<title>Development of balloonborne hard x-ray telescopes using a multilayer supermirror</title>

Abstract

We present new results in the development of high throughput hard x-ray telescopes with multilayer supermirror coatings. Basic techniques to make the supermirror are at first developed in deposition of constant d spacing multilayers. The reflector of multilayer on the float glass achieves high reflectivity, limited by the surface roughness of substrate, while, we need more improvement in getting comparable reflectivity of multilayers on the replica foil. We put the mask just in front of sample, it reduced the nonuniformity of the thickness less than 2%. In order to maximize the effective area and field of view, we have optimized the supermirror parameters; d spacing, number of layer pairs, and thickness ratio of heavy and light element. Multiblock method is introduced to design the supermirror, and it gives high reflectivity of approximately 30% in the 25 - 40 keV band. A test supermirror sputtered on a glass sample exhibits reasonable reflectivities of about 20 - 30%. We designed a telescope system with 45 cm diameter, 20 cm mirror length in two stage, and focal length of 8 m. The effective area of four such telescopes is 320 cm2 for the x rays between 25 and 40 keV. We plan the application of this type of telescope to the balloon experiment named InFOC(mu) S to reveal hard x-ray images of clusters of galaxies or supernova remnants.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.