Optical mass gauging of solid hydrogen Original Research Article

We have developed a prototype solid hydrogen optical mass gauge system (SHOMGS) to quantify the mass of hydrogen within a spherical container at liquid helium temperature. Monochromatic laser light of wavelength 797 nm enters a spherical vessel (d=100 mm), which is filled with a mixture of liquid helium and solid H2 particles of various sizes. The mass of the H2 is determined prior to insertion into the sphere by measuring the amount of gH2 that is condensed into an injector supply reservoir. In the SHOMGS a light source undergoes multiple internal reflections by the container walls and simultaneous absorption by the sH2 with the received signal being proportional to the mass of H2 in the container. The measured signal from the SHOMGS is compared to the injected mass of sH2 to quantify the performance of the device in this application.