I've pushed an MCMC simulation to the A+ BHD repo (filename MCMC_TFs.ipynb). The idea is to show how random offsets around ideal IFO change the noise couplings of different DOFs to readout.
At each step of the simulation:
1. Random offsets for the different DOFs are generated from a normal distribution. The RMSs are taken from experimental data and some guesses and can be changed later. The laser frequency is tuned to match the CARM offset.
These are the current RMS detunings I use:
| DOF |
RMS |
Taken from |
| DARM |
10fm |
PHYSICAL REVIEW D 93, 112004 (2016), Table 2 |
| CARM |
1fm |
PHYSICAL REVIEW D 93, 112004 (2016), Table 2 |
| MICH |
3pm |
PHYSICAL REVIEW D 93, 112004 (2016), Table 2 |
| PRCL |
1pm |
PHYSICAL REVIEW D 93, 112004 (2016), Table 2 |
| SRCL |
10pm |
PHYSICAL REVIEW D 93, 112004 (2016), Table 2 |
| OMCL |
0.1pm |
Guess |
| OMC Breadboard angle |
1\mu rad |
Guess |
| Differential arm loss |
15ppm |
Guess |
| BHD BS imbalance |
10% |
Guess |
| OMC finesse imbalance |
5ppm |
Guess |
2. A transfer function is computed for the noisy DOFs.
3. Projected noise is calculated.
These are the noise level for the DOFs:
| DOF |
Noise |
Taken from |
| MICH |
2e-16 m |
PHYSICAL REVIEW D 93, 112004 (2016), Fig 9 |
| PRCL |
0.5e-17 m |
PHYSICAL REVIEW D 93, 112004 (2016), Fig 9 |
| SRCL |
5e-16 |
PHYSICAL REVIEW D 93, 112004 (2016), Fig 9 |
| OMCL |
2.5e-17*(100/f)^(1/2) |
LIGO-G1800149 |
| OMC Breadboard angle |
1nrad |
Guess |
| RIN |
2e-9 |
Optics Letters Vol. 34, Issue 19, pp. 2912-2914 (2009) |
The attachments show the projected noise levels for the noisy DOFs. Each curve is a different instance of random offsets. The ideal case - "zero offsets" is also shown.
OMC Comm and OMC diff refer to the common and differential length change of the OMCs. |