3,626 research outputs found
Information-Control Software for Handling Serial Devices in an EPICS Environment
Each accelerator control system has a variety of measurement devices. One of
the most common types of instrument interfaces used for their control is a
serial (RS-232) bus. It is inexpensive and adequate for relatively simple
measurement and control devices such as switchers, amplifiers, voltmeters, and
steppermotors. Since the RS-232 specification is very broad and does not
require uniformity above the basic communication protocol level, one of the
major problems associated with the use of RS-232 is that the command protocol
for each device is unique. This makes it difficult to design generic drivers
for RS-232 and also hampers efforts to design generic troubleshooting methods.
This paper presents software developed independently at three other labs and
integrated into a single system at Jefferson Lab to handle serial devices in a
generic manner. The software is based on the EPICS toolkit and uses a 3-tier
architecture including a common serial driver at the bottom, a top-level
protocol to specify individual device commands in a generic manner, and a
mid-level of software to "glue" the two together.Comment: 3 pages, paper presented at Conference ICALEPCS-2001, San Jose, CA,
November, 200
A Relational Database Model for Managing Accelerator Control System Software At Jefferson Lab
The operations software group at the Thomas Jefferson National Accelerator
Facility faces a number of challenges common to facilities managing a large
body of software developed in-house. Developers include members of the software
group, operators, hardware engineers and accelerator physicists. One management
problem has been ensuring that all software has an identified maintainer who is
still working at the lab. In some cases, locating source code for 'orphaned'
software has also proven to be difficult. Other challenges include enforcing
minimal standards for versioning and documentation, segregating test software
from operational software, encouraging better code reuse, consolidating
input/output file storage and management, and tracking software dependencies.
This paper will describe a relational database model for tracking the
information necessary to solve the problems above. The instantiation of that
database model provides the foundation for various productivity- and
consistency- enhancing tools for automated (or at least assisted) building,
versioning, documenting and installation of software.Comment: ICALEPCS, 2001 PSN#WEAP07
The impact of quark masses on pQCD thermodynamics
We present results for several thermodynamic quantities within the
next-to-leading order calculation of the thermodynamic potential in
perturbative QCD at finite temperature and chemical potential including
non-vanishing quark masses. These results are compared to lattice data and to
higher-order optimized perturbative calculations to investigate the trend
brought about by mass corrections.Comment: V2: Major modifications; 12 pages, 13 figure
NORSEX 1979 microwave remote sensing data report
Airborne microwave remote sensing measurements obtained by NASA Langley Research Center in support of the 1979 Norwegian Remote Sensing Experiment (NORSEX) are summarized. The objectives of NORSEX were to investigate the capabilities of an active/passive microwave system to measure ice concentration and type in the vicinity of the marginal ice zone near Svalbard, Norway and to apply microwave techniques to the investigation of a thermal oceanic front near Bear Island, Norway. The instruments used during NORSEX include the stepped frequency microwave radiometer, airborne microwave scatterometer, precision radiation thermometer and metric aerial photography. The data are inventoried, summarized, and presented in a user-friendly format. Data summaries are presented as time-history plots which indicate when and where data were obtained as well as the sensor configuration. All data are available on nine-track computer tapes in card-image format upon request to the NASA Langley Technical Library
Thermodynamics of (2+1)-flavor strongly interacting matter at nonzero isospin
We investigate the phase structure of strongly interacting matter at
non-vanishing isospin before the onset of pion condensation in the framework of
the unquenched Polyakov-Quark-Meson model with 2+1 quark flavors. We show
results for the order parameters and all relevant thermodynamic quantities. In
particular, we obtain a moderate change of the pressure with isospin at
vanishing baryon chemical potential, whereas the chiral condensate decreases
more appreciably. We compare the effective model to recent lattice data for the
decrease of the pseudo-critical temperature with the isospin chemical
potential. We also demonstrate the major role played by the value of the pion
mass in the curvature of the transition line, and the need for lattice results
with a physical pion mass. Limitations of the model at nonzero chemical
potential are also discussed.Comment: 8 pages, 4 figures; version published in Phys. Lett.
A search for inverse magnetic catalysis in thermal quark-meson models
We explore the parameter space of the two-flavor thermal quark-meson model
and its Polyakov loop-extended version under the influence of a constant
external magnetic field . We investigate the behavior of the pseudo critical
temperature for chiral symmetry breaking taking into account the likely
dependence of two parameters on the magnetic field: the Yukawa quark-meson
coupling and the parameter of the Polyakov loop potential. Under the
constraints that magnetic catalysis is realized at zero temperature and the
chiral transition at is a crossover, we find that the quark-meson model
leads to thermal magnetic catalysis for the whole allowed parameter space, in
contrast to the present picture stemming from lattice QCD.Comment: 8 pages, 5figure
New Class of Compact Stars at High Density
We discuss the equation of state for cold, dense quark matter in perturbation
theory, and how it might match onto that of hadronic matter. Certain choices of
the renormalization scale correspond to a strongly first order chiral
transition, and may generate a new class of small and very dense quark stars.
The results for the mass-radius relation are compatible with the recent
determination of the mass and the radius of an isolated neutron star by Pons et
al.Comment: Latex, 7 pages, 4 figures. Presented at the International Conference
on Statistical QCD, Bielefeld, Germany, 26-30 August 2001. Requires
espcrc1.st
Temporal and Spatial Turbulent Spectra of MHD Plasma and an Observation of Variance Anisotropy
The nature of MHD turbulence is analyzed through both temporal and spatial
magnetic fluctuation spectra. A magnetically turbulent plasma is produced in
the MHD wind-tunnel configuration of the Swarthmore Spheromak Experiment (SSX).
The power of magnetic fluctuations is projected into directions perpendicular
and parallel to a local mean field; the ratio of these quantities shows the
presence of variance anisotropy which varies as a function of frequency.
Comparison amongst magnetic, velocity, and density spectra are also made,
demonstrating that the energy of the turbulence observed is primarily seeded by
magnetic fields created during plasma production. Direct spatial spectra are
constructed using multi-channel diagnostics and are used to compare to
frequency spectra converted to spatial scales using the Taylor Hypothesis.
Evidence for the observation of dissipation due to ion inertial length scale
physics is also discussed as well as the role laboratory experiment can play in
understanding turbulence typically studied in space settings such as the solar
wind. Finally, all turbulence results are shown to compare fairly well to a
Hall-MHD simulation of the experiment.Comment: 17 pages, 17 figures, Submitted to Astrophysical Journa
Hyperons and massive neutron stars: the role of hyperon potentials
The constituents of cold dense matter are still far from being understood.
However, neutron star observations such as the recently observed pulsar PSR
J1614-2230 with a mass of 1.97+/-0.04 M_solar help to considerably constrain
the hadronic equation of state (EoS). We systematically investigate the
influence of the hyperon potentials on the stiffness of the EoS. We find that
they have but little influence on the maximum mass compared to the inclusion of
an additional vector meson mediating repulsive interaction amongst hyperons.
The new mass limit can only be reached with this additional meson regardless of
the hyperon potentials. Further, we investigate the impact of the nuclear
compression modulus and the effective mass of the nucleon at saturation density
on the high density regime of the EoS. We show that the maximum mass of purely
nucleonic stars is very sensitive to the effective nucleon mass but only very
little to the compression modulus.Comment: 24 pages, 8 figure
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