Fundamental concept of mortar treatment from Furuta-san,

• Sprayed mortar is fundamentally used as a temporary method until the permanent concrete overlay is applied. Generally, in civil engineering, permanent structures made of mortar are limited to slope protection works. While it is used in slope works with poor conditions, measures are taken to address cracking and delamination.

• I understand that with managed quality and standard construction, it can last about 30 to 50 years. However, I believe the quality control and construction management of the mortar used at the problematic locations were not under conditions that would generally guarantee quality.

 So, this is the reason we never believe the general lifetime of mortar in the KAGRA site. The only method to keep its condition is simply to check the mortar conditions every week.

Actually, even in the XY-arm tunnel where the regular checks have been done, the drop of small-sized mortars was sometimes observed, maybe because of sudden pressure by spring water.

Operation Shift Summary (Aug.29,2025)
Operators name:  Washimi

Shift time: 09-17 JST

Check Items:
VAC: No issues were found.
CRY cooler: No issues were found.
Compressor: No issues were found.
Temp check: (10:00/16:00) temperature change in PSL (due to human works)
VIS GAS filter output check: No issues were found.

IFO state (JST):
09:00 Start of shift, STANDBY remains
17:00 End of shift, STANDBY remains

I increased the current for ITMY IM heater for warming up.

DATE : 2025/08/29 07:50 UTC                                                     
ARM : Y
TEMP ITM : 38.5
TEMP ETM : 113.9
NUM : 10
IFO REFL HWP : 152.0
PSL HWP : 173.0
IMC POWER : 6.0
VALUE : 1233.1
ERROR : 8.9

Measured data is stored to /users/Commissioning/data/Finesse/Yarm/20250829-075004

(Tanaka, Miyakawa)

We finished some remaining work in the PSL room.

• We calibrated the DC PD for the output power monitor of the neoLASE laser.
• Currently, we have set 7A for LD current, and the output is ~28W. It is not the full power, so the mode is not perfectly matched to the PMC, and the transmissivity of PMC is ~78%. The transmitted power of PMC is ~22W.
• We performed the fine alignment procedure for PMC.
• We put beam dumps for transmitted/reflected light from several new/current optics.
• We cleaned up the tools, optics we used in these two weeks.
• We checked the PMC lock, IMC lock, and PLL lock at the last stage before leaving the PSL room.

There are still some remaining work;

• Changing the air-cooled power meter to the water-cooled one.
• We tried to put an iris into the main path to block the ring-shaped scattering light, but the intensity noise got drastically worse, so we removed the iris. There remains some scattering light. We should change some 1-inch optics to 2-inch optics.

We can try the IFO lock next, but one concern is that IMC sometimes becomes unstable to acquire lock. Once IMC is locked, it lasts long.

Date: 2025/08/29

Member: Dan Chen, Misato Onishi

We performed our usual WSK calibration at UToyama.

The results look no problem.

Results

Comparison with Previous Results

Comparing with previous results, no significant issues were found.
Attached graph is the result summary including the latest measured data.

[Kimura and Nakagaki]
 As reported in K-log 34875, the X-27's TMP was switched to air cooling due to a malfunction in the cooling water chiller unit.
However, the switch to air cooling caused a problem with rising temperatures inside the enclosure surrounding the TMP and dry pump.   
 As a countermeasure, part of the enclosure was modified to allow the hot air (approximately 40~50°C) discharged from the dry pump to be vented outside the booth.
As a result, the temperature inside the enclosure decreased from 27.5 ° C to 26.6 °C.
 We plan to maintain this enclosure configuration and continue monitoring the internal temperature.

The TMP and dry pump were not stopped during the implementation of this countermeasure.

DATE : 2025/08/29 00:31 UTC                                                                                    
ARM : X
TEMP ITM : 88.0
TEMP ETM : 104.6
NUM : 10
IFO REFL HWP : 150.0
PSL HWP : 173.0
IMC POWER : 5.0
VALUE : 1358.1
ERROR : 8.7

Measured data is stored to /users/Commissioning/data/Finesse/Xarm/20250829-003133
 

I reduced the current for ETMY IM heater because ETMY temp is now more than 100K.

Sorry, I kept yesterday's log as a draft

Operation Shift Summary (Aug.28,2025)
Operators name:  Washimi

Shift time: 09-17 JST

Check Items:
VAC: No issues were found.
CRY cooler: No issues were found.
Compressor: No issues were found.
Temp check: (10:00/16:00) temperature change in PSL (due to human works)
VIS GAS filter output check: No issues were found.

IFO state (JST):
09:00 Start of shift, STANDBY remains
17:00 End of shift, STANDBY remains

IM Temps of all cryo-payloads.

N2 and O2 components seemed to increase a little bit as Fig.2. Fig.1 shows the temperature inside the EX cryostat.

(Tanaka, Miyakawa)

Finally, we solved the mystery of spot jumps!

They were coming from the heated air generated by Thorlab's power detector. We have ~50W power at the output of the neoLASE box, and ~24W is injected into PMC, and ~25W is discarded into the power meter. Unfortunately or safely, the power meter is air cooled type. If we walk around the optics near the power meter, or even very small convection with no person, it can cause a drastic beam distortion.

We reduced the original power to ~20W, and we rotated the HWP to make all P polarization to avoid sending laser power to the power meter. After waiting until the power meter is cooled down, we looked at the transmitted light, and it became much much less spikes.

Fig.1 shows the situation this morning. Transmitted light (blue) and reflected light (orange) of PMC had many spikes of 5~10% total power several times in 10minutes.

Fig.2 shows that after fixing the heat problem, Transmitted light (blue) and reflected light (orange) have no spikes in 20 minutes. Note that the power calibration is not yet done for refl light, so please ignore the left axis number.

Then we tried the ISS lock, and it worked without any lock loss for at least 40 minutes (we will leave it for tonight).

We still have some remaining work in the PSL room tomorrow. We can try the IFO lock then.

I reduced the current for ETMX IM heater again.

We accepted the SDFs reported on klog 34946

KAGRA Pcal-Y updates (2025/08/28)

Workers: Dan Chen, Misato Onishi

We performed monthly Pcal-Y calibration on 2025/08/28.

After the calibration, we updated EPICS parameters related to the Pcal-Y system. No issues were found.

Astract:

BS was oscilated in yaw, so I measured TF for investigating the reason of the oscillation.
TF doesn't seem strange though some gain difference can be observed.
Also, I requested LOCK_ACQUISITION state to BS today, oscillation soesn't seem to be reproduced.
So, I keep BS at LOCK_ACQUISITION state to monitor it.

Detail:

Yokozawa-san found that BS yaw was oscillating at LOCK_ACQUISITION state on Monday (fig1).
Then, I and Takahashi-san checked what is the reason of this oscillation on Tuesday.

We first checked the signals when BS at ALIGNED state and confirmed that there seems no oscillation.
So, the oscillation comes from the difference between ALIGNED state and LCOK_ACQUISITION state.

The main difference between these states are as follows:
1. Inertial damping control of IP
2. Sensor correction of IP and F0
3. Dewhitening filter setting
4. TML damping control

We manually changed the control setting one by one and confirmed that 2, 3, and 4 didn't cause the oscillation while 1 causes the oscillation.
So, the issue seems to come from inertial damping control.

To investigate what happens in inertial damping control, I measured TF of IP{L,T,Y} today (fig2-4).
Though no large difference can be seen, the relative gain of geophone and LVDT in L and T DoFs seems changed by about 1dB (fig5,6) while yaw seems less than 0.1dB (fig7).

After that, I requested LCOK_ACQUISITION state for BS and wait for a while but somehow oscillation did not happen, this is a mistery.
So, I keep BS at LOCK_ACQUISITION state to see if theoscillation happens again or not.