A charged particle moving at an angle to a magnetic field like that found at the ends of a solenoid (increasing field strength) would produce the desired motion

A charged particle moving at an angle to a magnetic field like that found at the ends of a solenoid (increasing field strength) would produce the desired motion. Example: https://s3-us-west-2.amazonaws.com/courses-images/wp-content/uploads/sites/1989/2017/06/13230250/figure-23-05-04a.jpeg https://s3-us-west-2.amazonaws.com/courses-images/wp-content...