C. G. Rapley
New techniques and observations in Soft X-ray astronomy
1976 (supervisor: J. L. Culhane)

Progress in soft X-ray astronomy has been hampered by difficulties encountered in the design of reliable instrumentation. The work described in this thesis is addressed to improving conventional instrument performance, to obtaining new astronomical data concerning the Soft X-ray Diffuse Background and to deveolping new instrumentation capable of providing high energy resolution at soft X-ray energies.

In part I, following a review of thin window proportional counter techniques, some laboratory development work is described. This includes the design of a charge sensitive preamplifier suitable for use with soft X-ray systems, the manufacture and calibration of proportional counter thin windows, the discovery of a new and very durable thin window material and the discovery of a detector internal coating which significantly reduces detector ultraviolet sensitivity.

The use of a conventional thin window proportional counter to study the spatial structure of the Soft X-ray Diffuse Background is described in Part II. The experiment, launched on Skylark 1203, detected X-ray emission from the radio continuum features Loops I and IV and revealed a prominent absorption feature coincident with a dense neutral hydrogen filamentary structure, the Hydra ridge. An analysis of these data indicates the presence of gas at a temperature of ~7.10^5 K lying beyond the bulk of the absorbing material within the galactic disk. It is argued that much of the observed emission both from within and beyond the galactic disk may result from the interaction of the Sco-Cen association with the local interstellar medium.

Part III is concerned with the laboratory testing of a one-dimensional position sensitive proportional counter and its use in a novel form of crystal spectrometer capable of providing simultaneous high energy resolution over a range of soft X-ray energies. Descriptions are given of two successful souding rocket flights of an instrument used to study solar active regions.