1. Development of CCDs for the SXI We have developed 2 different types of CCDs for the SXI in parallel.. *Advantage =>They are successfully employed for current satellites. *Disadvantage =>The maximum thickness of the depletion layer is 100  m *Advantage =>mobility of major carrier is 3 times larger =>higher resistivity of silicon wafer N-type CCDs have 2-3 times thicker depletion layer than p- type. *Disadvantage =>They have never been employed onboard detectors. =>The performance for X-rays are hardly investigated. 1, P-type CCDs, fabricated on p-type Si wafer. 2, N-type CCDs, fabricated on n-type Si wafer.

2. Background of developing CCDs with thick depletion layer * Steven Holland et al. fabricated MOS CCDs with high resistivity n-type Si wafer and successfully obtained a 300  m thick depletion layer. * L. Strüder et al. developed pn-CCDs with 300  m thickness of the depletion layer, and it had already employed for XMM- Newton Development of the n-type MOS CCDs is under way with a collaboration of Osaka U., Kyoto U., NAOJ (National Astronomical Observatory of Japan) and HPK (Hamamatsu Photonics K.K.).

3. Specification of test device Specification (design value) Pixel size14.5  m x 15  m Format328 x 320 Wafer thickness200  m Depletion layer200  m Illuminated methodFI (Front illuminated) Depletion layer : 200  m electrode Fully depleted CCD 4.8 mm Schematic of cross section

4. Basic performance Basic performance was comparable to that of p-type CCD n-type CCD Energy resolution143 ± 3 eV Readout noise7 electrons Pulse height [ADU] Mn k  5.9 keV Mn k  6.5 keV escape counts Spectrum of 55 Fe 1 pixel size is 14.5 x 15 um X-ray events p-type CCD 135 eV 5 electrons X-ray image Operation temp -70 o C Readout speed 60 kHz

5. Responsivity for soft X-ray spectrum of oxygen K line We investigated the responsivity for soft X-ray by using Oxygen K line : 527 eV Energy resolution FWHM = 81 ± 1 eV We confirmed that this CCD completely collects the signal charges Because this peak has no low energy tail. Pulse height [ADU] counts Oxygen K line 527 eV This CCD have good responsivities for soft X-ray down to 0.5 keV.

6. Thickness of the depletion layer Pulse height [ADU] counts 22.4 keV 24.9 keV Spectrum of 109 Cd Thickness of the depletion layer 172 ± 13  m Energy resolution 574 eV at 22.4 keV. We measured the thickness of depletion layer from the detection efficiency. Detection efficiency Energy [keV] Solid line : 172  m Dotted line : 70  m Detection efficiency based on http://www-cxro.lbl.gov/optical_constants/

7. Future plan Depletion layer To improve the efficiency below 0.5 keV, We have developed the BI (Back illuminated) CCDs. We will evaluate the performance of this device. Schematic of cross-section electrode Large imaging area (3 x 6 cm) Photograph of engineering model FI BI