摘要:

Rayleigh acoustic waves were propagated along the surface of a sheet sample of a Ni alloy while the alloy was undergoing electrolytic charging with hydrogen. The waves were propagated, at frequencies from 2 to 15 MHz, from a transmitting to a receiving transducer, and their attenuation and velocity were monitored. A number of experiments was conducted to ensure that Rayleigh conditions were met and that extraneous results due to such effects as passive film changes and bubble formation were minimal. During cathodic polarization, wave velocity and attenuation decreased. The attenuation decrease followed two stages: an instantaneous one, probably due to polarization effects in the electrolyte, and a gradual one associated with the entry of hydrogen into the alloy. Both the instantaneous and gradual decreases were reversible and were recovered when polarization was removed. The kinetics of the recovery of the gradual component of attenuation were described by the Granato‐Hikata‐Lu¨cke model for unpinning of dislocations by point defects. All results indicated that the surface wave technique was sensitive to hydrogen atom entry into the surface and that the entering atoms migrated to and pinned dislocations within a layer of thickness much less than the Rayleigh wavelength.

ISSN:0021-8979    

DOI:10.1063/1.329066

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The rotational temperature of nitric oxide gas has been measured by means of a single‐beam two‐photon excitation spectrum method using a pulsed continuously tunable dye laser. The nitric oxide gas was enclosed at about 40 Torr in a quartz cell which was put in an electric oven. The NO &ggr; (0‐0) band andR11+Q21branches were used to obtain the two‐photon excitation spectrum. The rotational temperatures were determined using the fact that molecules are distributed in the rotational levels according to the Boltzmann law. The temperature range was from room temperature to about 470 K. Observed temperatures were in good agreement with cell temperatures which were obtained by using a thermocouple.

ISSN:0021-8979    

DOI:10.1063/1.329067

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The recently described transient hot‐strip method has been developed for the study of solids with direction dependent thermal conductivity. By making three independent measurements, with the hot‐strip properly oriented, information can be obtained about the thermal conductivities along the principal directions and also about the specific heat capacity per unit volume. To demonstrate the versatility of the method, crystalline quartz was studied over the temperature range 230–340 K and the results are in good agreement with earlier reported data.

ISSN:0021-8979    

DOI:10.1063/1.329068

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The use of a quadrupole ion trap to catch ions in flight and to trap them for extended periods of time was investigated. The numerical results obtained that storage of ions produced externally is possible in the combined mode, in which suitable radio‐frequency, dc‐electric, and magnetic fields are applied simultaneously. Equations describing the dynamics of the ion motion have been derived and optimum injection conditions were obtained.

ISSN:0021-8979    

DOI:10.1063/1.329069

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Neutron elastic‐scattering reactions are examined by computer simulation and found to be potentially useful as a diagnostic for fuel &rgr;R(density‐radius product). We show how previously anticipated uncertainties can be removed by correlating the distortion of the scattered‐ion distribution with energy loss of DD protons for low &rgr;Rand with D‐He3protons for large &rgr;R. This diagnostic could be used to directly measure &rgr;Rof the fuel without special target preparation for target &rgr;R≲0.2 g/cm2.

ISSN:0021-8979    

DOI:10.1063/1.329070

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

An experimental investigation of the physical processes governing ion extraction from a plasma is presented. The screen hole plasma sheath of a multiaperture ion accelerator system is defined by equipotential plots for a variety of accelerator system geometries and operating conditions. A sheath thickness of at least 15 Debye lengths is shown to be typical. The electron density variation within the sheath satisfies a Maxwell‐Boltzmann density distribution at an effective electron temperature dependent on the discharge plasma primary‐to‐Maxwellian electron density ratio. Plasma ion flow up to and through the sheath is predominately one dimensional and the ions enter the sheath with a modified Bohm velocity. Low values of the screen grid thickness to screen hole diameter ratio give good ion focusing and high extracted ion currents because of the effect of screen webbing on ion focusing.

ISSN:0021-8979    

DOI:10.1063/1.329071

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A method of determining the laser intensity necessary for ionization of atomic states is described. Results are presented for ionization of argon states I–V at 10−4Torr using a short (25 psec)‐pulse neodymium laser at intensities up to 4×1016W cm−2. The results agree with computer calculations of the Keldysh tunneling model in the regime &ggr;⩽1 and with results previously obtained in helium. The electron energy spectra technique employed further verifies the existence of the ponderomotive force.

ISSN:0021-8979    

DOI:10.1063/1.329072

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Stimulated emissions between 12 and 291 &mgr;m have been obtained in14NH3utilizing two‐step and two‐photon excitation. Twelve new lines were observed. A discussion of the parameters available to control the emissions is given.

ISSN:0021-8979    

DOI:10.1063/1.329060

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

New data are presented giving equilibrium ion concentrations in moist air as functions of temperature and humidity. The ions are thought to be decomposition products of neutral water clusters which are found whenever cluster generation mechanisms such as evaporation or combustion are active. The temperature dependence of the ion concentration can be modeled closely by the equilibrium ion product of water. The electrical conductivity of moist air is found to have a quadratic humidity dependence, suggesting that presently accepted electrostatic and insulator theories should be reviewed.

ISSN:0021-8979    

DOI:10.1063/1.329061

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A pointed‐filament‐type field‐emission liquid‐metal ion source is designed and employed as a gold ion source. By adding a crossbar across a hairpin bend, the amount of the gold adhering on the filament is increased. The lifetime is estimated to be over 200 h at 10‐&mgr;A emission current. The emission current increases with increasing extraction voltage up to a saturation value which is ascribed to a limitation of the supply of liquid gold to the needle apex. The value of current density per unit solid angle is 30 &mgr;A/sr at a total current of 30 &mgr;A, which is of the same order as that obtained from a gallium ion source previously reported. Emission current fluctuations of a few tens of percent of the dc component are observed. In order to regulate the emission current and suppress current fluctuations, a bias electrode in addition to a counterelectrode is placed close to the needle apex. With such a triode structure, the emission current is regulated by a bias voltage of several hundred volts and stabilized to within 1% by means of feedback to the bias voltage of a current monitor output.

ISSN:0021-8979    

DOI:10.1063/1.329062

出版商:AIP    

年代:1981

数据来源: AIP