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DOE OSTI2015

Z-dependence analysis of M x-ray production cross sections for heavy elements with 60≤Z≤90 by protons impact

Motivated by the large deviation between the experiment and the predictions of the most often used model of ionization process by a charged particle, namely ECPSSR model, a large database of experimental M-shell X-ray production cross-sections by protons energies varying from 0.1 to 4.0 MeV for elements with atomic number 60 ≤ Z ≤ 90, is collected from various sources published from 1980 till 2009 to deduce an empirical M x-ray production cross section. This latter is then deduced from the available experimental data as a function of the scaled velocity parameter by using the whole range of elements (collective analysis) or by introducing the dependence of these cross sections on the atomic number of the target, noted as “Z-dependence analysis” in addition to the collective one. The corresponding results and their deviation from the experimental data are presented for selected elements. Also, a comparison is made for selected elements between our results and other theoretical as well as experimental works.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

Diffractive, inelastic and total cross sections in high energy pp, pA and γ*A reactions with the dipole formalism

The Lund Monte Carlo model DIPSY has recently been extended to ions to study elastic, inelastic and diffractive processes in high energy collisions between electrons, protons and nuclei. In this BFKL-based dipole formalism of parton interactions fluctuations are naturally included and adding them to the pomeron ladder substantially determine the diffractive excitation cross sections of the processes. Starting from √(s{sub NN})=200 GeV and √(s{sub γ*N})=100 GeV we provide results for pp, pA and γ*A total, inelastic and diffractive cross sections that are shown and discussed in case of pp, pO, pCu, pPb and γ*Au reactions. We find good agreement with pp and pPb data. We find that the diffractive cross sections are relatively small compared to the total ones but with increasing collision energies they grow faster than the elastic or the inelastic ones. We make a comparison to calculations obtained by the more conventional method of the Glauber Model MC, too.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Cross Sections for Electron Collisions with Methane

Cross section data are compiled from the literature for electron collisions with methane (CH{sub 4}) molecules. Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment. The data derived from swarm experiments are also considered. For each of these processes, the recommended values of the cross sections are presented. The literature has been surveyed through early 2014.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2015

SN-detection in LAr-TPC and the quest for (ν-Ar) cross sections

Neutrino-nucleus cross sections are of relevance to supernova astrophysics. These cross-sections can be grouped into three categories, those that affect supernova dynamics, supernova nucleosynthesis, and terrestrial supernova neutrino detection, each of which would benefit from experimental study. In this report only the relevance of an accurate knowledge of neutrino-target nucleus cross sections for SN detection will be discussed, in particular for the case of Argon, the active target material of LAr-TPC detectors currently under construction or proposed for future very massive underground experiments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

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

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

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl–2-butene and 2,3-dimethyl–2-butene

We report electron-scattering cross sections determined for 2-methyl–2-butene [(H{sub 3}C)HC = C(CH{sub 3}){sub 2}] and 2,3-dimethyl–2-butene [(H{sub 3}C){sub 2}C = C(CH{sub 3}){sub 2}] molecules. Absolute grand-total cross sections (TCSs) were measured for incident electron energies in the 0.5–300 eV range, using a linear electron-transmission technique. The experimental TCS energy dependences for the both targets appear to be very similar with respect to the shape. In each TCS curve, three features are discernible: the resonant-like structure located around 2.6–2.7 eV, the broad distinct enhancement peaking near 8.5 eV, and a weak hump in the vicinity of 24 eV. Theoretical integral elastic (ECS) and ionization (ICS) cross sections were computed up to 3 keV by means of the additivity rule (AR) approximation and the binary-encounter-Bethe method, respectively. Their sums, (ECS+ICS), are in a reasonable agreement with the respective measured TCSs. To examine the effect of methylation of hydrogen sides in the ethylene [H{sub 2}C = CH{sub 2}] molecule on the TCS, we compared the TCS energy curves for the sequence of methylated ethylenes: propene [H{sub 2}C = CH(CH{sub 3})], 2-methylpropene [H{sub 2}C = C(CH{sub 3}){sub 2}], 2-methyl–2-butene [(H{sub 3}C)HC = C(CH{sub 3}){sub 2}], and 2,3-dimethyl–2-butene [(H{sub 3}C){sub 2}C = C(CH{sub 3}){sub 2}], measured in the same laboratory. Moreover, the isomeric effect is also discussed for the C{sub 5}H{sub 10} and C{sub 6}H{sub 12} compounds.

2-METHYLPROPENE↗

DOE OSTI2015

Coherent to incoherent cross section ratio for 59.54 keV gamma rays at scattering angle of 110°

The coherent (Rayleigh) to incoherent (Compton) scattering cross-section ratio of elements, in the range 13 ≤ Z ≤ 82, are determined experimentally for 59.54 keV incident gamma photons. An HPGe (High purity germanium) semiconductor detector is employed, at scattering angle of 110°, to record the spectra originating from interactions of incident gamma photons with the target under investigation. The intensity ratio of Rayleigh to Compton scattered peaks observed in the recorded spectra, and corrected for photo-peak efficiency of gamma detector and absorption of photons in the target and air, along with the other required parameters provides the differential cross-section ratio. The measured values of cross-section ratio are found to agree with theoretical predictions based upon non-relativistic form factor, relativistic form factor, modified form factor and S-matrix theory.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Rotationally inelastic scattering of NO(A{sup 2}Σ{sup +}) + Ar: Differential cross sections and rotational angular momentum polarization

We present the implementation of a new crossed-molecular beam, velocity-map ion-imaging apparatus, optimized for collisions of electronically excited molecules. We have applied this apparatus to rotational energy transfer in NO(A{sup 2}Σ{sup +}, v = 0, N = 0, j = 0.5) + Ar collisions, at an average energy of 525 cm{sup −1}. We report differential cross sections for scattering into NO(A{sup 2}Σ{sup +}, v = 0, N′ = 3, 5, 6, 7, 8, and 9), together with quantum scattering calculations of the differential cross sections and angle dependent rotational alignment. The differential cross sections show dramatic forward scattered peaks, together with oscillatory behavior at larger scattering angles, while the rotational alignment moments are also found to oscillate as a function of scattering angle. In general, the quantum scattering calculations are found to agree well with experiment, reproducing the forward scattering and oscillatory behavior at larger scattering angles. Analysis of the quantum scattering calculations as a function of total rotational angular momentum indicates that the forward scattering peak originates from the attractive minimum in the potential energy surface at the N-end of the NO. Deviations in the quantum scattering predictions from the experimental results, for scattering at angles greater than 10°, are observed to be more significant for scattering to odd final N′. We suggest that this represents inaccuracies in the potential energy surface, and in particular in its representation of the difference between the N- and O-ends of the molecule, as given by the odd-order Legendre moments of the surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Following electron impact excitations of Rn, Ra, Th, U and Pu single atom L sub-shells ionization cross section calculations by using Lotz’s equation

L shell ionization cross section and L{sub i} subshells ionization cross sections of Rn, Ra, Th, U, Pu atoms calculated. For each of atoms, ten different electron impact energy values (E{sub o}) are used. Calculations carried out by using Lotz equation in Matlab. First, calculations done for non-relativistic case by using non-relativistic Lotz equation then repeated with relativistic Lotz equation. σ{sub L} total and σ{sub Li}(i = 1,2,3) subshells ionisation cross section values obtained for E{sub o} values in the energy range of E{sub Li} <E{sub o}<4E{sub Li} for each atom. Starting almost from E{sub o} = E{sub Li} values of the each sub shell ionization threshold energy, σ{sub L} total and σ{sub Li} (i = 1,2,3) are increasing rapidly with E{sub o}. For a fixed E{sub o} = 3.E{sub Li}), while Z increases from 86<Z<94, σL and σLi (i = 1, 2,3) are decrease. These results will also help to understand some σ{sub Li}(i = 1,2,3) subshells results obtained from other electron-atom impact studies.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2016

Axisymmetric electrostatic magnetohydrodynamic oscillations in tokamaks with general cross-sections and toroidal flow

The frequency spectrum and mode structure of axisymmetric electrostatic oscillations [the zonal flow (ZF), sound waves (SW), geodesic acoustic modes (GAM), and electrostatic mean flows (EMF)] in tokamaks with general cross-sections and toroidal flows are studied analytically using the electrostatic approximation for magnetohydrodynamic modes. These modes constitute the “electrostatic continua.” Starting from the energy principle for a tokamak plasma with toroidal rotation, we showed that these modes are completely stable. The ZF, the SW, and the EMF could all be viewed as special cases of the general GAM. The Euler equations for the general GAM are obtained and are solved analytically for both the low and high range of Mach numbers. The solution consists of the usual countable infinite set of eigen-modes with discrete eigen-frequencies, and two modes with lower frequencies. The countable infinite set is identified with the regular GAM. The lower frequency mode, which is also divergence free as the plasma rotation tends to zero, is identified as the ZF. The other lower (zero) frequency mode is a pure geodesic E×B flow and not divergence free is identified as the EMF. The frequency of the EMF is shown to be exactly 0 independent of plasma cross-section or its flow Mach number. We also show that in general, sound waves with no geodesic components are (almost) completely lost in tokamaks with a general cross-sectional shape. The exception is the special case of strict up-down symmetry. In this case, half of the GAMs would have no geodesic displacements. They are identified as the SW. Present day tokamaks, although not strictly up-down symmetric, usually are only slightly up-down asymmetric. They are expected to share the property with the up-down symmetric tokamak in that half of the GAMs would be more sound wave-like, i.e., have much weaker coupling to the geodesic components than the other half of non-sound-wave-like modes with stronger coupling to the geodesic displacements. Based on the general notion that the geodesic component of the GAM is more effective in tearing up the eddies in the electrostatic turbulence, it is important to preferentially excite the GAMs that are non-sound-wave like to maximize the efficiency on turbulence suppression through external means. Finally, approximate formulae for the frequencies of the EMF, ZF, SW, and the GAM for a large aspect ratio circular tokamak rotating at low Mach numbers are also provided.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2016

The first potential energy surfaces for the C{sub 6}H{sup −}–H{sub 2} and C{sub 6}H{sup −}–He collisional systems and their corresponding inelastic cross sections

Molecular anions have recently been detected in the interstellar and circumstellar media. Accurate modeling of their abundance requires calculations of collisional data with the most abundant species that are usually He atoms and H{sub 2} molecules. In this paper, we focus on the collisional excitation of the first observed molecular anion, C{sub 6}H{sup −}, by He and H{sub 2}. Theoretical calculations of collisional cross sections rely generally on ab initio interaction potential energy surfaces (PESs). Hence, we present here the first PESs for the C{sub 6}H{sup −}–H{sub 2} and C{sub 6}H{sup −}–He van der Waals systems. The ab initio energy data for the surfaces were computed at the explicitly correlated coupled cluster with single, double, and scaled perturbative triple excitations level of theory. The method of interpolating moving least squares was used to construct 4D and 2D analytical PESs from these data. Both surfaces are characterized by deep wells and large anisotropies. Analytical models of the PESs were used in scattering calculations to obtain cross sections for low-lying rotational transitions. As could have been anticipated, important differences exist between the He and H{sub 2} cross sections. Conversely, no significant differences exist between the collisions of C{sub 6}H{sup −} with the two species of H{sub 2} (para- and ortho-H{sub 2}). We expect that these new data will help in accurately determining the abundance of the C{sub 6}H{sup −} anions in space.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

EFFECTS OF NITROGEN PHOTOABSORPTION CROSS SECTION RESOLUTION ON MINOR SPECIES VERTICAL PROFILES IN TITAN’S UPPER ATMOSPHERE

The significant variations in both measured and modeled densities of minor species in Titan’s atmosphere call for the evaluation of possible influencing factors in photochemical modeling. The effect of nitrogen photoabsorption cross section selection on the modeled vertical profiles of minor species is analyzed here, with particular focus on C{sub 2}H{sub 6} and HCN. Our results show a clear impact of cross sections used on all neutral and ion species studied. Affected species include neutrals and ions that are not primary photochemical products, including species that do not even contain nitrogen. The results indicate that photochemical models that employ low-resolution cross sections may significantly miscalculate the vertical profiles of minor species. Such differences are expected to have important implications for Titan’s overall atmospheric structure and chemistry.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2026

Search for the 𝑌⁡(2175) in the Photoproduction Cross Section Measurement of 𝛾⁢𝑝 → 𝜙⁢𝜋 + ⁢𝜋 − ⁢𝑝 at GlueX

Based on 334 pb −1 of photoproduction data collected with the GlueX detector at Jefferson Lab, we have measured for the first time the cross section of the exclusive reaction 𝛾+𝑝→𝜙⁡(1020)⁢𝜋 + ⁢𝜋 − ⁢𝑝 by reconstructing the final state 𝐾 +⁢ 𝐾 − ⁢𝜋 + ⁢𝜋 − ⁢𝑝 produced with a photon beam of energies between 8.0 and 11.6 GeV. Based on the measured differential cross section, we have performed a search for the strangeoniumlike exotic candidate 𝑌⁡(2175), recently renamed to 𝜙⁡(2170). This state has been reported by different 𝑒 + ⁢𝑒 − annihilation experiments and it is addressed here for the first time in a photoproduction experiment. We do not find evidence for this state when using the resonance parameters quoted by the Particle Data Group and provide upper limits on the photoproduction cross section. Instead, we find a structure at a mass of 𝑚⁡(𝜙⁢𝜋 + ⁢𝜋 − ) = 2.24 GeV/𝑐 2 with a statistical significance of about 5⁢𝜎. The parameters of this structure differ from those quoted by the Particle Data Group for the 𝜙⁡(2170) and are consistent with a previous observation in 𝑒 + ⁢𝑒 − annihilation. In addition, there is evidence for a second structure at 1.82 GeV/𝑐 2 .

Exotic mesons↗

DOE OSTI2017

Measurement of the D + -meson production cross section at low transverse momentum in p p ¯ collisions at s = 1.96 TeV

We report on a measurement of the D + -meson production cross section as a function of transverse momentum (p T ) in proton-antiproton (p$\bar{p}$) collisions at 1.96 TeV center-of-mass energy, using the full data set collected by the Collider Detector at Fermilab in Tevatron Run II and corresponding to 10 fb -1 of integrated luminosity. We use D + →K - π + π + decays fully reconstructed in the central rapidity region |y|<1 with transverse momentum down to 1.5 GeV/c, a range previously unexplored in p$\bar{p}$ collisions. Inelastic p$\bar{p}$ scattering events are selected online using minimally biasing requirements followed by an optimized offline selection. The K - π + π + mass distribution is used to identify the D + signal, and the D + transverse impact-parameter distribution is used to separate prompt production, occurring directly in the hard-scattering process, from secondary production from b-hadron decays. We obtain a prompt D + signal of 2950 candidates corresponding to a total cross section σ(D + ,1.5 T <14.5 GeV/c,|y|<1)=71.9±6.8(stat)±9.3(syst) μb. While the measured cross sections are consistent with theoretical estimates in each p T bin, the shape of the observed p T spectrum is softer than the expectation from quantum chromodynamics. The results are unique in p$\bar{p}$ collisions and can improve the shape and uncertainties of future predictions.

(K-↗

DOE OSTI2022

Magneto-Mechanical Optimization of Cross-Sections for $ \text{cos}(\theta)$Accelerator Magnets

The cross-section design of cos (θ) superconducting magnets is historically developed in a two-step process: initially, the coil geometry is defined on the basis of magnetic optimizations; then, the structure is designed around the coil. The first step searches for the best coil cross-section maximizing the magnetic field, margin, field quality and conductor efficiency. The latter step aims at limiting the coil stresses and deformations. However, the coil design, defined with the initial magnetic optimization, can influence the mechanical behaviour of the magnet, altering, for example, the peak stress during operation. As the critical current is a function of the applied strain, the mechanical implications of the coil cross-section design can limit the achievable performance. In this paper we propose an integrated optimization process that targets the peak stress on the conductor in addition to the magnetic objectives. Here the results are presented for a sample high-field Nb 3 Sn dipole: a 4-layer design aiming at ultimate conductor performance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

New results of measurement of cross sections for electron-positron annihilation to hadrons with the SND detector at VEPP-2000

A survey of preliminary results of experiments with the SND detector at the VEPP-2000 e{sup +}e{sup −} collider in the energy range of √s = 1000–2000 MeV MeV is presented. The cross sections for the processes e{sup +}e{sup −} → π{sup 0}π{sup 0}γ, e{sup +}e{sup −} → π{sup +}π{sup −}π{sup 0}π{sup 0}, e{sup +}e{sup −} → π{sup +}π{sup −}π{sup 0}, e{sup +}e{sup −} → π{sup +}π{sup −}η, and e{sup +}e{sup −} → pp̄ were measured. The measured cross sections agree with the results of earlier measurements but have a higher precision. The cross section for the process e{sup +}e{sup −} → ηγ in the energy range extending from 1.4 to 2 GeV was measured for the first time. The ratio G{sub E}/G{sub M} for the neutron was measured for the first time in the timelike region.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

Cross section for the reaction {sup 115}In(γ, γ′){sup 115m} In in the region of the E1 giant resonance

The cross section for the reaction {sup 115}In(γ, γ′){sub 115m}In was measured for photon energies in the range of E{sub γ} ≅ 4–46 MeV. The parameters of the peak in this cross section near the threshold for the reaction {sup 115}In(γ, n), (E{sub γ}){sub (γ,n)}{sup thr}, were refined. It is shown that, in the cross section for the reaction {sup 115}In(γ, γ′){sup 115m}In at Eγ ∼ 27 MeV, there is no second peak for which δ{sub II}{sup int} would exceed about 0.2δ{sub I}{sup int} for the peak at E{sub γ} ∼ (E{sub γ}){sub (γ,n)}{sup thr}. The possibility of employing this reaction both in studying photonuclear reaction physics and in monitoring bremsstrahlung photons in gamma-activation studies was examined.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

New data on cross sections for partial and total photoneutron reactions on the isotopes {sup 91,94}Zr

Experimental data on {sup 91,94}Zr photodisintegration that were obtained in a beam of quasimonoenergetic annihilation photons by the method of neutron multiplicity sorting are analyzed. It is found that the cross sections for the (γ, 1n), (γ, 2n), and (γ, 3n) reactions on both isotopes do not meet the objective data-reliability criteria formulated earlier. Within the experimental–theoretical method for evaluating partial-reaction cross sections that satisfy these criteria, new data on the cross sections for the aforementioned partial reactions, as well as for the (γ, sn) = (γ, 1n) + (γ, 2n) + (γ, 3n) +... total photoneutron reaction, are obtained for the isotopes {sup 91,94}Zr.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗