The stored energy released in Stage I recovery of reactor neutron irradiated copper was measured by differential thermal analysis calorimetry for three fluences up to a maximum of 3.5 × 1018 n/cm2 (E>0.1 MeV) after irradiation at temperatures of less than 10 K. The stored energy dependence upon fluence, and a tendency toward saturation, were observed. Theoretical reaction rate processes were compared directly to the experimental rates of stored energy release, and the parameters associated with the theory were compared with results from previous resistivity measurements. Good agreement was found in several parameters, but major differences with previous D + E substage results lead to the conclusion that the point defect model may not describe materials experiencing severe neutron damage. Computer studies of warmup rates were made for first and second order and for correlated recovery processes as a function of defect concentration and of external power input. First and second order processes show definite distortion in their recovery rate curves for high defect concentrations; the correlated recovery process shows a much less pronounced effect. This investigation of stored energy used several new approaches. The use of one sample in both experimental and control roles was not unique, but the use of induced radioactivity within the sample as the heating source, and the use of computer generated theoretical stored energy release curves to analyze the data were unique.

The translational and rotational motions of a cylinder traveling down a straight incline, which provides a constant linear acceleration, depend on the angle of inclination. For small angles above the horizontal, free rolling takes place, but, above a critical angle, rolling and slipping occur. This critical angle is used to evaluate the coefficient of friction for steel cylinders progressing over aluminum surfaces. The moment of inertia is varied by using solid and annular cylinders and the aluminum surface is smooth, rough or corrugated. The coefficient of friction is shown to be independent of the moment of inertia but to depend on the type of surface and the angle of inclination.

A ball that rolls on parallel tracks, whose width is less than the diameter of the ball, experiences both translational and rotational motions. The linear accelerations of the ball for cases of rolling and slipping are derived theoretically, and these accelerations have also been determined by performing experiments when the width and the angular elevation of the tracks are controlled. Data show when slipping occurs for the rolling motion, and the onset of slipping is used to compute the coefficient of kinetic friction for a sphere. A second method of determining the coefficient of friction, for the sphere slipping without rolling, provides confirmation for this analysis.

From measurements made at 4.2 K, the residual resistivity increases produced by reactor irradiation near room temperature were studied in pure Cu up to fluences of 4.2 × 1023n/m2 (E > 1 MeV) and 12 × 1023 thermal n/m2 by methods which resolved the effects due to transmutations and to defects. While the increase in resistivity due to transmutations is linear, that due to defects falls off rapidly with increasing fluence. The defect damage rates at low doses depend upon initial sample conditions that are related to impurities, but they become equal above ~6 × 1021n/m2 (E > 1 MeV). Computations of defect concentrations using these resistivity data and earlier X-ray results [1], which measure dislocation loops, can be brought into reasonable agreement if the specific resistivity attributed to a single defect is decreased when that defect becomes part of a dislocation loop. In addition to the fundamental interest of these results, they also suggest that during the life of certain water-cooled Cu magnets for fusion reactors the resistivity increases due to defects will be small compared to those produced by transmutations.

Reflection of coherent light from a cylindrical glass tubing gives many interference fringes which extend around the tube for more than 180° from the incident beam direction. These fringes have a spacing which varies with angle. The cause of this interference pattern is the superposition of the reflections from the outer and inner surfaces of the cylinder. Excellent agreement is obtained between experimental and theoretical results of the magnitude of the fringe separation as a function of angular direction.

Characteristics of recovery processes have been investigated for cases of heating a sample to successively higher temperatures by means of isochronal annealing or by using a rapid pulse annealing. A recovery spectra shows the same features independent of which annealing procedure is used. In order to determine which technique provides the best resolution, we have studied how two independent first-order processes are separated for different heating rates and time increments of the annealing pulses. It is shown that the pulse anneal method offers definite advantages over isochronal annealing when annealing for short time increments. Experimental data by means of the pulse anneal technique are given for the various substages of stage I of aluminum.

Because the production of Frenkel defects occurs most readily along specific crystallographic directions in fee structures, the recovery mechanism by which annihilation occurs should also be related to the same crystallographic orientations. The recovery path of a diffusing interstitial requires the formation of a temporary meta-stable state as a close-pair Frenkel defect prior to annihilation. A theoretical treatment of this scheme for interstitial-vacancy recombination shows that during the ID diffusion there is an experimentally measurable difference if the recovery forms a IB or a IC close-pair configuration in aluminum. Experimental results are given which show a difference from the theoretical predictions, and it is concluded that the assumed analytical function describing the interstitial-vacancy distribution created by a 0.4 MeV electron irradiation should be modified.

Experimental results from polycrystalline and single crystalline samples of aluminum are analyzed in terms of how electron irradiation causes atomic displacements along 〈100〉 and 〈110〉 crystallographic directions. This interpretation is made for atoms that recoil with energies sliihtly greater than the threshold energy. It is noted that definite correlations exist between some of the substages of stage I and the natural required behavior of recoiling atoms. By applying this criterion to polycrystalline samples, one establishes a means for identifying other phenomena; e.g. multiple atomic displacements, spontaneous recombination, etc.

The threshold energy for atomic displacement in vanadium has been measured to be 26 ± 2 eV. In addition, a preliminary annealing spectrum of the damage induced by 0.5 MeV electrons is presented

Thin copper and platinum single-crystal foils have been irradiated at liquid-helium temperature with electrons of energies between 1 and 3 MeV. From resistivity measurements the directional dependence of the damage rate was determined with high accuracy by varying the orientation of the foils relative to the direction of the beam of the irradiation electrons. From the dependence of defect production on electron energy and foil orientation, the angular dependence of the threshold displacement energy could be determined. In both fcc metals, the closest-packed directions $〈100〉$ and $〈100〉$ possess ring-shaped regions which show minimum threshold values down to 19 eV for copper and 33 eV for platinum, while maximum threshold values are attained near the $〈111〉$ direction. For the electrical resistivity per unit concentration of Frenkel pairs, we obtained (1.7 \ifmmode\pm\else\textpm\fi{} 0.3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ \ensuremath{\mu}\ensuremath{\Omega} cm for copper and (9.5 \ifmmode\pm\else\textpm\fi{} 0.5) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ \ensuremath{\mu}\ensuremath{\Omega} cm for platinum. For copper a comparison with other theoretical and experimental works is possible and shows satisfactory accordance.

physica status solidi (a)Volume 19, Issue 1 p. K31-K34 Short Note Subthreshold radiation effects in platinum R. L. Chaplin, R. L. Chaplin Institut für Festkörperforschung, Kernforschungsanlage Jülich Department of Physics, Clemson University, Clemson S. C. 29631, U.S.A.Search for more papers by this authorP. Jung, P. Jung Institut für Festkörperforschung, Kernforschungsanlage JülichSearch for more papers by this author R. L. Chaplin, R. L. Chaplin Institut für Festkörperforschung, Kernforschungsanlage Jülich Department of Physics, Clemson University, Clemson S. C. 29631, U.S.A.Search for more papers by this authorP. Jung, P. Jung Institut für Festkörperforschung, Kernforschungsanlage JülichSearch for more papers by this author First published: 16 September 1973 https://doi.org/10.1002/pssa.2210190149 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat References 1 F. Dworschak, J. Neuhäser, H. Schuster, J. Wurm, S. Potyka, G. Sokolowski, and H. Wollenberger, Phys. Rev. Letters 16, 685 (1966). 2 G. Duesing, W. Sassin, W. Schilling, and H. Hemmerich, Cryst. Latt. Def. 1, 55 (1969). 3 A. Scholz and Chr. Lehmann, Phys. Rev. B6, 813 (1972). 4 K. Dettmann, Phys. stat. sol. 33, 411 (1969). Volume19, Issue116 September 1973Pages K31-K34 ReferencesRelatedInformation

Damage-rate data for electron-irradiated magnesium samples at 4.2 K have been obtained and analyzed. Since thermally activated recovery occurs at the irradiation temperature, a technique is given which corrects the data for this partial recovery. The corrected damage-rate date are compared with theoretical cross-section calculations involving several probability-of-displacement functions. The isochronal-annealing recovery spectrum is given and is explained in terms of the simultaneous recovery of several close-pair recovery processes.