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PMT Efficiency and Magnetic Effects

PMT Efficiency and Magnetic Effects. Steven Dazeley (Louisiana State University). Three questions are of interest. How much does a magnetic field effect the efficiency of PMTs? Use Earth’s magnetic field (~0.5gauss)

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PMT Efficiency and Magnetic Effects

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  1. PMT Efficiency and Magnetic Effects Steven Dazeley (Louisiana State University) Steven Dazeley

  2. Three questions are of interest • How much does a magnetic field effect the efficiency of PMTs? • Use Earth’s magnetic field (~0.5gauss) • What is the efficiency of a PMT w.r.t position on the cathode - without the magnetic field • Use mu-metal coated dark box to eliminate the field (actually reduced ~10x) • Test different possible mu-metal cone configurations – compare with mu-metal coated dark box results (Later – sorry) Steven Dazeley

  3. Setup • Testing 2 Hamamatsu 8” R5912 PMTs and a SK 8” • The 8” SK PMT results were presented by Svoboda at a previous meeting • Test ~30 points on each PMT cathode using a special crown that guarantees consistent angles Steven Dazeley

  4. Why? • Near and far detectors should be the same within ~1% • If PMT efficiencies depend heavily on their orientation w.r.t a field, then we have to either be very careful to arrange PMTs to cancel this effect (difficult if every PMT is different), or eliminate the field • Eliminating the field = $ • Or calibrate the effect? Steven Dazeley

  5. X and Y axis Steven Dazeley

  6. X axis (North and East) North - East Steven Dazeley

  7. Y Axis (West and North) West - North Steven Dazeley

  8. SK 8” Steven Dazeley

  9. Where is the efficiency drop-off? Black – x+20 degrees Blue – x+45 degrees Steven Dazeley

  10. Mu-metal dark box (X axis) North - East Black – North Blue - East Steven Dazeley

  11. Mu-metal dark box (Y axis) West - North Black – West Blue - North Steven Dazeley

  12. 2nd Hamamatsu PMT X - Axis North - East Black – North Blue - East Steven Dazeley

  13. 2nd Hamamatsu PMT Y Axis Black – West Blue - East West - North Steven Dazeley

  14. Steven Dazeley

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