Prototype of bandwidth limiting neutron chopper

Abstract

Abstract A bandwidth limiting neutron chopper prototype for spallation-neutron facilities is introduced. The content includes the structure of the chopper, design specifications, neutron absorber construction and motor phase control. The investigation shows that the strength of Boron Carbide + Resin composite covered on an Aluminum alloy disk is high enough when the chopper rotor runs at a speed of 3000 rpm. A general purpose PM servo motor was equipped for the chopper. High accuracy phase tracking performance was achieved for the chopper based on a dual-loop motor control structure including a velocity loop and a phase loop. Torque disturbance was well restrained by the velocity control loop at a high sampling rate with help of a high resolution encoder in the motor. With the stable inner loop, the phase loop could work at a low sampling frequency equal to the rotation speed. Thus the rotor was synchronous with an inner reference pulse within less than 10 s. Related experimental results about the chopper are provided.