Apparatus for the monitoring of the passsage of conductive objects through a tube

A system for monitoring the passage of individual conductive objects for the core of a nuclear reactor along a path, said system comprising:

• a measuring stretch including an electrode disposed along said path and juxtaposed with a conductive tube wall so that said electrode and said conductive tube wall constitute members defining a normally nonconductive gas-filled gap subject to electrical breakdown and traversed by said object;
• a high-voltage direct-current generator capable of generating voltages of the order of 15 kilovolts connected across said members and said gap whereby a voltage field is established across said gap sufficient to develop a separate discharge in the presence of said object;
• a high-ohmic resistor with a resistance value of megaohms connected in series with said electrode and said high-voltage direct-current generator;
• a voltage divider connected across said members and including a low-ohmic resistor connected to said wall and adapted to develop a varying high-frequency oscillation signal of a signal voltage of the order of up to 100 volts upon the passage of an object through said gap;
• and
• circuit means responsive to said signal voltage and including an amplitude demodulator connected across said low-ohmic resistor and generating a signal corresponding substantially to the envelope curve of a high-frequency oscillation signal induced by the passage of each object through said gap as a result of the interaction of said object, said field, a stray capacitance of said stretch, said high-ohmic resistor and said gap.