Spatial Variability of the Solar X-ray Spectrum below 20 Å

Abstract

X-RAY images of the Sun have recently been obtained in a number of relatively narrow wavelength bands below 20 Å. The instrument consisted of a gas-filled proportional counter with a six channel pulse-height discriminator to provide energy resolution¹. To provide spatial resolution and increase the collecting area of the detector a method discussed by Giacconi and Rossi was used². This involved the use of a grazing incidence paraboloidal mirror, a small stop in the focal plane of which limited the field of view to a half-angle α = r/(1–d) (Fig. 1). By a suitable choice of r the field of view was reduced to a fraction of that subtended by the whole Sun. An image was built up by scanning the instrument in a systematic way across the Sun.