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| <<TableOfContents(3)>> --------- |
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| Modeling of the interferometer is used in order to design the optical configurations, the signal extraction and control schemes as well as the trouble shooting when you discover unknown phenomena with the interferometer operation. | |
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| IFo modeling tools can be found in the svn directory https://nodus.ligo.caltech.edu:30889/svn/trunk/ifomodeling/. | = Key points of the IFO Modeling = |
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| <<TableOfContents(3)>> | * Optical configuration * Recyling cavity lengths * Amount of Schnupp asymmetry * Effect of arm cavity resonancies * Power budget * Effect of losses * Recycling gains / selection of the recycling mirrors * Signal extraction * Length signal extraction * 3f demodulation for lock acquisition * Detuning * Signal handing off procedure * Alignment signal extraction * MC WFS * Dither alignment * Aux Laser injection = IFO Modeling Tools = IFO modeling tools can be found in the svn directoryhttps://nodus.ligo.caltech.edu:30889/svn/trunk/ifomodeling/. |
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| By ''Matt Evans''. | By Matt Evans. |
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| The Optickle modeling package is part of the ISCmodeling tools. The svn contain the latest version as of Feb-02-2010. Documented and written in a way that be read by others. |
The Optickle modeling package is part of the ISCmodeling tools. The SVN contains the latest version as of Feb-02-2010. |
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| * '''Arm Cavities''': resonant for the carrier; non-resonant for the sidebands; DARM offset = 40 pm | * '''Arm Cavities''': resonant for the carrier; non-resonant for the sidebands |
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| In particular, since the model add no microscopic offset to the SRM position, the SRC is by default resonant for the carrier. That means that when the arms are locked, the carrier becomes anti-resonant and f2 resonant. | In particular, since the model adds no microscopic offset to the SRM position, and the cavity length is set equal to c/f2, the SRC is by default resonant for the carrier. That means that when the arms are locked, the carrier becomes anti-resonant and f2 resonant. |
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| [attachment:IFOtuning.pdf In this document] I discuss the details behind the choices. ----- |
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| By ''Stefan Ballmer'' | By Stefan Ballmer |
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| Undocumented and written with code not easy to read. |
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| It is a semi-analythical modeling package. The two building blocks of the models are a Fabry-Perot function and a Michelson function. Each function replaces either a cavity or a Michelson, with an effective compound mirror. the functions return complex reflectance and transmittance. The input parameters are the most generic. The surfaces of all mirrors are treated individually, i.e. reflectance and transmittance can be set independently for each side of a mirror. | It is a semi-analythical modeling package. The two building blocks of the models are a Fabry-Perot function and a Michelson function. Each function replaces either a cavity or a Michelson, with an effective compound mirror. The functions return complex reflectance and transmittance. The input parameters are the most generic. The surfaces of all mirrors are treated individually, i.e. reflectance and transmittance can be set independently for each side of a mirror. |
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| Macroscopic length and microscopic offsets are passed to the functions as inputs. | Macroscopic length and microscopic offsets are passed to the functions as parameters. |
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| By nesting any combination of cavities in the proper way and order, one can build up a compound mirror representing coupled cavities or the whole interferometer. then the reflectivity and transmissivity of the compound mirror will be the Bright and Dark port outputs, respectively. | By nesting any combination of cavities in the proper way and order, one can build up a compound mirror representing coupled cavities or the whole interferometer. Then the reflectivity and transmissivity of the compound mirror will be the Bright and Dark port outputs, respectively. |
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| All functions contain a detailed help description. | All functions contain a help description on how to use it. |
Contents
IFO Modeling
Modeling of the interferometer is used in order to design the optical configurations, the signal extraction and control schemes as well as the trouble shooting when you discover unknown phenomena with the interferometer operation.
Key points of the IFO Modeling
- Optical configuration
- Recyling cavity lengths
- Amount of Schnupp asymmetry
- Effect of arm cavity resonancies
- Power budget
- Effect of losses
- Recycling gains / selection of the recycling mirrors
- Signal extraction
- Length signal extraction
- 3f demodulation for lock acquisition
- Detuning
- Signal handing off procedure
- Alignment signal extraction
- MC WFS
- Dither alignment
- Aux Laser injection
- Length signal extraction
IFO Modeling Tools
IFO modeling tools can be found in the svn directoryhttps://nodus.ligo.caltech.edu:30889/svn/trunk/ifomodeling/.
Optickle
By Matt Evans.
The Optickle modeling package is part of the ISCmodeling tools. The SVN contains the latest version as of Feb-02-2010.
It is independent to looptickle.
40m Upgrade Optickle Model
The 40m model file is contained under the config40m directory of looptickle.
The model represents the interferometer according to this layout:
attachment:IFO_diagram.png
A dual recycled interferometer could be set in different configurations (for a discussion on the topics see: Kokeyama K. et al. Class. Quantum Grav. 25 (2008) 235013 (12pp)).
The 40m will follow the choices for Advanced LIGO.
The single sub-cavities of the model are individually set in the following ways:
Arm Cavities: resonant for the carrier; non-resonant for the sidebands
Michleson: resonant for the carrier; Schnupp asymmetry of 0.0307 m
PRC: anti-resonant for the carrier; resonant for both sidebands
SRC: resonant for the carrier; resonant for the f2 sideband; non-resonant for f1
In particular, since the model adds no microscopic offset to the SRM position, and the cavity length is set equal to c/f2, the SRC is by default resonant for the carrier. That means that when the arms are locked, the carrier becomes anti-resonant and f2 resonant.
(By adding an optional microscopic offset of lambda/4 the SRC would become resonant for the carrier when the arms are locked. In that case f2 would be anti-resonant. - not desirable)
[attachment:IFOtuning.pdf In this document] I discuss the details behind the choices.
Looptickle
By Stefan Ballmer
The package adds control loops to the Optickle model.
Matlab model of optical cavities
By Alberto Stochino
It is a semi-analythical modeling package. The two building blocks of the models are a Fabry-Perot function and a Michelson function. Each function replaces either a cavity or a Michelson, with an effective compound mirror. The functions return complex reflectance and transmittance. The input parameters are the most generic. The surfaces of all mirrors are treated individually, i.e. reflectance and transmittance can be set independently for each side of a mirror.
Macroscopic length and microscopic offsets are passed to the functions as parameters.
By nesting any combination of cavities in the proper way and order, one can build up a compound mirror representing coupled cavities or the whole interferometer. Then the reflectivity and transmissivity of the compound mirror will be the Bright and Dark port outputs, respectively.
All functions contain a help description on how to use it.