Apparatus for the solidification of a doped electricity conducting material and the continuous checking of its dopant content

An apparatus for use in solidification of a doped, electrically conducting material and for use in monitoring said solidification, said apparatus comprising:

• a first forming means for forming a first liquid of undoped material in thermodynamic equilibrium with a first solid of said undoped material;
• a second forming means for forming a second liquid of doped material in thermodynamic equilibrium with a second solid of said doped material, said solidification occuring at a solidification interface between said second liquid and said second solid in said second forming means;
• a short circuiting means for electrically short-circuiting said first liquid and said second liquid;
• and
• a measuring means for measuring an electric potential difference between the undoped first solid and the doped second solid whereby to permit calculation of the dopant concentration at said interface based upon said electric potential difference.