DEVELOPMENT OF CONVENTIONAL QUADRUPOLE MASS ANALYZER FOR RI TARGET ANALYSIS AND ITS PERFORMANCE

摘要

A Knudsen-cell-based quadrupole mass analyzer has been developed for the analysis of a small amount of RI sample. To achieve a high signaloise ratio, a continuous dynode electron multiplier was installed at the end of the mass filter and was operated in a pulse counting mode. Furthermore, the cylindrical shape molecular trap was set around the mass analyzer to reach high degree of vacuum and to reduce the RI contamination area in the apparatus. The isotope ratio of Cs-135/Cs-137 samples has been measured to demonstrate the performance of the mass analyzer. Taking the advantage of the Knudsen-cell's precise controllability over temperature, the contribution of the isobar Ba-137 was successfully removed in the mass spectrum of cesium. With samples containing about 0.3 mu g Cs-137 and almost the same amount of Cs-135, the isotope ratio measurement with the total error of 3% has been achieved. The molecular trap was also shown to be effective to reduce she contamination area in the apparatus. [References: 8]