Design of the Extreme Ultraviolet Explorer long-wavelength grazing incidence telescope optics

Designing optics for photometry in the long-wavelength portion of the EUV spectrum (400-900 A) poses different problems from those arising for optics, operating shortward of 400 A. The available filter materials which transmit radiation longward of 400 A are also highly transparent at wavelengths shortward of 100 A. Conventional EUV optics, with grazing angles of less, similar10 degrees , have very high throughput in the EUV, which persists to wavelengths shortward of 100 A. Use of such optics with the longer-wavelength EUV filters thus results in an unacceptably large soft x-ray leak. We have overcome this problem by developing a mirror design with larger graze angles >/=20 degrees , which has high throughput at wavelengths longer than 400 A but at the same time very little throughput shortward of 100 A.