2021 Fiscal Year Research-status Report
An advanced in-trap deflector for background-free nuclear mass measurements
| Project/Area Number |
21K13951
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| Research Institution | High Energy Accelerator Research Organization |
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Principal Investigator |
Rosenbusch Marco 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 特任助教 (50790945)
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| Project Period (FY) |
2021-04-01 – 2023-03-31
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| Keywords | in-MRTOF ion selection / mass spectrometry / ion separation methods / decay-spectroscopy / ion background reduction |
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| Outline of Annual Research Achievements |
The in-MRTOF deflection system turned out to be a great success for the on-line multi-reflection time-of-flight mass spectrograph (MRTOF-MS). The new deflection system has been successfully installed, tested, and applied in on-line nuclear mass measurements at the BigRIPS separator. The construction and delivery of parts was finished during FY2020, and the installation into the vacuum took place in late FY2020 and early FY2021.
First tests have been performed using molecules ionized in a helium-filled ion catcher by an alpha-emitter source irradiating contaminations inside the helium gas. The molecules have been extracted and forwarded to the MRTOF-MS equipped with the new deflector system. Using repetitive pulses synchronized to not affect the ions of interest, only a single mass unit could be transmitted to the TOF detector while all other mass units have been removed from the flight path by interaction with the activated deflection field. Additional programming of the pulsing sequence allowed later to include multiple mass units (e.g. A=74, A=75, and A=76) simultaneously while excluding all other ions from reaching the detector.
This new system lead to overwhelmingly clean ion spectra in the experiments RIBF199 and RIBF202 (see RIKEN RIBF experiments), where the masses of 73Ni and 74Ni have been measured at the same time, and also 74Ni and 75Ni (the two latter have been measured for the first time).
This system also allowed for background-free beta-decay measurements of many isotopes to unambiguously identify the radioisotopes by their previously-known half-life.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
This project is very successful because the planning was done carefully. The new method has been tested thoroughly in simulations during the planning. The results were used to chose the design, which had to satisfy the conditions that the deflection field is effective enough as moderate voltages, and also to create a field-free region for ions that should not be affected and pass the system without experiencing any forces. For this reason also the shielding properties of the deflection area against other electrodes in the vicinity has been tested by simulations.
The required components for the project and their implementation in the working system were realistic, which includes the required machining precision of the new electrodes and the demands on the electric pulser driving the deflection field.
The trigger system and the programming of the timing sequence is based on previously existing and used components at the same setup, which allowed for a smooth software and hardware implementation building on existing expertise in the research group.
In conclusion, this project is a great success because the way of realizability and possible challenges were well estimated before the project started.
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| Strategy for Future Research Activity |
The in-MRTOF deflector will be used as an essential part of the MRTOF setup in future experiments with on-line beam at RIKEN's RIBF facility. It is a vital tool to unambiguously identify the ions of interest without the need to make multiple measurements at different numbers of reflections inside the MRTOF-MS (as necessary before: see P. Schury et al. NIM-B 335, 39 (2014)). In near future, the configuration for accepting ions of multiple chosen mass units will be further investigated and optimized. Measuring several chosen masses at the same time is a powerful tool to efficiently use the expensive time at the accelerator.
As the deflection system is operated with a larger number of electric pulses, which could in principle cause small disturbance by induction into other electrodes during the flight of the ions (up to 128 pulses at present), new studies on the mass accuracy are to be done to benchmark the high accuracy of this spectrometer.
The ability to work without unwanted ionic background opens new possibilities to accurately determine nuclear half-lives using the beta-TOF detector without implantation of other radioisotopes delivered simultaneously by the on-line beam.
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| Causes of Carryover |
Although the basic system is working, a part of the budget will be used later to be able to purchase further components for improvement of the pulse pattern (purchasing and testing different pulsing units or hardware timing sequencer). The studies and improvement of the new in-MRTOF deflector system is still in progress.
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Research Products
(6 results)
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[Journal Article] The new MRTOF spectrograph for nuclear masses following RIBF's ZeroDegree spectrometer, featuring new methodologies for ion selection and mirror optimization2022
Author(s)
M. Rosenbusch, M. Wada, S. Chen, A. Takamine, S. Iimura, D. Hou, W. Xian, S. Yan, P. Schury, Y. Ito, H. Ishiyama, S. Kimura, J. Lee, J. Liu, S. Michimasa, H. Miyatake, J. Y. Moon, S. Nishimura, S. Naimi, T. Niwase, H. Wollnik
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Journal Title
Nucl. Instrum. Meth A (under review now). See arxiv link: https://doi.org/10.48550/arXiv.2110.11507
Volume: arXiv:2110.11507
Pages: 1 - 13
Peer Reviewed / Int'l Joint Research
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