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Title: Disintegrations of light elements
Author: Young, S. A.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1953
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This work is divided into three parts. Part A, discusses some of the focusing properties of magnetic fields used for the deflection and analysia of ion beams; part B describes the design and construction of magnets employing these theoretical principles; and Part C is an account of some experimental work done using focussed beams of deuterons. The work was all alone at the Clarendon Laboratory, between Michaelmas Term 1948 and Michaelmas Term 1953, and the three parts form a roughly chronological sequence. Part A: The Focusing Properties of Magnetic Analysers. The 1 M.V. and 500 KV. acaelerators of the Clarendon Laboratory provide relatively high current beams of positive ions which are very homogeneous in energy. For separating the ions of different masses a magnetic analyser is clearly necessary, since it can be shown that the alternative, an electrostatic analyser, gives energy dispersion only. The simple magnetic analyser which was customarily used until recently, being a sector shaped uniform field, has strong focussing properties in the plane containing the beam and perpendicular to the field lines (the "perpendicular" plane), but none in a plane containing the emergent beam and parallel to the field lines (the "parallel" plane). This focussing becomes stronger as the sector angle Φ is increased, until at 90°, which is frequently a convenient angle, an incident collimated beam of circular cross-section converges to a line focus at the exit boundary. This is a great inconvenience in mnny cases where care has been taken with the accelerator to provide an intense ion beam for nuclear bombardment studies. The properties of such uniform sector fields are discussed briefly, since they serve to demonstrate the formal analogy between ion trajectories in magnetic fields (ion optics) and light optics. The power of the lens in the two planes can be changed by using a field which in non-uniform, varying with radial distance as H α r-n. Such a field focusses in both planess but it is shown that coincident foci can only be obtained at image distances 3 + n; (b) D + D → H3 + p has been investigated in the energy range 150 KV. to 450 KV. (deuteron bombarding energy). Although other workers have made measurements of (a) in this region, the technique used was different, and the present work partly bridges the gap between the work of Eliot (0 to 50 KV.) and that of Blair (1 to 315 MV.), both of whom used similar methods. The apparatus consisted of a cylindrical target chamber filled with deuterium at a pressure of about 0.1 mm. Hg., and attached to the end of the accelerator column of a 500 KV Phillips generator. the beam was carefully collimated by a canal system, and the charged reaction products from a small volume at the centre of the target box were counted by ion counters operated in the proportional region. Two counters were arranged to swivel about an axis through the centre of the reaction volume, and a third, which was used to monitor conditions, was fixed to the lid of the box. The counter windows were of very thin (about 0.5 μ) quartz. The counter gas was heptane vapour at a pressure (about 1 cm.) determined by a fixed temperature bath. Counts were made of the number of He3 and H,sup>3 particles penetrating the counter window at various angles. These particles were distinguished by a careful choice of bias applied to a phase height disoriminato, and by the use of absorbing mica screens in front of the window. The principle is that the three charged particles from the reaction, as well as scattered deuterons, give in general different amounts of ionization in the counter materials and absorbers, because of their difference of energy and charge. The results to be expected are discussed in detail.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available