摘要:

The construction of a mechanical neutron monochromator for the cold neutron region with 80% transmission is described. The apparatus is specially designed to be used in connection with a neutron crystal spectrometer for filtering out higher order reflections by placing it between the crystal and the counter. An experimental test of the machine has been performed by measuring the gold cross section and the neutron intensity as a function of the angular velocity of the rotor for a certain wavelength. The result shows that no higher order neutrons are transmitted.

ISSN:0034-6748    

DOI:10.1063/1.1715699

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A flat coil is suspended in a magnetic field so that in equilibrium it is coplanar with the field and can oscillate about an axis in the plane of the coil perpendicular to the field. When an alternating current is passed through the coil the system behaves as an inductance in series with a condenser of capacity inversely proportional to the square of the magnetic field. The principle has been applied to the measurement of magnetic field. The instrument is capable of a precision of one part in 102with simple auxiliary apparatus.The application to a particle analyzing magnet is described. With some elaboration the magnetic field can be measured and stabilized to one part in 104in the range 1–12 kilogauss.

ISSN:0034-6748    

DOI:10.1063/1.1715705

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A possible electrostatic lens consists of a cylindrical surface along which the potential varies as the square of the distance from some original plane. If the cylinder is very long or is terminated without distorting the field within, the trajectories of charged particles inside it can be calculated analytically. These calculations show that a small diameter source of electrons inside the cylinder can be imaged, with magnification unity and slight aberration, at another point in the cylinder. A short section of the cylinder with open ends serves as a thick lens for focusing a beam of particles, the focusing effect being due to the main field inside the cylinder plus end effects. Such a lens was constructed, the boundary condition being realized by a succession of closely spaced rings maintained at the proper potentials. This lens was more efficient in focusing a highly divergent beam of ions than were several combinations of conventional lenses which were also tried.

ISSN:0034-6748    

DOI:10.1063/1.1715716

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A new type of scanning electrometer is described which is capable of measuring the charge on areas as small as 0.3 cm2at a rate fast enough to show changes in charge distribution on a dielectric surface within intervals of the order of 30 msec. The minimum charge density which can be measured is about 0.6×10−9coulomb cm−2. Resolution of charged areas of the order of one millimeter apart is possible. This provides a new tool for studying the distribution of surface charges in detail.

ISSN:0034-6748    

DOI:10.1063/1.1715696

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A simple electro‐optical aspect system for use in upper air research rockets is described. Observations of the earth's albedo or night air glow along with observations of celestial bodies provide data from which the rocket's aspect is determined. A mechanical computer is described which greatly simplified aspect data reduction.

ISSN:0034-6748    

DOI:10.1063/1.1715697

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

This paper is primarily concerned with the effect on the line profile shape and intensity of the angle &phgr;, the angle made by the projection of the electron velocity vector on a plane perpendicular to the instrument axis at the source with the radius of the source point. Quantitative results are quoted for several geometries. The line profile, expected intensity, and optimum source size for a commonly used slit geometry utilizing an entrance slit for take‐off angle selection is found to differ significantly from previously quoted results, the intensity for the same half‐width for optimum source size being 46% of the earlier work. A new slit geometry consisting of an additional baffle near the source which restricts &phgr; is discussed and is found to improve the expected intensity for the same line half‐width by 24% for an optimized Hubert slit system which is already found in this paper to be 28% better than the best of previous slit geometries. Finally, a geometry which selects &phgr; properly is shown to remove all dependence on source size from the resolution.

ISSN:0034-6748    

DOI:10.1063/1.1715698

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

This paper discusses the principle and gives some formulas that can be used for computing from schlieren effects the refractive index, the mass concentration, and the anhydrous mass of microscopic particles like cells or cell constituents.

ISSN:0034-6748    

DOI:10.1063/1.1715700

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A new instrument has been designed for the undistorted display of ferroelectric hysteresis loops even in the presence of relatively high conductivity. The electrical characteristics of a sample are determined directly from dial settings and meter readings. The basic circuit of the bridge may be described as two parallel Sawyer and Tower circuits, one containing the sample and the other containing resistors and capacitors for the compensation of conductivity and dielectric constant at saturation. The compensated hysteresis loop is displayed on an oscilloscope with the aid of a calibrated differential amplifier. The spontaneous polarization and the applied voltage, as well as the coercive field, are read on an electronic peak voltmeter. An important feature of the bridge is that measurements are independent of the frequency and wave form of the applied voltage.

ISSN:0034-6748    

DOI:10.1063/1.1715701

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A blood pressure regulator for use in cases of shock, hypotensive anesthesia, and in medical research is described. The difference between measured and reference values of blood pressure is used to control the infusion rate of drugs acting on the cardiovascular system. Although the system is inherently nonlinear, it is stable when operated with restricted gain.

ISSN:0034-6748    

DOI:10.1063/1.1715702

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The logarithmic response of the amplifier described in this paper is derived by extracting an output proportional to the time required for the voltage across a parallel resistance condenser combination to decay to a small fixed value. The input voltage is sampled with a 400‐cy converter. Accordingly, the amplifier is restricted to a resolving time of 1/400th of a second. A logarithmic response over four decades with a deviation of less than 1% of the maximum output is secured. The immediate purpose of the amplifier is to aid in the study of the transients associated with photocells.

ISSN:0034-6748    

DOI:10.1063/1.1715703

出版商:AIP    

年代:1957

数据来源: AIP