Estimation of the R134a gas refractive index for use as a Cherenkov radiator, using a high energy charged particle beam

Gases with relatively high refractive index, n-1≥500×10-6 at atmospheric pressure, giving a satisfactory photoelectron yield at relatively low pressures (≤5bar) are rare. These gases are often the only practical solution for low momentum particle identification in conventional secondary beam lines. The refractive index of R134a, one of the most common gases available to the physics community, has never been measured or reported. In the present note, the results of a dedicated experiment to estimate the refractive index of R134a, using mixed hadron/electron beams in the range 0.5-10 GeV are presented.