[Tanaka,Saito]

Based on the optical layout plan in klog:36739, we installed a newly purchased FI, a beam sampler, and mirrors. The transmission of the FI reached approximately 85%.

• We replaced the contaminated FI reported in klog:36739 with a newly purchased one (Photo 1). This FI has an aperture of 3 mm. Since the laser beam radius at the planned position in the optical layout is about 1.2 mm, we placed the HWP, PBS, and mirrors upstream of the FI as close together as possible, reducing the beam radius at the FI position to approximately 0.8 mm. After alignment, the input power was about 154 mW and the output power was about 131 mW, corresponding to a transmission of approximately 85%. A beam sampler with a reflection-to-transmission ratio of 9:1 was installed after the FI. Six mirrors were placed on the reflection side of the beam sampler.

Unfortunately, since the right-side wall shown in Photo 1 cannot be removed, it is difficult to install an additional mirror and perform alignment.

I checked the geophone performance by FLDACC status. Plot 1 shows the spectra of the geophones in the SAFE state, where the FLDACCs were not locked but were free-running under DC actuation to the proof mass. Plot 2 shows the spectra of the geophones in the READY state, where the FLDACCs were locked in ~20Hz UGF. In this case, the geophone spectra have been smeared by the FLDACC's activity.

[Kimura, Yasui and M. Takahashi]

 The duct shield cryocoolers (Yea, Yer) and the cooling water circulation system at Y-end were shut down at 9:00 a.m. to perform repairs on the Y-end feedwater pump.
Since the repairs on the feedwater pump were completed, the duct shield cryocoolers (Yea, Yer) and the cooling water circulation system were restarted at 1:30 p.m.

While the cooling water circulation system was shut down, the SLACK alarm was temporarily disabled.

I monitored the suspension during the evacuation, which started at 13:10. The suspension state was SAFE. The valve opening looks very small until 13:25. About one hour later, the IP drifted by ~1mm (Pic. 1) and the BF GAS drifted by ~0.15mm (Pic. 2). I changed the suspension state to ISOLATED at 14:25. The pressure was 6x10^3 Pa. The DC feedback signals to lock the FLDACCs were almost the same as the previous: 12100 for H1, 11500 for H2, and -5200 for H3. I offloaded the IP H1 and H2 with the FRs.

This is a retry of klog#36416 which hadn't been completed.

For the hardware replacement of CC-10 readout for SRMGV and OMMTGV from RaspPi to MOXA (klog#36737), I stopped vacuum DAQ and resumed it with a new channel list. All migration works on DGS (disabled to access RaspPi@AS which is no longer used, updated MEDM screens, update a watch list by vacuum guardian, and updated a channel list of KAGRA DAQ) was completed. At the end of this work, daqd was restarted.

I heard from Nakagaki-san that some hardware settings still remain. Because of this, new values haven't been written in some channels used for an alert by guardian by the new MOXA system though they exist. So an alert about pressure values at SRMGV and OMMTGV, and status of gate valve at OMMT are still disabled as shown in Fig.1 due to avoid annoying and meaningless alerts. They should be automatically enabled when pressure values will become smaller than threshold and gate valve will be opened.

I checked the TM transfer functions after closing the chamber. They were consistent with the references.

[Tanaka,Saito]

To resolve the issue of an excessively large beam size identified in klog:36731, we recalculated the positions of two lenses for mode matching.
The large loss in the FI reported in klog:36731 was caused by misalignment of the output polarization and contamination inside the FI.
 

• To resolve the issue of an excessively large beam size identified in klog:36731, we recalculated the positions of two lenses for mode matching (Fig. 1). The origin is defined as the point where the laser is emitted. The orange line represents the beam profile of the laser, the green line represents the beam profile after passing through the first lens, the red line represents the beam profile after passing through the second lens, and the blue line represents the target beam profile of the IR laser on the POS optical table.

  The focal lengths and positions of the two lenses are as follows:

  Lens 1: focal length = 200 mm, position = 2794 mm
  Lens 2: focal length = 150 mm, position = 3190 mm

  The beam size at these lens positions is acceptable when using 2-inch lenses. Based on the calculated lens positions, we redesigned the optical layout for PRCL and SRCL measurements (Fig. 2).
   

• Although the FI exhibited large losses in klog:36731, aligning the output polarization improved the transmitted power: the input power was approximately 27 mW, while the output power increased to about 20 mW, corresponding to a transmission of 74%. However, since no further improvement was observed, we inspected the interior of the FI by illumination and found contamination (Photo 1). Therefore, we decided to use a newly purchased FI instead.

I checked the IM transfer functions after closing the chamber. The DC gain of the H1 and L transfer functions was increased by 3dB due to the replacement of the satellite box.

[YamaT, Kimura, Yasui, TakahashiM, SawadaH, Nakagaki]

We switched the remote monitoring system for the two CC-10 vacuum gauges (PV names K1:VAC-PRESSURE-CS-SRMGV and K1:VAC-PRESSURE-CS-OMMTGV) that will be used by the GV auto-closure device from Raspberry Pi to MOXA.

I checked the GAS transfer functions after closing the chamber. They were consistent with the references.

I checked the IP transfer functions after closing the chamber.  The resonant frequencies of the IP were increased from 63 to 66 mHz for L, from 70 to 74 mHz for T, and from 0.32 to 0.33 Hz for Y, respectively. Diagonization should be retuned.

I turned ON the laser of Pcal-Y and requested the Pcal-Y guardian to be low power state, which was turned OFF duo to the DGS maintenance last weeks.

[Tanaka,Hirose,Saito]

In accordance with the optical layout plan in klog:36730, we installed the sub-laser, HWP, PBS, and FI.
We found that the beam size at the position of the second lens was too large, so we decided to reconsider the optical layout.
 

• Following the optical layout plan in klog:36730, we installed the sub-laser, HWP, PBS, and FI (Photo 1). From right to left in Photo 1, these are the sub-laser, HWP, PBS, HWP, and FI. Using the first HWP and PBS, we constructed the optical layout with reduced laser power. The laser power will be increased during the measurements of PRCL and SRCL. Although the HWP placed in front of the FI was not included in the original optical layout plan, it was installed to match the polarization to the FI. The FI was adjusted to maximize the transmitted power; however, the power decreased significantly from approximately 27 mW before the FI to approximately 1.8 mW after the FI. Since we had not confirmed whether the laser beam was properly aligned before placing the optical components, we plan to check the beam alignment.
   
• In the calculation of the positions of the two lenses for mode matching in klog:36730, the beam radius at the position of the second lens was found to be 10.7 mm, indicating that the beam size is too large for a 1-inch (25.4 mm) lens. Therefore, we plan to recalculate the positions of the two lenses for mode matching.

[Tanaka,Hirose,Saito]

Abstract:

We fitted the beam profile of the IR laser on the POS optical table measured in klog: 36724. The waist position was found to be 259 mm, and the waist size was 0.054 mm. Based on these results and the fitted beam profile of the sub-laser, we calculated the positions of two lenses required for mode matching. Furthermore, we developed an optical layout plan for the measurements of PRCL and SRCL.

Detail:

First, we fitted the beam profile of the IR laser on the POS optical table measured in klog: 36724 (Fig.1). The points represent the measurement results, and the lines represent the fitting results. The green and orange points were used for the fitting, while the blue and red points were excluded because their behavior differed from the other measurement points.

The measurement points around 300 mm deviate significantly from the fitting curve because, as shown in Photo 2 of klog: 36724, the beam split into two, and both spots were simultaneously fitted with a Gaussian. The apparently reasonable behavior around 350 mm is because only one of the split beams was successfully fitted with a Gaussian. However, since the beam was distorted as shown in Photo 3 of klog:36724, it should have been compared with the beam between 100 mm and 250 mm to determine whether to include it in the fitting; unfortunately, no photos were taken in that range. In addition, when the mesurement points around 350 mm are included in the fitting (Fig.2), the mesurement points between 100 mm and 250 mm deviate from the fitting curve compared to Fig.1. Therefore, we decided to use the results from Fig.1 to determine the positions of the two lenses for mode matching. (For the measurements of PRCL and SRCL, it is sufficient to observe the resonance of the TEM00 mode, so a slight mismatch in mode matching is considered acceptable.)

The waist position and waist size obtained from the fitting in Fig.1 are as follows:

Major : waist position = 264.3 ± 5.1 mm, waist size = 0.0526 ± 0.0025 mm
Minor : waist position = 253.6 ± 2.3 mm, waist size = 0.0555 ± 0.0013 mm
→ Average: waist position = 259 mm, waist size = 0.054 mm

The laser to be newly installed on the POS optical table must be mode-matched to this waist position and size. Therefore, its beam profile was measured in advance in Kashiwa and fitted (Fig.3). The origin is defined as the point where the laser is emitted.

The waist position and waist size obtained from the fitting in Fig.3 are as follows:

Major : waist position = −118.8 ± 1.9 mm, waist size = 0.1469 ± 0.0008 mm
Minor : waist position = −127.8 ± 1.8 mm, waist size = 0.1562 ± 0.0008 mm
→ Average: waist position = −123 mm, waist size = 0.1516 mm

Next, based on these waist positions and waist sizes, we determined the positions of two lenses for mode matching (Fig.4). The origin is defined as the point where the laser is emitted. The orange line represents the beam profile of the laser, the green line represents the beam profile after passing through the first lens, the red line represents the beam profile after passing through the second lens, and the blue line represents the target beam profile of the infrared laser on the POS optical table. 

The focal lengths and positions of the two lenses are as follows:

Lens 1: focal length = 200 mm, position = 1426 mm
Lens 2: focal length = 500 mm, position = 2363 mm

Finally, based on the calculated lens positions, we designed an optical layout for a phase-locked loop (PLL) used in the measurements of PRCL and SRCL (Fig.5). The right-hand side of Fig.5 corresponds to the optical system designed in this work.

[Washimi, Takahashi]

We replaced the satellite box for the IM H OSEMs. The previous box is  S1604901 (Pic. 1 and 2). The new box is  S1807635 (Pic. 3 and 4). The OSEM outputs were changed as follows (Pic. 5). The transfer functions for H2 (Pic. 7), H3 (Pic. 8), and Y (Pic. 10) were the same as the previous measurements. The DC gain of the transfer functions for H1 (Pic. 6) and L (Pic. 9) was increased by 5dB. The H1 OFFSET in "K1 SRM IM OSEMINF FILTERS" was returned from -3700 to -6315.5.

I added the F0 transfer function measured with a modified template.

I checked the transfer functions of F1, BF, IM, and TM. The states during the measurement were READY for F1 and BF, TWR_FLOAT for IM and TM. The diaggui for F0 did not work.