Up: A PRECISE MEASUREMENT OF
The detector stand supporting 240 CsI crystals was
designed at PSI during 1993 (Figure 2). The stand will be enclosed in a cosmic
muon veto house in the final setup. The first 25 CsI crystals have been
delivered and tested. Several tests were performed in a four week beam period
in the E1 area in the summer of 1993. The analysis of the data from this
run gave following results:
- A prototype of the active fiber target was tested
successfully. A high sensitivity and low cross talk between individual fibers
() were measured. Although only 35 of 140 fibers were equipped with
photomultipliers, the whole pion stopping distribution was measured by moving
the target perpendicular to the beam direction in separate measurements.
Analysis showed that 90 % of the stopped pions are contained in a spot of 20
mm diameter. This led to a redesign of the target with a reduced number of
fibers of 33 mm cross section each, covering an area of 27 mm
- Uniformity of the light output from several crystals was tested by
placing them in a 350 MeV beam with their main body axis
perpendicular to the beam. By optimizing surface treatment and cover of the
front face of the crystals, a uniformity of was achieved (Figure 3).
- A 12-crystal section of the CsI calorimeter was assembled and placed in
a 70 MeV e beam. The measured energy resolution of about 5 % FWHM agrees
well with a Monte Carlo calculation (Figure 4).
Mon Dec 4 11:53:12 MET 1995