What makes silica aerogel particularly appealing to RICH designers is that its refractive index can be chosen in the range 1.008-1.1 [4]. Applications in different experiments are given. We have considered the idea to accumulate multiple aerogel radiators so that Cherenkov photons from each tile organize a unified ring image on a photo-detector plane. A laser beam from a He-Ne laser source (wavelength 632.8 nm) was coupled to the lateral face of the sample as shown in Fig. Aerogels with low refractive index and high light transmittance, are highly desirable for Cherenkov detectors. We present optical and X-ray radiographical characterization of silica aerogels with refractive index from 1.05 to 1.07 for a Cherenkov radiator. the aerogel tiles dev eloped for LHCb have a refractive index n 1. Catalysis in Novosibirsk to produce very transparent silica aerogel with refractive index in the range 1.005-1.055 [9]. 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. (ii) Ultra-low refractive index (iii) Ultra-low dielectric constant (iv) High surface area (v) High refractive index, porosity Aerogels are also extremely fragile. The density of the aerogel has the potential of being changed if the aerogel absorbs the humidity in the air around it or comes into direct contact with liquid water. Ref. Introduction In the search for a Cerenkov radiator with a refractive index between 1.01 and 1.30, free from the problems that pressurized The basic concept behind the ASHIPH [13] method is to . Test the effect of humidity on aerogel by putting it in an area of controlled humidity and then retesting for the refractive index. The attenuation coefficient of the aerogel has been measured as 0.069 mm −1 for the broadband wavelength of 400-700 nm 27 , 28 . 27, 28. Density values lying between 0.003 g/cm 3 and 0.55 g/cm 3 are in principle available, corresponding to refractive indices of n=1.0006 ( ) and n=1.11 ( ), respectively. In the aerogel preparation, the starting phase is the hydrolysis and condensation of silicon alkoxides in presence of an alcoholic solvent. The average refractive index for opacified aerogels calculated from equation is in the range of 1.016-1.026 and that for pure silica aerogel is 1.01 as reported . The lowest an aerogel's refractive index has ever been recorded is 1.0026, which is a smidge lower than the refractive index of. The measurements describ ed in the following sec- tions ha v e been p. Introduction In the search for a Cerenkov radiator with a refractive index between 1.01 and 1.30, free from the problems that pressurized We report on the compression-dependent optical birefringence of samples with porosities from 95 to 99% under a uniaxial compression of up to 15% in the spectral range 320 . Transmission measurements for the optical constants {delta}, {beta} of the complex refractive index n=1{minus}{delta}+i{beta} of molybdenum are performed in the energy range 60{endash}930 eV. Aerogel manufacturing tolerances result in variations of the index greater than this over a tile so it is necessary to measure the index as a function of lateral position in each tile. The manufacturer can tune the material density ρ, and n and ρ are related by n (λ) = 1 + k (λ) ρ where k is a wavelength-dependent coefficient. The refractive index n of the aerogel is measured at the wav elengths λ =543.5 nm and λ=632.8 nm with an He- Ne laser source.. Therefore, a uniform refractive index in the detector is important to . Optical and Radiographical Characterization of Silica Aerogel for Cherenkov Radiator. the 1.012 and 1.008 refractive index aerogels. The new aerogels are hydrophobic, radiation hard, and exhibit excellent optical properties, as well as up to ~30% higher light yield than currently available aerogels. Silica aerogel with nonlinear refractive index was applied to optical power limiting or optical switching applications for eye or sensor protection against the threat of intense laser. Silica aerogel with nonlinear refractive index was applied to optical power limiting or optical switching applications for eye or sensor protection against the threat of intense laser. Commercially available aerogels on the other hand, with refractive indices in the range 1.005 to 1.06, correspond to electron Cherenkov thresholds between 4.62 MeV and 1.025 MeV. Phys. To characterize the effective index of a . Low thermal conductivity " 0.005 - 0.1 W/mK ! Its acoustical property is such that it can absorb the sound waves reducing speed to . Identify the refractive index (n) experimentally in order to know what particles can best be detected when shot through it. The air-like refractive index, n, of an aerogel substrate provides another dimension for ultralow-index plasmonic devices. We use the laser Fraunhofer method, an X-ray absorption technique, and a ring imaging Cherenkov detector on a beam test to investigate the uniformity of density (i.e., refractive index) of an aerogel tile. The Aerosol Refractive Index Archive (ARIA) provides a database of hundreds of refractive index datasets of typical aerosol particles. Preparation of aeropel films Silica films with refractive indices in the range of 1.006- 1.05 (equivalent volume porosity 98.5-88%) were prepared at ambient pressure by an optimized process wherein organo-siloxane Scalable variable-index elasto-optic silica-aerogel metamaterials have been used for transformation-optics wave bender and Luneburg lens. Construction principles and signal yields are discussed. This exotic substance has many unusual properties, such as low thermal conductivity, refractive index and sound speed - in addition to its exceptional ability to capture fast moving dust. Among low refractive index solid-phase materials, silica aerogels have the lowest refractive index (less than 1.01) and high optical transparency over 90% 7. It was shown earlier using in situ ellipsometric imaging that the high porosity of these films was mainly attributable to the dilation or `springback` of the film during the final . Considering the measurement of optical path difference [Fig. 9 . J. Phys. 3). Very highly porous (aerogel) silica films with refractive index in the range 1.006-1.05 (equivalent porosity 98.5-88%) were prepared by an ambient-pressure process 1,2.It was shown earlier usingin situ ellipsometric imaging 1 that the high porosity of these films was mainly attributable to the dilation or "springback" of the film during the final stage of drying. Aerogel is made by high temperature and pressure-critical-point drying of a gel composed of colloidal silica structural units filled with solvents. index 1.14-1.19 heat-treatment Ref. Among the ultralow-refractive index materials, silica aerogel has the lowest "air-like" refractive index of less than 1.1 and a high optical transparency over 90% 25, 26. This paper presents measurements of the refractive index of a hygroscopic silica aerogel block at several wavelengths. Low mean free path of diffusion High specific surface area (for a non-powder material) Low thermal conductivity Low sound speed Low refractive index Low dielectric constant Aerogel is used in the kaon aerogel Cerenkov detector at Jefferson Lab. The measurements, performed with a monochromator, have been compared with different parameterisations for n (λ), in order to determine the best chromaticity law for the aerogel. Hydrophobic silica aerogel samples produced by the above technique also had low absorption coefficients in the visible part of the spectrum. refractive index n to Δn/n < 0.07%. Aerogels are widely employed in Cherenkov detectors 28, thermal insulation 29, air cleaning 3, catalysis 30, and sensors 31. In the following this combi-nation will be referred to as "focusing combination". A proximity focusing RICH using aerogel as a Cherenkov radiator has been developed for the upgrade of the Belle detector. Aerogels are synthesized from molecular precursors by sol-gel processing. The refractive index n and the density ρ are related by: n(λ)=1+k(λ)ρ (3) where k is a wavelength-dependent coefficient. Also, because of their low refractive index of 1.007-1.240 32, these. Scalable variable-index elasto-optic silica-aerogel metamaterials have been used for transformation-optics wave bender and Luneburg lens. In the aerogel preparation, the starting phase is the hydrolysis and condensation of silicon alkoxides in presence of an alcoholic solvent. At the same time, its lightweight is also one of its advantages. We experimentally measured the refractive index of our aerogel as n 0 =1.078 using Snell's law 24 (Supplementary Fig. To test how likely this is to happen, we used a humidity Characterization study of silica aerogel for Cherenkov imaging. To determine what separation would be achieved with 1.008 refractive index aerogel with the optical Development and testing of aerogels with a refractive index as low as 1.008 and high optical quality, which has not been utilized previously, is the key to future Cherenkov detector upgrades and low energy particle detection studies. The standard block size is 18 X 18 X 3 cm3. Precise measurements of the particle velocity require the aerogel refractive index to be known with a precision of the order of Dn=n 1:5 10 4. Silica aerogels, a porous bulk . Aerogels are highly porous structures prepared via a sol-gel process and supercritical drying technology. International Journal of ChemTech Research CODEN( USA): IJCRGG ISSN : 0974-4290 Vol.1, No.4, pp 1052-1057, Oct-Dec 2009 An Overview of Silica Aerogels *Rakesh P. Patel1, Nirav S. Purohit1, Ajay M. Suthar2 1 Department of Pharmaceutics, S.K. Properties of aerogels ! Basic relations electrons (pe). Schematic for the ambient- pressure aerogel film process. . Thus, we cur-rently retain the production technique and facility for producing various aerogels with a wide range of refractive indices. Aerogel is made by high temperature and pressure-critical-point drying of a gel composed of colloidal silica structural units filled with solvents. Precise measurements of the particle velocity require the aerogel refractive index to be known with a precision of the order of An/n 1.5 x iO . A novel pin-drying method enables us to produce highly transparent hydrophobic aerogels with high refractive index by shrinking wet-gels. By measuring the values of δ x, δ y, θ 1 and β in the experiment, we obtain θ 2, θ 3, and the refractive index of aerogels using Snell's law. Uniaxial compression of compliant aerogels introduces an optical activity into the material. Silica aerogels have drawn a lot of interest both in science and technology because of their low bulk density (up to 95% of their volume is air), hydrophobicity, low thermal conductivity, high surface area, and optical transparency. multiple-refractive-index aerogel radiator [16]. This novel material has many unusual properties, such as a low thermal conductivity, refractive index, sound speed, along with a high surface area and thermal stability. Refractive index of aerogel samples was measured by characterizing the refraction of a laser beam from aerogel monoliths placed on a goniometer stage. Abstract Aerogel is a Cherenkov radiator with a refractive index in the range n = 1.01-1.1. It provides 4σ π/K separation in the momentum range 0.61.5 GeV/c [9,12]. However, two key issues should be addressed before applying . The measured mean number of photoelectrons in saturation is ∼12 for n=1.030, ∼8 for n=1.020, ∼10 for n . Phase I established the fabrication techniques for producing small batches (10-20 tiles) of aerogel with refractive index 1.01 and nominal dimensions 10 x 10 x 1 cm3. index: 1.006-1.05 Figure 1. Uniformity of the refractive index. Special drying techniques must be applied to replace the pore liquid with air while . This ultralow index is close to the index of air because of its high porosity, whereas it can reach as high as n ~1.43 when maximally compressed, resulting in a broad tuneable range of Δ n ~0.35. 1. Further desirable properties of aerogel are listed below, with some of these properties also the best known to man. A very slow shrinkage of alcogel at room temperature has made possible producing aerogel with high refractive indices of up to 1.265 without cracks. refractive-index silica aerogels Yeonhong Kim w, seunghwa Baek w, prince Gupta w, Changwook Kim w, Kiseok Chang x, sung-pil Ryu x, Hansaem Kang x, Wook sung Kim x, Jaemin Myoung y, Wounjhang park z & Kyoungsik Kim w The coupling of the surface plasmon near-eld into the sensing medium is key to the sensitivity of It is very robust with respect to high power input beam in continuous wave regime and does not show any boiling or melting phenomena. Silica aerogels prepared by the sol-gel method with supercritical drying have an extremely high porosity and hence extremely low refractive index equivalent to air [11, 12], which determines that it is the best candidate for preparation of thin film with ultra-low refractive index. Advancing this idea, we have developed aerogel in which the refractive index varies continuously. 2. The inner surface of the two aerogel trays with higher refractive index is covered with Millipore paper, however, those two trays with lower aerogel refractive index are again covered with Gore diffusive reflector for higher performance. the aerogel surface, n is the refractive index of the solid and α is the angle between the two adjacent sides of the blo ck. . We present a method to perform in-flight measurement of the refractive index, and the mapping of the aerogel radiator plan of the AMS-RICH, directly from cosmic rays. By C. da Silva Costa. Among the classes of aerogels, silica aerogel exhibits the most remarkable physical properties, possessing lower density, thermal conductivity, refractive index, and dielectric constant than any solids. Refractive Index Besides low weight, aerogels have ultimate (lowest) values in other properties: thermal conductivity, refractive index, sound speed, and dielectric constant. The ASHIPH system [10] for the KEDR detector [11] at BINP uses aerogel tiles of high transparency with a refractive index of 1.05.
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