Reducing the Effects of Electrical Interference on Nuclear Instruments

An account is given of a research programme that has been going on for some years to study the mechanism by which electrical interference disturbs the correct operation of nucleonic instruments, particularly the wide-bandwidth equipment used with pulse counting types of measurement. One of the principal results of this work is the realization that most sources of interference cause currents to flow through the screening of the measuring installation and that it is this flow of current that causes signals to be generated that interfere with the measurement. Information is given on the characteristics of a variety of coaxial cables from this point of view, indicating which types are to be preferred. A discussion is also given of the influence of these factors on the mechanical design of electronic boxes. Techniques have been developed that, with the establishment of the relevant criteria, allow installations to be measured for their degree of susceptibility to electrical interference. Also the results of these measurements can be used to decide where to make changes to the installation to effect improvements. A large ''library'' of remedial measures is available and a few examples are given. (author)