摘要:

A simple, versatile pulse sequence generator for use with the McSkimin pulse‐superposition technique of measuring ultrasonic velocities is described. Standard TTL integrated circuits are used in construction of the unit. The generator produces a sequence either of two pulses followed by 2, 6, 14, or 30 spaces, or of four pulses followed by 4, 12, 28, or 60 spaces. The pulse repetition frequency is determined by an external oscillator operating at a multiple (one, two, five, or ten) of this frequency. Testing and operation of the unit is described.

ISSN:0034-6748    

DOI:10.1063/1.1134092

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Radar specialists know that during the reflection of waves the phenomenon of depolarization appears in a more or less intense manner depending upon atmospheric conditions. The measurement of depolarization in a laboratory setting is difficult because the problem involves measuring a weak, incoherent energy superimposed upon a strong, coherent energy, and standard instruments have not been conceived to effect such a measurement. The author first studies the influence of wave depolarizations upon reflectometric measurements made at normal incidence in standard rectangular guides, then he indicates how, by using an interferometer, one can perform the measurement of the coherent and incoherent energy. In the second part of his report, he studies the influence of wave depolarizations made during reflection at an oblique angle (for example, the measurement of the Brewster angle). He then indicates a type of interferential analyzer (a two‐ or a three‐wave) employed with a polarization duplexer which enables one to measure, or to record (with a three‐wave interferometer), depolarization as well as the rotation and ellipticity of the reflected coherent energy. Finally, in the third part, the author considers the case of reflection made at normal incidence in circular waveguides (mode TE11). He is led to propose an interferential reflecto‐polarimeter–ellipsometer having as its principal element a ’’lossy’’ turnstile junction, the properties of which he outlines briefly. He shows that this instrument will enable one to achieve the measurement and recording (when associated with a three‐wave interferometer) of depolarization as well as of the rotation and ellipticity of the coherent part of the reflected wave.

ISSN:0034-6748    

DOI:10.1063/1.1134093

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An electromechanical apparatus is described that was designed to determine the twist in textile yarns by measuring the number of turns a yarn untwists due to the torque created by a freely rotating axial load. The apparatus utilizes an optoelectronic system to count the number of turns in each direction so that the net number of turns needed to reach the equilibrium state is measured. The damping of the rotating unit was found to be noncritical. A mechanical support system has been designed which facilitates testing and improves reproducibility of results. The system can be used for staple and continuous filament yarns but the sample length for staple yarns must be shorter than the fiber length.

ISSN:0034-6748    

DOI:10.1063/1.1134094

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An apparatus to measure inelastic low‐energy electron diffraction (ILEED) and energy‐ and angular‐dependent secondary electron emission, (EADSEE), is described. The apparatus can measure EADSEE for incident beam energies of up to 200 eV and ILEED for beam energies up to 50 eV, with energy and angular resolutions of about 0.15 eV and 1.5°, respectively. General design criteria are discussed, and detail is provided where a little‐known technique has been employed.

ISSN:0034-6748    

DOI:10.1063/1.1134095

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Further improvements to the pulsed EPR spectrometer of Huisjen and Hyde [Rev. Sci. Instrum. 45, 669 (1974)] are described. Special attention is given to techniques for separation of free‐induction‐decay and saturation‐recovery signals. The instrument is suitable for determination of spin‐lattice relaxation times as short as 10−7sec, and is designed particularly for measurements on dilute solutions of free radicals and of spin‐labeled biomolecules. Analytical solutions of the Bloch equations are obtained that are appropriate for this instrument. The predictions of the equations have been verified by comparison with experiments on the tetracyanoethylene (TCNE) radical anion.

ISSN:0034-6748    

DOI:10.1063/1.1134096

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Iron microparticles were fired onto a capacitor‐type microparticle detector which responded to an impact with a spark discharge. Ion currents were extracted from the spark and analyzed in a time‐of‐flight mass spectrometer. The mass spectra showed the elements of both detector and particle materials. The total extracted ion current was typically 10 A within a period of 100 nsec, indicating very efficient vaporization of the particle and ionization of the vapor. Potential applications include research on cosmic dust, atmospheric aerosols and cloud droplets, particles ejected by rocket or jet engines, by machining processes, or by nuclear bomb explosions.

ISSN:0034-6748    

DOI:10.1063/1.1134097

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A resonant transformer high‐voltage (HV) generator is described that delivers a 1.1‐MV peak on the HV head of the secondary circuit. The HV head feeds a field emission diode that gives out a 6‐kA/20‐nsec electron beam. High repetition rates, up to 3 pulses/sec (power supply limited), have been attained with foilless diodes. Design details and electron beam characteristics are given and discussed.

ISSN:0034-6748    

DOI:10.1063/1.1134098

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A method is described for measuring the thickness of a flowing liquid film by the use of laser scattering from suspended latex particles. The apparatus described has a linear voltage to film thickness relationship, unlike capacitance and resistance methods.

ISSN:0034-6748    

DOI:10.1063/1.1134099

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A circuit breaker capable of transferring a current of 200 kA to a fuse placed in parallel in 10 &mgr;sec is described. The conducting element is a bar with a cross section in the shape of a T which is burst open at the joint of the arms and leg by pressurized insulating oil. The command, which uses magnetic pressure, is very efficient. The circuit breaker–fuse combination can be used to transfer energy stored in a coil driven by a homopolar generator rapidly to a load.

ISSN:0034-6748    

DOI:10.1063/1.1134100

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The design and construction of an inelastic electron scattering spectrometer for the study of electronic excitations of solids is described. The spectrometer features high beam energy (300 keV) and fine energy loss resolution (<0.1 eV). Energy loss spectra in the range 0–1000 eV may be measured with momentum transfer from 0 to 2 A˚−1.

ISSN:0034-6748    

DOI:10.1063/1.1134101

出版商:AIP    

年代:1975

数据来源: AIP