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 . In order to successfully lock a power recycled interferometer with Fabry-Perot arms a technique broadly used is to choose the PRC length such that the sidebands are resonate in PRC. In our design the PRC length has been chosen to let both f1 and f2 sidebands resonate in PRC [#ref1 [1]] [#ref2 [2]].  . In order to successfully lock a power recycled interferometer with Fabry-Perot arms a technique broadly used is to choose the PRC length such that the sidebands are resonate in PRC. In our design the PRC length has been chosen to let both f1 and f2 sidebands resonate in PRC [#ref1 [1]] [#ref2 [2]]. The precision required to get those sidebands resonate is simply depending on the linewidth of PRC for both sidebands.
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 . To measure the length of the recycling cavity,  . There two options to measure the PRC length. One is to use another auxiliary laser and the other is to sweep the modulation frequency.
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[1] [1] " ''Advanced LIGO Length Sensing and Control Final Design'' "[https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=12213 LIGO-T1000298-v2]
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[2] [2] A.Stochino, " '' Design and Characterization of Optical Cavities and Length Sensing and Control System of an Advanced Gravitational Wave Interferometer '' " [https://nodus.ligo.caltech.edu:30889/svn/trunk/alberto/thesis/main/main.pdf 40m svn]
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[3] [3] R.ward, " '' Length Sensing and Control of an Advanced Prototype Interferometric Gravitational Wave Detector'' "[https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=9237 PhD Thesis LIGO-P1000018-v1]

Interferometer Characterization at the 40m prototype

Goals

  • To help the DRMI commissioning that will be performed at LLO.

Motivations

  • In the aLIGO schedule a DRMI test will start on May 2011 at LLO. Prior to the DRMI test we, the 40m lab, should help their commissioning to make the things smooth and hence allow to finish the commissioning in the shortest time. Moreover any commissioning tests that will be performed at LLO should be well predicted and tested at the 40m so that the people at the site can easily pass through all the commissioning tests and possibly can spend time for a real trouble shooting (commissioning) to fix unexpected issues.

  • So for this purpose some recipes must be prepared by the 40m lab. Each recipe includes descriptions about how to make a commissioning test, how to estimate important parameters and the results at the 40m. Additionally some useful scripts must be developed at the 40m.

BR BR

Contents

  1. Interferometer Characterization at the 40m prototype
    1. Goals
    2. Motivations
  2. DRMI Characterization Plan at the 40m
    1. Schnupp asymmetry measurement and its adjustment
      1. Requirement
      2. How to
      3. Results
    2. PRC length measurement and its adjustment
      1. Requirements
      2. How to
      3. Results
    3. SRC length measurement
      1. Requirements
      2. How to
      3. Results
    4. Recycling gain measurements
      1. How to
      2. Results
    5. Beam spot position on BS
      1. Requirements
      2. How to
      3. results
    6. Reflectivity check
      1. How to
      2. Results
    7. Sensing matrix check
      1. How to
      2. Results
    8. Calibration of Actuator responses
      1. How to
      2. Results
    9. f2a filter adjustment
      1. Requirement
      2. How to
      3. Results
    10. IFO modeling
      1. How to
      2. Results
    11. Locking procedure
      1. How to
    12. MICH actuator decoupling
      1. Requirements
      2. How to
  3. References

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DRMI Characterization Plan at the 40m

Schnupp asymmetry measurement and its adjustment

Requirement

  •  Schnupp asymmetry = 0.0342 [m] +/- XXX [mm]

  • The Schnupp asymmetry determines the reflectivity r and transmissivity t of the Michelson for the f1 and f2 sidebands when the carrier is kept in the dark condition. In the design the f2 sideband should be critical coupling in the dual recycling cavity [#ref1 [1]] [#ref2 [2]]. To achieve the critical coupling we should adjust r and t properly.

  • According to a simulation the asymmetry should be within the precision of XXX mm to achieve more than 95 % of the power build up.

How to

  • Here is an instruction how to measure the Schnupp asymmetry.

Results

  • The result at the 40m was ... and the precision was +/- XXX mm. This implies us to fix the length of the asymmetry.

BRBR

PRC length measurement and its adjustment

Requirements

  • {{{ lprc = 6.7538 [m] +/- XXX [mm]

}}}

  • In order to successfully lock a power recycled interferometer with Fabry-Perot arms a technique broadly used is to choose the PRC length such that the sidebands are resonate in PRC. In our design the PRC length has been chosen to let both f1 and f2 sidebands resonate in PRC [#ref1 [1]] [#ref2 [2]]. The precision required to get those sidebands resonate is simply depending on the linewidth of PRC for both sidebands.

How to

  • There two options to measure the PRC length. One is to use another auxiliary laser and the other is to sweep the modulation frequency.

Results

BRBR

SRC length measurement

Requirements

  • {{{ lsrc = 5.39915 [m] +/- XXX mm }}}

How to

Results

BRBR

Recycling gain measurements

  • Since the recycling gain is related to loss in the recycling cavity,...

How to

Results

  •  Carrirer    = XX
 f1 sideband = YY
 f2 sideband = ZZ

BRBR

Beam spot position on BS

Requirements

{{{ off-centering < XXX mm }}}

  • To get a clean AS signal

How to

results

BRBR

Reflectivity check

How to

Results

BRBR

Sensing matrix check

How to

Results

BRBR

Calibration of Actuator responses

How to

Results

BRBR

f2a filter adjustment

Requirement

How to

Results

BRBR

IFO modeling

How to

Results

BRBR

Locking procedure

How to

BRBR

MICH actuator decoupling

Requirements

  • {{{ Precision < 1 % (?)

}}}

  • When the DRMI is locked the MICH control signal is fed back to the BS actuator, but the actuation on BS intrinsically changes the PRC and SRC length as well as the MICH length ( lx-ly). This means the noise from MICH can be transferred to the PRC and SRC, resulting in the degradation of noise performance in the PRC and SRC [#ref3 [3]].

  • To avoid the coupling the MICH control should also actuate on PRM and SRM to minimize the coupling.

How to

BR BR BR BR

References

[1] " Advanced LIGO Length Sensing and Control Final Design "[https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=12213 LIGO-T1000298-v2]

[2] A.Stochino, " Design and Characterization of Optical Cavities and Length Sensing and Control System of an Advanced Gravitational Wave Interferometer " [https://nodus.ligo.caltech.edu:30889/svn/trunk/alberto/thesis/main/main.pdf 40m svn]

[3] R.ward, " Length Sensing and Control of an Advanced Prototype Interferometric Gravitational Wave Detector "[https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=9237 PhD Thesis LIGO-P1000018-v1] BR BR [#plantop back to top]

Interferometer_Characterization (last edited 2012-03-11 03:31:49 by KiwamuizumiATligoDOTorg)