Cored Rutherford cables for the GSI fast ramping synchrotron

The new heavy ion synchrotron facility proposed by GSI will have two superconducting magnet rings in the same tunnel, with rigidities of 200 T/spl middot/m and 100 T/spl middot/m. Fast ramp times are needed, which can cause significant problems for the magnets, particularly in the areas of ac loss and field distortion. This paper discusses the 200 T/spl middot/m ring, which will use Cos/spl theta/ magnets based on the RHIC dipole design. We discuss the reasons for choosing Rutherford cable with a resistive core and report loss measurements carried out on cable samples. These measurements are compared with theoretical calculations using measured values of inter-strand resistance. Reasonably good agreement is found, but there are indications of nonuniformity in the adjacent resistance R/sub a/. Using these measured parameters, losses and temperature rise are calculated for a RHIC dipole in the operating cycle of the accelerator. A novel insulation scheme designed to promote efficient cooling is described

Recent and future trends in synthetic greenhouse gas radiative forcing

Atmospheric measurements show that emissions of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons are now the primary drivers of the positive growth in synthetic greenhouse gas (SGHG) radiative forcing. We infer recent SGHG emissions and examine the impact of future emissions scenarios, with a particular focus on proposals to reduce HFC use under the Montreal Protocol. If these proposals are implemented, overall SGHG radiative forcing could peak at around 355 mW m[superscript −2] in 2020, before declining by approximately 26% by 2050, despite continued growth of fully fluorinated greenhouse gas emissions. Compared to “no HFC policy” projections, this amounts to a reduction in radiative forcing of between 50 and 240 mW m[superscript −2] by 2050 or a cumulative emissions saving equivalent to 0.5 to 2.8 years of CO2 emissions at current levels. However, more complete reporting of global HFC emissions is required, as less than half of global emissions are currently accounted for.Natural Environment Research Council (Great Britain) (Advanced Research Fellowship NE/I021365/1)United States. National Aeronautics and Space Administration (Upper Atmospheric Research Program Grant NNX11AF17G)United States. National Oceanic and Atmospheric Administratio

Characterization of uncertainties in atmospheric trace gas inversions using hierarchical Bayesian methods

We present a hierarchical Bayesian method for atmospheric trace gas inversions. This method is used to estimate emissions of trace gases as well as "hyper-parameters" that characterize the probability density functions (PDFs) of the a priori emissions and model-measurement covariances. By exploring the space of "uncertainties in uncertainties", we show that the hierarchical method results in a more complete estimation of emissions and their uncertainties than traditional Bayesian inversions, which rely heavily on expert judgment. We present an analysis that shows the effect of including hyper-parameters, which are themselves informed by the data, and show that this method can serve to reduce the effect of errors in assumptions made about the a priori emissions and model-measurement uncertainties. We then apply this method to the estimation of sulfur hexafluoride (SF6) emissions over 2012 for the regions surrounding four Advanced Global Atmospheric Gases Experiment (AGAGE) stations. We find that improper accounting of model representation uncertainties, in particular, can lead to the derivation of emissions and associated uncertainties that are unrealistic and show that those derived using the hierarchical method are likely to be more representative of the true uncertainties in the system. We demonstrate through this SF6 case study that this method is less sensitive to outliers in the data and to subjective assumptions about a priori emissions and model-measurement uncertainties than traditional methods

An Overview of the 2014 ALMA Long Baseline Campaign

A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from September to late November 2014, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy.Comment: 11 pages, 7 figures, 2 tables; accepted for publication in the Astrophysical Journal Letters; this version with small changes to affiliation

The hidden heart of the luminous infrared galaxy IC 860 I. A molecular inflow feeding opaque, extreme nuclear activity

High-resolution (0.​​″03–0.​​″09 (9–26 pc)) ALMA (100–350 GHz (λ3 to 0.8 mm)) and (0.​​″04 (11 pc)) VLA 45 GHz measurements have been used to image continuum and spectral line emission from the inner (100 pc) region of the nearby infrared luminous galaxy IC 860. We detect compact (r ∼ 10 pc), luminous, 3 to 0.8 mm continuum emission in the core of IC 860, with brightness temperatures TB >  160 K. The 45 GHz continuum is equally compact but significantly fainter in flux. We suggest that the 3 to 0.8 mm continuum emerges from hot dust with radius r ∼ 8 pc and temperature Td ∼ 280 K, and that it is opaque at millimetre wavelengths, implying a very large H2 column density N(H2)≳1026 cm−2. Vibrationally excited lines of HCN ν2 = 1f J = 4 − 3 and 3–2 (HCN-VIB) are seen in emission and spatially resolved on scales of 40–50 pc. The line-to-continuum ratio drops towards the inner r = 4 pc, resulting in a ring-like morphology. This may be due to high opacities and matching HCN-VIB excitation- and continuum temperatures. The HCN-VIB emission reveals a north–south nuclear velocity gradient with projected rotation velocities of ν = 100 km s−1 at r = 10 pc. The brightest emission is oriented perpendicular to the velocity gradient, with a peak HCN-VIB 3–2 TB of 115 K (above the continuum). Vibrational ground-state lines of HCN 3–2 and 4–3, HC15N 4–3, HCO+ 3–2 and 4–3, and CS 7–6 show complex line absorption and emission features towards the dusty nucleus. Redshifted, reversed P-Cygni profiles are seen for HCN and HCO+ consistent with gas inflow with νin ≲ 50 km s−1. Foreground absorption structures outline the flow, and can be traced from the north-east into the nucleus. In contrast, CS 7–6 has blueshifted line profiles with line wings extending out to −180 km s−1. We suggest that a dense and slow outflow is hidden behind a foreground layer of obscuring, inflowing gas. The centre of IC 860 is in a phase of rapid evolution where an inflow is building up a massive nuclear column density of gas and dust that feeds star formation and/or AGN activity. The slow, dense outflow may be signaling the onset of feedback. The inner, r = 10 pc, IR luminosity may be powered by an AGN or a compact starburst, which then would likely require a top-heavy initial mass function

The 2014 ALMA Long Baseline Campaign: An Overview

A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from September to late November 2014, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy