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 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
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.
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.
Abstract
Nuclear charge radii globally scale with atomic mass number
A
as
A
1∕3
, and isotopes with an odd number of neutrons are usually slightly smaller in size than their even-neutron neighbours. ...This odd–even staggering, ubiquitous throughout the nuclear landscape
1
, varies with the number of protons and neutrons, and poses a substantial challenge for nuclear theory
2–4
. Here, we report measurements of the charge radii of short-lived copper isotopes up to the very exotic
78
Cu (with proton number
Z
= 29 and neutron number
N
= 49), produced at only 20 ions s
–1
, using the collinear resonance ionization spectroscopy method at the Isotope Mass Separator On-Line Device facility (ISOLDE) at CERN. We observe an unexpected reduction in the odd–even staggering for isotopes approaching the
N
= 50 shell gap. To describe the data, we applied models based on nuclear density functional theory
5,6
and
A
-body valence-space in-medium similarity renormalization group theory
7,8
. Through these comparisons, we demonstrate a relation between the global behaviour of charge radii and the saturation density of nuclear matter, and show that the local charge radii variations, which reflect the many-body polarization effects, naturally emerge from
A
-body calculations fitted to properties of
A
≤ 4 nuclei.
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FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A series of irradiation tests have been performed at TRIUMF to investigate different material pairings to act as high-power electron-to-gamma converter for the ARIEL Electron Target East (AETE). The ...bulk of the converter body will be made out of an aluminum alloy with a sub-millimeter high-Z metal layer bonded to the surface facing the incoming electron beam. This contribution presents the approach chosen to select the optimal material for the high-Z layer, describes the tests performed and shows result which led to the successful selection of a specific tantalum-aluminum pairing as the future ARIEL converter material.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This article summarizes the current specifications and the latest features of the CERN-ISOLDE resonance ionization laser ion source (RILIS). This includes a description of the optical layout and the ...newly designed reference system. The ionization schemes for the laser ionized beams at ISOLDE are tabulated, including six new elements. All RILIS schemes are also made publicly available in the RILIS elements on-line database. Finally, we announce a paradigm shift in RILIS operation – the combination of a machine protection and a monitoring and control system has enabled on-call operation of the laser ion source for selected beams in 2014 and has become the standard mode of operation in 2015.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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
The mean-square charge radii of 207,208Hg (Z = 80, N = 127, 128) have been studied for the first time and those of 202,203,206Hg (N = 122, 123, 126) remeasured by the application of in-source ...resonance-ionization laser spectroscopy at ISOLDE (CERN). The characteristic kink in the charge radii at the N = 126 neutron shell closure has been revealed, providing the first information on its behavior below the Z = 82 proton shell closure. A theoretical analysis has been performed within relativistic Hartree-Bogoliubov and nonrelativistic Hartree-Fock-Bogoliubov approaches, considering both the new mercury results and existing lead data. Contrary to previous interpretations, it is demonstrated that both the kink at N = 126 and the odd-even staggering (OES) in its vicinity can be described predominately at the mean-field level and that pairing does not need to play a crucial role in their origin. A new OES mechanism is suggested, related to the staggering in the occupation of the different neutron orbitals in odd- and even-A nuclei, facilitated by particle-vibration coupling for odd-A nuclei.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
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