[en] In studies of in-beam gamma ray spectroscopy for nucleides far from the beta-stability line, it is one of the most important things to know what nucleide emits gamma rays. In order to identify nucleide which emitting the gamma rays, we have proposed a new gamma ray measuring system which consists of an annular type high purity Ge detector, a beam separator, a device for identification of atomic number, and a TOF type mass spectrometer. In order to obtain the best mass resolving power in the TOF type mass spectrometer, characteristic of a Si(Au) detector as the measuring device of particle energy was investigated. For this purpose Si(Au) detectors which can generate strong internal static field were fablicated. The energy resolution for heavy ions of various kind were measured as functions of the detector bias voltage, and the response functions concerning channelling effect were also studied for various incident particles. Many interesting evidence were observed with respect to pulse height defect and radiation damage. From these experimental results, following things were concluded. 1. Strong electric field in the Si(Au) detector is the most important to measure heavy ions in high resolution from the view points of pulse height defect, radiation damage and charge collection. 2. It is found that large disturbance in response function for heavy ions is caused by channelling effect, and then it is concluded that the effect can be reduced completely by inclining 1⁰ incident angle against perpendicular direction of crystalline surface of the detector. (author)