Hall C raster veto/flag generator

Due to the high intensity and small size of the continuous electron beam produced at Jefferson Lab,11The Southeastern Universities Research Association (SURA) operates the Thomas Jefferson National Accelerator Facility for the United States Department of Energy under contract DE-AC05-84ER40150. ust raster it over the target to keep the properties of the target stable during an experiment. Rastering the beam using sign-wave control signals to produce a Lissajous pattern, however, causes the beam to remain at the edges of the target longer than the center. In these regions, the local heating can be much higher than the central region generating considerable luminosity losses affecting the quality of the data. This circuit tracks the X and Y raster waveforms and sends out NIM and TTL VETO/FLAG pulses when X2+Y2 is greater than a user set threshold based on the percentage of the peak voltage on the Y input. The VETO/FLAG can be used to limit the acquisition/analysis of the data to a circular region in the center of the raster pattern. This circuit automatically compensates for changing frequency and voltage to maintain a constant percent trigger from 0.4 to 5 V peak to the peak of the raster waveform.