MECHANISM OF SELF-QUENCHING STREAMER BY MEANS OF UV-LASER LIGHT

自猝灭流光（SQS）工作模式是气体计数管的一种基本工作模式，它与已建立的电离室工作模式、比例工作模式和GM工作模式一样重要。SQS模式指示非常高的气体倍增，并且进一步指示上级GM模式约一个数量级的非常好的计数率特性。本文用紫外激光研究了SQS模式的机理，其中光电离过程可能是重要的，结果如下：（1）在常用的Ar-isoC_4 H_2混合计数气体中加入二次淬灭气体如甲缩醛，改善了SQS管的计数率特性<10>。2）利用像增强器对α射线产生的流束进行光学观测，揭示了α射线产生SQS的机理。由于α射线电离径迹产生的电子产生两个流光，高电子密度的电离径迹加速了SQS跃迁。3）用紫外激光观察到SQS跃迁，电子雪崩的大小取决于激光功率，电离过程通过多次光吸收过程进行。因此，SQS跃迁与α射线等带电粒子的跃迁相似。4）Meta稳态激发的贡献不太清楚，因为紫外激光电离和光电离还有待确定。应该进一步研究。

The self-quenching streamer (SQS) mode of gas counter operation is a basically important operation mode as well as the established ionization-chamber, proportional, and GM modes. The SQS mode indicates a very high gas multiplication, and furthemore very good counting rate characteristics that are superior to the GM mode by about one order. In the present pfoject, the mechanism of the SQS mode, in which the photoionization process may be important, was investigated by means of UV-laser light.The results are summarized as follows :1) The counting rate characteristics of SQS tubes are improved by adding the second quenching gas vapor such as methylal to usually used counting gas mixture of Ar-isoC_4H_<10>. It encourages us to use SQS tubes in high radiation dose field near reactor sites.2) The mechanism of SQS produced by alpha-rays was revealed by optical observation of streamers with image intensifiers. Since two streamers are generated by electrons that come from ionization tracks by alpha-rays, high electron-density ionization-tracks accelerate the SQS transition.3) The SQS transition is observed by means of UV-laser light, Size of electron avalanches depends on the laser power and the ionization proceeds through the multiple photo-absorption process. The SQS transition is, therefore, similar to those by charged particles such as alpha-rays.4) The contribution from excitation of meta-stable states are not so clear, because the ionization by UV laser light and photoionization are to be identified. It should be studied furthemore.