Today we performed some test injections with the NEB wall coil. The coil has been connected to the amplifier module (the connection is still temporary and some work has to be finalized, for instance the acquistion of monitoring signals and remote switch off are still to be implemented).
We added one magnetic probe (named ENV_NEB_MAG_COIL_N) positioned at the geometric center of the wall coil and oriented along the coil axis, that is along the N arm (Figures 1 and 2). Note that, at first we attached the probe to the SAS separating wall, and the probe was saturating, probabily because of eddy currents induced in aluminum layer of the wall.
Also: we moved magnetometer ENV_NEB_MAG_V onto the tower base, EAST side, first orienting along the N-arm direction and then perpendicular to it (see details in the attached log file). While magnetometers ENV_NEB_MAG_W and ENV_NEB_MAG_N remained in their usual assigned location.
Pictures of the magnetometers are attached.
We injected into the amplifier module (Voltage input) white band passed from 0-1000 Hz (channel ENV_NOISE_NEB).
We rotated the ENV_NEB_MAG_V onto the tower base to the E-W direction and repeated the injection.
DETAILS of the INJECTION are in the attached LOG file
Figure 7 compares transfer functions between the injected noise and the 4 magnetic channels (purple: tower magnetometer oriented North-arm, blue: tower magnetomeer oriented West-arm).
The 1/f slope above 10 Hz or so seems to correspond to the pole of the wall coil. A more precise analisys of data and computation of coil pole based on teoretical and measured R and H parameters has to be done.
Figure 8 shows ffts of the injected magnetic noise.