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Message ID: 6355     Entry time: Mon Mar 5 14:10:35 2012
Author: kiwamu 
Type: Update 
Category: LSC 
Subject: power budget on the AP table 

I checked the laser powers on the AP table and confirmed that their powers are low enough at all the REFL photo diodes.

When the HWP( which is for attenuating the laser power with a PBS) is at 282.9 deg all of the REFL diodes receives about 5 mW.

This will be the nominal condition. 

If the HWP is rotated to a point in which the maximum laser power goes through, the diodes get about 10 mW, which is still below the power rate of 18 mW (#6339).

I used the Coherent power meter for all the measurements.

The table below summarizes the laser powers on the REFL diodes and the OSA. Also the same values were noted on the attached picture.


 nominal power [mW]

(when HWP is at 282.9 deg)

expected max power [mW]

(when HWP is at a point where the max power goes through)

REFL11 5.5 10
REFL33 4.5 10
REFL55 5.3 10
REFL165 4.8 10
REFL OSA 0.7 0.7


A note:
I found that the OSA for the REFL beam was receiving a unnecessary bright laser.
So I put an ND1 attenuator stacked on the existing ND2 attenuator. The laser power entering in the OSA is currently at 0.7 mW.
Attachment 1: power_budget.png  2.684 MB  | Hide | Hide all
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