Commissioning a Helium II Test Facility at SLAC

Liquid helium is the only fluid that exhibits the unique properties characteristic of a superfluid when cooled to temperatures near absolute zero. This superfluid helium state is commonly referred to as He II. Among the many odd properties are a vanishingly small viscosity and a high effective thermal conductivity. A He II test facility will provide researchers in the Experimental Facilities Department at SLAC with the opportunity to do research in the superfluid range with relative ease. The nature of this project is to test the functionality of the existing helium components in the cryogenics lab and recommend improvements. The basic experimental setup consisted of a helium dewar, a vacuum pump system, and a network of sensors. After adding liquid helium into the dewar and turning on the vacuum pump, we observed that the pump was able to reduce the pressure down comfortably into the superfluid state. Furthermore, by adding heat to the fluid in set increments we learned what amount of heat could be added while still keeping the helium in the superfluid range. Our final test was to see if we had the ability to change the pressure via the MKS exhaust valve controller. The controller failed miserably and was found to be inadequate for the type of experiments to be done. Among the other recommended improvements were: adding isolation valves to the vacuum pump line, erecting a supply line for clean helium gas, incorporating a relief valve in the helium recovery line, and documenting the existing vent and vacuum lines. Once these improvements are made, the He II test facility should be up and running, allowing researchers to dive as deep as they please into the superfluid state