Streamers in MSGC's and other gaseous detectors

In this paper we describe the formation and propagation of streamers under different conditions and in different gas mixtures. We discuss how streamers may limit the operational capabilities of various gaseous detectors. 1 . Introduction Wire chambers, proposed by G. Charpak et al. [1], revolutionized detector development. They are widely used now in many experiments and have made possible many important discoveries in High Energy Physics. A further significant step was made by A. Oed et al. [2], who suggested replacing the wires by strips on a dielectric substrate. This detector, the MSGC, has many technological advantages. However, it suffers from one main disadvantage: at gains of about 104 sparking appears and this is a serious limitation in many applications. Recent studies have shown that the gain is limited by the appearance of streamers [3] and that these streamers have a very narrow self-quenched region (in voltage) and then transit rapidly to sparks. Do streamers affect the rate characteristics of MSGC's and other gaseous detectors and can breakdown in MSGC's be prevented? In this paper we will try to answer these questions. 2 . What is known about streamers