Using the Tevatron Electron Lens (TEL) as a Wire and other TEL Studies at FNAL

During a visit to FNAL, on March 1, 2004, we performed a two-dimensional grid scan - with 1-mm step size - of the TEL transverse position in the vicinity of the proton and pbar beams, while three bunches of either beam were excited by the TEL on every turn. The measured tune shifts of protons and pbars are compatible with expectation. The proton Schottky 'emittance' is strongly dependent on the TEL position, possibly due to a coherent interaction between protons and electrons. The relative position of protons, pbars and TEL can be determined in three different ways: from the TEL BPM readings, from the tune variation with TEL position, and from the loss-rate variation with the TEL position. The results are consistent at least within 1 or 2 mm, possibly better. Tunes and losses do not necessarily yield identical values for the beam position. Significant proton losses occurred when the TEL approached the proton beam. These losses decreased with the third power of the distance. They were the result of a longitudinal shaving, which might be related to a longitudinal interaction of TEL and proton beam and/or to the nonzero dispersion at the TEL.