Joint European x-ray monitor (JEM-X): x-ray monitor for ESA's INTEGRAL mission

JEM-X will extend the energy range of the gamma ray instruments on ESA's INTEGRAL mission (SPI, IBIS) to include the x-ray band. JEM-X will provide images with arcminute angular resolution in the 2 - 60 keV band. The baseline photon detection system consists of two identical, high pressure, imaging microstrip gas chambers, each with a collecting area of 500 cm(superscript 2). They view the sky through a coded aperture mask (0.5 mm tungsten) at a separation of 3.4 m. The two detector boxes are formed from 2 mm thick stainless steel plate and are filled with 5 bar Xe. The field of view is defined by the collimator mounted on top of the detector. Each collimator consists of an array of bonded square tubes of Mo. The internal surface of these tubes is covered by a graded shield. The collimator provide also the support for the detector windows which are made out of 250 micrometer thick beryllium foils. The detector sensor elements consists of microstrip plates shaped as regular octagons with a diameter of 292 mm. The basic microstrip pattern is similar to the one chosen for the HEPC/LEPC detector system on SRG. The detector position resolution will be sufficient to ensure an angular resolution for JEM-X of better than 3 arcmin throughout the 2 - 60 keV band.