= Length Sensing and Control Design =
This page discusses the design of the LSC system of the 40m Upgrade

== Ports ==
The Power Spectrum for each port is provided. From that we identify the optimum sensing signals.

[...]
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== Sensing Matrix ==
For locking, the baseline plan is to use the same error signals of AdvLIGO:

|| '''DOF''' || '''Signal''' ||
|| CARM || REFL_I1 ||
|| DARM || AS_DC ||
|| PRCL || POP_I1 ||
|| MICH || POP_Q2 ||
|| SRCL || POP_I2 ||

In case that '''3f signals''' will be used for lock acquisition, as a result of Optickle simulations, we propose the following sensing matrix:

|| '''DOF''' || '''Signal''' ||
|| X || POX ||
|| Y || POY ||
|| PRCL || REFL_32I ||
|| MICH || REFL_31I ||
|| SRCL || REFL_32Q ||

[...]
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== Cavity Absolute Lengths ==
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=== Arm Cavities ===
Antiresonance conditions fro both sidebands [...]
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=== Schnupp Asymmetry ==
Arguments on the Schunpp asymmetry design;
 * dependence on the asymmetry of central cavity's coupling
 * dependence of sideband output power ("throughput power" - K. Arai) to asymmetry
 * different designs for different PRMs (initial, temporary 10%; final 5.5%)
 * guidelines to change the asymmetry in different circumstances (alignment, etc.) 
 * [...]
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=== Power Recycling Cavity ===
 * ideal lengths
 * lengths corrections
 * [...]
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=== Signal Recycling Cavity ===
 * ideal lengths
 * lengths corrections
 * [...]