摘要:

A general review of thermometry is presented. Topics covered include the concept of temperature and temperature scales; the International Practical Temperature Scale (IPTS); the roles played by the Advisory Committee on Thermometry and its parent International Committe on Weights and Measures; anticipated improvements in an extension of the IPTS; recent advances in primary thermometry; and current developments of practice (including fixed points and interpolation devices, and practical temperature measurements at the secondary level).

ISSN:0034-6748    

DOI:10.1063/1.1136349

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The time constant for fluorescent decay of the redRlines of Ruby has previously been shown to be a monotonic function of temperature over a range of more than 200 °C. An optical thermometer using this effect has been constructed and has a resolution of ±0.3 °C. Improvements in digital signal processing may increase this resolution another factor of 16.

ISSN:0034-6748    

DOI:10.1063/1.1136350

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An SCR Marx circuit which is characterized as inexpensive and reliable, with no warm‐up or heater power has been constructed, tested, and utilized in a pulsed discharge experiment. The specific circuit design produced an output pulse of 13 kV with a risetime of 0.12 &mgr;s and a FWHM of 0.16 &mgr;s. With a 500 V self‐enclosed battery power supply, the pulse generator was insensitive to triggering by stray signals, with an observed jitter of ±50 ns in triggering a spark gap of 18 kV.

ISSN:0034-6748    

DOI:10.1063/1.1136351

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A single‐coil triple‐tuned NMR probe designed to simultaneously stimulate1H,2H and13C resonances is described. Isolation between the1H and13C channels is higher that obtained by the cross‐coil system and the1H decoupling efficiency is significantly increased. The basic idea can be applied to design probes for observing resonances of various other nuclei either in liquid or solid state.

ISSN:0034-6748    

DOI:10.1063/1.1136352

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We devised an apparatus and technique for loading diamond‐anvil cells with gases at high pressure. Cells were filled quickly and conveniently at room temperature with helium and hydrogen isotopes to initial densities exceeding those of the normal liquids. We report preliminary values of4He and D2melting points based on the ruby pressure scale and compare them with extrapolations from our earlier melting curves measured to 20 kbar in a piston‐cylinder device. Our filling procedure now makes it possible to use4He as a pressure medium in diamond cells. The technique is also useful for loading cells with gaseous mixtures.

ISSN:0034-6748    

DOI:10.1063/1.1136333

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A commercially available optical and fluorescence stopped flow apparatus has been adapted for thermal detection methods. A minor modification was sufficient to permit the measurement of kinetics of chemical reactions with half lives in the range of 15 ms to several seconds. A detection sensitivity of 1 m °C was obtained.

ISSN:0034-6748    

DOI:10.1063/1.1136334

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An active system for plasma density measurement using an amplitude modulated microwave carrier signal is described. For plasmas of higher density, IR or visible carrier signals may be used. Adjacent‐mode competition is avoided by choosing the wavelength of the modulating signal to be comparable to the active delay‐line oscillator’s feedback path length. Although the technique described is intended for use with plasma, it can be applied to measurements of other dielectrics.

ISSN:0034-6748    

DOI:10.1063/1.1136335

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An apparatus for the measurement of the absorption and magnetic circular dichroism (MCD) spectra of matrix‐isolated high temperature molecules is described. A conventional electromagnet capable of producing fields up to 5500 gauss (0.55 T) is shown to produce high quality MCD spectra. A closed‐cycle helium cryostat is used to provide the variable low temperatures required, while a commercial microcomputer furnishes the wavelength advance, the photoelastic modulator voltage control, and digital signal collection. A pseudodouble beam absorption apparatus provides an absorbance (logI0/I) measurement on the same matrix‐isolated sample used for the MCD measurement, enabling straightforward comparison of the two and facilitating interpretation of any MCDA1andC0terms that are observed. The absorption and MCD spectra of the &ggr;′ and &agr; bands of the diatomic TiO in an argon matrix (14 K) are presented to illustrate the power of the combined absorption/MCD matrix isolation method for the assignment of the excited electronic states of high temperature molecules.

ISSN:0034-6748    

DOI:10.1063/1.1136336

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A novel energy/momentum spectrometer consisting of a multigrid ion energy analyzer in tandem with an inflexion focusing magnetic sector momentum analyzer is described. The entire analyzer ion flight path may be negatively biased relative to the outer (grounded) instrument housing, enabling post acceleration (up to a few keV) of grid extracted ions from laser blow‐off plasmas or laser‐initiated vacuum arcs. Used as a time‐of‐flight momentum spectrometer, the instrument is shown capable of unraveling velocity distributions and relative abundances of ions of different charge in expanding laser blow‐off plasmas, even for a few keV initial ion energy spread. Used as a discharge ion analyzer, the high mass resolution of the instrument, (m/&Dgr;m=110), enables ion isotopic species of carbon, iron and copper to be readily separated and energy analyzed. A channeltron collector provides wide dynamic range (∼105) and high time resolution (∼1.0 &mgr;s), enabling detection of low abundance species such as polymer ions in carbon discharges.

ISSN:0034-6748    

DOI:10.1063/1.1136337

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A computer program is described, which permits rapid calculations of paraxial electron trajectories in multielement electrostatic cylinder lens systems. The method uses a ’’unified’’ data set for the electric potential of tube lenses with arbitrary voltage ratios, rather than solving Laplace’s equation numerically, thereby shortening the program coding drastically. With this program computer optimizations of long lens systems with respect to beam divergence and beam diameter can also be performed. Examples are given of the design of a multi‐element zoom lens and of the calculation of electron trajectories in 250 V acceleration tube with 36 electrodes.

ISSN:0034-6748    

DOI:10.1063/1.1136338

出版商:AIP    

年代:1980

数据来源: AIP