摘要:

A novel technique has been developed which allows a quadratic magnetic field to be continuously varied (via a superconducting flux transformer) from the outside of an ultrahigh‐vacuum container placed within a superconducting solenoid. Enclosed within each of these vacuum vessels is a high‐precision (compensated) Penning trap which is used in a variety of geonium experiments at the University of Washington. By varying the dc current in an outer (normal) primary solenoid, the secondary current flowing within a shorted superconducting loop is varied accordingly. The superconducting loop need only be placed in a cylindrically symmetric position within the Penning trap in order to generate theB2term, and with a clever choice of geometry, the zeroth‐order term can be totally eliminated. As an additional highlight, the uniform field from the main solenoid is drift stabilized to the same degree as the basic cancellation and further, an auxiliary trim coil can be used to fine trim the zeroth‐order null.

ISSN:0034-6748    

DOI:10.1063/1.1138875

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Prototypes of magnetically suspended rotors for centrifugation of cells, organic and inorganic solutions, and gases are Fe‐containing glass and metallic hollow microspheres 0.1–2 mm in diameter, composite steel‐glass disks up to 1 cm, and microspheres of porous steel and Fe‐impregnated porous glass. Fe‐coated microcapsules with cells can be used for lower centrifugal forces. Predictable applications include cell hybridization and homogenization, spinning of samples at the ‘‘magic angle’’ in nuclear‐magnetic resonance (NMR), intensification of nuclear fusion by high‐speed rotation of microspheres with deuterium and tritium, and other examples. Rotor contents can be examined under the microscope during centrifugation, or the spinning rotor can be frozen and its contents freeze dried for further examination.

ISSN:0034-6748    

DOI:10.1063/1.1138876

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new computed tomography imaging device that allows four orders of magnitude improvement in temporal resolution over currently available systems is described. Using 21 simultaneously triggered flash x‐ray sources and 21 detector arrays, density resolution of several percent for a 1‐cm region, lateral spatial projection resolution of 2 mm on a 200‐mm object, and a temporal resolution of 10−6s are predicted. To achieve this time resolution with only 21 views, both the spatial and contrast resolution are degraded when compared with medical CT systems. The system has multislice capability when used with film/screen detectors. The design, construction, and projected capabilities of the facility are detailed.

ISSN:0034-6748    

DOI:10.1063/1.1138877

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A general purpose high‐speed digital image processing system with bus‐oriented architecture has been developed using a time‐shared multiframe data bus with the data transferring rate of 80 Mbytes/s. This system is equipped with special purpose hardware for executing frame‐to‐frame operation, 2‐D convolution, and 2‐D recursive filtering, allowing image processing of dynamic scenes can be performed in real time. The architecture and hardware of the developed system are presented, and the manufacture of special purpose hardware is described. Experimental results have demonstrated the ability to accomplish image processing of moving objects in real time, and 2‐D convolution and 2‐D recursive filtering at high speed.

ISSN:0034-6748    

DOI:10.1063/1.1138878

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A conceptual basis for the technique of time delay photothermal wave spectroscopy is presented. The signal generation and appropriate system functions in the time delay and frequency domains are introduced and discussed from the point of view of correlation and spectral analysis and processing.

ISSN:0034-6748    

DOI:10.1063/1.1138879

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

FM time delay laser excitation has been implemented in a photothermal deflection spectrometric apparatus with fast rise‐time optics. The performance of the system was studied in both frequency and time delay domains. The spectrometer was further used in the study of thin quartz layers on an opaque substrate. In this work we have demonstrated the operation of the first frequency modulated (FM) time delay photothermal deflection (mirage effect) spectrometer with a ns rise time spectrally flat beam position detector unit. It was established by use of a blackbody reference that the spectrometer is responsive to impulsive heat sources in the sample with no measureable instrumental distortion of the frequency or time delay domain responses. The sensitivity of the device was tested successfully in the measurement of thermal parameters of thin quartz layers on absorbing backings. It was further shown that our spectrometer is sensitive to thin SiO2layers on Si wafers. The data were largely consistent with Green’s function models of heat conduction in the liquid interface and bulk. The ability of the spectrometer to perform high‐quality frequency response measurements via fast Fourier transformations of the input data in very short time compared to the conventional lock‐in detection is an extremely useful feature for thermal‐wave applications.

ISSN:0034-6748    

DOI:10.1063/1.1138880

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A detailed comparison is presented between the time delay and the pseudo‐random‐binary‐sequence (PRBS) methods of excitation and mirage effect response. Both time delay domain dynamic system response and frequency domain spectral functions were calculated via FFT methods. The results show that the FM time delay spectrometer exhibits superior performance to the PRBS device and is optimally suitable for nondestructive and depth‐profiling studies. The detailed examination of, and comparison between, the time delay and spectral dynamic functions of our FM time delay photothermal wave spectrometer and those of a PRBS‐driven device has proven that the former apparatus is capable of producing superior quality time delay and spectral function information when tested on a fast, flat frequency response mirage effect system. The FM time delay photoacoustic/photothermal wave technique and instrumentation of this work holds excellent promise for nondestructive evaluation and depth‐profiling applications in scientific research as well as industrial development laboratories.

ISSN:0034-6748    

DOI:10.1063/1.1138881

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An acoustic microscope setup has been applied to determine Rayleigh wave velocities in crystals from acoustic materials signatures. The Rayleigh wave velocity close to and above the phase transition in SrTiO3has been measured as a function of temperature. It has been shown that propane can be used as a coupling liquid between the acoustic lens and the sample enabling acoustic microscopy in the temperature region 85–220 K.

ISSN:0034-6748    

DOI:10.1063/1.1139207

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A double‐sided, high‐frequency response heat‐flux gauge has been developed which allows measurement of heat flux from dc to 100 kHz. The instrument is designed for heat‐flux magnitudes ranging from one to several hundred kW/m2at temperatures up to 400 °C and is independent of the test article material. The gauges consist of a metal film (1500 A˚) resistance thermometers sputtered on both sides of a thin (25 &mgr;m) polyimide sheet. The sheet, which can contain many gauges, is then adhesively bonded to a test article. The temperature difference across the polyimide is a direct measure of the heat flux at low frequencies, while a quasi‐1D analysis is used to infer the high‐frequency heat flux from the upper surface temperature history. The design criteria, construction and application techniques, and a novel, ratiometric calibration procedure are discussed in detail.

ISSN:0034-6748    

DOI:10.1063/1.1138882

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Two important improvements in a new technique for measuring and mapping local heat transfer coefficients are described. The first improvement involves the use of a new encapsulated thermochromic liquid crystal which has better stability and a narrower bandwidth than the cholesteric crystals previously used. The second important improvement is in the packaging arrangement. In this new arrangement, useful for gas flows, the liquid crystal is applied directly on the surface of an electrically conducting gold coating used as an electric heater, and is essentially in direct contact with the fluid. The encapsulated liquid crystal used in this study was applied directly to the gold surface without affecting the electrical characteristics of the gold coating. This new packaging arrangement has two advantages. First, no correction for the temperature drop across the plastic substrate is required. Second, a significant increase in the maximum detectable frequency is predicted.

ISSN:0034-6748    

DOI:10.1063/1.1138883

出版商:AIP    

年代:1986

数据来源: AIP