Development of an auroral X-ray imager using a two-dimensional array of Si(Li) semiconductor detectors
In order to observe aurotal X-ray images, a horizontal two-dimensional array of lithium-drifted silicon (Si(Li)) semiconductor detectors has been developed. The auroral X-ray imager has a 5 × 5 pixel array. The sensor element of one pixel is a Si(Li) detector, the area of which is 1.8 cm × 1.8 cm and the thickness of which is 0.5 cm. Noises of the Si(Li) detectors have been decreased for X-ray measurements. Although the noise signals are too large for X-ray measurements at room temperature, they become much smaller at 5° C. Thus, accurate X-ray measurements by the Si(Li) detectors are fully possible at such a low temperature. In observations by a stratospheric balloon, cooling of the Si(Li) detectors can be made by dissipation of heat to a low-temperature environment. A heat-pipe has been used to cool the Si(Li) detectors. The energy range of the auroral X-rays to be observed is from 37 to 200 keV. The horizontal two-dimensional array of the Si(Li) detectors has been placed in a pinhole collimator. The angular resolution corresponding to one pixel of the auroral X-ray imager is 15° at the central pixel. The total field of view of the imager is 62°.