3.3.1 The pion beta decay project detector
The design of the pion beta decay detector involves several components
illustrated in Figure 3.7. Many of these components were used in the 1996 and
1997 beam times at PSI. The detector, when completed, will cover nearly 80%
of 4 p sr as seen by the center of the target. For the summer of 1996, an
array of 40 CsI crystals covered ~ 13% of 4 p sr however, the presence of 4
"dummy" crystals (plastic pieces shaped like the crystals used for mechanical
support) reduced the usable area of this array significantly. By 1997, the
"dummy" crystals had been replaced by CsI crystals giving a coverage of >
14% of 4 p sr.