Pepperpot Emittance Calculations

Simon Jolly

Imperial College

29th August 2007

29/8/07 Simon Jolly, Imperial College 2

Pepperpot Emittance Measurement

• As with Slit-Slit scanner, pepperpot emittance measurement is sensitive to cut level.

• Have to impose some sort of cut due to inherent 100 count noise from camera and background noise.

• Scintillator degrades over time: can we specify cut level and scintillator lifetime to give consistent emittance measurement?

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Pepperpot vs. Slit-Slit: 11kV X Emittance

0.71 mm mrad

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Pepperpot vs. Slit-Slit: 11kV Y Emittance

1.07 mm mrad

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Pepperpot vs. Slit-Slit Pre-Conclusions

• Shape and distribution broadly the same, but much broader for pepperpot measurement.

• Emittance values higher for pepperpot single pixel measurement compared to slit-slit.

• Current cut is 119 counts: can we improve shape/emittance values with improved cut?

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5/7/07 1454 Image, Light Intensity

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5/7/07 1454 Image, Emittance Variation

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5/7/07 1525 Image, Emittance Variation

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6/7/07 All Images, Light Intensity

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6/7/07 All Images, Average Spot Emittance

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6/7/07 All Images, Single Pixel Emittance

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Pepperpot 11kV: 119/250 Cut

250 cut119 cut

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Pepperpot vs. Slit-Slit: 11kV X Emittance

0.71 mm mrad

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Pepperpot vs. Slit-Slit: 11kV X Emit, 250 Cut

0.39 mm mrad

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Pepperpot vs. Slit-Slit: 11kV Y Emittance

1.07 mm mrad

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Pepperpot vs. Slit-Slit: 11kV Y Emit, 250 Cut

0.45 mm mrad

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Cut Variation Conclusions

• Variation in cut level produces clear change in emittances.

• Currently using new cut level of 250 counts for emittance measurements.

• More analysis needed into cut level as a function of image intensity.

• Scintillator lifetime ~1 hour integrated beam time: more tests with Ce-Quartz needed.