Combinations of deflection chopping systems for minimizing energy spreads

Abstract

Pulsed MeV ion beam techniques are broadly applied in time-of-flight experiments for direct measurements of neutron velocities and energies. They are also used to achieve a neutron monochromater by allowing the selection of neutrons having a well defined velocity. The sequence of components needed for creation of sub-nanosecond pulsed MeV ion beam systems usually consist of a suitable DC ion source, a chopper module for production of beam pulses, a klystron buncher for introducing time compression to individual pulses and a final ion-acceleration stage. It is pointed out that the achievable pulse compression is limited by the energy spread within the pulses that are directed into the klystron buncher. Furthermore, that this energy spread may be dominated by the energy spread created within the preceding chopper system. The present invention minimizes this problem of chopper introduced energy spreads and discloses a chopping system that comprises at least two electrostatic deflectors with phase-locked radiofrequency voltages. With proper amplitude and phase control chopper assemblies are described that do not add significant energy spreads to the beam.