A machine can have good dynamic aperture but poor beam lifetime. Semi-analytic estimates of the beam lifetime seem to be an essential complement. Presently schemes to correct the resonance effects are being developed and will be tried out this year. It will also be of great interest to see how high we can go with the beam-beam parameter. On the collective effects side, detailed calculations of impedance and loss factors continue and an impedance database has been implemented.
Strong scraping leading to short beam lifetimes is used to calibrate the loss monitors.
The loss monitors are sufficiently linear and sensitive to measure beam tails corresponding to life times of several thousand hours down to minutes. As presented in the EPAC 96 in Barcelona, significant non-Gaussian beam tails have been observed in LEP both in the horizontal and vertical plane. The results are compared to theoretical tracking studies. More recently, using additional collimators in regions with and without dispersion, the importance of the combined effect of energy loss in the scattering processes and dispersion to launch particles at large amplitudes could be demonstrated. It could be shown in measurements and simulations that a large fraction of the particles in the tails have a relatively large momentum deviation.