Reports until 23:53, Tuesday 18 April 2017
H1 General
patrick.thomas@LIGO.ORG - posted 23:53, Tuesday 18 April 2017 - last comment - 11:00, Wednesday 19 April 2017(35649)
Beam spot on ALSX camera image in NLN
If I recall correctly this image (attached) is normally dark in NLN?
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jenne.driggers@LIGO.ORG - 11:00, Wednesday 19 April 2017 (35663)

Looking at the auto-captured images, indeed you are correct that there is some light where there didn't used to be any. 

The work that could have affected this is the placement of the new black glass beam dump (alog 35636).  Not that there should be any significant reflection from this dump (it has 5 bounces from black glass), any reflection would go in the opposite direction from the ALSX camera.  So, I don't think it could be reflection from this beam dump.  What is possible is that the old razor dump was catching stray beams in addition to the main one, and the black glass dump with a slightly smaller profile isn't catching that stray beam. 

I think dumping the main POP beam with the new dump is still overall helpful, and we'll see if this extra stray beam actually has any affect on the interferometer.  It's small enough in power that it wasn't visible on the IR card we were using, although we didn't utilize an IR viewer to see much dimmer beams.

Right now, I think we should monitor things to see if this beam has any effect, and we can look at ISCT1 again next Tuesday.