Test and calibration of the Magnetic Measurement System for the Superconducting Cyclotron at LNS, Catania

The apparatus for magnetic measurements before commissioningof the Superconducting Cyclotron is presented.This is a fast system designed for the systematic mapping of cyclotron fields. A search coil measures the fieldvariation by scanning the median plane radially. The c.oilbearingbar ‘can then be turned over 360’ about the centralaxis to cover a full map. The absolute value of the field ismeasured by NMR probes placed at the cyclotron centreand at the RF cavities holes. The mechanical features ofthe system allow an accurate positioning and movementof the coil. The radial position is determined by an incrementalencoder with a step of 0.18 mm, the angularposition with an accuracy of 10W3 degrees and the medianplane is identified within 0.1 mm. The coil can move radiallywith a maximum speed of 50 cm/s. Accounting fordead times (coil return drift measurement) we make theconservative estimate of measuring one full map per hour,with an azimuthal step of lo. The overall accuracy on themeasured field is y E 10m4. A brief description of thesoftware used and probe calibration data are included.