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dc.contributor.authorLindsay, Norman Mathesonen
dc.date.accessioned2018-09-13T16:03:55Z
dc.date.available2018-09-13T16:03:55Z
dc.date.issued1969
dc.identifier.urihttp://hdl.handle.net/1842/32528
dc.description.abstracten
dc.description.abstractThe EBM will realise its full potential when a highly automated system capable of reliably machining sub -micron detail is developed. A study has been made of the several parts of the EBM, using an experimental system to test some probable answers to this design problem.en
dc.description.abstractThe use of a field emitter gun in the experimental system is an exceptional departure from orthodox design. It is only recently that field emitters have been accepted as having practical engineering applications. This is due to the development of modern UHV systems as well as research into new field emitter materials. With crystal oriented emitters, a new approach to design of the electron- optics can be made. The high brightness allows the use of very small apertures, where diffraction is the limiting aberration rather than spherical aberration, and this factor has boosted the application of field emitters to practical systems.en
dc.description.abstractRecent work by Windsor suggests that crystal oriented lanthanum hexaboride (LaB₆) will eventually replace tungsten as the emitter material. LaB₆ is a hard refractory material, resistant to ion bombardment. It requires lower applied voltage to induce emission, since it has a very low surface work function of 2.7eV. Thus the energy of bombarding ions is lower and this can result in a lower rate of tip erosion. However the material is difficult to machine and requires special etching techniques.en
dc.description.abstractAn experimental method which allows field emitters to operate at conventional vacuums has been described in chapter 3. This opens the way to "Flow grade" performance of field emitters, which nevertheless may prove superior to conventional cathode performance, and at the same time is competitive in cost and simplicity. The behaviour of flow grader field emitters should be studied in detail in a system with close control of the pressure and residual gas composition, and preferably with a scanning electron micro - scope facility in the same vacuum chamber to monitor detail of the tip geometry.en
dc.description.abstractTo limit the cost and simplify experimental procedure, the UHV system has remained of simple design, using only five or six basic components. Some idea as to what should be the final form for an operational EBM have been worked out. A differential pumping system between gun and work chamber would allow the chamber to be cycled from 10⁻⁶Torr to atmosphere, while keeping the gun under constant UHV. In a high vacuum system at room temperature, a pressure difference factor of 10³ across an aperture of 0.1mm. results in a leakage of only 1 litre /second into the lower pressure side. This leakage can be pumped away by a small 10 litre/second ion pump, and the aperture may serve a dual purpose by creating the pressure difference and also forming the defining aperture for the electron beam. In addition, a straight through plate valve should be included to isolate the work chamber when cycling down to atmosphere.en
dc.description.abstractThe option of making the column in pyrex or ceramic has been mentioned in section 5.3. This would greatly increase the bandwidth of the deflection and focussing coils, if these were wound outside the column. An extra benefit is the possibility of using RF heating to outgass the metal electrodes inside the column, using an external induction coil.en
dc.description.abstractA great deal of effort was put to designing the electronic instrumentation. This is of course an integral part of the EBM system and should be "tailor made" for the application. The D-to-A generator forms the central part of the computer- to -EBM interface, while facilities for computer control were also built into the high voltage current source. In the near future, a master voltage reference source with ultra low drift will be installed, and will control all the power supplies for the deflection generator, lens supply, high voltage source, and any additional instrumentation used in the EBM system.en
dc.description.abstractThese developments will eventually lead to a highly controlled precision machine, with an important contribution in the realm of micro -miniature, high reliability devices.en
dc.publisherThe University of Edinburghen
dc.relation.ispartofAnnexe Thesis Digitisation Project 2018 Block 20en
dc.relation.isreferencedbyen
dc.titleDesign of a high resolution electron beam machinesen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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