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VIS (General)

ryutaro.takahashi - 18:44 Thursday 03 September 2026 (37449)

Change of SRCL

[Ushiba, Takahashi]

We moved three SR mirrors to change SRCL. Each setpoint for the IP L LVDT was changed by +200 [um]. SRCL was decreased by 1mm in Total. Moving order was SR3, SRM, and SR2. After changing the setpoints, GRY was locked and aligned. The setpoints for the Oplev yaw were changed from 37 to 31 for SR3 and from -49 to -45 for SR2. Changed values are summarized below. Oplev L was different from IP L by a factor of 2. After the length measurements, all setpoints were recovered.

	IP L setpoint [um]	IP L OUT [cnt]	OL L [um]	OL P [urad]	OL Y [urad]
SR3	0:200	-3000:3000	+210 (-90:120)	-2 (17:15)	-6 (37:31)
SRM	-550:-350	-6200:-2500	+190 (-60:150)	+5 (32:37)	-32 (68:36)
SR2	-100:100	6900:9900	+105 (-245:-150)	+26 (18:44)	+4 (-49:-45)

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ryutaro.takahashi - 12:51 Friday 11 September 2026 (37481)

[Ushiba, Takahashi]

We checked the actual movable range of the IP in the Type-B suspensions. The transfer functions of the IP L were measured by changing the setpoint for L. The resonant frequencies of L depended on the setpoint and became higher with larger deviation. To keep the same (or lower) resonant frequencies, the movable range should be set to +4mm for SRM, +3mm for SR2, and +3mm for SR3.

The measured resonant frequencies are summarized below. The SR3 suspension touched a part (maybe the side stopper for the GAS filter) when the setpoint was set to 5000. The plots show the measured transfer functions in SRM, SR2, and SR3.

Shift [mm]	0	+3	+4	+5	+6
SRM [mHz]	63	63	63	66	133
setpoint	-500	2500	3500	4500	5500
SR2 [mHz]	66	66	82	94	102
setpoint	0	3000	4000	5000	6000
SR3 [mHz]	86	74	94	hit
setpoint	0	3000	4000	5000

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