Dispersion and betatron matching into the linac

Abstract
In high energy linear colliders, the low emittauce beam from a damping ring has to be preserved all the way to the linac, in the linac and to the interaction point. In particu- lar, the Ring-To-Linac (RTL) section of the SLAC Linear Collider (SLC) should provide an exact betatron and dis- persion match from the damping ring to the linac. A beam with a non-zero dispersion shows up immediately as an increased emittance, while with a betatron mismatch the beam filaments in the linac. Experimental tests and tuning procedures have shown that the linearized beta matching algorithms are insufficient if the actual transport liue has some unknown errors not included in the model. Also, ad- justing quadrupole strengths steers the beam if it is offset in the quadrupole magnets. These and other effects have lead to a lengthy tuning process, which in the end improves the matching, but is not optimal. Different ideas will be discussed which should improve this matching procedure and make it a more reliable, faster and simpler process.

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