Gamma-Ray Spectroscopy at the Isotope Separator and Accelerator (ISAC)

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The atoms of all elements are composed of electrons orbiting a tiny massive core, the atomic nucleus. The nucleus is, in turn, composed of smaller objects called protons and neutrons or, collectively, nucleons. These nucleons interact with each other by all of the known forces of nature, making the atomic nucleus an ideal "laboratory" for studying a wide range of topics of basic scientific interest, from the properties of the fundamental interactions of subatomic particles to how the nucleus as a whole behaves as a collective entity.The use of the atomic nucleus as a laboratory for basic science research has been constrained by the small subset of the possible combinations of protons and neutrons (isotopes) occurring naturally on Earth. A great expansion of this field of science is, however, being made possible by the development of research facilities such as the Isotope Separator and Accelerator (ISAC), and its new expansion to the Advanced Rare IsotopE Laboratory (ARIEL) at the TRIUMF facility in Vancouver, British Columbia. ISAC produces world-record intensities of short-lived isotopes and delivers them to research scientists in the form of high-quality ion beams. In the present research, the high-frequency light (gamma-rays), neutrons, and charged particles emitted when rare isotopes produced at ISAC decay or interact with other nuclei will be measured in state-of-the-art detector arrays known as GRIFFIN, TIGRESS, and SPICE, designed and constructed by a collaboration of researchers from Canadian universities and TRIUMF. These measurements will support a broad program of basic science research, ranging from precision measurements of the weak interactions of subatomic particles called quarks, through studies aimed at a better understanding of how the chemical elements are synthesized in the explosions of stars, to experiments designed to unravel how the atomic nucleus responds to the stresses of unusual neutron-to-proton ratios. The world leading combination of the ISAC facility, its upgrade to ARIEL, and the sophisticated detection systems employed in these studies, will ensure that Canadian scientists remain at the forefront of the emerging field of rare isotope research.