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3γ decay measurements

3γ coincidences spectrometer
One can determine the rate of 3γ decays by counting the triple coincidences in 3 coplanar counters inserted into the channels in a lead block with the sample chamber in the centre. When angular spacings between all counters are 120, the energies of registered quanta from 3γ decay are 341 keV and the energy windows of single channel analysers are placed around that value. The counting rate in porous materials at our detector sizes (NaI(Tl) Φ40x40 mm), source activity (20 µCi) and geometry, reaches 3 coincidences per second. That allows to collect good statistics in a reasonable time.
AMPL - amplifier,
SCA - single channel analyser,
CFT - constant fraction discriminator,
DEL - delay,
FAST CC - fast coincidence (~ns),
SLOW CC - coincidence,
SC - counter.