Improving the Spectral Coverage and Resolution of the ISOLDE RILIS

This thesis concerns applications and developments of the Resonance Ionization Laser Ion Source (RILIS) at CERN-ISOLDE for ion beam production and laser spectroscopy. Laser developments, including the first operation of a grating-tuned Ti:sapphire combined with a thick etalon for linewidth reduction, the construction and characterization of a seeded Ti:sapphire ring cavity laser and the first demonstration of a Raman laser in the blue spectral range are presented. In-source laser spectroscopy on Dy isotopes has been performed, providing a valuable insight into the nuclear charge radii systematics near proton number Z=64. This work also illustrates the resolution limit imposed by Doppler-broadening of the atomic spectral lines inside the ion source. Addressing this limitation, the Doppler-free 2-photon ionization technique has been developed, leading to its first successful "in-source" application. The future of this approach to significantly increase the spectral resolution of RILIS is discussed

Tunable diamond raman lasers for resonance photo-ionization and ion beam production

Lasers with wide tunability and tailored linewidth are key assets for spectroscopy research and applications. We show that diamond, when configured as a Raman laser, provides agile access to a broad range of wavelengths while being capable of efficient and selective photo-excitation of atomic species and suitable spectroscopic applications thanks to its narrow linewidth. We demonstrate the use of a compact diamond Raman laser capable of efficient ion beam production by resonance ionization of Sm isotopes in a hot metal cavity. The ionization efficiency was compared with a conventional Ti:sapphire laser operating at the same wavelength. Our results show that the overall ion current produced by the diamond Raman laser was comparable -or even superior in some cases-to that of the commonly used Ti:sapphire lasers. This demonstrates the photo-ionization capability of Raman lasers in the Doppler broadening-dominated regime, even with the considerable differences in their spectral properties. In order to theoretically corroborate the obtained data and with an eye on studying the most convenient spectral properties for photo-ionization experiments, we propose a simple excitation model that analyzes and compares the spectral overlap of the Raman and Ti:Sapphire lasers with the Doppler-broadened atomic spectral line. We demonstrate that Raman lasers are a suitable source for resonance photo-ionization applications in this regime

Improving the Spectral Coverage and Resolution of the ISOLDE RILIS

This thesis concerns applications and developments of the Resonance Ionization Laser Ion Source (RILIS) at CERN-ISOLDE for ion beam production and laser spectroscopy. Laser developments, including the first operation of a grating-tuned Ti:sapphire combined with a thick etalon for linewidth reduction, the construction and characterization of a seeded Ti:sapphire ring cavity laser and the first demonstration of a Raman laser in the blue spectral range are presented. In-source laser spectroscopy on Dy isotopes has been performed, providing a valuable insight into the nuclear charge radii systematics near proton number $Z=64$. This work also illustrates the resolution limit imposed by Doppler-broadening of the atomic spectral lines inside the ion source. Addressing this limitation, the Doppler-free 2-photon ionization technique has been developed, leading to its first successful "in-source" application. The future of this approach to significantly increase the spectral resolution of RILIS is discussed

Resonance ionization spectroscopy of Europium: The first application of the PISA at ISOLDE-RILIS

The following work has been carried out at the radioactive ion beam facility ISOLDE at CERN. A compact atomic beam unit named PISA (Photo Ionization Spectroscopy Apparatus) has been implemented as a recent addition to the laboratory of the Resonance Ionization Laser Ion Source (RILIS). The scope of this thesis work was to demonstrate different applications of the PISA, using the existing and highly developed laser setup of the RILIS installation. In a demonstration of the suitability of PISA for ionization scheme development, a new ionization scheme for Europium has been developed. This resulted in the observation of several new autoionizing states and Rydberg series. Through the analysis of the observed Rydberg resonances a refined value of $45734.33(3)(3)$ cm$^{-1}$ for the ionization potential of the europium atom has been determined. In addition this thesis reports on the feasibility of the use of the PISA as a RILIS performance monitoring device during laser ion source operations. Finally the present work outlines future applications and upgrades of the PISA. Several modifications are recommended which will help to further improve the performance, practicality and versatility of the PISA

Ion beam production and study of radioactive isotopes with the laser ion source at ISOLDE

At ISOLDE the majority of radioactive ion beams are produced using the resonance ionization laser ion source (RILIS). This ion source is based on resonant excitation of atomic transitions by wavelength tunable laser radiation. Since its installation at the ISOLDE facility in 1994, the RILIS laser setup has been developed into a versatile remotely operated laser system comprising state-of–the-art solid state and dye lasers capable of generating multiple high quality laser beams at any wavelength in the range of 210–950 nm. A continuous programme of atomic ionization scheme development at CERN and at other laboratories has gradually increased the number of RILIS-ionized elements. At present, isotopes of 40 different elements have been selectively laser-ionized by the ISOLDE RILIS. Studies related to the optimization of the laser–atom interaction environment have yielded new laser ion source types: the laser ion source and trap and the versatile arc discharge and laser ion source. Depending on the specific experimental requirements for beam purity or versatility to switch between different ionization mechanisms, these may offer a favourable alternative to the standard hot metal cavity configuration. In addition to its main purpose of ion beam production, the RILIS is used for laser spectroscopy of radioisotopes. In an ongoing experimental campaign the isotope shifts and hyperfine structure of long isotopic chains have been measured by the extremely sensitive in-source laser spectroscopy method. The studies performed in the lead region were focused on nuclear deformation and shape coexistence effects around the closed proton shell Z = 82. The paper describes the functional principles of the RILIS, the current status of the laser system and demonstrated capabilities for the production of different ion beams including the high-resolution studies of short-lived isotopes and other applications of RILIS lasers for ISOLDE experiments

In‐Source High‐Resolution Spectroscopy Using an Integrated Tunable Raman Laser

Tunable single-frequency lasers are the most prominent tool for high-resolution spectroscopy, allowing for the study and exploitation of the electronic structure of atoms. A significant milestone relies on the demonstration of integrated laser technology for performing such a task. The device presented here is composed of a compact Fabry–Perot monolithic resonator capable of producing tunable and Fourier-limited nanosecond pulses with a MHz-class frequency stability without active cavity stabilization elements. It also has the remarkable capability of exploiting the Raman effect to funnel efficiently the broad spectrum of an input laser to a spectrally-bright Stokes pulse at hard-to-access wavelength ranges. The targeted atom for the demonstrations is 152Sm, released as an atomic vapor in a hot cavity environment. Here, the Stokes field is tuned to a wavelength of 433.9 nm, while a crossed-beams spectroscopy setup is used to minimize the Doppler broadened spectral features of the atoms. With this work, the suitability of integrated diamond Raman lasers as a high-resolution in-source spectroscopy tool is demonstrated, enabling many applications in atomic and nuclear physics. The integrated form-factor and inherent simplicity makes such a laser an interesting prospect for quantum-technology based sensing systems and related applications

In-source laser spectroscopy of dysprosium isotopes at the ISOLDE-RILIS

A number of radiogenically produced dysprosium isotopes have been studied by in-source laser spectroscopy at ISOLDE using the Resonance Ionization Laser Ion Source (RILIS). Isotope shifts were measured relative to $^{152}$Dy in the 4 f$^{ 10}$6s$^{2}$ $^5$I$_8$ (gs) $\rightarrow$ 4 f$^{ 10}$6s6p (8,1)$^8_o$ (418.8 nm$_{vac}$) resonance transition. The electronic factor, F, and mass shift factor, M, were extracted and used for determining the changes in mean-squared charge radii for $^{145m}$Dy and $^{147m}$Dy for the first time.A number of radiogenically produced dysprosium isotopes have been studied by in-source laser spectroscopy at ISOLDE using the Resonance Ionization Laser Ion Source (RILIS). Isotope shifts were measured relative to $^{152}$Dy in the 4$f$$^{10}$6$s$$^{2}$ $^{5}$ I$_{8}$ (gs)→ 4$f$$^{10}$6$s$6$p$(8,1)$_{8}^{0}$ (418.8nm$_{vac}$) resonance transition. The electronic factor, $F$ , and mass shift factor, $M$ , were extracted and used for determining the changes in mean-squared charge radii for $^{145m}$Dy and $^{147m}$ Dy for the first time

Developments at the CERN-ISOLDE Offline 2 mass separator

The Offline 2 mass separator laboratory is part of the CERN-ISOLDE Offline facilities - a suite of installations required to perform essential quality control on target and ion source units before irradiation at CERN-ISOLDE (Catherall et al., 2017) [1]. The facility is also used for extended preparatory offline studies as a prerequisite before conducting any beam development on-line, especially establishing systematic effects. The Offline 2 separator resembles the on-line CERN-ISOLDE Frontend and employs identical services such as beam instrumentation, gas delivery system, laser ionization and the equipment control system. The facility is able to generate dc as well as bunched non-radioactive beams up to an energy of 60keV. The mass resolving power of the existing 90° dipole mass separator magnet is R≈500 (Warren et al., 2020) [2]. The ion beams can be cooled and bunched in an unmodulated RFQ. In order to study effects of the RFQ buffer gas on the formation of molecular species, a dedicated identification setup is required. We intend to employ a Wien filter downstream the RFQ. This work presents initial beam dynamics simulations through the entire Offline 2 facility to prepare injection into the RFQ. The fields of the RFQ are also shown serving as a basis for field map PIC simulations. Furthermore, we present the status of the emittance meter preparations in front of the separator magnet allowing a comparison to the beam dynamics simulations

Continuously tunable diamond Raman laser for resonance laser ionization

We demonstrate a highly efficient, tunable, ∼5 GHz line- width diamond Raman laser operating at 479 nm. The diamond laser was pumped by a wavelength-tunable intra- cavity frequency-doubled titanium sapphire (Ti:Sapphire) laser operating at around 450 nm, at a repetition rate of 10 kHz with a pulse duration of 50 ns. The Raman reso- nator produced a continuously tunable output with high stability, high conversion efficiency (28%), and beam quality (M$^{2}$ <1.2). We also demonstrate that the linewidth and tunability of the pump laser is directly transferred to the Stokes output. Our results show that diamond Raman lasers offer great potential for spectroscopic applications, such as resonance laser ionization, in an all-solid-state platform