The CLAS12 beamline and its performance

Abstract This paper describes the Hall B beamline and its performance during the first year of data-taking operation using the CLAS12 detector. We review the beamline instrumentation used to measure and monitor the beam. This instrumentation led to excellent beam quality for energies ranging from 2.2 to 10.6 GeV at the design luminosity of 1 0 35  cm−2s−1. The instrumentation includes a Moller polarimeter, which can typically measure the beam polarization to an absolute precision of ∼ 2.5%.