Measurements of the magnetic field direction for the polarized He-3 target.

For accurate measurement of the neutron electric form factor the direction of the magnetic field should be determined with a few milli radian accuracy. Furthermore, to achieve high polarization of the He-3 target, precise knowledge of both the direction and the gradient of the field is required. We have developed custom tools based on the Hall probes for such a measurement. The results of the measurements will be presented and compared with detailed calculations based on OPERA.