Below we report some of the activities performed this morning.
1/ Part 1 : OMC polarization tuning (BS+NI aligned)
As mentioned in entry 50444, when the OMC temperature is around 23°c, the P-polarization peak is partially overlapped with the 6MHz LSB (Fig.1). We checked the influence of the OMC temperature working point on the position of this P-polarization peak.
At 24 deg (Fig.2) the P-polarization peak is moving to the opposite side of the LSB 6 MHz (getting farther from the carrier S-polarization peak).
Then we lowered the OMC temperature working point at 22 deg. In this case the P-polarization peak is moving closer to the S-polarization peak, and do not overlap any more with the LSB 6 MHz (Fig.3). Therefore this seems to be a good working point. In the future we need to keep the OMC working point around 22 deg.
While the OMC was at 23 deg, we switched off the 6 MHz modulation depth in order to evaluate the residual polarization mismatch (Fig.4). To this purpose the RFC was locked using the 56 MHz SB. When we substract the tail of the carrier resonance, the height of the P-polarisation peak is about 0.005 mW on the PD3 photodiode and 0.02 mW on the PD1 photodiode. The S-polarization peak is about 0.6 mW on PD3, which corresponds to 30 mW on PD1. Thus the polarization mismatch is about : 0.02/0.6 = 0.07 %.
2/ Photodiodes configuration updates:
- Offsets of the B1 PD1/2/3 photodiodes have been corrected.
- The definition of B1_DC has been changed. This channel nows correspond to the sum of B1_PD1_DC and B1_PD2_DC. The SDB2_Photodiodes configuration file has been updated accordingly.
- The gains of the DC and Audio channels of the B4_PD1 and PD2 photodiodes have been corrected in order to take into account the new preamplifiers (80 mA). The offsets of the photodiodes have been corrected.
3/ SIB2 alignment (PR aligned):
The centering of the B2 beam on the B2_PD1/2/3 photodiodes has been checked. During this activity we noticed that a few picomotors were not correctly assigned. This concerns the B2_M4V, B2_M4H, B2_M5bV picomotors. This has been fixed.
The alignement of the B2 quadrants still remains to be adjusted.
