SuperHILAC and the Berkeley superheavy element program

From 24th congress of the International Union of Pure and Applied Chemistry; Hamburg, F.R. Germany (3 Sep 1973). A nontechnical description of the SuperHILAC, now under construction, is presented. The injector, linear accelerators, and mass separator for identifying heavy elements are described, along with the basic layouts of the injector and target areas. (7 figures) (RWR

Berkeley new element program

The work done with element 106 is reviewed, and a new experiment which bears on the properties of the isotope of mass 260 with atomic number 104 is discussed. It is noted that in the case of element 106 a link is demonstrated to the granddaughter as well as the daughter. (JFP

The preparation of accelerator targets by the evaporation of acetate-organic solutions in the presence of NH/sub 3/ gas

The chemical methods described in this paper have been developed for preparation of isotopic targets for bombardment by accelerator-produced ions. Three systems are compared: nitrate-, chloride-, and acetate-organic solutions. The best method was found to be the metallic acetate-organic solution system, evaporated onto the substrate in the presence of ammonia gas. A detailed procedure is given for this method. The targets obtained by the acetate-organic solution system are uniform and adherent. The hydroxide forms fine crystals of good quality for target thicknesses from a few ..mu..g/cm/sup 2/ to several mg/cm/sup 2/. Thicknesses up to 5 mg/cm/sup 2/ of Eu as the oxide were obtained by this method. The process is simple and fast. 18 refs., 1 tab

New Low Mass Isotopes of Emanation (Element 86)

Among the spallation products obtained from the 350-Mev proton bombardment of Th{sup 232} they have identified two gaseous alpha-emitters which apparently do not decay into any presently known alpha-decay chains. The half-lives observed for the decay of the alpha-activities are 23 minutes and 2.1 hours. These half-lives may be principally determined by an unknown amount of orbital electron capture. At least one alpha-emitting daughter (about 4 hours half-life) has been observed to grow from a gaseous parent, but it has not been determined whether it arises from alpha-decay or electron-capture. Since these gaseous atoms emit alpha-particles it is assumed that they are isotopes of element 86 (emanation or radon) rather than a lighter rare gas. if they were heavy isotopes such as Em{sup 221} or Em{sup 223}, both unknown, they would decay into known alpha-decay series, the neptunium and actinium series, respectively, and so would grow known short lived alpha-emitters which would have been detected. It thus appears reasonable that they must be lighter than the known emanation isotopes

Thermodynamic Model for Energy-Constrained Open-System Evolution of Crustal Magma Bodies Undergoing Simultaneous Recharge, Assimilation and Crystallization: the Magma Chamber Simulator

The Magma Chamber Simulator quantifies the impact of simultaneous recharge, assimilation and crystallization through mass and enthalpy balance in a multicomponent–multiphase (melt + solids ± fluid) composite system. As a rigorous thermodynamic model, the Magma Chamber Simulator computes phase equilibria and geochemical evolution self-consistently in resident magma, recharge magma and wallrock, all of which are connected by specified thermodynamic boundaries, to model an evolving open-system magma body. In a simulation, magma cools from its liquidus temperature, and crystals ± fluid are incrementally fractionated to a separate cumulate reservoir. Enthalpy from cooling, crystallization, and possible magma recharge heats wallrock from its initial subsolidus temperature. Assimilation begins when a critical wallrock melt volume fraction (0·04–0·12) in a range consistent with the rheology of partially molten rock systems is achieved. The mass of melt above this limit is removed from the wallrock and homogenized with the magma body melt. New equilibrium states for magma and wallrock are calculated that reflect conservation of total mass, mass of each element and enthalpy. Magma cooling and crystallization, addition of recharge magma and anatectic melt to the magma body (where appropriate), and heating and partial melting of wallrock continue until magma and wallrock reach thermal equilibrium. For each simulation step, mass and energy balance and thermodynamic assessment of phase relations provide major and trace element concentrations, isotopic characteristics, masses, and thermal constraints for all phases (melt + solids ± fluid) in the composite system. Model input includes initial compositional, thermal and mass information relevant to each subsystem, as well as solid–melt and solid–fluid partition coefficients for all phases. Magma Chamber Simulator results of an assimilation–fractional crystallization (AFC) scenario in which dioritic wallrock at 0·1 GPa contaminates high-alumina basalt are compared with results in which no assimilation occurs [fractional crystallization only (FC-only)]. Key comparisons underscore the need for multicomponent–multiphase energy-constrained thermodynamic modeling of open systems, as follows. (1) Partial melting of dioritic wallrock yields cooler silicic melt that contaminates hotter magma. Magma responds by cooling, but a pulse of crystallization, possibly expected based on thermal arguments, does not occur because assimilation suppresses crystallization by modifying the topology of multicomponent phase saturation surfaces. As a consequence, contaminated magma composition and crystallizing solids are distinct compared with the FC-only case. (2) At similar stages of evolution, contaminated melt is more voluminous (∼3·5×) than melt formed by FC-only. (3) In AFC, some trace element concentrations are lower than their FC-only counterparts at the same stage of evolution. Elements that typically behave incompatibly in mafic and intermediate magmas (e.g. La, Nd, Ba) may not be ‘enriched’ by crustal contamination, and the most ‘crustal’ isotope signatures may not correlate with the highest concentrations of such elements. (4) The proportion of an element contributed by anatectic melt to resident magma is typically different for each element, and thus the extent of mass exchange between crust and magma should be quantified using total mass rather than the mass of a single element. Based on these sometimes unexpected results, it can be argued that progress in quantifying the origin and evolution of open magmatic systems and documenting how mantle-derived magmas and the crust interact rely not only on improvements in instrumentation and generation of larger datasets, but also on continued development of computational tools that couple thermodynamic assessment of phase equilibria in multicomponent systems with energy and mass conservation

Lava channel formation during the 2001 eruption on Mount Etna: evidence for mechanical erosion

We report the direct observation of a peculiar lava channel that was formed near the base of a parasitic cone during the 2001 eruption on Mount Etna. Erosive processes by flowing lava are commonly attributed to thermal erosion. However, field evidence strongly suggests that models of thermal erosion cannot explain the formation of this channel. Here, we put forward the idea that the essential erosion mechanism was abrasive wear. By applying a simple model from tribology we demonstrate that the available data agree favorably with our hypothesis. Consequently, we propose that erosional processes resembling the wear phenomena in glacial erosion are possible in a volcanic environment.Comment: accepted for publication in Physical Review Letter

The New Element Californium (Atomic Number 98)

Definite identification has been made of an isotope of the element with atomic number 98 through the irradiation of Cm{sup 242} with about 35-Mev helium ions in the Berkeley Crocker Laboratory 60-inch cyclotron. The isotope which has been identified has an observed half-life of about 45 minutes and is thought to have the mass number 244. The observed mode of decay of 98{sup 244} is through the emission of alpha-particles, with energy of about 7.1 Mev, which agrees with predictions. Other considerations involving the systematics of radioactivity in this region indicate that it should also be unstable toward decay by electron capture. The chemical separation and identification of the new element was accomplished through the use of ion exchange adsorption methods employing the resin Dowex-50. The element 98 isotope appears in the eka-dysprosium position on elution curves containing berkelium and curium as reference points--that is, it precedes berkelium and curium off the column in like manner that dysprosium precedes terbium and gadolinium. The experiments so far have revealed only the tripositive oxidation state of eka-dysprosium character and suggest either that higher oxidation states are not stable in aqueous solutions or that the rates of oxidation are slow. The successful identification of so small an amount of an isotope of element 98 was possible only through having made accurate predictions of the chemical and radioactive properties