The Design and Operation of a Double Magnetic Lens Beta-Ray Spectrometer

Details are given of the design of a double magnetic lens spectrometer. Both coils of this spectrometer are capable of very fine adjustment in five degrees of freedom. Extensive work has been carried out on the testing of this instrument. This has included a study of the variation of spherical aberration with coil separation, the use of a quick and accurate experimental method of plotting trajectories, and an investigation of the extremely critical nature of coil alignment. Experimental confirmation of the predictions of Deutsch and his co-workers has also been obtained, and ring focus has been incorporated with notable success. This spectrometer has a much lower spherical aberration than a short lens and gives a performance comparing not unfavourably with long lens types.