A Laser system for flow field imaging in superfluid helium using He2*

For visualization of the flow field in superfluid Helium (He II), He₂* excimer can be traced by using Laser induced fluorescence (LIF). In our group the proposed He₂* excimer generation method is based on the neutron absorption reaction of naturally abundant ³He in Helium. Small He₂* clusters generated by this method are then available for 3D LIF imaging. By applying this method, we already confirmed successful generation of He₂* excimers using our laser system. In this study, for successful visualization of He₂* excimer images in superfluid Helium, the required laser parameters, such as f intensity, repetition rate and wavelength were investigated. For systematic characterization of these, an offline system based on a high voltage discharge for excimer generation is being set up to provide a more intense and accessible source of excimers, not requiring the use of a neutron beam.