• M.J. Syphers, D.J. Harding
  Fermilab, Batavia, Illinois

During the 20 years since it was first commissioned, the Fermilab Tevatron has developed strong coupling between the two transverse degrees of freedom. A circuit of skew quadrupole magnets is used to correct for coupling and, though capable, its required strength has increased since 1983 by more than an order of magnitude. In more recent years changes to the Tevatron for colliding beams operation have altered the skew quadrupole corrector distribution and strong local coupling become evident, often encumbering routine operation during the present physics run. Detailed magnet measurements were performed on each individual magnet during construction, and in early 2003 it was realized that measurements could be performed on the magnets in situ which could determine coil movements within the iron yoke since the early 1980's. It was discovered that the superconducting coils had become vertically displaced relative to their yokes since their construction. The ensuing systematic skew quadrupole field introduced by this displacement accounts for the required corrector settings and observed beam behavior. An historical account of the events leading to this discovery and progress toward its remedy are presented.

• M.J. Syphers, G. Annala, D.A. Edwards, N.M. Gelfand, J.A. Johnstone, M.A. Martens, T. Sen
  Fermilab, Batavia, Illinois

During the beginning of Run II of the Tevatron Collider it became apparent that a large skew quadrupole source, or sources, had developed in the superconducting synchrotron. Efforts to locate the current source of coupling were undertaken, with the eventual discovery that the main magnets had developed a systematic skew quadrupole moment over their lifetime. Over the past year, the magnets have been altered in place in an attempt to restore the systematic skew quadrupole moment to zero. Beam observations and their interpretations are presented, and remedial measures are discussed.

• J.T. Volk, J. Annala, L. Elementi, N.M. Gelfand, K. Gollwitzer, J.A. Greenwood, M.A. Martens, C.D. Moore, A. Nobrega, A.D. Russell, T. Sager, V.D. Shiltsev, R. Stefanski, M.J. Syphers, G. Wojcik
  Fermilab, Batavia, Illinois

It was observed during the early part of Run II that dipole corrector currents in the Tevatron were changing over time. Measurement of the roll for dipoles and quadrupoles confirmed that there was a slow and systematic movement of the magnets from their ideal position. A simple system using a digital protractor and laptop computer was developed to allow roll measurements of all dipoles and quadrupoles. These measurements showed that many magnets in the Tevatron had rolled more than 1 milli-radian. To aid in magnet alignment a new survey network was built in the Tevatron tunnel. This network is based on the use of free centering laser tracker. During the measurement of the network coordinates for all dipole, quadrupole and corrector magnets were obtained. This paper discusses roll measurement techniques and data, the old and new Tevatron alignment network.