Apparatus is provided for causing nuclear magnetic resonance in a
plurality of samples. The apparatus comprises a magnetic system for
generating a magnetic field including a working volume in which the
magnetic field is substantially homogeneous. A sample holder is adapted
to hold the plurality of samples within the working volume. A common
transmitting means provides radio frequency signals simultaneously to
each of the samples thereby causing nuclear magnetic resonance within
them. A multiple receiver array detects the nuclear magnetic resonance
signals using a plurality of receiving means in corresponding receiving
circuits where each circuit has a different spatial sensitivity to each
sample. A probe and sample holder according to the invention are also
provided.