High-β* Optics for the LHC

Special high-β* optics have been requested to allow for the study of diffractive and elastic scattering at the LHC in the very forward region. Several options are considered and described in detail in this note. These optics all require a special phase advance of π2 in at least one plane between the IP and a roman pot detector. The phase advances of the high beta insertions is lower than for the normal physics optics and requires global tune adjustments to keep the overall LHC tunes constant. The requirements on luminosity and intensity are rather modest. These optics will be used without crossing angle and the number of bunches will be limited to a maximum of 156. An optics at an intermediate β* of 90m has been requested by TOTEMfor the first year of LHC operation and should be compatible with normal physics running in the other IPs. Commissioning of the very high-β∗ (>1km) optics is for later years and requires dedicated operation at reduced emittance and hardware changes