Microfabrication of high aspect ratio microtube arrays to store high density charged particles

Abstract

Fabrication of a portable high-density charged particle trap with an array of micro-Penning-Malmberg traps (microtraps) with substantially lower end barrier potentials than conventional Penning-Malmberg traps is presented [1]. The microtraps are designed for antimatter storage such as positrons. The fabrication of large length to radius aspect ratio (1000:1) microtrap arrays involved advanced techniques including photolithography, deep reactive ion etching (DRIE) of silicon wafers to achieve through-vias, gold sputtering of the wafers surfaces and inside the vias, and thermal compression bonding. The bonded stacks were gold electroplated to achieve a uniform gold surface to minimize the patch effects. Positron losses occur in experimentation by trap imperfections such as misalignment of microtraps, asymmetries, and physical imperfections on the surfaces. This paper describes the fabrication issues encountered and addresses geometry errors and asymmetries.