Mimicking diffuse supernova antineutrinos with the sun as a source

Measuring the $ \bar \nu _e $ \bar \nu _e component of the cosmic diffuse supernova neutrino background (DSNB) is the next ambitious goal for low-energy neutrino astronomy. The largest flux is expected in the lowest accessible energy bin. However, for E ≲ 15 MeV a possible signal can be mimicked by a solar $ \bar \nu _e $ \bar \nu _e flux that originates from the usual ⁸B neutrinos by spin-flavor oscillations. We show that such an interpretation is possible within the allowed range of neutrino electromagnetic transition moments and solar turbulent field strengths and distributions. Therefore, an unambiguous detection of the DSNB requires a significant number of events at E ≳ 15 MeV.     

40-MCi tritium source of antineutrinos

Some technical and technological aspects of development, design, and safe operation of an artificial tritium source with an antineutrino activity of 40 MCi for experiments to measure the neutrino magnetic momentum are considered.     

The Casimir effect as a possible source of cosmic energy

Energy production due to the Casimir effect is considered for the case of a superdense state of matter, which can appear in such cosmological objects as white dwarfs, neutron stars, quasars and so on. The energy output produced by the Casimir effect during the creation of a neutron star turns out to be sufficient to explain nova and supernova explosions. It is shown that the Casimir effect might be a possible source of the huge energy output of quasars.     

Determination of the direction to a source of antineutrinos via inverse beta decay in Double Chooz

To determine the direction to a source of neutrinos (and antineutrinos) is an important problem for the physics of supernovae and of the Earth. The direction to a source of antineutrinos can be estimated through the reaction of inverse beta decay. We show that the reactor neutrino experiment Double Chooz has unique capabilities to study antineutrino signal from point-like sources. Contemporary experimental data on antineutrino directionality is given. A rigorous mathematical approach for neutrino direction studies has been developed. Exact expressions for the precision of the simple mean estimator of neutrinos’ direction for normal and exponential distributions for a finite sample and for the limiting case of many events have been obtained.     

Thermal crisis of a vortex source

The effect of circulation in the field of a bulk vortex source on thermal crisis (flow choking induced by energy supply in a layer in accordance with a known law) is studied. Substantial changes in the value of energy supply parameter and slight variations in the coordinate of the critical cross section in which the velocity of sound is attained are revealed, and the dependence of these parameters on the location and width of the heat-supply region is noted. The possibility of transition to a supersonic flow when the heat release region is near the minimal cross section of the vortex source is analyzed. The difference between the cases of polyatomic and monatomic gases is demonstrated. Distinguishing features of the vortex sink are considered.     

The kinetic energy of fission fragments

The Coulomb energy is calculated for the nucleus in the process of fission (in the general case asymmetrical) into two spherical fragments and for ellipsoidal deformations. In the first case the calculation has been done on an M-20 electronic computer. Conclusions are drawn on the form of the nucleus in symmetrical fission at the moment of fragmentation and its effect on the kinetic energy of the fragments.We wish to express our thanks to Yu. Volkov for making the numerical calculations.     

Space charge effects as a source of electron energy spread andefficiency degradation in gyrotrons

Space charge effects (so-called negative-mass instability) as the reason for electron energy spread developing in the region of the electron drift between the cathode and the cavity of a gyrotron are discussed. The quasioptical gyrotron working at third harmonic that is developed at Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne, is used to demonstrate the expected efficiency degradation     

Mass and energy dependence of pion-induced fission

Data for fission induced by pi meson beams from 80 to 500 MeV are presented for nuclei from Fe through Pu as measured by solid state track detectors. The general trends for binary fission withπ ⁺ are reproduced fairly well by a calculation in the ‘high excitation’ limit with standard level density and fission barrier parameters, butπ ^? data are underpredicted. A universal dependence of the binary fission probabilities with the fissility (Z±1)²/A is found to be valid for both pion beam charges for all beam energies below the delta resonance. Probabilities for observing three fragments withπ ⁺ are not reproduced by a ternary fission application of the model found to work for binary fission.     

A conical piezoelectric transducer with integral sensor as a self-calibrating acoustic emission energy source

The experimental results of a conical piezoelectric transducer with integral backing sensor as a self-calibrating simulated acoustic emission (SAE) energy source are presented. It has been shown that there is a negative linear relationship between the energy of SAE signal detected by the backing sensor and the relative strength (signal energy) of SAE source in the structure detected by a reference sensor under different transducer-to-structure coupling efficiencies, with AC drives of the same wave packet, frequency and peak amplitude to excite the conical transducer as a SAE source at all the investigated frequencies over the frequency range of interest in AE measurements (nominally from 50 kHz to around 1 MHz). This should enable the relative strength of the SAE source in a structure to be determined using the SAE measurement from the backing sensor for the selected electrical inputs to the conical transducer, and hence to remove the concerns about inconsistent transducer-to-structure coupling affecting the relative strength of the SAE source for calibration.     

Prompt radiation as a probe for fission dynamics

It is shown that the Strutinsky-Denisov induced polarization mechanism leads to the appearance of the prompt electric dipole radiation from fission fragments of ²³⁵Uby thermal neutrons in the domain of around 5 MeV. The probability of the radiation is at the level of 0.001 per fission, which is in agreement with experiment. The angular distribution exhibits left-right asymmetry with respect to the direction of the neutron polarization axis. That means that the emission of gamma quanta at the given angle depends on the neutron polarization. The asymmetry is at the level of 10⁻³. The study of this effect will give a direct information about the scission configuration, nuclear viscosity, and dissipation properties of the collective energy of the surface vibration in fragments with large amplitude. This will give a complete picture of the process of snapping back the nuclear surface.     

Effect of entrance channel parameters on fission fragment angular momentum in medium energy fission

Independent isomeric yield ratios of¹³²I were radiochemically determined in alpha particle induced fission of²³⁸U in the energy range 25–44 MeV. Fission fragment angular momenta were deduced from the measured isomeric yield ratios using spin dependent statistical model analysis. It was seen that angular momentum of¹³²I increases with increase of excitation energy and angular momentum of the fissioning nucleus. Comparison of the present data on¹³²I in²³⁸U(α,f) with the literature data for the same product in²³⁸U(p, f) and²³⁸U(γ, f) at various excitation energies show that fragment angular momentum strongly depends on the input angular momentum in the range of excitation energy considered. Experimental fragment angular momentum at all excitation energies were seen to be in agreement with the theoretical values calculated based on thermal equilibration of the various collective rotational degrees after considering the occurence of multichance fission. Thus, strong effect of input angular momentum as well as the statistical equilibration among the various collective rotational degrees of freedom in medium energy fission is corroborated.     

The congruence energy: a contribution to nuclear masses,deformation energies and fission barriers

The difference between measured binding energies and those calculated using a shell- and pairing-corrected Thomas-Fermi model can be described approximately by C(I) = −10 exp(−4.2{I}) MeV, where I = (N - Z)/A. Our interpretation of this extra binding is in terms of the granularity of quantal nucleonic density distributions, which leads to a stronger interaction for a neutron and proton with congruent nodal structures of their wave functions. The predicted doubling of this congruence energy in fission is supported by an analysis of measured fission barriers and by a study of wave functions in a dividing Hill-Wheeler box potential. A semi-empirical formula for the shape-dependent congruence energy is described.     

Measurement of high energy neutrons by fission reactions

In most high energy radiation fields, such as those encountered around accelerators or cosmic rays in the atmosphere, neutrons produce the largest percentage of the hadron dose. In these radiation fields, the neutron spectrum is typically formed by low energy neutrons (evaporation spectrum) and high energy neutrons (knock-on spectrum).

Neutron spectrometry and dosimetry are better understood for low energy neutrons (i.e. neutrons with energy below 20 MeV) than for those of higher energies. This paper reports the study of different detectors based on the registration of fission fragments of different heavy elements (namely bismuth, gold and tantalum), which have their principal response to high energy neutrons.     

Thermal source of stimulated radiation

The action of a source of stimulated radiation is investigated under conditions when the energy is supplied from a thermal reservoir. For the three-level system a calculation based on thermodynamic considerations and kinetic equations is carried out. Relations expressing the dependence of the minimum temperature of the hot reservoir, which is necessary for inversion, on the parameters of the system and on the maximum intensity of exciting radiation are found.The expression for the efficiency of conversion of thermal energy into stimulated radiation is _max<(1–T ₀/T)(A ₃₂–A ₂₁)/(A ₃₂+A ₃₁).This efficiency is always lower than the Carnot efficiency and depends also on the value of the Einstein coefficients for spontaneous emission between different levels.The author heartily thanks M. Trlifaj, K. Pátek and A. Fousková for stimulating discussions.     

Co-ion dependence of DNA nuclease activity suggests hydrophobic cavitation as a potential source of activation energy

The source of the activation energy that allows cutting of DNA by restriction enzymes is unclear. A systematic study of the cutting efficiency of the type-II restriction endonuclease EcoRI, with varying background electrolyte ion pair and buffer reported here, shows only a modest dependence of efficiency on cation type. Surprisingly, efficiency does depend strongly on the presumed indifferent anion of the background salt. What emerges is that competition between the background salt anion and the buffer anion for the enzyme and DNA surfaces is crucial. The results are unexpected and counterintuitive from the point of view of conventional electrolyte theory. However, taken together with recent developments in surface chemistry, the results do fall into place and could also suggest a novel mechanism for enzyme activity as an alternative to metal-activated hydrolysis: microscopic cavitation in a hydrophobic pocket might be the source of activation energy. Received 19 June 2000 and Received in final form 17 October 2000     

Thermal storage of solar energy as sensible heat at medium temperatures

Summary A model has been solved in order to determine the thermal losses of a storage tank, where thermal energy is stored as sensible heat of a diathermic fluid at medium temperatures. A parametric analysis has been performed in order to evaluate the influence of various design parameters on the thermal discharge of the accumulator. This work was has been performed in the framework of activities of the ?Progetto Finalizzato Energetica? supported by the C.R.N.     

用周期铁磁结构环作磁累积发生器的初始能源

 首先推导了描述铁磁体的磁场方程，并分析计算了圆筒型周期性永磁结构环内部所携带的磁能，研究了磁能与永磁体质量的关系。分析表明，采用内外径分别为60和90mm、长为60mm、质量约为30kg的四级周期永磁结构能够提供1kJ左右的磁能。这种结构有可能成为间接馈电磁累积发生器的初始能源。     

Formation of a high-current pulsed gas discharge as a source ofhighly concentrated energy flux to treat metal surfaces

The properties of a novel, pulsed, high-current gas discharge with minimized energy losses are investigated. The discharge provides a highly concentrated energy flux that can be used to treat metal surfaces and to form thin surface layers with desirable properties. A theoretical treatment of the formation of the discharge is presented, and the limitations on its voltage and interelectrode separation length are considered. Experiments are carried out to test the theoretical predictions of the discharge parameters. The experimental results show that more than 80% of the energy input to the discharge from the power supply is delivered to the metal surface     

Thermal unparticles: a new form of energy density in the universe

An unparticle with scaling dimension has peculiar thermal properties due to its unique phase space structure. We find that the equation of state parameter , the ratio of pressure to energy density, is given by providing a new form of energy in our universe. In an expanding universe, the unparticle energy density evolves dramatically differently from that for photons. For , even if at a high decoupling temperature T _D is very small, it is possible to have a large relic density at present photon temperature T _γ ⁰, large enough to play the role of dark matter. We calculate T _D and using photon–unparticle interactions for illustration.     

Correlation between fractional independent yields and neutron-to-proton ratio of fission products in low energy fission

Fractional independent yields of fission products in the thermal neutron-induced fission of²³³U,²³⁵U,²³⁹Pu,²⁴¹Pu and in the spontaneous fission of²⁵²Cf have been correlated with the neutron-to-proton ratio of the fission products. The yields of the products from a fissioning system, when plotted as a function of neutron-to-proton (N/Z) ratio of fission preducts, fall on two Gaussian distribution corresponding to light and heavy fission products. The centroids of the distribution or the most probable value of neutron-to-proton ratio is found to be very close to theN/Z of the fissioning nucleus. From the most probable value ofN/Z the various parameters of charge distribution e.g. most probable massA _p, most probable chargeZ _p, the mass dispersionσ _Aand the charge dispersionσ _Zhave been obtained and are in good agreement with the experimental values ofA _pandZ _p.