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Minutes of the CLIC Meeting - 28 March 2003

Emittance measurements and beam optimization using Laser Wire Scanners

Summary of Daresbury Damping Ring Workshop
Gregory Penn, Maxim Korostelev

Gregory Penn presented his work done for the CLIC study:
The scattering cross-section of an electron beam with a laser pulse can be used as a diagnostic for beam profiles and hence emittance. With realistic laser parameters, it should be possible to measure emittances for the CLIC beam (where the scattering is in the Compton regime) with an accuracy of around 10%. Simulations in GEANT4 will be presented showing that, if losses are as anticipated, the accuracy of the measurement will be limited primarily by the low statistics for detected Compton scattering events. A basic scheme for optimizing the beam emittance using "emittance bumps" is also considered, where a single moderately accurate emittance diagnostic can be used with a large number of tuning parameters to slowly optimize the CLIC beam. Emittances within a few percent of optimum can be achieved; when ground motion effects are considered, the results are not as good.
copy of his transparencies (pdf format)
The present design for the Final Focus has a very low phase advance and is not compatible with the required phase advance for emittance measurements.
Gregg showed that assuming the required phase advance, the emittance bumps can be optimized with a single emittance measurement station in the dispersion suppressor. Already a simple 1-dimensional optimization of 10 bumps with an emittance measurement precision of 10% can reduce an initially large emittance to less than about 4% above nominal and keep it to this level.

Maxim Korostelev gave a summary of the Daresbury Damping Ring Workshop.
copy of his transparencies (not available yet)

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Frank Tecker  - Last updated  28-03-2003