Interstitial-Atom Trapping and Deuterium Localization at 57 Co Impurities in Cu
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INTERSTITIAL-ATOM TRAPPING AND DEUTERIUM LOCALIZATION AT 57Co IMPURITIES IN Cu
C.T. MA, B. MAKOWSKI, M. MARCUSO* AND P. BOOLCHAND Department of Physics, University of Cincinnati, Cincinnati, Ohio
45221
ABSTRACT A high purity Cu target foil doped with 57Co and cooled to 80 K has been deuteron irradiated (E = 2 MeV to .5 MeV) using a Van de Graaff accelerator. In-situ Mbssbauer spectra of the target were taken as a function of deu5 7 terium dose and post irradiation annealing. Two new Co sites are observed in addition to the original substitutional site. The new site 11', populated at low temperature following the irradiations is identified with a 57Co impurity atom having Cu-interstitials trapped in its immediate vicinity. The new site '2', populated on annealing the target above 360 K is believed to represent a 57Co impurity having deuterium localized in its vicinity.
INTRODUCTION Microscopic trapping of elementary defects and defect clusters at solutes in cubic metals has been demonstrated by resonance techniques. In recent years, particular interest has also focussed on the interaction of light interstitial atoms (p,p,d) with defects and solutes in metals. As an example, the localization of p'+at Mn solutes [l] and vacancies [2] in Al host has been recently demonstrated. In this paper, we describe a new experimental method to study the interaction of p and d with defects and solutes in metals. The method utilizes investigating p or d irradiated metal targets using nuclear gamma resonance (NGR or the Mtssbauer effect). We have applied this method to the case of d irradiated Cu and in this paper show that valuable new information on localization of d and trapping of Cu-interstitial clusters at Co solutes in Cu can be obtained.
EXPERIMENTAL We have developed [3] an experimental facility to irradiate target foils cooled to 10 K or 80 K with p or d using a 2-MeV Van de Graaff accelerator. The facility includes a cold-finger assembly forming part of a Janis supervary-temp liquid helium dewar which is mated to the accelerator beam line. Provision for a heater and thermometry on the cold finger is made to vary the temperature of the target. High-purity Cu target foil (Marz grade from Materials Research Corporation) 57 of 61V thickness was doped with Co to prepare a 0.5 mCurie Mtssbauer source. The source exhibited a linewidth of .22(1) mm/s for the inner two lines of Fe taken with a 12.51 thick foil. The target, cooled to 80 K, was subjected to d irradiation at a beam current of 10 vamps and beam energies ranging from 2 MeV to 0.5 MeV. After a total of 5 hours of irradiations during which the beam energy was successively reduced starting from 2 MeV, a total integrated Present address:
Argonne National Lab, Argonne,
Illinois
60439
404 dose of 3.7 x 1017 corrected for secondary electron e.aission, was achieved on the target. NGR spectra of the target were taken with an absorber mounted on a constantacceleration drive. The drive was physically located outside the dewar and at right angles to the accelerator b
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