STUDY OF A HIGH RESOLUTION GERMANIUM ION CHAMBER FOR DOUBLE beta DECAYS

为了研究双β衰变，我们研究了建立一个高分辨（能量）四甲基锗（TMG）温液电离室的可能性。TMG含有7.6%的^ Ge双β衰变源<76>。因此，如果建造一个充满TMG的高分辨电离室，它将是一个很好的无中微子双β衰变探测器。为此，我们首先建立了TMG的净化系统和两平行板电离室，并成功地观测到了976 KeV的^ Bi转换电子信号<207>。然后，我们制作了一个在阴极和阳极之间带有栅格的新腔室，并比较了（1）不使用栅格和（2）使用栅格的能量分辨率。结果是：对于电子寿命为4 μ sec的液体，σ/E-对于（1）为19%，对于（2）为17%，表明能量分辨率有所改善。然而，对于具有较长寿命的液体，可以预期能量分辨率的进一步改善。

For the purpose of studying double beta decays, we have investigated possibility of constructing a high resolution (energy) warm liquid ionization chamber which contains Tetramethyl germanium (TMG). TMG contains 7.6% of possible double beta decay source of ^<76>Ge. Thus, if the high resolution ionization chamber filled with TMG is constructed, then the chamber will be a good detector for observing the neutrinoless double beta decays. However, high resolution in energy is essential for the observation.For this purpose, we first constructed a purification system for TMG and an ionization chamber with two parallel plates and succeeded in observing a signal from 976KeV conversion electrons from ^<207>Bi. Then, we made a new chamber with a grid between the cathode and the anode and compared the energy resolutions for (1) without using the grid and (2) with using the grid. The results were : sigma/E-19% for (1) and 17% for (2) for the liquid with electron lifetime of 4musec, indicating some improvement in the energy resolution. However, the further improvement in the energy resolution can be expected for the liquid with a longer lifetime.