The design, construction, and performance of the CLAS Chrenkov threshold ga
s detector at Jefferson Lab is described. The detector consists of 216 opti
cal modules. Each module consists of the of three adjustable mirrors of lig
htweight composite construction. a Winston light collecting cone, a 5-in. p
hotomiltiplier tube, and specially designed magnetic shielding. Efficiencie
s and response functions have been measured. (C) 2001 Elsevier Science B.V.
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