Structural trends in atomic nuclei from laser spectroscopy of tin

Tin is the chemical element with the largest number of stable isotopes. Its complete proton shell, comparable with the closed electron shells in the chemically inert noble gases, is not a mere precursor to extended stability; since the protons carry the nuclear charge, their spatial arrangement also drives the nuclear electromagnetism. We report high-precision measurements of the electromagnetic moments and isomeric differences in charge radii between the lowest 1/2(+), 3/2(+), and 11/2(-) states in Sn117-131, obtained by collinear laser spectroscopy. Supported by state-of-the-art atomic-structure calculations, the data accurately show a considerable attenuation of the quadrupole moments in the closed-shell tin isotopes relative to those of cadmium, with two protons less. Linear and quadratic mass-dependent trends are observed. While microscopic density functional theory explains the global behaviour of the measured quantities, interpretation of the local patterns demands higher-fidelity modelling. Measurements of the hyperfine structure of chemical elements isotopes provide unique insight into the atomic nucleus in a nuclear model-independent way. The authors present collinear laser spectroscopy data obtained at the CERN ISOLDE and measure hyperfine splitting along a long chain of odd-mass tin isotopes.Peer reviewe

Development of an Electrostatic Ion Beam Trap for Laser Spectroscopy of Short-lived Radionuclides

Kollineare Laserspektroskopie (CLS) ist aufgrund ihrer hohen Genauigkeit und Auflösung eine leistungsstarke Methode zur Vermessung von Eigenschaften kurzlebiger Radionukliden wie Kernspin, elektromagnetische Momente oder Ladungsradius. Die Durchführung von CLS mit beschleunigten Ionenstrahlen (> 30 keV) bietet eine hervorragende spektrale Auflösung, die sich der natürlichen Linienbreite des spektroskopischen Übergangs annähert. Der optische Nachweis von Fluoreszenz beschränkt die erfolgreiche Anwendung von CLS jedoch auf Radionuklide mit Produktionsraten von mehr als 100 bis 10.000 Ionen pro Sekunde, abhängig vom speziellen Fall und dem benutzten spektroskopischen Übergang. Um die CLS Reichweite auf die “exotischsten” Nuklide mit sehr geringen Produktionsausbeuten auszudehnen, sind empfindlichere Methoden erforderlich. Aus diesem Grund wird derzeit das neuartige Multi-Ionen-Reflexionsgerät für CLS (MIRACLS) am europäischen Kernforschungszentrum CERN entwickelt. Dieser Aufbau zielt darauf ab, die hohe Auflösung herkömmlicher fluoreszenzbasierter CLS mit einer hohen experimentellen Empfindlichkeit zu kombinieren, die je nach Masse und Lebensdauer des untersuchten Nuklids um den Faktor 30 bis 700 erhöht wird. Durch wiederholtes Reflektieren des Ionenstrahls zwischen den elektrostatischen Spiegeln einer elektrostatischen Ionenstrahlfalle, die oft auch als MR-ToF-Vorrichtung (Multi-Reflection Time of Flight) bezeichnet wird, prüft der Laserstrahl das eingefangene Ionenbündel während jedem Umlauf im MR-ToF Gerät. Daher wird die Beobachtungszeit verlängert und die experimentelle Empfindlichkeit im Vergleich zu herkömmlichem CLS mit einer einzelnen Passage erhöht. Im Rahmen dieser Arbeit wurde ein MIRACLS Pilotexperiment um ein MR-ToF-System herum aufgebaut, welches mit Ionen mit einer Strahlenregie von ≈1,5 keV operierte und das für CLS-Zwecke erweitert wurde. Ziel dieses Aufbaus was es, das Potenzial des MIRACLS-Konzepts zu demonstrieren, Simulationen zu bewerten, die zum Entwurf eines zukünftigen 30-keV Geräts verwendet werden, und die MIRACLS Technik generell weiterzuentwickeln. Zu diesem Zweck wurden CLS-Messungen mit Ionen stabiler Magnesium- und Calciumisotope durchgeführt. Diese Daten dienten dazu, die Leistung der neuen Methode zu charakterisieren, insbesondere im Hinblick auf die Erhöhung der Empfindlichkeit und der Messgenauigkeit.Due to its high accuracy and resolution, collinear laser spectroscopy (CLS) is a powerful tool to measure nuclear ground state properties such as nuclear spins, electromagnetic moments and mean-square charge radii of short-lived radionuclides. Performing CLS with fast beams (>30 keV) provides an excellent spectral resolution approaching the natural linewidth. However, its fluorescence-light detection limits its successful application to nuclides with yields of more than several 100 to 10,000 ions/s, depending on the specific case and spectroscopic transition. To extend its reach to the most exotic nuclides with very low production yields far away from stability, more sensitive methods are needed. For this reason, the novel Multi Ion Reflection Apparatus for CLS (MIRACLS) is currently under development at ISOLDE/CERN. This setup aims to combine the high resolution of conventional fluorescence based CLS with a high experimental sensitivity, enhanced by a factor of 30 to 700 depending on the mass and lifetime of the studied nuclide. By repetitively reflecting the ion beam between the electrostatic mirrors of an electrostatic ion beam trap, often also called Multi-Reflection Time of Flight (MR-ToF) device, the laser beam probes the ion bunch during each revolution. Therefore, the observation time is extended and the experimental sensitivity is enhanced compared to conventional single-passage CLS. As part of this thesis, a MIRACLS proof-of-principle apparatus has been constructed around an MR-ToF system, operating at ~1.5 keV beam energy, which has been upgraded for the purpose of CLS. The goal of this setup is to demonstrate the potential of the MIRACLS concept, to benchmark simulations that are employed to design a future device operating at 30 keV, and to further develop the technique. For this purpose, CLS measurements with ions of stable magnesium and calcium isotopes are performed. This data serves to characterise the performance of the new method, especially in terms of gain in sensitivity and measurement accuracy

Detailed Efficiency Simulations of the GEROS spectrometer using MCNP5

A poster presented at HNPS2017 (9-10.06.2017)<br

A new γ-spectrometry station at the University of Athens

<p>A poster presented at HNPS2014, May 2014</p> <p>AUTh, Thessaloniki, Greece</p

Radioactivity Studies in Soils from Northwestern Greece

A poster presented at HNPS2023, 29-30.09.2023 at NTUA, Athens</p

A study of natural radioactivity in urban parks

A poster presented at HNPS2023, 29-20.09.2023 at NTUA</p

A comparative study of γ-ray spectrometers in various applications

A poster presented at HNPS2023, 29-30.09.2023 at NTUA, Athens, Greece</p

Fluorescence detection as a new diagnostics tool for electrostatic ion beam traps

In the development towards the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS), an optical detection region for the observation of fluorescent light is added to an electrostatic ion beam trap (EIBT). In addition to its use for highly sensitive collinear laser spectroscopy, this fluorescence detection is introduced as a diagnostics tool for the study of the ion dynamics inside an EIBT. First measurements of collision-induced fluorescence in an EIBT demonstrate the technique’s diagnostics power by tracking the evolution of an ion bunch’s temporal width over its storage time inside the ion trap. Thereby, the time-focus point of the ion bunch can be determined and the influence of space-charge effects in the EIBT can be investigated. Good qualitative agreement is obtained between the measured trend of temporal widths and the simulations of the ions’ trajectories in the trap. Particularly, the observation of self-bunching on the ion-bunch structure for many simultaneously stored ions is reproduced

First steps in the development of the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy

Collinear laser spectroscopy (CLS) has been combined with the multi-reflection time-of-flight (MR-ToF) technique. To this end, a photodetection system has been implemented at the drift region of a MR-ToF apparatus and a laser beam has been sent along the path of the ions that are stored between the two ion-optical mirrors. The main goal of the present proof-of-principle (PoP) experiments, is the confirmation of the expected increase in sensitivity compared to conventional fluorescence-based CLS due to the repeated probing of the trapped ion bunches. The novel method will be used for the precise measurement of nuclear ground- and isomeric-state properties of exotic nuclei with low production yields at radioactive ion-beam facilities. A significant sensitivity improvement of CLS is expected, depending on the half-life and mass of the nuclide of interest. The status of the PoP setup and future improvements are discussed.Collinear laser spectroscopy (CLS) has been combined with the multi-reflection time-of-flight (MR-ToF) technique. To this end, a photodetection system has been implemented at the drift region of a MR-ToF apparatus and a laser beam has been sent along the path of the ions that are stored between the two ion-optical mirrors. The main goal of the present proof-of-principle (PoP) experiments, is the confirmation of the expected increase in sensitivity compared to conventional fluorescence-based CLS due to the repeated probing of the trapped ion bunches. The novel method will be used for the precise measurement of nuclear ground- and isomeric-state properties of exotic nuclei with low production yields at radioactive ion-beam facilities. A significant sensitivity improvement of CLS is expected, depending on the half-life and mass of the nuclide of interest. The status of the PoP setup and future improvements are discussed