Experimental Status of Geo-reactor Search with KamLAND Detector

A natural nuclear fission reactor operating in the center of the Earth has been proposed by Herndon (Hollenbach and Herndon, 2001) as the energy source that powers the geo-magnetic field. The upper limit on the expected geo-reactor power is set by the estimated 12 TW (Buffett, 2003) heat flow from the Earth’s core. If it exists, a nuclear reactor of that size emits a strong anti-neutrino flux. Emitted electron anti-neutrinos can be detected by the Kamioka liquid scintillator anti-neutrino detector (KamLAND) (Raghavan, 2002), and the geo-reactor power level is proporional to the anti-neutrino emission rate. KamLAND measures the geo-reactor power as a constant positive offset in detected anti-neutrino rate on top of the varying anti-neutrino rate coming from man-made reactors. Here we present the first attempt to measure the geo-reactor power. Based on a 776 ton-year exposure of KamLAND to electron anti-neutrinos, the detected flux corresponds to (6 ± 6) TW. The upper limit on the geo-reactor power at 90% confidence level is 18 TW, which is below the lower limit of the total Earth’s radiogenic heat, estimated to be between 19 and 31TW (Anderson, 2003).     

Physics in Next Geoneutrino Detectors

The KamLAND liquid scintillator detector demonstrated the detection of antineutrinos produced by natural radioactivities in the Earth, so-called geoneutrinos. Although this first result of geoneutrinos is consistent with current geophysical models, more accurate measurements are essential to provide a new window for exploring the inside of the Earth. In this article I would like to discuss the future prospects of KamLAND geoneutrino detection, and the possibility of directional measurement of incoming geoneutrinos. It is interesting to consider the application of geoneutrino detectors to measurements of other neutrino signals. The possibility of detecting the solar 7Be, pep and CNO neutrinos is discussed. A new type detector concept is proposed not only to explore the precise measurement of reactor neutrino oscillations but also to enable us to realize the neutrino tomography inside the Earth.     

Imaging the Earth’s Interior: the Angular Distribution of Terrestrial Neutrinos

Decays of radionuclides throughout the earth’s interior produce geothermal heat, but also are a source of antineutrinos; these geoneutrinos are now becoming observable in experiments such as KamLAND. The (angle-integrated) geoneutrino flux has been shown to provide a unique probe of geothermal heating due to decays, and an integral constraint on the distribution of radionuclides in the earth. In this paper, we calculate the angular distribution of geoneutrinos, which opens a window on the differential radial distribution of terrestrial radionuclides. We develop the general formalism for the neutrino angular distribution. We also present the inverse transformation which recovers the terrestrial radioisotope distribution given a measurement of the neutrino angular distribution. Thus, geoneutrinos not only allow a means to image the earth’s interior, but offer a direct measure of the radioactive earth, both revealing the earth’s inner structure as probed by radionuclides, and allowing a complete determination of the radioactive heat generation as a function of radius. Turning to specific models, we emphasize the very useful approximation in which the earth is modeled as a series of shells of uniform density. Using this multishell approximation, we present the geoneutrino angular distribution for the favored earth model which has been used to calculate the geoneutrino flux. In this model the neutrino generation is dominated by decays of potassium, uranium, and thorium in the earth’s mantle and crust; this leads to a very “peripheral” angular distribution, in which 2/3 of the neutrinos come from angles θ ≳ 60° away from the nadir. We note that a measurement of the neutrino intensity in peripheral directions leads to a strong lower limit to the central intensity. We briefly discuss the challenges facing experiments to measure the geoneutrino angular distribution. Currently available techniques using inverse beta decay of protons require a (for now) unfeasibly large number of events to recover with confidence the forward scattering signal from the background of subsequent elastic scatterings. Nevertheless, it is our hope that future large experiments, and/or more sensitive techniques, can resolve an image of the earth’s radioactive interior.     

Upper limits on neutrino fluxes from point-like sources with AMANDA-II

The AMANDA-II telescope, operated by the IceCube collaboration, is currently the world’s most sensitive telescope to fluxes of neutrinos from individual sources. A data sample of 4282 neutrino induced events collected in 1001 days of detector livetime during the years 2000–2004 have now been analyzed looking for a neutrino signal from point-like sources. A sensitivity to fluxes of of d Φ/dE=1.0×10⁻¹⁰(E/TeV)⁻² TeV⁻¹ cm⁻²s⁻¹ was reached in the energy range between 1.7 TeV and 2.4 PeV. So far no statistically significant localized excess of events over the background of atmospheric neutrinos has been found, which would be ascribed to a neutrino source. However, the flux upper limits derived from the non-observation of a signal are comparable to observed fluxes of high energy gamma rays from blazars and within the range of current models for neutrino emission from selected sources. Possible constraints on these models are discussed.      

Towards Earth AntineutRino TomograpHy (EARTH)

The programme Earth AntineutRino TomograpHy (EARTH) proposes to build ten underground facilities each hosting a telescope. Each telescope consists of many detector modules, to map the radiogenic heat sources deep in the interior of the Earth by utilising direction sensitive geoneutrino detection. Recent hypotheses target the core-mantle boundary (CMB) as a major source of natural radionuclides and therefore of radiogenic heat. A typical scale of the processes that take place at the CMB is about 200 km. To observe these processes from the surface requires an angular resolution of about 3°. EARTH aims at creating a high-resolution 3D-map of the radiogenic heat sources in the Earth’s interior. It will thereby contribute to a better understanding of a number of geophysical phenomena observed at the Earth’s surface. This condition requires a completely different approach from the monolithic detector systems as e.g. KamLAND. This paper presents, for such telescopes, the boundary conditions set by physics, the estimated count rates, and the first initial results from Monte-Carlo simulations and laboratory experiments. The Monte-Carlo simulations indicate that the large volume telescope should consist of detector modules each comprising a very large number of detector units, with a cross section of roughly a few square centimetres. The signature of an antineutrino event will be a double pulse event. One pulse arises from the slowing down of the emitted positron, the other from the neutron capture. In laboratory experiments small sized, ¹⁰B-loaded liquid scintillation detectors were investigated as candidates for direction sensitive, low-energy antineutrino detection.     

Probing the Earth’s Interior with the LENA Detector

A future large-volume liquid scintillator detector such as the proposed 50 kton LENA (Low Energy Neutrino Astronomy) detector would provide a high-statistics measurement of terrestrial antineutrinos originating from β-decays of the uranium and thorium chains. Additionally, the neutron is scattered in the forward direction in the detection reaction . Henceforth, we investigate to what extent LENA can distinguish between certain geophysical models on the basis of the angular dependence of the geoneutrino flux. Our analysis is based on a Monte-Carlo simulation with different levels of light yield, considering an unloaded PXE scintillator. We find that LENA is able to detect deviations from isotropy of the geoneutrino flux with high significance. However, if only the directional information is used, the time required to distinguish between different geophysical models is of the order of severals decades. Nonetheless, a high-statistics measurement of the total geoneutrino flux and its spectrum still provides an extremely useful glance at the Earth’s interior.     

Geo-Neutrinos: A Systematic Approach to Uncertainties and Correlations

Geo-neutrinos emitted by heat-producing elements (U, Th and K) represent a unique probe of the Earth interior. The characterization of their fluxes is subject, however, to rather large and highly correlated uncertainties. The geochemical covariance of the U, Th and K abundances in various Earth reservoirs induces positive correlations among the associated geo-neutrino fluxes, and between these and the radiogenic heat. Mass-balance constraints in the Bulk Silicate Earth (BSE) tend instead to anti-correlate the radiogenic element abundances in complementary reservoirs. Experimental geo-neutrino observables may be further (anti)correlated by instrumental effects. In this context, we propose a systematic approach to covariance matrices, based on the fact that all the relevant geo-neutrino observables and constraints can be expressed as linear functions of the U, Th and K abundances in the Earth’s reservoirs (with relatively well-known coefficients). We briefly discuss here the construction of a tentative “geo-neutrino source model” (GNSM) for the U, Th, and K abundances in the main Earth reservoirs, based on selected geophysical and geochemical data and models (when available), on plausible hypotheses (when possible), and admittedly on arbitrary assumptions (when unavoidable). We use then the GNSM to make predictions about several experiments (“forward approach”), and to show how future data can constrain a posteriori the error matrix of the model itself (“backward approach”). The method may provide a useful statistical framework for evaluating the impact and the global consistency of prospective geo-neutrino measurements and Earth models.     

Earth Radioactivity Measurements with a Deep Ocean Anti-neutrino Observatory

We consider the detector size, location, depth, background, and radio-purity required of a mid-Pacific deep-ocean instrument to accomplish the twin goals of making a definitive measurement of the electron anti-neutrino flux due to uranium and thorium decays from Earth’s mantle and core, and of testing the hypothesis for a natural nuclear reactor at the core of Earth. We take the experience with the KamLAND detector in Japan as our baseline for sensitivity and background estimates. We conclude that an instrument adequate to accomplish these tasks should have an exposure of at least 10 kilotonne-years (kT-y), should be placed at least at 4 km depth, may be located close to the Hawaiian Islands (no significant background from them), and should aim for KamLAND radio-purity levels, except for radon where it should be improved by a factor of at least 100. With an exposure of 10 kT-y we should achieve a 25% measurement of the flux of U/Th neutrinos from the mantle plus core. Exposure at multiple ocean locations for testing lateral heterogeneity is possible.     

Back reaction and Hawking radiation from a Vaidya black hole

Using Damour-Ruffini’s and Hamilton-Jacobi’s methods, Hawking radiation from a Vaidya black hole is investigated. Due to non-stationary black holes, the event horizon r _H and the entropy S are all related to both the mass m(υ) and . When the back-reaction of particles’s energy to space-time is considered, we get the emission probability. It is found that the result is different from that of the stationary Schwarzschild black hole, because is the function of mass m(υ).      

A Geoneutrino Experiment at Homestake

A significant fraction of the 44TW of heat dissipation from the Earth’s interior is believed to originate from the decays of terrestrial uranium and thorium. The only estimates of this radiogenic heat, which is the driving force for mantle convection, come from Earth models based on meteorites, and have large systematic errors. The detection of electron antineutrinos produced by these uranium and thorium decays would allow a more direct measure of the total uranium and thorium content, and hence radiogenic heat production in the Earth. We discuss the prospect of building an electron antineutrino detector approximately 700 m³ in size in the Homestake mine at the 4850’ level. This would allow us to make a measurement of the total uranium and thorium content with a statistical error less than the systematic error from our current knowledge of neutrino oscillation parameters. It would also allow us to test the hypothesis of a naturally occurring nuclear reactor at the center of the Earth.     

Periodic solutions for resonance 4/3: Application to the construction of an intermediary orbit for Hyperion’s motion

The motion of Hyperion is an almost perfect application of second kind and second genius orbit, according to Poincaré’s classification. In order to construct such an orbit, we suppose that Titan’s motion is an elliptical one and that the observed frequencies are such that 4n _H−3n _T+3n _ω=0, where n _H, n _T are the mean motions of Hyperion and Titan, n _ω is the rate of rotation of Hyperion’s pericenter. We admit that the observed motion of Hyperion is a periodic motion such as . Then, .N _H, N _T, k∈ N ⁺. With that hypothesis we show that Hyperion’s orbit tends to a particular periodic solution among the periodic solutions of the Keplerian problem, when Titan’s mass tends to zero. The condition of periodicity allows us to construct this orbit which represents the real motion with a very good approximation. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the peculiarities in the rotational frequency evolution of isolated neutron stars

The measurements of pulsar frequency second derivatives have shown that they are 10²−10⁶ times larger than expected for standard pulsar spin-down law, and are even negative for about half of pulsars. We explain these paradoxical results on the basis of the statistical analysis of the rotational parameters ν, and of the subset of 295 pulsars taken mostly from the ATNF database. We have found a strong correlation between and for both and , as well as between ν and . We interpret these dependencies as evolutionary ones due to being nearly proportional to the pulsars’ age. The derived statistical relations as well as “anomalous” values of are well described by assuming the long-time variations of the spin-down rate. The pulsar frequency evolution, therefore, consists of secular change of ν _ev(t), and according to the power law with n≈5, the irregularities, observed within a timespan as a timing noise, and the variations on the timescale larger than that—several decades. This work has been supported by the Russian Foundation for Basic Research (grant No 04-02-17555), Russian Academy of Sciences (program “Evolution of Stars and Galaxies”), and by the Russian Science Support Foundation. The authors would also like to thank the anonymous referee for valuable comments.     

Validation of techniques to mitigate copper surface contamination in CUORE

In this article we describe the background challenges for the CUORE experiment posed by surface contamination of inert detector materials such as copper, and present three techniques explored to mitigate these backgrounds. Using data from a dedicated test apparatus constructed to validate and compare these techniques we demonstrate that copper surface contamination levels better than 10⁻⁷- 10⁻⁸ Bq/cm² are achieved for ²³⁸U and ²³²Th. If these levels are reproduced in the final CUORE apparatus the projected 90% C.L. upper limit on the number of background counts in the region of interest is 0.02–0.03 counts/keV/kg/y depending on the adopted mitigation technique.     

Spectroscopy and photometry of the protoplanetary nebula candidate stHα62 = IRAS 07171+1823

We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 Å spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V _r 〉 = +45 ± 1 and +52 ± 1 km s^?1, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s^?1. The He I λ5876 Å line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s^?1. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N _e = 3.1 × 10³ cm^?3 and T _e ～ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = We present the results of spectroscopic and photometric observations for the B star StHα62 with an IR excess, a post-AGB candidate identified with the IR source IRAS 07171+1823. High-resolution spectroscopy has allowed the λ4330–7340 ? spectrum of the star to be identified: it contains absorption lines of an early B star and emission lines of a gaseous shell. The residual line intensities have been measured. The heliocentric radial velocities measured from absorption lines of the star and emission lines of the shell are 〈V _r 〉 = +45 ± 1 and +52 ± 1 km s⁻¹, respectively. The line-of-sight velocities of gas-dust clouds determined from the interstellar Na I lines are 12 and 33 km s⁻¹. The He I λ5876 ? line exhibits a P Cyg profile, which is indicative of an ongoing mass loss by the star. The expansion velocity of the outer shell estimated from forbidden lines is 12–13 km s⁻¹. Quantitative classification gives the spectral type B0.51 for the star. The parameters of the gaseous shell have been determined: N _e = 3.1 × 10³ cm⁻³ and T _e ∼ 21 000 K. Over 4 years of its observations, the star showed rapid irregular light variations with the amplitudes ΔV = , ΔB = , and ΔU = and no color-magnitude correlation. We estimate the total extinction for the star from our photometric observations as A _v = . Near-IR observations have revealed dust radiation with a temperature of ∼1300 K. We estimate the distance to StHα62 to be r = 5.2 ± 1.2 kpc by assuming that the star is a low-mass (M = 0.55 ± 0.05 M _⊙) protoplanetary nebula. Original Russian Text ? V.P. Arkhipova, V.G. Klochkova, E.L. Chentsov, V.F. Esipov, N.P. Ikonnikova, G.V. Komissarova, 2006, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 10, pp. 737–747.     

The experiment with the fast X-ray monitor (BRM) instrument onboard the CORONAS-PHOTON satellite

The “Fast X-ray Monitor” (BRM) instrument operated in the complex of the scientific instruments onboard the CORONAS-PHOTON satellite from February 19, 2009, until December 1, 2009. The instrument is intended for the registration of the hard X-ray radiation of solar flares in the 20–600 keV energy range in six differential energy channels (20–30, 30–40, 40–50, 50–70, 70–130, and 130–600 keV) with temporal resolution to 1 ms. In the instrument, a detector based on the YAP: Ce scintillator is used; this detector is 70 mm in diameter and 10 mm thick (the decay time is about 28 ns). For the decrease of the back-ground charge of the detector, the collimator limiting the angle of view of the instrument of value 12° is mounted over the scintillator. The effective area of the detector amounts to 27.7 cm² (at the X-ray radiation energy 80 keV), and the dead time of the detector is 1 μs. Over the operation onboard the CORONAS-PHOTON satellite, the BRM instrument has registered gamma ray burst series and, perhaps, one solar flare of the class C1.3 on October 26, 2009.     

A search for energetic neutrons emitted during solar flares

On the basis of solar flare forecasts, balloon flights were made from Hyderabad, India (vertical geomagnetic threshold rigidity of 16.9 GV), to detect the possible emission of high energy neutrons during solar flares. The detector comprised of a central plastic scintillator, completely surrounded by an anticoincidence plastic scintillator shield. The instrument responds to neutrons of about 15–150 MeV and gamma rays of about 5–30 MeV with about the same efficiency. The detector was flown to an atmospheric depth of 25 g cm^-2 on February 26, 1969; while the balloon was at ceiling a flare of importance 2B and one of 1N occurred. No perceptible flare associated increase in the counting rate was observed. Using the observed counting rates, an upper limit of 1.2 × 10^-2 neutrons cm^-2 sec^-1 is obtained for the first time for a flare of importance 2B for neutrons of energy 15–150 MeV. The corresponding upper limit for gamma rays of energy 5–30 MeV is found to be 10^-2 photons cm^-2 sec^-1. The neutron flux limits are compared with the recent calculations of Lingenfelter.     

Uranium isotopic composition and absolute ages of Allende chondrules

A handful of events, such as the condensation of refractory inclusions and the formation of chondrules, represent important stages in the formation and evolution of the early solar system and thus are critical to understanding its development. Compared to the refractory inclusions, chondrules appear to have a protracted period of formation that spans millions of years. As such, understanding chondrule formation requires a catalog of reliable ages, free from as many assumptions as possible. The Pb‐Pb chronometer has this potential; however, because common individual chondrules have extremely low uranium contents, obtaining U‐corrected Pb‐Pb ages of individual chondrules is unrealistic in the vast majority of cases at this time. Thus, in order to obtain the most accurate ²³⁸U/²³⁵U ratio possible for chondrules, we separated and pooled thousands of individual chondrules from the Allende meteorite. In this work, we demonstrate that no discernible differences exist in the ²³⁸U/²³⁵U compositions between chondrule groups when separated by size and magnetic susceptibility, suggesting that no systematic U‐isotope variation exists between groups of chondrules. Consequently, chondrules are likely to have a common ²³⁸U/²³⁵U ratio for any given meteorite. A weighted average of the six groups of chondrule separates from Allende results in a ²³⁸U/²³⁵U ratio of 137.786 ± 0.004 (±0.016 including propagated uncertainty on the U standard [Richter et al. 2010]). Although it is still possible that individual chondrules have significant U isotope variation within a given meteorite, this value represents our best estimate of the ²³⁸U/²³⁵U ratio for Allende chondrules and should be used for absolute dating of these objects, unless such chondrules can be measured individually.     

Bianchi type-III non-static magnetized cosmological model for perfect fluid distribution in general relativity

We have investigated Bianchi type III non-static magnetized cosmological model for perfect fluid distribution in general relativity. We assume that F ₁₂ is the only non-vanishing component of F _ij . Maxwell’s equation

Numerical theory of rotation of the deformable Earth with the two-layer fluid core. Part 1: Mathematical model

Improved differential equations of the rotation of the deformable Earth with the two-layer fluid core are developed. The equations describe both the precession-nutational motion and the axial rotation (i.e. variations of the Universal Time UT). Poincaré’s method of modeling the dynamical effects of the fluid core, and Sasao’s approach for calculating the tidal interaction between the core and mantle in terms of the dynamical Love number are generalized for the case of the two-layer fluid core. Some important perturbations ignored in the currently adopted theory of the Earth’s rotation are considered. In particular, these are the perturbing torques induced by redistribution of the density within the Earth due to the tidal deformations of the Earth and its core (including the effects of the dissipative cross interaction of the lunar tides with the Sun and the solar tides with the Moon). Perturbations of this kind could not be accounted for in the adopted Nutation IAU 2000, in which the tidal variations of the moments of inertia of the mantle and core are the only body tide effects taken into consideration. The equations explicitly depend on the three tidal phase lags δ, δ _c, δ _i responsible for dissipation of energy in the Earth as a whole, and in its external and inner cores, respectively. Apart from the tidal effects, the differential equations account for the non-tidal interaction between the mantle and external core near their boundary. The equations are presented in a simple close form suitable for numerical integration. Such integration has been carried out with subsequent fitting the constructed numerical theory to the VLBI-based Celestial Pole positions and variations of UT for the time span 1984–2005. Details of the fitting are given in the second part of this work presented as a separate paper (Krasinsky and Vasilyev 2006) hereafter referred to as Paper 2. The resulting Weighted Root Mean Square (WRMS) errors of the residuals dθ, sin θd for the angles of nutation θ and precession are 0.136 mas and 0.129 mas, respectively. They are significantly less than the corresponding values 0.172 and 0.165 mas for IAU 2000 theory. The WRMS error of the UT residuals is 18 ms.