Speaker
Description
Precision atomic mass measurements are of great importance throughout nuclear physics. Within RIKEN's RIBF, we perform high-precision atomic mass measurements at three multi-reflection time-of-flight mass spectrographs with two more coming soon. These will allow us to cover the full range of nuclides, from the light halo nuclei to the superheavy elements. In addition to mass measurements, we have devised detectors to allow simultaneous and correlated decay spectroscopy as well.
Better understanding of the forces which bind the heaviest elements can be achieved through precision determination of atomic masses, as such measurements provide direct insight to the nuclear binding energy. This can provide insight into the upper bounds of nuclides, the existence and location of the predicted "island of stability", and the mass flow at the upper reaches of the rapid neutron capture process via fission recycling. To perform meaningfully precise atomic mass measurements of such nuclides requires a method which can achieve high resolving power, is amenable to extremely low yields, and can tolerate a large relative rate of contaminants. Multi-reflection time-of-flight mass spectrometry is one such method, as it offers resolving powers approaching 10^6 while not only tolerating a reasonably high contaminant rate but utilizing contaminants as reference ions when possible. The technique also allows the use of combined spectroscopy by adding decay detectors to the ion implantation detector used for time-of-flight determination. In this way low-yield radioactive ions typical in superheavy nuclide research can be confirmed via decay spectroscopy to facilitate measurements with very low total counts. We will describe results and future plans for such measurements at both the SHE-Mass and KISS-1.5 facilities located within the RIKEN Nishina Center.
To fully understand the rapid neutron capture process, the masses and lifetimes of neutron-rich nuclides is vital. At the end of the ZeroDegree beam line we have implemented a gas cell and MRTOF along with a host of decay detectors. This allows for simultaneously performing in-beam gamma-ray spectroscopy, precision atomic mass measurements, and decay studies of the neutron-rich nuclides. A planned upgrade of the gas stopping cell, along with development of a second gas stopping cell and MRTOF for installation at a highly dispersive position in the BigRIPS beam line (SLOWRI), will allow access to even more neutron-rich species as well as light species such as $^{14}$Be and $^{19}$B in the coming years. We will also discuss recent measurements from the ZeroDegree MRTOF, planned upgrades of ZeroDegree end station, and the also touch on plans for the full SLOWRI MRTOF measurements station.