The use of standard beam-based alignment methods such as Ballistic Alignment and Dispersion Free Steering is not sufficient to decrease emittance growth in the CLIC main linac to acceptable levels.
Previous simulations showed that so-called emittance tuning bumps might cure this problem. For CLIC the emittance reduction using tuning bumps is based on transversal offsets of cavities. For the tuning of the bumps, the emittance can be measured either locally or at the end of the linac. In this case the second method has been studied as it is more powerful. However, this method is also more complex due to crosstalk between different bumps, and the cavities have to be carefully chosen and combined to avoid the need for large number of iterations of the optimisation procedure. The detailed implementation of the tuning bumps will be described and performance in terms of speed and emittance reduction presented.