摘要:

A Pockels cell light modulator which operates at radio frequencies is described. It transmits more isotropic radiation than other Pockels cell or water cell modulators that operate at these frequencies. In addition, the modulated light has less phase variation between different components of the radiation than do water cell modulators.

ISSN:0034-6748    

DOI:10.1063/1.1683745

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A device has been developed that is able to fractionate a mixture of microscopic particles according to small differences in their volume. A dilute suspension of the particles passes through a sensor within which the volume of each particle is electronically measured. Subsequently the suspension emerges into the air as a liquid jet. This jet is caused to break into a large number of individual droplets, thereby isolating the suspended particles. Droplets containing particles of the desired volume ranges are electronically charged and electrostatically deflected into suitable receptacles. The apparatus is described in considerable detail with illustrative application to polystyrene spheres and to human white blood cells.

ISSN:0034-6748    

DOI:10.1063/1.1683746

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

We have measured the transmission of monochromatic slow neutrons over the wavelength range 1–5 Å for monocrystalline and polycrystalline samples of SiO2(quartz), MgO, PbF2, and Bi at 83 K and 300 K. These materials were selected as apparently suitable for use as neutron ``low‐pass'' velocity filters; SiO2and Bi have already been used in this manner at several laboratories. Single crystals of MgO cooled to 83 K are remarkably transparent to thermal neutrons; more than 70% of the incident 2 Å neutrons are transmitted by a 15 cm sample whose transmission for 1–2 MeV neutrons is about 0.01. SiO2is nearly as transparent, in agreement with several earlier measurements by other workers. A comparison of our measurements on Bi with other reported work shows that neutron transmission is low and quite variable from sample to sample for neutron wavelengths in the range 1–2 Å but fairly high for all samples at wavelengths >4 Å (∼50% for a 15 cm sample). For the latter wavelength range, we find slowly cooled Bi castings, in which large grains have developed, to be about as transparent as (nominally) monocrystalline samples. A single crystal of PbF2exhibited higher transmission in the range 1–3.5 Å than did any Bi sample. The theoretical basis for the neutron filtering action of crystalline materials is briefly discussed.

ISSN:0034-6748    

DOI:10.1063/1.1683747

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

This paper describes an accessory designed for a Philips‐Norelco x‐ray diffractometer to allow the investigation of the spatial distribution of any particular crystal plane found near the surface of cylindrical specimens. The device holds the specimen in the exact position required for measurement, and allows it to be moved through an arc of ±33°, while it is rotated about its own cylinder axis. Adjustments are provided for examining different regions of the specimen. It will accommodate specimens between 2.8 and 8.1 cm long and between 1.0 and 2.5 cm in diameter. Results obtained from the same thin foil specimen in cylindrical and planar form show reasonable agreement.

ISSN:0034-6748    

DOI:10.1063/1.1683748

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The results of an extensive experimental program on explosive‐driven magnetic flux compression devices of the ``bellows'' type are described and discussed. These generators, in which explosively propelled conducting plates compress the magnetic flux into the final load, have been tested in single and multistage systems, generating axial fields of up to 700 kOe in volumes of the order of liters with a corresponding maximum magnetic energy in the load of 2 MJ. Bellows generators are best suited to match a single‐turn solenoid as the inductive load and it is shown that in particular cases a combination of these generators with the recently described helical ones is of great interest. Particular attention is paid to a switching system (including a closing and opening switch) with which it is possible to transfer the magnetic energy accumulated in the generators into an appropriate inductive load within 10 &mgr;sec and less. A simple analysis and the experimental results show that this is feasible, although magnetic flux and energy losses are inevitable, particularly if high switch performances are required (e.g., opening time <5 &mgr;sec, initial current rise >1 MA/&mgr;sec).

ISSN:0034-6748    

DOI:10.1063/1.1683749

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A differentially pumped, atomic scattering chamber capable of detecting both ions following a large angle collision is described. This chamber is designed for use with incident ions having energies from 0.5 to 10 MeV. A construction technique is used which eliminates bellows and allows detection of atoms and ions over an angular range of 185°.

ISSN:0034-6748    

DOI:10.1063/1.1683750

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

In many experimental situations involving an exponentially decaying process, the time constant of the decay is of fundamental interest. The information is usually contained in an electrical signal, or can be converted to an electrical signal by means of an appropriate transducer. We offer a new method by which the time constant of such a signal can be rapidly and accurately measured. The method was devised in connection with the measurement of resistivities by the eddy current decay technique, but its usefulness in a more general context is also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1683752

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Errors encountered in time differentiating a voltage signal with a simple high gain operational amplifier differentiator are studied. Numerical and electronic means of correcting these generally small errors are suggested. The circuit, including a linear sweep voltage source, used for photoemission studies in this laboratory is presented. The coefficient of the error terms for this particular circuit are calculated numerically. Presently achieved sensitivity and resolution are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1683753

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A logarithmic amplifier is described which converts exponential signals to linear signals. The slope of the latter is inversely proportional to the decay constant or lifetime. This instrument facilitates the measurement of such phenomena as luminescence lifetimes and improves the accuracy of such measurements.

ISSN:0034-6748    

DOI:10.1063/1.1683754

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The study of lattice defects quenched into small diameter wires requires the precise control of the specimen at elevated temperatures. The circuit described has heated 0.127 mm diam wires to 350°C from 0°C in 2 msec and held the temperature constant to ±5C° in such media as air, mineral oil, and argon at 6 kilobars pressure. Maximum temperature is limited only by specimen design and environment. With an appropriate analog voltage input, the specimen temperature can be varied in any manner within the limits of maximum heating and cooling rates. Of particular interest is the ability of the circuit to provide a linear quench with time constant as long as desired.

ISSN:0034-6748    

DOI:10.1063/1.1683755

出版商:AIP    

年代:1969

数据来源: AIP