摘要:

Quadrature detection modifications and a microcell arrangement are described for the Varian XL‐100 NMR spectrometer which routinely improve sensitivity in13C Fourier transform sample‐limited studies by a factor of 4–5. The power requirement of the rf pulse amplifier is relaxed by a factor of 4. Previously attainable resolution is not affected.

ISSN:0034-6748    

DOI:10.1063/1.1686817

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A versatile photon and charged particle imaging system is described. The Ranicon employs a microchannel electron multiplier plate to convert each detected event into a charge signal. This charge pulse is proximity focused onto a large area resistive anode plate equipped with pickup electrodes on its edges. Each event is located electronically by the ratios of the charges collected at the edges or by the differences of the signals' rise times. One or two dimensional pictures are built up by storing events digitally (e.g., a core memory) or in analog form (e.g., a storage oscilloscope). Compact laboratory models have been constructed and tested. Operating characteristics, applications, limitations, and advantages of the Ranicon are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1686818

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A device has been developed which uses a Q‐switched laser pulse to produce a plane compressive stress pulse or a slowly decaying sinusoidal stress wave train in any solid or liquid material. The device utilizes a thin liquid layer to totally absorb the laser pulse and generate a stress pulse by rapid thermal expansion. Compressive stress pulses of 200 nsec duration and up to 5 kilobar amplitude have been obtained. Wave trains of about 30 cycles duration and 1/4 kilobar amplitude (peak‐to‐peak in typical solids) have been obtained at frequencies between 1–25 MHz. Stress amplitudes may be varied by filtering the incident laser radiation. The laser radiation does not damage this transducer, so it may be used indefinitely.

ISSN:0034-6748    

DOI:10.1063/1.1686819

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A simple method for measuring interface state density distribution of an MIS capacitor is proposed. The method is the expanded one which is based on comparing a measured quasistaticC‐Vcurve to ideal characteristics. The measurement can be achieved semiautomatically and simultaneously with the quasistatic capacitance measurement by using analog systems. And rather time‐consuming computer calculation is not necessary. The completed apparatus can measure the interface state density in the range of 1010−3×1012/cm2· eV for standard Al&sngbnd;SiO2&sngbnd;Si capacitors. It is necessary for precise measurement to determine accurately the doping density of substrate and insulator capacitance.

ISSN:0034-6748    

DOI:10.1063/1.1686820

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A problem with depth profiling in Auger electron spectroscopy is the alignment of the electron and sputter ion beams so that they are coincident on the specimen at the focal point of the analyzer. Most procedures used to date are tedious and require the use of a Faraday cup. The technique reported here allows the direct, precise, and quick alignment of the ion bombardment beam utilizing the optics of the electron spectrometer used for Auger analysis. A typical 2 kV focused ion beam can be aligned within a few minutes using the phenomenon of low energy ion excited Auger electron analysis.

ISSN:0034-6748    

DOI:10.1063/1.1686821

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Samples held at pressures up to 260 kilobar in a diamond anvil pressure cell have been heated to very high temperatures by means of a laser beam introduced through one of the transparent diamond anvils. A 7 J pulsed ruby laser is able to produce temperatures as high as 3000°C in a high pressure sample. A 60 W cw YAG laser is able to produce sustained temperatures up to 2000°C. An optical pyrometer has been used in the latter case to measure the brightness temperature with an accuracy of ±50°C. The ruby laser has been successful in directly converting graphite to diamond; the YAG laser has made it possible to show that (Fe,Mg)2SiO4disproportionates to (Fe,Mg)O plus SiO2(stishovite) at pressures in excess of 200 kilobars and temperatures above 1000°C.

ISSN:0034-6748    

DOI:10.1063/1.1686822

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The design and operation of a unique apparatus for plasma anodization of bulk and vapor deposited metals is described. This apparatus made possible in one chamber vapor deposition of high purity metals on polished substrates, establishment of controlled glow discharges with various inert and reactive gases, and simultaneous ellipsometric and electrical measurements of the oxide films as they were being formed. The apparatus was also used for optical constant determinations at pressure of less than 1×10−10Torr after evaporation of high purity metals.

ISSN:0034-6748    

DOI:10.1063/1.1686823

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A digitally programmable microwave source, assembled from various commercially available components and covering the range 8.0–40.0 GHz in four bands, has been interfaced to a small computer, and software has been developed for the acquisition, storage, retrieval, and statistical analysis of data. This system has been used in conjunction with Stark and Zeeman modulated microwave spectrometers, yielding high resolution, high sensitivity, high accuracy, and operation with a considerable degree of automation and flexibility. The programming time is typically 5–15 msec, and the frequency may be set in increments of 100 Hz or less. The long term frequency stability and accuracy is 2×10−9/month, and the short term stability or spectral purity appears to be excellent, in agreement with theoretical expectations. The software provides for signal averaging, baseline subtraction, convenient display and frequency measurement, and for transfer of data, via magnetic tape, to a large scale computer, where it can be analyzed by a nonlinear least squares procedure.

ISSN:0034-6748    

DOI:10.1063/1.1686824

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The technique of derivative thermal analysis, dTA, which plots sample temperature vs rate of change of sample temperature, has been refined in this apparatus to produce calibrated derivative thermal analysis curves in units of degrees and degrees/second. The scaling factors of 1 K=2 mV and 1 K/sec = −100 mV permit calibration to 5273 K, materials permitting, with digital temperature readout. The derivative function provides high sensitivity for detecting very weak fast phase transitions by observing thermal arrests in linear heating and cooling curves. A companion automatic temperature controller holds the furnace temperature constant, or programs it up or down at a linear rate of 0.1 K/sec to 10 K/sec. Light from the incandescent sample and surrounding furnace is divided into two paths by a beam splitter. One path to an optical pyrometer provides temperature calibration. Light in the second path is sensed by photo transistors that measure the sample and furnace temperatures. The temperature signal is linearized by taking the logarithm of the photo transistor current. Operational amplifier circuits establish the desired proportionality to temperature. The sample and furnace temperature signals are differentiated to produce rate signals for dTA display and temperature control. Illustrative dTA curves of the U&sngbnd;C, Nb&sngbnd;C, and Nb&sngbnd;Al systems are included.

ISSN:0034-6748    

DOI:10.1063/1.1686825

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

It is demonstrated that the absolute transmission of a quadrupole mass filter is improved when the ions are bunched and injected at the proper phase into the instrument. Experiment shows that a rough approximation to the theoretical solution is sufficient to increase the transmission by 125% at high resolution where it is most needed.

ISSN:0034-6748    

DOI:10.1063/1.1686826

出版商:AIP    

年代:1974

数据来源: AIP