Reports until 12:40, Friday 04 October 2013
H1 AOS
sheila.dwyer@LIGO.ORG - posted 12:40, Friday 04 October 2013 - last comment - 16:58, Monday 07 October 2013(7998)
more beam measurements

Joe, Pablo, Cheryl, Sheila

We measured the beams coming out of the HAM2 viewport, with the nanoscan head 2 feet 6 inches from the viewport.  (in the first version of this alog I wrote the wrong distance)

For the brighter beam we measured beam diameters: 2549 um horizontal, 2632 um vertical.  after rorating the scan head 90 degrees we measured 2650um vertical, 2561 um horizontal.  

For the dim beam we measured 7160um vertical, 5972 um horizontal after rotating  by 90 degrees we got 6077um horizontal 5865um vertical. 

We also measured the beam in HAM1, in the same location as wensday (we move the BS for the RF PD to 16 inches after M2, we put the nanoscan 40 inches after the BS, there we got 4025 um vertical, 4126 horizontal.  After rotating the head 90 degrees we got 4045 um vertical 4020um horizontal.  

Comments related to this report
guido.mueller@LIGO.ORG - 13:43, Friday 04 October 2013 (8000)
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Hi Sheila,

Can you be a little more specific which beam you measure where? 
The 4000um diameters sound good but I don't know what you mean with the brighter beam and what with the dimer beam.
sheila.dwyer@LIGO.ORG - 21:48, Saturday 05 October 2013 (8011)
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Hi Guido-

I believe the brighter beam is the reflection off of PRM, although I haven't looked at the layout to double check.  As you face the viewport, near the veiwport the dim beam is on the right while the bright beam is on the left.  If you move to about 3 feet away from the viewport they cross, and the dim one is on the left if you are facing the veiwport.  Pablo watched the spots on the wall as I moved the PRM alignment, and the bright one moved.  

sheila.dwyer@LIGO.ORG - 15:14, Sunday 06 October 2013 (8013)
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I should have been more clear, the first two measurements are of beam sizes for SM2 trans, coming out of the HAM2 veiwport where IOT2R would normally be. 

paul.fulda@LIGO.ORG - 09:32, Monday 07 October 2013 (8017)
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Looking at the table layout for HAM2 (D0901083), I would expect the SM1 forward trans beam (from PMMT2 a.k.a. IM3) to be the dimmer beam, since this beam is split twice before making its way to the viewport. The SM1 return trans beam is not split at all before getting to the viewport. (I think you already came to this conclusion).

From the model, using rather rough estimates for the distances after IM4 transmission (+/- 2 inches), we expect that the SM1 forward trans beam (dimmer beam) where you measured it should have diameters of 6.20mm horizontal and vertical. The SM1 return trans beam (brighter beam) where you measured it should have diameters of 2.68mm horizonal and 2.67mm vertical. Not so far away from what you measured...

I'll try to get more precise numbers for the after-IM4-trans distance from Luke and update accordingly.

paul.fulda@LIGO.ORG - 09:45, Monday 07 October 2013 (8019)
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Apologies, everywhere I wrote "SM1" I meant "SM2". Or IM4, they are the same mirror.

sheila.dwyer@LIGO.ORG - 11:34, Monday 07 October 2013 (8020)
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SM2TransReturn1.png is a screen shot of the nanoscan program with the bright beam, when apperature 1 veritcal. 

SM2TransForward1.png  the dimmer beam, first with Apperature 1 horizontal then SM2TransForward2.png is with the apperature 1 vertical.  

I haven't figured out how to export data from the software, and I can't uplaod .nsd files to the alog, but if anyone wants the data it is available at http://www.ligo-wa.caltech.edu/~sheila.dwyer/NanoScanData/IO/

You can use the free Nanosan software from Ophir/ Newport to open these files. 

We saw that the Forward beam looks like it could possibly be clipping, Joe tried to move the location of the nanoscan head but the beam profile didn't get any better. 

Images attached to this comment
paul.fulda@LIGO.ORG - 15:27, Monday 07 October 2013 (8028)
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Just an update on the expected beam sizes with more accurate distances used in the model (good to 1/4" or so, inlcuding IM4 substrate and viewport substrate effect):

SM2trans forward 2wx=6.349mm, 2wy=6.3455mm

SM2trans return 2wx=2.6813mm, 2wy=2.6697mm

sheila.dwyer@LIGO.ORG - 16:58, Monday 07 October 2013 (8031)
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