Parabolic mirrors

Researchers at Satidia National Labs use a trough of parabolic mirrors to focus sunlight on a long glass tube in order to detojdfy water. (U.S. Department of Energy)... 

For a parabolic mirror one conjugate is real and located in front of the mirror, the other is located at infinity. As shown in Fig. 2, light emitted from the one conjugate of the parabolic mirror will focus onto the other conjugate without any additional system aberration. For example, light emitted from an infinitely distant point will come to perfect focus at the finite conjugate. 

So why aren t all teleseopes just a single parabolic mirror The answer is field coverage. A parabolic mirror develops wave-front aberrations as the... 

Figure 2.21. A, High-intensity point source lamp B, parabolic mirror C, light baffle D, narrow slit E, collimating lens F, Coming filters G, reaction cell or series of cells H, focusing lens I, photomultiplier.

Radiation from a xenon or deuterium source is focussed on the flow cell. An interchangeable filter allows different excitation wavelengths to be used. The fluorescent radiation is emitted by the sample in all directions, but is usually measured at 90° to the incident beam. In some types, to increase sensitivity, the fluorescent radiation is reflected and focussed by a parabolic mirror. The second filter isolates a suitable wavelength from the fluorescence spectrum and prevents any scattered light from the source from reaching the photomultiplier detector. The 90° optics allow monitoring of the incident beam as well, so that dual uv absorption and fluorescence... 

As an example of an experimental setup needed for the kind of experiments discussed above, we give now a brief overview of a recent experiment carried out by our group at the SLIC facility at CEA in Saclay (France) [10]. The laser system was the UHI-10 Ti Sa laser, which delivered 65 fs pulses with energy up to 0.7 J. The laser beam was focused by an //5 off-axis parabolic mirror, producing a quasi-gaussian spot where the field parameter ao = c/l aser/mec2,... 

A non-invasive infrared (IK) method has been developed for the measurement of temperatures of small moving fuel droplets in combustion chambers. 7111 The IR system is composed of two coupled off-axis parabolic mirrors and a MCT LWIR detector. The system was used to measure the temperature variations in a chain of monosized droplets generated with equal spacing and diameter (200 pm), moving at a velocity of >5 m/s and evaporating in ambient air. The system was also evaluated for droplet temperature measurements in flames under combustion conditions. 

Solar concentrators contract the solar radiation from a relatively large area onto a small area. A parabolic mirror of four feet in diameter covers an area of 4 pi, or 12.57 square feet (1.17 square meters). This surface area is measured on a plane and is slightly less than the surface area of the curved mirror. If the sun is about 20% down from peak strength, its strength should be about 800 watts per square meter. Then the total amount of energy striking the mirror is almost 1,000 watts. 

A parabolic mirror is used to collect radiation from one focus and deliver a parallel beam... 

A) Parabolic mirror, (B) graphite target, (C) preheater, (D) insulated preheater connectors and (E) glass tube. 

The IR light source is placed in a parabolic mirror in order to concentrate and focus the IR light inside the measurement cell. The chopper wheel, rotating with a well-defined frequency, will modulate the light, generating light-pulses which... 

A landmark project in California is the Mojave Solar Park, which is to be built in the Mojave Desert. When complete, the 6,000 acre will use 1.2 million parabolic mirrors and 317 miles of vacuum tubing to capture the sun s heat, generating 553 megawatts of solar power, enough to support 400,000 homes in northern and central California. The park uses technology developed by Solel Solar Systems of Israel. PG E, a major California utility, will be the major customer when the system comes on line in 2011. 

Figure 17.4 Schematic of the T-jump spectrometer described in the text. OAP, off-axis parabolic mirror PB, Pellin—Broca prism P, polarizer L, lens S, sample MCT, mercury cadmium telluride detector. The size of the pump relative to the probe at the point of overlap is shown in the lower left comer.

In this design, parabolic mirror reflectors (troughs) are used to track the trajectory of the Sun and to concentrate the sunlight onto absorber tubes that are located at the focal line of the parabolic mirrors. Inside the absorber tubes, heat-resistant oil is circulated. This heat-transfer fluid serves to transport the collected heat into boilers that generate steam to drive the turbine generators. 

Other alternative energy applications such as the concentrating parabolic mirror reflector-type solar collectors, where the temperature of the circulated oil can be high, around 900°F (500°C), require high-temperature flow sensors. For these applications, in addition to the head-type flowmeters, noncontacting (e.g., ultrasonic) and metallic tubes, variable-area flowmeters can also be considered. 

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