We report on our first X-ray imaging test of our novel ultra-lightweight and high-resolution MEMS X-ray optics for future space astronomical missions. We have fabricated a single-stage test optic made of Si from a Si (1 1 1) wafer with a thickness of 300 μm. We conducted a dry etching and made 20 μm line and space through holes to use their side walls for X-ray mirrors. We have smoothed the side walls by annealing and plastically bending the wafer to a spherical shape with a curvature of radius of 1000 mm.We have irradiated Al Kα 1.49 keV to the test optic and, for the first time, have verified X-ray focusing. An evaluated angular resolution ranged from 26 to 130 arcmin, which is two orders of magnitude worse than our goal of 15 arcsec. We found that this degraded resolution is mainly due to a large surface roughness of the side walls >10 μm scale and possibly the deformation process. An estimated X-ray reflectivity was also an order of magnitude lower than the theoretical value assuming flat side walls. We concluded that this could be due to the loss of the reflective area by the rough surface. Therefore, the future improvement on the large scale surface roughness is indispensable for the better angular resolution and effective area.
ASJC Scopus subject areas