Detection of Anomalous Reactor Activity Using Antineutrino Count Rate Evolution Over the Course of a Reactor Cycle

This paper analyzes the sensitivity of antineutrino count rate measurements to changes in the fissile content of civil power reactors. Such measurements may be useful in IAEA reactor safeguards applications. We introduce a hypothesis testing procedure to identify statistically significant differences between the antineutrino count rate evolution of a standard 'baseline' fuel cycle and that of an anomalous cycle, in which plutonium is removed and replaced with an equivalent fissile worth of uranium. The test would allow an inspector to detect anomalous reactor activity, or to positively confirm that the reactor is operating in a manner consistent with its declared fuel inventory and power level. We show that with a reasonable choice of detector parameters, the test can detect replacement of 73 kg of plutonium in 90 days with 95% probability, while controlling the false positive rate at 5%. We show that some improvement on this level of sensitivity may be expected by various means, including use of the method in conjunction with existing reactor safeguards methods. We also identify a necessary and sufficient daily antineutrino count rate to achieve the quoted sensitivity, and list examples of detectors in which such rates have been attained.Comment: 9 pages, 7 figures, submitted to J. Appl. Phy

A mobile antineutrino detector with plastic scintillators

We propose a new type segmented antineutrino detector made of plastic scintillators for the nuclear safeguard application. A small prototype was built and tested to measure background events. A satisfactory unmanned field operation of the detector system was demonstrated. Besides, a detailed Monte Carlo simulation code was developed to estimate the antineutrino detection efficiency of the detector.Comment: 23 pages, 11 figures; accepted for publication in Nuclear Instruments and Methods in Physics Research

Cosmic Optical Background: the View from Pioneer 10/11

We present the new constraints on the cosmic optical background (COB) obtained from an analysis of the Pioneer 10/11 Imaging Photopolarimeter (IPP) data. After careful examination of data quality, the usable measurements free from the zodiacal light are integrated into sky maps at the blue (~0.44 um) and red (~0.64 um) bands. Accurate starlight subtraction is achieved by referring to all-sky star catalogs and a Galactic stellar population synthesis model down to 32.0 mag. We find that the residual light is separated into two components: one component shows a clear correlation with thermal 100 um brightness, while another betrays a constant level in the lowest 100 um brightness region. Presence of the second component is significant after all the uncertainties and possible residual light in the Galaxy are taken into account, thus it most likely has the extragalactic origin (i.e., the COB). The derived COB brightness is (1.8 +/- 0.9) x 10^(-9) and (1.2 +/- 0.9) x 10^(-9) erg/s/cm2/sr/A at the blue and red band, respectively, or 7.9 +/- 4.0 and 7.7 +/- 5.8 nW/m2/sr. Based on a comparison with the integrated brightness of galaxies, we conclude that the bulk of the COB is comprised of normal galaxies which have already been resolved by the current deepest observations. There seems to be little room for contributions of other populations including "first stars" at these wavelengths. On the other hand, the first component of the IPP residual light represents the diffuse Galactic light (DGL) - scattered starlight by the interstellar dust. We derive the mean DGL-to-100 um brightness ratios of 2.1 x 10^(-3) and 4.6 x 10^(-3) at the two bands, which are roughly consistent with the previous observations toward denser dust regions. Extended red emission in the diffuse interstellar medium is also confirmed.Comment: Accepted for publication in the Astrophysical Journal; Typos correcte

Transport properties of ybco thin films near the critical state with no applied field

Transport measurements carried out on twinned ybco films are compared to the predictions of a previously proposed model suggesting that the vortices move along the films twin boundaries that behave as rows of Josephson weak links [P.Bernstein and J.F.Hamet, J.Appl.Phys.95 (2004) 2569]. The obtained results suggest that, except if the films are very thin, the twin boundaries consist of superimposed rows of weak links with mean height,ds, whose mean length along the TBs is an universal function of T/Tc, the reduced temperature. This conclusion yields a general expression for the critical surface current density of the films as a function of T/Tc and of the number of superimposed weak links rows, while the critical current density depends on ds. A comparison of the measurements reported by various authors shows that the nature of the substrate and the growth technique have both a strong effect on ds . The existence of superimposed weak links rows is attributed to extended defects generated by y2o3 inclusions.Comment: 33 pages, 13 figures; accepted for publication in Physica

A sharp stability criterion for the Vlasov-Maxwell system

We consider the linear stability problem for a 3D cylindrically symmetric equilibrium of the relativistic Vlasov-Maxwell system that describes a collisionless plasma. For an equilibrium whose distribution function decreases monotonically with the particle energy, we obtained a linear stability criterion in our previous paper. Here we prove that this criterion is sharp; that is, there would otherwise be an exponentially growing solution to the linearized system. Therefore for the class of symmetric Vlasov-Maxwell equilibria, we establish an energy principle for linear stability. We also treat the considerably simpler periodic 1.5D case. The new formulation introduced here is applicable as well to the nonrelativistic case, to other symmetries, and to general equilibria

Multiobjective parsimony enforcement for superior generalisation performance

Program Bloat - phenomenon of ever-increasing program size during a GP run - is a recognised and widespread problem. Traditional techniques to combat program bloat are program size limitations of parsimony pressure (penalty functions). These techniques suffer from a number of problems, in particular their reliance on parameters whose optimal values it is difficult to a priori determine. In this paper, we introduce POPE-GP, a system that makes use of the NSGA-II multiobjective evolutionary algorithm as an alternative, parameter-free technique for eliminating program bloat. We test it on a classification problem and find that while vastly reducing program size, it does improve generalisation performance

Using schema transformation pathways for data lineage tracing

With the increasing amount and diversity of information available on the Internet, there has been a huge growth in information systems that need to integrate data from distributed, heterogeneous data sources. Tracing the lineage of the integrated data is one of the problems being addressed in data warehousing research. This paper presents a data lineage tracing approach based on schema transformation pathways. Our approach is not limited to one specific data model or query language, and would be useful in any data transformation/integration framework based on sequences of primitive schema transformations

Screening magnetic fields by a superconducting disk: a simple model

We introduce a simple approach to evaluate the magnetic field distribution around superconducting samples, based on the London equations; the elementary variable is the vector potential. This procedure has no adjustable parameters, only the sample geometry and the London length, $\lambda$, determine the solution. The calculated field reproduces quantitatively the measured induction field above MgB$_2$ disks of different diameters, at 20K and for applied fields lower than 0.4T. The model can be applied if the flux line penetration inside the sample can be neglected when calculating the induction field distribution outside the superconductor. Finally we show on a cup-shape geometry how one can design a magnetic shield satisfying a specific constraint

Dissipative control of energy flow in interconnected systems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76668/1/AIAA-1993-3770-736.pd