EPECUR setup for the search for narrow baryon resonances in pion-proton scattering

The EPECUR experimental setup has been designed to search for narrow resonant states by precisely measuring differential and total reaction cross sections for pion-nucleon interactions with 1-MeV pion energy steps. Over the 5 years that passed from the submission of the idea of the experiment to the start of data taking in April 2009, a non-magnetic spectrometer with a liquid hydrogen target based on the large-aperture multiwire drift chambers with a hexagonal structure has been built at the universal beamline 322 of the U-10 proton synchrotron at the Alikhanov Institute for Theoretical and Experimental Physics. Owing to the unique properties of the beamline, the beam particle momentum can be measured with an accuracy of 0.1% or better using 1-mm-pitch proportional chambers located at the first focus of the beamline. The design of numerous subsystems of the setup is based on modern electronic components including microprocessors and field programmable gate arrays. All the subsystems have been tuned and tested both individually and as parts of the whole setup. The distributed data acquisition system is based on the widely spread USB and Ethernet protocols, which help achieve high performance characteristics and take full advantage of the industrial solutions.