Shield for decoupling RF and gradient coils in an NMR apparatus

An NMR apparatus including means for producing a homogeneous magnetic field, a radio frequency (RF) coil for transmitting and receiving RF energy, a gradient coil for generating pulsed linear magnetic field gradients at audio frequencies and a decoupling shield disposed between said RF and gradient coils, said RF coil being disposed within the shield, said shield comprising:

• a first array made up of a multiplicity of electrically conductive regions separated by a first set of relatively narrow, compared to the width of said conductive regions, non-conductive regions, said array being disposed on the inner shield surface;
• a second array made up of a multiplicity of electrically conductive regions separated by a second set of relatively narrow, compared to the width of said conductive regions, non-conductive regions, said first and second arrays being disposed on opposite surfaces of a member formed of a high dielectric material, the conductive regions of one array being offset relative to the conductive regions of the other array such that the conductive regions of the one array bridge the non-conductive regions of the other array to form a plurality of capacitive elements which act essentially as electrical short-circuits at radio frequencies and which transmit substantially unaffected the homogeneous magnetic field and the audio frequencies associated with the pulsed magnetic field gradients.