We describe the design and performance of the near-infrared (1.51-1.70 μm), fiber-fed, multi-object (300 fibers), high resolution (R = λ/Δλ ∼ 22,500) spectrograph built for the Apache Point Observatory Galactic Evolution Experiment (APOGEE). APOGEE is a survey of ∼10 5 red giant stars that systematically sampled all Milky Way populations (bulge, disk, and halo) to study the Galaxy's chemical and kinematical history. It was part of the Sloan Digital Sky Survey III (SDSS-III) from 2011 to 2014 using the 2.5 m Sloan Foundation Telescope at Apache Point Observatory, New Mexico. The APOGEE-2 survey is now using the spectrograph as part of SDSS-IV, as well as a second spectrograph, a close copy of the first, operating at the 2.5 m du Pont Telescope at Las Campanas Observatory in Chile. Although several fiber-fed, multi-object, high resolution spectrographs have been built for visual wavelength spectroscopy, the APOGEE spectrograph is one of the first such instruments built for observations in the near-infrared. The instrument's successful development was enabled by several key innovations, including a "gang connector" to allow simultaneous connections of 300 fibers; hermetically sealed feedthroughs to allow fibers to pass through the cryostat wall continuously; the first cryogenically deployed mosaic volume phase holographic grating; and a large refractive camera that includes mono-crystalline silicon and fused silica elements with diameters as large as ∼400 mm. This paper contains a comprehensive description of all aspects of the instrument including the fiber system, optics and opto-mechanics, detector arrays, mechanics and cryogenics, instrument control, calibration system, optical performance and stability, lessons learned, and design changes for the second instrument.
We describe a novel cold neutron spectrometer under development at NIST optimized for wave vector resolved spectroscopy with incident energies between 2.1 meV and 20 meV and energy resolution from 0.05 meV (E i = 2.1 meV) to 3.0 meV (E i = 20 meV). By using a 1428 cm 2 double focusing PG (0 0 2) monochromator close to the National Institute of Standards and Technology (NIST) cold neutron source the instrument provides up to 5 × 10 8 neutrons cm −2 s −1 on a 8 cm 2 sample area. The measured performance is consistent with Monte Carlo simulations. The monochromating system, which includes radial collimators, three filters and a variable beam aperture, offers considerable flexibility in optimizing Q-resolution, energy resolution and intensity. The detector system will consist of an array of 20 channels which combined will subtend a solid angle of 0.2 sr. This is approximately a factor of 40 more than a conventional triple axis spectrometer. Each detector channel contains a vertically focusing double crystal analyzer system (DXAL) actuated by a single stepping motor. We find identical integrated reflectivity at approximately 10% coarser energy resolution for the 130 mosaic double bounce analyzer as compared to a conventional 25 analyzer at the same energy. The vertical focusing of the DXAL allows for smaller detectors for enhanced signal to noise with 8 • vertical acceptance. Options for post sample collimators and filters provide flexibility in the choice of scattered beam energy and wavevector resolution.
ABSTRACT. The FourStar Infrared Camera is a 4 K × 4 K near-infrared (1.0-2.4 μm) imager built for the Magellan 6.5 m Baade Telescope at Las Campanas Observatory, Chile. FourStar has an all-refractive optical system, four HAWAII-2RG detectors, and Teledyne electronics. The pixel scale of 0:159″ pixel À1 produces a 10:8 0 × 10:8 0 field of view. Ten filters are available across the Y , J, H, and K s bands. We present the optical, mechanical, thermal, electronic, and software design choices and their associated engineering implementations. The detector readout electronics, control system, and the automatic data acquisition hardware are also described. Laboratory and onsky performance data are presented. FourStar has excellent image quality, easily meeting the requirement of critically sampling the median seeing disk. The throughput is ≈0:5-0:6 across its wavelength coverage. Some early science results are presented.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ∼1.6−2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.
A study has been conducted of locomotive crashworthiness in a range of collision scenarios to support the efforts of the Locomotive Crashworthiness Working Group of the Federal Railroad Administration's Railroad Safety Advisory Committee (RSAC) to develop locomotive crashworthiness requirements. The RSAC is a government/industry committee including all segments of the rail community, with the purpose of developing solutions to safety regulatory issues. This paper presents the results of a study of the crashworthiness of conventional and modified locomotive designs in five collision scenarios. The five collision scenarios studied are:1. in-line collision of two locomotive-led trains with trailing locomotive overriding leading locomotive 2. in-line collision of two locomotive-led trains with one colliding locomotive overriding the other 3. locomotive grade crossing collision with highway vehicle hauling logs, with principal impact on locomotive window area 4. oblique collision, locomotive with intermodal trailer 5. oblique collision, locomotive with freight car
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