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Advanced optical diagnostic techniques and instruments are being developed to operate successfully in the high-temperature coal combustion environments of large scale facilities. The success of these instruments depends heavily on maintaining a clear optical path into and out of the gas stream for long periods of time. The buildup of slag at the access port and contaminate fouling of the optical window require special systems to maintain the optical path. The rationale for, and design of, two such systems are presented in this article. The first system, a remotely operated window changer, provides for exchanging fouled windows for clean windows.more » The second system, a remotely operated slagbuster, provides for removing slag buildup in the access port. The design and operation of both systems are discussed. Parts lists, drawings, and schematics are presented also.« less

It is possible, by using alternating-gradient focusing, to design circular accelerators with magnetic guide fields which are constant in time, and which can accommodate stable orbits at all energies from injection to output energy. Such accelerators are in some respects simpler to construct and operate, and moreover, they show promise of greater output currents than conventional synchrotrons and synchrocyclotrons. Two important types of magnetic field patterns are described, the radial-sector and spiral-sector patterns, the former being easier to understand and simpler to construct, the latter resulting in a much smaller accelerator for a given energy. Further, a theory of orbitsmore » in fixed-field alternating-gradient accelerators has been worked out in linear approximation, which yields approximate general relationships between machine parameters, as well as more accurate formulas which can be used for design purposes. There are promising applications of these principles to the design of fixed-field synchrotrons, betatrons, and high-energy cyclotrons.« less

From the basic formulas governing echelle performance, simple expressions for echelle and groove dimensions are derived for producing a two-dimensional echelle spectrogram having any desired characteristics. Several possible mountings of Bausch & Lomb echelles having 200 grooves per inch and resolving powers in the range 200,000 to 500,000 have been tested with the objective of covering as much as possible of the spectral range 2000 to 7000A in a single exposure with high photographic speed. This type of spectrograph is of increasing importance for the analysis of complex spectra of materials available in only minute samples. The mounting thus farmore » found most satisfactory involves making the light from a horizontal slit parallel with an 8-inch concave mirror of 10.5-ft focus, placing the echelle with its grooves horizontal in the resulting collimated beam nearly over the slit, and illuminating a 21-ft concave grating with grooves vertical with the slightly diverging parallel beams from the echelle. The vertical plate factor thus produced on 30 inches of plate set in the focal plane at the grating normal varies from 0.47 A/mm at 7000A to 0.14A/mm at 2000A, and the spectral region from 7000 to 2000A can be covered in a single exposure at such dispersion. The reduction of optical parts to mirror, echelle, and grating gives high speed, so that exposure times of from 20 to 60 sec suffice for most arc spectra. To combine the echelle and grating characteristics effectively, the spectrum below 3600A is made to overlap in the second order of the grating that from 7200 to 3500A in the first. Measured resolving powers vary from 220,000 at 7000A to 450,000 or more at 2537A. Even in complex Zeeman spectra of the rare earths, the statistical distribution of lines is found to be such that little interference results from the partial overlapping of two grating orders. The spectral images are found to be stigmatic and sharp out to 15 inches on either side of the normal to the grating.« less