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DT fusion neutron radiation strengthening of copper and niobium

Description: The initial results of a comparative study of the radiation strengthening and damage structures produced in Cu and Nb by D-T fusion and fission reactor neutrons are described. The radiation strengthening produced by a given fluence of fusion neutrons above about 10$sup 17$n/cm$sup 2$ is equal to that produced by a fluence of fission reactor neutrons (E greater than 0.1 MeV) ten times as great. This difference is about twice as large as would be expected if the strengthening scaled with damage energy or dpa. Initial transmission electron microscopy observations of the damage structures in fusion and fission reactor neutron irradiated copper indicate that the same type of primary structural defects, vacancy and interstitial point defect clusters and small dislocation loops with a/3 (111) and a/2 (110) Burgers vectors, are produced in both cases. The difference in the radiation strengthening produced by fusion and fission reactor neutrons in Cu appears to result from a substantially greater rate of accumulation of damage, in the form of point defect clusters, during irradiation with fusion neutrons than during irradiation with fission reactor neutrons plus a significant difference in the size and spatial distributions of the damage clusters. (auth)
Date: October 30, 1975
Creator: Mitchell, J.B.; Van Konynenburg, R.A.; Echer, C.J. & Parkin, D.M.
Partner: UNT Libraries Government Documents Department

1.06 μm 150 psec laser damage study of diamond turned, diamond turned/ polished and polished metal mirrors

Description: Using a well characterized 1.06 μm 150 ps glass laser pulse the damage characteristics for diamond turned, diamond turned/ polished, and polished copper and silver mirrors less than 5 cm diameter were studied. Although most samples were tested with a normal angle of incidence, some were tested at 45$sup 0$ with different linear polarization showing an increase in damage threshold for S polarization. Different damage mechanisms observed will be discussed. Laser damage is related to residual surface influences of the fabrication process. First attempts to polish diamond turned surfaces resulted in a significant decrease in laser damage threshold. The importance of including the heat of fusion in the one dimensional heat analysis of the theoretical damage threshold and how close the samples came to the theoretical damage threshold is discussed. (auth)
Date: July 24, 1975
Creator: Saito, T. T.; Milam, D.; Baker, P. & Murphy, G.
Partner: UNT Libraries Government Documents Department

Ion radiation damage

Description: From international conference applications of ion beams to metals; Albuquerque, New Mexico, USA (2 Oct 1973). The depth distribution of damage energy deposited in solids by energetic ions was calculated and results are compared with the experimental damage found in copper irradiated with 10 sup 16/ 1-MeV protons at ambient temperature. The general form of the experimental damage profile from the transmission-electronmicroscope measurements agrees well with that calculated. 16 figures, 22 references) (auth)
Date: January 1, 1973
Creator: Oen, O.S.; Narayan, J. & Noggle, T.S.
Partner: UNT Libraries Government Documents Department

Theory of radiation induced defect production

Description: The theory of defect production in solids by neutron irradiation is reviewed, including discussions of the nuclear reactions which produce the primary recoils and the loss of energy from the displacement cascade by electron excitations. The theoretical predictions are compared with the limited available experiments on thermal and fast neutron irradiation. The results are in rough agreement in most instances, but further improvements in the theory are clearly needed. (auth)
Date: October 1, 1975
Creator: Robinson, M.T.
Partner: UNT Libraries Government Documents Department

15 MeV neutron damage in Cu and Nb

Description: An investigation was made of high-energy neutron damage in Cu and Nb irradiated with approximately 15 MeV neutrons at the Oak Ridge Isochronous Cyclotron. The neutrons were generated by bombarding a thick Be target with 40- MeV deuterons resulting in a high energy neutron spectrum broadly peaked at 15 MeV. Single crystals of Cu and Nb were irradiated at room temperature to fluences of approximately 2 x 10$sup 17$ n/cm$sup 2$. The resulting loop-type defect clusters in the crystals were characterized using x-ray diffuse scattering and transmission electron microscopy. The cluster size distributions were found to be generally similar to those characteristic of fission neutron irradiations in these materials and no multiple clusters or sub-clusters were observed. Additional comparisons with fission reactor irradiations in Cu and Nb indicate that the retained displacement damage in these crystals is approximately 3 times greater for the high-energy neutrons than for an equivalent fluence of fission neutrons. This result is consistent with detailed damage energy calculations for the Be(d,n) neutron spectrum. (auth)
Date: January 1, 1975
Creator: Roberto, J. B.; Narayan, J. & Saltmarsh, M. J.
Partner: UNT Libraries Government Documents Department

Nature of defect clusters in electron-irradiated copper

Description: An electron microscope study has been made of the clustering of point defects in electron-irradiated copper in the range of temperatures between Stage III and Stage V. The samples used were single crystals of copper irradiated at 4$sup 0$K with 3 MeV electrons to a dose of 1.4 x 10$sup 19$ electrons/cm$sup 2$. In all of the samples examined the defect clusters were in the form of dislocation loops, mostly less than 100 A in diameter. In samples warmed to room temperature, i.e. slightly above Stage III, the analysis of black-white contrast showed that the loops present were entirely of the interstitial type. In samples annealed at 90 and 150$sup 0$C, the defects were predominantly loops of interstitial type, but approximately 10 percent of the loops were of vacancy type. At 250$sup 0$C, the fraction of the loops of vacancy type increased to about 40 percent but the total loop density decreased markedly. The evidence seems to indicate that in Stage III vacancies do not cluster into sizes large enough to be visible in the electron microscope. (auth)
Date: January 1, 1975
Creator: Ohr, S.M.
Partner: UNT Libraries Government Documents Department

Positron lifetime measurements as a non-destructive technique to monitor fatigue damage

Description: In the fatigue cycling of initially hard copper, self consistent positron lifetime and x-ray particle size measurements followed the softening process and revealed a new feature which may be the final development of microvoids before fracture. In the cyclic fatigue of initially soft 4340 steel closely spaced concurrent measurements of these parameters are now in progress. For initially hard 4340 steel fatigue softening was revealed with a large positron lifetime decrease. In hydrogen embrittlement studies positron lifetime was found to be sensitive to hydrogen in an interesting way, i.e., if a specimen is already at its maximum defect density, hydrogen is trapped at some of the defects, reduce their attraction for positrons and hence cause a decrease in positron lifetime; conversely in a soft specimen, hydrogen generates more dislocation length than it can trap at (thus cancelling) hence a positron lifetime increase occurs. In electron irradiated and annealed single crystal copper 4 annealing peaks were seen at 125, 270, 400, and 650$sup 0$K. A clear correlation between decreasing positron lifetime and increasing percent porosity in $alpha$ alumina was established. This behavior is quite the opposite to that in metals. (auth)
Date: September 1, 1975
Creator: Byrne, J.G.
Partner: UNT Libraries Government Documents Department

DT fusion neutron radiation strengthening of copper and niobium

Description: The initial results of a comparative study of the radiation strengthening and damage structures produced in Cu and Nb by D-T fusion and fission reactor neutrons are described. The radiation strengthening produced by a given fluence of fusion neutrons above about 10$sup 17$ n/cm$sup 2$ is equal to that produced by a fluence of fission reactor neutrons (E greater than 0.1 MeV) ten times as great. This difference is about twice as large as would be expected if the strengthening scaled with damage energy or dpa. Initial transmission electron microscopy observations of the damage structures in fusion and fission reactor neutron irradiated copper indicate that the same type of primary structural defects, vacancy and interstitial point defect clusters and small dislocation loops with a/3 (111) and a/2 (110) Burgers vectors, are produced in both cases. The difference in the radiation strengthening produced by fusion and fission reactor neutrons in Cu appears to result from a substantially greater rate of accumulation of damage, in the form of point defect clusters, during irradiation with fusion neutrons than during irradiation with fission reactor neutrons plus a significant difference in the size and spatial distributions of the damage clusters. (auth)
Date: September 29, 1975
Creator: Mitchell, J.B.; Van Konynenburg, R.A.; Echer, C.J. & Parkin, D.M.
Partner: UNT Libraries Government Documents Department

Neutron damage calculations in Cu, Nb, and Au to 32 MeV: application to sputtering and deuteron-breakup neutron sources

Description: Primary recoil distributions and specific damage energies have been computed for high energy deuteron-breakup neutrons in Cu, Nb, and Au. The calculations are based on theoretical neutron cross sections, and consider in particular a d-Be spectrum broadly peaked at 15 MeV with some neutrons above 30 MeV. The theoretical results are similar to corresponding calculations for monoenergetic 15-MeV neutrons and are in good agreement with range measurements of (n,2n) recoils generated by high energy d-Be neutrons in Nb and Au. The calculations are also consistent with recent d-Be neutron sputtering experiments in Nb and Au and demonstrate the usefulness of deuteron-breakup neutron sources for simulating fusion neutron effects. (auth)
Date: February 1, 1976
Creator: Roberto, J.B.; Robinson, M.T. & Fu, C.Y.
Partner: UNT Libraries Government Documents Department

Ni ion damage in Cu and Nb

Description: Ni ion damage in Cu was studied using x-ray diffuse scattering and transmission electron microscopy, and in Nb using x-ray diffuse scattering. Single crystals of Cu and Nb were irradiated at room temperature to a fluence of 1.2 x 10$sup 13$/cm$sup 2$ at 60 MeV, and Cu was also irradiated to 5 x 10$sup 12$/cm$sup 2$ at 4 MeV. The x-ray diffuse scattering from loop-type defect clusters in the crystals was measured near several Bragg reflections in order to probe the depth distributions of the damage. In Cu, cluster size distributions derived from the x-ray measurements agreed well with TEM results. Comparison with fission reactor irradiations using the damage energy concept suggests similarities in retained damage between the neutron and Ni ion irradiations. (auth)
Date: January 1, 1975
Creator: Roberto, J.B. & Narayan, J.
Partner: UNT Libraries Government Documents Department

Effect of point defects on mechanical properties of metals. Progress report, January 1, 1975--December 31, 1975

Description: Results of research activities are presented on electron irradiation softening in pure Fe, effects of impurities on electron irradiation softening, electron microscopic investigation of electron irradiation softening, surface film softening, and dislocation motion. (JRD)
Date: December 1, 1975
Creator: Meshii, M.
Partner: UNT Libraries Government Documents Department