Nuclear mass measurements and ion manipulation

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This application is for continued support of extreme accuracy mass measurements on short-lived radioactive nuclei.  The interest in such measurements is in their direct relationship to the nuclear forces that hold nuclei together, thereby determining the structure of the nuclei. These forces are so strong that the binding energy they give to a nucleus lowers its mass by a measurable amount.  Radioactive, i.e. unstable, nuclei are particularly interesting because the more unstable a nucleus the more obvious are the strengths, and weaknesses, of the nuclear forces in holding it together. However, mass measurements of short-lived radioactive nuclei are inherently much more difficult than measurements of normal, stable atoms such as exist on Earth.  This is not only because of difficulties in dealing with radioactivity but, more importantly, because the nuclei are short-lived and available only at the high-energy accelerator facilities that can produce them and, even there, only in very minute quantities. The research program proposed here uses a novel form of high-precision high-sensitivity mass spectrometer based on electromagnetic traps that has been developed by a McGill collaboration with European scientists. The first such instrument, named ISOLTRAP, was developed for the ISOLDE radioactive beam facility at CERN.  This instrument has to date allowed measurements on over 200 radioactive nuclei, the shortest half-life being 85 milliseconds.  It has also led to the construction of 5 similar spectrometers around the world, with a new generation of such a spectrometer being an essential part of the TITAN facility of ISAC at TRIUMF. An essential part of this research program is the development of apparatus to manipulate the radioactive ions efficiently into the mass spectrometer. This grant application is for further development of such apparatus, particularly using high radiofrequency quadrupole electric fields in buffer gas to manipulate the ions in miniature structures. Such techniques not only have applications in nuclear physics but also in biomolecular research and nanoscience.