Abstract
At the SPES (Selective Production of Exotic Species) facility, intense Radioactive Ion Beams (RIBs) are produced by the interaction of a 40 MeV proton beam with a multi-foil uranium carbide ...target employing the Isotope Separation On-Line (ISOL) technique. The Target Ion Source (TIS) unit constitutes the core of the isotope production process. TIS units are replaced on a periodic basis during operation to maintain high performance. An automated storage system has been designed to accept highly radioactive TIS units and house them during a cooling period prior to decommissioning. The system is conceived to meet strict functional and safety requirements. Its peculiar design allows for improved reliability and availability during critical operations, as well as minimization of staff exposure to ionizing radiation during maintenance tasks. This contribution describes the design and control architecture of the Temporary Storage System (TSS). The equipment is part of a structured framework of remote manipulation, consisting of various machines interlocked with the Access Control System (ACS) and the Machine Protection System (MPS).
SPES (Selective Production of Exotic Species) is a second generation facility for the production of radioactive ion beams that is going to be commissioned at the Laboratori Nazionali di Legnaro of ...INFN at Legnaro, Padua, Italy. Radioactive neutron-rich isotopes are expected to be produced by nuclear fission induced by a 40 MeV, 200 μA primary proton beam impinging on a
UC
target. The expected reaction rate is about 10
fission/s. Radioactive ion beams are produced using the isotope separation on-line technique. The production of such an amount of radioactive species raises radiological issues throughout the life cycle of the facility. A study of the radioactive contamination of the components of the radioactive ion beam line is performed with the FLUKA Monte Carlo simulation code, under realistic hypotheses for the produced isobaric beams. The present results complete previous studies focused on the radiological impact of the production target irradiation, the residual activation of the primary proton beam line and the radioactive contamination of the ion source complex. The overall ambient dose equivalent rate due to the different radiation sources is calculated at several positions inside the production bunker and at different times after a typical one-year operating period of the facility with the
UC
target at full power. The obtained results and the developed methodology provide the guidelines and the needed tools to plan ordinary and extraordinary interventions as well as final decommissioning of the SPES facility.
The SPES laser ion source has been tested at ISOLDE Offline 2, CERN. A two-step single resonance photo-ionization scheme has been used to ionize gallium atoms in the SPES tantalum hot-cavity ion ...source. The ion beam time structure, laser enhancement of ion yield, and ionization efficiency are investigated in relation to the ion source temperature and ion load. From the time structures, it is inferred that a significant fraction of the extracted ions are generated in the transfer line rather than just in the hot cavity. The effect of the electrostatic axial field on the movement of ions inside the ion source is discussed. Generally, there is an inverse relationship between total ion load and the laser enhancement factor. This dependency is enhanced at lower operating temperature of the ion source. This is explained by the influence of thermionic electron emission and ion density on the transverse laser-ion confinement, and therefore the survival of ions as they drift towards the extraction region of the ion source. At 2200 °C, the nominal temperature for on-line operation of the ion source, the ratio of laser-ionized to surface-ionized gallium was stable around 55 during the measurement campaign, and independent of the total extracted ion current up to the measured value of 1.1 μA. A resonance laser ionization efficiency value of 27.2% for gallium has been measured.
Abstract
Graphite is widely used in industrial applications, thanks to its excellent high temperature resistance. Therefore, its mechanical strength under combined stress at high temperature is an ...important issue for structural design. This work reports biaxial compressive data of an isotropic ultrafine grain graphite, the POCO EDM-3. Uniaxial tests have been first performed at room temperature with plane specimens, in order to obtain the stress strain curve for this material. Compressive tests have been then carried out with different notched geometries, both at room temperature and at 1000°C, in order to evaluate the biaxial compressive strength. Since plastic deformation was observed in uniaxial compressive tests with plane samples, elastic-plastic simulations have been performed with the FE code Ansys®, in order to assess the stress state at failure. The applicability of the Von Mises yield criterion has been evaluated, by comparing the equivalent Von Mises stresses at failure in different notched geometries. The tests demonstrated that, at room temperature, this type of graphite plastically deform in compression and that the Von Mises criterion can be used in order to evaluate the stress state. Moreover, the comparison between the failure loads at room temperature and at 1000°C showed that the resistance increases as the temperature increases.
Karyotype and chromosomal characteristics from 3 allopatric populations of Hoplias malabaricus, cytogenetically the most studied Erythrinidae taxon, were investigated using different staining ...techniques (C-, Ag-, and CMA(3) banding) as well as fluorescent in situ hybridization (FISH) to detect 18S rDNA, 5S rDNA, and 5SHindIII satellite DNA sites. The isolation, cloning and characterization of an 18S rDNA probe from H. malabaricus genome were also performed for the first time in order to develop a more specific probe. The 3 populations, named PR, CR, and DR, showed identical karyotypes, with 2n = 42 chromosomes composed of 11 m pairs and 10 sm pairs, without heteromorphic sex chromosomes, which characterize the populations as belonging to karyomorph A. In all populations C-positive heterochromatin was situated in the centromeric/pericentromeric regions of the chromosomes, as well as in the telomeric region of several pairs. A conspicuous proximal heterochromatic block on the long arm of pair No. 16 was the only GC-rich segment in the karyotypes. 5SHindIII satellite DNA was always mapped in the centromeric region of several chromosomes. The 18S rDNA sites were situated on the telomeric or centromeric regions, whereas the 5S rDNA showed an interstitial or proximal location in some pairs. Several chromosomes bearing these repetitive DNA sequences were shared by the 3 populations, alongside with some exclusive chromosomal markers. In this sense, population CR was the most differentiated one, including a syntenic condition for the 18S and 5S rDNA probes, as confirmed by double FISH. Thus, despite their inclusion in the same major karyotypic group, the distinct populations cannot be considered an absolute evolutionary unit, as evidenced by their inner chromosomal differentiations.
Karyotypic and cytogenetic characteristics of catfish Harttia carvalhoi (Paraíba do Sul River basin, São Paulo State, Brazil) were investigated using differential staining techniques (C-banding, ...Ag-staining) and fluorescent in situ hybridization (FISH) with 18S and 5S rDNA probes. The diploid chromosome number of females was 2n = 52 and their karyotype was composed of nine pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric and four pairs of acrocentric chromosomes. The diploid chromosome number of males was invariably 2n = 53 and their karyotype consisted of one large unpaired metacentric, eight pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric, four pairs of acrocentric plus two middle-sized acrocentric chromosomes. The differences between female and male karyotypes indicated the presence of a sex chromosome system of XX/XY1Y2 type, where the X is the largest metacentric and Y1 and Y2 are the two additional middle-sized acrocentric chromosomes of the male karyotype. The major rDNA sites as revealed by FISH with an 18S rDNA probe were located in the pericentromeric region of the largest pair of acrocentric chromosomes. FISH with a 5S rDNA probe revealed two sites: an interstitial site located in the largest pair of acrocentric chromosomes, and a pericentromeric site in a smaller metacentric pair of chromosomes. Translocations or centric fusions in the ancestral 2n = 54 karyotype is hypothesized for the origin of such multiple sex chromosome systems where females are fixed translocation homozygotes whereas males are fixed translocation heterozygotes. The available cytogenetic data for representatives of the genus Harttia examined so far indicate large kayotype diversity.
The genus
Piabucus
is the only member of the subfamily Iguanodectinae found in the Pantanal of Mato Grosso State, where it is represented by
Piabucus melanostomus. P. melanostomus
from the Paraguay ...and Bento Gomes Rivers of the Pantanal wetlands were analysed using conventional and molecular cytogenetic techniques to cytogenetically characterise the species and broaden the knowledge of the subfamily. The results indicated no sex-related heteromorphisms. The diploid number for the species was 2n = 50 chromosomes, which were divided into six metacentric, eight submetacentric, 24 subtelocentric, and 12 acrocentric with a fundamental number (FN) of 88. Heterochromatin was visualised using the C-banding technique, which showed that it was mainly distributed in the centromeric and pericentromeric region of most chromosomes, but larger blocks were observed on the long arms of large subtelocentric chromosomes (8, 9, 10, 13, and 20 pairs). Nucleolar organising regions (Ag-NOR) were observed in the p-subterminal region of one subtelocentric chromosome pair (9) with a remarkable size polymorphism between homologues in individuals from the Paraguay River, which was confirmed using the FISH technique with 18S rDNA. In this population, in all individuals studied, one of the homologous shows block considerably larger. The karyotype was compared with those of other subfamilies considered basal in Characidae, according to morphological data.
Over the past decades many accelerator facilities have been built in order to produce radioactive nuclei. Among the falcility under construction, SPES (Selective Production of Exotic Species) is the ...Italian ISOL (Isotope Separation On Line) facility in the installation phase in these years in the Laboratori Nazionali di Legnaro. The innovative aspect of this facility is that the radioactive beam produced by fission induced by the proton beam, produced by a high power cyclotron, interact with a multi-disks uranium carbide target. The formed RIB will be sent directly to the low energy experimental area and, afterwards, to the post-acceleration complex. Currently the installation program concerning the SPES RIB source provides the set-up of the apparatus around the production bunker. The main objective of SPES project is to provide, in the next years, the first low-energy radioactive beams for beta decay experiments using the b-DS (beta Decay Station) set-up and for radiopharmaceutical applications by means of the IRIS (ISOLPHARM Radioactive Implantation Station) apparatus. In this work, all the specific issues related to the SPES RIB and the Low Energy beam lines will be reported. The main RIB systems, such as ion source systems, target-handling devices and the installation of low energy transport line, will be presented in detail.
Abstract A two-step resonance photo-ionization scheme has been used to ionize samarium atoms in the SPES tantalum hot-cavity ion source. The effect of the ion load on the ion beam time structure and ...the laser enhancement of the ion yield has been studied at different ion source temperatures. Generally, the introduction of more positive ions (ion load) affects negatively the overall confinement of the laser ions inside the volume of the ion source. Possible enhancement of the laser ion confinement through the introduction of neutrals is observed as well. The ion load is also observed to affect the confinement in the transfer line much more than in the hot cavity. Measurement of the time structure with inverted polarity of the cavity DC heating supply confirmed the significance of the longitudinal potential for ion extraction. The laser enhancements of the ion yield are found to be sensitive to the ion load at low operating temperature of the ion source i.e. 1800°C, whereas at 2050°C and 2200°C, they are relatively stable till an ion load value of 1.2 µA.
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