Resonators spherical

Further progress depends essentially on the developments in p and C measurements. A new proposal is to apply quasi-spherical resonators for DCGT [40],... 

The spherical resonators are represented by a cylinder of the same volume. 

This experiment is based on a modified version of Kundt s tube, in which the wavelength X of standing waves of frequency /are determined electronically. Figure 3 shows the experimental apparatus, which utilizes an audio oscillator driving a miniature speaker as the source and a microphone as the detector. Also, an alternative apparatus based on a small spherical resonator has been described by Colgate et al. ... 

The rise in importance of this method results from the high accmacy with which the speed of sound can now be measured from the spherical modes of a spherical resonator, and the fact that the results are not subject to errors from gas adsorption. One form of apparatus [89-ewi/tru] is shown schematically in Figme 8. The sealed resonator is constracted from two hemispheres of aluminium alloy, mounted on a copper support. It has two ports machined at an angle of 90° to take the electroacoustic transducers. 

The speed of sound in compressed gases is determined from the lowest-order radial modes of a spherical-resonator [89-ewi/tra, 81-meh/mol] of mean radius Aq at the given temperature and zero pressure, since (m/oo) is given by... 

For a spherical resonator no resonance experiments with laser excitation have been reported so far. However, acoustic excitation of radial modes with a second microphone was accomplished just recently and, as expected, very high Q factors were obtained in a high quality spherical resonator The goal of these experiments was the measurement of thermophysical properties with high precision. A spherical resonator is also an interesting candidate for photoacoustic investigations. 

The resonator with the highest symmetry is the spherical resonator. A treatment of oscillations in a spherical cavity was already given by Rayleigh in 1894 A recent discussion may be found in Ref. In the simple loss-free model, sound is described by the homogeneous wave equation ... 

Table 2. Eigenvalues of the radial modes in a spherical resonator...

Very precise speed of sound measurements were performed by Mehl and Moldover utilizing a spherical resonator and acoustic excitation of radial modes As... 

Cha JN, Bartl MH, Wong MS et al (2003) Microcavity lasing from block peptide hierarchically assembled quantum dot spherical resonators. Nano Lett 3(7) 907-911... 

The first step towards higher sensitivities is the increase of the absorption path length L. This can be for instance achieved when the absorption cell is placed inside a multipass cell. One example is shown in Fig. 1.2. Two spherical mirrors with a high reflectivity R are separated by a distance d which nearly equals the mirror radius r forming a nearly spherical resonator (Vol. 1, Sect. 5.2). 

Resonators with two curved mirrors (a general spherical resonator, see Figure 3.5b) include a range of different configurations, depending on the radii of curvature of the mirrors and their relative... 

The so-called concentric resonator (Figure 3.5d), with r - -r2= L, represents the functional opposite of the plane-plane resonator. It is easiest to align, has the lowest diffraction loss and exhibits the smallest mode volume. For example, CW dye lasers incorporate this type of cavity (see Chapter 4.3) because of the short length of the active medium (the dye jet), strong focusing of the pump and resonator beams is necessary to cause efficient stimulated emission and to generate sufficient gain for laser action. However, this type of spherical resonator is not commonly used with any other laser. 

For these spherical resonators the magnification factor M can be expressed by the resonator parameter G [5.25] ... 

Fiedler M and Hess P (1989) Laser excitation of acoustic modes in cylindrical and spherical resonators theory and applications. In Hess P (ed) Photoacoustic, Photo-thermal and Photochemical Processes in Gases, pp 85-121, Vol 46 in Topics in Current Physics. Berlin Springer. 

The cross section of a bar is proportional to its mass, thus there are efforts to build a 100-ton spherical resonant de-teetor, with high sensitivity and omnidirectional response. The sphere must be equipped with several transducers to detect the fundamental modes the quadrupole modes and the monopole mode (not sensitive to gravitational waves). Efforts are also being devoted to developing more efficient electronics systems (transducers and amplifiers) to achieve better sensitivity. Another major improvement foreseen is the increase of the bandwidth from the current few hertz to several tens of hertz. In this way, coincident runs could allow the determination of source position. 

M. H. Bartl, S. P. Puls, J. Tang, H. C. Lichtenegger, and G. D. Stucky, 2004, Cubic mesoporous frameworks with a mixed semiconductor nanocrystalline wall stmcture and enhanced sensitivity to visible light, Angew. Chemie Inti Ed. 43, 3037-3040 J. N. Cha, M. H. Bard, M. S. Wong, A. Popitsch, T. J. Deming, and G. D. Stucky, 2003, Microcavity lasing from block peptide hierarchically assembled quantum dot spherical resonators. Nano Letters 3, 907-911... 

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