Letter | Published:

Paraffin Mirrors for Ultrasoft X-rays

Naturevolume 214pages263265 (1967) | Download Citation



OUR search for a suitable dispersion technique to identify ultrasoft X-radiation (wavelength λ>20 Å) led us to consider the wavelength dependence of the critical angle of total reflexion. A critical angle of total reflexion exists only if the reflector is transparent to radiation. Thus, one reason for the unsatisfactory results reported by Franks and Braybrook1 could be the high absorption of the ultra-soft X-rays in the beryllium reflector used by these authors. At first glance beryllium is the best choice for a low-absorption reflector, but commercial beryllium is contaminated by heavy metals. Even a small proportion of, say, iron or nickel, combined with the beryllium oxide that always forms on the surface where total reflexion occurs, can destroy the critical angle.

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  1. Engineering Physics Laboratory, Engineering Department, E. I. du Pont de Nemours and Co., Inc., Wilmington, Delaware

    • H. K. HERGLOTZ


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