摘要:

It is shown that the original A˚ngstro¨m method of determining the thermal diffusivity of metals is not valid in the case of a specimen surrounded by a solid medium, and an appropriate modification is described. Several simplifications of this method are also presented and criteria for their validity given. An electronic system has been developed for automatic sampling and analysis of the temperature data. The new method has been applied to Cu under pressure, and the results show that the thermal conductivity rises by 6.4% up to 2.5 GPa (25 kilobar).

ISSN:0034-6748    

DOI:10.1063/1.1134585

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We describe an optical system which has been used in conjunction with a high pressure diamond anvil cell to obtain absorption, reflectance, and photoluminescence spectra. The system is shown to yield useful results to pressures at least as high as 200 kilobar.

ISSN:0034-6748    

DOI:10.1063/1.1134586

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We describe the technique and the results of a measurement of the width of a fine structure pulse from our L‐band electron linear accelerator. The pulse width was measured by measuring the width of the C˚erenkov light pulse generated by the electron beam using a streak camera–TV camera–computer system. With very low beam currents, a pulse width of 20 psec (FWHM) was measured, while at higher beam currents a pulse width of 27 psec was measured showing a space‐charge effect. In addition, a broad energy spectrum for the electrons or improper focusing into a 270° bending magnet was also shown to increase the pulse width of the beam after it had traversed the magnet.

ISSN:0034-6748    

DOI:10.1063/1.1134587

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A device is described which can produce images of small, low mobility (low energy) negative electric currents. The device can map the cross section of an impinging current density as small as −10−13A⋅cm−2with a spatial resolution of 102points per mm2. The charge carriers need an electrostatic energy of only ∼1 eV to be detected. A device for room temperature operation is easily constructed. With some modifications the device can operate at temperatures as low as 1 K.

ISSN:0034-6748    

DOI:10.1063/1.1134588

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

This project developed a device for measuring temperature in which the heat expansion of mercury is measured capacitively. Using this method, the step‐like movement of the mercury restricting the performance of conventional mercury‐in‐glass thermometers can be reduced. In our new devices, the average step is less than 1 mK. The instability of the electronic part with time appears to limit the measuring range to 3–4 decades. The device is particularly suitable for highly accurate remote measurement of temperature. Compared with other accurate electronic devices for measuring temperature, the device constructed is extremely inexpensive.

ISSN:0034-6748    

DOI:10.1063/1.1134589

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A method for fabrication of an inexpensive platinum electrode is presented. The process is based on the thermal deposition of a Pt film upon a glass substrate yielding a chemically inert electrode; the electrode is amenable to Pt blacking. The measured polarization capacitance for this electrode as a function of frequency is presented for both the bare and Pt blacked states.

ISSN:0034-6748    

DOI:10.1063/1.1134579

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A combined optical and electron spin resonance spectrometer is described. Construction details and typical kinetic data are presented.

ISSN:0034-6748    

DOI:10.1063/1.1134580

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An electronic circuit has been constructed which delivers constant power to a nickel wire, also functioning as a resistance thermometer. The temperature increase versus time,t, is linear in lnt, and the coefficient of slope directly yields the thermal conductivity of the medium surrounding the wire. Systematic errors due to finite time, wire length, and lateral extension of the medium and due to plastic deformation of the wire are analyzed. Temperatures are sampled automatically, and the digital data are reduced by means of an on‐line desk calculator. The thermal conductivities of AgCl and polytetrafluoroethylene have been measured up to 10 kilobar.

ISSN:0034-6748    

DOI:10.1063/1.1134581

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A system that permits the soft recovery of specimens shock loaded with a gas gun has been designed for dynamic fracture studies. Post‐impact damage to the specimen is minimized via the in‐flight capture of the projectile and flyer disk. The system has been tested for projectile velocities up to 0.32 mm/&mgr;sec.

ISSN:0034-6748    

DOI:10.1063/1.1134582

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A new method of measuring the complex permittivity in the time domain is proposed. By taking responses of a sample solution to a binary pseudorandom noise, a simultaneous measurement of all the frequency components are performed. Due to its high efficiency, an extreme reduction in measuring time together with low power excitation becomes possible. The Fourier transform of the response is multiplied by the Fourier transform of the binary pseudorandom noise and normalized; from the transfer function thus obtained, the complex permittivity is calculated, and the dispersion profile is displayed. A measuring time of 28 msec is required to obtain the dielectric dispersion profile from 71 Hz to 36 kHz. This is demonstrated for a solution of poly‐&ggr;‐benzyl L‐glutamate.

ISSN:0034-6748    

DOI:10.1063/1.1134583

出版商:AIP    

年代:1976

数据来源: AIP