Evaluation of the soft x-ray reflectivity of micropore optics using anisotropic wet etching of silicon wafers.

The x-ray reflectivity of an ultralightweight and low-cost x-ray optic using anisotropic wet etching of Si (110) wafers is evaluated at two energies, C K(alpha)0.28 keV and Al K(alpha)1.49 keV. The obtained reflectivities at both energies are not represented by a simple planar mirror model considering surface roughness. Hence, an geometrical occultation effect due to step structures upon the etched mirror surface is taken into account. Then, the reflectivities are represented by the theoretical model. The estimated surface roughness at C K(alpha) (approximately 6 nm rms) is significantly larger than approximately 1 nm at Al K(alpha). This can be explained by different coherent lengths at two energies.

Shaped silicon wafers obtained by hot plastic deformation: performance evaluation for future astronomical x-ray telescopes.

In order to develop lightweight and high angular resolution x-ray mirrors, we have investigated hot plastic deformation of 4 in. silicon (111) wafers. A sample wafer was deformed using hemispherical dies with a curvature radius of 1000 mm. The measured radius of the deformed wafer was 1030 mm, suggesting that further conditioning is indispensable for better shaping. For the first time to our knowledge, x-ray reflection on a deformed wafer was detected at Al K(alpha) 1.49 keV. An estimated surface roughness of <1 nm from the x-ray reflection profile was comparable to that of a bare silicon wafer without deformation. Hence, no significant degradation of the microroughness was seen.