The laser ionization technique for ISOL Radioactive Ion Beam facilities
by
Iain D. MOORE(University of Jyväskylä, Dep. of Physics, Finland)
→
Europe/Rome
LNL Meeting Room (INFN LNL)
LNL Meeting Room
INFN LNL
Description
Since its conception in the 1980’s, the resonant laser ionization ion source has been established as a reliable and efficient on-line ion source for the selective production of radioactive ion beams (RIBs). Laser ion sources are fast becoming an integral part of new facilities (for example HIE-ISOLDE, SPIRAL2, RIBF in RIKEN and FRIB in the USA do or plan to incorporate such technology). Historically dye laser systems have been the predominant and pioneering working horses for laser ion source applications up to recently, but the development of all solid-state Titanium:Sapphire laser systems has initiated a significant evolution in this field.
The thick target ISOL method excludes the production of some elements completely either due to fast chemistry with the target material or a very low vapour pressure and slow diffusion time. The ion guide method of production utilizes thin targets and a buffer gas as a stopping and extraction medium. This results in a universal production of all elements with extraction times approaching 1 ms and below. However, the IGISOL method suffers from no Z selectivity which can result in overwhelming background contributions when trying to probe the most exotic species, for example in fission reactions. Incorporation of laser ionization and a gas cell is a rather more complex procedure than with a hot cavity ion source however this has been pioneered successfully at Louvain-la-Neuve and will be one of the main priorities in the new Rare Isotope Beam Science facility, Jyväskylä.
More innovative approaches involve the so-called Laser Ion Source Trap method (LIST) which is under development at Mainz, Louvain-la-Neuve and at Jyväskylä. The LIST technique would offer the highest selectivity for RIB production, and current efforts are focused on improvements in efficiency in order to make it compatible with more standard in-source ionization. In parallel, solid state laser developments are continually being made between a network of several facilities. These include intra-cavity frequency doubling, grating-based lasers for better wavelength tuning and injection-seeded lasers for in-source spectroscopy. This latter method of spectroscopy can utilize the same infrastructure of a laser ion source and is a very attractive means of extracting fundamental nuclear structure information (nuclear spins, moments and changes in mean-square charge radii) of very weakly-produced, short-living radioactive nuclei.
In this talk I will present the status of a wide range of the above topics, from the laser ion source technique, to laser developments, to spectroscopy in-source. I will take examples from the IGISOL facility at JYFL and also present the status of other laser ion source facilities.
