A system to measure the particle momentum of the very high intensity wide band electrons and positrons beam FNAL) has been realized. It consists of five large area silicon microstrip detectors, assembled in a symmetric two lever arm configuration, measuring the particle bend angles across the last pair of beam dipoles. Each silicon plane, 300-mu-m thickness, consists of 256 microstrips with 300-mu-m pitch and it is exposed to a rate of about 10(6) particles CM-2 S-1. Nowadays no other kind of detector could operate in such a high intensity beam with such a fine granularity requirement. The system is based on local data pipelining at the TEVATRON radiofrequency (53 MHz) and it is currently used in the heavy quarks photoproduction experiment E687 at FERMILAB, with a 2.2% resolution at 350 GeV. Technical construction details, performances of the system (efficiencies, momentum resolution and rate capabilities) are presented.
