摘要:

The microstructure of Vanadium irradiated to a fluence of 1.0 × 1019n/cm2E< 1 MeV at a temperature of 55 °C was quantitatively analyzed after irradiation and post-irradiation annealing and correlated with changes in the strength as determined from microhardness measurements. Radiation anneal hardening during Stage III annealing was not accompanied by a change in the size or number of defect aggregates. It is shown that the strength changes and migration kinetics of Stage III are consistent with the migration of oxygen and/or carbon to the defect aggregates. It is suggested that the simultaneous observation of no growth of defect aggregates and radiation anneal hardening in Stage III can be used to differentiate between impurity migration and intrinsic defect migration.

ISSN:0033-7579    

DOI:10.1080/00337577108231087

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

A simple cryostat for annealing spectra measurements in the temperature range 78 to 700 °K is described and its specifications are given. The rise time at the annealing temperature is chosen equal to 1.5 minutes, giving thus, a practically square shape of the temperature pulse. An analogue valve regulates automatically a stream of cold nitrogen gas and maintains the temperature of the samples constant within ±0.05 °C. The rise time varies from 1 min, or even less, to about 7 min, when there is no control of temperature through the cold gas.

ISSN:0033-7579    

DOI:10.1080/00337577108231088

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Polycrystalline and ⟨100⟩-oriented single-crystal wires of high-purity platinum have been irradiated with 2.5-MeV electrons at ∼20 K and above liquid-nitrogen temperature. Following each irradiation, measurements of the logarithmic decrement were taken as a function of temperature. In general, the irradiations resulted in pronounced pinning and depinning effects as well as anelastic effects due to the irradiation-produced interstitials alone. The former are interpreted as, on the one hand, pinning of dislocations by interstitials which arrive at the dislocations and are immobilized, and on the other hand, the annihilation of pre-existing vacancy pinners by interstitials that become mobile on the dislocations. Aa increase in the decrement at a temperature of ∼75 K was observed in both samples, and this increase is related to the onset of interstitial pipe diffusion which brings about the mutual annihilation of the interstitial and vacancy pinners. In addition to some structure in the background, a reorientation peak attributed to anelastic reorientations of interstitial-type defects was observed at ∼38 K. The excessive width of the observed peak suggests a spectrum of activation energies associated with the peak. From the results of our experiments we assert that conclusions based upon pinning rates must take into account the possible interaction between newly arrived interstitial pinners and pre-existing vacancy pinners. These interactions will be temperature dependent and may profoundly influence low-flux, low-fluence irradiation experiments.

ISSN:0033-7579    

DOI:10.1080/00337577108231089

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

A silicon (111) surface was bombarded in U.H.V. with low energy (≤1 keV) He+and Kr+ions. The ions retained within the solid were subsequently desorbed into a closed volume, by raising the target temperature linearly, with respect to time, at a rate of 30°KS−1. The differentiated signal in a mass spectrometer provided desorption spectra.

ISSN:0033-7579    

DOI:10.1080/00337577108231090

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Radiation damage and annealing studies of copper samples have been performed for the near threshold energy region. A nonlinear behavior of the damage rate vs. irradiation fluence is found. This effect is related to damage which does not anneal below 300 K and is independent of subthreshold damage.

ISSN:0033-7579    

DOI:10.1080/00337577108231091

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

High-purity zone refined specimens of cadmium were irradiated at liquid helium temperature with electrons in the energy range 0.5–1.7 MeV. From the measurements of the electrical resistivity change rate per incident electron and from an analysis of the recovery spectra up to ∼ 200 °K we deduce that two simultaneous processes are acting under electron bombardment. The first—a subthreshold process—is of a complicated nature and thought to be due to the interaction of the bombarding electrons with very small amounts (∼ 10−7per atom) of hydrogen atoms loosely bound to traps, their binding energy being of the orderTs∼ 10−1eV. The second is the cadmium atom displacement proper, with an energy threshold ofTd= 19±2 eV.

ISSN:0033-7579    

DOI:10.1080/00337577108231092

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Estimates of the depth of bombardment-induced amorphization (Ra) are presently available for seven different ions injected into Si (Ar, As, B, Ne, P, Sb and Si) as well as for Kr injected into WO3. These depths can be interpreted in terms of recent damage-distribution theories to yieldFd(Ra), theinitialdisplacement fraction at depthRa. (Here the term ‘initial’ means ‘present before thermal and athermal annealing’.) The resulting values ofFd(Ra) were found to be reasonably constant, such that, depending on which theory was used, they had an average of either 0.7 ±0.2 or 0.4 ±0.2 for Si and either 0.09 ±0.03 or 0.17 ±0.06 for WO3. This approximate constancy is considered to be particularly significant with Si, since the data used encompassed incident masses from 11 to 122, incident energies from 10 to 280 keV, and doses from 3 × 1014to 1 × 1014ions/cm2. It is concluded, in view of the constancy ofFd(Ra), that the amorphization of si and WO3can be self-consistently explained by homogeneous damage accumulation. An alternative category of explanation, based on the random impingement of discrete disordered regions of volumeVais, however, not excluded; in fact, it is argued that the constancy demonstrated here forFd(Ra) is also compatible with discrete disordered regions providedVais proportional to the incident energyE.

ISSN:0033-7579    

DOI:10.1080/00337577108231093

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Gamma-irradiation of KF. 2H2O and KF. 4H2O crystalline hydrates at low temperatures results in the appearance of colour centres. The characteristics of optical spectra of these centres at 77 °K are: λmax= 475 nm andW1/2= 0.58 eV for KF. 2H2O; λmax= 480–485 nm and W1/2= 0.62 eV for KF. 4H2O. The EPR spectrum of colour centres is an isotropic singlet withg-factor 2.001 andΔH= 34.5 Oe (for KF. 2H2O at 77 °K). Their yields are low (0.015 and 0.0055 particles/100 eV for KF. 2H2O and KF. 4H2O at 77 °K, respectively). The kinetics of their accumulation at γ-irradiation as well as the kinetics of thermal and photostimulated decay has been investigated. On the basis of the data obtained it has been concluded that the colour centres in crystalline hydrates investigated are similar in their nature toF-centres in alkali halide crystals but differ from trapped electrons in glassy aqueous solutions.

ISSN:0033-7579    

DOI:10.1080/00337577108231094

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The energy dependence of low dose damage production in commercial and high purity polycrystalline tungsten wires was studied near 350 K with 1.6 to 2.4 MeV electrons. From resistivity measurements at 291 K the threshold energy for the onset of observable damage was determined as 50 × 2 eV. An ‘effective’ threshold of 52 ±2 eV was also determined by directly fitting the energy dependence of the damage rates to theoretical displacement cross sections calculated from step-function displacement probabilities. A decrease of two orders of magnitude in impurity content reduced damage rates by about a factor of two but did not affect threshold. These results combined with current defect recovery models for tungsten, low temperature threshold data, and computer-calculated bcc damage theory suggest: (1) Observed damage consisted of equal concentrations of vacancies and impurity-trapped Stage I free interstitials. (2) Across Stage II (100 K to 600 K) onset threshold should be within 50 ±2 eV. (3) Minimum recoil energy required for free interstitial production near 0 K is 53 ± 5 eV. (4) Threshold has little dependence on crystal direction. An empirical method is presented for predicting threshold energies in the bcc transition metals by assuming the directional dependence of threshold is directly proportional to that of Young's modulus. By the use of one universal proportionality constant (1.2 × 10−11eV.cm2/dyne), thresholds for a number of metals and directions are calculated and shown to have significantly better agreement with experiment than the best available theoretical estimates.

ISSN:0033-7579    

DOI:10.1080/00337577108231095

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Scattering Theory (Aspects of Scattering Processes in Atomic, Nuclear and Particle Physics)Edited by A. O. Barut Gordon and Breach Science Publishers Inc., 1969, pp. viii + 431.

ISSN:0033-7579    

DOI:10.1080/00337577108231096

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor