摘要:

The design and construction of a double focusing uniform field magnetic electron spectrometer are described. The pole pieces of the magnet are curved in an effort to correct all median plane aberrations and thereby increase the collecting power. The spectrometer has been installed on a scanning microscope which uses a field emission gun to produce a 100 Å probe. Energy analysis of the transmitted electrons as well as filtered diffraction patterns can be obtained from areas as small as 100 Å in diameter. In addition, the area under study can be observed directly in the scanning transmission mode, using electrons of any selected energy loss. A resolution of the spectrometer of 2 ppm at an electron energy of 20 keV is shown and the measured second order aberration coefficient is <5% of that of an equivalent straight edge sector magnet. Also, the solid angle for collection of electrons is about an order of magnitude greater than that of the equivalent straight edge magnet at any given resolution. Experimental results in all modes of operation are presented.

ISSN:0034-6748    

DOI:10.1063/1.1685116

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A theoretical analysis shows factors which affect the onset of nonlinear response of the anode current of a photomultiplier to the light intensity incident on the photocathode, when the dynode voltages are provided by a linear resistor chain. The percent deviation from linearity of the anode current is shown to be independent of the number of dynodes and the gain per stage. The conditions do depend on the form of the gain per stage which is assumed to depend on parametersg=p+q. The parametergis shown to have approximately the same value for a number of photomultipliers, so that any significant differences in the initial deviation from linearity would be attributed to the ratiop/q. This ratio has not been measured, but a method of doing so is described. Some measurements of the deviation from linearity are discussed in terms of the analysis, and the indications from that limited sampling are that one can expect deviations to be less than 3% for all photomultipliers when the anode current is less than 0.1 the current in the final resistor of a linear bleeder chain.

ISSN:0034-6748    

DOI:10.1063/1.1685117

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Two different methods of orienting piezoelectric crystals are described. One method depends upon the symmetry of the phase velocity of elastic surface waves as a function of propagation direction in a crystal face. The other method utilizes the symmetry of the piezoelectric coupling strength. Measurements in theZplanes of &agr;‐quartz and LiNbO3reveal accuracies better than 10′ for the determination of the nonoptic axes.

ISSN:0034-6748    

DOI:10.1063/1.1685118

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An apparatus is described which measures the shear strength of bulk materials in the temperature range from 25 to 350°C, in the pressure range from 20–80 kilobars. The strain rate in this pressure and temperature range can be varied between 3.5×10−7and 3.7×10−1sec−1. Some data on OFHC copper are given to indicate the type of results obtained from this apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1685119

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Two types of cylindrical reentrant cavities are described for magnetic resonance and ultrasonic applications in the 0.1–‐1.0 GHz frequency region. The physical size of these cavities is reduced by introducing large capacitive and inductive elements into the cavity. Tuning, rf coupling, and temperature control techniques are described for operation at low temperatures.

ISSN:0034-6748    

DOI:10.1063/1.1685120

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A system is presented for the time resolution of plasma potential using gridded electrostatic analyzers. The novelty of this method is the separation of consecutive current‐energy characteristic curves and their display on a CRT. Using a 20 kHz bias signal, 30–50 consecutive 25 &mgr;sec sweeps are displayed on a CRT in a 1 msec time interval. This is sufficient for the study of low frequency plasma fluctuations in transient confinement experiments. Application to the DCX‐2 mirror machine is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1685121

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Several pulsed NMR experiments using rapidly repeating pulse sequences are described. Theoretical results for magnetization as a function of pulse spacing &tgr; are given for cases where the Bloch equations apply, and compared with experiments. These results suggest a simple method of rapid signal accumulation whenT2*<T2,T1, that is, when resolution is limited by magnet inhomogeneity.

ISSN:0034-6748    

DOI:10.1063/1.1685122

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The design of a simple parallel current regulation circuit has the following bandwidths: 10 MHz for voltage regulation, 0.2 Hz for the primary reference voltage circuit, and 20 Hz for amplifier noise. These characteristics compare very favorably to other voltage regulation circuits which are used in design of secondary reference voltage sources.

ISSN:0034-6748    

DOI:10.1063/1.1685123

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The normal impulse accommodation coefficient is measured with a torsion balance. Data for Ar, N2, O2, H2, N2O, CO2, stainless steel, and glass are given. The absolute error of the relative method used is &Dgr;&sgr;′=0.05. The measurements occur at room temperature.

ISSN:0034-6748    

DOI:10.1063/1.1685124

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The magneto‐optical Faraday effect associated with certain paramagnetic ions has been utilized to construct an optical magnetometer suitable for studying the magnetic properties of hollow cylinder superconductors. As an instantaneous field detector, the response of the system in general is limited only by the spin‐bath relaxation time of the paramagnetic ion‐host crystal system being used. The magnetometer has the advantage of requiring no moving parts and also avoids the necessity of having to extract a low level voltage signal from the low temperature environment. Also, since the detector is an insulator, there are no undesirable time derivative of field signals generated in its use. The operating field range is limited by the sensitivity desired in a given experiment. For fields up to 13.5 kOe at a temperature of 2.15 K, the sensitivity for the analyzer oriented at 45° with respect to the plane of polarization of the emergent light is at worst ±9.3 Oe. The text lists the sensitivity at various other fields and temperatures in tabular form. Initial results on superconducting hollow cylinder niobium are also presented.

ISSN:0034-6748    

DOI:10.1063/1.1685125

出版商:AIP    

年代:1971

数据来源: AIP