Detecting ionizing radiation in liquid helium using wavelength shifting light collection

Detectors for counting low energy (less than 1 MeV) ionizing events in liquid helium are developed and characterized. These devices employ wavelength shifting fluors to convert extreme ultraviolet (EUV) helium scintillation light to the visible, allowing transport of signal light to room temperature. Three technological approaches are developed and tested: wavelength shifting fiber, composite acrylic tube, and diffuse reflecting tube of expanded teflon. The tube-based detectors have been used to detect magnetically trapped neutrons. All of the technological approaches have utility in other experiments, such as a more sensitive measurement of the neutron electric dipole moment and the monitoring of the low-energy solar neutrino flux.