We study the expected performance of the proposed fundamental neutron physics beamline at the upgraded High Flux Isotope Reactor at Oak Ridge National Laboratory. A curved neutron guide transmits the neutrons from the new cold source into a guide hall. A novel feature of the proposed guide is the use of vertical focussing to increase the flux for experiments that require relatively small cross-...

We have analyzed Rossi X-ray timing explorer (RXTE) pointed observations of the outbursts of black hole and neutron star soft X-ray transients in which an initial low/hard state or ‘island’ state, followed by a transition to a softer state, was observed. In three sources, the black hole transient XTE J1550-564, the neutron star transient Aquila X-1 and a quasi-persistent neutron star low mass X...

Neutron-capture elements in low metallicity Galactic halo stars vary widely both in overall contents and detailed abundance patterns. This review discusses recent observational results on the n-capture elements, discussing the implications for early Galactic nucleosynthesis of: (a) the star-to-star " bulk " variations in the n-capture/Fe abundance ratios; (b) the distinct signature of rapid n-c...

Kilohertz quasi-periodic oscillations (kHz QPOs) has been regarded as representing the Keplerian frequency at the inner disk edge in the neutron star X-ray binaries. The so-called “parallel tracks” on the plot of the kHz QPO frequency vs. X-ray flux in neutron star Xray binaries, on the other hand, show the correlation between the kHz QPO frequency and the X-ray flux on time scales from hours t...

We examine the energy-resolved pulse profiles of 51 flux oscillations observed during the decline of thermonuclear X-ray bursts from accreting weakly-magnetized neutron stars with the Rossi X-ray Timing Explorer. We find that the fractional rms amplitudes of the oscillations increase as a function of energy by 0.25% keV to 0.9% keV between 3−20 keV, and are as large as 20% in the 13−20 keV band...

We present a new method for precision measurement of the capture flux polarization of a polychromatic (white), continuous cold neutron beam, polarized by a (3)He spin filter. This method allows an in situ measurement and does not require knowledge of the neutron beam wavelength distribution. We show that a polarimetry precision of 0.1 % is possible.

The protection-system of GEN III+ reactors partially relies on self-powered neutron detectors (SPNDs), in-core devices measuring the neutron flux. The goal of this paper is to estimate the robustness and reliability of those detectors for surveillance purposes, using mathematical models. The results of research might serve as the basis for decision-making regarding future development and amelio...

The energy source powering the X-ray emission from anomalous X-ray pulsars (AXPs) and soft γ-ray repeaters (SGRs) is still uncertain. In one scenario, the presence of an ultramagnetized neutron star, or “magnetar”, with B ≃ 1014 − 1015 G is invoked. To investigate this hypothesis, we have analyzed archival ASCA data for several known AXPs and SGRs, and fitted them with a model in which all or p...

Single event upsets (SEU) have been observed in implantable cardiac defibrillators. The incidence of SEUs is well modeled by upset rate calculations attributable to the secondary cosmic ray neutron flux. The effect of recent interpretations of the shape of the heavy ion cross-section curve on neutron burst generation rate calculations is discussed. The model correlates well with clinical experi...

Neutronics-processing interface parameters have large impacts on the neutron economy and transmutation performance of an aqueousbased Accelerator Transmutation of Waste (ATW) system. A detailed assessment of the interdependence of these blanket neutronic and chemical processing parameters has been performed. Neutronic performance analyses requi’re that neutron transport calculations for the A’T...