The use of n-perflourcarbons as RICH radiators

Ring Imaging CHerenkov (RICH) detectors in high energy physics demand a sufficiently high and stable refractive index and a long radiation length combined with good transparency extending into the UV range. n-Perflourcarbons fulfill all these criteria and show chemically inert behavior. In this paper an overview of n-perflourcarbons used for RICH detectors will be given. As an example of the experimental techniques for purification and recuperation, the C4F10 system for the LHCb RICH 1 detector will be discussed. The purification of the C4F10 gas cycle is based on a cascade of two membranes. The selected membranes let smaller molecules such as N2 pass 16 times more effectively than C4F10. The recuperation system liquefies the C4F10 by cooling it down to - 40 ∘ C . The liquid n-Perflourcarbon is extracted and the remaining light gases such as Ar go to the waste line. Laboratory tests have proved the capability of this system in 20 recuperation runs, with an average loss of less than 10% of the C4F10 per recuperation cycle.