Design and test of a beam transformer as a chopper

This paper introduces a new type of chopper, which is similar to a beam transformer first discussed by R. Wideroe[1]. It is based on the fact that the RFQ has a rather small energy window. A pulsed beam transformer that provides 10% energy modulation to the beam in front of an RFQ can effectively chop the beam. It has fast rise- and fall-time and a short physical length. A prototype, which consists of a cavity and a high voltage pulsed power supply, has been constructed and tested. Two types of magnetic materials were tried for making the core of the cavity--the Finemet and the ferrite Philips 4M2. While the former gave good performance, the latter failed the test. Results from the bench measurements and a plan for beam tests are briefly described. For details the readers are referred to Ref. [2]