No abstract available

[en] The g9a experiment using the CLAS detector in Hall B of Jefferson Lab will measure double-polarization observables using a polarized energy-tagged photon beam in conjunction with the frozen spin target, FROST. This contribution describes the extraction of the G double polarization observable in the single pion photoproduction using a linearly polarized photon beam in the energy range 730-2300 MeV and the longitudinally polarized frozen spin target, FROST.

[en] The Canadian Super-Critical Water Reactor (SCWR) uses a vertical pressure-tube concept, with D₂O moderator, super-critical H₂O coolant and thorium-based fuel. To further recent MCNP modelings of the SCWR core, it was necessary to simulate a Liquid Injection Shutdown System (LISS), which involves reactivity reduction by liquid neutron poison injection. By utilizing previous studies on similar reactor concepts, a LISS has been modeled in MCNP for the SCWR, demonstrating sufficient and timely reactivity reduction. In particular, the model propagates physically realistic neutron poison jets over multiple time steps, thereby simulating a realistic LISS in MCNP. (author)

[en] Highlights: • 77 Heavy-water moderated critical ZED-2 experiments analyzed with MCNP and KENO. • SCALE used to find nuclear data adjustments minimizing MCNP a priori biases. • MCNP patch used to repeat analysis using nuclear data adjustments from SCALE. • Present a detailed code-to-code comparison of of a priori and a postiori k_eff biases. • SCALE results consistently underestimate impact of proposed corrections by 1–2 mk. - Abstract: Many nuclear data uncertainty propagation methods are implemented on the basis of first-order perturbation theory. These methods are complex and integral verification using direct perturbation of the nuclear cross section data is difficult due to the structure of nuclear data files. We present a new implementation of the direct perturbation method, which eliminates the need to modify these files. The method was implemented in DPERT, a patched version of MCNP5. Using the DPERT patch, we present an integral verification of TSURFER based on 77 heavy water moderated ZED-2 critical experiments. TSURFER is a module of the SCALE code suite and applies first-order perturbation theory to propagate nuclear data uncertainties. The experiments were modeled using the standard MCNP5 code to establish the a priori k_eff calculation biases. TSURFER was used to minimize these biases by adjusting the underlying nuclear data. The proposed cross section alterations were then applied to the experiment models, and the DPERT patch was used to verify TSURFER’s evaluation of the a posteriori k_eff biases. The study confirmed the TSURFER bias reduction prediction, but suggests TSURFER may underestimate the impact of the nuclear data corrections by 1.35 ± 0.05 mk on average

[en] The excitation spectrum of the nucleon provides a stringent constraint on the dynamics and interactions of its internal constituents and therefore probes the mechanism of confinement in the light quark sector. Our detailed knowledge of this excitation spectrum is poor, with many predicted states not yet observed in experiment and many 'established' states having poorly known properties. To address these shortcomings a worldwide effort is currently underway exploiting the latest generation of electron and photon beams in detailed studies of meson photoproduction from nucleon targets. A major contribution to this effort will come from the experimental programme at Jefferson Lab exploiting the frozen spin target (FROST) with the CLAS spectrometer. The status of this project will be presented along with preliminary results and analyses.

[en] We present a preliminary analysis of the photon beam asymmetry observable (Σ) from the photoproduction reaction channel γn → pπ^- in the invariant mass range 1.6 - 2.3 GeV. The measurement was obtained using the near-4π CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1 - 2.3 GeV, incident on a liquid deuterium target. The measurement will provide new data to address the poorly established neutron excitation spectrum and will greatly expand the sparse world data-set both in energy and angle. (authors)

[en] Despite many decades of study the physical origin of ‘dark matter’ (DM) in the Universe remains elusive. In this letter we calculate the properties of a completely new DM candidate—Bose–Einstein condensates formed from a recently discovered bosonic particle in the light-quark sector, the $d^{\ast <!--\; ???\; -->}(2380)$ hexaquark. In this first study, we show stable $d^{\ast <!--\; ???\; -->}(2380)$ Bose–Einstein condensates could form in the primordial early universe, with a production rate sufficiently large that they are a plausible new candidate for DM. Some possible astronomical signatures of such DM are also presented. (letter)

[en] We describe the development, construction and preliminary results obtained with medium-size Multi-Gap Resistive Plate Chambers prototypes designed to detect and localize 511 keV photons for Positron Emission Tomography imaging applications. The devices are intended for in-beam monitoring of the treatment plans throughout deep tumor therapy with hadron beams; emphasis is put on achieving coincidence time resolutions of few hundred ps, in order to exploit optimized reconstruction algorithm and reduce the heavy non-correlated background contributions distinctive of this operation. Using technologies developed for high energy physics experiments, the detectors can be built for covering large areas, thus leading the way to the conception of full-body PET systems at low cost

[en] This paper summarizes calculations of MCNP5 and WIMS-AECL/RFSP compared against measurements in coolant void substitution experiments in the ZED-2 critical facility with CANFLEX R-LEU/RU (Low Enriched Uranium, Recovered Uranium) reference fuels and CANFLEX-LVRF (Low Void Reactivity Fuel) test fuel, and H₂O/air coolants. Both codes are tested for the prediction of the change in reactivity with complete voiding of all fuel channels, and that for a checkerboard voiding pattern. Understanding these phenomena is important for the ACR-1000 R reactor. Comparisons are also made for the prediction of the axial and radial neutron flux distributions, as measured by copper foil activation. The experimental data for these comparisons were obtained from critical mixed lattice / substitution experiments in AECL's ZED-2 critical facility using CANFLEX-LEU/RU and CANFLEX-LVRF fuel in a 24-cm square lattice pitch at 25 degrees C. Substitution analyses were performed to isolate the properties (buckling, bare critical lattice dimensions) of the CANFLEX-LVRF fuel. This data was then used to further test the lattice physics codes. These comparisons establish biases/uncertainties and errors in the calculation of k_eff, coolant void reactivity, checkerboard coolant void reactivity, and flux distributions. Results show small to modest biases in void reactivity and very good agreement for flux distributions. The importance of boundary conditions and the modeling of un-moderated fuel in the critical experiments are demonstrated. This comparison study provides data that supports code validation and gives good confidence in the reactor physics tools used in the design and safety analysis of the ACR-1000 reactor. (authors)

[en] We explore the fundamental limits to which reionization histories can be constrained using only large-scale cosmic microwave background (CMB) anisotropy measurements. The redshift distribution of the fractional ionization x _e(z) affects the angular distribution of CMB polarization. We project constraints on the reionization history of the universe using low-noise full-sky temperature and E-mode measurements of the CMB. We show that the measured TE power spectrum, ${\stackrel{^<!--\; ^\; -->}{C}}_{\mathrm{\ell <!--\; ???\; -->}}^{\mathrm{T}\mathrm{E}}$, has roughly one quarter of the constraining power of ${\stackrel{^<!--\; ^\; -->}{C}}_{\mathrm{\ell <!--\; ???\; -->}}^{\mathrm{E}\mathrm{E}}$ on the reionization optical depth τ, and its addition improves the precision on τ by 20% over using ${\stackrel{^<!--\; ^\; -->}{C}}_{\mathrm{\ell <!--\; ???\; -->}}^{\mathrm{E}\mathrm{E}}$ only. We also use a two-step reionization model with an additional high-redshift step, parameterized by an early ionization fraction $x_e^{min}$, and a late reionization step at z _re. We find that future high signal-to-noise measurements of the multipoles 10 ≤ ℓ < 20 are especially important for breaking the degeneracy between $x_e^{min}$ and z _re. In addition, we show that the uncertainties on these parameters determined from a map with sensitivity 10 μK arcmin are less than 5% larger than the uncertainties in the noiseless case, making this noise level a natural target for future large sky area E-mode measurements.