摘要:

Secondary electron energy distributions from most materials contain a great deal of fine structure, including Auger transitions, in the range 0–200 eV. Especially in the case of retarding field energy analyzers, these relatively small peaks are superimposed on a large smoothly varying background signal with the result that quantitative measurement of peak heights is especially difficult. A method for minimizing the undesirable background signal is described; it utilizes appropriate programing of the ac modulation of the retarding potential,Vac&agr;Emsin&ohgr;t. This technique results in improved energy resolution of retarding field analyzers at low electron energies where, in general, resolution is more critical than sensitivity. The detection of fine structure which would normally be lost if a constant modulation signal were employed as in the conventional procedure is demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1686010

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The electron emission capability of recently developed thermal electron emitters which can be delineated into small areas of almost any desirable shape by standard photolithographic processes has been studied. The emission performance is found to be comparable to standard sprayed oxide coated cathodes, i.e., the effective work function &phgr;E(1000 K) ≃ 1.66 ± 0.50 eV and &Dgr;&phgr;E/&Dgr;T≃ 6.3 × 10−4eV/K.

ISSN:0034-6748    

DOI:10.1063/1.1686011

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Noise pollution level is an index of the annoyance and objectionability of noise which has recently been drawing increasing interest. It is based on two quantities, one relating to the equivalent continuous energy level and the other relating to the variations in level. This paper describes an instrument which has been designed and built for measuring and displaying noise pollution level directly. In addition, it displays the sound pressure level, the mean level, and the standard deviation of the level. The measurement is based on a 5 min interval, allowing 12 complete measurements per hour. The instrument has a dynamic range in excess of 60 dB and is automatic in operation, allowing its unattended use for long periods of time with a chart or digital recorder.

ISSN:0034-6748    

DOI:10.1063/1.1686012

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Fabrication of thin film refractory metal superconducting weak links by photoresist and selective anodization techniques is described. Structures as small as 0.3 &mgr; have been fabricated with registry of subsequent structures to a precision of better than 0.5 &mgr;.

ISSN:0034-6748    

DOI:10.1063/1.1686013

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A bridge method which allows the simultaneous measurements of the coupling coefficient and the loadedQof a single‐ended cavity is described. The measuring system consists of a ``magicT'' bridge and incident power monitor circuits. Two collinear arms of the magicTare terminated by the cavity under measurement and the built‐in short at equal distances. Measurements are made by comparing the reflected power from the bridge with the incident power on the cavity.

ISSN:0034-6748    

DOI:10.1063/1.1686014

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A Philips thermionic emission electron microscope has been converted into a photoemission electron microscope by the addition of a simple ultraviolet illumination system and an electron multiplier array for image intensification. Photoemission images are formed without heating or activation of the surface. One example includes the first electron optical image of exoelectron emission from an abraded metal surface.

ISSN:0034-6748    

DOI:10.1063/1.1686015

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A triggered air gap has been developed for inserting timing marks on the film of streaking cameras used in ultra‐high‐speed photography. The gap has a rise time ten times faster than existing xenon flashlamps. The peak output of 7 × 106cd/cm2(7Mcd/cm2) achieves the same film density as the lamps. This paper describes both the design used to achieve low inductance in the gap and the driving circuitry.

ISSN:0034-6748    

DOI:10.1063/1.1686016

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A Pyrex sample holder encloses a polytetrafluoroethylene container which seals the sample. The nuclear magnetic resonance (NMR) spectrum of fluorine in the material of the container serves as a reference.

ISSN:0034-6748    

DOI:10.1063/1.1686017

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A conventional electromagnet has been modified by using tapered pole caps with axial holes drilled through the pole cap faces to apply longitudinal fields to the absorber in Mo¨ssbauer absorption experiments. Fields in excess of 25 kOe are obtained with the apparatus described. In order to demonstrate the performance of the apparatus, spectra of the ferrite Li0.2Zn0.4Fe2.4O4are shown and the magnetic hyperfine fields at A and B sites are obtained.

ISSN:0034-6748    

DOI:10.1063/1.1686018

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A four‐decade, logarithmic count‐rate circuit with a log transistor as the feedback element in an electrometer amplifier was designed and constructed for measuring periodic or random inputs. This new design enables a much greater degree of miniaturization than possible with the conventional, parallel diode‐pump configuration. Pulses of constant charge are supplied to the log electrometer by a common‐base transistor current source that is driven by a stable univibrator. Frequency compensation of the electrometer is not required because of the stabilizing influence of a 0.1 &mgr;F feedback capacitor that maintains the output voltage ripple at < 1 mV peak‐to‐peak for periodic inputs. The electrometer output changes 1 V per decade from + 4 to 0 V as the average input rate increases from 10 to 105counts/sec. From 0 to 50 °C the total output voltage zero drift is < ± 10 mV and the 1 V per decade calibration changes < ± 10 mV. The maximum error of the logarithmic conversion is < 1% referred to the output voltage. A figure of merit for the output response to a step change in input frequency is defined as the number of pulses required for the output to reach 90% of the difference between the initial and final output voltages. This response number is plotted as a function of the ratio of the initial and final input rates.

ISSN:0034-6748    

DOI:10.1063/1.1686019

出版商:AIP    

年代:1973

数据来源: AIP