pre-amplification and rectification stages used in a conventional ultrasonic receiver can be eliminated which leads to a significant improvement in the system energy-efficiency. The PTAT circuit self-biases itself in accordance to the magnitude of the incident ultrasound pressure signal and is also configured to function as an active diode (with threshold voltage of ≈25 mV) to achieve signal rectification. In this paper we present measurement results obtained from a PTAT-based ultrasound receiver that has been prototyped in a 0.5 μm CMOS process, and we compare the performance to a standard transconductance amplifier (TCA) based design that has also been prototyped in the same process. The improvement in input dynamic range was measured to be 25 dB and sensitivity of the PTAT-based receiver was measured to be 21 Hz/mV when the biasing current is 16.67 nA. We also present the bit-error-rate (BER) performance when the receiver circuit is used for a substrate communications application where ultrasound is used for transmitting and receiving data through an Aircraft grade Aluminum plate.

Diagnostics of low-temperature neon plasma through a fine-structure resolved collisional–radiative model

A collisional–radiative (CR) model for low-temperature Ne plasma is developed. Various radiative and collisional processes involving the ground 2p6 and the excited 2p53s, 2p53p, 2p53d, 2p54s and 2p54p states are considered in the plasma. First, we calculate a complete set of required electron-impact excitation cross-sections of Ne, which is an important process in such low-temperature plasma. We used the relativistic distorted wave (RDW) theory and calculated electron excitation cross-sections for the transitions from the ground 2p6 state to the excited 2p53s, 2p53p, 2p53d, 2p54s and 2p54p states, as well as from the excited state 2p53s to the 2p53p and 2p54p excited states of the Ne atom in a wide range of incident electron energies from the threshold to 500 eV. The ground and different excited states of the Ne are represented through the multiconfiguration Dirac–Fock wave functions, which are obtained using the GRASP2K code. To ascertain the reliability of the obtained wave functions, we calculated the oscillator strengths for different dipole allowed transitions, and compared them with the available experimental and theoretical results. Further, the calculated detailed RDW cross-sections are presented and compared with the available experimental and other theoretically calculated values. The cross-sections for 2p53s to 2p54p and 2p53s (J = 1 only) to 2p53p are reported for the first time. The complete set of calculated electron excitation cross-sections of different transitions of Ne along with other processes are used to develop the CR model. The model has been applied to the diagnostics of low-temperature Ne plasma by coupling it to the optical emission and absorption measurements of Boffard et al (2012 J. Phys. D: Appl. Phys. 45 382001, and 2009 Plasma Sources Sci. Technol. 18 035017). The extracted values of electron density, electron temperature and the calculated 1si level populations have been compared with the corresponding measurements available in the pressure range of 5–25 mTorr and are found to be in excellent agreement.

Challenging microscopic structure and reaction models for nucleon scattering off nuclei in the A=208 mass region

We present a microscopic description of neutron and proton elastic and inelastic scattering off $^{206,207,208}\mathrm{Pb}$ and $^{209}\mathrm{Bi}$ together with new medium-energy (7.5--15.5 MeV) neutron elastic and inelastic scattering measurements for various low-energy levels. The Jeukenne, Lejeune, Mahaux (JLM) semimicroscopic folding model provides the relevant optical and transition potentials used to calculate the elastic and inelastic cross sections. Rearrangement corrections that account for proton and neutron density variations during the transition are considered. The nuclear diagonal and transition densities are calculated from a (quasiparticle) random phase approximation [(Q)RPA] structure model implemented with the Gogny D1S interaction. Calculated differential elastic and inelastic cross sections are mostly in very good agreement with available data. Predicted nuclear structure properties as well as scattering calculations and measurements for the yrast quadrupole excitation in $^{206}\mathrm{Pb}$ are carefully discussed. The rearrangement corrections to inelastic scattering form factors are shown to reduce medium energy nucleon inelastic cross section by up to 55%. The magnitude of these corrections changes depending on the probe, incident energy, multipolarity, and nature of the transitions considered. The combined analysis of nuclear structure properties and those for nucleon scattering cross sections measured previously over a range of incident energies provides stringent tests of present microscopic models and helps distinguish those scattering data which most likely call for revision.

Measurement of ν¯μ charged-current single π− production on hydrocarbon in the few-GeV region using MINERvA

The antineutrino scattering channel $\bar{\nu}_{\mu} \,\text{CH} \rightarrow \mu^{+} \,\pi^{-} \,X$(nucleon(s)) is analyzed in the incident energy range 1.5 to 10 GeV using the MINERvA detector at Fermilab. Differential cross sections are reported as functions of $\mu^{+}$ momentum and production angle, $\pi^{-}$ kinetic energy and production angle, and antineutrino energy and squared four-momentum transfer. Distribution shapes are generally reproduced by simulations based on the GENIE, NuWro, and GiBUU event generators, however GENIE (GiBUU) overestimates (underestimates) the cross-section normalizations by 8% (10%). Comparisons of data with the GENIE-based reference simulation probe conventional treatments of cross sections and pion intranuclear rescattering. The distribution of non-track vertex energy is used to decompose the signal sample into reaction categories, and cross sections are determined for the exclusive reactions $\mu^{+} \pi^{-} n$ and $ \mu^+ \pi^{-} p$. A similar treatment applied to the published MINERvA sample $\bar{\nu}_{\mu} \,\text{CH} \rightarrow \mu^{+} \,\pi^{0} \,X$(nucleon(s)) has determined the $\mu^{+} \pi^{0} n$ cross section, and the latter is used with $\sigma(\pi^{-} n)$ and $\sigma(\pi^{-} p)$ to carry out an isospin decomposition of $\bar{\nu}_{\mu}$-induced CC($\pi$). The ratio of magnitudes and relative phase for isospin amplitudes $A_{3}$ and $A_{1}$ thereby obtained are: $R^{\bar{\nu}} = 0.99 \pm 0.19$ and $\phi^{\bar{\nu}} = 93^{\circ} \pm 7^{\circ}$. Our results are in agreement with bubble chamber measurements made four decades ago.

Experimental setup combining in situ hard X-ray photoelectron spectroscopy and real-time surface X-ray diffraction for characterizing atomic and electronic structure evolution during complex oxide heterostructure growth.

We describe the next-generation system for in situ characterization of a complex oxide thin film and heterostructure growth by pulsed laser deposition (PLD) using synchrotron hard X-rays. The system consists of a PLD chamber mounted on a diffractometer allowing both real-time surface X-ray diffraction (SXRD) and in situ hard X-ray photoelectron spectroscopy (HAXPES). HAXPES is performed in the incident X-ray energy range from 4 to 12 keV using a Scienta EW4000 electron energy analyzer mounted on the PLD chamber fixed parallel with the surface normal. In addition to the standard application mode of HAXPES for disentangling surface from bulk properties, the increased penetration depth of high energy photoelectrons is used for investigation of the electronic structure changes through thin films grown deliberately as variable thickness capping layers. Such heterostructures represent model systems for investigating a variety of critical thickness and dead layer phenomena observed at complex oxide interfaces. In this new mode of operation, in situ HAXPES is used to determine the electronic structure associated with unique structural features identified by real-time SXRD during thin film growth. The system is configured for using both laboratory excitation sources off-line and on-line operation at beamline 33-ID-D at the Advanced Photon Source. We illustrate the performance of the system by preliminary scattering and spectroscopic data on oxygen vacancy ordering induced perovskite-to-brownmillerite reversible phase transformation in La2/3Sr1/3MnO3 films capped with oxygen deficient SrTiO3-δ (100) layers of varying thickness.

A novel comprehensive utilization of vanadium slag/epoxy resin/antimony trioxide ternary composite as gamma ray shielding material by MCNP 6.2 and BXCOM

New research on composite materials was proposed for both gamma ray shielding and fireproofing. When compared to concrete, composite materials show up higher shielding properties in the 0.015 MeV–15 MeV incident energy range. The composite was prepared with vanadium slag, epoxy resin and antimony-trioxide. Different ratios of ternary composite were investigated in order to determine the optimum ratio for shielding and anti-flame properties. Photon atomic parameters with shielding were determined by BXCOM and MCNP 6.2. BXCOM program determines the buildup factors (both EBF and EABF) in the 0.015–15 MeV energy range for up to 40 mean free path (mfp) penetration depth. It uses geometric progression (G-P) fitting method. The effective electron number (Neff) and the effective atomic number (Zeff) were also obtained with the BXCOM software. Furthermore, parameters such as the mass attenuation coefficients (μρ), half-value layer (HVL) and tenth-value layer (TVL) were determined by MCNP 6.2 in order to confirm and compare with WinXCOM results. Obtained results may be concluded to have preferable shielding properties for the composite as an alternative to concrete. Antimony-trioxide (x=0.03), was found to exhibit the minimum EBF and EABF values, and is a convenient radiation shielding material. The Epoxy resin-vanadium slag and antimony-trioxide ternary glassy composite indicates better radiation shielding properties than concrete, but weaker than lead.

Electron impact elastic scattering from methane and silane molecules

Analytical expressions for the static potentials of the electron scattering from methane (CH4) and silane (SiH4) molecules have been obtained using Gaussian wave functions. Subsequently, we have studied the elastic scattering of electrons from these molecules utilizing their static potentials along with exchange and polarization potentials as well as a purely imaginary absorption potential to represent scattering into inelastic channels. The multi-centre target molecules are represented as STO-6G Gaussian wave functions. We have calculated the differential, integrated and momentum transfer cross sections in a wide range of incident electron energies from 10 to 500 eV. Comparisons of our results for CH4 and SiH4 with the available measurements and theoretical results are presented.

Fission fragment angular anisotropy in neutron-induced fission of U235 measured with a time projection chamber

Fission fragment angular distributions can provide an important constraint on fission theory, improving predictive fission codes, and are a prerequisite for a precise ratio cross section measurement. Available anisotropy data is sparse, especially at neutron energies above 5 MeV. For the first time, a three-dimensional tracking detector is employed to study fragment emission angles and provide a direct measurement of angular anisotropy. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration has deployed the fission time projection chamber (fissionTPC) to measure nuclear data with unprecedented precision. The fission fragment anisotropy of $^{235}$U has been measured over a wide range of incident neutron energies from 180 keV to 200 MeV; a careful study of the systematic uncertainties complement the data.