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HK: Hadronen und Kerne

HK 47: Detektoren III

HK 47.10: Talk

Wednesday, March 26, 1997, 16:30–16:45, HS K

An analogue trigger-processor for the A4 experiment at MAMI — •Simon K"obis¹ and A 4² — ¹Institut f"ur Kernphysik,Mainz — ²

The measurement of the parity violating asymmetry of the cross section of elastically scattered polarized electrons on unpolarized protons gives access to the strange quark contribution of the form factors of the nucleon.Such an experiment is currently set up at the MAinzer MIkrotron (MAMI) facility in Mainz(collaboration A4) with an electron beam energy of 855 MeV. A total uncertainty of 5% of the expected asymmetry of about 8 × 10⁻⁶ is projected. A large solid angle (0.7 sr) crystal calorimeter consisting of 1044 PbF₂ crystals will be built. The total eventrate expected is about 100 MHz in the whole detector. This requires fast cluster recognition, spatial and temporal pile-up rejection and fast data storage.In order to meet such extreme requirements a parallel trigger processor with an analog signal processing stage and a storage module are being developed. Each detector is provided with such a processor and storage module. A report on the recent results of a prototype-module for the quasi analog-trigger-processor which already achieved an aquisition rate of 2 MHz/channel is given.