The nature of the X-ray background in the cosmos - the FON experiment

The following main scientific objectives of the FON experiment are formulated: 1) studying the distribution of the x-ray background radiation on the hemisphere using a detector with a high spectral resolution efficiency in the range from 2 to 150 keV; 2) examining the behaviour of different spectral background features (refraction at E=21 keV, about the spectral background lines E=6.4 keV and E=6.7 keV) during observations in different directions of the space; 3) searching for great scale fluctuations associated with a possible radiation of ultraclusters of galaxies; 4) searching for assimetry in the background radiation distribution as a result of relativistic effects associated with the relative movement in the surrounding space; 5) obtaining a summary of data about the solution of the question concerning the x-ray background nature; 6) investigation of the change in the flux and the spectral content of different bright x-ray radiation sources. Experimental data on distribution of the X-ray intensity in the hemisphere and the spectrum contents of the background radiation are compiled and compared. The main results about the measurements of the x-ray background have been obtained with gas proportional photon counters (1 - 60 keV) and scintillation detectors (above 20 keV), which have a comparatively low energy resolution efficiency