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Fast to Total Ratio

It is the first test to which all delivered modules are subjected. The bare module is air gap coupled to a PMT---EMI 9822QB. The cosmic rays traversing the crystal produce signals whose charges are integrated during the fast gate (100 ns) and the long (total) gate: 1000 ns. The ratio of the charge collected during the fast gate to that measured in the long gate gives the F/T of that particular crystal. The F/T is an important measurement of the quality of the CsI ingot from which the module was cut. The length of the fast gate is also the nominal length of the delayed pion gate (DPG) during which pion beta and events are registered. For good energy resolution in the calorimeter, the F/T for each module must be or better.

Bernward Krause
Mon Jan 15 14:57:06 MET 1996