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The CHESS G-line wiggler has been tuned using a conventional magnetic measurement method together with a novel vibrating wire technique. While the conventional method, based on magnetic field measurement with a long flip coil, provides magnetic field characteristics integrated over the wiggler length, the vibrating wire technique gives the location of magnetic field errors along the wiggler length allowing the correction of field errors in the location where they occurred. The paper gives parameters of the CHESS G-line wiggler, describes the magnetic measurement setup, discusses some aspects of the vibrating wire technique applied to wiggler tuning, and reports on results of the CHESS G-line wiggler tune up.

Machine performance for the running period is reviewed with an emphasis on phenomena associated with the large number of parasitic crossings peculiar to a single ring collider with multi-bunch beams.

A vibrating wire technique has been used for the precise positioning of the CESR Phase III quadrupole magnets into cryostats at room temperature. The alignment was performed in a 8 /spl times/ 10/sup -2/ T/m quadrupole magnetic field gradient. The position of the quadrupole magnetic center was measured to 0.03 mm precision. The magnets were aligned with a cryostat centerline with better than 0.2 mm precision. The measurement setup, instruments and the procedure are described.

The longitudinal multi-bunch beam instability significantly complicates Cornell Electron Storage Ring (CESR) operation. The observed dependence of the horizontal separator temperature on the space between two bunches circulating in the same direction suggested the presence of long lasting parasitic modes in the separators. The S-parameter measurement confirmed the existence of the modes and gave their frequencies and quality factors (Qs). The program URMEL was used to calculate the modes coupled to the beam, i.e. parameters R/Q. Using these characteristics the longitudinal instability growth rate and instability threshold current were computed. The calculated threshold is only 35% higher than observed. The conclusion has been made that the parasitic modes in horizontal separators are among the major factors causing longitudinal multibunch beam instability at the CESR. The multibunch beam stability at the CESR will be significantly improved if these modes are damped.