Development and operation of an electrostatic time-of-flight detector for the Rare RI storage Ring

Abstract

An electrostatic time-of-flight detector named E-MCP has been developed for quick diagnostics of circulating beam and timing measurement in mass spectrometry at the Rare-RI Ring in RIKEN. The E-MCP detector consists of a conversion foil, potential grids, and a microchannel plate. Secondary electrons are released from the surface of the foil when a heavy ion hits it. The electrons are accelerated and deflected by 90 • toward the microchannel plate by electrostatic potentials. A thin carbon foil and a thin aluminum-coated mylar foil were used as conversion foils. We obtained time resolutions of 69(1) ps and 43(1) ps (standard deviation) for a 84 Kr beam at an energy of 170 MeV/u when using the carbon and the aluminum-coated mylar foils, respectively. A detection efficiency of approximately 90% was obtained for both foils. The E-MCP detector equipped with the carbon foil was installed inside the Rare-RI Ring to confirm particle circulation within a demonstration experiment on mass measurements of nuclei around 78 Ge produced by in-flight fission of uranium beam at the RI Beam Factory in RIKEN. Periodic time signals from circulating ions were clearly observed. Revolution times for 78 Ge, 77 Ga, and 76 Zn were obtained. The results confirmed successful circulation of the short-lived nuclei inside the Rare-RI Ring.

First Application of Mass Measurements with the Rare-RI Ring Reveals the Solar r -Process Abundance Trend at A=122 and A=123Li1, Naimi2, Sprouse3 et al. 2022Phys. Rev. Lett.Self Cite24110View full textAdd to dashboardCite

“…Therefore, to accept the quasi-continuous beam from the SRC, the individual self-injected trigger technique was developed for injecting pre-identified particles of interest [15]. The particle identification (PID) was achieved by the ∆E-TOF method in the beam line, where ∆E is the energy loss measured by the ionization chamber (IC) placed at F3 and TOF is the time-of-flight measured by the plastic scintillator at F3 and the E-MCP detector [16] at S0 of the SHARAQ spectrometer. Also a 2-mm thick plastic scintillator was placed after the IC at F3 to get a rough ∆E information needed for removing contaminants [17].…”

A comparison between Geant4 simulation and experiment for time-of-flight measurement

“…Generally, the transport time of electron from carbon foil to MCP is several hundred ps with several dozes of ps of deviation. 18,19) Efficiency is defined as formula 3,…”

First application of mass measurement with the Rare-RI Ring reveals the solar r-process abundance trend at A=122 and A=123

“…Therefore, to accept the quasi-continuous beam from the SRC, the individual self-injected trigger technique was developed for injecting pre-identified particles of interest [14]. The particle identification (PID) was achieved by the ∆E-TOF method in the beam line, where ∆E is the energy loss measured by the ionization chamber (IC) placed at F3 and TOF is the time-of-flight measured by the plastic scintillator at F3 and the E-MCP detector [15] at S0 of the SHARAQ spectrometer. Also a 2-mm thick plastic scintillator was placed after the IC at F3 to get a rough ∆E information needed for removing contaminations [16].…”