2,919 research outputs found
Time Resolution Measurements on SiPM for High Energy Physics Experiments
Scintillator detector have been used in a wide range of experiments in different areas: Nuclear and High Energy Physics, Medicine, and Radiation Security among others. It is common to use scintillator counters coupled to Photomultiplier Tubes (PMT) as a read out detectors. Nowadays, there has been a great interest in using the Silicon Photomultipliers (PMSi) as a replacement for PMT's due to their high photon detection efficiency (PDE) and their high single photon time resolution (SPTR). The fast the signal is detected, the whole detection system will be useful to search for new physics. PMSi is also known to have a good compactness, magnetic field resistance and low cost. In our lab we are measuring the time resolution of two different models of PMS in order to build a fast radiation detector system
The interaction of hydrogen with metal alloys
Hydrogen diffusion coefficients were measured for several alloys, and these were determined to be about the same at 25 C for all alloys investigated. The relation of structure, both metallurgical and crystallographic, to the observed hydrogen distribution on charging was investigated, as well as the role of hydride formation in the hydrogen resistance of metal alloys. An attempt was made to correlate the structures and compositions of metal alloys as well as other parameters with the ratios of their notched tensile strengths in hydrogen to that in helium, R(H2/He), which are believed to represent a measure of their hydrogen resistance. Evidence supports the belief that hydrogen permeability and hydrogen resistance are increased by smaller grain sizes for a given alloy composition
Beyond the Plate: Leisure Studies as a Recipe for Food Justice
To address the issues that have been derived from the dominant forces in our food systems, movements such as food justice strive to find solutions through decolonization and addressing barriers to accessing healthy, affordable and culturally representative food. One group of individuals that are heavily involved in, and impacted by, food justice are college students. This study seeks to explore the extent to which college students’ involvement in food justice is shaped by their free time. With this research, I strive to bring in the voices of college students, while also bridging a gap in the field by bringing leisure studies, or free time, into the conversation with food justice. I distributed a survey to a group of students majoring in environmental science and studies, in addition to a range of other fields, to gain perspective on their perceptions on the intersection of free time and food justice, as well as meal-based discussion via a focus group. Through this, I found that college students are both in need of the work that food justice does, such as ensuring affordability, but they generally lack the resources or time to participate in the movement. However, it was also discovered that food justice looks different in each context, in terms of who is carrying out the work, as well as in the issues it is trying to solve; thus, there is ultimately not one way to use one’s free time to participate in it
Temperature dependent orbital degree of freedom in a bilayer manganite by magnetic Compton scattering
We have measured temperature-dependent magnetic Compton profiles (MCPs) from
a single crystal of LaSrMnO. The MCPs, which involved
the scattering of circularly polarized x-rays, are in general related to the
momentum density of all the unpaired spins in the system. Nevertheless, we show
that when the x-ray scattering vector lies along the [110] direction, the
number of magnetic electrons of a specific symmetry, i.e. -electrons of
symmetry, yield a distinct signature in the MCP, allowing us to
monitor substantial changes in the occupancy of the states over
the investigated temperature range of 5-200K. This study indicates that
magnetic Compton scattering can provide a powerful window on the properties of
specific magnetic electrons in complex materials.Comment: 5 pages, 4 figures, to appear in Phys. Rev. Let
Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles
We study the three-dimensional nature of the quantum interface between an
ensemble of cold, trapped atomic spins and a paraxial laser beam, coupled
through a dispersive interaction. To achieve strong entanglement between the
collective atomic spin and the photons, one must match the spatial mode of the
collective radiation of the ensemble with the mode of the laser beam while
minimizing the effects of decoherence due to optical pumping. For ensembles
coupling to a probe field that varies over the extent of the cloud, the set of
atoms that indistinguishably radiates into a desired mode of the field defines
an inhomogeneous spin wave. Strong coupling of a spin wave to the probe mode is
not characterized by a single parameter, the optical density, but by a
collection of different effective atom numbers that characterize the coherence
and decoherence of the system. To model the dynamics of the system, we develop
a full stochastic master equation, including coherent collective scattering
into paraxial modes, decoherence by local inhomogeneous diffuse scattering, and
backaction due to continuous measurement of the light entangled with the spin
waves. This formalism is used to study the squeezing of a spin wave via
continuous quantum nondemolition (QND) measurement. We find that the greatest
squeezing occurs in parameter regimes where spatial inhomogeneities are
significant, far from the limit in which the interface is well approximated by
a one-dimensional, homogeneous model.Comment: 24 pages, 7 figure
MACS: Multi-agent COTR system for Defense Contracting
The field of intelligent multi-agent systems has expanded rapidly in the recent past. Multi-agent architectures and systems are being investigated and continue to develop. To date, little has been accomplished in applying multi-agent systems to the defense acquisition domain. This paper describes the design, development, and related considerations of a multi-agent system in the area of procurement and contracting for the defense acquisition community
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