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.< >
A detailed study of a dynamic aperture is given for electron storage rings with noninterleaved sextupole magnets. As a result of a cancellation of major transverse nonlinearities of sextupoles by ...minusital I transformers, other tiny terms such as fringe fields of quadrupoles and kinematical terms of drift spaces come to limit the transverse dynamic aperture. Results for transverse aperture in simulations can be explained by a simple one-dimensional model including these terms. In the longitudinal direction, a modulation of linear betatron motion by synchrotron oscillation is investigated as the source of the aperture limit.
An anomalous equilibrium emittance due to chromaticity of the focusing elements is predicted for electron storage rings. A simple model which describes the transverse beam distribution as a function ...of the longitudinal phase space is given to evaluate the anomalous emittance. The anomalous emittance can be a critical difficulty in achieving a very flat beam for high-luminosity electron-positron colliders.
A realistic, pulse-to-pulse, simulation is done to evaluate performance of an orbit feedback system in final focus system for future linear colliders. Accumulation of errors and long time stability ...of the system including time evolution of ground movement are estimated by this simulation. The result of simulation confirms that the orbit feedback system can maintain nanometer beam size at a colliding point and can keep beams in head-on collision.< >
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