Today we did one switch on - switch off cycle of the big turbo beteween SR and BS. This pump was noticed to produce noise lines around 465Hz back in June (37927) and we kept it off since then.
Today we wanted to reasses its noise contribution, to check if there is any change after the PR and SDB1 baffling interventions.
Here the times (LT):
9:03 people near SR
9:04 ctrl on
9:05 fan (Provisional one) on
9:07 start sweep
9:10- 9:12 people in det lab
9:19 steady reached
9:25 start slow down (fan still on)
9:31 pump slow down completed
Figure 1 shows the noise sweep up (then down) as the pump slowly increase (then decrease) its rotation frequency up to the steady state value (463Hz). The seismic noise is loud on the BS tower (x100 above quiet) and it is also sensed at DT tower (x10 above quiet) and acoustically (ENV_CEB_MIC). Some noise is seen in DARM between 250 and 460Hz (this is a region where we know the ITF is sensitive to CEB acoustic noise (39916) and DT tower vibrations (39915).
When in steady state the 463Hz line and two sidebands at +-6.5Hz are seen in Hrec (Figure 2). This was also the case before O2, although it seems the coupling has slightly decreased (Figure 3).
