摘要:

This is an extension of the work carried out by Gibson and Caldwell on the optimization of the uniformity of the magnetic field produced in the bore of a toroidal conductor of rectangular cross section. In this paper the work is extended to consider the magnetic field due to a number of conductors. The usefulness of the work is assessed by comparing it to the work of Garrett, and numerical results are given for particular coil parameters.

ISSN:0021-8979    

DOI:10.1063/1.330632

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

We optimize the operating conditions of a model internal combustion engine to obtain maximal efficiency. The model engine consists of a cylinder equipped with a piston containing a working fluid, coupled to a heat bath and heated by internal combustion with a rate of heating that is very weakly dependent on the temperature and pressure of the working fluid. We consider operation of the piston under the influence of an external pressure. The model engine includes valves allowing the exhaust and intake of the working fluid. It is found that the optimal operation has an optimal compression ratio and an optimal energy to be exhausted with the working fluid. The results are demonstrated with a numerical example. Also presented are optimizations for this system of the average power, and optimization of the work for a given specified average power.

ISSN:0021-8979    

DOI:10.1063/1.330633

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Single‐crystal lanthanum hexaboride (LaB6) rods 1 mm in diameter by more than 150 mm in length have been fabricated by the laser‐heated floating zone process. The procedure is described and the effects of process parameters such as power input and pulling and feeding rates on the geometry of the molten zone and on the quality of the grown rods are discussed. By seeded growth, the orientation of the rod axis can be selected; crystals having a rod axis corresponding to ⟨100⟩, ⟨110⟩, ⟨111⟩, ⟨210⟩, ⟨211⟩, and ⟨321⟩ were prepared during this study, each with a uniform diameter and having high crystalline quality. These crystals have been used for evaluating the performance of the indirectly‐heated‐type LaB6rod cathode. An electron optical test column allows the angular emission pattern, the crossover intensity distribution, the tip temperature, and the on axis brightness of the cathode to be observed and measured. Symmetries in the angular emission and the crossover are related to the LaB6lattice structure, and these patterns are accurately reproducible. At operating temperatures of 1800 K, the angular emission is smooth and the crossover a uniform round spot. Brightness measurements of the six different orientations show that the brightness increases with increasing temperature and eventually levels off to a space‐charge limitation. The use of ⟨100⟩‐oriented rod cathodes with a cone tip of less than 2 &mgr;m radius gives the best results and an increase in brightness of a factor of about three as compared to sintered material of the same geometry can be achieved.

ISSN:0021-8979    

DOI:10.1063/1.330634

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Ray tracing techniques are used to derive an analytic approximation for the resolving power, &lgr;/&Dgr;&lgr;, of convex curved crystal spectrographs as a function of the linear source size parallel to the plane of dispersion and as a function of the Bragg angle. Using the derived expression, we investigate source size broadening in spectra from spatially and temporally integrated imploding‐wire plasmas. We also compare the level spacing between the last discrete spectral line and the spectral line succeeding it to various line broadening processes: line broadening due to the finite size of the plasma source (source size line broadening), Doppler broadening, and line broadening due to the crystal rocking curve. We show that, in some cases, source size line broadening is comparable to the level spacing. Source size line broadening causes difficulties in obtaining the ion density from the series merging technique, since the latter is based on Stark broadening. We show that in some previously reported experiments the ion densities determined from the series merging technique should be considered an upper limit.

ISSN:0021-8979    

DOI:10.1063/1.330635

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

We report a systematic ion microprobe study of the isotope fractionation effects produced during the sputtering of pure metal targets. The metals studied were B, Mg, Si, Cr, Ni, Cu, Ge, Mo, Ag, Sb, Re, Tl, and Pb; isotopic ratios were determined with typical precisions of 0.1%–0.3%. Detailed studies show that the data are free of possible instrumental biases, interference effects, etc. In all cases, the secondary ions produced by sputtering are enriched in the lighter isotope, and the degree of this enrichment is a function both of the spatial location and the energy of the extracted ions relative to the sputtering site. The maximum observedL/Henrichment factors vary from 6.5%/amu for B to 0.6%/amu for Pb, and are observed to show an approximateMH/ML[rather than a (MH/ML)1/2] dependence on mass. For masses greater than 50, the mass dependence of this fractionation can be closely described by an ionization model modified after Schroeeretal. [Surf. Sci. 34, 571 (1973)]; it is improbable that the observed fractionation is related to differential sputtering effects. Use of ion microprobes for isotopic research in geochemistry/cosmochemistry will require careful control of this isotopic fractionation process if a precision of better than 1%–2% is sought.

ISSN:0021-8979    

DOI:10.1063/1.330636

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Ground‐state dissociative attachment rates in HCl and Cl2are obtained in the electron energy ranges from 0.7 to 5 eV. The results are compared with previous cross‐section data convoluted with Boltzmann‐code calculations for the electron energy distribution.

ISSN:0021-8979    

DOI:10.1063/1.330637

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A source has been constructed for the generation of metal cluster beams. The particles are detected by electronic time of flight mass spectrometry which includes pulsed electron impact ionization. Condensation occurs in a supersonic carrier gas (H2, He, or Ar) and large dimer/monomer ratios are found, although the Zn1vapor pressure before the expansion is only 10−3mbar. The highest measured value of the dimer to monomer intensity ratio was 6.

ISSN:0021-8979    

DOI:10.1063/1.330620

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Exact solutions are presented for the magnetic field of single and double current‐carrying helical windings. The latter is a configuration used widely in free electron lasers. Differences are shown between the exact field and the simple form commonly assumed in analyzing free electron laser interactions.

ISSN:0021-8979    

DOI:10.1063/1.330621

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A magnetic torque is induced by motions of a cylindrical metal shell that is being levitated around an alternating‐current filament—a suspension device analyzed previously for the motionless case. This kinetic magnetic torque is calculated for shell‐filament configurations in which the shell rotates on its own axis while revolving in circular orbits about the parallel current axis. The calculated torque is given numerically over a wide range of device parameters via a set of universal curves, with analytic formulae for limiting cases. The torque results are used to assess the dynamics of the suspension under various conditions, including external magnetic spin damping and extraneous orbital momentum generation.

ISSN:0021-8979    

DOI:10.1063/1.330622

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Models are presented which facilitate investigation of the longitudinal dynamics of non‐relativistic beams in inductive linear accelerators. In the limit that changes in the beam distribution take place during passage through many acceleration gaps, it is shown that the equations governing the response of the beam to the gap voltages are the same as those for the transverse motions of particles passing through an array of thin lenses. The analogy with lenses provides insight into macroscopic beam current profiles, longitudinal emittance growth, beam stability, and velocity bunching.

ISSN:0021-8979    

DOI:10.1063/1.330623

出版商:AIP    

年代:1982

数据来源: AIP