Online test of the FRS Ion Catcher at GSI

Abstract At the FRS Ion Catcher at GSI, relativistic exotic ions produced by projectile fragmentation/fission are range-focused, slowed down and thermalised in a gas-filled stopping cell, extracted and made available to high-precision experiments with ions almost at rest. It is a prototype for a gas cell system at the Low-Energy Branch of the Super-FRS at FAIR. In an online experiment, the FRS Ion Catcher was commissioned successfully with relativistic nickel fragments. The overall efficiency of the system was measured as (1.8 ± 0.3)% and can be divided into a stopping efficiency of (5.0 ± 1.1)% and an extraction and transport efficiency of (35.8 ± 9.4)%. The overall efficiency is hence limited mostly by the stopping efficiency, which could be increased in the future by operating at higher gas cell pressures. From extraction time measurements of polyatomic ions formed in the gas cell extraction times of atomic ions of 20–50 ms can be derived. The potential of the system was illustrated by the half-life measurement of 54 Co with a short half-life of 193 ms only.