Beam current monitor calibrator for the Spallation Neutron Source

The beam current monitor (BCM) system for the Spallation Neutron Source (SNS) to be installed at Oak Ridge National Laboratory (ORNL) requires an on-line calibrator to assure the system is appropriately scaling current. The calibration system must be able to handle the current range expected in the MEBT, Linac, HEBT, Ring and RTBT. This covers a dynamic range of 35ma to 50 amps. A 10-turn calibration winding has been included in all current transformers. This calibrator must provide adequate flexibility to assure the current transformers are not damaged by failures in the calibrator drive amplifier, and provide better than 1% accuracy with a capability to provide calibrated currents covering the dynamic range. This paper will address the design considerations and resulting design of a suitable calibrator for this system.