Early in Run2, there was an effort to compare the different emittance measurements
in the Tevatron (flying wires and synchtotron light) and understand the origin of
the observed differences. To measure the beta function at a few key locations near
the instruments, air-core quadrupoles were installed. By modulating the gradient of
these magnets and measuring the effect on the tune, the lattice parameters can be
extracted. Initially, the results seem to disagree with with other methods. At the
time, the lattice was strongly coupled due to a skew component in the main dipoles,
caused by sagging of the cryostat. After a large fraction of the superconducting
magnets were shimmed to remove a strong skew quadrupole component, the results now
agree with the theoretical values to within 20%.