摘要:

The variation of the thermal conductivity of uranium‐impregnated graphite is measured continuously while under neutron irradiation. The temperature is continuously monitored and results are reported which show the effects of the uranium oxide particle size as well as the effect of the neutron bombardment as separated from the fission recoil bombardment.

ISSN:0021-8979    

DOI:10.1063/1.1735099

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A method for measuring the resistivity of metallic specimens is described. The measurement is made by noting the rate of decay of flux from a bar situated in an external magnetic field that has been rapidly reduce to zero. The method is suitable for specimens greater than 5×10−3cm in diameter. For a specimen 1 cm in diameter, resistivities from 10−11to 10−3ohm‐cm may be measured with an error of less than three percent. The method requires no contact to the specimen, and local values of resistivity may be measured. Several applications are described.

ISSN:0021-8979    

DOI:10.1063/1.1735100

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A set of small‐area, alloy,p‐njunction diodes was made from a slice of heat‐treatedn‐type silicon. The carrier lifetimes of the diodes were found to be in the range of 2.5×10−8sec to 3.5×10−6sec. Measurements were made of the lifetime and of the current‐voltage characteristics in the forward and reverse directions as a function of temperature from room temperature to 165°C. An analysis of the results and, in particular, the correlation of current flow with lifetime values, showed that for the diodes with the shortest lifetimes, centers situated 0.48 ev at 0°K from either the conduction or valence bands were responsible for large space‐charge currents. For the diodes with lifetimes in the microsecond range, surface leakage currents were predominant. Evidence was found of a field‐dependent emission probability, &bgr;, for these centers. The results showed that &bgr;∼E0.35whenE, the electric field, is in the range of 2×104to 8×104v/cm.

ISSN:0021-8979    

DOI:10.1063/1.1735101

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Phase‐detection techniques used in recording magnetic resonances are the source of a measurement broadening. Results of a general mathematical treatment for arbitrary line shape and of machine computation for a Lorentz line shape lead to a series of curves which may be used to correct observed widths under circumstances where the Lorentz shape may be verified and effects of finite modulation frequency may be ignored.

ISSN:0021-8979    

DOI:10.1063/1.1735102

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Temperature diffuse scattering of x‐rays (TDS) has been examined in cubic powders to test the reliability of current TDS theory. Measurements are reported of the diffuse scattering of copper and lead along with the Bragg reflections of these metals at room and liquid nitrogen temperatures. These measurements were made using a scintillation counter diffractometer and crystal monochromated CuK&agr; radiation. The TDS so otained is compared with TDS calculations based on the one‐ and two‐phonon calculation as well as on the Warren (modified one‐phonon) calculation. Both formulas are found to fit the magnitude of TDS by choosing appropriate Debye characteristic temperatures. The Debye &THgr;'s which fit the copper and lead TDS data at room temperature are: 324° and 96° (one‐ and two‐phonon) and 269° and 64° (Warren formula) as compared to values of 307° and 79° taken from the temperature dependence of the Bragg reflections and 315° and 88° from specific heat values for copper and lead, respectively. Evidence is also found for extra diffuse scattering in the low‐angle region. This extra scattering is tentatively ascribed to a multiple scattering process.

ISSN:0021-8979    

DOI:10.1063/1.1735103

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

In order to obtain accurate values for the integrated Bragg intensities, it is necessary to correct for the fact that temperature diffuse scattering (TDS) peaks in the same regions of reciprocal space in which Bragg peaks occur. On the basis of recent calculation of TDS in cubic powders it is possible to calculate the contribution of TDS to apparent measured Bragg intensities. Measurements were made on a counter spectrometer using crystal‐monochromated CuK&agr; radiation. The contribution of TDS to the measured Bragg intensities is demonstrated on several peaks of lead. A simple relationship is derived for the correction and compared with a graphical solution obtained by plotting TDS under the Bragg peak. The agreement between the two methods of correcting for TDS is good. The magnitude of the correction varies with the material, the wavelength of the x‐rays and the region of reciprocal space studied. For a typical material such as copper using copper radiation, the correction is about 3% of the integrated intensity. For lead, again using copper radiation, it is about 15%.

ISSN:0021-8979    

DOI:10.1063/1.1735104

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Dislocation‐free Ge crystals of 50 g weight have been grown from the melt by the Dash technique. We have diffused Cu into slabs of these crystals for 0.5 to 2 hr at 700–850°C. Acceptors with an ionization energy indistinguishable from that of the lowest substitutional Cu level were observed. Their concentration ranged from ∼0.5×1015/cm3for samples taken from the tops of crystals to ∼3×1015/cm3for samples from near the bottom. Insufficient time was available for the dissociative diffusion of substitutional Cu into the interior from the surface to account for the observed acceptor concentrations. The data may, however, be interpreted as indicating that vacancies trapped into the crystal during normal growth combine with rapidly diffusing interstitial Cu atoms to make substitutional Cu atoms. According to this interpretation, the data show that the concentration of vacancies trapped into the bottom of a dislocation‐free Ge crystal is larger than at the top, presumably as a consequence of the heat treatment the crystal receives during normal growth. The vacancy concentration at the melting point is 2.9–3.9×1015/cm3, on this model. Methods of altering the vacancy content of the crystals by further heat treatment are discussed. Some experimental details of Cu diffusion into dislocation‐free Ge are given in an Appendix.

ISSN:0021-8979    

DOI:10.1063/1.1735105

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1735106

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1735107

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1735108

出版商:AIP    

年代:1959

数据来源: AIP