Demonstration of waferscale voltage amplifier and electrostatic quadrupole focusing array for compact linear accelerators

Abstract

Compact linear accelerators, with beam energies in the kiloelectron volt to megaelectron volt range, have applications in medicine, neutron/X-ray generation, surface modifications, etc. The size, weight, and power of existing accelerators preclude them from mass availability in portable formats. This paper presents a specific implementation of an ion accelerator architecture based on planar wafers with accelerating and focusing sections. Our low cost approach allows the control of the final ion beam energy with potential applications, for example, for accelerator-based ion implantation. In this paper, we demonstrate two important waferscale modules required to build a linear particle accelerator; these include (1) on-wafer voltage amplification for beam acceleration using Inductor-Capacitor (LC) resonators and (2) waferscale electrostatic quadrupole arrays (ESQA) to refocus the ion beams during transport. On-board LC resonators were developed using Printed Circuit Board fabrication processes to implement an LC element resonant at ∼16.6 MHz with a quality factor of 25. An energy gain of ∼250 eV was observed using a two wafer acceleration unit with an argon ion beam with 6.5 keV initial energy. A 3 × 3 ESQA was fabricated on a glass wafer with metal electrodes formed by depositing copper metal around the beam apertures. The ESQA was used to focus and defocus an argon ion beam, demonstrating a field gradient of ∼500 V over a gap of ∼250 μm.