Fused Silica Research as long as Advanced LIGO Alex in addition to er Ageev, Gregg Harry, Jim Hough,

Fused Silica Research as long as Advanced LIGO Alex in addition to er Ageev, Gregg Harry, Jim Hough, www.phwiki.com

Fused Silica Research as long as Advanced LIGO Alex in addition to er Ageev, Gregg Harry, Jim Hough,

One, Toph, Contributor has reference to this Academic Journal, PHwiki organized this Journal Fused Silica Research as long as Advanced LIGO Alex in addition to er Ageev, Gregg Harry, Jim Hough, Steve Penn, Sheila Rowan, Phil Willems Overview Research has been conducted over the past several years to underst in addition to the fundamental loss mechanism in fused silica in addition to produce extremely low loss FS optics suitable as long as Advanced LIGO. Experiments have been per as long as med on fiber/rod samples over wide range of sizes reveal a clear surface loss dependence. Loss appears to be entirely in the surface. For each sample, loss also increases with frequency. Slowly “annealing” samples can lower loss, but not below the surface loss limit. BOB SAMPLE EXCITER Surface Loss & Effects of Annealing 8 mm fiber Q = 80 million, be as long as e annealing Q = 200 million, after annealing LIGO Test mass, if surface loss limited Q (predicted) = 2 billion SURFACE LOSS

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Frequency dependence of loss Willems has measured an Initial LIGO uncoated test mass in a low-loss suspension, Q = 120 million at 11 kHz. (This result is several times higher than any previous measurement on these masses. Suggests suspension losses in previous work.) Fit of frequency dependence predicts a Q = 170 million in LIGO frequency range. Required improvement in loss by annealing is small as long as large masses, thus low temperature anneal should be sufficient. Plot of highest Q’s measured in fused silica as a function of frequency. Annealing: Benefits & Challenges Annealing can greatly lower the mechanical loss as long as samples above the surface loss limit, including superpolished samples. Low temperature anneals (600° C) yield large decrease in loss ( 10) as long as superpolished samples. (St in addition to ard Anneal temp. 11,000° C) Annealing could change surface figure, optical absorption, or silicate bonding to support structure. Cool down rate is geometry dependent in addition to could be prohibitively long as long as Advanced LIGO masses. Silica Research Plan Explore optimal annealing curve as long as flame-drawn rod samples in addition to small superpolished disk samples as a function of geometry in addition to peak temperature. Test dependence on annealing atmosphere in addition to type of fused silica. Test annealed superpolished disks as long as changes in surface figure, contamination, in addition to optical absorption. If repolishing is required, measure the effect on the mechanical loss. Test impact of annealing on the silicate bonds connecting the “ears” to the test mass. Test optimize annealing procedure on LIGO-sized uncoated optics.

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