EXPERIMENTAL PERFORMANCE OF AN E×B CHOPPER SYSTEM

Beam operation of an E×B chopper system has started in the Low-Energy Beam Transport (LEBT) section of the accelerator-driven neutron source FRANZ [1]. The chopper is designed for low-energy high-perveance beams and high repetitionrates. Itcombinesastaticmagneticdeflectionfield with a pulsed electric compensation field in a Wien filtertype E×Bconfiguration [2]. Helium ions with14keVenergy were successfully chopped at the required repetition rate of 257kHz. The maximum chopped beam intensity of 3.5mA, limited by the given test ion source, corresponds to a generalized perveance of 2.7· 10 =3 . For the design species and energy, 120keV protons, this is equivalent to a beam current of 174mA. Beam pulses with rise times of (120± 10)ns, flat top lengths of (85± 10)ns to (120± 10)ns and Full Width at Half Maximum (FWHM) between (295± 10)ns and (370± 10)ns were experimentally achieved.