Flight CCD selection for the x-ray CCD camera of the Monitor of All-sky X-ray Image and mission onboard the International Space Station

Abstract

MAXI, Monitor of All-sky X-ray Image, is an X-ray observatory on the Japanese Experimental Module (JEM) Exposed Facility (EF) on the international space station. MAXI is a slit scanning camera which consists of two kinds of X-ray detectors: one is a one-dimensional position-sensitive proportional counter with a total area of ~5000 cm 2 , the Gas Slit Camera (GSC), and the other is an X-ray charge-coupled device (CCD) array with a total area ~200 cm 2 , the Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular dimension of 1degree X 180degree while the SSC subtends a field of view with an angular dimension of 1degree times a little less than 180degree. In the course of one station orbit, MAXI can scan almost the entire sky with a precision of 1degree and with an X-ray energy range of 0.5-30keV. So far, we have fabricate 25 CCDs for flight candidates and production of devices are still continued. We need to select 32 and 16 CCDs to install a flight camera and a spare camera, respectively. We therefore developed the efficient screening method using 55 Fe sources. The key parameters of the CCDs for the screening are readout noise, dark current, charge transfer efficiency, and detection efficiency. The performance criteria used to rank devices are discussed.