Speaker
Description
The atomic masses are most fundamental physical quantity and is the indicator that determines its existence and stability of nuclides. Comprehensive mass measurements provide us with important information to enhance our knowledge of physics in extreme regions, such as the astronomical r-process and the origin of Uranium.
The multi-reflection time-of-flight mass spectrograph (MRTOF-MS)[1] is one of the mass measurement device for the heavy elements. Recently a state-of-the-art detector referred to as an $\alpha$-TOF[2] has been developed and installed to MRTOF-MS. The $\alpha$-TOF detector can measure ion implantation to deduce the time-of-flight (TOF) and subsequent α-decay and fission (spontaneous fission (SF), $\beta$-delayed fission, etc.) events from implanted ions simultaneously, which can discriminate ``true" events from background events. We have recently succeeded in the direct mass measurement of the superheavy nuclides $^{257}$Db[3], which had a count rate of about two events per day.
Furthermore, we have initiated the new field of nuclear spectroscopy using the decay-correlated mass measurement[4]. This value of the technique was initially demonstrated by using the decay properties to discriminate and mass analyze the isomeric state of nuclides, which could not be resolved from the ground state using the TOF spectrum of MRTOF.
Recently we have developed $\beta$-TOF[5], an improved version of $\alpha$-TOF, and extended its measurement areas to include $\beta$-decaying nuclides.
In this talk, we will introduce the technique of the decay correlated mass measurement using MRTOF and $\alpha$/$\beta$-TOF.
[1] P. Schury et al., Nucl. Instrum. Methods. Phys. Res. B, 335, 39 (2014).
[2] T. Niwase et al., Nucl. Instrum. Methods. Phys. Res. A, 953, 163198 (2020).
[3] P. Schury et al., Phys. Rev. C 104, L021304 (2021).
[4] T. Niwase et al., Phys. Rev. C 104, 044617 (2021).
[5] T. Niwase et al., to be submitted.
