Resonance laser ionization developments for IGISOL-4

Abstract

The work presented in this thesis concentrates on the development of the FURIOS laser ion source towards e cient and selective production of low energy radioactive ion beams. This includes design and development of the ion guide and hot cavity catcher systems for laser ion source use, and the development of in-source and in-jet laser spectroscopy techniques. The work has been carried out at the IGISOL facility in the Accelerator laboratory of the University of Jyväskylä. The FURIOS facility was upgraded and developed during the move to the IGISOL-4 facility. The laser transport was greatly improved in order to allow a large fraction of the initial laser intensity to be transported into the gas cell at the IGISOL-4 frontend. The careful design of the IGISOL frontend and the FURIOS facility enable the laser ion source to be utilized e ciently for the production of radioactive ion beams at IGISOL-4. Additionally, in order to overcome the de ciencies of the standard IGISOL ion guide design under on-line conditions, an ion guide based on an original design by the LISOL group in Leuven has been adapted the IGISOL. The shadow gas cell allows e cient resonance laser ionization in a gas cell under on-line conditions. The transport e ciency of the ion guide was determined using recoil source. Additionally, the principal operation of the ion guide was demonstrated under pseudo-on-line conditions utilizing resonance laser ionization. An inductively heated hot cavity catcher laser ion source was developed based on existing electron bombardment heated thermal ionizer design in collaboration with the JYFL ECR group. The motivation behind the development of a new type of recoil catcher at IGISOL is the production of rare isotope of silver, N=Z 94Ag. The evacuation time for the silver atoms from the catcher was measured to be less than 10 ms at a relatively low temperature of 1200 C. Though the hot cavity catcher ion source principle was demonstrated, the commissioning experiment showed the need to further develop the catcher in order to improve the beam quality and ionization e ciency. Lastly, in gas-jet spectroscopy in the form of the LIST approach was studied. Different ion guide nozzles were compared in order to nd a nozzle that would produce long collimated gas jets for the use of the LIST approach. A de Laval type nozzle was found out to be the most promising, being able to produce a well collimated jet spanning a distance of 14 cm. The jet temperature was measured to be very low, which when combined with the low pressure, makes a very attractive environment for laser spectroscopy.