A novel type of proximity focusing RICH counter with multiple refractive index aerogel radiator

Abstract

A proximity focusing ring imaging Cherenkov detector, with the radiator consisting of two or more aerogel layers of different refractive indices, has been tested in 1-4 GeV=c pion beams at KEK. Essentially, a multiple refractive index aerogel radiator allows for an increase in Cherenkov photon yield on account of the increase in overall radiator thickness, while avoiding the simultaneous degradation in single photon angular resolution associated with the increased uncertainty of the emission point. With the refractive index of consecutive layers suitably increasing in the downstream direction, one may achieve overlapping of the Cherenkov rings from a single charged particle. In the opposite case of decreasing refractive index, one may obtain well separated rings. In the former combination an approximately 40% increase in photon yield is accompanied with just a minor degradation in ARTICLE IN PRESS www.elsevier.com/locate/nima 0168-9002/$ -see front matter r

Progress in the development of silica aerogel as a RICH radiator in the Belle II experiment

“…In the limited expansion distance between the aerogel radiator surface and photodetector surface (20 cm in our case), a multilayer-focusing radiator (with different refractive indices) using thick aerogels was proposed and demonstrated [10] to increase the number of detected photoelectrons with no degradation in the resolution of the Cherenkov angle. In past beam tests using a prototype A-RICH counter, we achieved a / separation capability of more than 5 at 4 GeV/ with a basic detector configuration [2], [11].…”

Large-area silica aerogel for use as Cherenkov radiators with high refractive index, developed by supercritical carbon dioxide drying

“…The A-RICH counter will employ a focusing dual-layer aerogel radiator scheme with different refractive indices [29], as illustrated in Fig. A.14. The higher-refractiveindex aerogel tiles are arranged behind tiles with lower refractive index, such that the Cherenkov photons emitted from both layers focus on the photodetection plane.…”

Development of a 144-channel Hybrid Avalanche Photo-Detector for Belle II ring-imaging Cherenkov counter with an aerogel radiator

“…In order to solve this contradiction, we adopted two layers of aerogel radiator with increasing refractive indices along the particle path so that the Cherenkov image is focused on the photo-detection plane. With this scheme, we can increase the number of photons without degrading the single photon Cherenkov angle resolution [7]. Two 20 mm-thick aerogel tiles with the refractive indices of 1.045 and 1.055 will be used in the Aerogel RICH for upstream and downstream radiators [8].…”