UBC Theses and Dissertations

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UBC Theses and Dissertations

The precise measurement of mass spectrometer ion currents Whittles, Arthur Brice LeRoy

Abstract

This thesis is primarily concerned with the problems involved in making precise mass spectrometer ion current measurements. A survey of the literature of the past decade shows that until the new type of system discussed in Chapter 3 was presented by R.D. Russell and F. Kollar, remarkably few developments were made in improving the precision of ion current measurements for the isotopes of the heavier elements. This situation is probably partly due to a failure to apply the modern methods of analysis which are presently used in the design of feedback control systems. Chapters 1 and 2 deal with the main requirements of ion current measuring systems. It has been assumed in previous systems that the resistor, through which the ion current is passed, has an approximately constant value for all values of the current. A method has been developed to measure the degree of this non-linearity, and results are given for the Victoreen Hi-Meg resistor. The theory necessary for the measurement is developed in detail. The final chapter deals with a general study of mass spectrometer measuring systems. A comparison is made of the two general types of measuring systems now in use, with an attempt to determine their relative advantages and disadvantages. The new system noted above is also discussed with the objectives of determining its theoretical performance, and of illustrating the methods of analysis. An appendix has been included to show the usefulness of the analogue computer in the design of an ion current measuring system.

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