Annual Report 2022

  The RCNP Annual Report summarizing our activities in FY2022 is now available.

  The Accelerator Division reported on the details of the commissioning of the refurbished AVF cyclotron and the RING cyclotron accelerator, which was restarted with the AVF cyclotron as injector, and on the first use of the beam after the restart. Although the beam intensity has not yet reached design performance, we are approaching a stable beam delivery while continuing to solve many of the problems inherent in the refurbishment process. The Accelerator Division also conducts research for future efficient and stable accelerator operation. Accelerator operation requires optimization tuning of a huge number of parameters. Similar optimization is required for ion sources, and the optimal values of parameters vary depending on the condition of the ion source on a given day. Therefore, optimization tuning has been based on experience and intuition, but with this method, beam intensity, quality, and tuning time vary from operator to operator. To solve this problem, they established a new optimization method that can achieve constant performance in a short time by using Bayesian optimization and demonstrated it using Pantechnik’s 10 GHz ECR ion source NANOGAN.

  One of the themes that is expected to see a lot of use when joint-use experiments are resumed at the cyclotron facility is non-destructive testing using muons. The MuSIC-M1 beamline, which provides a continuous muon beam, is suitable for nondestructive inspection because of its low loss due to accidental coincidence, is expected to be used in a wide range of fields. This annual report describes what elemental analysis is possible with nondestructive testing using the MuSIC-M1.

  Research on superdeformed nuclei, on which the Research Center for Nuclear Physics is particularly focusing, is also expected to make significant progress with the resumption of the cyclotron facility's operation. The 40Ca nucleus, the subject of this Annual Report, is particularly interesting because they are characterized by the coexistence of three very different shapes. An international research group led by the Research Center for Nuclear Physics has successfully observed the decay transition from the superdeformed spin-0 excited state to the spin-0 ground state using a Super-e spectrometer. Since transitions between states with completely different shapes are forbidden, this observation indicates that the superdeformed spin-0 excited state contains a small spherical component.

  RCNP also has a major commitment to hadron physics. In this Annual Report, we present the results of Latice QCD calculations of the diquark degrees of freedom in charm baryons using the HAL QCD method; preparations for the E50 experiment with a high-energy pion beam at J-PARC are also underway, and as both the studies progress, it is expected that the understanding of the diquark degrees of freedom will deepen in the near future.

Sincerely yours,

Takashi Nakano
Director of Research Center for Nuclear Physics