Laser resonance ionization at ISOL facilities

About

Abstract:

Radioisotopes science is a broad-reaching field encompassing topics such as atomic and nuclear physics, astrophysics, medical applications and material science. Although some radioisotopes are naturally occurring on Earth the vast majority are available to us exclusively via artificial production in nuclear reactions. In contrast to conventional nuclear reactors, Isotope Separator On-Line (ISOL) devices couple the production, extraction, purification and transport of radioisotopes to an experiment in a single machine. This approach reduces the delivery time to as little as some tens of milliseconds, thereby enabling access to an unprecedented range of isotopes, reaching out towards rather extreme proton-to-neutron (Z:N) ratios.

ISOL facilities rely on the conversion of reaction products to ions, extracting them as an ion beam and filtering this ion beam downstream of the target and ion source assembly using an electromagnetic spectrometer. This alone does not guarantee the delivery of an isotopically pure ion beam to the experiment: in many cases element-selective ionization is also required due the to the presence of isobars (nuclear mass, A=N+Z, ambiguity) in the admixture of reaction products. Laser resonance ionization is widely considered the optimal technique for achieving this due to the efficiency, speed and complete element selectivity of the process.

In this lecture we will cover this topic by explaining how the differences in atomic structure for each chemical element can be exploited to enable selective laser ionization, and how this is achieved practically at ISOL facilities to deliver a purified beam of a certain isotope to an experiment. We will also discuss how this process itself be used as an experimental tool to study atomic and nuclear properties of these isotopes .

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