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Update on Attenuation Lengths and Light Yield

Update on Attenuation Lengths and Light Yield. C. Alfieri. 20.08.2014. Attenuation Lengths of the new 14080801-06 batch measured by Kuraray. Attenuation lengths below expectations confirmed. We compared LY for two 1000ppm fibre samples (lot 14080803 and the “Dortmund sample ”).

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Update on Attenuation Lengths and Light Yield

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  1. Update on Attenuation Lengths and Light Yield C. Alfieri 20.08.2014

  2. Attenuation Lengths of the new 14080801-06 batch measured by Kuraray. • Attenuation lengths below expectations confirmed.

  3. We compared LY for two 1000ppm fibre samples (lot 14080803 and the “Dortmund sample”). • LY measured up to 240cm. • The Dortmund sample shows on average 20% higher LY than the 2014 1000ppm sample.

  4. With our set-up, we could measure LY with just 1 signal fibre at every distance for the Dortmund sample. • Our theoretical model well fits the one-single-fibre spectra (it didn’t with 4 fibres). • We could extract Npe with a ROOT routine. P=Poisson G=Gauss

  5. With 4 fibres we underestimate low photoelectrons’ contribution. Due to: Misalignment?? (Electrons maybe don’t always pass through all the 4 fibres). ≈270μm Xtalk?? (Fibres are tangled: can some helical mode photon pass from one fibre to another?)

  6. Single fibre and 4 fibre LYs show differences • Single fibre LY (from fit) multiplied by 4 is ≈10% higher than 4fibre LY (from COG). • Ly1fibre*4/Ly4fibre quite stable at all distances. • Still possible to use 4 fibre for relative LY measurements (signals easier to read-out for fibres with low LY at distances >2m).

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