Description:

The main goal for this phase is to establish reference "golden" orbit, optics and machine aperture with nominal 450 GeV optics. Orbit, tune, chromaticity, coupling, aperture, dispersion and beta-beat will be measured in detail. If necessary, we will correct these parameters within the specified tolerance windows.
If in previous phases (A.1, A.2 and A.3) we used the commissioning optics with increased Qh/Qv tune split, at the end of this phase we will have commissioned the nominal tunes for the energy ramp.
The chromaticity will be measured in detail and appropriate corrections will be made available for the energy ramp, treated in Phase A.6.

In addition, we will verify corrector polarities (according to a specified priority list).
If during early LHC operation we will perform a commissioning of the energy ramp (A.8) for single beams without going through the phase A.5 (where machine protection issues are addressed), in phase A.4 we will need to commission a minimum sub-system of collimators and protection devices in preparation for higher stored beam energies. This will be done after the reference orbit and optics will be established.
Some measurements/corrections will have to be repeated after the operation with two beams is established (A.6).