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

TL;DR

This paper reports the development of an electrostatic time-of-flight detector, E-MCP, with high time resolution and efficiency, used for diagnostics and mass measurements of circulating ions in the Rare-RI Ring at RIKEN.

Contribution

The paper introduces a novel electrostatic time-of-flight detector with optimized design and demonstrates its successful application in circulating beam diagnostics and mass measurements.

Findings

Achieved time resolutions of 69 ps and 43 ps with different foils.

Approximately 90% detection efficiency for both foils.

Confirmed circulation of short-lived nuclei inside the Rare-RI 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$^\circ$ 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.