AN e+e- COLLIDER IN THE VLHC TUNNEL

We describe the design of an e + e - collider that could be installed in the tunnels of the VLHC to run before that machine. We consider the arguments required to maximize the luminosity and indicate what effects would limit the machine performance. We also describe the primary technical issues involved with the construction of the components and consider how costs could be minimized. where ξy, P , ρ, and β y* are the beam-beam tune shift, radiated synchrotron power for two beams, bending radius, and the beta function at the interaction point. While the beam-beam tune shift, ξy, is in the range of 0.03 for most lepton colliders, it was found at LEP that very stable operation was obtained at high energies with values of 0.08-0.09. These values were, however, limited by the bunch current at injection. During the last run of LEP, the goal was to reach the highest energy possible, and the beam-beam limit was not reached. Since ξ y, scales with the damping decrement, we expect values of 0.14 - 0.17 at 185 GeV with two IR's. With a single IR, the beam-beam parameter could be higher, giving a luminosity close to 10 34 cm -1 s -2 . We have assumed that the radiated power, P, for both beams will be 100 MW. In addition to its effect on the luminosity, this number determines the size of the cooling system, the size of the rf system required to replace this