The paper presents results of investigations of
the process of the creation of a diamagnetic cavity by
a laser-produced plasma in a strong transverse magnetic
field of 10 T in induction. The plasma was produced from
a flat, teflon target by an Nd laser of 5 J in energy and
about 1 ns in pulse duration. The investigations were carried
on by means of a three-frame interferometry and a non-contact
magnetic probe, a so called remote magnetic probe (RMP).
For the needs of this work, we developed a methodology
for the measurement of the dimensions of the cavity during
its expansion by means of the RMP, taking into account
the plasma expansion geometry that is specific to flat
targets. The dynamics of the process of creation of the
diamagnetic cavity, its shape and dimensions have been
determined. A very good consistency of dimensions of the
diamagnetic cavity and plasma boundary in their quasisteady
state, obtained with both diagnostics, allows us to apply
the RMP method not only for the investigation of diamagnetic
properties of various laser-produced plasmas, but also
for the evaluation of their initial kinetic energy and
its transformation in magnetic field.