摘要:

A method using standard waveguide components is described for accurate measurements of complex dielectric permittivity of low, medium, and high loss liquids up to 150 GHz. Measurements on cyclohexane, carbon tetrachloride, chloroform, and 1,1,1‐trichloroethane are reported. The data of chloroform are compared with results from different authors, confirming an additional absorption above 40 GHz. The method is also suitable for determining the level of the continuous spectra obtainable by far infrared Fourier transform spectroscopy.

ISSN:0034-6748    

DOI:10.1063/1.1686676

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An autofrettaged high pressure aluminum chamber for pressures up to 3 kilobar for inelastic neutron scattering experiments has been designed and constructed. The autofrettage technique shows some advantages with respect to the simplicity and the flexibility of construction as compared with other methods.

ISSN:0034-6748    

DOI:10.1063/1.1686677

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The design of electronic circuitry is described that has the capability of measuring independently the bias dependence of the first derivativesdI/dV(dynamic conductance) anddV/dI(dynamic resistance) and the second derivativesd2I/dV2andd2V/dI2of a tunneling current‐voltage (I‐V) characteristic over a wide range of junction impedances (less than 1 &OHgr; to greater than 104&OHgr;). Connections to the sample are four terminal so that problems with lead resistance are eliminated. Resolution in the measurement of the first derivatives is better than one part in 104, and problems with long‐term drift are obviated by the use of feedback. Modulation levels at the sample junction, both at constant current and constant voltage, are conveniently monitored with a calibrated lock‐in amplifier and can be easily changed. The circuitry has been operated successfully with voltage modulation levels across the junction ranging from 1.0 &mgr;V to 2.5 mV rms. Data are presented on Al&sngbnd;I&sngbnd;Pb and Al&sngbnd;I&sngbnd;AuPb3tunnel‐junction samples to illustrate the capabilities of the system.

ISSN:0034-6748    

DOI:10.1063/1.1686678

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A general purpose sequencing and timing computer with a program capacity of 100 instructions is described. Program storage is by means of a low cost shift register memory. Input, output, and branching instructions are provided, along with a novel instruction for the creation of ``DO'' loops. Complex pulse patterns with pulse durations ranging from 1 &mgr;sec to arbitrarily long times can be easily programmed. Up to eight external devices can be controlled without additional demultiplexing.

ISSN:0034-6748    

DOI:10.1063/1.1686679

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A method is described to directly measure mean spiral diameter in a magnetically confined electron beam. In collision experiments, spiraling affects polarization measurements and effective path length assessment; and in experiments using colliding beams, the collision energy or energy spread can be significantly altered. The technique described here allows experimental correction for these effects. Magnitudes of transverse velocities from various causes leading to spiraling are estimated on the basis of models. A gun designed for use in crossed beam electron‐ion excitation experiments is described, and results of tests on spiraling and space charge effects for this gun are given. The tests generally indicate the modeling to be correct. Judicious choice of operating conditions led to path length corrections as small as 4±2% at 3 eV, decreasing to 0.25±0.2% at 200 eV.

ISSN:0034-6748    

DOI:10.1063/1.1686680

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A sensitive x‐ray detection system has been used in the recording of soft x‐ray appearance potential spectra with an electron excitation current of a few microamperes covering a sample area of 1 cm2. The system included a 6&mgr; thick aluminum foil, a cesium iodide photocathode, a continuous‐channel electron multiplier, and conventional pulse‐counting electronics. The aluminum foil was placed over the entrance window of the detector in order to filter out the ultraviolet and extreme‐soft x‐ray emissions from the sample prior to detection of the soft x rays that passed through the foil. The transmitted soft x rays were incident on a cesium iodide photocathode and the resulting photoelectron events were individually detected with a high‐gain electron multiplier whose output pulses were processed with pulse‐counting electronics.

ISSN:0034-6748    

DOI:10.1063/1.1686681

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The thermal relaxation method is used to measure heat capacities of small samples from 0.060 to 1.2 K. The calorimeter incorporates a low heat capacity holder, and is designed to be used in conjunction with a3He&sngbnd;4He dilution refrigerator. The accuracy was checked by measuring a 2 g copper sample. A least squares fit of the copper data yields a &ggr; value of 0.688 mJ (K2g at.)−1which agrees to 1.0% with published values of &ggr; for copper. The data exhibit a standard deviation of 5.6% around the fit.

ISSN:0034-6748    

DOI:10.1063/1.1686682

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new method to record the time dependence of a transient absorption or emission spectrum produced by a single pulse of radiation is described. The time‐resolved spectrum is produced by an image converter camera with streak capability. The streak image is scanned by a TV camera, the output of which is transferred to a computer. Apart from its time‐saving aspect, the method is particularly useful for experiments with rare or radioactive chemicals.

ISSN:0034-6748    

DOI:10.1063/1.1686683

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Accurate calculations of focal properties of the two‐tube electrostatic lens are extended to cover a range of voltage ratios from 1.1 to 10000. The accuracy of the calculations is discussed in detail. For voltage ratios near 6400 the lens is found to be telescopic. Results are given in tabular form and asP‐Q(object‐image) curves. A simple analytical form for the focal properties of lenses with near‐unity voltage ratios is given.

ISSN:0034-6748    

DOI:10.1063/1.1686684

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The use of matrices to represent electron lenses is discussed. It is shown that it is more convenient and natural to represent a lens by a matrix and that the matrix elements show a more regular behavior than do the focal properties. Thus matrices are more convenient to use in computer programs. Matrix elements for the two‐tube electrostatic lens are presented and their properties discussed. A simple analytical form for the matrix elements of lenses with near‐unity voltage ratios is given.

ISSN:0034-6748    

DOI:10.1063/1.1686685

出版商:AIP    

年代:1974

数据来源: AIP