A Precise Individual Superconductive Undulator Pole Measurement System

Modern synchrotron radiation facilities have extremely low electron beam emittance, what allows to generate SR with narrow harmonics using superconductive undulators. Therefore, serious requirements are imposed on the magnetic field structure of the undulators - it's necessary to provide as low as possible phase error value which depends on the deviation of magnetic field amplitudes of every single pole. An attractive way to reduce a phase error is to find out characteristics of each pole of the undulator precisely and then install them in a certain order while assembling the undulator. A device for individual pole magnetic measurements for their further sorting is described. Magnetic measurements requirements are formed. A measurement error of 0.2 % was achieved, however long-term repeatability is much worse, about 1.5 % - the data floats away monotonously for unknown reasons, likely connected with constructive design features of the system. Further works would be aimed at improving the long-term stability as well as reducing the measurement error caused by electrical part of the measurement system.