Buoyancy‐Driven Natural Convection of Liquid Helium in an Electron Bubble Chamber

A small liquid helium test chamber with 1.5 L active volume has been designed and constructed, to make the fundamental measurements of physical properties of electron bubble transports in liquid helium, aimed at developing a new cryogenic neutrino detector, using liquid helium as the detecting medium, for the detection of solar neutrinos. The test chamber is a double‐walled cylindrical container equipped with five optical windows and ten high voltage cables. A LN2/LHe cryostat and a needle valve for vapor helium cooling are used to provide a 1.7∼4.5 K low temperature environments for the test chamber. One of key issues for the cryogenic design and experimental sensitivity of electron bubble tracking is that of keeping a thermally uniform liquid helium bath. The external heat loads to the chamber will generate a buoyancy‐induced convection of liquid helium, which will carry the electron bubbles and accelerate or decelerate their transportation and therefore must be reduced to the minimum, so that the slow ...