On Sep 12, 2009, at 2:04 AM, Roarty, Francis X wrote:
Would running the test at temperature extremes to compare for change in sag rate/displacement isolate the mechanical from the light path?
The test can be fixed by simply using much smaller components, and much sturdier component mounts. There is no need for the splitter or mirror surface areas to be much larger than the laser beam. Another improvement might be to machine the beam path into a thick base, so as to provide maximum support for the components, which would be mounted in recesses machined into the base. I think this kind of experiment is best conducted in a stable and temperature controlled environment, preferably in a basement or underground, in order to avoid the need to continually adjust the mirrors when looking for diurnal effects. The diurnal effects noted by the author may in fact be temperature change induced. Temperature changes affect not just the mirrors and splitter, but the entire base as well. That can produce large effects, especially near dawn and dusk.
Best regards, Horace Heffner http://www.mtaonline.net/~hheffner/
