Coil size and geometric field quality in short model dipoles for LHC

We have measured the magnetic field at room temperature and at 1.8 K on mor e than twenty, l-m long, single aperture LHC superconducting dipole models. The magnets feature either a 5-block coil, geometry or the baseline 6-bloc k geometry foreseen for the LHC, Comparison of warm and cold measurements s how that the coil geometry is essentially unchanged during cooldown. We hav e therefore used mechanical measurements taken on the coil and collars duri ng assembly to estimate the azimuthal coil length. Based on these measureme nts we show here that the sensitivity of allowed harmonics on coil size is in goad agreement with the prediction obtained from the numerical model use d for designing the LHC magnets.