[Haba, Komori, Ushiba]
Abstract:
We measured IR power at several places on TMSY and measured ADC cnts of PD and QPDs at that time.
Detail:
After putting a green filter (klog22458), we measured IR beam power at several places on TMSY optical table.
Measurement results are as follows (optical layout of TMSY can be seen here):
1. In front of RLNS2 (just after the green filter): 480uW +- 10uW (background: 0.73 +- 0.02 uW)
2. In front of RPD1: 52.5 +- 0.5 uW (background: -0.26 +- 0.01 uW)
3. In front of RQPD1: 116 +- 1 uW (background: 0.15 +- 0.00 uW)
4. In front of RQPD2: 118 +- 1 uW (background: 0.53 +- 0.00 uW)
We also measured PD and QPD cnts at each segments when IR was locked.
Following tables are results.
| IR locked | Background | |
| PDA1 | 272.38 | 17.89 |
| QPDA1 SEG1 | -680.33 | -29.98 |
| QPDA1 SEG2 | -647.87 | -30.09 |
| QPDA1 SEG3 | -643.04 | -29.07 |
| QPDA1 SEG4 | -763.46 | -29.89 |
| QPDA2 SEG1 | -581.50 | -26.75 |
| QPDA2 SEG2 | -856.75 | -28.08 |
| QPDA2 SEG3 | -608.52 | -26.27 |
| QPDA2 SEG4 | -816.47 | -26.94 |
Then, I set offset for background subtruction of QPD segments according to the measurement results.
Note:
In front of PDA1, there is a mirror for reducing IR power on PD (I don't know how much power was thorown away).
Between RST3and RBS2, there was a mirror for reducing laser power on QPDs but it was removed during the work because IR power on QPD is too small.
After removing the mirror at QPD path, I changed the QPD gain to low gain mode for avoid saturation of QPD signals.