On the Importance of Isospin Effects for the Interpretation of Nuclear Collisions

It is demonstrated that many aspects of nuclear collisions, as for instance the evolution of $\pi^{+}/\pi^{-}$ and $K/\pi$ ratios with $x_F$ and $\sqrt{s}$, are influenced by isospin effects already present in elementary nucleon--nucleon collisions.Comment: 3 pages, 5 figures. International Europhysics Conference on High Energy Physics, Aachen, Germany, July 2003, submitted to JHE

Evaluation Of Covert Plutonium Production From Unconventional Uranium Sources

The potential for a relatively non-advanced nation to covertly acquire a significant quantity of weapons-grade plutonium using a gas-cooled, natural uranium-fueled reactor based on relatively primitive early published designed is evaluated in this article. The economic and technical issues that would influence the design decisions of a covert 239Pu production program are considered. Several unconventional uranium acquisition approaches were explored. Methods for extracting uranium from enrichment tails, seawater, and coal ash sources were considered. The evaluation indicated that uranium extraction from coal ash or insitu leaching from underground deposits could be performed in economical manner that might be difficult to detect by the international community. These two methods were estimated to be within the technical capabilities of an under-developed national. Calculations performed using the Monte Carlo N-Particle code (MCNP) showed that extracting uranium from enrichment tails would not be a technically feasible source for reactor fuel fabrication because the 235U concentration inside the enrichment tails would not be high enough to maintain criticality in the relatively unsophisticated reactor design considered. The SCALE code package was used to perform reactor physics and depletion calculations used to evaluate the effect of different combinations of uranium irradiation time and reactor power density had on plutonium production rates and isotope concentrations. The results of these simulations were used to estimate the desirability of the modeled plutonium for use in a weapon with published materials attractiveness figures of merit. All the modeled reactor conditions produced material that was highly attractive for use in a nuclear weapon. Historical examples of early gas-cooled reactors were used to examine the complexity associate with building various gas-cooled reactor designs. These examples were compared to simulated reactor conditions. The choices that a covert unsophisticated nuclear weapons program might consider when designing a reactor were evaluated. An air-cooled design was found to be a simple and cost effective solution for a group interested in producing a small number of significant quantities (8 kg) of plutonium

System size and centrality dependence of the balance function in A+A collisions at sqrt[sNN]=17.2 GeV

Electric charge correlations were studied for p+p, C+C, Si+Si, and centrality selected Pb+Pb collisions at sqrt[sNN]=17.2 GeV with the NA49 large acceptance detector at the CERN SPS. In particular, long-range pseudorapidity correlations of oppositely charged particles were measured using the balance function method. The width of the balance function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions

System size and centrality dependence of the balance function in A + A collisions at sqrt s NN = 17.2 GeV

Electric charge correlations were studied for p+p, C+C, Si+Si and centrality selected Pb+Pb collisions at sqrt s_NN = 17.2$ GeV with the NA49 large acceptance detector at the CERN-SPS. In particular, long range pseudo-rapidity correlations of oppositely charged particles were measured using the Balance Function method. The width of the Balance Function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions

Nose-cone calorimeter: PHENIX forward upgrade

PHENIX is a high rate experiment efficient at measuring rare processes, but has limited acceptance in azimuth and pseudorapidity (η). The Nose Cone Calorimeter (NCC), a W–Si sampling calorimeter in the region of 0.9<η<3, is one of the upgrades which will significantly increase coverage in both azimuth and pseudorapidity. The NCC will expand PHENIX’s precision measurements of electromagnetic probes in η, reconstruct jets, perform a wide scope of correlation measurements, and enhance triggering capabilities. The detector will significantly contribute to measurements of γ-jet correlations, quarkonia production, and low-x nuclear structure functions. This report discusses details of the detector design and its performance concerning a sample of the physics topics which will benefit from the NCC. In view of recent funding difficulties, outlook of the activities is discussed

Pion production in PbPb collisions at the SPS

New data on charged pion production in PbPb interactions are measured by the NA49 experiment and compared to NN interactions. Different phenomena are isolated. It is argued that salient features of pion production in nuclear interactions can be understood as a result of NN dynamics and of other non-exotic phenomena

Plutonium Signatures in Molten-Salt Reactor Off-Gas Tank and Safeguards Considerations

Fluid-fueled molten-salt reactors (MSRs) are actively being developed by several companies, with plans to deploy them internationally. The current IAEA inspection tools are largely incompatible with the unique design features of liquid fuel MSRs (e.g., the complex fuel chemistry, circulating fuel inventory, bulk accountancy, and high radiation environment). For these reasons, safeguards for MSRs are seen as challenging and require the development of new techniques. This paper proposes one such technique through the observation of the reactor’s off-gas. Any reactor design using low-enriched uranium will build up plutonium as the fuel undergoes burnup. Plutonium has different fission product yields than uranium. Therefore, a shift in fission product production is expected with fuel evolution. The passive removal of certain gaseous fission products to the off-gas tank of an MSR provides a valuable opportunity for analysis without significant modifications to the design of the system. Uniquely, due to the gaseous nature of the isotopes, beta particle emissions are available for observation. The ratios of these fission product isotopes can, thus, be traced back to the relative amount and types of fissile isotopes in the core. This proposed technique represents an effective safeguards tool for bulk accountancy which, while avoiding being onerous, could be used in concert with other techniques to meet the IAEA’s timeliness goals for the detection of a diversion