The Development Of Signal Processing And Acquisition System For J-TEXT Thomson Scattering System

Thomson scattering diagnostic has been internationally recognized as one of the most powerful measuring means of plasma electron temperature.The measurement results of Thomson scattering diagnostic can be used to directly describe plasma transport and dynamics behavior,so that most of plasma physics research can be realized.The set-up of J-TEXT Thomson scattering system is in progress,and it can provide reliable plasma temperature and density for J-TEXT physical experiment after construction finished.As a key role of Thomson scattering system,signal processing and acquisition system is used to measure the scattered spectrum.We can obtain the plasma electron temperature and density by analyzing the scattered spectrum.This paper focus on two important links of signal processing circuit and data acquisition system,and the concrete content and achievement of the paper mainly manifests in the following aspects:(1)The photon number distribution of scattered light is given in the paper according to the design parameter of J-TEXT Thomson scattering diagnostic system.It provides an important basis for the analysis and processing of J-TEXT Thomson scattering signal.(2)The signal processing circuit for J-TEXT Thomson scattering diagnostic has been successfully developed.For effectively solving the problem of amplifying weak scattered light pulse signal in the plasma background noise environment,the rational topology design and the delay line technical are used in the circuit.The output pulse width of signal processing circuit is ~40ns,and its wave shape is symmetrical and not overshoot.With the use of temperature control circuit,the signal-to-noise ratio of signal processing circuit is up to 18.(3)An integral data acquisition system based on VME bus has been established for J-TEXT Thomson scattering diagnostic.The data acquisition system can meet the requirements of 14 measurements point and 50 Hz repetition frequency of J-TEXT Thomson scattering diagnostic.Moreover,the data acquisition system has high cost performance and there are enough acquisition channels to expand the system.The functional verification test for signal processing and acquisition system is provided in this paper,and the experimental results show that our design can satisfy construction requirements of J-TEXT Thomson scattering diagnostic,which is very important for the construction of the whole Thomson scattering system.