Thin Film Silica Aerogel Structures for Heavy Ion Particle Detectors and Applications to Superfluid ³He

We investigate the use of high porosity silica (SiO₂) aerogel as a particle filter in heavy ion detectors to discriminate between electrons and positive ions. Our prototype device consists of silica aerogel grown in stainless steel 25µ micro-mesh that is designed to optimize electron transmission while absorbing positive ions. The samples are produced by the supercritical drying of alcogel (SiO₂ matrix suspended in methanol) imbibed in the micro-mesh, producing aerogel that fills the holes of the mesh. We then characterize the aerogel-filled mesh for homogeneity and electronic transparency using scanning electron and transmission electron microscopy (SEM and TEM). SEM analysis indicates that aerogel fills the mesh holes. TEM analysis indicates that electron transmission through aerogel-filled mesh holes is approximately half that of transmission through empty mesh holes. Other applications of this new technology include stabilization of superfluid phases of 3He and potentially their superfluid-normal-superfluid coherent structures.

W. P. Halperin, J. M. Parpia, and J. A. Sauls, Physics Today, 71, 30 (2018).