Passivation of micro-strip gas chambers with an interstitial germanium coating

Micro-strip gas chambers (MSGCs) were constructed in the Solid-State Electronics Laboratory of the University of Michigan and their performance was studied. Many efforts have been made in the past to construct MSGCs that yield high absolute gas gain and stable gas gain. Introducing a thin germanium layer has been effective for passivation but difficulties associated with the poor adhesiveness of the thin layer have been a serious obstacle. This paper reports on a new method used to overcome these difficulties. Unlike the conventional coating method the thin germanium layer was successfully deposited between the strip lines. This technique requires a careful geometric alignment of a second photomask with the original micro-strip structure. The resulting detector performance was noteworthy and an absolute gas gain of 2 · 104 was easily achieved by the new chamber. The chamber's gain instability was also reduced significantly compared with those without interstitial coating