The CLAS12 Spectrometer at Jefferson Laboratory




The CEBAF Large Acceptance Spectrometer for operation at 12 GeV beam energy (CLAS12) in Hall B atJefferson Laboratory is used to study electro-induced nuclear and hadronic reactions. This spectrometerprovides efficient detection of charged and neutral particles over a large fraction of the full solid angle.CLAS12 has been part of the energy-doubling project of Jefferson Lab’s Continuous Electron Beam AcceleratorFacility, funded by the United States Department of Energy. An international collaboration of 48 institutionscontributed to the design and construction of detector hardware, developed the software packages for thesimulation of complex event patterns, and commissioned the detector systems. CLAS12 is based on a dual-magnet system with a superconducting torus magnet that provides a largely azimuthal field distribution thatcovers the forward polar angle range up to 35◦, and a solenoid magnet and detector covering the polar anglesfrom 35◦to 125◦with full azimuthal coverage. Trajectory reconstruction in the forward direction using driftchambers and in the central direction using a vertex tracker results in momentum resolutions of<1% and<3%, respectively. Cherenkov counters, time-of-flight scintillators, and electromagnetic calorimeters providegood particle identification. Fast triggering and high data-acquisition rates allow operation at a luminosity of1035cm−2s−1. These capabilities are being used in a broad program to study the structure and interactions ofnucleons, nuclei, and mesons, using polarized and unpolarized electron beams and targets for beam energiesup to 11 GeV. This paper gives a general description of the design, construction, and performance of CLAS12.

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Copyright © 2020 Published by Elsevier B.V.

DOI: https://doi.org/10.1016/j.nima.2020.163419