Lear, Past, Present and Near Future

Abstract

LEAR¹,² is a strong focusing synchrotron/storage ring 78.5 meters in circumference. The design range of operating momenta is 0.1 to 2.0 GeV/c and its present role is to provide intense, pure beams of low energy antiprotons. It has a separated function lattice BODFOFDOB and is a symetric four period machine with 4 bending magnets and 8 focusing doublets. The result is a very strong focusing machine, with a phase advance per period of ≈ 250° and a betatron wavelength of ≈ 30 meters. γ = E/E₀ at transition is imaginary for the standard working points. This leads to a large value for ∣η∣, where

$$\frac{{\Delta F}}{F}/\frac{{\Delta P}}{P} = \eta = \frac{1}{{\gamma _T^2}} - \frac{1}{{{\gamma ^2}}}$$

which favours good mixing for the stochastic cooling process and helps the ultraslow stochastic extraction. Since η is always negative, the machine operates below transition over all of its large momentum range, thus avoiding negative mass effects and the problems associated with operating close to the transition energy.