Superconductive level indicator for liquid hydrogen and liquid neon, and measuring method for liquid level measurement

A method for level measurement in vessels for the storage of liquid hydrogen or liquid neon, comprising the following steps:

• providing a probe comprising a filament wire made of a superconductor based on magnesium diboride MgB2 arranged vertically or inclinedly to the vertical in a liquid hydrogen vessel under a condition of no current flow through the probe, such that the superconductor is in the superconducting state over a length in both a liquid phase and a gas phase of the hydrogen or neon in the vessel;
• activating a current flow along the superconductor;
• and, simultaneously with activating the current flow or shortly therebefore or shortly thereafter, heating an upper portion of the superconductor such that an initial region of the superconductor in a vicinity of the upper portion is in the normally conducting state, and generating ohmic heat in the upper portion;
• controlling the ohmic heat to propagate the normally conducting phase along the superconductor through resistive heat evolution in regions that are already normally conducting, in combination with thermal conductivity within the vessel, the resistive heat evolution in the MgB2 filament wire and the cooling by the surrounding gas or liquid, which opposes the heating, being matched to each other to control a speed of propagation within certain limits;
• after attainment of a steady state in which propagation comes to a halt at a height of a phase boundary between hydrogen or neon in liquid and gas phases due to intensive cooling inside the liquid phase, and a voltage drop measured across the superconductor approaches a constant value, measuring the voltage drop with a voltage measuring apparatus and storing the voltage drop that is measured to determine a liquid level in the vessel;
• and
• tracking any fluctuations in the liquid level by comparing a measured voltage drop to the voltage drop that has been stored or deactivating the probe until a succeeding measurement.