A 2.45 GHz electron cyclotron resonance (ECR) ion source with a single mode resonator is being developed to produce high efficient single charged ion beams from exiguous gaseous elements. The source is intended to produce short and long half-life radioactive ion beams as well as stable ion beams for low and high energy experiments at ISAC [J. M. Poutissou, Proceedings of the ISAC Workshop (1994)]. It is obvious that for the radioactive ion beam production, the gas and ion transient time and the overall ionization efficiency are the most important parameters. The transient time is measured using ultrafast peizoelectric gas valve which could operate up to a frequency of 2 kHz. A unique feature of the source is that the plasma chamber is considerably smaller (∼170 times) than its resonance cavity in order to minimize the transient time. Quartz tubes with various diameters (5–20 mm) and 80 mm long are tested as the plasma chamber and the results are discussed. The effect of the transfer tube length, which links the target and the ion source on the transient time is also described. An axially symmetric five electrode extraction system containing three multiaperture electrodes was used to extract the beam. The source, including ECR coils and extraction system is placed in the middle of a 60 cm×60 cm×90 cm vacuum box to simulate the ISAC target module conditions. The preliminary results of the molecular and ion transient time studies, beam efficiency studies are also presented in this article.
Abstract. The nuclear incoherent 71" photoproduction cross section from '^C is evaluated at forward angles in the 4.0 to 6.0 GeV energy range using the multicoUisional intranuclear cascade model MCMC. The model incorporates some improvements in comparison with previous versions associated with the momentum distribution (MD) for light nuclei -extracted from the available (e,e'p) data -as well as the evaluation of the shadowing effects during the photonucleus interaction. The final results of the single and double differential cross sections at forward angles are very sensitive to the MD parameterizations due to the Pauli principle, which largely suppresses the cross sections for low momentum transfer. The attenuation of the nuclear cross section due to pion -nucleus final state interactions is approximately 40% (without nuclear shadowing), which is in nice agreement with the predictions from the Glauber model. The single and double 71" differential cross sections are presented for possible applications for the interpretation of the inelastic background in the PrimEx experiment at the Jefferson Laboratory.
No abstract
Microsymposia C171MS pseudopotentials (projected augmented waves, PAWs). The calculated ρ(r) function is equidistant 3D grid. The dimension of 3D grid can be easily adjusted by internal keywords of the VASP program and it is limited by the size of the system RAM only.To compare the experimental and theoretical ρ(r) functions we carried out the high-resolution X-ray studies and DFT calculations of crystal structures of coordination compounds containing group 14 elements. The present work covers the results obtained for two complexes with formally divalent Ge and Sn and six formally tetravalent Si, Ge and Sn. We used the ρ(r) function calculated for the corresponding isolated molecules as reference points to evaluate the influence of crystal packing and possible systematic errors. The topological parameters (the values of ρ(r), its Laplacian (∇ 2 ρ(r)), kinetic and potential energy densities) in CP(3,-1) were compared. The most prominent differences are revealed for the ∇ 2 ρ(r) values. The latter are defined by dimension of 3D grid. On the other hand, the values of atomic volumes and charges are in good agreement. In our opinion the usage of our methodology is allowed to investigate the chemical bonding in any crystal with volume of the unit cell to be up to 4000-5000 Å 3 . Depending on photon flux and sample quality, repetition rates of about 100 Hz can be realized for the XANES range. A new optimized monochromator enables the acquisition of full high quality EXAFS spectra with a scan range of typically 1 keV -up to about 2.5 keV -in only 50 ms per spectrum. This setup employs a channel cut crystal, a cam driven tilt table for rapid angular oscillations and a novel fast readout system for the Bragg angle. Latest developments also allow a user friendly variation of the scanned energy range within experiments by remote control [5]. Since a fast sequential energy scanning technique is used, the detection of fluorescence radiation or surface sensitive techniques like X-ray reflection measurements can be applied. A reference sample can be monitored simultaneously with each measurement to detect minor edge shifts reliably. Even XANES microtomography becomes feasible, using the fast scanning monochromator with refractive X-ray lenses for beam focusing. Using cryogenic cooling, the monochromator crystal can cope with the full heat load from third generation undulator sources, and excellent data quality can be obtained. Currently, a new dedicated setup using an insertion device at the PETRA III storage ring (DESY, Hamburg, Germany) is under development. KeywordsHowever, such measurements require very fast high precision detection systems with low noise level, and the photon energy at each instant must be known with high accuracy. Special care is necessary to avoid dynamic distortions of the measured absorption spectra.In addition, the high data acquisition rates make special software developments necessary for fast continuous measurements [6].The most recent technical developments of fast XAFS measurements, the current s...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.