A Particle Seeding Apparatus for Cryogenic Flow Visualization

Abstract

A particle seeding apparatus to create neutrally buoyant solid particles in liquid helium (He I and He II) has been developed and successfully tested as part of a flow visualization experiment. The apparatus consists of a liquid cavity to hold the hydrogen-deuterium mixture, a vacuum jacket, a plain orifice atomizer, a needle valve, a solenoid valve, heaters and temperature sensors. During the condensation process, the vacuum jacket around the hydrogen cavity was filled temporarily with helium gas. The needle valve, which is coated with indium to prevent any leaks, closes the gate between liquid mixture and helium, and operates via a solenoid. Heaters in the can control the temperature of the liquid mixture. Temperature is monitored by silicon diode temperature sensors placed on the can. Tests have been performed inside a glass cryostat for visual inspection, and have been recorded using a black and white video camera and a camera equipped with a macro lens. Depending on the flow velocity inside the nozzle, atomization with different particle sizes has been observed.