Search

Associated Particle Imaging (API) is a nuclear technique that allows for the nondestructive determination of 3D isotopic distributions. The technique is based on the detection of the alpha particles associated with the neutron emitted in the deuteriumtritium (DT) fusion reaction, which provides information regarding the direction and time of the emitted 14 MeV neutron. Inelastic neutron scattering leads to characteristic gamma-ray emission from certain isotopes, for example 12C, that can be correlated with the neutron interaction location. An API system consisting of a sealed-type neutron generator, gamma detectors, and a position-sensitive alpha detector is under development for the nondestructive quantification of carbon distribution in soils. This paper describes the design of the alpha detector, detector response simulations, and first experimental results. The alpha detector consists of an Yttrium Aluminum Perovskite (YAP) scintillator mounted on the inside of a neutron generator tube. The scintillation light propagates through a sapphire window to a position-sensitive photomultiplier tube mounted on the outside. The 16 × 16 output signals are connected through a resistive network for a 4-corner readout. The four readout channels are amplified, filtered, and then digitized for the calculation of the alpha interaction in the detector. First test results demonstrate that an excellent alpha position resolution, better than the 1mm FWHM required by the application, can be achieved with this detector design.

The database at http://www.radiopurity.org is the world's largest public database of material radio-purity mea-surements. These measurements are used by members of the low-background physics community to build experiments that search for neutrinos, neutrinoless double-beta decay, WIMP dark matter, and other exciting physics. This paper summarizes the current status and the future plan of this database.

The Majorana Collaboration is searching for the neutrinoless double-beta decay of the nucleus 76Ge. The Majorana Demonstrator is an array of germanium detectors deployed with the aim of implementing background reduction techniques suitable for a tonne scale 76Ge-based search (the LEGEND collaboration). In the Demonstrator, germanium detectors operate in an ultra-pure vacuum cryostat at 80 K. One special challenge of an ultra-pure environment is to develop reliable cables, connectors, and electronics that do not significantly contribute to the radioactive background of the experiment. This paper highlights the experimental requirements and how these requirements were met for the Majorana Demonstrator, including plans to upgrade the wiring for higher reliability in the summer of 2018. Also described are requirements for LEGEND R&D efforts underway to meet these additional requirements.

Time-resolved experimental techniques are increasingly abundant at storage ring facilities. Recent developments in accelerator technology and beamline instrumentation allow for simultaneous operation of high-intensity and timing-based experiments. The MAX IV facility is a state-of-the-art synchrotron light source in Lund, Sweden, that will come into operation in 2016. As many storage ring facilities are pursuing upgrade programs employing strong-focusing multibend achromats and passive harmonic cavities (HCs) in high-current operation, it is of broad interest to study the accelerator and instrumentation developments required to enable timing-based experiments at such machines. In particular, the use of hybrid filling modes combined with pulse picking by resonant excitation or pseudo single bunch has shown promising results. These methods can be combined with novel beamline instrumentation, such as choppers and instrument gating. In this paper we discuss how these techniques can be implemented and employed at MAX IV.

The maximum entropy principle is a powerful tool for solving underdeterminedinverse problems. This paper considers the problem of discretizing a continuousdistribution, which arises in various applied fields. We obtain theapproximating distribution by minimizing the Kullback-Leibler information(relative entropy) of the unknown discrete distribution relative to an initialdiscretization based on a quadrature formula subject to some momentconstraints. We study the theoretical error bound and the convergence of thisapproximation method as the number of discrete points increases. We prove that(i) the theoretical error bound of the approximate expectation of any boundedcontinuous function has at most the same order as the quadrature formula westart with, and (ii) the approximate discrete distribution weakly converges tothe given continuous distribution. Moreover, we present some numerical examplesthat show the advantage of the method and apply to numerically solving anoptimal portfolio problem.

The Texas Symposia on Relativistic Astrophysics had their origins in a couple of astounding scientific discoveries and a demographic accident. A sequence of additional discoveries over the next 15 or so years (pulsars, X-ray binaries, the microwave background, gamma ray bursts....) perpetuated the series, while the inventory of topics thought appropriate for discussion first expanded and then contracted down to a now fairly rigid set, which is easily discerned from the titles of the rest of the papers in these proceedings, while the past inventory has included complex molecules, large telescopes, and at least a few planets. We explore here portions of what happened from 1st Texas in Dallas in December 1963 to the 25th gathering in Heidelberg in 2010, including the parade of "hot" topics, some demographic and scientometric developments, and a few probably authentic anecdotes. Changes in the sources of funding, nationalities of speakers and participants, and gender balance reflect (sometimes with considerable time delay) the larger landscape of science over the years. © 2011 American Institute of Physics.

This paper sketches a careful analysis of an exceptional classroom event where students develop, without explicit instruction, a model equivalent to Newton's thermal law as a composition of intuitive knowledge elements. Lessons about how social (cultural, discursive, situated, etc.) and cognitive perspectives may interact are put forward. © American Institute of Physics.

The 24 years between the announcement of "gamma-ray bursts of cosmic origin" (1973) and the unambiguously cosmological 970228 seemed very long to the generation that lived through them. For a good many astronomical phenomena, however, the interval between the recognition of a puzzle and convergence of the community on a solution was even longer. Examples include periodic variable stars and coronal lines from the sun. In other cases, the right idea has appeared very soon after discovery, pulsars and quasars, for instance. Sometimes, on the other hand, the theorists are out in front with an explanation in advance of the discovery. This is called a prediction, and some have come very far in advance (heliocentric parallax surely holds the record), others only a few years (superluminal motion in quasars, for example). The talk and this paper explore a few examples of each class as a framework for the much-told GRB story. © 2006 American Institute of Physics.