Diffuse X-ray Spectrometer (DXS) Recent Results

The Space Physics Group and the Space Science and Engineering Center of the University of Wisconsin have designed and built a pair of novel detectors, the Diffuse X-ray Spectrometer (DXS), for the spectroscopic study of the diffuse X-ray background. Each detector consists of a one foot by two foot, curved lead stearate crystal panel that reflects X-ray photons according Bragg's law into a large position-sensing proportional counter. The detectors, collecting X-ray photons between 42 Angstroms and 83 Angstroms with Delta lambda (FWHM) ~ 2.5 Angstroms, were exposed to the X-ray background for about 40,000 seconds on Space Shuttle flight STS 54 in 1993. We present the DXS spectra and demonstrate the accuracy of the wavelength scale (0.3 Angstroms), flat-field response (corrected to better than 3%), absolute flux calibrations ( ~ 10%), and detailed agreement of the spectral shape of the instrument response to three mono-energetic input sources. The quality and accuracy of the in-flight spectra and response functions are more than adequate to place serious constraints on theories concerning the origin and nature of the diffuse X-ray background. Fits to several current models will be shown.