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The attached trend shows a problem with the QPD sums.
Why are ETMX and ITMX so much lower than ETMY and ITMY? Are the laser's dying? Or is it the gain inside the QPD? Or the reflectivity of the coatings?
Steve - please check on Monday the laser powers and the ETM/ITM reflectivity for HeNe lasers. Maybe we have to increase the transimpedance gain in the heads.
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ETMX and ETMY have 0.2 mW returning to their QPDs........so the gain must lower at ETMX
ITMX laser 1103P has only 0.67 mW output and 0.025 mW returning to the QPD.
ITMX and ETMX oplev lanching paths have lenses without AR coating. This is my fault. I will buy them.
ETMX 0.2 mW 900 counts
ITMX 0.025 1300
SRM 0.04 2600
BS 0.05 3500
PRM 0.06 4000
ETMY 0.2 9000
ITMY 0.3 14500 |