Fabricating subcollimating grids for an x-ray solar imaging spectrometer using LIGA techniques

Reid A. Brennen; Michael H. Hecht; Dean V. Wiberg; Steven Manion; William D. Bonivert; Jill M. Hruby; Marcus L. Scholz; Timothy D. Stowe; Thomas W. Kenny; Keith H. Jackson; Chantal G. Khan Malek

doi:10.1117/12.222650

26 September 1995 Fabricating subcollimating grids for an x-ray solar imaging spectrometer using LIGA techniques

Reid A. Brennen, Michael H. Hecht, Dean V. Wiberg, Steven Manion, William D. Bonivert, Jill M. Hruby, Marcus L. Scholz, Timothy D. Stowe, Thomas W. Kenny, Keith H. Jackson, Chantal G. Khan Malek

Author Affiliations +

Proceedings Volume 2640, Microlithography and Metrology in Micromachining; (1995) https://doi.org/10.1117/12.222650
Event: Micromachining and Microfabrication, 1995, Austin, TX, United States

Abstract

We are fabricating sub-collimating X-ray grids that are to be used in an instrument for the High Energy Solar Spectroscopic Imager (HESSI), a proposed NASA mission. The HESSI instrument consists of twelve rotating pairs of high aspect ratio, high Z grids, each pair of which is separated by 1.7 meters and backed by a single Ge detector. The pitch for these grid pairs ranges from 34 micrometers to 317 micrometers with the grid slit openings being 60% of the pitch. For maximum grid X-ray absorbing with minimum loss of the solar image, the grid thickness-to-grid-slit ratio must be approximately 50:1, resulting in grid thicknesses of 1 to 10 millimeters. For our proof-of-concept grids we are implementing a design in which a 34 micrometers pitch, free-standing PMMA grid is fabricated with 20 micrometers wide slits and an 800 micrometers thickness. Stiffeners that run perpendicular to the grid are placed every 500 micrometers . After exposure and developing, metal, ideally gold, is electrodeposited into the free-standing PMMA grid slits. The PMMA is not removed and the metal in the slits acts as the X-ray absorber grid while the PMMA holds the individual metal pieces in place, the PMMA being nearly transparent to the X-rays coming from the sun. For optimum imaging performance, the root-mean-square pitch of the two grids of each pair must match to within 1 part in 10000 and simultaneous exposures of stacked sheets of PMMA have insured that this requirement is met.

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Reid A. Brennen, Michael H. Hecht, Dean V. Wiberg, Steven Manion, William D. Bonivert, Jill M. Hruby, Marcus L. Scholz, Timothy D. Stowe, Thomas W. Kenny, Keith H. Jackson, and Chantal G. Khan Malek "Fabricating subcollimating grids for an x-ray solar imaging spectrometer using LIGA techniques", Proc. SPIE 2640, Microlithography and Metrology in Micromachining, (26 September 1995); https://doi.org/10.1117/12.222650

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