On a cryogenic noble gas ion catcher

In-situ purification of the gas used as stopping medium in a noble gas ion catcher by operating the device at low temperatures of 60 to 150 K was investigated. Alpha-decay recoil ions from a 223Ra source served as energetic probes. The combined ion survival and transport efficiencies for 219Rn ions saturated below about 90 K, reaching 28.7(17) % in helium, 22.1(13) % in neon, and 17.0(10) % in argon. These values may well reflect the charge exchange and stripping cross sections during the slowing down of the ions, and thus represent a fundamental upper limit for the efficiency of noble gas ion catcher devices. We suggest the cryogenic noble gas ion catcher as a technically simpler alternative to the ultra-high purity noble gas ion catcher operating at room temperature.