EXTRACTION OF MICRON-SIZED PARTICLES FROM A HE II BATH

Our laboratory is developing a new technique to separate micron and possibly submicron size particles by size using superfluid helium (He II). A heat current in the He II generates normal fluid flow, which in turn drags particles of different sizes into different sections of an experimental channel immersed in a He II bath. We developed a technique to extract the particles from the separation channel while it is immersed in the helium bath. A tube is inserted from the room temperature environment to the area in the channel collecting the particles to be extracted. This tube is closed at the bottom by a multi bore tube cylinder and is pumped to a lower pressure that the helium bath. The pressure gradient through the multi bore tubes creates a temperature gradient which drives the normal component of the He II and the particles into the tube. The particles can then be collected and extracted by pulling the tube out of the bath. We compare the performance of this device for extraction of particles of different materials and size varying between 0.3 and 9.9 mum.