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

The apparatus for magnetic measurements before commissioning of the Superconducting Cyclotron is presented. This is a fast system designed for the systematic map ping of cyclotron fields. A search coil measures the field variation by scanning the median plane radially. The c.oilbearing bar ‘can then be turned over 360’ about the central axis to cover a full map. The absolute value of the field is measured by NMR probes placed at the cyclotron centre and at the RF cavities holes. The mechanical features of the system allow an accurate positioning and movement of the coil. The radial position is determined by an incremental encoder with a step of 0.18 mm, the angular position with an accuracy of 10W3 degrees and the median plane is identified within 0.1 mm. The coil can move radially with a maximum speed of 50 cm/s. Accounting for dead times (coil return drift measurement) we make the conservative estimate of measuring one full map per hour, with an azimuthal step of lo. The overall accuracy on the measured field is y E 10m4. A brief description of the software used and probe calibration data are included.