307 research outputs found
Exact aymptotic expansions for the thermodynamics of hydrogen gas in the Saha regime
We consider the hydrogen quantum plasma in the Saha regime, where it almost
reduces to a partially ionized atomic gas. We briefly review the construction
of systematic expansions of thermodynamical functions beyond Saha theory, which
describes an ideal mixture of ionized protons, ionized electrons and hydrogen
atoms in their ground-state. Thanks to the existence of rigorous results, we
first identify the simultaneous low-temperature and low-density limit in which
Saha theory becomes asymptotically exact. Then, we argue that the screened
cluster representation is well suited for calculating corrections, since that
formalism accounts for all screening and recombination phenomena at work in a
more tractable way than other many-body methods. We sketch the corresponding
diagrammatical analysis, which leads to an exact asymptotic expansion for the
equation of state. That scaled low-temperature expansion improves the
analytical knowledge of the phase diagram. It also provides reliable numerical
values over a rather wide range of temperatures and densities, as confirmed by
comparisons to quantum Monte Carlo data.Comment: 10 page
Equation of state SAHA-S meets stellar evolution code CESAM2k
We present an example of an interpolation code of the SAHA-S equation of
state that has been adapted for use in the stellar evolution code CESAM2k. The
aim is to provide the necessary data and numerical procedures for its
implementation in a stellar code. A technical problem is the discrepancy
between the sets of thermodynamic quantities provided by the SAHA-S equation of
state and those necessary in the CESAM2k computations. Moreover, the
independent variables in a practical equation of state (like SAHA-S) are
temperature and density, whereas for modelling calculations the variables
temperature and pressure are preferable. Specifically for the CESAM2k code,
some additional quantities and their derivatives must be provided. To provide
the bridge between the equation of state and stellar modelling, we prepare
auxiliary tables of the quantities that are demanded in CESAM2k. Then we use
cubic spline interpolation to provide both smoothness and a good approximation
of the necessary derivatives. Using the B-form of spline representation
provides us with an efficient algorithm for three-dimensional interpolation.
The table of B-spline coefficients provided can be directly used during stellar
model calculations together with the module of cubic spline interpolation. This
implementation of the SAHA-S equation of state in the CESAM2k stellar structure
and evolution code has been tested on a solar model evolved to the present. A
comparison with other equations of state is briefly discussed. The choice of a
regular net of mesh points for specific primary quantities in the SAHA-S
equation of state, together with accurate and consistently smooth tabulated
values, provides an effective algorithm of interpolation in modelling
calculations. The proposed module of interpolation procedures can be easily
adopted in other evolution codes.Comment: 8 pages, 5 figure
Identity of electrons and ionization equilibrium
It is perhaps appropriate that, in a year marking the 90th anniversary of
Meghnad Saha seminal paper (1920), new developments should call fresh attention
to the problem of ionization equilibrium in gases. Ionization equilibrium is
considered in the simplest "physical" model for an electronic subsystem of
matter in a rarefied state, consisting of one localized electronic state in
each nucleus and delocalized electronic states considered as free ones. It is
shown that, despite the qualitative agreement, there is a significant
quantitative difference from the results of applying the Saha formula to the
degree of ionization. This is caused by the fact that the Saha formula
corresponds to the "chemical" model of matter.Comment: 9 pages, 2 figure
DANSSino: a pilot version of the DANSS neutrino detector
DANSSino is a reduced pilot version of a solid-state detector of reactor
antineutrinos (to be created within the DANSS project and installed under the
industrial 3 GW(th) reactor of the Kalinin Nuclear Power Plant -- KNPP).
Numerous tests performed at a distance of 11 m from the reactor core
demonstrate operability of the chosen design and reveal the main sources of the
background. In spite of its small size (20x20x100 ccm), the pilot detector
turned out to be quite sensitive to reactor antineutrinos, detecting about 70
IBD events per day with the signal-to-background ratio about unity.Comment: 16 pages, 11 figures, 3 tables. arXiv admin note: substantial text
overlap with arXiv:1304.369
Search for sterile neutrinos at the DANSS experiment
DANSS is a highly segmented 1~m plastic scintillator detector. Its 2500
one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS
detector is placed under an industrial 3.1~ reactor of the
Kalinin Nuclear Power Plant 350~km NW from Moscow. The distance to the core is
varied on-line from 10.7~m to 12.7~m. The reactor building provides about 50~m
water-equivalent shielding against the cosmic background. DANSS detects almost
5000 per day at the closest position with the cosmic
background less than 3. The inverse beta decay process is used to detect
. Sterile neutrinos are searched for assuming the model
(3 active and 1 sterile ). The exclusion area in the plane is obtained using a ratio of positron energy
spectra collected at different distances. Therefore results do not depend on
the shape and normalization of the reactor spectrum, as well
as on the detector efficiency. Results are based on 966 thousand antineutrino
events collected at 3 distances from the reactor core. The excluded area covers
a wide range of the sterile neutrino parameters up to
in the most sensitive region.Comment: 10 pages, 13 figures, version accepted for publicatio
The IGEX experiment revisited: a response to the critique of Klapdor-Kleingrothaus,Dietz, and Krivosheina
This paper is a response to the article "Critical View to" the IGEX
neutrinoless double-beta decay experiment..."published in Phys. Rev.D, Volume
65 (2002) 092007," by H.V.Klapdor-Kleingrothaus, A. Dietz, and I.V.Krivosheina,
published as preprint hep-ph/0403056. The criticisms are confronted, and the
questions raised are answered. We demonstrate that the lower limit quoted by
IGEX, for the half life of Ge-76 neutrinoless double beta decay, 1.57x10**25 y,
is correct and that there was no "arithmetical error"-as claimed in the "
Critical Review" article
The first result of the neutrino magnetic moment measurement in the GEMMA experiment
The first result of the neutrino magnetic moment measurement at the
Kalininskaya Nuclear Power Plant (KNPP) with the GEMMA spectrometer is
presented. An antineutrino-electron scattering is investigated. A high-purity
germanium detector of 1.5 kg placed 13.9 m away from the 3 GW reactor core is
used in the spectrometer. The antineutrino flux is . The differential method is used to extract the -e
electromagnetic scattering events. The scattered electron spectra taken in 6200
and 2064 hours for the reactor ON and OFF periods are compared. The upper limit
for the neutrino magnetic moment Bohr magnetons
at 90{%} CL is derived from the data processing.Comment: 9 pages, 10 figures, 2 table
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