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Proceedings Paper

Air convection noise of pencil-beam interferometer for long trace profiler
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Paper Abstract

In this work, we investigate the effect of air convection on laser-beam pointing noise essential for the long trace profiler (LTP). We describe this pointing error with noise power density (NPD) frequency distributions. It is shown that the NPD spectra due to air convection have a very characteristic form. In the range of frequencies from ~0.05 Hz to ~0.5 Hz, the spectra can be modeled with an inverse-power-law function. Depending on the intensity of air convection that is controlled with a resistive heater of 100 to 150 mW along a one-meter-long optical path, the power index lies between 2 and 3 at an overall rms noise of ~0.5 to 1 microradian. The efficiency of suppression of the convection noise by blowing air across the beam optical path is also discussed. Air-blowing leads to a white-noise-like spectrum. Air blowing was applied to the reference channel of an LTP allowing demonstration of the contribution of air convection noise to the LTP reference beam. The ability to change (with the blowing technique presented) the spectral characteristics of the beam pointing noise due to air convection allows one to investigate the contribution of the convection effect, and thus make corrections to the power spectral density spectra measured with the LTP.

Paper Details

Date Published: 29 August 2006
PDF: 12 pages
Proc. SPIE 6317, Advances in X-Ray/EUV Optics, Components, and Applications, 63170D (29 August 2006); doi: 10.1117/12.681297
Show Author Affiliations
Valeriy V. Yashchuk, Lawrence Berkeley National Lab. (United States)
Steve C. Irick, Lawrence Berkeley National Lab. (United States)
Alastair A. MacDowell, Lawrence Berkeley National Lab. (United States)
Wayne R. McKinney, Lawrence Berkeley National Lab. (United States)
Peter Z. Takacs, Brookhaven National Lab. (United States)

Published in SPIE Proceedings Vol. 6317:
Advances in X-Ray/EUV Optics, Components, and Applications
Ali M. Khounsary; Christian Morawe, Editor(s)

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