Picosecond Beam Monitors and Data-Acquisition System

The 30-A, 50-ps electron pulse generated by the EG&G/AEC linear accelerator permits the measurement of scintillator response functions and the study of other subnanosecond phenomena. To take advantage of this capability, a system for fast pulse monitoring has been developed. Faraday cups and nonintercepting monitors have been designed to measure the electron beam current, and are used in conjunction with a unique data-acquisition system for fast pulse measurements. This system uses the fastest available sampling oscilloscopes, modified for remote operation of the sampling elements, thus eliminating the signal distortion of the coaxial cable between the experimental measurement point and the data-recording area. The digitized output of the sampling oscilloscope is stored in a magnetic memory and repeatedly averaged to increase the signal-to-noise ratio, allowing the measurement of signals that are approximately 100 ps in duration and a few millivolts in amplitude. The digital information, recorded on either magnetic or paper tape, is compatible with computerized data-reduction techniques. This data-acquisition system may be used on any recurring fast pulse and offers a sensitivity-bandwidth improvement of about 105 over the best traveling-wave oscilloscopes.