KAGRA Logbook

CAL (XPcal)

Kohei Mitsuhashi - 21:09 Tuesday 24 December 2024 (32118)

XPcal calibration

[Dan-san, Mitsuhashi]

What we did

We did the integrating sphere calibration for XPcal.
The results are attached. PDF file is made by Hido-san.

Note

This is the first calibration of WSK and integrating spheres of XPcal since WSK broke down on 2024 December 11(A calibration of WSK and GSK has already done).
The WSK used in this calibration is new, so the experimental results cannot be directly compared with previous data.
Related klog: https://klog.icrr.u-tokyo.ac.jp/osl/?r=31960
Related cal wiki: https://dac.icrr.u-tokyo.ac.jp/KAGRA/DAWG/CAL/O4_meas_date/UToyama_241211

Non-image files attached to this report

result_summary.pdf

Comments to this report:

takahiro.yamamoto - 20:51 Wednesday 25 December 2024 (32131)

For comparing latest results with past ones, I computed a calibration factor from GSK to each PD.

Latest measurements
Latest results of integration sphere calibration are available in the attached file of klog#32118.
According to this file, a calibration factor from WSK to each PD is as follows.
RxPD1_WSK = 0.156746 +/- 0.000067 RxPD2_WSK = 0.155860 +/- 0.000053 TxPD1_WSK = 0.443911 +/- 0.000019 TxPD2_WSK = 0.603179 +/- 0.000025

A calibration factor from GSK to WSK is available in wiki post on Dec.11.
In this wiki post, there is no representative value of a calibration factor but there are 4 repeated measurement results with errors.
So I used weighted average of these 4 measurements as a representative value of the calibration factor from GSK to WSK.
WSK_GSK = 0.90768 +/- 0.00032

A calibration factor from GSK to each PD can be computed as a product of one from GSK to WSK and one from WSK to each PD and results are as follows.
RxPD1_GSK = 0.142275 +/- 0.000079 (+/- 0.056%) RxPD2_GSK = 0.141471 +/- 0.000069 (+/- 0.049%) TxPD1_GSK = 0.40293 +/- 0.00014 (+/- 0.036%) TxPD2_GSK = 0.54749 +/- 0.00020 (+/- 0.036%)

Previous measurements
Same results measured before the trouble on WSK are available in klog#31697 (WSK -> each PD) and in klog#30199 (GSK -> WSK).
RxPD1_WSK = 1.01099 +- 0.00028 RxPD2_WSK = 1.00658 +- 0.00034 TxPD1_WSK = 2.84929 +- 0.00030 TxPD2_WSK = 3.88791 +- 0.00037 WSK_GSK = 0.14024 +/- 0.00013

Then, we obtained a calibration factor from GSK to each PD before the trouble with the same manner as above.
RxPD1_GSK = 0.14178 +/- 0.00014 (+/- 0.097%) RxPD2_GSK = 0.14116 +/- 0.00014 (+/- 0.099%) TxPD1_GSK = 0.39958 +/- 0.00037 (+/- 0.093%) TxPD2_GSK = 0.54524 +/- 0.00051 (+/- 0.093%)

Before and After
Changes in the calibration factor from GSK to each PD before and after the trouble are as follows
RxPD1_GSK: +0.35% RxPD2_GSK: +0.22% TxPD1_GSK: +0.84% TxPD2_GSK: +0.41%.

These changes are quite larger than the error of each measurement.
I have not checked how much time variation (time drift in months) is typical of past measurements.
A next step is to check these changes can be regarded as a time variation or comes from some kind of systematic changes of instruments.

takahiro.yamamoto - 18:46 Thursday 26 December 2024 (32159)

According to the discussion with Hido-kun, measurement results doesn't contains the error coming from the relative position between incident beam and integration sphere, and also it's larger than a statistical error in each measurement.

Uncertainty of relative position in each measurement in Sec. 6.1 of JGW-P2415539 is ~0.33% for RxPD and ~0.26% for TxPD (For TxPD calibration we need to move only WSK and TxPD isn't moved. This is the reason why the position uncertainty of RxPD becomes larger than one of TxPD). If we assume that WSK calibration has similar uncertainty with RxPD case (When WSK is calibrated by using GSK, both WSK and GSK are moved.), a calibration factor of GSK to each PD has relative uncertainty among measurements on another days are ~0.47% for RxPD and ~0.42% for TxPD.

So the change in the calibration factor from GSK to each PD measured in this month and last month is within relative uncertainty of each measurement and we can conclude that there is no significant change before and after the trouble on WSK for the current precision of the integration sphere calibration.