This is a summary of the Guardian modifications described in klog 37812.

1. Changes to the Guardian paths

• The original path between DOWN and LOCK_PREP_FOR_OBSERVATION has been disconnected. This path was previously used for the transition from DOWN to PRMI_3F_LOCKED. The observation path in the VERTEX Guardian will be modified for DRMI locking in the future. The settings in the DOWN state have not been changed. The parameters used for PRMI 1f/3f locking are reset in the DOWN state. PRMI_3F_LOCKED can now be reached from LOCKING_PRMI, which is on the path DOWN → LOCKING_PRMI → PRMI_1F_LOCKED. The settings in LOCKING_PRMI are now selected depending on whether PRMI 1f or 3f locking is requested.

2. Changes to each state

[PREP_FM_FOR_PRMI]

• [Demodulation phases] The demodulation phases are set separately for PRMI 1f and 3f locking. For each degree of freedom, the demodulation phase was optimized so that the signal appears mainly in either the I or Q phase. Previously, the demodulation phases were adjusted for MICH and PRX 1f/3f locking. This time, the phases were re-optimized under PRMI locking conditions, and the values were updated accordingly.
• [Output matrix] The OUTMTRX coefficient was set to -0.0404 to send the MICH feedback signal to BS and PRM. The same coefficient is used for both PRMI 1f and 3f locking.

• [HWP setting] During PRMI 3f locking, the REFL optical power was too high. Therefore, the HWP angle was changed from 140 deg to 160 deg. The HWP is now set to 160 deg in this state.

[LOCKING_PRMI]

The input matrix and feedback gains are configured according to the requested locking mode.

For PRMI 1f locking (PRMI_1F_LOCKED request):

• INMTRX:

  • POP17Q, POP45I → MICH

  • POP45I → PRCL

• The gains of MICH1 and PRCL1 are applied first.

• Once the signals exceed the thresholds, the gains of MICH2 and PRCL2 are applied.

For PRMI 3f locking (PRMI_3F_LOCKED request):

• INMTRX:

  • REFL51I → MICH

  • REFL51I, POP135I → PRCL

• The gains of MICH1 and PRCL1 are applied first.

• Once the signals exceed the thresholds, the gains of MICH2 and PRCL2 are applied.

The same filters are used for both PRMI 1f and 3f locking.

[PRMI_3F_LOCKED]

• This state is now connected to LOCKING_PRMI. Previously, it was connected to LOCKING_PRMI_FOR_OBSERVATION. The state index remains unchanged.

[PRMI_3F_LOCKED_FOR_OBSERVATION]

• This is the former PRMI_3F_LOCKED state, which was connected to LOCKING_PRMI_FOR_OBSERVATION. The state index was changed from 450 to 460.

3. Current status

• PRMI 3f is currently locked using the VERTEX Guardian with the PRMI_3F_LOCKED request. At the same time, PRMI ADS is requested through the ASC_LOCK Guardian. The interferometer remains stable under these conditions. The Initial Alignment Guardian has not yet been tested. The HWP settings used in the PRMI path of the Initial Alignment Guardian and the VERTEX Guardian are identical. Therefore, no conflict due to the HWP settings is expected.