Graphene foils improve angular and energy resolution in neutral atom detectors while also improving mass discrimination and usable energy ranges. We developed improved grid supports and achieved areas >10 cm2 with good foil coverage and significant improvements in secondary electron yield from ~1 nm metal oxide overcoats. We present Luxel’s characterization of large-area graphene foils for applications as transmission filters and detector components.
FIRE (Far-ultraviolet Imaging Rocket Experiment) is a sounding rocket payload telescope designed to image
between 900-1100Å. It is scheduled to launch on January 29th, 2011 from the Poker Flats complex in northern Alaska.
For its first flight, it will target G191B2B, a white dwarf calibration source, and M51 (the Whirlpool Galaxy), the
science target, to help determine the number of hot, young O stars, as well as the intervening dust attenuation. FIRE
primary consists of a single primary mirror coated in silicon carbide, a 2000Å thick indium filter and a micro-channel
plate detector coated with rubidium bromide. Combined, these create a passband of 900-1100Å for the system and reject
the hydrogen Lyman-α to approximately a factor of 10-4. To ensure that the filter survives the launch, a small vacuum
chamber has been built around it to keep the pressure at 10-8 torr or lower.
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.
New generation x-ray instruments for spacecraft such as ASTRO-E and CONSTELLATION-X have very specialized requirements, notably operation at cryogenic temperatures. Luxel Corporation, under a NASA Phase I SBIR contract, undertook the demonstration of feasibility of producing polyimide films suitable for use as x-ray filter substrates specifically optimized for cryogenic applications. 5000 angstrom thick polyimide films were processed using different cure cycles, and burst pressure analyses were performed at 293, 77, and 4 Kelvin. Test data showed that polyimide films are inherently stronger at cryogenic temperatures than at room temperature. Through cure modification, film strength was increased an additional 9 percent at 4K over that of the standard cure clearly showing the feasibility of film optimization.