Design and optimization of an on-chip electrostatic injector for a miniaturized proton/ion linear accelerator

¹ NEXT research unit, Sensors and Devices Centre, Fondazione Bruno Kessler - Trento, Italy
² Università degli Studi di Trento - Trento, Italy
³ Trentino Institute of Fundamental Physics, TIFPA - Trento, Italy
⁴ Fondazione Bruno Kessler, Sensors and Devices Centre - Via Sommarive 18, Trento, Italy

Received: 20 February 2026
Accepted: 30 April 2026

Abstract

This paper presents a feasibility study and the design of a miniaturized electrostatic pre-accelerator stage for protons and ions, based on standard Si/SiO₂ technology. Numerical simulations and 3D electromagnetic modelling were performed to optimize the accelerating gradient and control the longitudinal field components within the cavity. Several electrode geometries were evaluated, including planar and toothed configurations, each having a total length of 1 mm. Particle transport analysis demonstrates that protons can reach a final kinetic energy of approximately 99.5 keV, while alpha particles reach nearly 149 keV, when accounting for the combined contribution of the source and injector terminal energies. A comparative analysis highlights a critical trade-off between beam collimation and transmission efficiency: while corrugated geometries offer superior confinement, the tapered planar design ensures 100% particle transmission, identifying it as the most robust configuration. This work demonstrates the feasibility and potential of ultra-compact, passive electrostatic focusing systems for heavy-ion injection, thereby advancing the development of portable particle sources. Such sources are highly relevant for nuclear applications (e.g., compact neutron generators), materials characterization techniques, and medical applications, including proton therapy and high-energy proton imaging.