Kiwamu, Dave O, Paul, Elli

We used the digital cameras looking at the test masses to compare scattering from ITMx and ITMy and from ETMx and ETMy.  From our measurements, it appears that ETMy scatters more light than ETMx.  The two ITMS scatter comparable ammounts of light.

We took photos of each of the test masses with the IR locked in each arm and the green beam misaligned.  Examples of the kind of scattering we saw are attached in scatteringPRofileExamples.jpg.

We then estimated the total light scattered onto each camera.

-The camera aperature was opened to maximum for each camera.  The exposure time was chosen to be the same for both ITMs and both ETMS, and the exposure was chosen so very few (<5) pixels were saturated.  When we did this, we noticed two particularly bright smears on ETMy.  We had to reduce the ETM exposure level right down before these two spots stopped saturating the camera.

-We also took background images of each optic with no IR or green beam in the arms at the same exposure level.  We also subtracted the noise floor from the images.  The images with background and noise removed are attached in backgroundAndNoiseRemoved.jpg.

-Finally the pixel value for each image was summed over the entire image to give a value proportional to the ammount of light scattered onto the camera.  These pixel sums are: (the matlab code for calculating these is attached.)

At a super low exposure time of 200microseconds, we detected no light scattered off of ETMx, but we can still see an appreciable ammount of light comming off of ETMY.

The ITMs were imaged at 10000microseconds exposure time, and the amount of scatter we see is much more comparable than for the ETMs.