Weak Interaction Discussion Group (WIDG) Seminar: Emily Grace, Royal Holloway University of London, “Calculations and Measurement of the Rayleigh Scattering Length of the Scintillation Light in Liquid”

Event time: 
Tuesday, May 9, 2017 - 12:00pm
Wright Lab, EAL 108 Conference Room (EAL108) See map
268 Whitney Avenue
New Haven 06520
(Location is wheelchair accessible)
Event description: 

Like all the noble elements, argon is a scintillators, i.e. it produces light when exposed to radiation. Large liquid argon detectors have become widely used in low background experiments, including dark matter and neutrino research. However, the index of refraction of liquid argon at the scintillation wavelength has not been measured and the previous Rayleigh scattering length calculations disagree with measurements. We introduce a new calculation using previously measured data in liquid argon to extrapolate the optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship. Further, we tested these calculations using a test stand, designed and constructed at Royal Holloway, to experimentally verify the scattering length of liquid argon. This experiment consisted of a long tube of liquid argon with window on one end and photomultiplier tube on the other side. The argon was scintillated at different positions using a collimated, external gamma source. The scattering length was calculated by examining the amount of light detected as a function of position from the window yielding a final result of 58±4 cm at a temperature of 90 K.