The third candidate is thin gap chambers (TGCs), a kind of MWPC with a very thin gap ( mm). TGC is highly efficient except for the dead space due to wire supports. The signal is fast enough for our purpose. The position resolution of 1 cm is easily achieved, similar to the case of RPC. TGC can be operational at a very high particle rate of 1 kHz/cm2. The only demerit is the higher construction cost than that of RPC, as TGC uses a huge number of wires.
The endcap muon trigger system for the ATLAS experiment uses the TGC technology . To this purpose intensive R&D works were performed in Israel and Japan. Production of a total of 1,000 large TGC doublets/triplets are in progress at KEK. According to the ATLAS TGC schedule, the production will be completed in 2003, and then installed at the LHC experimental hall by the end of 2004. Through the TGC production we will at least gain an excellent experience to construct a large area muon detector system.