Energy-control and novel particle-identification methods combined with range in a multi-sampling ionization chamber for experiments using slowed-down RI beams

摘要

A method for controlling the energy of slowed-down RI beams with the goal energy of 20 MeV/u was developed at the RIKEN RI Beam Factory. The ~(93)Zr beam energy was successfully tuned to 20.2 MeV/u in a single step by adjusting its momentum selected by the first dipole magnet after a primary target. A method for particle identification was developed for the secondary reaction fragments at 50 MeV/u. The dispersive mode was applied to the ZeroDegree spectrometer to measure the momentum at the final focus F11. The reaction fragments were stopped in the multi-sampling ionization chamber (MUSIC) placed at F11, which measured the ΔE-E of the beam particles. In addition, the range R in MUSIC was determined with a resolution of 1.4 mm (σ) by using the energy ratio obtained from multi-sampled energy deposits. The atomic number was determined from the E - R correlation with a resolution of 0.15 (σ). To distinguish the charge state of the RI beam after the secondary reaction target, the range with the correction for the β dependence was combined with the mass-to-charge ratio determined from the time-of-flight and magnetic-rigidity measurements. A 5.6 σ separation was obtained between ~(92)Zr~(40+) and ~(90)Zr~(39+) using these two values.