Design of MARCO, the New Solenoidal Detector Magnet for the ePIC Experiment at BNL

Magnet with renewed coils (MARCO) is the new superconducting solenoid for electron-proton/ion collider (ePIC), the general-purpose detector capable of delivering the full scientific scope of the electron–ion collider at Brookhaven National Laboratory (BNL). This 3.84-m-long solenoid, with a bore diameter of 2.84 m, will provide a magnetic field of 2.0 T at the center with a nominal current of 4 kA at 4.5 K, for a total stored energy of 45 MJ. Its conductor is an NbTi Rutherford in copper channel, specially designed to stand the high mechanical loads induced by the magnetic field. Its copper stabilizer will assure the protection in case of quench. The coils are wound into six layers inside a thin external mandrel in brass, with a triple role of mechanical reinforcement, cryogenic support for the thermosiphon circuit, and quench-back propagator. With a cold mass average radial thickness of just 7 cm, the magnet fulfills all the criteria of transparency for the particles directed to the hadronic calorimeter forecast around the cryostat. In this article, the design of MARCO is presented with a specific focus on the magnetic and quench analysis.