Project
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Towards implementing new isotopes for environmental research: The half-life of 32Si
Applicant |
Schumann Dorothea
|
Number |
177229 |
Funding scheme |
Sinergia
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Research institution |
Paul Scherrer Institut
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Institution of higher education |
Paul Scherrer Institute - PSI |
Main discipline |
Interdisciplinary |
Start/End |
01.09.2018 - 31.08.2023 |
Approved amount |
1'933'529.00 |
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All Disciplines (9)
Astronomy, Astrophysics and Space Sciences |
Climatology. Atmospherical Chemistry, Aeronomy |
Keywords (6)
nuclear dating; half life determination; nuclear astrophysics; Liquid Scintillation Counting; Accelerator Mass Spectrometry; environmental research
Lay Summary (German)
Lead
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Die klimatischen Veränderungen auf der Erde beeinflussen Mensch und Gesellschaft. Um die richtigen Entscheidungen treffen zu können, benötigen sowohl Wissenschaftler als auch Politiker fundierte Kenntnisse über die Natur der involvierten Prozesse. Ein wichtiger Parameter in diesen Forschungen ist die korrekte Altersbestimmung der entsprechenden Untersuchungsobjekte, wie z.B. Sediment-Proben oder Eisbohrkerne. Radioaktive Isotope spielen dabei eine zentrale Rolle. Neben der allseits gut bekannten Radiokarbon-Methode werden auch andere natürlich vorkommende Radionuklide wie 210Pb oder 36Cl zur Datierung benutzt. Je nach Halbwertszeit decken sie einen bestimmten Zeitbereich ab. Zwischen 210Pb mit 22 Jahren Halbwertszeit und 14C mit 5730 Jahren gibt es eine Lücke, für die bisher kein geeignetes Radionuklid etabliert werden konnte.
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Lay summary
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Inhalt und Ziel Für den interessanten Zeitraum zwischen 100-1000 Jahren wäre das Radionuklid 32Si mit einer geschätzten Halbwertszeit von ~ 150 Jahren der ideale Kandidat. Zwar ist die Halbwertzeit verschiedene Male mit unterschiedlichen Methoden bestimmt worden, jedoch reichen die Werte von 100 bis 300 Jahren, was derzeit eine Benutzung des Nuklids zur Datierung verunmöglicht. Eine Verbesserung der Situation kann nur erreicht werden, wenn mehrere unabhängige Messmethoden einen einheitlichen Wert bestätigen könnten. Dabei erweist sich die sehr limitierte Verfügbarkeit des Probenmaterials als zusätzliche Erschwernis. Wir haben in am PSI bestrahlten Probenmaterial die erforderliche Menge an 32Si zur Verfügung. Die Aufgaben bestehen darin, 1) das Nuklid in erforderlicher Menge und Reinheit chemisch abzutrennen, 2) die entsprechenden Messmethoden (Massenspektrometrie und Aktivitätsmessungen) zu entwickeln und 3) einen neuen Wert für die 32Si-Halbwertszeit zu bestimmen, der durch mehrere unabhängige Einzelmessungen abgesichert ist. Darüber hinaus soll ein Set von Standards hergestellt werden, das die routinemässige Bestimmung von relevanten Umweltproben ermöglicht. Wissenschaftlicher und gesellschaftlicher Kontext Wir hoffen, mit einer gesicherten Halbwertszeit für 32Si eins der wichtigen natürlichen Radionuklide für die Umweltforschung nutzbar zu machen. Die klimarelevanten Prozesse in den letzten 1000 Jahren könnten damit besser verstanden werden. Die Weiterentwicklung der Messmethoden eröffnet auch neue Horizonte für andere Radionuklide, die für derartige Untersuchungen interessant sein könnten.
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Responsible applicant and co-applicants
Employees
Project partner
Scientific events
Active participation
Title |
Type of contribution |
Title of article or contribution |
Date |
Place |
Persons involved |
Awards
1st year PhD prize NES
|
2019
|
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Project funding |
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Project funding |
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|
Exotic Radionuclides from Accelerator Waste for Science and Technology - ERAWAST III: Half-life determination of pure electron capture nuclides (137La, 157Tb) |
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Project funding |
Abstract
The predicted climate changes on Earth will have a high impact on the environment and the human society. The climate patterns observed during the past centuries leads to a better understanding of the driving forces for such changes. They are the foundation for extrapolating and modelling future climate changes. More studies using new, innovative techniques are necessary to broaden the knowledge on the involved processes and accomplish a reliable scientific basis for decision makers. Precise time information is crucial when climate archives are investigated. The radioactive isotopes 32Si with a half-life of approximately (153±19) years (calculated average value taken from [ND11]) and 39Ar (369±3) years [ND05]) are cosmogenic nuclides that are produced in the upper atmosphere by bombardment of cosmic rays on argon. They are the only two available radionuclides with the potential to fill the dating gap between the relatively short-lived 210Pb (T1/2 ˜ 22 y) on the one side and the longer-lived 14C (T1/2 ˜ 5730 y) on the other side, thus allowing to understand environmental processes such as glacier dynamics, ocean and atmospheric circulation, sedimentation in lakes and oceans or groundwater flow in the recent past (100-1000 years). However, for precise dating the accurate knowledge of the radionuclide`s half-life is mandatory. So far, the inconsistent data base on the nuclear properties of 32Si and doubtful nuclear data for 39Ar as well as their extreme rareness made their application difficult if not impossible with current technology. Therefore, the applicability of these isotopes for environmental research studies is still very limited. To overcome this important obstacle, the following qualifications have to be fulfilled: 1) the half-lives need to be known with high accuracy and low uncertainty, if absolute ages or comparison to other dating methods are required.; 2) reliable and reproducible routine measurement techniques including certified reference materials are needed; 3) sufficient sample material for both fundamental research comprising half-life determination as well as for provision of calibration standards for later routine measurements (dating) are necessary.As a first step, we focus on 32Si and propose to solve these challenges in the following way:a)Around 200 MBq of 32Si were produced at the Paul Scherrer Institute (PSI) by bombarding metallic vanadium with 590 MeV protons over 2 years (End of Beam 2012). A radiochemical separation system will be developed and applied for isolating and purifying 32Si from the matrix material as well as from other rare exotic isotopes (e.g., 44Ti, 41Ca, 39/42Ar, 26Al, 40K), which are urgently needed for applications in nuclear medicine, nuclear astrophysics, environmental research, basic nuclear physics among others.b)Measurement techniques (Liquid Scintillation Counting (LSC), Cerenkov measurement (CM), Plastic Scintillation (PS) counting, Ionization Chamber (IC) measurements, Accelerator Mass Spectrometry (AMS) and Inductively Coupled Plasma - Mass Spectrometry (ICP-MS)) will be utilized and refined. The techniques developed in this course will subsequently meet the special requirements for the half-life determination of 32Si as well as future routine measurements of 32Si. Using a fraction of the isolated 32Si sample, complementary half-life measurements via different techniques will be performed.c)Standard materials for all applicable measurement techniques shall be produced and made available for routine measurements world-wide.The re-determination of the half-life and the availability of 32Si standard material will be a first, ground-breaking step towards fostering its routine application in environmental and astrophysical applications. More efforts and projects have to follow to establish the method for investigating processes in the recent past on Earth and in stars aside the commonly accepted doctrines.
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