How to measure void fraction of two-phase cryogenic flows Original Research Article

The report presents the experience in the field of designing, manufacturing and testing the void fraction sensors of round and annular cross-sections for research purposes and practical applications. These sensors are of radio frequency type with a uniform electric field within the measuring volume, and their readings depend on the dielectric permittivity of the media filling the sensitive part. The measuring system and method to calibrate these sensors are described. The temperature sensors used to measure the temperatures of the void fraction sensor body and the cryogenic flows are also presented. The operational characteristics of the radio frequency (RF)-systems for TESLA Test Facility cooled with two-phase superfluid helium at 1.8 K, Nuclotron and UNK cooled with two-phase helium at 4.5 K, the installation to separate isotopes of hydrogen at 22 K, etc. are reported.