Precise Measurements of the Density and Critical Phenomena Near the Phase Transitions in Helium Using High-Q Niobium Microwave Cavities

The experimental approach of using high-Q niobium microwave resonator (Q≈1010) and high resolution thermometry to achieve precise measurements of the density and critical phenomena in liquid helium near phase transitions is described. The numerical verifications of the experimental feasibility as well as the applications of the precision density measurement techniques are discussed.