Design Of VME-based Constant Fraction Timing Discriminator

The high-energy physics experiments need to determine a signal generation time, this work is mainly done by the timing discriminator. Each signal has its rising edge, timing discriminator generate a timing signal by detecting the rising edge. By analyzing the two timing signal by the TDC after the time-to-digital conversion between these two physical events can determine the time difference. By analyzing the energy of particles in the time information can be determined experiment, the spatial location, speed and other information. Therefore, the accuracy of the timing discriminator have a significant impact on the results of physical experiments.According to the needs of our school to build the drift chamber model, for the time swimming in the timing screening larger and NIM plug-screening currently used can not be included in the software system, based on VME bus constant fraction timing discriminator (CFD) program.The program is the analysis of the principle of timing and time swimming causes. Constant fraction timing technology by a constant percentage point at the rising edge of timing signal, can effectively reduce the time swimming because the signal rise change. Constant than the core of the timing, there are two, one is a quick comparison, and the second is the signal delay. In order to ensure the high performance of the discriminator, we have chosen the ultra-high-speed comparator for the ECL circuit technology. Reliability of the system to select the precision of the delay device. VME bus interface, CPLD interface logic control. The discriminator can operate independently of the eight channels, each channel parameters are available from the PC through the VME bus settings.This thesis describes the design and implementation of the VME bus-based constant fraction timing discriminator. Comparison the advantages and disadvantages of the cutting-edge timing, the zero-crossing timing and constant fraction timing discriminator. Then I introduction of the hardware circuit design of CFD and control circuit based on VME bus.