Аңдатпа
Abstract This paper presents numerical modeling of a pulsed ring ion source and the ion-optical system of a time-of-flight mass spectrometer with an axially -symmetric electrostatic mirror. The relevance of this study is determined by the fact that, in the considered electrostatic mirror configuration, ions must be introduced as a ring-shaped packet, whereas conventional ion sources generally form a beam in the shape of a small spot near the symmetry axis of the system. In this regard, a pulsed ring ion source configuration is proposed and numerically investigated, enabling the formation, extraction, and preliminary acceleration of a ring-shaped ion packet. It is shown that modifying the source geometry, reducing the accelerating gap, and introducing a correcting cylindrical electrode make it possible to reduce the effect of potential sagging, and ensure ion transmission to the entrance of the mass analyzer under conditions of strong preliminary acceleration The high efficiency of axially-symmetric electrostatic mirrors is due to their ability to provide simultaneous spatial and time-of-flight focusing of ion packets. The electrode system of such a mirror is formed by cylindrical electrodes sharing a common axis, which is consistent with the ring geometry of ion injection and enables the implementation of the two spatial and timeof-flight focusing modes, namely "ring-to-axis" and "axis-to-ring". The potential distribution in such a system is represented in a relatively simple analytical form. To determine the trajectories and flight times of charged particles in the electrostatic field of the deflector, dimensionless Newtonian equations are used; these equations are integrated by the Adams method with automatic selection of the integration step. The starting values required for the integration were determined using Krylov's method of successive approximations, and the relative integration accuracy was set to 10 -9 . The calculation of spatial focusing and the arrival time of particles at the detector plane was performed using the Monte Carlo method, with normally distributed events within a specified range of initial parameters. The simulations demonstrated that the resolving power of the time-offlight mass spectrometer can be increased up to 5000 at 50% of the peak height, which makes the proposed system promising for compact high-sensitivity spaceborne mass spectrometers. The proposed TOF-MS configuration is intended for the analysis of low-energy ions in gas-phase applications, with particular emphasis on compact spaceborne instruments for planetary atmospheric and cometary composition measurements.