Experimental Measurement and Preliminary Simulation for the Gas Distribution Inside the RF Ion Trap System of MRTOF Mass Spectrometer

The MRTOF-MS (Multi-Reflection Time-Of-Flight Mass Spectrometer) is an important device to precisely measure atomic masses. An MRTOF-MS at the SHANS (Spectrometer for Heavy Atom and Nuclear Structure) consists of a cryogenic gas catcher, a radio-frequency ion trap system (RFTrap) and an MRTOF mass analyzer. The buffer gas distribution in the RFTrap directly affects on the cooling, bunching and storage of the ions and plays a key role in the formation of high-quality pulsed ion beam. The performance of the MRTOF mass analyzer is highly dependent on the quality of the incident ion beam, including characteristics such as low emission angle and low energy dispersion. Therefore, the study of the gas pressure distribution within the RFTrap is of great significance. In this work, the gas pressure distribution of the RFTrap has been measured experimentally, and the preliminary numerical simulation has been conducted by using MolFlow+ software. Through the correction and analysis of the data, the gas pressure of the key region for the ion transmission in the RFTrap, which cannot be measured directly, has been obtained. It provides an important reference for optimizing the performance of the MRTOF-MS.