空气中以雪崩模式工作的阻性气体电子倍增器

It is well known that conventional gas detectors are unstable when it's working in the air with avalanche mode because of the photo feedback. The novel micro pattern gas detectors, like RETGEM, MICROMEGAS and so on, are strongly suppressed photo feedback, due to the avalanche confinement in a small space. Thus allow them working in the air in the stable. Our proposal is performing a RETGEM in the air with the avalanche mode. First, we increase the field in the conversion gap to keep the attachment coefficient low and in constant. Second, based on our earlier work, we will optimize the geometry of the RETGEM and choose the resistive layer to increase the effective gain. Besides, decrease the induction gap to about 100μm and strengthen the field to get electrons to avalanches in the small gap, just like a MICROMEGAS. Thus detector is working in the RETGEM+MICROMEGAS two step avalanche modes to get higher effective gain and more stable. This compensates the loss of primary ionized electrons and increases signal-to-noise ratio. Third, we will explore the working conditions with different temperature and humidity in the air. The significance of this proposal is developing simple and practical detectors for neutron detection and heavy ion therapy beam monitor.

在雪崩放大模式下工作的传统气体探测器由于光子反馈而在空气中不能稳定工作。新型的微结构探测器，如RETGEM、MICROMEGAS等，由于雪崩发生在很小的空间内，因而在很大程度上抑制了光子反馈，使其能够在空气中稳定工作。本项目是研制在空气中以雪崩放大模式工作的RETGEM探测器。首先，通过提高转化区的电场强度使得电子和离子的复合系数达到一个较小的值；其次，在已有的研究基础上优化探测器的结构和表面电阻来提高增益。通过减小RETGEM探测器的感应区到约100微米左右，提高电场强度使电子在感应区中继续发生雪崩放大，使探测器工作在RETGEM+MICROMEGAS两级放大的状态，进一步提高探测器的增益和稳定性。从而弥补原初电离电子的损失，提高了信号噪声比。第三，在不同湿度和温度条件下研究该探测器的工作状态。本项目的意义在于发展应用于中子探测和重离子治疗装置上束流监测的简单实用型探测器。

雪崩放大模式工作的核辐射气体探测器在空气中工作不稳定。微结构的气体探测器能够在很大成都上限制长射程的电子和光子，具有在空气中以雪崩放大模式工作的可能性。本项目主要研制的双层结构的THGEM探测器在空气中测试得到对239Pu α源的相对增益达到20，探测效率达到85.7%。完成了项目预计目标。