439,935 research outputs found
Scaler mode of the Auger Observatory and Sunspots
Recent data from the Auger Observatory on low energy secondary cosmic ray
particles are analyzed to study temporal correlations together with data on the
daily sunspot numbers and neutron monitor data. Standard spectral analysis
demonstrates that the available data shows 1/f^{\beta} fluctuations with
{\beta} approximately 1 in the low frequency range. All data behave like
Brownian fluctuations in the high frequency range. The existence of long-range
correlations in the data was confirmed by detrended fluctuation analysis. The
real data confirmed the correlation between the scaling exponent of the
detrended analysis and the exponent of the spectral analysis.Comment: 20 pages, 6 figures, to be published in Astrophysical Journal
Supplement Serie
Society of Physics Students
This report summarizes progress on the development of a neutron source from an existing commercial product. The targeted tabletop device uses a pyroelectric crystal to create an electric field that accelerates deuterium ions towards a deuterated target to produce neutrons via fusion. A pyroelectric X-ray generator was characterized and its performance successfully compared with the manufacturer's specifications. A second special "opened " device was obtained from the vendor. A vacuum chamber in which to operate this device in a partial vacuum (and then later with deuterated gas) has been designed and is currently being fabricated. The project will continue next semester with the completed vacuum chamber and the conversion of the pyroelectric X-ray generator to a pyrofusion neutron generator. The neutrons will be characterized and used to further study particle interactions by Indiana University undergraduate students. Review of Project Pyroelectricity is the ability of certain materials to generate an electrical potential when they are heated or cooled. A research paper [1] was published in Nature in mid-2005 about an experiment that used a pyroelectric crystal to achieve nuclear fusion. Pyroelectric fusion is the process by which a pyroelectric crystal in a vacuum is cooled down and then slowly heated. Du
Neutron Shielding Optimization Studies
The IsoDAR sterile-neutrino search calls for a high neutron flux from a 60 MeV proton beam striking a beryllium target, that flood a sleeve of highly-enriched 7Li, the beta-decay of the resulting 8Li giving the desired neutrinos for the veryshort-baseline experiment. The target is placed very close to an existing large neutrino detector; all such existing or planned detectors are deep underground, in low-background environments. It is necessary to design a shielding enclosure to prevent neutrons from causing unacceptable activation of the environment. GEANT4 is being used to study neutron attenuation, and optimising the layers of shielding material to minimize thickness. Materials being studied include iron and two new types of concrete developed by Jefferson Laboratory, one very light with shredded plastic aggregate, the other with high quantities of boron. Initial studies indicate that a total shielding thickness of 1.5 meters produces the required attenuation factor, further studies may allow decrease in thickness. Minimising it will reduce the amount of cavity excavation needed to house the target system in confined underground spaces
Neutron-Neutron Fusion
The neutron-neutron fusion process, , at very low neutron
energies is studied in the framework of pionless effective field theory that
incorporates dibaryon fields. The cross section and electron energy spectrum
for this process are calculated up to next-to-leading order. We include the
radiative corrections of calculated for the one-body
transition amplitude. The precision of our theoretical estimates is found to be
governed essentially by the accuracy with which the empirical values of the
neutron-neutron scattering length and effective range are currently known. Also
discussed is the precision of theoretical estimates of the transition rates of
related electroweak processes in few-nucleon systems.Comment: 14 pages, 4 figures, minor correction, accepted for publication in
Phys. Lett.
Neutron rich nuclei and neutron stars
The PREX experiment at Jefferson Laboratory measures the neutron radius of
208Pb with parity violating electron scattering in a way that is free from most
strong interaction uncertainties. The 208Pb radius has important implications
for neutron rich matter and the structure of neutron stars. We present first
PREX results, describe future plans, and discuss a follow on measurement of the
neutron radius of 48Ca. We review radio and X-ray observations of neutron star
masses and radii. These constrain the equation of state (pressure versus
density) of neutron rich matter. We present a new energy functional that is
simultaneously fit to both nuclear and neutron star properties. In this
approach, neutron star masses and radii constrain the energy of neutron matter.
This avoids having to rely on model dependent microscopic calculations of
neutron matter. The functional is then used to predict the location of the drip
lines and the properties of very neutron rich heavy nuclei.Comment: 8 pages, 4 figures, proceedings of International Conference on
Fission and Neutron Rich Nuclei 5, Sanibel, F
An improved method for estimating the neutron background in measurements of neutron capture reactions
The relation between the neutron background in neutron capture measurements
and the neutron sensitivity related to the experimental setup is examined. It
is pointed out that a proper estimate of the neutron background may only be
obtained by means of dedicated simulations taking into account the full
framework of the neutron-induced reactions and their complete temporal
evolution. No other presently available method seems to provide reliable
results, in particular under the capture resonances. An improved neutron
background estimation technique is proposed, the main improvement regarding the
treatment of the neutron sensitivity, taking into account the temporal
evolution of the neutron-induced reactions. The technique is complemented by an
advanced data analysis procedure based on relativistic kinematics of neutron
scattering. The analysis procedure allows for the calculation of the neutron
background in capture measurements, without requiring the time-consuming
simulations to be adapted to each particular sample. A suggestion is made on
how to improve the neutron background estimates if neutron background
simulations are not available.Comment: 11 pages, 9 figure
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