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Theory of High Frequency Rectification by Silicon Crystals

Description: The excellent performance of British ''red dot'' crystals is explained as due to the knife edge contact against a polished surface. High frequency rectification depends critically on the capacity of the rectifying boundary layer of the crystal. C. For high conversion efficiency, the product of this capacity and of the ''forward'' (bulk) resistance R{sub b} of the crystal must be small. For a knife edge, this product depends primarily on the breadth of the knife edge and very little upon its length. The contact can therefore have a rather large area which prevents burn-out. For a wavelength of 10 cm. the computations show that the breadth of the knife edge should be less than about 10{sup -3} cm. For a point contact the radius must be less than 1.5 x 10{sup -3} cm. and the resulting small area is conductive to burn-out. The effect of ''tapping'' is probably to reduce the area of contact.
Date: October 29, 1942
Creator: Bethe, H.A.

Effect of Tensor Range in Nuclear Two-Body Problems

Description: The interaction between neutron and proton in the triplet state has been investigated. The central and tensor potentials have been assumed to be of the ''meson'' type but of possibly different ranges. The variational-iterational method has been utilized to determine V{sub o}, the strength of the central potential, and {gamma}V{sub o}, the strength of the tensor potential. A wide variation in the values of both central and tensor ranges were included. Calculations of this type have proved difficult in the past principally because of the sensitivity of the results to the quadrupole moment Q of the deuteron for which accurate wave functions are necessary. It would be desirable to have a more accurate value of Q deduced from experiment. The percent D state in the deuteron and the effective triplet range have also been computed. The results are applied to the discussion of the magnetic moment of the deuteron, the photoelectric disintegration of the deuteron, and neutron-proton scattering. It is concluded that experimental information on neutron-proton interaction at their present accuracy does not determine the range of the tensor forces except within rather broad limits. A decrease in the uncertainty in the triplet range by an order of magnitude would be required. Finally it is concluded that charge independence of nuclear forces can be maintained with the meson well.
Date: November 1, 1949
Creator: Feshbach, H.; Schwinger, J. & Harr, J.A.


Description: Methods are developed for estimating the effect on a critical assembly of fabricating it as a lattice rather than in the more simply interpreted homogeneous manner. An idealized case is discussed supposing an infinite medium in which fission, elastic scattering and absorption can occur, neutrons of only one velocity present, and the neutron m.f.p. independent of position and equal to unity with the unit of length use. (auth)
Date: August 27, 1946
Creator: Welton, T.A. & Feynman, R.P.