The Research And Test Of Multi-Wire Drift Chamber System

High Energy Nuclear Physics is one the major areas in today's nuclear physics research,including equation of state of nuclear matter,studying of symmetry energy of nuclear matter,QCD phase transition and so on.The research of high energy nuclear physics needs large equipment such as ion accelerator and modern particle spectrometer system.One of the important sub-system in the modern particle spectrometer is the tracking detector system which can do PID by measuring the track of particles emitted in the nuclear reaction and reconstructing the momentum of particles.Considering the existence of HIRFL-CSR,a large universal particle spectrometer system is proposed to be built at the external target experiment terminal,which offers the opportunity of research of high energy nuclear physics in China.The Multi-Wire Drift Chamber(MWDC)is selected as the forward track detector of the spectrometer system.The MWDC array system consists of several parts: the drift chamber,the TOF detector(plastic scintillator),front end electronics,Flash-ADC digitizer Data Acquisition system,digital waveform processing package,track finding and track reconstruction packages,chamber alignment package and so on.The drift chamber has a planar structure which manufactured with epoxy plate and aluminum alloy plate.Wires are stretched using the automatic stretching machine.TOF detector offers the trigger signal of the system at the same time measures the time of flight of the incident particles.TOF detector is made of two plastic scintillators.The light generated in each scintillator is transmitted through the light guide and collected by the PMTs mounted at the terminals of the scintillators.The front end electronics of the drift chamber is voltage sensitive pre-amplifier designed with discrete devices,including common-base amplifier,emitter follower,pole-zero cancellation,power output and so on.The Data Acquisition system is based on the Flash-ADC digitizer modules,with which the waveform of every channel of detector is stored for later analysis.A set of digital waveform processing algorithm is developed according to the signature of the detector signal for increasing the Signal-Noise Ratio and the energy resolution.The digital Constant Fraction Timing method is used to deduce the time information of the signals.For track finding and reconstruction of 2D and 3D,a set of algorithm is developed with an analytical fitting package which can do tracking with high efficiency and less computing time.After the integration of the detector system,it is tested with the beam at IHEP.The test results show that the drift chamber array has a time resolution of 600 ps,space resolution of 368 ?m and energy resolution of 22.5%.For a better resolution it is necessary to further improve the system.