Project

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Measurement of the charge radius of radium

Applicant Knecht Andreas
Number 165569
Funding scheme Project funding
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Particle Physics
Start/End 01.10.2016 - 30.11.2020
Approved amount 310'728.00
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All Disciplines (2)

Discipline
Particle Physics
Nuclear Physics

Keywords (4)

Slow muon beam; Muon; Charge radius; Radium

Lay Summary (German)

Lead
Der Ladungsradius eines Atomkernes ist eines seiner definierenden Merkmale und von grosser Wichtigkeit zur Bestimmung der Wechselwirkung des Kernes mit den ihn umgebenden Elektronenschalen. Zur Zeit ist ein Experiment im Aufbau, das paritätsverletzende (Verletzung der Spiegelsymmetrie) Übergänge im radioaktiven Element Radium messen will und dafür den absoluten Ladungsradius von Radium benötigt. Mit Hilfe der Gammaspektroskopie charakteristischer Übergangslinien von sich formenden myonischen Atomen, die wir an einem speziellen Myonstrahl am Paul Scherrer Institut (PSI) erzeugen, können wir den Ladungsradius von Radium und anderer Isotope bestimmen.
Lay summary

Die Ladungsradien vieler Elemente wurden über all die Jahre schon gemessen. Wo es jedoch noch Lücken gibt ist bei radioaktiven Elementen, von denen man meistens nur die Änderung der Ladungsradien zwischen den unterschiedlichen Isotopen kennt. Zur Zeit ist ein Experiment im Aufbau, das paritätsverletzende (Verletzung der Spiegelsymmetrie) Übergänge im radioaktiven Element Radium messen will und dafür den absoluten Ladungsradius von Radium benötigt. 

 

Eine Methode zur Messung von absoluten Ladungsradien ist die Gammaspektroskopie von Übergängen in myonischen Atomen. Dazu wird ein negativer Myonenstrahl im zu untersuchenden Material gestoppt und die charakteristischen Emissionslinien, die beim Einfang des Myons durch den Kern ausgesandt werden, untersucht und der Ladungsradius des Kernes extrahiert. 

 

Da die radioaktiven Elemente nur in kleinen Mengen von ein paar Mikrogramm verfügbar sind, kann man die Messung nicht an einem normalen Myonenstrahl, die am PSI vorhanden sind, durchführen, sondern braucht dazu einen speziell entwickelten Strahl, der die Myonen auf sehr langsame Energien abbremst. Dieser Strahl wurde ursprünglich für das Lamb-Shift-Experiment entwickelt und wird nun von uns für die Messung des Ladungsradius radioaktiver Atome verwendet.

Direct link to Lay Summary Last update: 28.04.2016

Responsible applicant and co-applicants

Employees

Publications

Publication
Study of nuclear properties with muonic atoms
Knecht A., Skawran A., Vogiatzi S. M. (2020), Study of nuclear properties with muonic atoms, in The European Physical Journal Plus, 135(10), 777-777.
Measurement of the quadrupole moment of Re185 and Re187 from the hyperfine structure of muonic X rays
Antognini A., Berger N., Cocolios T. E., Dressler R., Eichler R., Eggenberger A., Indelicato P., Jungmann K., Keitel C. H., Kirch K., Knecht A., Michel N., Nuber J., Oreshkina N. S., Ouf A., Papa A., Pohl R., Pospelov M., Rapisarda E., Ritjoho N., Roccia S., Severijns N., Skawran A., Vogiatzi S. M., et al. (2020), Measurement of the quadrupole moment of Re185 and Re187 from the hyperfine structure of muonic X rays, in Physical Review C, 101(5), 054313-054313.
Towards nuclear structure with radioactive muonic atoms
SkawranA, AdamczakA, AntogniniA, BergerN, CocoliosT E, DresslerR, DüllmannC, EichlerR, IndelicatoP, JungmannK, KirchK, KnechtA, KrauthJ J, NuberJ, PapaA, PohlR, PospelovM, RapisardaE, RenischD, ReiterP, RitjohoN, RocciaS, SeverijnsN, VogiatziS, WautersF, WillmanL (2019), Towards nuclear structure with radioactive muonic atoms, in IL NUOVO CIMENTO, 42 C, 125.
Nuclear structure with radioactive muonic atoms
Adamczak A., Antognini A., Berger N., Cocolios T.E., Dressler R., Eggenberger A., Eichler R., Indelicato P., Jungmann K., Kirch K., Knecht A., Papa A., Pohl R., Pospelov M., Rapisarda E., Reiter P., Ritjoho N., Roccia S., Severijns N., Skawran A., Wauters F., Willmann L. (2018), Nuclear structure with radioactive muonic atoms, in EPJ Web of Conferences, 193, 04014-04014.

Collaboration

Group / person Country
Types of collaboration
S. Roccia, Institut Laue Langevin France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
P. Reiter, Institut für Kernphysik, Universität zu Köln Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
T. Cocolios, Nuclear and Radiation Physics, KU Leuven Belgium (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
A. Amato, Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Y. Shitov, Joint Institute for Nuclear Research, Dubna Russia (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
P. Indelicato, Metrology of Simple Systems and Fundamental Tests, Laboratoire Kastler Brossel France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
K. Jungmann, Faculty of Science and Engineering, Universität Groningen Netherlands (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
R. Eichler, Labor für Radiochemie, Paul Scherrer Institut Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
C. H. Keitel, Max Planck Institute for Nuclear Physics, Heidelberg Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Ch.E. Düllmann, Kernchemie, Johannes Gutenberg Universität Mainz Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
A. Adamczak, Institute of Nuclear Physics, Polish Academy of Sciences Poland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
N. Severijns, Nuclear and Radiation Physics, KU Leuven Belgium (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
M. Pospelov, University of Victoria Canada (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
K. Kirch, Precision Physics at Low Energy, ETHZ Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
N. Berger, Research Group Berger, Johannes Gutenberg Universität Mainz Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
R. Pohl, Research Group Pohl, Johannes Gutenberg Universität Mainz Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Rewriting Nuclear Physics Textbooks: one more step forward Talk given at a conference Study of nuclear properties 
 with muonic atoms 22.07.2019 Pisa, Italy Knecht Andreas;
Seminar der Abteilung Radiochemie an der Johannes Gutenberg Universität Mainz Individual talk Measuring the charge radius of 
 radioactive nuclei with muonic atoms 29.10.2018 Mainz, Germany Knecht Andreas;
2018 European Nuclear Physics Conference Talk given at a conference Nuclear Structure with radioactive muonic atoms - The nuclear charge radius of radioactive isotopes by muonic X-rays measurements 02.09.2018 Bologna, Italy Skawran Alexander Albert;
SPES one-day Workshop "Probing fundamental symmetries and interactions by low energy excitations with SPES RIBs" Talk given at a conference Atomic parity violation with radioactive ions &
 the muX experiment 01.02.2018 Pisa, Italy Knecht Andreas;


Self-organised

Title Date Place
Workshop on Muonic Atom Spectroscopy 21.10.2016 Villigen PSI, Switzerland

Abstract

This research plan proposes to measure for the first time the absolute charge radius of radium and additionally also rhenium, curium and polonium. Next to its mass the charge radius of a nucleus is one of its main defining parameters. So far no absolute charge radius measurements exist for the nuclei mentioned above thus providing ample motivation for this proposal. In the case of radium the motivation goes even beyond. An experiment measuring parity violating transitions in a single, trapped radium ion is currently underway. The extraction of the underlying physics in the form of the weak mixing angle relies on the precise calculation of all necessary corrections and needs a measurement of the charge radius with an accuracy of 0.2%.In order to measure absolute charge radii muonic atom spectroscopy offers an excellent method that has been widely employed over a wide range of isotopes. In this method the characteristic X-rays emitted during the cascade of the muon into the ground state are analyzed by means of germanium detectors. From the measured transition energies the charge radii can be extracted with high accuracy. In the case of 208-Pb an impressive relative accuracy of 0.02% in the measurement of its charge radius was achieved showing the potential of this method.As we cannot use a large mass of the radioactive isotopes mentioned above we will use a special slow negative muon beam developed for the Lamb shift experiment to stop in about 1 µg/cm^2 of target mass. A high-purity germanium detector located close to the target will record the muonic X-rays and allow us to extract the relevant charge radii.
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