A magnetic resonance system, comprising: a plurality of radio frequency coil elements adjacent to an examination region, wherein the plurality of radio frequency coil elements is operatively connectable to at least one radio frequency transmitter, and is configured to generate a B 1 excitation field in the examination region according to a generated excitation signal; and at least one passive shimming device (22,24) disposed in the examination region between the radio frequency coil elements and a space in the examination region to be occupied by a subject, and provided for improving uniformity of the generated B 1 excitation field, the at least one passive shimming device (22,24) including at least one of - at least one rod composed of a non-proton magnetic resonance signal generating solid dielectric material with a permittivity of at least 100 that is disposed in the examination region to passively shim the generated B 1 excitation field; and - at least one tube configured to receive a variable volume of dielectric fluid disposed adjacent to the radio frequency coil elements to passively shim the generated B 1 excitation field, wherein the magnetic resonance system further comprises a shimming processor which is configured to analyze a distribution of the generated B 1 excitation field and to determine the position of the at least one rod and/or the volume or dielectric permittivity of the at least one tube in order to improve a uniformity of the B 1 distribution to optimize a homogeneity of the B 1 excitation field, wherein in the case of the at least one rod, the magnetic resonance system includes an actuator which is configured to position the dielectric rod in the examination region according to the position determined by the shimming processor, and in the case of the at least one tube, the magnetic resonance system includes a reservoir which is configured to supply the dielectric fluid to the at least one tube; and a fluid controller which is configured to control at least one of the volume of dielectric fluid in the at least one tube and the dielectric permittivity of the dielectric fluid supplied to the at least one tube according to respectively the volume and dielectric permittivity determined by the shimming processor. a plurality of radio frequency coil elements adjacent to an examination region, wherein the plurality of radio frequency coil elements is operatively connectable to at least one radio frequency transmitter, and is configured to generate a B 1 excitation field in the examination region according to a generated excitation signal; and at least one passive shimming device (22,24) disposed in the examination region between the radio frequency coil elements and a space in the examination region to be occupied by a subject, and provided for improving uniformity of the generated B 1 excitation field, the at least one passive shimming device (22,24) including at least one of - at least one rod composed of a non-proton magnetic resonance signal generating solid dielectric material with a permittivity of at least 100 that is disposed in the examination region to passively shim the generated B 1 excitation field; and - at least one tube configured to receive a variable volume of dielectric fluid disposed adjacent to the radio frequency coil elements to passively shim the generated B 1 excitation field, - at least one rod composed of a non-proton magnetic resonance signal generating solid dielectric material with a permittivity of at least 100 that is disposed in the examination region to passively shim the generated B 1 excitation field; and - at least one tube configured to receive a variable volume of dielectric fluid disposed adjacent to the radio frequency coil elements to passively shim the generated B 1 excitation field, wherein the magnetic resonance system further comprises a shimming processor which is configured to analyze a distribution of the generated B 1 excitation field and to determine the position of the at least one rod and/or the volume or dielectric permittivity of the at least one tube in order to improve a uniformity of the B 1 distribution to optimize a homogeneity of the B 1 excitation field, wherein in the case of the at least one rod, the magnetic resonance system includes an actuator which is configured to position the dielectric rod in the examination region according to the position determined by the shimming processor, and in the case of the at least one tube, the magnetic resonance system includes a reservoir which is configured to supply the dielectric fluid to the at least one tube; and a fluid controller which is configured to control at least one of the volume of dielectric fluid in the at least one tube and the dielectric permittivity of the dielectric fluid supplied to the at least one tube according to respectively the volume and dielectric permittivity determined by the shimming processor.