The Dark Energy Camera is a new imager with a 2.2-degree diameter field of view mounted at the prime focus of the Victor M. Blanco 4-meter telescope on Cerro Tololo near La Serena, Chile. The camera was designed and constructed by the Dark Energy Survey Collaboration, and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it. The camera consists of a five element optical corrector, seven filters, a shutter with a 60 cm aperture, and a CCD focal plane of 250 micron thick fully-depleted CCDs cooled inside a vacuum Dewar. The 570 Mpixel focal plane comprises 62 2kx4k CCDs for imaging and 12 2kx2k CCDs for guiding and focus. The CCDs have 15 microns x15 microns pixels with a plate scale of 0.263 arc sec per pixel. A hexapod system provides state-of-the-art focus and alignment capability. The camera is read out in 20 seconds with 6-9 electrons readout noise. This paper provides a technical description of the camera's engineering, construction, installation, and current status.

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The dark energy camera

We present results from the JINA REACLIB project, an ongoing effort to maintain a current and accurate library of thermonuclear reaction rates for astrophysical applications. Ongoing updates are transparently documented and version tracked, and any set of rates is publicly available and can be downloaded via a Web interface at http://groups.nscl.msu.edu/jina/reaclib/db/. We discuss here our library V1.0, a snapshot of recommended rates for stable and explosive hydrogen and helium burning. We show that the updated reaction rates lead to modest but significant changes in full network, one-dimensional X-ray burst model calculations, compared with calculations with previously used reaction rate sets. The late time behavior of X-ray burst light curves shows significant changes, suggesting that the previously found small discrepancies between model calculations and observations may be solved with a better understanding of the nuclear input. Our X-ray burst model calculations are intended to serve as a benchmark for future model comparisons and sensitivity studies, as the complete underlying nuclear physics is fully documented and publicly available.

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The jina reaclib database: its recent updates and impact on type-i x-ray bursts

.The South Pole Telescope (SPT) is a 10 m diameter, wide-field, offset Gregorian telescope with a 966 pixel, multicolor, millimeter-wave, bolometer camera. It is located at the Amundsen-Scott South Pole station in Antarctica. The design of the SPT emphasizes careful control of spillover and scattering, to minimize noise and false signals due to ground pickup. The key initial project is a large-area survey at wavelengths of 3, 2, and 1.3 mm, to detect clusters of galaxies via the Sunyaev-Zel’dovich effect and to measure the small-scale angular power spectrum of the cosmic microwave background (CMB). The data will be used to characterize the primordial matter power spectrum and to place constraints on the equation of state of dark energy. A second-generation camera will measure the polarization of the CMB, potentially leading to constraints on the neutrino mass and the energy scale of inflation.

The 10 Meter South Pole Telescope

The Quasicontinuum (QC) Method, originally conceived and developed by Tadmor, Ortiz and Phillips [1] in 1996, has since seen a great deal of development and application by a number of researchers The idea of the method is a relatively simple one With the goal of modeling an atomistic system without explicitly treating every atom in the problem, the QC provides a framework whereby degrees of freedom are judiciously eliminated and force/energy calculations are expedited This is combined with adaptive model refinement to ensure that full atomistic detail is retained in regions of the problem where it is required while continuum assumptions reduce the computational demand elsewhere This article provides a review of the method, from its original motivations and formulation to recent improvements and developments A summary of the important mechanics of materials results that have been obtained using the QC approach is presented Finally, several related modeling techniques from the literature are briefly discussed As an accompaniment to this paper, a website designed to serve as a clearinghouse for information on the QC method has been established at wwwqcmethodcom The site includes information on QC research, links to researchers, downloadable QC code and documentation

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The Quasicontinuum Method: Overview, applications and current directions

The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation gamma-ray spectrometer. AGATA is based on the technique of gamma-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a gamma ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of gamma-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector-response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer.

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AGATA - Advanced GAmma Tracking Array

Nuclear Instruments and Methods in Physics Research. Section B; Microstructural Characterization of Semi-Interpenetrating Polymer Networks by Positron Lifetime Spectroscopy

The laminate structure comprises a liquid crystal polymer substrate attached to a test surface of an article. A light absorbing coating is applied to the substrate and is thin enough to permit bonding steric interaction between the liquid crystal polymer substrate and an overlying liquid crystal monomer thin film. Light is directed through and reflected by the liquid crystal monomer thin film and unreflected light is absorbed by the underlying coating. The wavelength of the reflected light is indicative of the shear stress experienced by the test surface.

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Method of determining shear stress employing a monomer-polymer laminate structure

An anemometer utilizing a radionuclide counting technique for measuring both the velocity and the direction of wind. A pendulum 12 consisting of a wire 13 and a ball 14 with a source of radiation 15 on the lower surface of the ball is positioned by the wind. Detectors 16, 17 and 18 are located in a plane perpendicular to pendulum 13 (no wind). The detectors are located on the circumference of a circle and are equidistant from each other as well as the undisturbed (no wind) source ball position. The ratio of the outputs of detectors 16 and 17, and the ratio of the outputs of detectors 17 and 18 are applied to a processor 23 to select from the data stored in the processor the wind velocity V and the wind direction φ. In a second embodiment of the invention (FIG. 10) the pendulum consists of a wire 27, a heavy ball 24, a string 28 and a lighter ball 25 with radiation sources on the lower surfaces of both balls.

Radionuculide counting technique for measuring wind velocity and direction

A low energy positron flux generator using well‐annealed polycrystalline moderators and a Na22 positron source has been developed for microstructural characterization of thin polymer films. A 200 μc Na22 source, deposited on a thin (2.54 μm) aluminized mylar film, is sandwiched between two 0.0127 cm×2.54 cm×2.54 cm tungsten strips. Two identical test polymer films, whose thicknesses may range from 0.001 to 0.01 cm, insulate the two tungsten moderator strips from the aluminized source film. A potential difference of 10–100 volts, depending on the test film thickness, is applied between the tungsten strips and the aluminized source film. Thermalized positrons diffusing out of the moderator strips are attracted to, or repelled from, the source foil depending on the polarity of the potential difference between the moderator strips and the source foil. Thus, more positrons are expected to stop/annihilate in the test films when the source is at a negative potential than when it is at a positive potential. The d...

Jag J. Singh

Papers

Nuclear Instruments and Methods in Physics Research. Section B; Microstructural Characterization of Semi-Interpenetrating Polymer Networks by Positron Lifetime Spectroscopy

Method of determining shear stress employing a monomer-polymer laminate structure

Radionuculide counting technique for measuring wind velocity and direction

A low energy positron flux generator for microstructural characterization of thin polymer films

Shear sensitive monomer-polymer laminate structure and method of using same