Study of alternative ILC final focus optical configurations

The current design of ILC final focus achieves perfect first order chromaticity correction in both horizontal and vertical planes. Based on RDR FFS optics a set of alternative optical configurations were studied in which the horizontal beam size at the IP is increased while at the same time the vertical one is decreased, with the goal of reducing beamsstrahlung emission. Luminosity reduction due to the hour glass effect must be considered because βy⁎/σz⁎ becomes much smaller in this case. The beam–beam interaction simulation by Guineapig++ was used for evaluation. Reduced bunch lengths are used to make sure that the obtained luminosities are not lower than those of the ILC RDR configuration.