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.
Simulation-based optimization for the TRIUMF FEBIAD ion source Maldonado Millan, F.; Babcock, C.; Day Goodacre, T. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
September 2023, 2023-09-00, Volume:
542
Journal Article
Peer reviewed
The TRIUMF-FEBIAD ion source is typically used to generate radioactive ion beams of molecules, halogens, and noble gases. The experimental campaign undertaken in the past couple of years has shown ...room for operational improvement, for example, by increasing the thermionic emission from the hot cathode. However, this work has also identify reliability issues in the thermo-mechanical aspect of the source. To mitigate failures observed due to unwanted excessive heating, a simulation campaign has been performed to increase the reliability and performance of the FEBIAD ion source. This paper presents the results derived from a simulation-based optimization campaign that can increase the overall ionization efficiency and robustness of the TRIUMF-FEBIAD ion source.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
Multiphysics simulation of a FEBIAD ion source Maldonado Millan, F.; Day Goodacre, T.; Gottberg, A.
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
01/2020, Volume:
463
Journal Article
Peer reviewed
The FEBIAD ion source is routinely operated at TRIUMF-ISAC to produce radioactive ion beams, however there is scope to improve the ionization efficiency and beam quality. To achieve this improvement, ...simulations with the Comsol multiphysics software suite and experimental studies are being performed. Preliminary simulations indicate that the ionization rate inside the anode exhibits a spatial variation determined by the local electron fluence. The FEBIAD electromagnet coil is included in a simulation for the first time and a first validation of the methodology is the reproduction of experimental observables, e.g. the ion current generated as a function of the electromagnet coil current. The multiphysics approach of the simulations, and the experimental validation, can lead to a better understanding with possibilities to optimize the FEBIAD ion source and improve its versatility. With ARIEL, TRIUMF’s new ISOL facility, two target stations with improved target-ion source flexibility will open additional avenues to implement modified designs of a FEBIAD with increased capabilities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Factors affecting immunogenicity of the first 2 doses of oral poliovirus vaccine (OPV) among unimmunized Mayan infants were prospectively evaluated. The relative impact of multiple variables, ...including mass or routine vaccination, concurrent enteric bacterial (salmonella, shigella, and campylobacter) and viral (adenovirus 40/41, astrovirus, nonpolio enteroviruses, and rotavirus) infections, interference among Sabin vaccine viruses, and preexisting poliovirus antibodies were studied. Sera were available from 181 infants after 2 OPV doses. Seroresponses were 86% to Sabin type 1, 97% to Sabin type 2, and 61% to Sabin type 3 vaccines. Mass versus routine vaccination and preexisting poliovirus antibodies did not affect immunogenicity. By multiple logistic regression analysis, fecal shedding of homologous Sabin strains was associated with increased seroresponses to all Sabin types, especially to Sabin type 3. Decreased OPV immunogenicity was primarily attributable to interference of Sabin type 3 by Sabin type 2. OPV formulations with higher doses of Sabin type 3 could improve immunogenicity among infants in developing countries.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Symptomatic and asymptomatic astrovirus infection was prospectively determined in a 3-year birth cohort of Mayan infants. Stool samples from 271 infants and 268 older siblings were tested for ...astrovirus, adenovirus 40/41, rotavirus and Salmonella, Shigella and Campylobacter species. Concurrent diarrhea, vomiting, fever, or anorexia were noted. Astrovirus was detected in 164 infants (61%) and 20 siblings (7%). Rotavirus (4%) and adenovirus 40/41 (13%) were isolated less frequently. Of all diarrheal episodes reported at a visit, 26% (78/305) were associated with astrovirus; 17% (78/452) of astrovirus infections were associated with diarrhea and 9% with other symptoms. Only diarrhea was associated with astrovirus infection (odds ratio, 1.4; 95% confidence interval CI, 1.07–1.92; P = .01). Of infants with astrovirus, 70% shed at multiple visits over a period of 2–17 weeks (median, 5). The point prevalence of astrovirus infection was significantly higher among infants than siblings (relative risk, 6.18; 95% CI, 3.93–9.72; P < .0001, χ2). Astrovirus was identified throughout the year, peaked in March and May, and decreased in September. In this population, astrovirus was the most common enteric pathogen isolated; symptomatic infection was prevalent among infants.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
In a 24‐month, multicenter, open‐label, randomized trial, 715 de novo kidney transplant recipients were randomized at 10–14 weeks to convert to everolimus (n = 359) or remain on standard calcineurin ...inhibitor (CNI) therapy (n = 356; 231 tacrolimus; 125 cyclosporine), all with mycophenolic acid and steroids. The primary endpoint, change in estimated glomerular filtration rate (eGFR) from randomization to month 12, was similar for everolimus versus CNI: mean (standard error) 0.3(1.5) mL/min/1.732 versus −1.5(1.5) mL/min/1.732 (p = 0.116). Biopsy‐proven acute rejection (BPAR) at month 12 was more frequent under everolimus versus CNI overall (9.7% vs. 4.8%, p = 0.014) and versus tacrolimus‐treated patients (2.6%, p < 0.001) but similar to cyclosporine‐treated patients (8.8%, p = 0.755). Reporting on de novo donor‐specific antibodies (DSA) was limited but suggested more frequent anti‐HLA Class I DSA under everolimus. Change in left ventricular mass index was similar. Discontinuation due to adverse events was more frequent with everolimus (23.6%) versus CNI (8.4%). In conclusion, conversion to everolimus at 10–14 weeks posttransplant was associated with renal function similar to that with standard therapy overall. Rates of BPAR were low in all groups, but lower with tacrolimus than everolimus.
In a multicenter, open‐label, randomized trial of de novo kidney transplant recipients, conversion to everolimus at 10–14 weeks posttransplant is associated with similar renal function as in patients who continue to standard tacrolimus or cyclosporine therapy, with low rates of biopsy‐proven acute rejection in all groups, but lower rates with tacrolimus than everolimus.
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BFBNIB, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Most inherited TP53 mutations have been identified in individuals with a family cancer predisposition syndrome, in which the activity of p53 mutants is severely reduced. However, germline p53 mutants ...in children with 'sporadic' adrenocortical or choroid plexus tumors exhibit a wide range of functional activity. Here, we demonstrate the occurrence of a complex germline TP53 mutation in two unrelated families with different cancer phenotypes, neither fulfilling the classic criteria for Li-Fraumeni syndrome. The TP53 mutation consists of a duplication of 7 bp in exon 4, resulting in a frame shift and premature stop signal. Haplotype analysis indicated that the mutation arose independently in the two families. Analysis of the DNA secondary structure predicts the TP53 mutation occurred within a hairpin loop. Additional germline complex mutations occurring within the same region of exon 4 have been identified in the IARC database. Our findings suggest that certain TP53 regions are prone to intrinsic genetic alterations, possibly through defects in DNA replication or repair. Further, carriers of the same TP53 mutation can have diverse cancer profiles, illustrating the complexity of genetic counseling and risk prediction.
Background
: Hydroa vacciniforme (HV) is a disease of unknown origin characterized by erythema, vesicles, necrosis, and varicelliform scars in light-exposed skin. Systemic involvement is absent. A ...few patients have been reported with “severe HV” with systemic involvement, development of non-Hodgkin's lymphoma, and a poor prognosis.
Objective
: Our purpose was to characterize and differentiate our patients' disease from HV.
Methods
: We performed a retrospective clinicopathologic study of 14 children previously diagnosed as having “severe HV”.
Results
: The extension and severity of the cutaneous lesions, fever, wasting, failure to thrive, hepatosplenomegaly, vasculitis, panniculitis, and potential development of lymphoma are features that clearly differentiate edematous scarring vasculitic panniculitis from HV.
Conclusion
: Edematous scarring vasculitic panniculitis is a novel multisystemic disease with malignant potential that is not related to classic HV.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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