Controlling Magnets at Jefferson Laboratory

The Magnet Record

• Provides two dependent settable fields for controlling magnet’s effect– Magnet current (“S”)– Magnet field (“BDL”)

• Magnet hysteresis loop control– Magnet field map kept in each record

Magnet Hysteresis

Managing Hysteresis

• Beam reproducibility requires magnet reproducibility

• Keep Magnet On Loop (KMOL) mode forces magnets to stay on the curve

• High-level applications must work with alarm handlers and other tools

Setting a Magnet’s Strength

• “Engineering” control: current– Useful when no field map is available– When running through the hysteresis curve

• Optice control: field of the magnet– So applications can control magnets in an

energy-independent manner

• Magnet fudge factor

Magnet Alarms

• Difference alarm– Alerts operations to a mismatch on current

• Outside range alarm– Alerts operations to a current being clipped

• On-loop alarm– Alerts operations to a non-reproducible magnet