Aerogel refractive index

Because of their low density, aerogels have a refractive index very close to 1. Experimentally one finds that... 

As a result of the small refractive index, light enters and leaves a piece of aerogel almost without reflective losses and refractive effects. The dependence... 

The refractive index of silica aerogels increases with their density p (kg m ) accord-... 

Figure 28.7 shows a typical model of a threshold-type Cherenkov counter. Silica aerogel is filled in a box to which photomultiplier tubes (PMTs) are attached. The refractive index of aerogel is set so that the Cherenkov light is emitted for pions but not for kaons [8,9]. In this way, it is known that kaon/pion/proton separation in the momentum region of 1.0-3.5 GeV/c is possible using aerogel with low refractive index such as 1.01-1.03. 

MacKenzie J D (1988) Applications of the sol-gel process. J Non-Cryst Solids 100 162—168 Adachi I, Sumiyoshi T, Hayashi K, lida N, Enomoto R, T sukada K, Suda R, Matsumoto S, Natori K, Y okoyama M, Yokogawa H (1995) Study of a threshold Cherenkov counter based on silica aerogels with low refractive index. Nucl Instr Meth Phys Res A, 335 390-398... 

Optical coatings The losses of optical devices can be reducedby coating them with an aerogel of (matched) low refractive index (Hrubesh and Poco, 1995 Hru-besh, 1998) in this way, more sunlight can reach the active surface of a solar cell and, in fiber optics, light collection at the fiber entrance and signal propagation efficiency can be improved. 

The important properties ofhydrophobic sihca aerogels will be described in this section. Especially, we describe silica aerogers inihal properties and its resistance to moisture for optical properties, transparency and refractive index. 

Figure 4-10. Correlation between densities and refractive indexes of MEW s hydrophobic silica aerogels.

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