Atomic oxygen degradation of Intelsat 4-type solar array interconnects: Laboratory investigations

A Hughes 506 type communication satellite belonging to the Intelsat organization was marooned in low Earth orbit on March 14, 1990, following failure of the Titan third stage to separate properly. The satellite, Intelsat VI, was designed for service in geosynchronous orbit and contains several material configurations which are susceptible to attack by atomic oxygen. Analysis showed the silver foil interconnects in the satellite photovoltaic array to be the key materials issue because the silver is exposed directly to the atomic oxygen ram flux. The results are reported of atomic oxygen degradation testing of Intelsat VI type silver foil interconnects both as virgin material and in a configured solar cell element. Test results indicate that more than 80 pct. of the original thickness of silver in the Intelsat VI solar array interconnects should remain after completion of the proposed Space Shuttle rescue and/or reboost mission

High intensity 5 eV O-atom exposure facility for material degradation studies

An atomic oxygen exposure facility was developed for studies of material degradation. The goal of these studies is to provide design criteria and information for the manufacture of long life (20 to 30 years) construction materials for use in low Earth orbit. The studies that are being undertaken will provide: (1) absolute reaction cross sections for the engineering design problems, (2) formulations of reaction mechanisms for use in the selection of suitable existing materials and the design of new more resistant ones, and (3) the calibration of flight hardware (mass spectrometers, etc.) in order to directly relate experiments performed in low Earth orbit to ground based investigations. The facility consists of a CW laser sustained discharge source of O-atoms, an atomic beam formation and diagnostics system, a spinning rotor viscometer, and provision for using the system for calibration of actual flight instruments

Hollow pellet injection for magnetic fusion

Precise delivery of mass to burning plasmas is a problem of growing interest in magnetic fusion. The answers to how much mass is necessary and sufficient can vary depending on parameters such as the type of atoms involved, the type of applications, plasma conditions, mass injector, and injection timing. Motivated by edge localized mode (ELM) control in H-mode plasmas, disruption mitigation and other applications in magnetic fusion, we report progress and new possibilities in mass delivery based on hollow pellets. Here, a hollow pellet refers to a spherical shell mass structure with a hollow core. Based on an empirical model of pellet ablation, coupled with BOUT++ simulations of ELM triggering threshold, hollow pellets are found to be attractive in comparison with solid spheres for ELM control. By using hollow pellets, it is possible to tailor mass delivery to certain regions of edge plasmas while minimizing core contamination and reducing the total amount of mass needed. We also include experimental progress in mass delivery experiments, in-situ diagnostics and hollow pellet fabrication, and emphasize new experimental possibilities for ELM control based on hollow pellets. A related application is the disruption mitigation scheme using powder encapsulated inside hollow shells. Further experiments will also help to resolve known discrepancies between theoretical predictions and experiments in using mass injection for ELM control and lead to better predictive models for ELM stability and triggering.Comment: Manuscript prepared for reviews by {\it Nuclear Fusion}, following the initial presentation in the 27th IAEA FEC, Gandhinagar, India, Oct. 22 - 27, 201

Position-sensitive detection of ultracold neutrons with an imaging camera and its implications to spectroscopy

Position-sensitive detection of ultracold neutrons (UCNs) is demonstrated using an imaging charge-coupled device (CCD) camera. A spatial resolution less than 15 $\mu$m has been achieved, which is equivalent to an UCN energy resolution below 2 pico-electron-volts through the relation $\delta E = m_0g \delta x$. Here, the symbols $\delta E$, $\delta x$, $m_0$ and $g$ are the energy resolution, the spatial resolution, the neutron rest mass and the gravitational acceleration, respectively. A multilayer surface convertor described previously is used to capture UCNs and then emits visible light for CCD imaging. Particle identification and noise rejection are discussed through the use of light intensity profile analysis. This method allows different types of UCN spectroscopy and other applications.Comment: 12 figures, 28 pages, accepted for publication in NIM

Status of the UCNτ experiment

The neutron is the simplest nuclear system that can be used to probe the structure of the weak interaction and search for physics beyond the standard model. Measurements of neutron lifetime and β-decay correlation coefficients with precisions of 0.02% and 0.1%, respectively, would allow for stringent constraints on new physics. The UCNτ experiment uses an asymmetric magneto-gravitational UCN trap with in situ counting of surviving neutrons to measure the neutron lifetime, τ_n = 877.7s (0.7s)_(stat) (+0.4/−0.2s)_(sys). We discuss the recent result from UCNτ, the status of ongoing data collection and analysis, and the path toward a 0.25 s measurement of the neutron lifetime with UCNτ

Measurement of the neutron lifetime using an asymmetric magneto- gravitational trap and in situ detection

The precise value of the mean neutron lifetime, $\tau_n$, plays an important role in nuclear and particle physics and cosmology. It is a key input for predicting the ratio of protons to helium atoms in the primordial universe and is used to search for new physics beyond the Standard Model of particle physics. There is a 3.9 standard deviation discrepancy between $\tau_n$ measured by counting the decay rate of free neutrons in a beam (887.7 $\pm$ 2.2 s) and by counting surviving ultracold neutrons stored for different storage times in a material trap (878.5$\pm$0.8 s). The experiment described here eliminates loss mechanisms present in previous trap experiments by levitating polarized ultracold neutrons above the surface of an asymmetric storage trap using a repulsive magnetic field gradient so that the stored neutrons do not interact with material trap walls and neutrons in quasi-stable orbits rapidly exit the trap. As a result of this approach and the use of a new in situ neutron detector, the lifetime reported here (877.7 $\pm$ 0.7 (stat) +0.4/-0.2 (sys) s) is the first modern measurement of $\tau_n$ that does not require corrections larger than the quoted uncertainties.Comment: 9 pages, 3 figures, 2 table

Implementation of routine outcome measurement in child and adolescent mental health services in the United Kingdom: a critical perspective

The aim of this commentary is to provide an overview of clinical outcome measures that are currently recommended for use in UK Child and Adolescent Mental Health Services (CAMHS), focusing on measures that are applicable across a wide range of conditions with established validity and reliability, or innovative in their design. We also provide an overview of the barriers and drivers to the use of Routine Outcome Measurement (ROM) in clinical practice

A boron-coated CCD camera for direct detection of Ultracold Neutrons (UCN)

A new boron-coated CCD camera is described for direct detection of ultracold neutrons (UCN) through the capture reactions $^{10}$B (n,$\alpha$0$\gamma$)$^7$Li (6%) and $^{10}$B(n,$\alpha$1$\gamma$)$^7$Li (94%). The experiments, which extend earlier works using a boron-coated ZnS:Ag scintillator, are based on direct detections of the neutron-capture byproducts in silicon. The high position resolution, energy resolution and particle ID performance of a scientific CCD allows for observation and identification of all the byproducts $\alpha$, $^7$Li and $\gamma$ (electron recoils). A signal-to-noise improvement on the order of 10$^4$ over the indirect method has been achieved. Sub-pixel position resolution of a few microns is demonstrated. The technology can also be used to build UCN detectors with an area on the order of 1 m$^2$. The combination of micrometer scale spatial resolution, few electrons ionization thresholds and large area paves the way to new research avenues including quantum physics of UCN and high-resolution neutron imaging and spectroscopy.Comment: 10 pages, 8 figure

Immunohistochemical detection of macrophage migration inhibitory factor in fetal and adult bovine epididymis: Release by the apocrine secretion mode?

Originally defined as a lymphokine inhibiting the random migration of macrophages, the macrophage migration inhibitory factor (MIF) is an important mediator of the host response to infection. Beyond its function as a classical cytokine, MIF is currently portrayed as a multifunctional protein with growth-regulating properties present in organ systems beyond immune cells. In previous studies, we detected substantial amounts of MIF in the rat epididymis and epididymal spermatozoa, where it appears to play a role during post-testicular sperm maturation and the acquisition of fertilization ability. To explore its presence in other species not yet examined in this respect, we extended the range of studies to the bull. Using a polyclonal antibody raised against MIF purified from bovine eye lenses, we detected MIF in the epithelium of the adult bovine epididymis with the basal cells representing a prominently stained cell type. A distinct accumulation of MIF at the apical cell pole of the epithelial cells and in membranous vesicles localized in the lumen of the epididynnal duct was obvious. In the fetal bovine epididymis, we also detected MIF in the epithelium, whereas MIF accumulation was evident at the apical cell surface and in apical protrusions. By immuno-electron microscopy of the adult bovine epididymis, we localized MIF in apical protrusions of the epithelial cells and in luminal membrane-bound vesicles that were found in close proximity to sperm cells. Although the precise origin of the MIF-containing vesicles remains to be delineated, our morphological observations support the hypothesis that they become detached from the apical surface of the epididymal epithelial cells. Additionally, an association of MIF with the outer dense fibers of luminal spermatozoa was demonstrated. Data obtained in this study suggest MIF release by an apocrine secretion mode in the bovine epididymis. Furthermore, MIF localized in the basal cells of the epithelium and in the connective tissue could be responsible for regulating the migration of macrophages in order to avoid contact of immune cells with spermatozoa that carry a wide range of potent antigens. Copyright (c) 2006 S. Karger AG, Basel

A multilayer surface detector for ultracold neutrons

A multilayer surface detector for ultracold neutrons (UCNs) is described. The top $^{10}$B layer is exposed to the vacuum chamber and directly captures UCNs. The ZnS:Ag layer beneath the $^{10}$B layer is a few microns thick, which is sufficient to detect the charged particles from the $^{10}$B(n,$\alpha$)$^7$Li neutron-capture reaction, while thin enough so that ample light due to $\alpha$ and $^7$Li escapes for detection by photomultiplier tubes. One-hundred-nm thick $^{10}$B layer gives high UCN detection efficiency, as determined by the mean UCN kinetic energy, detector materials and others. Low background, including negligible sensitivity to ambient neutrons, has also been verified through pulse-shape analysis and comparisons with other existing $^3$He and $^{10}$B detectors. This type of detector has been configured in different ways for UCN flux monitoring, development of UCN guides and neutron lifetime research.Comment: 21 pages, 10 figure