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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 54Co with a short half-life of 193 ms only. ispartof: Nuclear Instruments & Methods in Physics Research B vol:266 issue:19 pages:4493-4497 ispartof: location:FRANCE, Deauville status: published

A gas-filled radio-frequency quadrupole has been developed, which acts as an interface between a time-of-flight mass spectrometer and an atmospheric-pressure ion source or a gas-filled ion beam stopping cell. It delivers cooled continuous or bunched beams to the mass analyzer. The radiofrequency quadrupole has been characterized and the longitudinal energy distributions, bunching efficiencies and beam losses as a function of storage time, and the duty cycle improvement have been measured. Using the bunch mode, the mass-resolving power of the time-of-flight mass spectrometer could be increased by a factor of about two and now amounts to 24 000 (full width at half maximum).

The charge-exchange contribution can dominate the energy-loss straggling of partially stripped heavy ions depending on the charge-changing cross sections and the partial stopping powers. We have studied the energy-loss straggling of few-electron uranium ions in different solids in the energy range of (200–1000) MeV/u. Our experimental data are compared with a new model taking into account realistic screening for relativistic scattering of target electrons at close impacts to derive partial stopping powers. Screening of the projectile nucleus by inner-shell electrons reduces the charge-exchange straggling compared to that pertaining to a point-like charge distribution.