• K J S Sawhney

      Articles written in Pramana – Journal of Physics

    • Imaging characteristics of toroidal and ellipsoidal mirrors for synchrotron radiation source Indus-1

      K J S Sawhney R V Nandedkar

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      We discuss and compare the imaging characteristics of toroidal and ellipsoidal mirrors for different horizontal acceptances of synchrotron radiation source Indus-1; using a ray tracing method. It has been shown that the toroidal and ellipsoidal mirrors have similar focussing behaviour at small horizontal acceptances. For large horizontal acceptances, toroidal mirror shows an asymmetry in the focussed image. Though the data used here are for Indus-1, the results are generally valid for any bending magnet synchrotron radiation source incident at grazing angles on these mirrors.

    • Optical design of a toroidal grating monochromator based beam line on Indus-1

      K J S Sawhney R V Nandedkar

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      In this paper, we discuss the detailed optical design of a beam line that is under construction on the synchrotron radiation source, Indus-1. Toroidal mirrors are used as pre-and post- focusing elements and a toroidal grating monochromator as a dispersing element. Using three interchangeable gratings, this monochromator will give, at a moderate resolution, a good throughput on the sample in the wavelength range 40 to 1000 Å. Effect of various parameters and their optimization on the resolution and throughput characteristics have been studied by ray tracing calculations, and presented.

    • Use of spherical gratings in a toroidal grating mount for vuv-soft x-ray synchrotron radiation

      K J S Sawhney A I Munshi R V Nandedkar

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      A toroidal grating monochromator (TGM) based beamline was designed earlier and it is being setup on the 450 MeV Indus-1 synchrotron radiation source. This beamline operates in 40–1000 Å wavelength range and gives a moderate resolution (∼500) at high throughput. Now-a-days, spherical gratings are giving very high resolution in some complex monochromators. We have evaluated the use of spherical gratings in the simple rotation mount of a TGM. The motivation has been to evaluate if the existing TGM beamline, without any hardware changes, can be used with the much cheaper spherical gratings. The two monochromators, employing toroidal and spherical gratings respectively, have been compared by performing detailed ray tracing calculations. Our study shows that, with the same mechanical hardware, a real spherical grating monochromator gives better performance compared to the conventional TGM with respect to the spectral resolution and the flux. Furthermore, for moderate resolution this improvement is realized even when the exit slit is not moved to keep the spherical grating in-focus.

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