KAGRA Logbook

CAL (XPcal)

dan.chen - 16:27 Monday 01 May 2023 (25062)

XPcal guardian parameter fix and TF measurements

Date: 2023/5/1

With Shingo Fujii

First, we determined the parameters for the guardian so that the XPcal guardian could be used.
Now the guardian can be used. If you find any point does not work well, please let me know.

Then, we measured OLTFs and TF from injection point(=CLTF) to PDs like TxPD.
Basically, they worked as they were supposed to.
Finally, measurements were made when large injections were input, but at high frequencies (above 10 kHz), the laser power was not able to keep up. (I don't think we'd put a pcal line in at such a high frequency.)

(We did not run the scripts to estimate the separate ratio proms, etc because we afraid it would interfere with other interferometer works.)

Images attached to this report

25062_1682925864_001_FRF_-_-_CH1-2_Graph1_NC-OLTF-Path1.png

25062_1682925864_002_FRF_-_-_CH1-2_Graph1_NC-OLTF-Path2.png

25062_1682925864_006_FRF_-_-_CH1-2_Graph1_NC-Path1-CLTF-to-OFS.png

25062_1682925864_007_FRF_-_-_CH1-3_Graph1_NC-Path1-CLTF-to-Tx.png

25062_1682925864_008_FRF_-_-_CH1-4_Graph1_NC-Path1-CLTF-to-Rx.png

25062_1682925864_009_FRF_-_-_CH1-2_Graph1_NC-Path2-CLTF-to-OFS.png

25062_1682925864_010_FRF_-_-_CH1-3_Graph1_NC-Path2-CLTF-to-Tx.png

25062_1682925864_011_FRF_-_-_CH1-4_Graph1_NC-Path2-CLTF-to-Rx.png

25062_1682925864_020_FRF_-_-_CH1-3_Graph1_NC-1p5Vinj-Path1-CLTF-to-OTx.png

Comments to this report:

dan.chen - 10:53 Tuesday 02 May 2023 (25079)

We performed the power balance estimation and updated parameters such as K1:CAL-PCAL_EX_1_RX_V_R_SET.

Images attached to this comment

dan.chen - 16:21 Tuesday 02 May 2023 (25084)

Detailed report: link

takahiro.yamamoto - 18:55 Tuesday 02 May 2023 (25086)

> Finally, measurements were made when large injections were input, but at high frequencies (above 10 kHz), the laser power was not able to keep up.
It was probably that a voltage at VGA output reached 15V.

Figure 1 and 2 show transfer functions of open loop and closed loop, respectively.
At this time, I assumed that 39dB gain at VGA.
This corresponds to the 5.0V output from DAC (= 12.0dB + 49.9dB/V * 5.0V / 11.0V/V + 4.4dB).

They seem to be well match with measured TFs for this discussion.
So I prepared a transfer function model from from injection point named as "CLTF" to the output of VGA
in the case that OFS loop is closed based on the OLTF model.
As shown in Fig. 3, TF from "CLTF" to the output of VGA has more than 10dB gain around 10kHz.
Assuming 1.5V injection from "CLTF" with the case of Fig.3, a voltage at VGA output reaches 15V around 13kHz as shown in Fig.4.

Images attached to this comment