Search results for "EVAPORATION"
showing 10 items of 175 documents
Electrolytic preparation of actinide filaments for laser resonance ionization spectroscopy
1993
Abstract For the determination of trace amounts of actinide elements by resonance ionization mass spectroscopy, atomic beams of these elements are produced by evaporation from rhenium substrates. The actinides are deposited by electrolysis as hydroxides in a 2 mm spot on a rhenium foil and covered electrolytically with a thin layer of rhenium or platinum. During heating of such a sandwich reduction occurs to the metallic state while diffusing through the overplated layers and the actinides are evaporated as atoms from the surface. With lead-doped platinum, efficient release is observed already at 1700°C in contrast to rhenium where 2100°C is required and a higher background is produced.
Improved ion guide for heavy-ion fusion-evaporation reactions
1998
The ion guide for heavy-ion-induced reactions developed originally for the SARA facility in Grenoble has been implemented at the Jyvaskyla IGISOL facility. For the Cd-116(Ar-40, 6n)Dy-150 reaction an efficiency of 0.5% relative to the number of reaction products entering the stopping chamber was obtained. This is 3.5 times higher than previously obtained at SARA and corresponds to a yield of about 100 ions/(p mu C mb). Mass-separated yields for the Ar-36 + Mo-92 and Ar-36 + Mo-94 reactions were measured. (C) 1998 Elsevier Science B.V. All rights reserved.
Alpha decay of the new isotopes207, 208Ac
1994
Two new neutron-deficient isotopes207,208Ac have been produced in fusion reactions with 5.2–5.6 MeV/nucleon40Ar ions on175Lu and identified on the basis of genetic correlations. The fusion evaporation products were separated on-line using a gas-filled magnetic recoil separator. The alpha energy and half-life of208Ac were determined to be (7572±15) keV and (95 −16 +24 ) ms, respectively. A new alpha line with a half-life of (25 −5 +9 ) ms and an energy of (7758±20) keV is assigned to the decay of an isomeric state in208Ac. Another new activity with a half-life of (22 −9 +40 ) ms and an alpha energy of (7712±25) keV is assigned to207Ac.
Absolute transmission and separation properties of the gas-filled recoil separator RITU
2011
Abstract The absolute transmission values of the RITU gas-filled recoil separator have been measured for several fusion evaporation products. Three different beams and several targets were used to create fusion evaporation residues in mass region A =170–190 mainly in neutron evaporation channels. Measured absolute transmission values from around 7% up to round about 90% have been observed for very asymmetric and symmetric reactions, respectively. For the reactions studied it was observed that the angular spread of products after the target and the angular acceptance of RITU determine the transmission probability relatively accurately. Magnetic rigidities and equilibrium charges of the produ…
Speeding up liquid-phase heavy element chemistry: Development of a vacuum to liquid transfer chamber (VLTC)
2021
Abstract We present a new system, which is suitable for performing fast liquid phase chemistry experiments and gives access to shorter-lived isotopes of super heavy elements (SHE) than accessible with current techniques. With this novel vacuum to liquid transfer chamber (VLTC), which is mounted behind a physical preseparator, the desired isotopes are transported from the low-pressure side of the recoil separator directly into the liquid phase of a chemical experiment. Simulations on the kinematics of evaporation residues were performed using SRIM, validating the general plausibility of the VLTC concept. Subsequently, the feasibility was demonstrated with 250 , 252 Cf fission fragments, whic…
Characterization of deuteride titanium targets used in neutron generators
2000
Abstract The study of the physicochemical characteristics of titanium thin films and the corresponding deuterium absorption/desorption kinetics was performed. In order to optimize the production of high-energy neutrons the behaviour of deuteride titanium targets has been studied experimentally by bombardment with 120 and 350 kV deuterons by means of electrostatic accelerators. The importance of the deposit evaporation conditions on the efficiency of neutron emission is clearly demonstrated as well as the thermomechanical stability of the Ti thin film by deuteron bombardment. The main parameters involved in the targets behaviour have been discussed from a thermodynamical approach.
Correlation between the spatial distribution of the circumstellar disks and the massive stars in the open cluster NGC 6611. Compiled catalog and clus…
2006
Context: the observation of young stars with circumstellar disks suggests that the disks are dissipated, starting from the inner region, by the radiation of the central star and eventually by the formation of rocky planetesimals, over a time scale of several million years. It was also shown that strong UV radiation emitted by nearby massive stars can heat a circumstellar disk up to some thousand degrees, inducing the photoevaporation of the gas. This process strongly reduces the dissipation time scale. Aims: we study whether there exists a correlation between the spatial distribution of stars with circumstellar disks and the position of massive stars with spectral class earlier than B5, in …
Crushing of Interstellar Gas Clouds in Supernova Remnants: the Role of Thermal Conduction and Radiative Losses
2004
We model hydrodynamic interactions of an old supernova remnant shock wave with a small interstellar gas cloud, taking into account the effects of thermal conduction and radiative losses. In particular, we consider a representative case of a Mach 30 shock impacting on an isolated cloud with density contrast χ = 10 with respect to the ambient medium. Thermal conduction appears to be effective in suppressing the Kelvin-Helmholtz and Rayleigh-Taylor instabilities which would develop at the cloud boundaries. We demonstrate that the radiative losses play a crucial role in the dynamics of the shock-cloud interaction, dominating evolution of the shocked cloud medium.
Black Hole Evaporation by Thermal Bath Removal
1996
We study the evaporation process of 2D black holes in thermal equilibrium when the incoming radiation is turned off. Our analysis is based on two different classes of 2D dilaton gravity models which are exactly solvable in the semiclassical aproximation including back-reaction. We consider a one parameter family of models interpolating between the Russo-Susskind-Thorlacius and Bose-Parker-Peleg models. We find that the end-state geometry is the same as the one coming from an evaporating black hole formed by gravitational collapse. We also study the quantum evolution of black holes arising in a model with classical action $S = {1\over2\pi} \int d^2x \sqrt{-g} (R\phi + 4\lambda^2e^{\beta\phi}…
Use of Heating Configuration to Control Marangoni Circulation during Droplet Evaporation
2022
The present work presents a numerical study of the evaporation of a sessile liquid droplet deposited on a substrate and subjected to different heating configurations. The physical formulation accounts for evaporation, the Marangoni effect, conductive transfer in the support, radiative heating, and diffusion–convection in the droplet itself. The moving interface is solved using the Arbitrary Lagrangian–Eulerian (ALE) method. Simulations were performed using COMSOL Multiphysics. Different configurations were performed to investigate the effect of the heating conditions on the shape and intensity of the Marangoni circulations. A droplet can be heated by the substrate (different natures and thi…