Aerogel detector with a Fresnel lens focalization

The use of threshold Cherenkov detectors for the identification of high momentum particles in high energy physics experiments is connected with the efficiency of detection of light in the aerogel. As one goes lower in the refractive index, less photons are emitted, and more attention should be paid to the improvements of the detection efficiency. The light integration box method relies on photomultipliers of large size and requires even two of them. We have studied the possibility to use a thin focalizing element (Fresnel lens) between the aerogel and the photomultiplier to focalize the light onto a smaller diameter photomultiplier. The results show that for good aerogel and low indices of refraction ( < 1.01 ) the scheme with the aerogel and the Fresnel lens may be superior and less costly than the conventional set-up.