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Emittance Measurement Work

Emittance Measurement Work. 08 /07/ 10 Jimmy Garland The University of Manchester The Cockcroft Institute. Emittance Measurement Work.

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Emittance Measurement Work

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  1. Emittance Measurement Work 08/07/10 Jimmy Garland The University of Manchester The Cockcroft Institute

  2. Emittance Measurement Work • Normalised transverse emittance was modeled in GPT form the gun to the end of the booster for difference initial bunch distributions from the simulated cathode. • Emittance was measured using a variety of screen based methods after the booster.

  3. Emittance Measurement Work The nominal laser spot size on the cathode is a circle of radius 2mm. This photograph of the laser on the cathode shows a more elliptical laser spot profile. The profile is elongated in the y direction with respect to the beam line by a factor of roughly 2.

  4. Emittance Measurement Work Emittance for a nominal circle (blue) and an ellipse (yellow and red) distribution at the cathode derived from the photo of the laser on the cathode.

  5. Emittance Measurement Work

  6. Emittance Measurement Work Using a hard edged, externally generated distribution. Showing a nominal circle (blue) and ellipse of y/x ratio 2/1 (yellow and red).

  7. Emittance Measurement Work As the ratio of the x to y transverse size increases at the cathode, the difference in emittance for x and y increases after the booster. The x emittance increases as opposed to the y due to the 90 degree rotation form the 2 solenoids.

  8. Emittance Measurement Work

  9. Emittance Measurement Work Conclusions: • The measured transverse emittance agrees reasonably well with GPT simulations when using an initial cathode spot derived from the photograph of the laser on the cathode. • The laser spot size on the cathode has a large effect on the measured emittance and the difference between x and y transversely. • Striving to make the laser circular would appear to reduce the discrepancy between x and y measured emittance based on simulation.

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