Quantum efficiency of the CCD camera (XIS) for the ASTRO-E mission

We measured the optical and the X-ray transmission of the optical blocking filters for the X-ray Imaging Spectrometers (XISs) which are the X-ray CCD cameras of the ASTRO-E satellite. We conclude that the oxidation of the aluminum reduces the optical transmission down to ∼60–70% of the theoretical value of the aluminum. We achieved optical transmission below 5×10−5 in the range from 4000 to 9500 Å by using aluminum thickness of 1200 Å, while the theoretical calculation requires 800 Å. The measurement of absolute quantum efficiency of XIS is also performed at several particular energies. We confirmed 20% quantum efficiency at 0.5 keV for the XIS engineering model (XIS EM).