2015 Beam Profile Measurements

We modified the setup this year to increase the distance between the beam profiler (camera) and the laser image (screen).  A distance of 4 m is enough to allow the lens we have to create a focussed image, but the final image only takes up a small area on the detector surface and therefore does not allow us to make the most of the equipment.

A better solution will be to employ a different lens, or at least to place the optical filters in front of the lens, rather than between the lens and the detector.

Despite these difficulties, we were able to extract some images showing cold-spots:

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Although we determined that these were equally obvious to the naked eye by looking at the aiming beam.  When removing the damaged protective window (the cause of the cold-spot), everything looked fine to start with, although perhaps a little saturation was creating the appearance of noise:

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After a bit of lunch, we tried the same again and found something more interesting:

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There is something here which can’t easily be seen by the naked eye.  Mr Atkins very kindly let us use his ZAP-IT paper for comparison:

ZAP-IT paper profiles

Although we are limited here by the scanning resolution, we can still see that the cold-spot is easily picked up on the ZAP-IT on the left, and there is some discrepancy on the right showing a slightly ‘colder’ region.  We all agreed that the beam profiler showed some more detail in this case, although the paper was much easier to use.

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