摘要:

We describe a single‐sideband frequency demodulation scheme with large dynamic range which gives linear response and is capable of shot‐noise‐limited performance when used with time‐resolved pump and probe, polarization, and three‐ and four‐wave mixing spectroscopies.

ISSN:0034-6748    

DOI:10.1063/1.1137591

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A versatile, variable‐temperature (3–350 K continuous), vacuum cold‐finger, solid‐state nuclear‐magnetic‐resonance (NMR) probe is described and its characteristics in several applications are discussed. The single‐coil probe is specifically designed for use in superconducting magnets with bores as small as 2.5 in. and is suitable for both single‐ and double‐resonance experiments. The tuning arrangement allows for multinuclear data acquisition without the necessity of breaking the vacuum. Various adaptations to the cold finger suitable for a variety of different solids, e.g., powders, amorphous materials (glasses), condensables, and single crystals are presented including a single‐axis goniometer operable over the entire temperature range.

ISSN:0034-6748    

DOI:10.1063/1.1137592

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A high‐pressure (P<3.6 kbar) multimode resonator system suitable for low‐temperature (4.2 K) microwave measurements over a wide range of frequencies (21–215 GHz) is described. A simple reflection spectrometer is used for low frequencies (<50 GHz). At higher frequencies, an unusual transmission resonator scheme is used which requires only one microwave window.

ISSN:0034-6748    

DOI:10.1063/1.1137593

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A description is given for an automated method for determining dielectric constant and loss by the measurement of the time response of the dielectric to a step voltage. Attention is paid to the circuits necessary to achieve high accuracy (0.1%) and high sensitivity (tan &dgr;=10−5) over audio and subaudio frequencies (104to 10−4Hz). These include a 100‐V step generator accurate to 5 ppm, a charge detector with a time‐independent bias current of 30 fA, and a clock that can control sampling time from 5 &mgr;s to 10 s. In addition, a numerical Laplace transform, based on a cubic spline, is described that preserves the accuracy of the time data when they are transformed into the frequency domain.

ISSN:0034-6748    

DOI:10.1063/1.1137594

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A simple, compact, UHV compatible Mott polarization analyzer is described that employs electron accelerating voltages in the range 20–40 keV.The analyzer provides excellent discrimination against inelastically scattered electrons and has the advantage that the major portion of the apparatus, and the scattered electron detectors, are operated near ground potential. The efficiency of the analyzer, ∼2×10−5, is competitive with those provided by other polarimeters. The analyzer can measure the polarization of electron beams having currents as low as ∼10−13A and is suitable for use in a wide variety of experiments involving polarized electron beams.

ISSN:0034-6748    

DOI:10.1063/1.1137595

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Although the spatial resolution of a scanning Auger microprobe is limited by its electron optics, its effectiveness for the analysis of semiconductor devices that have features of interest comparable in size to the diameter of the analyzing electron beam is enhanced by a variation in the method of signal detection. Signal detection in an Auger spectrometer is most often accomplished using phase‐sensitive detection. The modulating signal required in the phase‐sensitive detection process is applied to the electron energy analyzer. Instead, by applying the modulating signal directly to different electrically isolatable regions of a device, only those Auger electrons originating in a particular region are detected. By rejecting signals from regions adjacent to a modulated region, Auger spectra characteristic only of the region of interest are obtained without spurious contributions from adjacent areas inadvertently illuminated by the analyzing beam.

ISSN:0034-6748    

DOI:10.1063/1.1137566

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A free surface gas/oil interface has been constructed to aid in the comparison of gas piston gauges with oil piston gauges. A coaxial three‐terminal capacitor partially immersed in the oil and partially in the gas permits the determination of hydrostatic heads and differential pressures between the piston gauges. The interface has been used in the comparison of primary standard gas and oil piston gauges with an average standard deviation about mean pressures of 4.5 Pa (6.5×10−4psi) over the range of 0.4 to 4 MPa (60 to 600 psi).

ISSN:0034-6748    

DOI:10.1063/1.1137567

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A diamond‐anvil high‐pressure cell for single‐crystal x‐ray diffraction studies is described. The cell is suited especially to four‐circle diffractometers. The important feature of this device is that, compared to previously reported cells for single‐crystal x‐ray studies, a greater portion of the reciprocal space can be observed. All structure factors up to a &thgr; limit, depending on the design of the cell, can be measured. Thus, the probability of solving complicated unknown structures is increased. The major disadvantage of the cell is the limitation of the highest achievable pressure of 35 kbar, caused by failure of the beryllium gasket.

ISSN:0034-6748    

DOI:10.1063/1.1137568

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

We describe a support for the University of Rochester gravitational wave detector. The support is a two‐stage filter with springs made of aluminum and a brass intermediate mass. With this support we have measured a mechanical quality factor for the fundamental mode of a 200‐kg aluminum cylinder of 2.2×107at 2302 Hz at 4.2 K. The filter attenuates vibrations by −130 dB at this frequency.

ISSN:0034-6748    

DOI:10.1063/1.1137579

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A versatile double‐crystal topography camera is described which has provisions for both image detection and precision rocking curve analysis for a wide variety of single‐crystal samples. The camera has a variable base separating the two crystals and this base is rotatable for working with a range of diffraction vectors. The accuracy of the second crystal goniometer stage is of the order of 0.2 arc s. An example of typical data taken with this camera is displayed.

ISSN:0034-6748    

DOI:10.1063/1.1137580

出版商:AIP    

年代:1984

数据来源: AIP