A laser ablation carbon cluster ion source for the FRS Ion Catcher

Abstract

A Laser Ablation Carbon Cluster Ion source (LACCI) has been developed and commissioned at the FRS Ion Catcher at GSI. It is the first laser ablation ion source for long-term measurements with a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). This is enabled by two key developments: (i) a two-dimensional movable target platform that ensures the long-term stable production of ions and (ii) a mass filter for the isolation of the ions of interest. LACCI is capable of providing closely-spaced reference ions in the mass range up to ∼300 u for accurate mass measurements of exotic nuclei (relative mass uncertainty ∼10−8) and systematic studies of the mass uncertainties with the multiple-reflection time-of-flight mass spectrometer. Investigations of the laser energy and repetition rate and long-term measurements have been carried out with carbon targets (Sigradur®, Fullerene) and metallic targets (silver, gold, copper, tungsten, and erbium). In a test experiment, LACCI has delivered a stable ion current for more than 20 h at a laser repetition rate of 100 Hz, corresponding to an operation for one week at 10 Hz. It thus fully satisfies the requirements for long-term accurate mass measurements of exotic nuclei with an MR-TOF-MS. This enables the access of exotic ions, detected with rates as low as 0.1 per hour at the FRS Ion Catcher.