Engineering topics
Publications and source records attributed to Lehan, J. P..
We discuss the instrumental aspects affecting the measurement accuracy when determining PSD with phase shifting interferometers. These include the source coherence, optical train effects, and detector effects. The use of a carefully constructed calibration standard will also be discussed. We will end with a recommended measurement and data handling procedure.
Determination of the shape of very thin x-ray mirrors employed in spaced-based telescopes continues to be challenging. The mirrors shapes are not readily deduced to the required accuracy because the mount induced distortions are often larger than the uncertainty tolerable for the mission metrology. In addition to static deformations, dynamic and thermal considerations are exacerbated for this class of mirrors. We report on the performance of one temporary mounting scheme for the thin glass mirrors for the Constellation-X mission and prospects for deducing their undistorted shapes.
We investigated the use of a simultaneous-phase acquisition interferometer (a 4D FizCamTM 1500) for determining the PSD of the extremely-high aspect ratio (500: 1) glass mirrors for the Constellation-X SXT telescope. We found that the results obtained are strongly influenced by the methodology employed while collecting the data and outline a best method for this type of measurement.
The lanthanide trifluorides show promise as vacuum ultraviolet (VUV) coating materials. The optical properties of single-layer coatings vary with deposition temperature, and with ion-beam energy and current density. The optical constants, stoichiometry, durability, moisture adsorption, and crystallinity are studied for trifluoride films made under a variety of deposition conditions.