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Nature of conduction in thorium oxide single crystals
NOTES FROM THE BARTOL RESEARCH FOUNDATION W. F. G. SWANN, DIRECTOR
NATURE OF CONDUCTION IN THORIUM OXIDE SINGLE CRYSTALS * BY W. E. DANFORTH AND J. H. BODINE
R e c e n t considerations relative to the theory of p h e n o m e n a in mixed conductors have led us to the view that, in a fresh unpolarized unactivated crystal of t h o r i u m oxide, the conduction takes place almost entirely by ions. The considerations referred to have to do with the analysis of the polarization curve. Letting E0 be the emf. which appears when a constant current is applied, and E . the final emf. which exists as a result of polarization, it appears t h a t the fraction of current carried by electrons should be, in the limit of small currents, Eo/E,. This is found experimentally to be a q u a n t i t y less t h a n 1 per cent. The high electronic conductivity observed in polycrystalline thoria aggregates, as used in electron tube cathodes, m u s t be understood as resulting from the presence of electrolytically produced thorium. * Assisted by the U. S. Office of Ordance Research and the U. S. Navy Bureau of Ships. INELASTIC SCATTERING OF 14 MEV NEUTRONS * BY G. W. McCLURE AND D. W. KENT
T h e Bartol 100 Kev Cockcroft-Walton accelerator now produces a flux of 2 X 108 14 Mev neutrons per sec via the H3(H ~, n)He 4 reaction. A scintillation counter built into the target chamber acts as an indicator of the absolute neutron yield by counting the He 4 recoils from the target. Experimentation thus far completed has consisted mainly of inelastic scattering measurements on the Fe nucleus. The 7'-ray spect r u m resulting from the neutron b o m b a r d m e n t of an Fe scattering sample (natural isotope mixture) shows discrete -y-rays at 0.850, 1.25, 1.82 and 2.12 Mev all of which correspond to transitions between known levels in the 92 per cent a b u n d a n t Fe 56 isotope. The production cross sections for the two lower energy 7'-rays are approximately 0.75 and 0.26 barn, respectively. An investigation of the 2.57-hr. Mn 5~ activity induced in the Fe scatterer by neutron b o m b a r d m e n t indicates a cross section of 72 millibarns for the reaction Fe58(n,p)Mn 56. All of the cross sections listed are accurate to about + 10 per cent. F u r t h e r inelastic scattering work employing n-~, coincidence measurements are currently in progress. • Assisted by the U. S. Atomic Energy Commission. 238
NATURE OF CONDUCTION IN THORIUM OXIDE SINGLE CRYSTALS * BY W. E. DANFORTH AND J. H. BODINE
R e c e n t considerations relative to the theory of p h e n o m e n a in mixed conductors have led us to the view that, in a fresh unpolarized unactivated crystal of t h o r i u m oxide, the conduction takes place almost entirely by ions. The considerations referred to have to do with the analysis of the polarization curve. Letting E0 be the emf. which appears when a constant current is applied, and E . the final emf. which exists as a result of polarization, it appears t h a t the fraction of current carried by electrons should be, in the limit of small currents, Eo/E,. This is found experimentally to be a q u a n t i t y less t h a n 1 per cent. The high electronic conductivity observed in polycrystalline thoria aggregates, as used in electron tube cathodes, m u s t be understood as resulting from the presence of electrolytically produced thorium. * Assisted by the U. S. Office of Ordance Research and the U. S. Navy Bureau of Ships. INELASTIC SCATTERING OF 14 MEV NEUTRONS * BY G. W. McCLURE AND D. W. KENT
T h e Bartol 100 Kev Cockcroft-Walton accelerator now produces a flux of 2 X 108 14 Mev neutrons per sec via the H3(H ~, n)He 4 reaction. A scintillation counter built into the target chamber acts as an indicator of the absolute neutron yield by counting the He 4 recoils from the target. Experimentation thus far completed has consisted mainly of inelastic scattering measurements on the Fe nucleus. The 7'-ray spect r u m resulting from the neutron b o m b a r d m e n t of an Fe scattering sample (natural isotope mixture) shows discrete -y-rays at 0.850, 1.25, 1.82 and 2.12 Mev all of which correspond to transitions between known levels in the 92 per cent a b u n d a n t Fe 56 isotope. The production cross sections for the two lower energy 7'-rays are approximately 0.75 and 0.26 barn, respectively. An investigation of the 2.57-hr. Mn 5~ activity induced in the Fe scatterer by neutron b o m b a r d m e n t indicates a cross section of 72 millibarns for the reaction Fe58(n,p)Mn 56. All of the cross sections listed are accurate to about + 10 per cent. F u r t h e r inelastic scattering work employing n-~, coincidence measurements are currently in progress. • Assisted by the U. S. Atomic Energy Commission. 238