sheila.dwyer@LIGO.ORG - posted 15:47, Monday 17 March 2025 - last comment - 16:12, Monday 17 March 2025(83415)
POP power measurements repeat
Sheila, Elenna
This morning while we were relocking I did a repeat of the POP air power measurements with 2W input power into the IFO, similar to what was done in 82942, this time the powers are rather different and are closer to expectations for HAM1 powers (with settings on the power meter verified).
- See photo of this path: 82751 After the 90/10 BS I measured 1.6mW, right before POP X I measured 0.83mW, and 0.22mW on the pop AIR B path. (I am sure that the power meter was set correctly for the wavelength and filter state).
- The attached screenshot shows a time series of when I was making measurements, you can tell which measurement happened when by looking at the time each beam was blocked.
- POP_A_LF is calibrated into uW on the POP in vac diode 13905 (1055uW at this time), while POP_A_LP is calibrated into Watts in the PRC based on input power, PRG (82656).
Implied power in the PRC at 2W input power time:
- input power 1.86W * PRG of 53 = 98.6W
- power meter in popair path = 1.6mW *(1/ 0.1)*(1/(1-0.054))*(1/229e-6) = 73.9 W
- power on POP A LF = 1054uW*(1 /0.054)*(1/229e-6) = 85.2W
| power measured |
counts before any calibration is applied (INMON) |
what I think this diode's calibration should be | currently calibrated value of this diode | |
| after 90/10 BS | 1.6mW | |||
| before POP X (POP X SUM) | 0.83mW | 940 | 0.88 uW/ count | no calibration applied |
| before POPAIR B | 0.22mW | 141 | 1.56uW/count | no calibration applied |
| POPAIR A diode | 0.22mW infered from POPAIR B meas | 10.9 | 20uW/count | 55uW |
| POP in vac diode | 260 | 1054uW |
Images attached to this report
Comments related to this report
With regards to the upcoming HAM1 vent and placement of an in-vac POP WFS, I think these results indicate that we can have ~30 mW of power on the in-vac POP WFS. At 2 W of input power, Sheila measured 0.8 mW on the POPX WFS. At 60 W input, there should be about 24 mW on the POPX WFS.
Daniel made a similar conclusion here.