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Abstract: The cathode amplifier is intended to amplify the positive current pulses from the cathode strips of proportional chambers and drive the 50Ω coaxial cable. The amplifier gain and the output voltage swing are matched for operation with the LeCroy 1882F ADC. The special feature of the anode electronics is the integration of the amplifying section, signal delay unit and digital section within one CAMAC module (ADD-32). The 1m-wide ADD-32 module contains the electronics for 32 wires, which makes it possible to place up to 672 data channels in a CAMAC crate with a standard bus. To amplify signals, 8-channel microcircuits Ampl8.3 are used. The output logic signals are delayed by 9-channel IDT72421 FIFO microcircuits, which enables to obtain a total signal delay of up to hundreds of microseconds and longer. The digital section of the system is based on ALTERA programmable logic arrays. This system with a total of 576-channels is used in the PIBETA experiment to study rare pion decays on the PSI accelerator (Switzerland). [Copyright &y& Elsevier]

We describe the design, construction and performance of the PIBETA detector built for the precise measurement of the branching ratio of pion beta decay, π+→π0e+νe, at the Paul Scherrer Institute. The central part of the detector is a 240-module spherical pure CsI calorimeter covering ∼3π sr solid angle. The calorimeter is supplemented with an active collimator/beam degrader system, an active segmented plastic target, a pair of low-mass cylindrical wire chambers and a 20-element cylindrical plastic scintillator hodoscope. The whole detector system is housed inside a temperature-controlled lead brick enclosure, which in turn is lined with cosmic muon plastic veto counters. Commissioning and calibration data were taken during two 3-month beam periods in 1999/2000 with π+ stopping rates between 1.3·103 π+/s and 1.3·106 π+/s. We examine the timing, energy and angular detector resolution for photons, positrons and protons in the energy range of 5–150 MeV, as well as the response of the detector to cosmic muons. We illustrate the detector signatures for the assorted rare pion and muon decays and their associated backgrounds. [Copyright &y& Elsevier]