In one aspect of the invention an induction resistivity tool incorporated into a downhole tool string comprises an outer wall of a downhole component having an outer diameter. At least one induction transmitter assembly is disposed along the outer diameter. The transmitter assembly comprises at least one coil array and at least one induction transmitter coil wound about at least one core. The coil array comprises a plurality of magnetic units and each unit comprising a magnetic field orientation. The magnetic field orientations accumulatively form a Halbach array with an augmented field side and a canceled field side of the array. The transmitter assembly generates an induction signal from outside the outer wall and substantially prevents the signal from entering the outer wall when the transmitter assembly is carrying an electrical current.

The present invention is directed to a method and apparatus of multi-directional acceleration for parallel imaging. An RF coil assembly is constructed to have a plurality of RF coils arranged in axial and tangential direction for image data acquisition with acceleration in at least two dimensions.

In one aspect of the invention, a sensor assembly for incorporation into a downhole tool string comprises at least one sensor adapted to detect changes in magnetic flux proximate a first portion of the downhole tool string. A second portion of the downhole tool string comprises a characteristic that interferes with a magnetic reading of the at least one sensor. At least one magnetic focusing array is disposed on an outer diameter of the tool string, and the at least one magnetic focusing array reduces an effect on the sensor of the interfering characteristic of the second portion.