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masahide.tamaki - 21:45 Tuesday 26 July 2022 (21606) Print this report
Power Budget Measurement

[Ushiba, Yasui, Tamaki]

This is a continuation work from yesterday.

Summary

We did power budget measurements with what we had prepared yesterday.
The laser power values at each point are as shown in Fig 1.
The relevant PD and QPD values are also shown in Table 2 (bottom of this report).

Fig1

From this, transmissivities are as below

IFI:  \frac{2.80}{2.98}\simeq0.940
IMMT1:  1-\frac{2.79}{2.80}\simeq0.00358\,\,\,({\rm nominal}:0.003)

PRM:  1-\frac{0.281}{2.79}\simeq0.101\,\,\,({\rm nominal}:0.1) 

As there was VIS work for PR suspensions, we couldn't measure power around REFL, so we will do it tomorrow.

Memo

When I first measured the power after IFI, there was probably a ghost beam hitting the power meter and the value was higher (it was not in the light receiving surface, but the temperature rose because of it, so the value of thermal type power meter became higher).
When we calculated the transmittance, it was strange, so we decided to measure it again and obtained the results shown in the figure above.

Table1

Power Budget
Place Power [W] Background [W]
2.98 ± 0.02 0.01 ± 0.01
2.80 ± 0.02 0.01 ± 0.01
2.79 ± 0.01 0.01 ± 0.01
2.79± 0.01 0.01 ± 0.01
0.281 ± 0.001 -0.007 ± 0.001


Table2

IMC_CAV_TRANS ① 1286.291
MCE_TRANS_QPDA1 ① SEG1 -4306.882
SEG2 -9560.892
SEG3 -9778.571
SEG4 -4534.533
SUM 27980.84
MCE_TRANS_QPDA2 ① SEG1 -4830.760
SEG2 -7353.130
SEG3 -3796.635
SEG4 -2849.884
SUM 18575.48
IMMT1_TRANS_QPDA1 ② SEG1 -10621.50
SEG2 -7424.781
SEG3 -3465.211
SEG4 -3760.238
SUM 25286.44
IMMT1_TRANS_QPDA2 ② SEG1 -11283.93
SEG2 -14074.58
SEG3 -6219.06
SEG4 -5345.05
SUM 36943.94
ASC_POP_FORWARD_QPDA1 ⑤ SEG1 -348.7203
SEG2 -655.4798
SEG3 -240.0567
SEG4 -135.8861
SUM 1380.142
ASC_POP_FORWARD_QPDA2 ⑤ SEG1 -1156.781
SEG2 -55.93481
SEG3 -8.508447
SEG4 -22.90711
SUM 1244.132
Images attached to this report
Comments to this report:
masahide.tamaki - 0:48 Wednesday 27 July 2022 (21611) Print this report

I calculated the relationship between laser power and the QPD (or PD) counts associated with it.
①: IMC_CAV_TRANS, MCE_TRANS_QPDA{1,2}
②: IMMT1_TRANS_QPDA{1,2}
⑤: ASC_POP_FORWARD_QPD{1,2}
* The circled numbers correspond to numbering in klog21606.

This allows us to convert power into counts.

* I used numerical data in klog21594 and klog21606 for my calculations.

Images attached to this comment
tomotada.akutsu - 1:31 Wednesday 27 July 2022 (21612) Print this report

Thank you for the summary. Nicer if revising these calibration plots with various input power. For example, you can remotely vary the input power to IMC by rotating the corresponding HWP in the PSL room without losing the IMC lock (see 21563). So, you can know every QPD/PD read variation for various input power while sitting in the control room.

masahide.tamaki - 8:39 Wednesday 27 July 2022 (21613) Print this report

Thank you for your comment.
I will try it today (maybe) with reference to your klog.

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