X-ray Focusing Telescopes Research Articles

A focusing X-ray telescope monochromator

In order to resolve clusters of X-ray lines emitted by flares (Fritz et al , 1967; Neupert and Swartz, 1970) and to determine line shapes, a considerable resolving power is needed. The angular size of flares, typically about 2’ will not allow the necessary resolution to be obtained without a very fine slit system combined with the flat crystal X-ray spectrometer. In stellar X-ray spectroscopy large plane diffracting crystals will be associated with large counters, which in turn would act as a source of considerable noise.

A focusing X-ray telescope for use in the study of extraterrestrial X-ray sources in the energy range 20–140 keV

We have designed and tested a focusing X-ray telescope with an angular resolution (FWHM) of 1.0° for the study of extraterrestrial X-ray sources in the energy range 20–140 keV. The telescope's lens is an array of rock salt crystals (each of which is approximately one inch square), mounted on a 6-ft-diameter paraboloidal frame. The lens is located 9.5 ft above a 2-in.-diameter NaI crystal and PM tube (which measures the energy of the incident X ray). X rays passing through the salt crystals undergo a 2θ deflection if the Bragg condition for reflection, nλ = 2d sin θ, is approximately satisfied. Optimum thickness and effective energy bandwidths for such reflections have been determined for energies in the telescope's operating range. The area-efficiency product of the lens is approximately 8 times the NaI crystal area from 20 to 40 keV, giving a real improvement in the signal-to-background ratio. Crystals more nearly perfect than rock salt offer the possibility of increased gain over narrow energy intervals. Polarization measurements of the incident X rays may also be made.