摘要:

Niobium‐on‐sapphire resonators have been constructed as sensor elements for accelerometers in gravitational wave antennae. In their present form the resonators constitute small simple sensor elements for a wide range of applications where displacements take place, such as seismometry, gravimetry, thermal expansion measurements, as well as gravitational wave antennae. Radio‐frequency losses in the niobium‐sapphire interface have been observed. These limit the resonatorQto less than 105and show a strong power dependence. Several methods of fabrication of the niobium‐on‐sapphire circuits have been investigated. Complete details for construction are given. An accelerometer based on these resonators is described in an accompanying paper.

ISSN:0034-6748    

DOI:10.1063/1.1135816

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An accelerometer is described which uses a rf niobium‐on‐sapphire resonator as its sensor element. The accelerometer uses a magnetically levitated spool as a test mass and the spool modulates the inductance of the resonator; its position is servo controlled to maintain the resonator at the external rf excitation frequency. The accelerometer has high sensitivity over the full audio frequency range, but is optimized for frequencies between 100 Hz and 1 kHz, where the calculated displacement sensitivity approaches 10−15cm for a 1 Hz measurement bandwidth. The system noise sources are analyzed and possible improvements are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1135817

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The thermal relaxation method is used to measure heat capacities of small samples in the temperature range around room temperature. The calorimeter is designed to measure under heat exchange gas and a steplike excess heat is applied to the sample by irradiation from a lamp.

ISSN:0034-6748    

DOI:10.1063/1.1135818

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A digital lock‐in detection technique which overcomes some practical limitations of the analog lock‐in amplifiers is described. An example of implementation is given, based on multichannel pulse analyzers. Some representative results are reported for two typical application fields of lock‐in techniques, namely optical spectrometry and semiconductor profiling withC–Vtechniques. Advantages and limitation of the technique are discussed as well as adaptation to various modulation waveforms.

ISSN:0034-6748    

DOI:10.1063/1.1135819

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A new type of electron impact spectrometer using an axial magnetic field for electron collimation is described. The feasibility of this apparatus for collision studies at low impact energies (0.1−30 eV) is demonstrated with vibrational and electronic excitation in He, N2, CO, and C2H2. The potentials and limitations of this new approach are also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1135820

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An apparatus of split‐octahedron type has been developed for the study of x‐ray diffraction at high pressure. The apparatus consists of a cylinder, a sphere, and an octahedron, all split up and assembled in a multistaged arrangement. Three ways of splitting the innermost octahedron are utilized in matching the cell geometry to the standard camera method. High pressures in excess of 220 kilobars can be generated in the center of the split octahedron by using a composite mixture of diamond powder and epoxy resin as a pressure‐transmitting medium. The pressures required for the semiconductor‐to‐metal transitions of ZnTe, ZnS, GaAs, and GaP are determined by simultaneously monitoring the electrical resistance of the semiconductors and the lattice parameter of sodium chloride.

ISSN:0034-6748    

DOI:10.1063/1.1135821

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Eight circuits designed for producing a signal that is a linear function of temperature change, utilizing a single thermistor as the temperature‐sensitive element, are examined. All are found equal in linearizing capability, including five circuits containing operational amplifiers. This finding does not apply to certain linearizing circuits such as those containing logarithmic amplifiers, some of which may be expected to have a linearizing capability greater than that of the circuits examined.

ISSN:0034-6748    

DOI:10.1063/1.1135812

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A high‐resolution system for measuring the magnetic fields near recording heads and disks has been built. The perpendicular field components close to the head and disk surfaces are measured with an InSb Hall probe which is moved point‐by‐point under computer control. The computer also records the magnetic field strength as a function of position in a plane parallel to the head or disk surface. The active area of the probe is 2×2 &mgr;m and a roughly 1‐&mgr;m separation between the probe and the surfaces being measured can be obtained. Measurements of the fields near transitions on a particulate disk and near the gap in in a ferrite recording head are presented and compared with calculated field distributions.

ISSN:0034-6748    

DOI:10.1063/1.1135813

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A soft x‐ray appearance potential spectrometer using a channelplate detector is described and evaluated. This detector is much more sensitive than the metal photocathode in common usage and provides useful SXAPS spectra at primary electron currents of less than 10 &mgr;A. Operation of the detector at high x‐ray fluxes is limited by saturation effects which can be minimized by the proper choice of channelplate and geometry.

ISSN:0034-6748    

DOI:10.1063/1.1135814

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

By using a [(signal) + (noise)] − (noise) digital averaging technique in order to reduce the offset drift, an improvement of about a factor 100 has been obtained in the sensitivity of a pyroelectric detector array (PDA). Different applications of the apparatus for measurement of infrared and far‐infrared beam characteristics are also presented.

ISSN:0034-6748    

DOI:10.1063/1.1135815

出版商:AIP    

年代:1979

数据来源: AIP