484 THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1951 



samples were used in order to avoid electromagnetic cavity- type resonances. 

 The g-f actor observed is 2.19. The first-order magnetocrystalline anisotropy 

 constant Ki was found so be —6.27 X lO'* ergs/cc. The absorption line was 

 very narrow (half-widths less than 100 oersteds) and fit a resonance curve 

 quite satisfactorily. 



Two Comments on the Limits of Validity of the P. R. Weiss Theory of Ferro- 

 magnetism. P. W. Anderson.^ Letter to the editor. Phys. Rev., v. 80, pp. 

 922-923, Dec. 1, 1950. 



Television Picture Fidelity. M. W. Baldwin, Jr.^ Electronics, v. 24, pp. 

 106-107, Jan., 1950. 



Abstract — Consideration of the various factors involved in the physics 

 of image formation on a television picture tube, and discussion of inherent 

 limitations and attributes of the overall system and its production 

 techniques. 



Changes in Conductivity of Germanium Induced hy Alpha-Particle Bombard- 

 ment.* W. H. Brattain^ and G. L. Pearson.^ Phys. Rev., v. 80, pp. 846-850, 

 Dec. 1, 1950. 



Abstract — ^The bombardment of n-type germanium by alpha-particles from 

 polonium first removes the conducting electrons at the rate of 78 per alpha- 

 particle. After the electrons are gone conducting holes are introduced at the 

 initial rate of 8.6 per alpha-particle. Some of these holes disappear with 

 time at room temperature after bombardment is stopped, leaving only two 

 conducting holes per alpha-particle. This change takes place only to the 

 depth of penetration of the particles, namely 1.9 X 10~^ cm. The distribution 

 of holes with depth is not uniform. The concentration rises from an initial 

 value to a maximum at 1.4 X 10~^ cm depth and then falls to zero. The maxi- 

 mum is about 2.5 times the initial value and the integral under the curve is, 

 of course, two holes per alpha-particle. 



Experimental Verification of Space Charge and Transit Time Reduction 

 of Noise in Electron Beams.* C. C. Cutler^ and C. F. Quate.* Phys. Rev., 

 v. 80, pp. 875-878, Dec. 1, 1950. 



Abstract — This paper describes a simple experiment which indicates some 

 significant properties of the noise currents in a long electron stream, and veri- 

 fies the applicability of the theory as worked out by Rack, Peterson, and 

 Pierce to the noise properties of klystrons and traveling-wave tubes. An 

 appendix shows that the observations are reasonably consistent with the 

 theory. 



* A reprint of this article may he obtained on request to the editor of the B. S. T. J. 



1 B. T. L. 



» A. T. & T. Co. 



