摘要:

The absolute signal and absolute noise behaviors of Auger electron spectrometers are analyzed for the pulse counting, analog amplification, beam blanking, and sinusoidally modulated differential modes. Measurements for a Varian 10‐keV CMA system and a VG Scientific Microlab support the theoretical predictions in detail. Measurements using a 5‐keV electron beam at 45° angle of incidence allow a figure of merit factorFto be derived such that the defined signal‐to‐noise ratio for the Cu L3M45M45intense peak is given byF(It)0.5, whereIis the beam current ( &mgr;A) andtis either the period averaging time or twice the exponential time constant (ms). It is shown that theFvalue using pulse counting is 20.5times that using current amplification, 2 times that using beam blanking, and 3.3 times that using modulated differentiation. TheFvalue, under specified conditions, allows a very broad characterization of the instrument’s sensitivity. The measuredFvalues for the above instruments are all very similar and are equivalent to a value of 40 in the pulse counting mode.

ISSN:0034-6748    

DOI:10.1063/1.1140230

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The construction and operation of a scanning positron microbeam is reported. The positrons are obtained from a doubly remoderated positron beam with a normalized brightness‐per‐volt of 1.8×105e+ s−1 cm−2 rad−2 V−1 Ci−1. The beam of 8000e+ s−1is brought to a 10×50 &mgr;m2focus by a sectored lens and is scanned across a test grid. Possible applications to defect spectroscopy and the observation of small samples will be discussed.

ISSN:0034-6748    

DOI:10.1063/1.1140231

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We reconsider the properties of the seven‐element electrostatic zoom‐lens system of Chutjian and Kuyatt [Rev. Sci. Instrum.50, 347 (1979)] from our experience with a ‘‘visual’’ beam‐tracing program, and propose a modified operation of this lens system to achieve simultaneously correct focusing, zero beam angle, and constant target size over the zoom range. Rational function fits to all driving voltages are given. A ray‐tracing program for a personal computer is described in the Appendix.

ISSN:0034-6748    

DOI:10.1063/1.1140232

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The resonance enhancement of an optoacoustic signal, generated in methyl alcohol vapor, is investigated with the objective of obtaining a reliable discriminator at reduced pump power levels. The 9P(36) pump line from a CO2laser is used throughout the study. The optoacoustic signal strength and resonatorQare measured at the fundamental longitudinal resonant frequency for various resonator geometries and vapor pressures. Resonators of length ranging from 12 to 24 cm are examined for tubes of inner diameter 7.5, 9.5, and 10.6 mm. The maximum vapor pressure for which a reliable discriminator is obtained is found to be 1 Torr. Both the optacoustic signal strength and the resonatorQincrease with increasing vapor pressure and decreasing resonator length. The highestQis obtained for the 10.6‐mm‐i.d. tubes. Using a resonator of the length 14 cm and 10.6‐mm i.d. at a vapor pressure of 1 Torr, it is found that a pump power as low as 0.4 W gives a reliable discriminator.

ISSN:0034-6748    

DOI:10.1063/1.1140233

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report on a newly built infrared spectrometer to be used for vibrational studies at the electrochemical interface. The usual way to select the weak interface absorption consists in changing the electrode potential and measuring the associated change in absorption. However, up to now it was difficult to benefit from both the advantages of using a lock‐in detection and Fourier transform spectroscopy. Our apparatus allows simultaneous use of these two techniques. This is achieved by using a slow scan speed (∼6 &mgr;m s−1) for the Michelson interferometer. The electrode potential may be modulated at a frequency as low as 100 Hz. The ultimate sensitivity of our apparatus corresponds to a relative change of transmitted light intensity of &Dgr;I/I∼10−6, for a measuring time of 45 min, in the 800–4200 cm−1range, with a resolution of 25 cm−1. Our ultimate resolution capability is 0.5 cm−1. Data are presented that have been obtained on then‐Si/acetonitrile interface using an attenuated total reflection geometry, which allows further improvement of the performances by one order of magnitude.

ISSN:0034-6748    

DOI:10.1063/1.1140234

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A high‐temperature IR‐transmitting absorption cell has been designed and tested. The cell is heated by utilizing the cell wall as the heating element. A PTFE (Teflon) gasket double‐window assembly allows temperatures as high as 500 °C to be attained. Temperature uniformity of 4 °C is observed, and preliminary absorption results by CO2at 10 &mgr;m are presented.

ISSN:0034-6748    

DOI:10.1063/1.1140235

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The characteristics of microchannel plates (MCPs) for detection of x rays have been investigated using synchrotron radiation in the energy ranges from 0.6 to 2.0 keV and from 5 to 20 keV. Microchannel plates are operated under the condition of an unsaturated pulse‐height distribution mode. The current response curve of MCPs is measured continuously with x‐ray energy variation for the first time. The experimental result of some discontinuous jumps in the response is obtained at the energies corresponding to the absorption edge of the MCP materials. In the low‐energy range (h&ngr;<2 keV), the dependence of the current response to the incident angle of x rays to the channel axis &thgr; is measured to be proportional to cot &thgr;, which is interpreted by the x‐ray absorption near the surface of MCP channel wall. While, in the high‐energy range (h&ngr;>5 keV), a weak dependence on &thgr; is observed, and is attributed mainly to the penetration of x rays through multiple channels.

ISSN:0034-6748    

DOI:10.1063/1.1140236

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A fiber‐optic temperature sensor, operating on the principle of differential absorption effects with temperature, has been constructed using visible wavelength sensing and a ruby fluorescence‐based internally generated reference scheme. Results of an investigation of the system and a comparison with previous work by the authors on a related system are reported.

ISSN:0034-6748    

DOI:10.1063/1.1140275

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Spectroradiometric temperature measurement techniques require a stable high‐temperature reference source. It is essential that the brightness temperature of this reference source be calibrated against an accepted standard. We show that the optimal choice for the operating temperature of the reference source is slightly higher than the medium under test. We consider the use of miniature quartz‐halogen lamps, as an alternative to the traditional tungsten ribbon lamp, as the reference source for emission–absorption pyrometry. The use of subminiature quartz‐halogen lamps can extend the optimum operating condition by over 500 K and are less prone to lamp envelope fouling than tungsten vacuum lamps.

ISSN:0034-6748    

DOI:10.1063/1.1140237

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A laboratory instrumentation system has been developed which provides flexibility for conducting an extensive range of thermal investigations of organic materials. Test samples can be of gaseous, liquid, solid, polymeric, composite, or even multiphase nature. This modular system uses an interchangeable test‐cell assembly concept for performing laboratory experiments and physical simulations. Incorporated in‐line instrumental analysis techniques provide sensitive and comprehensive effluent analyses of the thermal‐related degradation behavior.

ISSN:0034-6748    

DOI:10.1063/1.1140238

出版商:AIP    

年代:1988

数据来源: AIP