Large-Volume E.L.F. Magnetic Field Compensation [LV-EMFC] Research Project - part 4

    For the so-called permanent solution, subject to further optimization studies, several driven coil and sensor placement constraints applicable to the temporary Beta Site installation have been dispensed with. Hallways, for example, are no longer relevant to cable placement, since lower z and y cable segments can be routed through arbitrarily located conduits under the protected structure. Only 9 driven coils are required in the permanent case. The coil locations shown here have been determined by means of optimization scripting in the simulation program.

NOTES:
Sensors for Y coil 1 at Y=7.94 and on line through center coil 1
Sensor for Y coil 2 & 3 at center coils
Upper Z centers at X-74.5, Z-3 and at Y-13.85 (1st Z coil)- center of coil
2nd coil Y=29=1.755m from center of coil along Y
3rd coil sensors: y-48.4 - center of coil

    A x-y axis slice is taken at Z = 1m, which corresponds to a z-axis region representative of highest human occupancy in the single-story Beta Site building. A.c. magnetic field magnitudes through the PV are significantly lower than in the uncompensated case (Panel 10).

    Z = 1.0m "boresight" linear plot comparing uncompensated magnetic fields rms magnitude with compensated rms magnitude and axial components peak magnitudes for Y₀ coil at -2.41m displacement from building.

    Noteworthy are the relatively low average values and peak-to-avarage ratios achieved for both B_y and B_z components. Both factors are essential indicators of compensation quality. ACMF fields over a large portion of the building interior attenuated to 1mg_rms or less.

    In this plot, survey record B_x,y,z magnitude/phase data have been used to compute relative ACMF phase variation within the site structure. This plot reveals phase shift due to the presence of electrically-conductive structural members throughout the building. Phase variation related to the structural symmetry is plainly visible, with a skew which is due to slight non-parallelism of the building and the transmission-line source right-of-way. Analysis of this survey phase data suggests that compensatory phase shift may be programmed into the LV-EMFC signal processors to increase the active-feedback system field attenuation coefficient in most installations.