Enhanced performance antennas for NMR logging

1. Field of the Invention An antenna design for a downhole nuclear magnetic resonance logging tool is enhanced to shape the resultant RF field generated by the antenna. The enhancement is accomplished by adding additional turns to a portion of the antenna, either circumscribing a ferrite material or located on the surface of an at least partially non-conductive material. The additional turns or half turns in combination with the RF field from parallel antenna portions result in a RF field contribution that is proportionally higher than the RF field contribution from the coil portions which are not enhanced. Further, the total RF field can be shaped over a earth sample region depending on placement of the enhancing turns. In this way, for example, the total RF field can be generated to achieve an orthogonal alignment with a static magnetic field over a larger region of the sample.