Development of an RF-carpet gas cell coupled to the RIKEN gas-filled recoil ion separator for chemistry of superheavy elements

We report the development of a buffer-gas stopping cell equipped with a radiofrequency (RF) carpet (RF-carpet gas cell) that is coupled to the RIKEN gas-filled recoil ion separator (GARIS) to rapidly extract ions of superheavy elements (SHEs) into chemistry apparatuses. We measured extraction efficiencies and times of ²²⁰Rn ions recoiling from a ²²⁴Ra source under various conditions. When the He gas introduced into the gas cell was cooled to 59–75 K, the extraction efficiency reached 68–77%. The extraction efficiency for room-temperature He gas was found to vary in the range of 19–63% depending on the He-gas pressure and the travel distance of ions. The extraction times of ²²⁰Rn ions were in the range of 7–107 ms. The high extraction efficiencies and the short extraction times indicate that this apparatus is applicable to the chemical studies of SHEs with half-lives as short as several tens of milliseconds. Moreover, we will be able to investigate chemical reactions between SHE ions and gaseous molecules in an ion trap by using low-energy SHE ion beams supplied by this apparatus.