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CAL (Pcal general)
Kohei Mitsuhashi - 13:32 Tuesday 10 December 2024 (31960) Print this report
WSK's circuit or PD seems to be broken

Why it is broken


When we attached DC supply to External Power port of Pcal PD satellite BOX (in attached picture), it was attached upside down. This Box is connected to WSK to supply DC and to measure a read-out Voltage of WSK.
Usually, +18 V is supplied to PD preamp of WSK, but ion this time -18V was supplied.

How to know it is broken


The read-out voltage of WSK showed around 10V without injecting lazer.
Images attached to this report
Comments to this report:
dan.chen - 16:47 Tuesday 10 December 2024 (31961) Print this report

With Hido-san, Mitsuhashi-san,

Summary

  • We replaced the PD and the pre-amp circuit of WSK which was broken this morning by the PD and pre-amp circuit of WST.
  • The output from WSK seems normal, no problem.
  • When we injected a laser power roughly same as that during a past calibration measurement, the WSK output is "similar" to the past. (about 20% change.)
    • The point is that because we changed WSK, we must calibrate WSK by GSK, then use the new calibration factor to calibrate the Pcal PDs in KAGRA.

Details

  • We checked the pre-amp circuit.
    • WSK original one:
      • D number: D1300210-v4
      • R7: 202 = 2k Ohm
      • R8: 2001 = 2k Ohm
    • WST original one:
      • D number: JGW-D2214419
      • R7: 2001 = 2k Ohm
      • R8: 1302 = 13k Ohm
    • So, the trans-impeadance is same each pther.
  • We installed the WST circuit with the PD to the WSK.
  • We connected the cable on the renewed WSK.
  • Checked the output from the WSK, then it was about 0V.
    • When we inject a flashlight, it has a small strange oscillation with about 10mV? amp.
  • Then we injected the laser with the power that we usually use for the calibration.
    • The position of the WSK is trans, which means formation B.
    • The OFS offset is 0.504V.
    • The output from renewed WSK is 0.450V.
      • This value was about 0.55V when we performed the calibration.
    • The output from GSK is -0.570V. (-0.59V during the last calibration.)
  • We injected a sin wave with a function generator.
    • No strange point was observed.
  • We will perform a GSK-WSK calibration tomorrow.
Kohei Mitsuhashi - 22:39 Thursday 12 December 2024 (31987) Print this report
Dan, Hido, Mitsuhashi

Summary


・A new WSK's pre-amp circuit works properly.
・Read out voltage from a new WSK is not contradictory.

Detail


According to previous comments, the new WSK pre-amp circuit (D number: D2214419) installed in the WST circuit was reported to have approximately six times higher gain compared to the broken previous WSK pre-amp circuit (D number: D1300210-v4). However, when the lazer was injected with power that we usually use for the calibration, the new WSK showed around 0.50 V, whereas the previous WSK showed around 0.54 V based on historical experimental data, resulting in a contradictory outcome. On the other hand, the voltages from the GSK were approximately around -0.64 V and around -0.59 V, respectively.

This contradiction was incorrectly reported. The reason is that the value referenced as historical experimental data of the previous WSK actually belonged to the WST. Upon rechecking the historical experimental data of the previous WSK, it was confirmed to be around 0.08 V, which explains the difference properly in gain between the pre-amp circuits. At that time, GSK showed around 0.61V.

The reported voltages correspond to Formation A, where the front device is the GSK, and the back device is the WSK. Importantly, this trend remains consistent regardless of whether the front device is the WSK and the back device is the GSK, or if Formation B is employed instead at least the three calibrations since November.

Additional finding


In JGW-D2214419, the electricity schematic, R7 is 20.0k Ohm. But in the new WSK pre-amp circuit using D2214419, R7 is 2K Ohm.
Kohei Mitsuhashi - 17:17 Thursday 26 December 2024 (32155) Print this report
with Dan-san, with Onish-san

Summary


・We did a calibration of WSK to GSK @ Univ.Toyama.
Result wiki : https://dac.icrr.u-tokyo.ac.jp/KAGRA/DAWG/CAL/O4_meas_date/UToyama_241226

・A results is around 0.1% difference from the previous WSK calibration. This difference doesn't make matter.

Detail


Today we did the calibration of WSK. Before this, we did a calibration of XPcal's and YPcal's integrating spheres to WSK, and we also did a calibration of WSK to GSK. Related klogs and wiki are as followed.
XPcal : https://klog.icrr.u-tokyo.ac.jp/osl/?r=32118
YPcal : https://klog.icrr.u-tokyo.ac.jp/osl/?r=32128

The previous WSK to GSK :https://dac.icrr.u-tokyo.ac.jp/KAGRA/DAWG/CAL/O4_meas_date/UToyama_241211

0.1% difference is there in results between the previous WSK calibration and this WSK calibration.
This difference doesn't make matter.
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