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Description
The K800 ""CATANA"" Superconducting Cyclotron is currently undergoing the POTLNS upgrade project. This involves replacing its active components (Nb-Ti coils and vacuum chambers) while retaining the existing iron yoke, aiming to increase ion beam intensities by two orders of magnitude. To achieve the target performance within the strict dimensional constraints of the pre-existing yoke, four high-performance superconducting coils were manufactured under extremely tight assembly tolerances.
However, manufacturing deviations of the entire assembly prevented standard geometric installation from ensuring the required magnetic form factor. To overcome this, a novel assembly procedure was developed based on the actual magnetic field map rather than the as-built physical geometry of the coils.
Because the system is optimized for cryogenic operations, the primary challenge was the low field intensity obtainable during room-temperature (""warm"") alignment. To map this weak field, a dedicated field mapper was developed using a triaxial Hall probe integrated with a Hexagon T-Probe®. Optical targets on the coils ensured continuous referencing to the magnetic field. These measurements allowed the calculation of an absolute target position for the four coils, guaranteeing the correct alignment of the system's magnetic mid-plane with the physical extraction plane of the vacuum chamber.
Following assembly under laser tracker control, cooling, and energization, the alignment success was verified via cold magnetic measurements using a custom, low-cost, non-magnetic polar positioner tracked azimuthally by a laser tracker. A gimbal system eliminated one degree of freedom by aligning the system with gravity. This magnetic field-based alignment strategy proved highly effective, enabling precision levels unattainable through conventional geometric alignment methods.
