269 research outputs found
All Coronal Loops are the Same: Evidence to the Contrary
The 1998 April 20 spectral line data from the Coronal Diagnostics
Spectrometer (CDS) on the {\it Solar and Heliospheric Observatory} (\SOHO)
shows a coronal loop on the solar limb. Our original analysis of these data
showed that the plasma was multi-thermal, both along the length of the loop and
along the line of sight. However, more recent results by other authors indicate
that background subtraction might change these conclusions, so we consider the
effect of background subtraction on our analysis. We show Emission Measure (EM)
Loci plots of three representative pixels: loop apex, upper leg, and lower leg.
Comparisons of the original and background-subtracted intensities show that the
EM Loci are more tightly clustered after background subtraction, but that the
plasma is still not well represented by an isothermal model. Our results taken
together with those of other authors indicate that a variety of temperature
structures may be present within loops.Comment: Accepted for publication in ApJ Letter
Probing the isovector transition strength of the low-lying nuclear excitations induced by inverse kinematics proton scattering
A compact approach based on the folding model is suggested for the
determination of the isoscalar and isovector transition strengths of the
low-lying () excitations induced by inelastic proton
scattering measured with exotic beams. Our analysis of the recently measured
inelastic O+p scattering data at and 43 MeV/nucleon
has given for the first time an accurate estimate of the isoscalar
and isovector deformation parameters (which cannot be determined from
the (p,p') data alone by standard methods) for 2 and excited
states in O. Quite strong isovector mixing was found in the 2
inelastic O+p scattering channel, where the strength of the isovector
form factor (prototype of the Lane potential) corresponds to a
value almost 3 times larger than and a ratio of nuclear transition
matrix elements .Comment: 5 pages, 3 figure
Multiphonon Giant Resonances
A new class of giant resonances in nuclei is discussed, i.e., giant
resonances built on other giant resonances. These resonances are observed with
very large cross sections in relativistic heavy ion collisions. A great
experimental and theoretical effort is underway to understand the reaction
mechanism which leads to the excitation of these states in nuclei, as well as
the better microscopic understanding of their properties, e.g., strength,
energy centroids, widths, and anharmonicities.Comment: Postscript file with text and 11 embedded figure
The Detection of Ionizing Radiation by Plasma Panel Sensors: Cosmic Muons, Ion Beams and Cancer Therapy
The plasma panel sensor is an ionizing photon and particle radiation detector
derived from PDP technology with high gain and nanosecond response.
Experimental results in detecting cosmic ray muons and beta particles from
radioactive sources are described along with applications including high energy
and nuclear physics, homeland security and cancer therapeuticsComment: Presented at SID Symposium, June 201
Plasma Panel Sensors for Particle and Beam Detection
The plasma panel sensor (PPS) is an inherently digital, high gain, novel
variant of micropattern gas detectors inspired by many operational and
fabrication principles common to plasma display panels (PDPs). The PPS is
comprised of a dense array of small, plasma discharge, gas cells within a
hermetically-sealed glass panel, and is assembled from non-reactive,
intrinsically radiation-hard materials such as glass substrates, metal
electrodes and mostly inert gas mixtures. We are developing the technology to
fabricate these devices with very low mass and small thickness, using gas gaps
of at least a few hundred micrometers. Our tests with these devices demonstrate
a spatial resolution of about 1 mm. We intend to make PPS devices with much
smaller cells and the potential for much finer position resolutions. Our PPS
tests also show response times of several nanoseconds. We report here our
results in detecting betas, cosmic-ray muons, and our first proton beam tests.Comment: 2012 IEEE NS
Fusion of radioactive Sn with Ni
Evaporation residue and fission cross sections of radioactive Sn on
Ni were measured near the Coulomb barrier. A large sub-barrier fusion
enhancement was observed. Coupled-channel calculations including inelastic
excitation of the projectile and target, and neutron transfer are in good
agreement with the measured fusion excitation function. When the change in
nuclear size and shift in barrier height are accounted for, there is no extra
fusion enhancement in Sn+Ni with respect to stable Sn+Ni.
A systematic comparison of evaporation residue cross sections for the fusion of
even Sn and Sn with Ni is presented.Comment: 9 pages, 11 figure
Development of a plasma panel radiation detector: recent progress and key issues
A radiation detector based on plasma display panel technology, which is the
principal component of plasma television displays is presented. Plasma Panel
Sensor (PPS) technology is a variant of micropattern gas radiation detectors.
The PPS is conceived as an array of sealed plasma discharge gas cells which can
be used for fast response (O(5ns) per pixel), high spatial resolution detection
(pixel pitch can be less than 100 micrometer) of ionizing and minimum ionizing
particles. The PPS is assembled from non-reactive, intrinsically radiation-hard
materials: glass substrates, metal electrodes and inert gas mixtures. We report
on the PPS development program, including simulations and design and the first
laboratory studies which demonstrate the usage of plasma display panels in
measurements of cosmic ray muons, as well as the expansion of experimental
results on the detection of betas from radioactive sources.Comment: presented at IEEE NSS 2011 (Barcelona
Tomes! Enhancing Community and Embracing Diversity Through Book Arts
This article highlights important connections between the spoken word, handmade paper, cultural memory and natural sustenance -- in books and in artworks. Two projects were brought together for an exhibition, which serves as an innovative response to the call for multiculturalism, inclusion, and equity at an educational institution in one of the most multilingual and multicultural states in the U.S. Any organization which mounts an exhibition runs the risk of assuming they know what visitors want to see, or ought to see, and how they might choose to experience the works displayed. This exhibit is an attempt to subvert that tendency and extend the continuum of authority, offering visitors multiple modes for leaving their mark on the exhibit. Preliminary comments demonstrate how performative and tactile object-based inquiry leads to transformative learning. How do communities interact with and describe materials whose intent is to push what comfortably translates between English and Spanish? How can we collaborate to provide better access to collections that represent their families, communities, or traditions? What sorts of differences are observed between the ways people handle and describe unique objects if they are not instructed first? The exhibit continues to evolve according to community feedback. This article discusses one approach to collaboration as an effective tool for breaking down barriers to traditional authority and hierarchies
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