Nuclear Astrophysics

EMMA set to help reveal the hearts of stars and atoms

EMMA set to help reveal the hearts of stars and atoms: In 2018, the coupling of the EMMA and TIGRESS spectrometers will mark the beginning of EMMA’s scientific program to probe the deep nature of nuclear reactions in stars and the subtleties of extreme nuclear structure. EMMA's arrival is the culmination of a multi-year series of commissioning steps successfully demonstrating the spectrometer’s enormous potential for TRIUMF's rare isotope beam program. In December 2016, commissioning of the spectrometer as a whole began with a test beam of argon-36 (36Ar) bombarding a very thick gold (Au) foil. The spectrometer was initially tuned for elastically scattered Ar ions and its first mass/charge spectrum was collected. As shown in figure A, both the 13+ and 14+ charge states were detected simultaneously, the dispersion–the key ability to distinguish between states–agreed exactly with calculations. In September 2017 an argon-40 (40Ar) beam bombarded a very thin Au target and elastically back-scattered Au ions were detected in two charge states simultaneously and used to measure the energy, angular, and mass/charge acceptances; substantially improved resolving power was observed. In November 2017, EMMA accepted its first radioactive beam, sodium-24 (24Na) which was used to induce fusion evaporation reactions on a copper target. Various fusion products with atomic masses from 80 to 85 were clearly detected and resolved in a single spectrometer setting. EMMA will use of both the light, neutron-deficient beams from ISAC and the future heavy, neutron-rich beams from ARIEL to explore radiative capture and transfer reactions that are central to astrophysical research, and fusion reactions important to the study of nuclear structure.