A line at 19.9 Hz, amplitude 1V, has been injected on each WE MIR coil in configuration OPEN, which means connected to the electronics only on one side. In this way no current flow is generated by the injection, but only a voltage. During the injection, only one pair of WE coils was used to lock. The one not used for the lock and not used for the injection was totally disconnected, when the line was injected on UR and DL. Going to UL and DR, a large effect on the 50 Hz was induced in DISCONNECTED state, out of the range of the feed forward applied on WI, so the one not used was kept in the standard state (CLOSED in LN2).

The gps of the injections are:

gpsDL=1425315918;
gpsUR=1425316718;
gpsDR=1425318518;
gpsUL=1425319518;
gpsCLean=1425321068;

duration: 300s (even much more, in some cases)

The attached plot shows hrec in one case (the others are similar except for the impact on the 50 Hz). The amplitude of the injection was set in order to have a signal at the double frequency (39.8 Hz). That signal was small, but we decided to stop increasing the line because the effect at 19.9 Hz was already very large.

The same injections have been performed on NI. The amplitude of the line was 0.3 V. The three coils not involved in each injection were in standard state (LN);  the effect on the 50 Hz was large in any case.

The gps are:

NIUL=1425322018;
NIDL=1425322718;
NIUR=1425323818;
NIDR=1425324498;

300s are always available, but sometime the data are spoiled by a glitch, visible as a drop of the range. In order to select the better periods, the state of the injections are visible in the channels Sc_NI_MIR_VOUT_UL etc.