CERN Accelerating science

Thesis
Report number	CERN-THESIS-2023-406
Title	Advancements in MR-ToF Technology and Implementation of Doppler and Sympathetic Cooling for the Study of Radioactive Ions
Author(s)	Maier, Franziska Maria (Greifswald U.)
Publication	2023 - 127.
Thesis note	PhD : Greifswald U. : 2023
Thesis supervisor(s)	Malbrunot- Ettenauer, Stephan ; Schweikhard, Lutz
Note	Presented 21 Jul 2023
Subject category	Nuclear Physics - Experiment
Accelerator/Facility, Experiment	CERN ISOLDE ; ISOL
Abstract	Ion traps such as Paul traps and MR-ToF (multi-reflection time-of-flight) devices are indispensable tools at radioactive ion beam facilities for the preparation of high-quality radioactive ion beams for subsequent experiments or for precise measurements of the properties of radioactive ions, such as nuclear binding energies or nuclear charge radii. Within the work of this thesis, Doppler- and sympathetic cooling is implemented in a linear Paul-trap cooler-buncher enabling a reduction of the longitudinal emittance of radioactive ion beams resulting in a significant improvement of the ion beam quality. Moreover, a next-generation MR-ToF device is conceptualized in order to achieve isobaric pure beams with a higher ion intensity than state-of-the-art MR-ToF devices can provide. Once fully constructed and commissioned, it will operate at an unprecedented ion beam energy of 30 keV. Both of these advances are expected to become important for a wide range of experimental programs pursued at low-energy branches of RIB facilities ranging from fundamental symmetry studies, nuclear structure, rare isotope studies with antimatter, searches of physics beyond the standard model to material science and the production of medical isotopes. The next-generation MR-ToF mass separator is based on MIRACLS’ 30-keV MR-ToF device for highly sensitive and high-resolution collinear laser spectroscopy. By storing the ions in the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS), the same ion bunch is probed by a spectroscopic laser for thousands of times compared to a single passage in traditional collinear laser spectroscopy (CLS). Dedicated simulation studies show that the accuracy and resolution will be close to traditional single-passage CLS while the sensitivity is significantly enhanced. Hence, measurements of nuclear properties via fluorescence-based CLS of very rare radionuclides as well as highly sensitive and high-precision measurements of electron affinities via laser-photodetachment-threshold spectroscopy of negatively-charged (radioactive) ions will become possible. First measurement campaigns employing MIRACLS’ 1.5-keV MR-ToF device confirm the outstanding boost in signal sensitivity and provide confidence in the application of the MIRACLS technique for the measurement of scarcely produced radioactive ions that have been so far beyond the reach of conventional techniques. Furthermore, the electron affinity of 35Cl was measured, which is in perfect agreement with the literature value. These measurements will serve as important benchmarks for modern atomic and nuclear theory, especially in its description of nuclear charge radii. In summary, the implementation of Doppler and sympathetic cooling at RIB facilities, the conceptualization of a 30-keV MR-ToF apparatus for highly selective and high-flux mass separation as well as for highly sensitive and high-resolution fluorescence-based laser spectroscopy and the expansion of the MIRACLS technique for the study of negatively-charged ions will enable unprecedented new measurement opportunities at RIB facilities.

Email contact: franziska.maria.maier@cern.ch