Hydrogen Cells as Narrow-Band Geo-Coronal Lyman-Alpha Rejection Filters for Astrophysical Photometry

摘要

The Johns Hopkins University rocket group is seeking to develop a hydrogen absorption cell to act as narrowband H I Lya rejection filters for ultraviolet solar blind imaging detectors. A heated tungsten filament in the cell produces free atomic hydrogen by dissociation of molecular hydrogen contained in the cell. This creates a gas that is optically thick to the Lya, effectively filtering out incident geo-coronal Lya emission. This suppression of geo-coronal light will in principle make possible imaging observations of astrophysical sources into the far-UV below 1200 A, down to the lithium-fluoride transmission edge near 1040 A. The flux attenuation of a hydrogen cell has been measured in a vacuum monochrometer testbed. The goal is to produce a usable hydrogen cell design that can be easily mounted on a detector for photometric observations of astronomical sources in the far-UV.