Referencing the magnetic axis for HERA's superconducting magnets

For the alignment of the superconducting magnets of HERA the survey datums have to be referenced to the magnetic axis and the direction of the magnetic field. For the alignment of the superconducting magnets of HERA /1/ each magnet can be equipped with two survey platforms. They are attached to the side of the magnets. Reference points for these platforms are screws, which are prealigned by the manufacturer. Three radial screws define a plane, which gives the position of the survey point with respect to the geometrical axis and the role and yaw of the survey platform. Two vertical screws, on which the platform rests upon, provide the fixed-points for the height and the pitch of the survey platform. The azimuthal orientation is achieved by two horizontal screws, which locate a finger of the platform