Search results for "IONIZATION"
showing 10 items of 1255 documents
Evolution of the electronic properties of graded poly(thienylene vinylene)-poly(pyrrylene vinylene) mixed copolymers
1993
Abstract We present a valence effective Hamiltonian (VEH) theoretical investigation of the evolution of the electronic properties of poly(thienylene vinylene)-poly(pyrrylene vinylene) mixed copolymers as a function of the unit cell content on the basis of ab initio 3–21G∗ and 3–21G optimized geometries. As a consequence of the strong localization of the LUCO both electron affinity and bandgap deviate from a linear dependence, and only the ionization potential presents the expected values.
VEH electronic band structure of poly(phenylsilane)
1993
Abstract The electronic structure of all-trans syndiotactic and isotactic poly(phenylsilane) has been calculated using the valence effective Hamiltonian (VEH) method. The effects of attachment of the phenyl group on the electronic properties of polysilane are analysed in detail. The VEH results show a decrease of ionization potential and an increase of electron affinity which determine an important reduction of the bandgap. These features are correlated with σ−π and σ ∗ −π ∗ interactions between the silicon backbone and the phenyl group.
Comparison of two portable solid state detectors with an improved collimation and alignment device for mammographic x-ray spectroscopy
2006
We describe a portable system for mammographic x-ray spectroscopy, based on a 2 X 2 X 1 mm3 cadmium telluride (CdTe) solid state detector, that is greatly improved over a similar system based on a 3 X 3 X 2 mm3 cadmium zinc telluride (CZT) solid state detector evaluated in an earlier work. The CdTe system utilized new pinhole collimators and an alignment device that facilitated measurement of mammographic x-ray spectra. Mammographic x-ray spectra acquired by each system were comparable. Half value layer measurements obtained using an ion chamber agreed closely with those derived from the x-ray spectra measured by either detector. The faster electronics and other features of the CdTe detecto…
Ion production from solid state laser ion sources.
2010
Laser ion sources based on resonant excitation and ionization of atoms are well-established tools for selective and efficient production of radioactive ion beams. Recent developments are focused on the use of the state-of-the-art all solid-state laser systems. To date, 35 elements of the periodic table are available from laser ion sources based on tunable Ti:sapphire lasers. Recent progress in this field regarding the establishment of suitable optical excitation schemes for Ti:sapphire lasers are reported.
SU-E-T-691: Shielding Evaluation of a Treatment Room with An Electronic Brachytherapy System
2015
Purpose: Esteya™ (Elekta) is a brachytherapy electronic system used for treating skin cancer lesions. This unit is based on a 69.5 kV X-ray source and a surface applicator which produces a circular beam of a specific diameter, which varies from 1 to 3 cm. This study aims to establish the radiation protection measures for the system. Methods: A characterization of the scattered and leakage radiation of the system was implemented by means of experimental measurements. The scattered radiation measurements were performed with a Berthold LB133 ionization chamber, evaluating the dose rate for different distances from the applicator surface. The patient was simulated through water equivalent solid…
Design and characterization of a new high-dose-rate brachytherapy Valencia applicator for larger skin lesions
2016
Purpose: The aims of this study were (i) to design a new high-dose-rate (HDR) brachytherapy applicator for treating surface lesions with planning target volumes larger than 3 cm in diameter and up to 5 cm in size, using the microSelectron-HDR or Flexitron afterloader (Elekta Brachytherapy) with a 192Ir source; (ii) to calculate by means of the Monte Carlo(MC) method the dose distribution for the new applicator when it is placed against a water phantom; and (iii) to validate experimentally the dose distributions in water. Methods: The penelope2008MC code was used to optimize dwell positions and dwell times. Next, the dose distribution in a water phantom and the leakage dose distribution arou…
First Determination of the Ionization Potential of Americium and Curium
1995
First successful ionization of Lr (Z = 103) by a surface-ionization technique.
2013
We have developed a surface ionization ion-source as part of the JAEA-ISOL (Isotope Separator On-Line) setup, which is coupled to a He/CdI2 gas-jet transport system to determine the first ionization potential of the heaviest actinide lawrencium (Lr, Z = 103). The new ion-source is an improved version of the previous source that provided good ionization efficiencies for lanthanides. An additional filament was newly installed to give better control over its operation. We report, here, on the development of the new gas-jet coupled surface ion-source and on the first successful ionization and mass separation of 27-s (256)Lr produced in the (249)Cf + (11)B reaction.
Release Studies of Atomic Technetium
1991
Application of a laser ion source (LIS) is a promising new technique for trace analysis with high efficiency and selectivity. One of the problems which can limit its efficiency attained in practice is the adsorption of sample atoms on the hot walls of the LIS cavity. We have studied the release of atomic technetium from different wall materials at temperatures up to 2500 K. For these investigations resonance ionization of technetium atoms applying a copper vapour pumped dye laser system and γ-spectrometry of 6-h 99mTc have been used. Theoretical calculations of the heat of desorption for technetium on different wall materials are presented and compared with experimental data. Though the res…