EPDM O-rings of gate valves employed for the construction of a second-generation accelerator for the production of neutron-rich Radioactive Ion Beams were studied in order to assess their sealing ...performance both during the facility service time and the post-service storage phase. Several O-ring specimens were at first exposed to different dose levels of mixed neutron and gamma radiations. Correspondent modifications of physical and mechanical properties of the material were investigated by means of uniaxial tensile tests, dynamic mechanical analyses, aging, compression set and vacuum leak tests. A hyperelastic strain energy function was adopted to fit the mechanical response of the material as a function of the absorbed dose. The minimum squeeze degree that guarantees O-ring sealing efficiency at different irradiation levels was determined by varying the interference between O-rings and grooves. A finite element model of the vacuum leak test was then set up to assess the contact pressure level required to ensure sealing. Numerical simulations of the gate valve main O-ring were subsequently carried out. By comparison of the predicted contact pressure and strain levels with experimental results, a life prediction map, as function of the service time, the storage time and the O-ring squeeze degree, was proposed.
Display omitted
•Study of mechanical properties evolution of EPDM irradiated with neutron and gamma mixed fields at different dose levels.•Identification of structural and functional O-Ring end-points as function of the absorbed dose level (service time).•Study of the sealing performance of the target chamber gate valve in a new generation radioactive ion beam source.•Definition of gate valve O-Ring life prediction map as function of service time, storage time and squeeze degree.
The aim of the SPES (Selective Production of Exotic Species) project is to provide high intensity and high-quality beams of neutron-rich nuclei to perform forefront research in nuclear structure, ...reaction dynamics and interdisciplinary fields like medical, biological and material sciences. SPES is a second generation ISOL radioactive ion beam facility, part of the INFN Road Map for the Nuclear Physics and supported by the italian national laboratories LNL (Legnaro) and LNS (Catania). It represents an intermediate step toward the future generation European ISOL facility EURISOL. It is based on the ISOL method with an UCx Direct Target able to sustain a power of 10 kW. The primary proton beam will be delivered by a Cyclotron accelerator with an energy of more then 40 MeV and a beam current of 200 μA. Neutron-rich radioactive ions will be produced by Uranium fission at an expected fission rate in the target of the order of 1013 fissions per second. The exotic isotopes will be re-accelerated by the ALPI superconducting LINAC up to energies of 10-13 AMeV, for masses in the region of A=130 amu, with an expected rate on the secondary target of 108 pps.
SPES (Selective Production of Exotic Species) is an INFN project to develop a Radioactive Ion Beam (RIB) facility as an intermediate step toward EURISOL. The SPES project is part of the INFN Road Map ...for the Nuclear Physics development in Italy and is supported by the whole Italian Nuclear Physics community and mainly by LNL and LNS the INFN National Laboratories of Nuclear Physics in Legnaro and Catania. The Laboratori Nazionali di Legnaro (LNL) was chosen as the site for the facility construction due to the presence of the PIAVE-ALPI accelerator complex, which will be used as re-accelerator for the RIBs. The SPES project is based on the ISOL method with an UCx Direct Target and makes use of a proton driver of at least 40 MeV energy and 200 microA current. Neutron-rich radioactive beams will be produced by Uranium fission at an expected fission rate in the target in the order of 1013 fissions per second. The key feature of SPES is to provide high intensity and high-quality beams of neutron rich nuclei to perform forefront research in nuclear structure, reaction dynamics and interdisciplinary fields like medical, biological and material sciences. The exotic isotopes will be re-accelerated by the ALPI superconducting linac at energies up to 10AMeV for masses in the region of A=130 amu with an expected rate on target of 109 pps.
Porous lanthanum carbide disks were prepared from La2O3 and graphite powders and with additions of polymeric fibers as sacrificial templates for the formation of interconnected channels of enhanced ...permeability to gas flow. Two kind of fibers were used (Nylon 6,6 and polypropylene) characterized by an average length of 500µm and diameters of 18 and 20µm, respectively. The fiber content was varied up to 21.3vol% for nylon or up to 24.8vol% for PP in order to control the porosity and the permeability level of bodies. The fiber-derived porous LaCx samples exhibited higher total porosity (38.0–51.7% for PP and 42.9–55.3% for nylon) compared to standard LaCx where porosity (35.7%) was generated only by the carbothermal reaction during sintering. A 50-fold increase in the Darcian permeability coefficient k1 and a 1200-fold increase in the non-Darcian coefficient k2 were achieved in comparison with the permeability level of the composition without fibers (k1=1.21×10−15m2 and k2=1.17×10−11m). Nylon was slightly better than PP to enhance permeability of LaCx targets.
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.
A systematic study of the indiffusion of oxygen in germanium induced by pulsed laser melting (PLM) is reported. In order to evidence the impact of the experimental parameters, different processing ...conditions have been compared, i.e. with or without pre-PLM etching of the Ge native oxide by H2O or HF dip, Air or N2-rich atmosphere, and single or multi-pulse PLM. Oxygen indiffusion is always observed with surface concentration above 1 × 1019 cm−3 for all the processing conditions. Pre-PLM surface chemical treatments seem to have no significant influence in terms of the oxygen penetration, although HF allows lower surface roughening. On the contrary, a processing atmosphere with reduced oxygen concentration is more efficient in reducing the overall O indiffusion. The present experimental results are crucial in view of the implementation of the PLM technique for highly doped Ge as well as to design studies where contamination issue might be crucial.
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.
Study of isotopes production for the SPES project Andrighetto, A.; Li, J.; Petrovich, C. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
05/2003, Letnik:
204
Journal Article
Recenzirano
The Monte Carlo calculations for the isotopes production in the UCx target (SPES project) are considered. The fragments are generated from the fission of
238U, using fast neutrons coming from a ...converter target (two target scheme). The neutron production yields from the converter target, as well as the energy and angular distributions from different material targets have been investigated. In all simulations, using the MCNPX code, we refer to a proton primary beam at 100 MeV energy, 1 mA, 100 kW power on the converter. The number of fissions (about 10
13 fissions/s) and the production rates of neutron-rich nuclei were calculated for different converter materials.
Lanthanum carbide is considered as a potential target for generation of radioactive ion beams by means of the ISOL (Isotope Separation On Line) technique. This method requires the use of porous ...refractories as targets, in order to work in extreme conditions (more than 2000°C in high vacuum) to enhance the release of the generated isotopes. Several techniques can be used to generate open interconnected porosity in lanthanum carbide. The use of polymeric (nylon and polypropylene) fibers as sacrificial fillers was successfully tested in a previous work. Here, the effect of the fibers length is reported and discussed in terms of porosity and permeability.
PDF
