A flexible open-access wire bonder for the ISOLDE Solenoidal Spectrometer upgrade project

The elements we see around us and that constitute our bodies are predominantly stable, yet we know these were forged in violent astrophysical scenarios such as neutron star mergers that are still ongoing in our universe. The synthesis of the elements in these explosive scenarios involves nuclear reactions involving unstable nuclei. The unknown structure and reactions of these unstable nuclei critically affects our understanding of the origin of elements and as we have begun to explore the properties of these nuclei, surprising results have been found on the evolution of shell structure. These indicate that what we find in stable nuclei cannot be simply extrapolated to unstable systems. Nature is far richer and more diverse than we anticipated, leading to new shell structures driven by the underlying nature of the nuclear interaction. The locations of these shell structures are subtly and intimately associated with the shapes of nuclei. Investigating this science requires precision measurements of the structure and reactions of unstable nuclei. In a recently completed project we constructed the ISOLDE Solenoidal Spectrometer that was designed to do just this at ISOLDE (CERN), which is the world's leading facility for the production and acceleration of radioactive ion beams. The spectrometer uses silicon strip detectors that are read out using ASICs and these have to be connected together to produce the experimental data. The thousands of electrical connections are made using thin wires that are bonded ultrasonically. This is the technology underpinning the silicon trackers found at the heart of all four main LHC experiments, as well as in a host of spectrometers for low-energy nuclear physics experiments. Through this grant we will buy a new wire bonder to make prototype detector systems and detector modules for the planned upgrades of the ISOLDE Solenoidal Spectrometer that will open up new opportunities for studying the properties of nuclei that are only usually to be found in exploding stars.