摘要:

A focussing monochromator array for detection of fluorescence EXAFS (Extended X−ray Absorption Edge Fine Structure) is described. The array is made of LiF crystals, specially prepared for large mosaic spread. Design criteria, performance specifications, and details of fabrication and crystal preparation are given.

ISSN:0034-6748    

DOI:10.1063/1.1136373

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A computer‐automated thermal relaxation calorimeter for use in the temperature range 4–380 K is described. The system can be utilized to make absolute measurements on fairly small (20 mg.) samples which may be of low thermal conductivity. A new hybrid sweep‐decay mode of operation for measuring heats of transition is demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1136374

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

When measuring pressures in the diamond anvil cell, undersirable line broadening and wavelength shifts result if small ruby crystals are used in a calibration system designed for large ones. These effects can be eliminated through the proper choice of objective lens, condensing lens, and slit system. Using such a system, we obtained excellent results with samples as small as 30 &mgr;m. In addition, we describe the use of the spectrum from a neon light to provide an internal wavelength standard during the measurement of the ruby spectrum. This eliminates the stripchart ‐ wavelength drive synchronization error, a potential source of large errors. A calculation of the estimated error associated with a typical pressure measurement indicates that, for small ruby samples, the pressure can be determined with a precision of ±0.5 kbar.

ISSN:0034-6748    

DOI:10.1063/1.1136375

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A study has been made of the resistance pressure characteristics of a number of Speer carbon resistors in the temperature range between 295 K and 76 K under hydrostatic pressure of up to 10.5 kbar. It is found that the resistance of the resistors decreases markedly with pressure. The results are quite reproducible and the effect of hysteresis is reduced after several pressure treatment.

ISSN:0034-6748    

DOI:10.1063/1.1136376

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A stopped‐flow apparatus is described for the rapid mixing and subsequent study of two dissimilar fluids under pressures up to 1200 bar. The device consists of two identical pressure chambers which contain the two fluids, a third pressure chamber which contains gas to maintain the pressure in the system, an optical port for photometric observation, and various connections. The device has been used to measure reaction times on the order of a hundred milliseconds to tens of seconds, using a maximum of 2 ml of each reagent per experimental determination. The dead time is found to be 5–25 ms with minium average flow velocities of 2.0 m/s. The construction and operation of the device are described and examples of water transport data in red blood cells and the bromophenolblue indicated chemical reaction of NaHCO3and HCl under pressure are presented.

ISSN:0034-6748    

DOI:10.1063/1.1136377

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Properties of pulsed gas lasers pumped by LC inversion circuit made of BaTiO3and SrTiO3series ceramic capacitors were experimentally investigated. The effects of a decrease in capacitance at higher charging voltages on TEA CO2and TE N2laser performances were clarified in terms of discharge voltage, current, power pulse, real stored energy and the energy deposited into the discharge load. Laser performances of the TEA CO2and TE N2lasers with the SrTiO3series capacitor used as an energy storage element of the LC inversion circuit were found to be superior to that of the BaTiO3series capacitor used.

ISSN:0034-6748    

DOI:10.1063/1.1136378

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A new submicron particle counter using a low output He–Ne laser (unpolarized, 8 mW) is proposed forinsitumeasurement of particulates. The design is based on calculations and experimental checks of factors governing the signal‐to‐noise ratio. Right angle scattering is found to be the most suitalbe optical system for eliminating miscellaneous noise and fundamental noise components derived from the carrier gas. The present version of the instrument with nine channels is constructed so as to minimized the noise level by reducing the sensing volume. This instrument can actually measure correct size distributions from 0.1 to 10 &mgr;m without detectable coincidence loss, at environmental particulate concentrations of up to 5×104/cm3.

ISSN:0034-6748    

DOI:10.1063/1.1136379

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A novel system has been developed for the direct measurement of acoustic displacement at a liquid–solid interface which is useful in the observation of leaky wave and related beam‐shift phenomena. Theory predicts that under certain conditions the acoustic field configuration is sensitive to material characteristics such as grain structure and hence assessment of this sensitivity is relevant to ultrasonic surface evaluation. The system utilizes a scanning laser probe together with knife‐edge detection; it permits rapid data acquisition, is remarkedly stable and easy to align, and provides linear maps of field intensity with minimal corruption even with acoustic transducer electrical input levels in the submilliwatt range.

ISSN:0034-6748    

DOI:10.1063/1.1136380

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A pulsed discharge lamp containing Hg vapor suitable for kinetic spectroscopy in the nanosecond time range is described. The spectral output is practically the same as that from a conventional low pressure mercury resoance lamp. The light intensity of the 253.7 nm resonance line is about 1010photon/pulse. The width of light pulses is about 10 ns, except at 253.7 nm, which pulse width is about 40 ns. The repetition rate is 5–10 kHz. Quenching rates of Hg(3P1) atoms by H2, C2H4, CO, and NH3are obtained by measuring decay rates of the 253.7 nm resonance line.

ISSN:0034-6748    

DOI:10.1063/1.1136381

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A negative helium ion beam of 70 mA at 10.5 kV has been produced by charge exchange in sodium. The production is studied as a function of sodium line density, beam energy and background helium gas density. The characteristics of this high current He−source are analyzed to determine the design requirements for He−beam generation in the range of tens to hundred of milliamperes.

ISSN:0034-6748    

DOI:10.1063/1.1136363

出版商:AIP    

年代:1980

数据来源: AIP