摘要:

Some of the important considerations in the design of a retarding field analyzer suitable for Auger electron spectroscopy based on display LEED optics are described. From such considerations an instrument has been built with an instrumental linewidth of less than 0.3% (resolution greater than 360). Analysis is made of the limitations insensitivity of the device due to shot noise, and on this basis a comparison is made with a 127° cylindrical electrostatic analyzer. The analysis can be readily extended to other forms of retarding field and deflection analyzers.

ISSN:0034-6748    

DOI:10.1063/1.1684071

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A source of pure beams of thermal alkyl radicals for molecular beam scattering experiments is described. A parent compound, (CH3)2Hg, (CH3)3Bi, CH3I, or (C2H5)2Hg, was pyrolyzed in an array of small Ta tubes, and a beam of the products entered a slotted disk type velocity selector. Selection at 1500 m/sec chemically purified the radical beam by removing parent molecules and high mass decomposition products. The best purities, found by modulated beam mass spectrometry, average to 94±8 mole% CH3, and in these runs the estimated intensities were 2−7×1015radicals/sr·sec, or 3−10×1013radicals/cm2·sec at the detector. Light hydrocarbons (C1,C2) were the major impurities, their concentration increasing with methyl flux.

ISSN:0034-6748    

DOI:10.1063/1.1684072

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An inexpensive 120 Gc detector, using a commercially available semiconductor wafer and whisker, is described. The construction of a simple p‐i‐n reflection modulator is discussed in detail. Characteristics for both devices are given.

ISSN:0034-6748    

DOI:10.1063/1.1684073

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A stroboscopically illuminated turntable is described; accurate and easily manipulated variation of the flashing frequency relative to the turntable frequency is achieved by photoelectric triggering of the lamp. The device is suitable for both visual and photographic evaluation of objects that may possess ``hidden'' degrees of radial (rotational) symmetry.

ISSN:0034-6748    

DOI:10.1063/1.1684074

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The null method described permits either guarded three‐terminal or four‐terminal potential probe measurements of conductance from 1 kHz to dc and of capacitance to frequencies as low as 0.01 Hz. Sample currents to a null detector are balanced by adjustable currents derived from dc voltage inverter and follower circuits which drive fixed standards of conductance and capacitance. Procedures for minimizing errors from circuit residuals and results of representative measurements are described.

ISSN:0034-6748    

DOI:10.1063/1.1684075

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An apparatus for the measurement of internal friction in the kilohertz frequency range is described. The Marx three component piezoelectric technique is used and the apparatus is designed for measurements at low and high temperatures in high vacuum. A graphical technique for calculating the damping from the measured voltages is presented and is used in a manner that improves the accuracy with which amplitude independent and amplitude dependent damping can be separated.

ISSN:0034-6748    

DOI:10.1063/1.1684076

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A low frequency torsion pendulum, employing Joule heating of metal wire specimens, is described. End losses are compensated by a strip heater attached to the fixed grip and by an induction heating coil surrounding the oscillating grip. Regulation of the three heat inputs by precision current adjusting type temperature controllers provides exceptional temperature uniformity and long term stability. Rapid response to changes in temperature set‐point results from the low thermal inertia of the system. Examples of experiments utilizing these features are given.

ISSN:0034-6748    

DOI:10.1063/1.1684077

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

In order to minimize the transient effect associated with switching a constant current power supply to different loads, a break‐before‐make type of switch contact arrangement is shown to be preferable to a make‐before‐break type of arrangement. Series resistance in the load circuit may be required for low current applications. With a constant heater current, the average heater power for the entire heating period can be precisely determined as the product of the current and the mean value of two particular potential readings. These two readings, symmetrical about the midpoint of the heating period, should be taken at specified intervals as determined by the exponential heat conduction characteristics of the calorimeter assembly.

ISSN:0034-6748    

DOI:10.1063/1.1684078

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A transformer ratio bridge is usually capable of measuring the capacitance of specimens with a maximum dissipation factor of about 101. The technique described herein allows this type of bridge to measure the capacitance, with a reasonable degree of accuracy, of specimens with a dissipation factor as high as 104. This is accomplished by correcting for and minimizing effects due to stray inductance and capacitance in the measurement system. The technique uses standard laboratory instrumentation, is simple in nature, and provides for the determination of dielectric behavior over a wide range of electrical conductivity.

ISSN:0034-6748    

DOI:10.1063/1.1684079

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A Kerr magneto‐optic camera has been constructed which takes 10 nsec exposures of the dynamic magnetization configuration in a magnetic thin film during high speed flux reversal. The photographs obtained have 10 &mgr; resolution and sufficient contrast and brightness to record, in a single exposure, the dynamic state during a 50 nsec or longer flux reversal. The time at which the photograph is taken relative to the application of the switching field is variable from ‐100 nsec to +10 &mgr;sec with a relative time stability at any setting of ±3 nsec. A Q‐switched ruby laser is used as a light source. The 10 nsec exposure time is obtained with a Kerr electro‐optic shutter. The reversing field has a risetime of 10 nsec, decay time of 20 nsec, variable amplitude (<30 Oe), duration (<10 &mgr;sec), and is applied with a stripline. Included in the description of the system are discussions of a blocking oscillator circuit used to drive KU‐27 thyratrons with a jitter of less than 1 nsec, an electron multiplier pulse amplifier with a 6 nsec risetime and a 0 to 1.5 kV output into 50 &OHgr;, and a thyratron pulse amplifier with a 10 nsec risetime and a 1.0 to 10 kV output into 50 &OHgr;. The apparatus is particularly suitable for studying high speed flux reversal in that it gives a visual picture of the dynamic state of the magnetization. Examples of sequences of photographs depicting dynamic flux reversal are also included.

ISSN:0034-6748    

DOI:10.1063/1.1684080

出版商:AIP    

年代:1969

数据来源: AIP