| The work of the thesis consists of two parts, one is the design of a new multifunctional well logging instrument, and the other is some basic research on associated particle C/O (Carbon Oxygen ratio) well logging method.Firstly this thesis introduces the design of the data processing circuit. The instrument has two working modes: PNC, and C/O. Its data processing circuit will perform the following functions: the nonlinearity adjustment of the energy data; the recording of pulse reaching time; the classification of time data and energy data; the forming of time spectrum and energy spectrum; the control of the data acquiring and processing. According to these functions, the circuit has three modules: controlling module, spectrum forming module, and energy data adjusting, time data recording and data classification module. These modules, integrated in the CPLDs (Complex Programmable Logic Device), are developed on the platform of ALTERA's MAX+PLUS II, using VHDL (Very High Speed Integrated Circuit Hardware Description Language).For the practical application of the associated particle C/O well logging method, a series of simulations were also done using the Monte Carlo N-Particle Transport Code MCNP 4C. My research concentrated on the relations between the position of the most gamma ray and the angle of neutron emitting, and the relations between the parameters of the shielding object and the counts of gamma ray. From the research results, we know that the position and the angle have a relation of nearly tangent. We also find that the length of the shielding object should be 10~11cm, as it can screen most of the background gamma ray with this length. And the radius should be as big as possible. The shielding object should be designed to be a cylinder plus a cone, and the material should be tungsten. The shielding object with these designing can be more effective, saving some space and material.
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