Virgo Logbook

AdV-DET (Commissioning)

gouaty, ruggi - 10:58 Friday 02 February 2018 (40504)

Low frequency line excitation on SDB1

Yesterday afternoon (Feb 01), we injected a low frequency line on the top stage of the SDB1 suspension in order to displace the bench along the longitudinal degree of freedom.

The following measurements were taken (all times in UTC):

With SDB2 Z control ON:

First quiet reference data: 18:30:00 - 18:33:50
Injection 1 (Figure 1): Sa_OB_F0_X moving by +/-13 um, SDB1_LC_Z moving by +/-17 um, Start = 18:33:55, Duration = 240s
Injection 2 (Figure 2): Sa_OB_F0_X moving by +/-20 um, SDB1_LC_Z moving by +/-25 um, Start = 18:39:16, Duration = 300s
Second quiet reference data: 18:44:43 - 18:47:04

With SDB2 Z control OFF:

Quiet reference data: 18:47:04 - 18:49:45
Injection 3 (Figure 3): Sa_OB_F0_X moving by +/-20 um, SDB1_LC_Z moving by +/-25 um, Start = 18:50:05, Duration = 240s

We must now analyze this data to evaluate the scattered light coupling factor on SDB1.

Images attached to this report

Comments to this report:

mwas - 13:58 Friday 02 February 2018 (40511)

Images attached to this comment

mwas - 16:01 Friday 02 February 2018 (40515)

The scattering coefficient that matches the measurement is 2e-5, this is 8 times smaller than in october (16e-5 #39901, after removing the OMC covers), and 2.5 times smaller than in September (5e-5 #39454, before removing the OMC covers). It is not conclusive as other things changed too, but it could be that the OMC covers have a large impact on scattered light, if true to it would be good to replace them with something darker than shiny aluminium.