Today afternoon, around 13h UTC we started the procedure to decrease the power towards the ITF. The power was lowered from 18W on the IMC transmission to 12 W. We followed the steps described below:
- We measured the TF of the IMC. The UGF was 110 kHz and the phase margin was 23 degrees;
- We moved the IPC1 and IPC8 rotators to adjust the power of the tranmission and reflection of IMC, respectively. The overall steps are summarized below:
- cm_send('EIBAgilisRot','MOVEREL', 1, 1, 10600, 50) #IPC1
- cm_send('EIBAgilisRot','MOVEREL', 4, 1, 3500, 50) #IPC8
- We changed the thresholds of some INJ signals:
- RFC threshold: from 2.2 mW to 1.5 mW (MCMir DSP card);
- IMC threshold: from 18 W to 12 W (IBMar DSP card) and also changed the variables 'LOCK' and 'IMC_trigger' on the VPM ISYS_Acl (lines 231 and 235);
- FmodErr Z_Calib: from -5e-9 to -1e-8 (on metatron)
- Then, we engaged all loops and everything locked again.
- Finally, we remeasured the TF of the IMC (see Fig. 1). The UGF is now 93 kHz and 26 degrees of phase margin.
- Fig. 2 shows the FFT of the main INJ signals and no significant difference can be seen.
To be noted that we didn't change the B2 signal, which now is 8.5 mW instead of 12.2 mW.
