396 research outputs found
Inverse beta decay reaction in Th and U fission antineutrino flux
Energy spectra of antineutrinos coming from Th and U
neutron-induced fission are calculated, relevant inverse beta decay
positron spectra and total cross sections are
found. This study is stimulated by a hypothesis that a self-sustained nuclear
chain reaction is burning at the center of the Earth ("Georeactor"). The
Georeactor, according to the author of this idea, provides energy necessary to
sustain the Earth's magnetic field. The Georeactor's nuclear fuel is U
and, probably, Th and U. Results of present study may appear to
be useful in future experiments aimed to test the Georector hypothesis and to
estimate its fuel components as a part of developments in geophysics and
astrophysics based on observations of low energy antineutrinos in Nature.Comment: 6 pages in LaTeX and 2 ps figures. Submitted to Physics of Atomic
Nucle
Neutrino-induced deuteron disintegration experiment
Cross sections for the disintegration of the deuteron via neutral-current
(NCD) and charged-current (CCD) interactions with reactor antineutrinos are
measured to be 6.08 +/- 0.77 x 10^(-45) cm-sq and 9.83 +/- 2.04 x 10^(-45)
cm-sq per neutrino, respectively, in excellent agreement with current
calculations. Since the experimental NCD value depends upon the CCD value, if
we use the theoretical value for the CCD reaction, we obtain the improved value
of 5.98 +/- 0.54 x 10^(-45) for the NCD cross section. The neutral-current
reaction allows a unique measurement of the isovector-axial vector coupling
constant in the hadronic weak interaction (beta). In the standard model, this
constant is predicted to be exactly 1, independent of the Weinberg angle. We
measure a value of beta^2 = 1.01 +/- 0.16. Using the above improved value for
the NCD cross section, beta^2 becomes 0.99 +/- 0.10.Comment: 22pages, 9 figure
Компресорні установки
Зміст видання відповідає освітньо-професійній програмі підготовки кадрів
з вищою освітою напряму „Електротехніка та електротехнології“, зокрема –
програмі дисципліни „Енергетичні установки“.
Розглянуто основні положення теорії компресорних машин, будову,
експлуатаційні особливості та методи регулювання режиму роботи поршневих,
ротаційних, гвинтових, водокільцевих і відцентрових компресорів.
Посібник адресовано студентам спеціальності „Енергетичний
менеджмент“, які вивчають дисципліну „Енергетичні установки“. Він може
бути корисним також студентам напрямів „Гірництво“, „Інженерна механіка“ та
„Електромеханіка“ при вивченні стаціонарних установок гірничих підприємств
Inverse Beta Decay in a Nonequilibrium Antineutrino Flux from a Nuclear Reactor
The evolution of the reactor antineutrino spectrum toward equilibrium above
the inverse beta-decay threshold during the reactor operating period and the
decay of residual antineutrino radiation after reactor shutdown are considered.
It is found that, under certain conditions, these processes can play a
significant role in experiments seeking neutrino oscillations.Comment: 8 pages including 5 ps figure
Present and Future Experiments in Non-equilibrium Reactor Antineutrino Energy Spectrum
Considerable efforts that have been undertaken in the recent years in low
energy antineutrino experiments require further systematic investigations in
line of reactor antineutrino spectroscopy as a metrological basis of these
experiments. We consider some effects associated with the non-equilibrium of
reactor antineutrino radiation and residual antineutrino emission from spent
reactor fuel in contemporary antineutrino experiments.Comment: 7 pages, 5 figures; Talk presented at International Conference
NANP-2005, Dubna, Russia, Jun.-2005; Submitted to Phys. Atom. Nuc
Investigation of the chemical vicinity of crystal defects in ion-irradiated Mg and AZ31 with coincident Doppler broadening spectroscopy
Crystal defects in magnesium and magnesium based alloys like AZ31 are of
major importance for the understanding of their macroscopic properties. We have
investigated defects and their chemical surrounding in Mg and AZ31 on an atomic
scale with Doppler broadening spectroscopy of the positron annihilation
radiation. In these Doppler spectra the chemical information and the defect
contribution have to be thoroughly separated. For this reason samples of
annealed Mg were irradiated with Mg-ions in order to create exclusively
defects. In addition Al- and Zn-ion irradiation on Mg-samples was performed in
order to create samples with defects and impurity atoms. The ion irradiated
area on the samples was investigated with laterally and depth resolved positron
Doppler broadening spectroscopy (DBS) and compared with preceding
SRIM-simulations of the vacancy distribution, which are in excellent agreement.
The investigation of the chemical vicinity of crystal defects in AZ31 was
performed with coincident Doppler broadening spectroscopy (CDBS) by comparing
Mg-ion irradiated AZ31 with Mg-ion irradiated Mg. No formation of
solute-vacancy complexes was found due to the ion irradiation, despite the high
defect mobility.Comment: Submitted to Physical Review B on March 20 20076. Revised version
submitted on September 28 2007. Accepted on October 19 200
High-Intensity and High-Brightness Source of Moderated Positrons Using a Brilliant gamma Beam
Presently large efforts are conducted towards the development of highly
brilliant gamma beams via Compton back scattering of photons from a
high-brilliance electron beam, either on the basis of a normal-conducting
electron linac or a (superconducting) Energy Recovery Linac (ERL). Particularly
ERL's provide an extremely brilliant electron beam, thus enabling to generate
highest-quality gamma beams. A 2.5 MeV gamma beam with an envisaged intensity
of 10^15 s^-1, as ultimately envisaged for an ERL-based gamma-beam facility,
narrow band width (10^-3), and extremely low emittance (10^-4 mm^2 mrad^2)
offers the possibility to produce a high-intensity bright polarized positron
beam. Pair production in a face-on irradiated W converter foil (200 micron
thick, 10 mm long) would lead to the emission of 2 x 10^13 (fast) positrons per
second, which is four orders of magnitude higher compared to strong radioactive
^22Na sources conventionally used in the laboratory.Using a stack of converter
foils and subsequent positron moderation, a high-intensity low-energy beam of
moderated positrons can be produced. Two different source setups are presented:
a high-brightness positron beam with a diameter as low as 0.2 mm, and a
high-intensity beam of 3 x 10^11 moderated positrons per second. Hence,
profiting from an improved moderation efficiency, the envisaged positron
intensity would exceed that of present high-intensity positron sources by a
factor of 100.Comment: 9 pages, 3 figure
Components of Antineutrino Emission in Nuclear Reactor
New scattering experiments aimed for sensitive searches of
the magnetic moment and projects to explore small mixing angle
oscillations at reactors call for a better understanding of the reactor
antineutrino spectrum. Here we consider six components, which contribute to the
total spectrum generated in nuclear reactor. They are: beta
decay of the fission fragments of U, Pu, U and
Pu, decay of beta-emitters produced as a result of neutron capture in
U and also due to neutron capture in accumulated fission fragments
which perturbs the spectrum. For antineutrino energies less than 3.5 MeV we
tabulate evolution of spectra corresponding to each of the four
fissile isotopes vs fuel irradiation time and their decay after the irradiation
is stopped and also estimate relevant uncertainties. Small corrections to the
ILL spectra are considered.Comment: LaTex 8 pages, 2 ps figure
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