NUCLEAR MAGNETIC RESONANCE TOOL WITH MAGNETOSTRICTIVE NOISE COMPENSATION

摘要

An NMR logging apparatus and method are provided including an antenna havingcompensation for magnetostrictive ringing. The antenna comprises at least oneinductive winding (126) and a core (118) having a first portion havingpositive magnetostriction in the presence of a radio frequency magnetic field,and a second portion having negative magnetostriction in the presence of theradio frequency magnetic field. The positive and negative portions may betiles (302, 304) shaped as polygonal cylinders arranged with alternatingpositive and negative tiles forming at least one layer of a matrix, or theportions may be constructed using ferrite powder fixed in epoxy and shaped inpolygonal cylinders.