Search

Results are presented on improvements in the performance of medium energy large area gas scintillation proportional counters for use in X-ray astronomy. By a suitable choice of gas mixture the electron transit time through the drift region can be significantly lowered with a consequent reduction in the detector dead time. In addition the electron diffusion is also reduced and this should result in an increase in the background rejection efficiency.

The in-orbit performance of the EXOSAT gas scintillation proportional counter spectrometer is presented. The background rejection capability in the EXOSAT deep orbit is examined as well as the overall detectors response. Typical examples of the spectra from cosmic X-ray sources show that this new type of detector will make a significant advance to the field of medium energy broad band X-ray spectroscopy.

A position sensitive gas scintillation proportional counter is presented for use as a broad band spectrometer in the focal plane of an imaging X-ray telescope. The 7 cm diameter detector has an on-axis position of ~ 2.5 mm and an energy resolution of ~ 10% for 6 keV X-rays. Design improvements are outlined which should provide a position resolution below ~ 1 mm at 6 keV over a useful aperture of ~ 8 cm. Such a detector, can, in conjunction with a suitable telescope, perform a spectral mapping in the range 0.1 - 6 keV of extended objects such as clusters of galaxies and supernova remnants with medium spatial resolution.

We present design performance on an high pressure parallel grids position sensitive Gas Scintillation Proportional Counters (HPGSPC). The detector has an usefull geometric area of 450 cm2, an energy resolution better than 4% at 60 KeV, a spatial resolution in the millimiters range from 3 to 120 KeV.

Experimental results obtained from a new, position sensitive, gas scintillation proportional counter are presented. The counter, for use in X-ray astronomy as a focal plane instrument in conjunction with a grazing incidence imaging telescope, features a useful aperture of ~ 7 cm, a two-stage scintillation region and a seven photomultiplier tube Anger camera read-out system. An energy resolution of ? 20% FWHM at 1.25 keV (< 10% at 6 keV) and a position resolution of 900 ?m at 6 keV at the centre of the useful aperture are achieved.

Results are presented on the development of a position sensitive gas scintillation proportional counter for use in high energy X-ray astronomy. This detector has a higher background rejection efficiency and a better energy resolution above 35 keV than conventional gas scintillators, gas proportional counters and crystal scintillators. These improvements arise directly fran the application of a discrimination technique which makes use of the detection of the fluorescent Xenon K shell photon emitted in most interactions involving the photoabsorption of genuine X-rays with energies greater than the K shell binding energy. Detectors incorporating this technique, and also having a position sensing capability to reject the induced Compton electron background fran the detector walls, will provide unique information on the spectral characteristics of cosmic X-ray sources. Such characteristics include high energy cyclotron lines fran neutron stars. The inherent imaging properties of these detectors when operated at high X-ray energies are also investigated. Such a detector when used in conjunction with a coded aperture mask will form a camera with an imaging capability of a few arc minutes at X-ray energies beyond the practical range of grazing incidence telescopes.

Results are presented on the performance of a large area gas scintillation proportional counter (GSPC) experiment for application as a spectrometer in X-ray astronomy. Two such counters will be launched on an Aries sounding rocket in 1979. This experiment has a total collecting area of 630 cm2, and an energy resolution of 11% for 6 keV X-rays. The intrinsic background rejection capability with the aid of burst length discrimination was ~ 80% for an X-ray acceptance of 80% at 6 keV.