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Entry  Tue Jun 28 07:46:54 2011, Suresh, Update, IOO, Power incident on REFL11 and REFL55 
    Reply  Tue Jun 28 10:11:13 2011, steve, Update, IOO, Power incident on REFL11 and REFL55 
    Reply  Tue Jun 28 14:21:41 2011, kiwamu, Update, IOO, something wrong ? : Power incident on REFL11 and REFL55 
       Reply  Thu Jul 7 14:27:16 2011, Suresh, Update, IOO, something wrong ? : Power incident on REFL11 and REFL55 
Message ID: 4954     Entry time: Thu Jul 7 14:27:16 2011     In reply to: 4898
Author: Suresh 
Type: Update 
Category: IOO 
Subject: something wrong ? : Power incident on REFL11 and REFL55 

Just tying up a loose end.  The next day Kiwamu and I checked to see what the trouble was.  We concluded that the PRM had not moved during my measurement though I had 'Misaligned' it from the medm screen.  So all the power levels measured here were with the PRM aligned.  The power level change was subsequently measured and e-logged

Quote:

The measured change in the REFL DC power with and without PRM aligned seems unacceptably small.  Something wrong ?

The difference in the power with and without PRM aligned should be more than a factor of 300.

         [difference in power] = [single bounce from PRM] / [two times of transmission through PRM ]

                                          = (1-T) / T^2 ~ 310,

where T is the transmissivity of PRM and T = 5.5% is assumed in the calculation.

Also the reflectivity of MICH is assumed to be 1 for simplicity.

Quote from #4894

We now have (with the PRM misaligned):

REFL11:  Power incident = 7.60 mW ;  DC out = 0.330 V  => efficiency = 0.87 A/W

REFL55:  Power incident = 23 mW ;  DC out = 0.850 V  => efficiency = 0.74 A/W

and with the PRM aligned::

REFL11:  DC out = 0.35 V  => 8 mW is incident

REFL55: DC out = 0.975 V  => 26 mW is incident

 

 

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