G. Manzo

Performance characteristics of a gas scintillation spectrometer for X-ray astronomy

Abstract The determination of the optimum electrical parameters of a spherical electric field gas scintillation spectrometer for X-ray astronomy is described. Detailed measurements using a collimated 55Fe 5.9 keV X-ray source are presented leading to trade-offs of drift field, shaping and scintillation field in an endeavour to provide a uniform response in terms of energy and time resolution over the full aperture of 314 cm2. The optimized uncollimated energy resolution at 6 and 60 keV was 11.0 and 4.5% fwhm respectively. The total background rejection efficiency for 60Co gamma ray induced events was 97 and 70% in the energy range 1–10 and 1–60 keV respectively. Finally design improvements which yield and energy resolution as low as 7.5%K at 6 keV are outlined.

The in-Orbit Performance of the Exosat Gas Scintillation Proportional Counter

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.

The gas scintillation proportional counter on Exosat

The inclusion of a gas scintillation proportional counter (GSPC) within the EXOSAT payload complement significantly improves the spectroscopic capability of the mission. This broad-band medium energy spectrometer used in conjunction with the large area proportioni counter array (ME) should provide additional spectroscopic details on strong X-ray sources at photon energies above ~ 2 keV. The novel type of detector has an energy resolution at least a factor of two better than the ME experiment over a similar bandwidth (2 – 40 keV).

A fluorescent gated gas scintillation proportional counter for high energy X-ray spectroscopy

Abstract Results are presented on a background rejection technique suitable for xenon gas filled detectors measuring X-rays above 35 keV. The technique involves the separate detection of both the xenon K shell fluorescent photon, emitted in most interactions involving the photoabsorption of high energy X-rays above 34.5 keV, and the residual event from the initial photoabsorption. This technique when applied to gas scintillation proportional counters filled with 1 atm xenon yields a background rejection efficiency of ∼97.3% and an energy resolution of ∼2.5% at 60 keV.

High pressure gas scintillation spectrometers for x-ray astronomy

Abstract A comparison of the performance of a gas scintillation counter operating at pressures above one atmosphere is presented. The factors which influence the background rejection efficiency are investigated in detail. In particular the response at higher X-ray energies has been found to improve significantly making this a useful spectrometer for higher energy X-ray astronomy.

Performance characteristics of a fluorescent gated gas scintillation proportional counter

Abstract Experimental results are presented on the background rejection capabilities of a K gated xenon gas scintillation proportional counter (GSPC) filled to a pressure of 3 bar. A total background rejection of between 99.3 and 99.8% can be achieved over the energy range 35–100 keV. Such results when coupled with an energy resolution of ∼ 2.7% at 60 keV make the K gated GSPC an attractive alternative to sodium iodide and germanium solid state detectors for application in high cosmic X-ray astronomy and other fields.

A Position Sensitive Gas Scintillation Proportional Counter for X-Ray Astronomy

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.

Preliminary Studies CF Gas Fillings in Gas Scintillation Proportional Counters

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.

Performance of a Flight Model Gas Scintillaticn Counter Spectrometer for X-Ray Astronomy

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.

A Fluorescent Gated Imaging Gas Scintillation Specftroeter for High Energy X-Ray Astronomy

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.