A Data Acquisition System For The Small Cell MDC Prototype Test Of BES3

A data acquisition (collection) system, which is used to test the small cell MDC (Main Drift Chamber) prototype of BES3, is introduced in this paper.The first chapter of the paper introduces the correlative background, and brings forward the necessity of building up this system. The second chapter lists the hardware system of the data acquisition and the electronic devices which compose this system, and briefly introduces the working course. The prime contents of the third chapter is the software system, including the hardware driver, the standard functions of CAMAC ( Cumputer Automated Measurement And Control) , and the GUI (graphics user interface), which ensures the system work well. The fourth chapter introduces the course of debugging this system, which mainly resolves the problems that come with this course, so that the system can work well. Then the detailed result lists at the end of this chapter. The conclusion part summarizes the contents of this paper and emphasizes the innovation of the work. Some advice also has been listed for the later work.The hardware in this system includes computer, CCU (crate control unit), some electronic units which measure the Q and T. The computer is common PC and it connects to the CCU through the ISA card, which is designed by us. The other electronic units include preamplifier, main amplifier, TDC (Time-to-Digital Converter), ADC (Analog-to-Digital Converter) , SC (Scintillation Counter), CFD (constant fraction discriminator), coincidence logic units, timing units, fan-out, input register, output register and ISA card. The unit connects eath other through coaxial cable whose characteristic impedance is 50 ohm.The operation system of the computer is Linux, Red Hat 7.2, under which C language is used to develop the hardware device, ISA interface card, driver, and consequently standard CAMAC function and GUI are written. All of these made the whole system work in the demand of the user's design and finish the data acquisition.When the system was regulated initially. The disaccording delay had changed by prolonging the cable to 25 meters in each channel. Accuracy hadbeen adjusted through changing the former edge and rear edge of the gate signal from the timing unit, and by the vernier knobs in the panel of ADC and TDC. The noise had been reduced to negligible by enforcing the signal's grounding and wrapping some metal shield on certain cable.After the system was adjusted, we measured the performance of the system by calibration, and the result was satisfying and could meet the demand of the prototype experimentation. Then we tested the performance of the prototype using this data acquisition system, with the cosmic rays as the particle resource. Detail conclusion listed in the paper, which indicates the data acquisition works well.