Determination of the extraction efficiency for ²³³U source α-recoil ions from the MLL buffer-gas stopping cell

Following the α decay of ²³³U, ²²⁹Th recoil ions are shown to be extracted in a significant amount from the MLL buffer-gas stopping cell. The produced recoil ions and subsequent daughter nuclei are mass purified with the help of a customized quadrupole mass spectrometer. The combined extraction and mass purification efficiency for ²²⁹Th³⁺ is determined via MCP-based measurements and via the direct detection of the ²²⁹Th α decay. A large value of (10±2)% for the combined extraction and mass purification efficiency of ²²⁹Th³⁺ is obtained at a mass resolution of about 1u/e. In addition to ²²⁹Th, also other α-recoil ions of the ^{233, 232}U decay chains are addressed. (orig.)