Superconducting Magnet Power Supply and Hard-Wired Quench Protection at Jefferson Lab for 12 GeV Upgrade

The superconducting magnet system in Hall B being designed and built as part of the Jefferson Lab 12 GeV upgrade requires powering two conduction cooled superconducting magnets-a torus and a solenoid. The torus magnet is designed to operate at 3770 A and the solenoid at 2416 A. Failure modes and effects analysis determined that voltage level thresholds and dump switch operation for magnet protection should be tested and analyzed before incorporating into the system. The designs of the quench protection and voltage tap subsystems were driven by the requirement to use a primary hard-wired quench detection subsystem together with a secondary programmable logic controller (PLC)-based protection. Parallel path voltage taps feed both the primary and the secondary quench protection subsystems. The PLC-based secondary protection is deployed as a backup for the hard-wired quench detection subsystem and also acts directly on the dump switch. We describe a series of tests and modifications carried out on the magnet power supply and the quench protection system to ensure that the superconducting magnet is protected against all fault scenarios.