No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
A High Resolving Power, Curved‐Crystal Focusing Spectrometer for Short Wave‐Length X‐Rays and Gamma‐Rays
1.J. W. DuMond and H. A. Kirkpatrick, “Multiple crystal x‐ray spectrograph,” Rev. Sci. Inst. 1, 88 (1930), see Fig. 2.
2.H. H. Johann, Zeits. f. Physik 69, 185 (1931).
3.Y. Cauchois, Comptes Rendus 194, 1479 (1932);
3.Y. Cauchois, Comptes Rendus 194, 362 (1932); , Compt. Rend.
3.Y. Cauchois, Comptes Rendus 199, 857 (1934); , Compt. Rend.
3.Y. Cauchois, J. de Phys. et Rad. 3, 320 (1932);
3.Y. Cauchois, J. de Phys. et Rad. 4, 61 (1933); , J. Phys. Radium
3.Y. Cauchois, Ann. de Physique 1, 215 (1934).
4.Spectrometers using bent crystals such as mica had been built and used prior to 1927. These were not focusing spectrometers, however, with two conjugate foci (real or virtual). One of these, for example, consisted of a sheet of mica rolled around a cylinder upon which an x‐ray beam, propagating at right angles to the axis of the cylinder fell in nearly tangential incidence so as to be reflected from the convex mica surface. The advantage gained was the elimination of the necessity for rocking the crystal or the source. No gain in luminosity was attained. Another early suggestion was to bend a mica sheet about a cylindrical surface having as its base profile a logarithmic spiral. The origin of the spiral would then certainly give one required focal point, but there is no corresponding conjugate focal point. Instead there is a caustic. This fact affords another way of perceiving the incompatibility of the two conditions imposed by Bragg reflection when applied to the cleavage surface of a bent mica crystal. A third type of bent‐crystal spectrometer which does have two conjugate foci and which affords considerable luminosity consists in a crystal such as mica rolled into a hollow cylinder which reflects the x‐rays from its internal concave surface. If the source of x‐rays is placed on the axis of this cylinder, a monochromatic point image will be formed elsewhere on the same axis. The mica surface may also conform to a hollow conical frustum. The geometry of the focusing is rather disadvantageous for photographic spectroscopy. P. Kirkpatrick has developed a very luminous monochromator in which this kind of focusing is combined with the Johann‐type of focusing (our case R of Fig. 2). Rocksalt crystals are deformed to a barrel‐shaped surface to obtain this result.
5.Others, however, have succeeded in building curved‐crystal spectrometers of the exact focusing type by suitably profiling the crystal lamina in its unstressed state to the required curvature, twice the radius of the focal circle, and then bending it until the spectra focus on the focal circle. See A. Guinier, Ann. de Physique 12, 161 (1939),
5.and R. Bozorth and F. E. Haworth, Phys. Rev. 53, 538 (1938).
6.Others who have worked with curved‐crystal spectrometers are J. W. M. DuMond and B. B. Watson, Phys. Rev. 46, 316 (1934);
6.J. W. M. DuMond and B. B. Watson, Rev. Sci. Inst. 8, 480 (1937);
6.I. Johansson, Zeits. f. Physik 82, 507 (1933);
6.P. Abelson, Phys. Rev. 56, 753 (1939);
6.E. Ingelstam, Rev. Sci. Inst. 11, 160 (1940);
6.J. E. Edwards, M. L. Pool, and F. C. Blake, Phys. Rev. 67, 150 (1945).
7.The material is a heat‐treatable stainless steel having the composition Cr 13.5 percent, C 0.35 percent, Mn 0.40 percent, Si 0.50 percent. It is obtainable from either Firth‐Sterling or Allegheny Ludlum Steel Companies.
8.Compton and Allison, X‐Rays in Theory and Experiment (D. Van Nostrand Company, Inc., New York, 1935), p. 746.
Article metrics loading...
Full text loading...
Most read this month
Most cited this month