When an
α
-particle moves in a magnetic field it describes a curved trajectory, the curvature of which is closely related to its charge and velocity. Thus the track of an
α
-particle obtained in a Wilson expansion chamber, placed in a magnetic field, will be no longer straight, but curved. From study of these curved tracks it should be possible to obtain information about the loss of energy and the change of the charge of a single atom moving through matter. The difficulty of this experiment is the necessity of using a strong magnetic field. The author has recently published a description of a method of producing strong magnetic fields for a small fraction of a second. The strength of these fields is of the order required for this kind of experiment, and the short period of time (0•01 sec.) during which the field is available is still very long compared with the time taken by the
α
-particle to describe its trajectory (1.0•10
-7
sec.). A preliminary account of this experiment has already been published, but it took about a year to complete the experimental results. In the present paper the description is given of the experimental arrangements used and of the results obtained.
α-ray tracks in a strong magnetic field
