1,721,038 research outputs found
A Compact Neutron Beam Generator System Designed for Prompt Gamma Nuclear Activation Analysis
No full textIn this work a compact system was designed for bulk sample analysis using the technique of PGNAA. The system consists of 252Cf fission neutron source, a moderator/reflector/filter assembly, and a suitable enclosure to delimit the resulting neutron beam. The moderator/reflector/filter arrangement has been optimised to maximise the thermal neutron component useful for samples analysis with a suitably low level of beam contamination. The neutron beam delivered by this compact system is used to irradiate the sample and the prompt gamma rays produced by neutron reactions within the sample elements are detected by appropriate gamma rays detector. Neutron and gamma rays transport calculations have been performed using the Monte Carlo N-Particle transport code (MCNP5)
Apparecchiatura per la produzione endogena di radioisotopi, particolarmente per diagnostica tomografica ad emissione di positroni.
No full textApparecchiatura per la produzione di radioisotopi a vita breve tramite tecnologie Plasma Focus. I radioisotopi interessati sono il F-18, O-15, N-13 e F-1
Wave propagation and "Landau-type" damping from Bohm potential
No full textFrom Bohm’s interpretation of Quantum Mechanics, a quantum kinetic equation (QKE) can be derived. It is found that waves propagate in force-free gases of non interacting particles, only due to Bohm potential. In the present article the existence of Landau damping in such propagations is investigated. It is found that Bohm potential alone gives indeed rise to damping entirely analogous to classical Landau damping, both for bosons and for weakly degenerate fermions
A Kinetic Approach to the Calculation of Surface Tension of a Spherical Drop
No full textIn literature, surface tension has been investigated mainly from a Thermodynamics standpoint, more rarely with kinetic methods. In the present work, surface tension of drops is studied in the framework of kinetic theory, starting from the Sutherland approximation to Van Der Waals interaction between molecules. Surface tension is calculated as a function of drop radius: it is found that it approaches swiftly an asymptotic value, for radii of several times the distance of minimum approach D of the Sutherland potential. This theoretical asymptotic value is compared to experimental values of surface tension in plane surfaces of a few liquids, and is found in reasonable agreement
A transport theory approach to percolation of liquids through porous media
No full text05.60.Cd Classical transport, 05.20.Dd Kinetic theory,
Device for the Endogenous Production od Radioisotopes, Particularly for PET
No full textDevice for the endogenous production of radioisotopes, particularly for PET, characterized as comprising:
a vacuum chamber, whose inner surface be treated totally or partially to resist ion implantation,
a pair of electrodes placed inside said vacuum chamber,
a capacitor bank,
means to connect said capacitor bank to said electrodes to generate between the latter an electrical discharge, thus generating a plasma and creating conditions for the unfolding of nuclear reactions that generate isotopes,
an overall inductance of the equivalent electric circuit of such device not exceeding 50 nH,
means attached to said vacuum chamber for the creation of a vacuum not higher than 10-6 torr,
means attached to said vacuum chamber for the insertion, after creating the vacuum, of at least one reaction gas at a pressure apt to guarantee creation of the plasma during discharge and subsequent obtention of confinement conditions of such plasma, and
means attached to said vacuum chamber for the extraction of gas and is storage into a gas chromatographic cylinder
Comparison of Stretched and Sitting Configurations for Partial Body Measurements
No full textThe current partial-body counter installed at KIT is under redesign in order to add whole-body counting capabilities and to replace the current phoswich detectors with HPGe detectors, also able to detect low energy photons (210Pb, 241Am). Dierent configurations for the positioning of the subject have been tested with the aid of Monte Carlo simulations and the performances attainable with a sitting and a lying configuration were compared. The optimal placement of the detectors was also defined. The simulations were used not only to estimate the counting eciencies, but also to estimate the Compton
scattering produced by 40K, then used to calculate the minimum detectable activities
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A range-based method to calibrate a magnetic spectrometer measuring the energy spectrum of the backward electron beam of a plasma focus
No full textThe electron beam emitted from the back of plasma focus devices is being studied as a radiation source for intraoperative radiation therapy applications. A plasma focus device is being developed for this purpose, and there is a need for characterizing its electron beam, particularly, insofar as the energy spectrum is concerned. The instrument used is a magnetic spectrometer. To calibrate this spectrometer, a procedure relying on the energy-range relation in Mylar R has been devised and applied. By measuring the transmission through increasing thicknesses of the material, electron energies could be assessed and compared to the spectrometer readings. Thus, the original calibration of the instrument has been extended to higher energies and also to better accuracy. Methods and results are presented
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