Indirect methods in nuclear astrophysics

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Nuclear reactions that occur in stars and stellar explosions produced the chemical elements out of which the Earth and all living beings are made. They also generate the solar energy that sustains life on Earth. A quantitative understanding of the formation of the elements requires both theoretical models of the environments in which they are produced and detailed experimental knowledge of relevant nuclear reaction rates. Some of these reaction rates can be measured directly in the lab, provided the requisite nuclear beams and targets are available. Many of the important nuclei are radioactive, and can only be produced in small amounts before they disintegrate. This implies that many direct measurements are impossible to make with sufficient precision in a reasonable amount of time. Accordingly, we must often resort to indirect measurements of the properties of nuclei involved in astrophysically important reactions. These indirect measurements can provide the same information that direct measurements do. Indirect measurements in nuclear astrophysics require elaborate electromagnetic spectrometers to sift through the products of nuclear reactions in order to find the important ones that are usually produced in very small amounts. These electromagnetic filters allow the determination of the masses and electric charges of nuclei produced in nuclear reactions. I have begun design work on a new recoil mass spectrometer called EMMA (Electromagnetic Mass Analyser) that will allow these important measurements in nuclear astrophysics to be carried out at TRIUMF, Canada's national laboratory for nuclear and particle physics. EMMA will enable scientists at TRIUMF to exploit the intense beams of radioactive nuclei provided by the new ISAC-II accelerator to determine astrophysical reaction rates. This grant will fund my work on EMMA and my other efforts in indirect nuclear astrophysics, as well as support the graduate students and postdoctoral research associate I supervise.