Collimator Wake Fields in the Slc Final Focus*
نویسندگان
چکیده
The SLC final-focus system accommodates 29 fixed or adjustable collimators for machine protection and background reduction. By amplifying pulse-to-pulse orbit variations and by generating emittance growth, collimator wake fields may degrade the beam quality at the interaction point (IP). In the SLC final focus, collimator halfapertures are larger than the bunch length, so that the standard collimator-wake formula of Bane and Morton does not apply. Numerical wake-field calculations for SLC parameters agree quite well with the high-frequency impedance of a step-out transition, derived by Gianfelice and Palumbo. Due to the nature of a final-focus system, the wake-field kicks from all collimators add coherently, and the overall impact on luminosity can be significant. This paper suggests that collimator wake fields in the final focus provide a possible explanation for the 30% discrepancy between expected and measured luminosity in the 1994/95 SLC run.
منابع مشابه
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