Characterization of a radiofrequency storage ion source using numerical simulations

Abstract A radiofrequency ion source routinely employed for laboratory astrophysics and astrochemistry experiments designated as the storage ion source was characterized using numerical simulations. The present work focuses on optimizing the storage and extraction of ions of astrophysical relevance having the $m/z$ range $3-330$, which covers most of the molecular ions detected in the interstellar medium and circumstellar envelopes. The crucial parameters for the storage of ions: radiofrequency signal frequency, $f_{RF}$ and amplitude, $V_{RF}$ were optimized, and the range of radiofrequency parameters that can be used to store ions inside the source is presented. The lifetimes of ions inside the source were estimated for various radiofrequency parameters. The difference in the lifetimes of ions of different $m/z$ was explained based on the ions' thermalization characteristics and the source's effective potential. The extraction of ions from the source was optimized, and a new design called the T-source was proposed to improve the extraction efficiency. We show that the T-source has better extraction efficiency than the original design, which is further enhanced by maintaining the source at a floating potential. Finally, we investigated the transmission characteristics of the extracted ions through a quadrupole ion guide, which may serve as an ion guide or a mass filter, leading to an ion storage device such as an ion trap or an ion storage ring.