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.
Contents
- Interferometer Characterization at the 40m prototype
-
DRMI Characterization Plan at the 40m
- Schnupp asymmetry measurement and its adjustment
- PRC length measurement and its adjustment
- SRC length measurement
- Recycling gain measurements
- Beam spot position on BS
- Reflectivity check
- Sensing matrix check
- Calibration of Actuator responses
- f2a filter adjustment
- IFO modeling
- Locking procedure
- MICH actuator decoupling
- References
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 . 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.
PRC length measurement and its adjustment
Requirements
- {{{ lprc = 6.7538 [m] +/- XXX [mm]
}}}
- In order to resonate both f1 and f2 sidebands the length should be adjusted to ..
- In addition to that the arm makes the non-zero phase shift on these sidebands and makes the ..
How to
- To measure the length of the recycling cavity,
Results
SRC length measurement
Requirements
- {{{ lsrc = 5.39915 [m] +/- XXX mm }}}
How to
Results
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
Beam spot position on BS
Requirements
{{{ off-centering < XXX mm }}}
- To get a clean AS signal
How to
results
Reflectivity check
How to
Results
Sensing matrix check
How to
Results
Calibration of Actuator responses
How to
Results
f2a filter adjustment
Requirement
How to
Results
IFO modeling
How to
Results
Locking procedure
How to
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 [#ref2 [2]].
- To avoid the coupling the MICH control should also actuate on PRM and SRM to minimize the coupling.
How to
References
[1] [2] [#plantop back to top]