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The reference cavity was locked using a 21.5 MHz signal from a rack mounted board (FSS REF - Crystal Frequency Reference [http://www.ligo.caltech.edu/docs/D/D980353-C.pdf]). That turned out to have many problems and we removed it completely from the system circa 2008 with a fixed 21.5 MHz OCXO from Wenzel and an RF Amplifier (see [http://nodus.ligo.caltech.edu:8080/40m/986 elog]). The reference cavity was locked using a 21.5 MHz signal from a rack mounted board (FSS REF - Crystal Frequency Reference http://www.ligo.caltech.edu/docs/D/D980353-C.pdf). That turned out to have many problems and we removed it completely from the system circa 2008 with a fixed 21.5 MHz OCXO from Wenzel and an RF Amplifier (see [[http://nodus.ligo.caltech.edu:8080/40m/986|elog]]).

We got the design parameters for the reference cavity from [[http://www.ligo.caltech.edu/docs/D/D980670-00.pdf|D980670]]

|| Spacer Material || Fused Silica (Corning?) ||
|| Mirror Material || Fused Silica ||
|| Mirror T_HR || 300 +/- 30 ppm ||
|| Mirror R_AR || < 500 ppm ||
|| Mirror RoC || 500 mm ||
|| Cavity Length || 8" (203.2 mm) ||
|| Cavity Finesse || 10000 ||
|| Cavity g-factor (g1*g2) || 0.352 ||
|| Cavity waist || 0.218 mm ||
|| Cavity FSR || 737.7 MHz ||
|| Cavity pole || 35.2 kHz ||
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See also [[Frequency Stabilization Servo]]. Some FEA of the LIGO/40m reference cavity using COMSOL: [[/FEA]]
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Some FEA of the LIGO/40m reference cavity using COMSOL:
[[/FEA]]		 ----
 See also [[Frequency Stabilization Servo]].

The reference cavity was locked using a 21.5 MHz signal from a rack mounted board (FSS REF - Crystal Frequency Reference http://www.ligo.caltech.edu/docs/D/D980353-C.pdf). That turned out to have many problems and we removed it completely from the system circa 2008 with a fixed 21.5 MHz OCXO from Wenzel and an RF Amplifier (see elog).

We got the design parameters for the reference cavity from D980670

Spacer Material

Fused Silica (Corning?)

Mirror Material

Fused Silica

Mirror T_HR

300 +/- 30 ppm

Mirror R_AR

< 500 ppm

Mirror RoC

500 mm

Cavity Length

8" (203.2 mm)

Cavity Finesse

10000

Cavity g-factor (g1*g2)

0.352

Cavity waist

0.218 mm

Cavity FSR

737.7 MHz

Cavity pole

35.2 kHz

Some FEA of the LIGO/40m reference cavity using COMSOL: /FEA

Reference_Cavity (last edited 2012-01-03 23:02:39 by localhost)