摘要:

A flyback system is described for use with a Mo¨ssbauer drive transducer of the coupled loudspeaker type operating at constant programmed velocity. A flyback control waveform is generated which quickly returns the transducer to its starting position and reestablishes the programmed velocity without exciting mechanical resonances. In addition, the range over which the velocity is maintained constant and counting is permitted is automatically held constant, independent of the programmed velocity, to eliminate systematic errors that would result from a correlation between average position and velocity.

ISSN:0034-6748    

DOI:10.1063/1.1683756

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The behavior of two type‐4013 Bendix Channeltrons as single particle detectors has been investigated and the efficiency of detection for protons and electrons has been measured in a vacuum of 10−6Torr. It has been established that under electron bombardment the gain decreases with time approaching an asymptotic valueG∞which depends only on the intensity of the incident flux. An empirical formula for the dependency ofG∞on the flux in the range 103to 106electrons/sec has been derived,G∞= (1.3×1010)/J, whereJis the incident flux measured in electrons per second and the high voltage applied to the Channeltron is 3 kV. When the bombarding beam is turned off the gain is always found to recover its initial value. The efficiency for electrons and protons does not show any dependency on the gain or on the particular Channeltron used.

ISSN:0034-6748    

DOI:10.1063/1.1683757

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A description of a ``linearizing circuit'' for low velocity hot‐wire anemometry is given and a detailed analysis of the transistors chain used to generate the desired function is presented. The frequency response of the complete circuit proved very satisfactory, but special consideration had to be given to compensation for the temperature sensitivity inherent to solid state devices.

ISSN:0034-6748    

DOI:10.1063/1.1683759

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Sources of errors and noise in analog differentiators are reviewed, together with techniques for minimizing signal distortion. A modified basic operational differentiator is augmented with a linear phase filter. Accurate derivatives are obtained over the range spanning dc to 1 Hz. An inexpensive instrument is presented which reduces noise to a low level while minimizing delay distortion of the signal.

ISSN:0034-6748    

DOI:10.1063/1.1683760

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A combination small and wide angle diffractometer is described. This instrument permits collection of both small angle and normal diffractometer data as a specimen is subjected to mechanical, chemical, or thermal treatment. Curved crystal focusing optics is utilized. The useful range of the apparatus is 0.023 to approximately 60° 2&thgr;. The apparatus has the following features: (1) excellent resolution over the entire usable angular range (the focused primary beam has a half‐breadth of 4×10−4rad); (2) simplicity of design; (3) monochromatization of x rays; (4) ample specimen space, enabling one to heat, deform, or otherwise perturb specimensin situ. The unit utilizes a ground and bent quartz crystal, a Picker diffractometer, and a Hilger microfocus x‐ray tube and generator. The basic unit can be assembled largely from factory‐available apparatus, the exceptions being special mounts for the x‐ray tube and the monochromator. The alignment procedure is briefly outlined and the positions of the necessary adjusting devices are described. A specimen heater, incorporated in this instrument and accurate to ±¼ C° from room temperature to about 150°C, is described. The heater utilizes the passage of hot gases to maintain the temperature. Finally, small and wide angle scattering curves are shown to illustrate the utility of the apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1683761

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A simple plasma ion source which is capable of delivering beams of 1×10−6A at 200 eV and 0.1–0.2 eV energy spread is described. Gas efficiencies of the order of percents are obtained. This source was found to be very successful in experiments using low energy beams in the electron volt region.

ISSN:0034-6748    

DOI:10.1063/1.1683697

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A magneto‐optical method has been developed to determine the spin‐lattice relaxation times of paramagnetic ions from the maximum rate at which paramagnetism can follow an ac magnetic field modulating a dc magnetic field of 0–6000 G. The spin‐lattice relaxation time &tgr; of the paramagnetic ion determines the maximum rate at which the Faraday rotation of plane polarized light traversing the material may be modulated at low temperatures. By measuring the phase angle between the light modulated by the Faraday rotation and the perturbing magnetic field for both the pure host material and the host material doped with paramagnetic ions, one is able to determine the relationship between &tgr; and the applied static magnetic field at low temperatures. The apparatus and the method employed for this measurement are described.

ISSN:0034-6748    

DOI:10.1063/1.1683698

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A low temperature thermometer based on the temperature dependence of thevF(T) of the19F NMR frequency in antiferromagnetic MnF2has been successfully operated in the 10–40 K temperature region. Novel features include the use of a MnF2crystal with a sharp19F NMR line as the temperature sensitive element in a solid state frequency‐locking autodyne circuit that operates while completely submerged in liquid H2or He. In the present design the circuit‐sample combination takes the form of a compact probe. With this device temperature readings which are reproducible to ±10−4K at 20 K have been obtained. Various applications for precision thermometry in the 10–40 K range using the device are proposed.

ISSN:0034-6748    

DOI:10.1063/1.1683700

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An electronic controller, made of integrated circuits and inexpensive silicon controlled rectifiers, has been designed as a coupler or interface between a card reader and a frequency synthesizer to permit sequential selection of one of the 5×109frequencies available from the frequency synthesizer. Because it was designed for unattended operation under clock control, a lamp display for monitoring was included and effects of impulsive interference were investigated.

ISSN:0034-6748    

DOI:10.1063/1.1683701

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An optical system is described that produces multiple images on a streak camera slit plane. The apparatus is made up of several identical optical objectives. Each objective, consisting of a pair of collimating lenses and a pair of Dove prisms, serves to form an image that can be arbitrarily positioned and oriented at the camera slit plane. The instrument was designed primarily to record the progress of a nonplanar shock wave or detonation wave along several nonparallel paths. When used with suitable short‐duration object illumination, it is also capable of recording framing pictures of a dynamic event. Two applications of the instrument are described.

ISSN:0034-6748    

DOI:10.1063/1.1683702

出版商:AIP    

年代:1969

数据来源: AIP