Crystallographic Oxide Phase Identification of Char Deposits Obtained from Space Shuttle Columbia Window Debris

Analyzing the remains of Space Shuttle Columbia has proven technically beneficial years after the vehicle breakup. This investigation focused on charred deposits on fragments of Columbia overhead windowpanes. Results were unexpected relative to the engineering understanding of material performance in a reentry environment. The TEM analysis demonstrated that the oxides of aluminum and titanium mixed with silicon oxides to preserve a history of thermal conditions to which portions of the vehicle were exposed. The presence of Ti during the beginning of the deposition process, along with the thermodynamic phase precipitation upon cool down, indicate that temperatures well above the Ti melt point were experienced. The stratified observations implied that additional exothermic reaction, expectedly metal combustion of a Ti structure, had to be present for oxide formation. Results are significant for aerospace vehicles where thermal protection system (TPS) breaches cause substructures to be in direct path with the reentry plasma.

Plutonium pit manufacturing unit process separation options for rapid reconstitution, a joint position paper of Lawrence Livemore National Laboratory and Los Alamos National Laboratory

This document addressed technical issues regarding the manufacturing processes involved in making plutonium pits. It addresses acceptable approaches from a technical standpoint as to how the manufacturing processes can be separated and distributed among different manufacturing sites. Site selections, costs, and intra-site transfers are not addressed in this document

Academic freedom in Europe: time for a Magna Charta?

This paper is a preliminary attempt to establish a working definition of academic freedom for the European Union states. The paper details why such a definition is required for the European Union and then examines some of the difficulties of defining academic freedom. By drawing upon experience of the legal difficulties beset by the concept in the USA and building on previous analyses of constitutional and legislative protection for academic freedom, and of legal regulations concerning institutional governance and academic tenure, a working definition of academic freedom is then derived. The resultant definition which, it is suggested, could form the basis for a European Magna Charta Libertatis Academicae, goes beyond traditional discussions of academic freedom by specifying not only the rights inherent in the concept but also its accompanying duties, necessary limitations and safeguards. The paper concludes with proposals for how the definition might be tested and carried forward

Characterization of Deposits on Glass Substrate as a Tool in Failure Analysis: The Orbiter Vehicle Columbia Case Study

In connection with the accident investigation of the space shuttle Columbia, an analysis methodology utilizing well established microscopic and spectroscopic techniques was implemented for evaluating the environment to which the exterior fused silica glass was exposed. Through the implementation of optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and electron diffraction, details emerged regarding the manner in which a charred metallic deposited layer formed on top of the exposed glass. Due to nature of the substrate and the materials deposited, the methodology proved to allow for a more detailed analysis of the vehicle breakup. By contrast, similar analytical methodologies on metallic substrates have proven to be challenging due to strong potential for error resulting from substrate contamination. This information proved to be valuable to not only those involved in investigating the break up of Columbia, but also provides a potential guide for investigating future high altitude and high energy accidents

The Space Shuttle Columbia: A Materials Forensic Analysis

No abstract availabl

Rubidium metal target development for large scale 82Sr production: LA-UR-14-22338

Strontium-82 (t1/2 = 25.5 d) is one of the medical isotopes produced on a large scale at the Isotope Production Facility (IPF) of the Los Alamos National Laboratory (LANL), employing a high intensity 100 MeV proton beam and RbCl targets. A constant increase in the 82Sr demand over the last decade combined with an established thermal limit of molten RbCl salt targets [1,2] has challenged the IPF’s world leading production capacity in recent years and necessitated the consideration of low-melting point (39.3 °C) Rb metal targets. Metal targets are used at other facilities [3–5] and offer obvious production rate advantages due to a higher relative density of Rb target atoms and a higher expected thermal performance of molten metal. One major disadvantage is the known violent reaction of molten Rb with cooling water and the potential for facility damage following a catastrophic target failure. This represents a significant risk, given the high beam intensities used routinely at IPF. In order to assess this risk, a target failure experiment was conducted at the LANL firing site using a mockup target station. Subsequent fabrication, irradiation and processing of two prototype targets showed a target thermal performance consistent with thermal modeling predictions and yields in agreement with predictions based on IAEA recommended cross sections [6]. Target failure test: The target failure test bed (FIG. 1) was constructed to represent a near replica of the IPF target station, incorporating its most important features. One of the most vulnerable components in the assembly is the Inconel beam window (FIG. 2) which forms the only barrier between the target cooling water and the beam line vacuum. The test bed also mimicked relevant IPF operational parameters seeking to simulate the target environment during irradiation, such as typical cooling water flow velocities around the target surfaces. While the aggressive thermal effects of the beam heating could not be simulated directly, heated cooling water (45 °C) ensured that the rubidium target material remained molten during the failure test. A worst case catastrophic target failure event was initiated by uncovering an oversized predrilled pinhole (1 mm Φ) to abruptly expose the molten target material to fast flowing cooling water. Prototype target irradiations: Two prototype Rb metal target containers were fabricated by machining Inconel 625 parts and by EB welding. The target containers were filled with molten Rb metal under an inert argon atmosphere. Follow-ing appropriate QA inspections, the prototype targets were irradiated in the medium energy slot of a standard IPF target stack using beam currents up to 230 µA. After irradiation the targets were transported to the LANL hot cell facili-ty for processing and for 82Sr yield verification. During the target failure test, cooling water conductivity and pressure excursions in the target chamber were continuously monitored and recorded at a rate of 1 kHz. Video footage taken of the beam window and the pinhole area combined with the recorded data indicated an aggressive reaction between the Rb metal and the cooling water, but did not reveal a violent explosion that could seriously damage the beam window. These observations, together with thermal model predictions, provided the necessary confidence to fabricate and fill prototype targets for irradiation at production-scale beam currents. X-ray imaging of filled targets (FIG. 3) shows a need for tighter control over the target fill level. One prototype target was first subjected to lower intensity (< 150 µA) beams before the second was irradiated at production level (230 µA) beams. During irradiation, monitoring of cooling water conductivity indicated no container breach or leak and, as anticipated given the model predictions, the post irradiation target inspection showed no sign of imminent thermal failure (see FIG. 4). Subsequent chemical processing of the targets followed an established procedure that was slightly modified to accommodate the larger target mass. TABLE 1 shows that post chemistry 82Sr yields agree to within 2 % of the in-target production rates expected on the basis of IAEA recommended cross sections. The table also compares 82Sr yields from the Rb metal targets against yields routinely obtained from RbCl targets, showing an increase in yield of almost 50 %

Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data

We present a measurement of neutrino oscillations via atmospheric muon neutrino disappearance with three years of data of the completed IceCube neutrino detector. DeepCore, a region of denser instrumentation, enables the detection and reconstruction of atmospheric muon neutrinos between 10 GeV and 100 GeV, where a strong disappearance signal is expected. The detector volume surrounding DeepCore is used as a veto region to suppress the atmospheric muon background. Neutrino events are selected where the detected Cherenkov photons of the secondary particles minimally scatter, and the neutrino energy and arrival direction are reconstructed. Both variables are used to obtain the neutrino oscillation parameters from the data, with the best fit given by $\Delta m^2_{32}=2.72^{+0.19}_{-0.20}\times 10^{-3}\,\mathrm{eV}^2$ and $\sin^2\theta_{23} = 0.53^{+0.09}_{-0.12}$ (normal mass hierarchy assumed). The results are compatible and comparable in precision to those of dedicated oscillation experiments.Comment: 10 pages, 7 figure

Flavor Ratio of Astrophysical Neutrinos above 35 TeV in IceCube

A diffuse flux of astrophysical neutrinos above $100\,\mathrm{TeV}$ has been observed at the IceCube Neutrino Observatory. Here we extend this analysis to probe the astrophysical flux down to $35\,\mathrm{TeV}$ and analyze its flavor composition by classifying events as showers or tracks. Taking advantage of lower atmospheric backgrounds for shower-like events, we obtain a shower-biased sample containing 129 showers and 8 tracks collected in three years from 2010 to 2013. We demonstrate consistency with the $(f_e:f_{\mu}:f_\tau)_\oplus\approx(1:1:1)_\oplus$ flavor ratio at Earth commonly expected from the averaged oscillations of neutrinos produced by pion decay in distant astrophysical sources. Limits are placed on non-standard flavor compositions that cannot be produced by averaged neutrino oscillations but could arise in exotic physics scenarios. A maximally track-like composition of $(0:1:0)_\oplus$ is excluded at $3.3\sigma$, and a purely shower-like composition of $(1:0:0)_\oplus$ is excluded at $2.3\sigma$.Comment: 8 pages, 3 figures. Submitted to PR

Search for non-relativistic Magnetic Monopoles with IceCube

The IceCube Neutrino Observatory is a large Cherenkov detector instrumenting $1\,\mathrm{km}^3$ of Antarctic ice. The detector can be used to search for signatures of particle physics beyond the Standard Model. Here, we describe the search for non-relativistic, magnetic monopoles as remnants of the GUT (Grand Unified Theory) era shortly after the Big Bang. These monopoles may catalyze the decay of nucleons via the Rubakov-Callan effect with a cross section suggested to be in the range of $10^{-27}\,\mathrm{cm^2}$ to $10^{-21}\,\mathrm{cm^2}$. In IceCube, the Cherenkov light from nucleon decays along the monopole trajectory would produce a characteristic hit pattern. This paper presents the results of an analysis of first data taken from May 2011 until May 2012 with a dedicated slow-particle trigger for DeepCore, a subdetector of IceCube. A second analysis provides better sensitivity for the brightest non-relativistic monopoles using data taken from May 2009 until May 2010. In both analyses no monopole signal was observed. For catalysis cross sections of $10^{-22}\,(10^{-24})\,\mathrm{cm^2}$ the flux of non-relativistic GUT monopoles is constrained up to a level of $\Phi_{90} \le 10^{-18}\,(10^{-17})\,\mathrm{cm^{-2}s^{-1}sr^{-1}}$ at a 90% confidence level, which is three orders of magnitude below the Parker bound. The limits assume a dominant decay of the proton into a positron and a neutral pion. These results improve the current best experimental limits by one to two orders of magnitude, for a wide range of assumed speeds and catalysis cross sections.Comment: 20 pages, 20 figure