摘要:

We describe the construction and performance of a new electron spectrometer for analysis of low kinetic energy electrons, 0–2000 eV. The design of the analyzer is based on computer calculations and combines many favorable properties of both the retarding and the deflection energy analyzer. The energy analyzer consists of a set of electrodes with cylindrical symmetry and a planar retarding field grid followed by an electrode system with postmonochromatic action. Therefore a differential spectrum is obtained directly. The performance of the analyzer is discussed in terms of resolution, sensitivity, luminosity, and signal‐to‐background. The resolution achieved is 0.5%, with a resolution of 30 meV, making it possible to resolve and study electronic vibrational levels in atoms and molecules. A few spectra of nitrogen and argon are shown as representative of the performance of the new analyzer.

ISSN:0034-6748    

DOI:10.1063/1.1686105

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The technique of field spinning Zeeman modulation in microwave spectroscopy has been extended to long cylindrical absorption cells by using orthogonal pairs of cosine distribution magnets. This magnet configuration permits economical application of the field spinning approach to rather long path length, large diameter cells with substantial homogeneity of the field. Fields adequate for microwave spectroscopy may be obtained even within a metallic (preferably austenitic stainless steel) cylindrical vacuum chamber. The solutions of Maxwell's equations for an idealization of the latter situation of an intervening conducting layer are presented, so that with the formulas given here, one may easily calculate available field as a function of geometry, amplifier power, modulation frequency, and circuit parameters. Two new microwave spectrometers have been constructed using such magnets, and our experiences with applying the field spinning technique to them will be discussed. Because the absorption cells are discharge tubes, we will consider the effects which the presence of the plasma has on the field spinning modulation method. While the plasma does give rise to the complication of a nonflat base line, it will be demonstrated that this can be held to quite manageable levels over a wide range of conditions. The spurious baseline fluctuation is likely to be observed in other configurations of Zeeman modulation of a plasma sample and appears to be related to a modulation of the plasma density and the resultant change in its refractive index.

ISSN:0034-6748    

DOI:10.1063/1.1686106

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A microwave spectrometer which utilizes the positive column of a dc glow discharge as its sample region has been constructed and operated successfully. This instrument employs free space microwave propagation through a large industrial Pyrex pipe, along with Zeeman modulation, and is intended for the study of transient paramagnetic molecules which are likely to be found in active discharges. This spectromenter features no mechanical tuning, instantaneous broad band width, resolution limited by Doppler broadening, and sensitivity comparable to that of conventional Stark modulated waveguide cells. Extensive observations primarily of the microwave spectrum of the OH radical in a water vapor discharge, have been made in order to delineate the range of application of this technique and to determine the effects of various operating parameters on the spectrum observed. Although the glow discharge is an extremely complicated phenomenon and is capable of manifesting its complexities in the behavior of our spectrometer, a wide range of conditions exist in which the presence of the plasma in the transmission path has negligible impact on the microwave spectrometer signal. Theoretical considerations of basic plasma physics will be employed to support the proposition that this is not unexpected and that a wide range of microwave spectroscopic studies of plasma samples are possible.

ISSN:0034-6748    

DOI:10.1063/1.1686107

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An inexpensive sampling circuit is described which allows high frequency repetitive signals to be plotted on anx ‐ yrecorder. The minimum sample width of 100 nsec is short enough that the effective high frequency 3 dB down point is about 6 MHz. The circuit includes provisions for signal averaging which allows significant improvement in the signal‐to‐noise ratio in many situations.

ISSN:0034-6748    

DOI:10.1063/1.1686108

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Increased interest in the use of the scanning infrared camera as both a diagnostic and research tool by the medical profession has led to the need for an external temperature reference. The scanning infrared camera detects the infrared radiation leaving a surface and converts the energy into a visual image which is photographed and termed a thermogram. This paper presents a thermal reference made by constructing an extended surface or fin in such a way as to produce a linear temperature profile down the fin axis. A fin was made following the theoretical model and tested. The resulting fin was quite linear and provides an excellent thermal reference.

ISSN:0034-6748    

DOI:10.1063/1.1686109

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An apparatus is described for ``short sample'' testing at high currents using the induced current method. Primary currents of 100 A would produce up to 16 000 A secondary current. The method of measuring the secondary current and results are given.

ISSN:0034-6748    

DOI:10.1063/1.1686110

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An analytical fit has been derived for the transfer function of a logarithmic electrometer utilizing a p‐n junction diode as a feedback loop element. Elementary semiconductor theory has been used to describe the diode current‐voltage characteristic, and the diode ohmic resistance and an external parallel resistance have been included in the circuit analysis. A temperature correction has been applied to account for a difference in the temperature of the diode during calibration and during the taking of data. The analytical fit with temperature correction is believed to be accurate to better than 10% of the absolute current input over seven current decades.

ISSN:0034-6748    

DOI:10.1063/1.1686111

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A modification of the absolute, longitudinal, steady‐state method of measuring thermal conductivity at low temperatures using one calibrated thermometer is described. By this method the effects due to any type of constant extraneous heating are completely canceled. The method is applied to measure the thermal conductivity of machined brass between 0.3 and 2 K.

ISSN:0034-6748    

DOI:10.1063/1.1686112

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

This paper describes an instrument that measures the transit time of a modulated light beam out and back over the path whose length is required. The instrument has a digital readout and an rms (1&sgr;) accuracy of ±0.08 mm on a single measurement over ranges up to 60 m. The measurement time is 2.7 sec.

ISSN:0034-6748    

DOI:10.1063/1.1686113

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A high‐speed X‐radiographic camera to radiograph blowoff products from materials subjected to high‐energy deposition by pulsed electron beams is described. Information obtained is average material density as a function of time and distance from the sample surface and is used to improve predictive hydrodynamic models. The camera design overcomes the difficult diagnostic problems of intense background radiation (bremsstrahlung), scattered electrons and electromagnetic interference usually associated with the electron beam environment. Conventional x‐ray film is mounted on a disk which rotates inside of a shielded housing. Data are recorded through a slit in the housing near the edge of the film disk (polar coordinate geometry) in either a flash (framing) or continuous (streak) mode. X‐ray energies used were 20–30 keV. Maximum speed of the film past the slit is approximately 0.04 cm/&mgr;sec.

ISSN:0034-6748    

DOI:10.1063/1.1686114

出版商:AIP    

年代:1973

数据来源: AIP