Today, after the damping of the N-3 link tube done by Vac team (it will be reported in another dedicated entry), we repeated tapping tests while interferometere was locked.

We did not have the same problems reported in entry 39373 (SDB2 out of control and interferometer unlocked due to SDB2 IP Geophones saturation), so the work done on the link is an improvement.

We report the GPS time (UTC) of the tapping tests, with some brief comments.

- please have a look at linked entry for figures and explanation of links location

(note: we move the little temporary accelerometer ENV_SDB2_LINK_ACC over every “tapped” link)

tapping over “N” Link

Time: Sep22,17-12:35:33 -> GPS: 1190118949

Time: Sep22,17-12:36:36 -> GPS: 1190119012

We see a peak around 90Hz in the accelerometer, and (maybe) also in Hrec.

Also, some structures at 240Hz in Hrec

tapping over N -1

Time: Sep22,17-12:39:56 -> GPS: 1190119212

Time: Sep22,17-12:40:56 -> GPS: 1190119272

Low frequency (<30Hz) noise in Hrec

tapping over N-2

Time: Sep22,17-12:44:09 -> GPS: 1190119465

Time: Sep22,17-12:45:33 -> GPS: 1190119549

We see structures between 60 and 70Hz in Hrec

tapping over N-3

Time: Sep22,17-12:48:39 -> GPS: 1190119735

Time: Sep22,17-12:50:21 -> GPS: 1190119837

No visible structures in Hrec, moreover the SDB2 is now stable (interferometer does not unlock as before)

accelerometer ENV_SDB2_LINK_ACC is left over this last link (N-3) for the time being