Target materials for exotic ISOL beams Gottberg, A.
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
06/2016, Letnik:
376
Journal Article
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The demand for intensity, purity, reliability and availability of short-lived isotopes far from stability is steadily high, and considerably exceeding the supply. In many cases the ISOL (Isotope ...Separation On-Line) method can provide beams of high intensity and purity. Limitations in terms of accessible chemical species and minimum half-life are driven mainly by chemical reactions and physical processes inside of the thick target. A wide range of materials are in use, ranging from thin metallic foils and liquids to refractory ceramics, while poly-phasic mixed uranium carbides have become the reference target material for most ISOL facilities world-wide. Target material research and development is often complex and especially important post-irradiation analyses are hindered by the high intrinsic radiotoxicity of these materials. However, recent achievements have proven that these investigations are possible if the effort of different facilities is combined, leading to the development of new material matrices that can supply new beams of unprecedented intensity and beam current stability.
Abstract The FEBIAD ion source is routinely used to produce radioactive ions of halogens, molecules, and noble gases in several ISOL facilities worldwide. At TRIUMF, an extensive numerical and ...experimental campaign has been performed to fundamentally understand the source while improving its reliability and overall performance. Particularly, the cathode temperature has been studied by pyrometric measurements, Schottky analysis and numerical simulations to properly understand the electron emission driving the ionization. The temperature values found are consistent within the error bars and confirm the equivalence of the methodologies used. The findings can be used as part of a numerical ionization model for more realistic electron emission and the benchmarked thermal model can be used to propose novel and more robust geometries.
Abstract The ISAC-FEBIAD is an electron impact ion source typically used to ionize radioactive molecules or isotopes of elements beyond the reach of either surface or laser ion sources. The FEBIAD’s ...key tuning parameters are the cathode temperature defining the number of electrons created; the anode voltage establishing the electron energy; and the magnetic field controlling the electron density inside the anode volume. However, these parameters are typically scanned in a small and limited range when optimizing the source. Recent investigations have shown the need to explore the entire range of operational values accessible by the power supplies, not only due to the intrinsic variations from source to source but also to operate the source at optimal settings. To address this, a scanning algorithm has been implemented as a web interface thanks to the High-Level-Application (HLA) infrastructure available at TRIUMF. The ion beam intensity during both offline and online commissioning of the web app are presented here as contour plots. The optimal settings found for stable 20 Ne are confirmed as the optimal settings for radioactive 18 Ne. The main takeaway, however, is that the optimal ion source parameters differ between singly-charged, doubly-charged, and molecular species. This development demonstrate and facilitate the need for element and charge state-specific parameter optimization. Additionally, the results highlight the possibility of parameter optimization to enhance the ratio of the species of interest to co-ionized contamination.
Background. Pneumococcal carriage studies provide a baseline for measuring the impact of pneumococcal conjugate vaccines (PCVs). The advent of conjugate vaccines has led to reductions in vaccine ...serotypes (VTs) in pneumococcal carriage. However, increasing non-vaccine serotypes (NVTs) remain a significant concern, necessitating continued surveillance of serotypes in the 13-valent PCV vaccine (PCV13) era. Objectives. To investigate pneumococcal carriage, serotype distribution and risk factors for pneumococcal colonisation among children presenting for routine immunisation at two clinics in Gauteng Province, South Africa (SA), 10 years after PCV introduction into the SA Expanded Programme on Immunisation (EPI-SA). Methods. Nasopharyngeal swabs were collected from 322 healthy children aged between 6 weeks and 5 years at two clinic centres in 2014 and 2016. Demographic data, risk factors for colonisation and vaccination details were recorded. The pneumococcal isolates were serotyped and tested for antimicrobial susceptibility. Results. Pneumococci were isolated from 138/316 healthy children (43.7%) presenting for routine immunisation at two clinics. The median age was 8.3 months and the age range 1.4 months - 5 years. Carriage varied across the age groups: 6 - 14 weeks 35.5%, 9 months 27.5%, 18 months 21.7%, and 5 years 15.2%. Risk factors significantly associated with pneumococcal colonisation included young age (9 18 months (odds ratio OR 3.5; 95% confidence interval (CI) 1.9 - 5.9), type of dwelling (single room (OR 8.1; 95% CI 1.3 - 52.3) or informal dwelling (OR 2.4; 95% CI 1.2 - 4.5)) and Haemophilus influenzae carriage (OR 5.6; 95% CI 0.6 - 2.5). Of the 26 serotypes detected, 19F (10/121; 8.3%) was the most frequent. The most frequent NVTs were 23B (16/121; 13.2%), 15B/C (14/121; 11.6 %) and 35B (11/121; 8.2%). Children aged 9 months carried the highest proportion of NVTs (33/101; 32.7%). Penicillin non-susceptibility was observed in 20 NVT isolates (20/36; 55.6%) and 2 VT isolates (2/36; 5.6%). Conclusions. The pneumococcal carriage prevalence described in our study varied across the age groups and was lower compared with other African studies that looked at pneumococcal carriage post PCV. The study gave insight into the common NVTs encountered at two immunisation clinics in Gauteng. Given that pneumococcal carriage precedes disease, common colonisers such as 15B/C and 35B may be sufficiently prevalent in carriage for expansion to result in significant disease replacement.
An outbreak of respiratory diphtheria occurred in two health districts in the province of KwaZulu-Natal in South Africa in 2015. A multidisciplinary outbreak response team was involved in the ...investigation and management of the outbreak. Fifteen cases of diphtheria were identified, with ages ranging from 4 to 41 years. Of the 12 cases that were under the age of 18 years, 9 (75%) were not fully immunized for diphtheria. The case fatality was 27%. Ninety-three household contacts, 981 school or work contacts and 595 healthcare worker contacts were identified and given prophylaxis against Corynebacterium diphtheriae infection. A targeted vaccination campaign for children aged 6–15 years was carried out at schools in the two districts. The outbreak highlighted the need to improve diphtheria vaccination coverage in the province and to investigate the feasibility of offering diphtheria vaccines to healthcare workers.
Trajectories of service innovations emanating from manufacturing sectors have been of particular interest to those wishing to improve resource productivity and promote sustainable development. ...Research has focused on product service systems (PSSs), which are a category of service innovations deliberately designed to offer superior environmental performance. This paper draws on research which explored whether trajectories of PSS can be induced on new UK housing developments to satisfy household demand and prevent household waste. The research was undertaken with a UK speculative house-builder and facilities management service providers from its supplier network. Qualitative data were collected via interviews and focus groups to enable rich accounts of the range of factors in these firms' selection environments which affect receptivity to PSS production to be developed. These were compared with factors affecting receptivity to PSS production identified in a study of UK manufacturers. The results show that in contrast to the manufacturing study, clear drivers for PSS delivery on new housing developments are absent in external selection environments of participating firms and uncertainty associated with the potential of PSS concepts to satisfy household demand inhibits development of requisite competence for PSS delivery within these. Thus further research is needed to explore new PSS supply arrangements involving a range of household service providers.
Abstract
At TRIUMF’s ISAC facility, 1+ Radioactive Ion Beams (RIBs) of noble gases, halogens, and molecules are created using a Forced Electron Beam Induced Arc Discharge (FEBIAD) ion source. ...Reported ionization efficiencies for FEBIADs range from 10% to 25% for
40
Ar
+
, while TRIUMF-FEBIAD ionization efficiency seems to be < 1% with a 90% emittance <15 μm. As RIB ion sources aim for a high ionization efficiency, an experimental and numerical campaign was conducted to investigate the comparably low efficiencies observed. The experimental results for
40
Ar
+
indicate that up to a 10% ionization efficiency is possible by operating the source at different parameters. The measurements agree with theoretical estimations; however, certain combinations of parameters produce an anomalously high electron current which enhances the ionization efficiency threefold. Present investigations aim to characterize and model the anomalous electron current because, if proven reliable, the argon ionization efficiency could reach 30% with no significant impact on beam emittance.
The electron target station of the TRIUMF-ARIEL Facility will employ an electron "driver" beam to irradiate Isotope Separator On-Line (ISOL) targets for the production of radioactive isotopes via ...photofission 1. 35 MeV electrons will be converted to gamma spectrum Bremsstrahlung photons via an electron to gamma (e-γ) converter located upstream of the ISOL target. The e-γ concept uses a composite metal with two layers: One high-Z material to stop and convert electrons to photons, and one low-Z material to provide structural support, thermal dissipation, and maximal transparency to the produced gamma photons as well as to provide attenuation of remaining primary electrons.. Several material combinations and bonding processes are currently being evaluated and tested using TRIUMF's e-linac. Water-cooling and thermal design are being optimized for 100 kW electron beam power operation and have thus far been experimentally validated up to 10 kW driver beam power equivalent. The latest test results and future prospects are summarized.
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