As-fabricated free-standing indium foils were found to have transmission in the 90nm to 120nm
band ranging from 10% to 70% of modeled values based on pure indium. Auger depth profiling of
the as-deposited indium showed little surface contamination and high purity. However, final freestanding
filters were found to have heavy contamination, particularly on the surface. An
argon/hydrogen plasma bombardment was developed which improved EUV transmission by 50% to
500% in the finished filters without causing significant pinholes to develop in the foils or
appreciably affecting blocking characteristics.
NASA will fly x-ray microcalorimeters on several mission payloads scheduled within the next 5 years. New and
improved blocking filters are urgently needed to realize the full potential and throughput of these missions. High
transmission polyimide support mesh is being developed as an alternative to the nickel mesh currently used in blocking
filter designs. Polyimide's composition affords high transparency to x-rays, especially above 3 keV. A new filter
fabrication technique that simplifies assembly, eliminates adhesives from the filter field, and creates a stronger foil/mesh
bond than epoxy, has also been demonstrated. In addition to support mesh, embedded resistive traces are being
developed to provide deicing capability to actively restore filter performance in orbit. This report details the progress of
this research to date.
The Solar X-ray Imager (SXI) was launched 24 May 2006 on Geostationary Operational Environmental Satellite
(GOES-13). SXI is a grazing incidence X-ray telescope that focuses an image of the Sun onto a CCD detector
through a set of selectable filters. The X-ray image data are transmitted at the rate of at least one image per minute,
which permits the reconstruction of near-real-time solar images in the 6-60Å range (photon energy 2000-200 eV).
Thin film filters consisting of aluminum, titanium, and polyimide are used in the entrance of the telescope to
eliminate visible light. During the first six months of on-orbit operations the amount of stray light transmitted
increased approximately linearly with time, consistent with the formation of small (less than 50 micron) pinholes. A
laboratory investigation was initiated and witness sample filters were subjected to energetic particles simulating the
on-orbit radiation environment and their quality was assessed using visible light-leak testing and scanning electron
microscope imaging. It was concluded that galvanic corrosion of aluminum and titanium initiates pinholes that
subsequently grow in dendritic fashion by spalling off of aluminum to relieve the internal film stress. The test
program also revealed that the geostationary radiation dose level can damage polyimide and lead to filter failure.
Radiation damage may have been responsible in part for the increased light levels observed in the GOES-12 SXI and
with increased exposure a similar observation could manifest on GOES-13 SXI. This paper presents the
methodology and results for the entrance filter test program for the GOES SXI telescopes and presents recommended
improvements for future instruments.