We present a status report on the investigation of the Mobius scheme for producing equal-emittance round beams at CESR. An insert has been constructed with six 45/spl deg/ rotated quadrupoles which interchange horizontal and vertical betatron oscillations on each passage. We describe the single-beam dynamics and the limitations introduced by the chromaticity correcting sextupoles. We also report on our two-beam experience.

A potential advantage of the “Mobius” scheme, or any other strongly coupled lattice, is that the normal-mode oscillations are damped at rates which depend on both the horizontal and vertical chromaticities. This opens up the possibility of maintaining adequate damping even for quite negative chromaticity in one plane, provided the other is appropriately increased to compensate. This “chromaticity sharing” has been observed at CESR by introducing resonant coupling with weak skew quadrupoles and observing the coherent damping rates of shock-excited betatron oscillations

As a first step toward testing the proposed "Mobius" scheme, we used existing CESR elements to collide round, rather than flat, beams. The tune shift parameter, /spl xi/, was inferred from the beam profiles and current, was compared to the tune shift of the coherent beam-beam /spl pi/ mode, and was corroborated by luminosity measurement. Values of /spl xi/ up to 0.09 were achieved without significant lifetime reduction.

We discribe various beam diagnostic devices in use at CESR, an 8 GeV electron-positron storage ring operating primarily in the 4.7 to 5.5 GeV beam energy range. Getting the last 20% of performance depends to some extent on empirical tuning and appropriate presentation of various parameters is very important. Several devices are most useful in machine studies and we describe their operation. The individually regulated quadrupoles in CESR provide unique opportunities for lattice measurements and calibration of beam position monitors.

CESR has produced e+ e- collisions for high energy physics in the very productive T region (4.7 to 5.7 GeV per beam) since the fall of 1979. The peak luminosity recorded during physics data taking over that period is shown in Fig. 1. The dramatic increase in the luminosity has resulted from the reduction of ßy* from 11 cm to 3 cm, an increase in σx *, and increases in the vertical aperture. Furthe...