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Entry  Thu Oct 13 23:58:38 2011, Koji, Update, LSC, fixing REFL165  PA131612.jpgPA131618.jpg
    Reply  Sat Oct 15 16:42:08 2011, Koji, Update, LSC, Testing REFL165  REFL165_test_111014_KA.pdfREFL165_transimpedance2.pdf
       Reply  Sat Oct 15 17:06:20 2011, Koji, Update, LSC, Installation REFL165  
       Reply  Sun Oct 16 02:30:00 2011, rana, Update, Electronics, Testing REFL165  
    Reply  Wed Mar 1 17:25:28 2017, Steve, Update, LSC, MCREFL condition pictures IMG_3646.JPGmcRefl_1.jpgmcRefl_3.jpgmcRefl_5.jpg
       Reply  Fri Mar 17 14:49:09 2017, gautam, Update, LSC, MCREFL condition pictures IMG_7219.JPGMCREFL_X.pdfMCREFL_Y.pdf
Message ID: 5671     Entry time: Sat Oct 15 16:42:08 2011     In reply to: 5664     Reply to this: 5672   5673
Author: Koji 
Type: Update 
Category: LSC 
Subject: Testing REFL165  

Test results of new REFL165 (the first attachment)

- The resonant freq 166.2MHz, Q=57 (previous Q was ~7)

- If we believe the TF measurement, the transimpedance at the resonance is 7.8k [V/A] and the shotnoise intercept current of ~1mA.
The linearity of the peak was confirmed by changing the modulation level of the beam.

- There is a riddle: the white light test indicates 4.5k [V/A] and 2.8mA for those numbers.
There are big descrepancies from those by the TF measurements.

Further analysis of the descrepancies:

Using the noise measurements with different DC current levels, the transimpedance for each frequency can be reconstructed.

Does this indicate the satiration by the white light???

- The TF measurement shows consistent mag&phase relationship at the resonance (c.f. LISO fit).
So this steep resonance is not an artifact by a noise or glitch but the real structure of the electronics.

- The TF measurement has been done with the photocurrent of ~0.3mA, while the transimpedance measurement
with the white light illumination has the practical effect only when the DC photocurrent is larger than 1mA
because of the circuit noise. Does this higher photo current affected the resonance?

- The off-resonant transimpedance agree with the TF measurement as far as we can see with those measurements.
This may mean that the actual resonant structure has been affected in the white light measurement.
(i.e. not the saturation of the RF opamp which causes the change of the gain at any freq.)
Is the above mentioned higher DC current causing the change of the diode capacitance or other property of the diode or the inductors???

Attachment 1: REFL165_test_111014_KA.pdf  422 kB  | Hide | Hide all
REFL165_test_111014_KA.pdf REFL165_test_111014_KA.pdf REFL165_test_111014_KA.pdf REFL165_test_111014_KA.pdf
Attachment 2: REFL165_transimpedance2.pdf  76 kB  Uploaded Sat Oct 15 17:42:51 2011  | Hide | Hide all
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