摘要:

A simple tunnel diode circuit capable of accurately timing the zero crossing point of bipolar pulses is described. The combination of a fast tunnel diode and a nonlinear load line results in a circuit that can detect the zero crossing of a wide range of input waveshapes. This technique has been utilized in the design of a versatile, fast zero crossing discriminator. This instrument, which is compatible with existing logic systems, exhibits time slewing of less than 200 psec for an input amplitude range of at least 1 to 70 times threshold. Direct coupling and extremely short recovery time enable the instrument to function well at rates as high as 50 MHz.

ISSN:0034-6748    

DOI:10.1063/1.1720559

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simplified bridge system for measurement of internal friction and fractional variations of Young's modulus at kilohertz frequencies is described. The system, composed of commercially available components, is used with a two‐part composite oscillator and is capable of measuring (logarithmic) decrements ranging from 10−7to 10−2. Fractional variations of decrement and Young's modulus can be detected to within 0.5% and 0.1 parts per million, respectively.

ISSN:0034-6748    

DOI:10.1063/1.1720560

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A pulse calorimeter for measuring the specific heat of electrical conductors from 25 to 900°C is described. The technique employed was unique in that a digital voltmeter, which was capable of recording 400 readings per second to a readability of 0.1% of full scale, was utilized to measure the transient temperature and power signals requisite to the method. Using this technique, a calculated determinate accuracy of 99% was achieved. Measurements of the specific heat of high‐purity iron from 25 to 900°C confirmed this calculated accuracy and were repeatable to within ±0.5%. The calorimeter was capable of measuring the specific heat rapidly at temperature intervals as small as 0.1 C°. Modifications are suggested to decrease the measurement errors to 0.5% and to increase the temperature range from −190 to 1400°C.

ISSN:0034-6748    

DOI:10.1063/1.1720561

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The described automatic sequence and photo control system for photographically monitoring simultaneous ultracentrifugation of four different samples is compatible with existing equipment. The system is inexpensive to install and provides complete flexibility in time intervals and sequences over wide ranges. In conjunction with a motion picture camera installation, high capacity is obtained without film handling and at enormous reduction in cost per photograph.

ISSN:0034-6748    

DOI:10.1063/1.1720562

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A technique for locking the output phase of a frequency multiplier to its input is described. A sampling system is utilized in which a narrow phase‐stable pulse, generated at a zero crossing of the input signal, is used to sample the frequency multiplier output. By means of a feedback loop the phase angle of the input to the controlled frequency multiplier is adjusted to minimize multiplier output phase variations with respect to the sampling pulse.

ISSN:0034-6748    

DOI:10.1063/1.1720563

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A hot cathode ion source has been developed to produce pulsed ion beams. The source has a canal electrode whose characteristics resemble those of the grid of a vacuum triode. The characteristics are attributed to sheath formation in the canal. The ratio of the maximum current to the minimum is about 103. A pulsed ion beam of a milliampere of submicrosecond duration has been easily obtained with a low power pulser. The rise time of the pulsed current is 0.1 &mgr;sec.

ISSN:0034-6748    

DOI:10.1063/1.1720564

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The relative detection efficiency of a curved continuous channel electron multiplier has been measured for H+, H2+,3He+,3He++, He+, Ne+, and A+ions over a 500‐eV energy range. The detector's efficiency is presented as a function of the incoming ion's energy, velocity, and degree of ionization. Preacceleration was employed to reduce the falloff in efficiency for energies below 3 keV.

ISSN:0034-6748    

DOI:10.1063/1.1720565

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A method of compensation for the effects of a longitudinal slot in a rectangular waveguide section used in a standing‐wave meter has been devised and investigated. The slot causes changes of the propagation constant and characteristic impedance of the guide. Compensation of these effects is necessary in the millimeter‐wave region where they become excessive, since the width of the guide is small so that the width of the slot represents an appreciable fraction of the former. The compensation, which is practically frequency independent, is carried out by an extension of the side walls of the slot into the interior of the waveguide forming two internal ridges on both sides of the slot. The field distribution inside the compensated waveguide is computed by conformal mapping and the height of the compensating ridges determined from waveguide and slot dimensions. Numerical results are presented for an example.

ISSN:0034-6748    

DOI:10.1063/1.1720566

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simple feedback system has been developed for application to either a field‐interrupting electrostatic modulator or to a vibrating electrode modulator; this system substantially increases the stability, sensitivity, and accuracy of the electrostatic voltmeter in which it is employed. An accuracy of 0.2% and a response rate of 2000 V/sec have been achieved in this instrument, which incorporates a transparent, vibrating NESA glass electrode to facilitate sample illumination.

ISSN:0034-6748    

DOI:10.1063/1.1720567

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An improved disk electropolishing technique, developed for the preparation of thin foil electron microscope specimens, eliminates the problem of premature perforation of specimens. Its rotating holder design prevents gas bubble adherence while maintaining low‐voltage, low‐temperature operation.

ISSN:0034-6748    

DOI:10.1063/1.1720568

出版商:AIP    

年代:1967

数据来源: AIP