Ageing problems of the Inner Tracker of HERA-B: An example for new detectors and new effects

Large-size MSGCs and GEM-MSGCs were developed for HERA-B. In the course of R&D many ageing and operation problems have been found, several have been solved but some necessitated 'bad' compromises in order to obtain a working detector technology. Eventually, the satisfactory operation of 130 GEM-MSGCs in HERA-B proved the development to be successful. Many of the found problems do apply as well to other modern micro pattern gaseous detectors and recommendations for future R&D are derived.