摘要:

The present status of a program directed toward the improvement of ion sources and the technology of intense dc ion beams is described. The work is in the energy range of from 20–600 keV at currents of up to 1 A. Several factors have differentiated the approach from that existing in some other areas of ion beam research. There are severe cooling problems in the ion source and in beam targets. Grids cannot be used in the electrode system, and many of the techniques which have been used to study detailed emittance shapes are very difficult to utilize because of these thermal problems. On the other hand, it is possible to accumulate electrons in these dc beams to eliminate the dispersive effect of space charge. Pulsed beams with on‐times of less than a few hundred microseconds ordinarily are completely unneutralized. Ion sources are described which are especially suited to proton production and to molecular ion production at source arc currents of up to 50 A. Single gap accelerating and focusing arrangements are described. A special configuration prevents electron trapping and subsequent break‐down in the combined electric and magnetic fields.

ISSN:0034-6748    

DOI:10.1063/1.1720740

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Identical particle extraction, a new method for the microanalysis of contamination particles on surfaces or the identification of precipitates or particles in various matrixes, utilizes the extraction replica method and the identical area method. The principal advantage of this method is that the electron microprobe is used to obtain an elemental analysis of the identical particles from which electron diffraction patterns are obtained.

ISSN:0034-6748    

DOI:10.1063/1.1720741

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An apparatus for the differential thermal analysis of small (1.7 ml) samples of solutions is described. A heat effect amounting to 50 cal per liter of solution taking place over a 30° temperature interval can be measured with a precision of 5%, and a change in heat capacity of the solution amounting to 2 cal deg−1per liter of solution can be measured with a precision of 15%.

ISSN:0034-6748    

DOI:10.1063/1.1720742

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A nanosecond fluorimeter suitable for measuring the emission kinetics of chromophores which have excited state lifetimes longer than 1 nsec is described in this paper. The acquisition and processing of the nanosecond data were accomplished in entirety by computers. The pulsed light source, an oxygen spark‐gap lamp operated in a relaxation mode, is simple to construct and use. The lamp exhibits high intensity over a broad spectral range, as well as a short pulse duration. In the wavelength interval from 230 to about 470 m&mgr;, there were 6×1011photons per pulse at a repetition rate of 2.1 kHz. The spectrum of the lamp was approximately flat between 200 and 600 m&mgr;. The rise and fall times of the light pulse, as measured with a planar photodiode, were 0.7 and 1.1 nsec. The accompanying current pulse had rise and fall times shorter than 0.43 nsec. A 1P21 photomultiplier tube was used as the detector in the fluorimeter. The output of the 1P21 was connected to a sampling oscilloscope that was triggered by a synchronous current pulse from the light source. The analog output of the sampling oscilloscope was digitized, stored, and averaged on a LINC computer, and then transferred to magnetic tape for processing on an IBM 7090. The nanosecond data were analyzed in terms of a convolution integral which took into account the shape of the exciting light pulse as seen by the detection system. The use of the apparatus is illustrated by two examples: 1, 4‐bis‐2‐ (4‐methyl‐5‐phenyloxazolyl) benzene, which has a lifetime of 1.5 nsec; and 1‐anilino‐8‐naphthalene sulfonate bound to serum albumin, which has a lifetime of 17.1 nsec.

ISSN:0034-6748    

DOI:10.1063/1.1720743

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An instrument for measuring electrolyte conductance or resistance is described. This instrument is unique in that it has the following combination of features: (1) resistance values in the range 1×10−1to 2×105&OHgr; can be measured with an accuracy of better than 5%; (2) resistance can be continuously recorded as a function of time; (3) the internal resistance of voltaic cells can be measured during cell discharge; and (4) no special conductivity cells are required. The present instrument is a modified ac Wheatstone bridge. The value of the unbalance signal is monitored and mathematically converted to resistance. Uses for the instrument are discussed and typical results are given.

ISSN:0034-6748    

DOI:10.1063/1.1720744

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simple method has been developed for displaying and measuring the important features of re‐entrant hysteresis loops of ferromagnetic wires. A conventional ac loop tracer is modified by the addition of a pulse generator and an extra coil coaxial with the specimen. A current pulse in this coil is used to nucleate a reverse domain in the wire at the appropriate time so that domain walls are available to be moved by the field coil. The loop traced on the oscilloscope then shows the wall motion coercivity. When no current pulse is used, the conventional rectangular loop which shows the nucleation field is displayed. If the pulses are generated at half the applied field frequency, the inner and outer loops are displayed alternately and appear to be superimposed. This loop tracer has been used to measure the normal re‐entrancy of permalloy wires, the stress‐induced re‐entrancy of ribbons with positive magnetostriction constants, and an unusual type of re‐entrancy in nickel wires. With appropriate modifications this technique can be applied to other specimen configurations and loop tracers.

ISSN:0034-6748    

DOI:10.1063/1.1720745

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An experimental apparatus to allow generation, control, and sampling of particulate smokes has been combined with an angular scanning spectropolarimeter to allow study of the optical character of polydisperse and irregularly shaped particles. The experimental apparatus and its operation are described.

ISSN:0034-6748    

DOI:10.1063/1.1720746

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A technique for producing monodisperse sprays is described. The technique makes use of Rayleigh's criterion for the breakup of capillary jets by mechanically vibrating a number of uniform size capillary needles arranged in parallel. It was used to produce sprays in the size range of 290–950 &mgr;, but in principle there is no reason why this range cannot be extended. The regime of spray sizes where drop coalescence is likely to take place is delineated, and methods of minimizing coalescence are described.

ISSN:0034-6748    

DOI:10.1063/1.1720747

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A description is given of the techniques and apparatus employed to generate a high density keV plasma capable of serving as an intense source of soft x rays. The spectral distributions of the emission spectra have been analyzed and details of the analysis are presented. The distributions are characteristic of 5–10 keV optically thin plasma continua with line radiation superimposed. Source intensities of from 0.1 to 5 MW are readily produced, lasting for a few tenths &mgr;sec; these intensities are a strong function of the material used for discharge tube electrodes, varying asZ4forZ≤30. Finally, cursory experiments were conducted to examine the feasibility of filtering these spectra to obtain a monochromatic radiation source.

ISSN:0034-6748    

DOI:10.1063/1.1720748

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A calorimetric system for dosimetry on a beam of charged particles is described. The calorimeter works at liquid helium temperature. The total dose may be measured with an accuracy of 0.3%, and the dose per area with 0.4%. No theoretical corrections are needed.

ISSN:0034-6748    

DOI:10.1063/1.1720749

出版商:AIP    

年代:1967

数据来源: AIP