摘要:

The radial and axial distributions of Cs ground‐state (62S1/2) atoms in Cs&sngbnd;Ar low‐pressure discharges are studied by absorption spectroscopy. The results show that there is appreciable Cs‐atom depletion at the center of the discharge. Within experimental accuracy the Cs(62S1/2) concentration is found to be constant over the whole length of the positive column of the discharge.

ISSN:0021-8979    

DOI:10.1063/1.1658004

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The longitudinal electric field and the electron density and temperature have been measured in the positive column of low‐pressure dc arc discharges in mixtures of cesium and argon at densities around 5×1018and 5×1022m−3, respectively. The measurements have been made with electrostatic probes and with a microwave interferometer. At a low discharge current cesium alone is ionized. When the discharge current is increased the cesium atom density is reduced by ionization and radial diffusion, and at a critical current a discontinuous transition to a state having a high electron temperature is observed. This discontinuity is explained as the result of a multivaluedness of the electric field as a function of the current density. Even at the present low degree of ionization the electron mobility is found to be strongly influenced by Coulomb collisions.

ISSN:0021-8979    

DOI:10.1063/1.1658005

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Poisson's equation, governing space‐charge‐limited flow in a relativistic planar diode, is solved assuming the initial velocities of the accelerated particles are zero, through the use of two power series convergent in the potential range 0≤V≤2m0c2/Zeand 2m0c2/Ze≤V< ∞. In the region of lower potential the solution is expressed in a power series inU, a normalized potential. AsUbecomes small the solution reduces to the well‐known Child's Law. In the region of higher potential, a power series in inverse powers ofUis employed. AsUbecomes large the solution reduces to the ultra‐relativistic form obtained ifv, the particle velocity, can be considered equal to the speed of light. Convergence of both series is rapid, and it is only necessary to retain a few terms to realize a high degree of accuracy.

ISSN:0021-8979    

DOI:10.1063/1.1658006

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The electron energy distribution is obtained for a cesium plasma in a thin region close to the emitter of an ignited‐mode thermionic converter. Assuming that the steady‐state plasma is spatially uniform, the Boltzmann equation with only the electric field and the collision terms is solved by the use of WKBJ method. The collision terms include the elastic, inelastic and electron‐electron Coulomb interactions. A parameterpwhich is proportional to the ratio of the degree of ionization and the electric field, is used to characterize the effect of the electron‐electron interaction on the energy distribution. The stability of the present solution depends on the position of a singular point, a so‐called turning point in the wave equation. The present method gives a stable solution whenp≥3. Whenp<3, the ``turning point'' moves inside the inelastic region, and the equation has multivalued solutions. Thus the present method cannot be applied to those cases with very large induced electric field and small degree of ionization. The solution is examined in various values ofp, and the effect of nonequilibrium ionization in the energy distribution function is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1658007

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The passive analog technique is applied to cyclic glass pressing. Design details of an analog of a plunger‐glass‐mold system are given. The analog is used to provide results on plunger temperature profiles, heat contents, glass temperature gradients near the glass‐mold boundary, and rates of attainment of normal mold running temperature. These results are substantiated by practical pressing machine experience. The method is therefore of use in the assessment and design of glass‐pressing systems.

ISSN:0021-8979    

DOI:10.1063/1.1658008

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The anisotropy of heat conductivity that develops on uniaxial stretching of amorphous high polymers has been examined theoretically and experimentally. Experimental measurements on oriented polystyrenes and polymethylmethacrylates show a linear increase in conductivity (parallel to stretching) with increasing elongation. The slope of the relationship is sensitive to the molecular weight distribution of the polymer and the stretching conditions (temperature). The observations are discussed in relation to current theories of heat conduction in polymers.

ISSN:0021-8979    

DOI:10.1063/1.1658009

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Laser action at 2.7 &mgr; from atomic bromine was produced by flash photolysis of gaseous iodine monobromide. The output consists of a series of sharp pulses having peak powers up to 50 W and a total duration of 5 &mgr;sec. Optical gain was estimated to be ∼1 dB/m. Chemical reversibility of the system is very good; regeneration of the starting material occurs spontaneously and requires about 3 msec. The fact that excited bromine rather than excited iodine atoms are formed leads to clarification of previous conflicting spectroscopic assignments.

ISSN:0021-8979    

DOI:10.1063/1.1658010

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Magnetization measurements were performed on commercial Nb3Sn and Ti&sngbnd;Nb alloy samples to determine hysteretic loss (magnetization vs magnetic field) and flux‐jump stability at 4.2°K in magnetic fields up to 9.3 Wb/m2. The aforementioned superconducting properties were also observed and recorded with various geometries, field sweep rates and thermal environments. The samples consisted of ribbons and/or wires ranging in size from 1.0 to 0.1 cm wide and 0.1 to 0.0001 cm thick. The transport currents ranged from a few amperes to greater than a thousand amperes. These data were obtained utilizing an experimental setup similar to that described by Fietz. The shape and magnitude of the magnetization curves with and without the presence of transport current was not a function of frequency in the range employed, 0.012 to 3.0 Wb/m2·min, except for the multifilament composites. The magnetization and flux‐jump stability was found to be a function of the sample dimensions, as would be expected with the earlier expressions given by Wipf, Hancox, Chester, and Stekly. The transport current density was not a function of the dimensions. These data on magnetization and transport current effects are in accord with earlier work by LeBlanc and co‐workers on Nb&sngbnd;Zr. There is a first principle derivation of the flux‐pinning effects that uses a Josephson junction tunneling model and results in the Kim‐Anderson expression. The internal field distribution could be characterized byHint(x)=(Ha−Hs exp(−x/&lgr;)+Hs,  &lgr;=(Hs−Ha)/Jc(Ha).The exponential expression forJc(Ha) vsHaof Fietzet al.fits the sample data; however, the Kim‐Anderson expression that would be the first term in the expansion of the exponential would also fit the observed data within the experimental error. The data concerning transport current and magnetization can be accurately accounted for (in the infinite sheet configuration) by expressions derived by Yasukochi. The thin plate geometry, with the proper demagnetization factor, is in agreement as well.

ISSN:0021-8979    

DOI:10.1063/1.1658011

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Nuclear magnetic resonance has been employed to identify the phases of the system NbNxin several samples of niobium nitride. The &egr; phase has been identified by a characteristic second‐order quadrupolar broadened central transition with two sets of satellite lines also being observed. The quadrupole coupling constant has been determined for the &egr; phase (e2qQ/h=10.6±0.1 MHz) and for the &dgr; phase (e2qQ/h=4.3±0.4 MHz). The relative amounts of the phases present in a sample were also determined in two samples.

ISSN:0021-8979    

DOI:10.1063/1.1658012

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A general method is given for evaluating currents and coil forces in two‐dimensional magnetic fields. When the field componentsHXandHYare known along a closed contourCin the field planeZ=X+iYand we defineH≡HY+iHX, the total current withinCisC HdZ/4&pgr;iand the total field force per unit length,F≡FY+iFX, acting on all the currents withinCis−C H2dZ/8&pgr;.As an example, the current and coil force are worked out for the uniform field magnet formed by intersecting parallel cylindrical conductors and compared with prior results.

ISSN:0021-8979    

DOI:10.1063/1.1658013

出版商:AIP    

年代:1969

数据来源: AIP