Tuning of final focus system for future linear colliders

The author examines a procedure to correct various initial machine errors, using the JLC final focus system as an example. A simulation shows that the combination of alignment by the beam method and linear knobs is a possible tuning method for the start-up of the final focus system. It allows a conventional level of initial alignment of the magnets, setting errors and sensitivity of position monitors. It also has to rely on the spot size monitor at the interaction point and the accuracy and the stability of the magnet movers. It is not necessary for the magnet movers to be able to set the position in the submicron accuracy, because one can use a correction dipole instead of such a small displacement of a quadrupole. In the simulation, about 400 pulses were used to tune up the entire beam line. Since the linear collider has a few hundred Hz repetition rate, the actual speed of the tuning is limited by the response of the movers and the monitors. This means that, in the actual situation, one can use more pulses to determine the displacement of the magnets and the minimum search than in the simulation. Therefore, the accuracy of the method may become even better than the simulation.<>