摘要:

A procedure is described to determine the thickness of a plate material by infrared scanning. It consists of heating the material with a moving heat source and measuring the temperature of the plate by infrared scanning when the material has reached a quasisteady state. At that time, the initial temperature has been damped out, and the plate temperature becomes invariant with time in the moving coordinates of the heat source. The plate thickness can thus be determined independent of the initial temperature of the plate, and the infrared image can be analyzed more conveniently for an accurate determination of the plate thickness. This paper covers the analysis and experiment for infrared scanning. The uncertainty in the measurement is found to be within one gauge size of the plate thickness tested. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145593

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A large optical‐aperture membrane diamond anvil cell designed for infrared spectroscopy is described. The cell offers definite advantages compared to existing systems. Other possibilities concerning x‐ray diffraction analyses with the cells are mentioned. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145594

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In this paper, the performance of a novel high‐pressure diamond‐anvil powder x‐ray diffractometer in Guinier geometry is reported. The diffractometer is a combination of a curved quartz‐crystal monochromator, a Mao–Bell‐type diamond‐anvil cell, a flat position sensitive detector, and a Huber goniometer with compound stages to realize this geometry. The incident x‐ray beam is from a rotating anode x‐ray generator. It is shown that the above experimental arrangement results in an enhanced S/N ratio, improvement in resolution, and reduction of the data‐acquisition time. Test results on UAl2are presented to demonstrate the advantages of the setup in the study of phase transitions at high pressure. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145595

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A microflow apparatus has been built with a time resolution of 1 ms for mixing volumes of at least 80 &mgr;l per syringe. A time resolution of 3 ms is attained for mixing volumes of 10 &mgr;l per syringe. Equal volumes are mixed and concentration changes are observed photometrically using fiber optics for coupling light into and out of the observation tube having 1 mm diameter and 10 mm light path length. The reaction of ferrocytochromecwith ferrihexacyanide was used to calibrate the apparatus at 550 nm (10 nm half‐width). ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146502

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The development, construction, and evaluation of a simple ruby‐based fiber optic thermometer, for use over the region 200–300 K, are described. The results are compared with those obtained from a simple theoretical model, which may be used for system calibration, and with those of previously published work, and good agreement is seen. The application of such a sensor to the food processing industry and environmental monitoring is indicated. ©1995 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1145596

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have developed a new optical pyrometer with unique advantages for shock‐wave studies and for measurements of systems that are moving with respect to the detection system. Our pyrometer is fully fiber optic coupled. This completely eliminates any time‐dependent imaging or aperture effects common to imaging pyrometers, and is simple to align and calibrate. The sensitivity is also higher than typical imaging systems used for shock experiments. The design is excellent for observations of time‐varying phenomena. Detection is done with fast photomultiplier tubes with roughly 1 ns response. In addition, one may also include a streaked spectroscopic system, making this system ideal for fast spectroscopic studies. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145597

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Real‐time observation of the fluctuations in the temperature of a flowing gas may be obtained with a probe containing two geometrically similar thermocouples differing only in size, and an electronic analog circuit using commercially available integrated circuits. The thermocouple lag time constants may vary as gas flow rate varies, and need not be known. Only the thermocouple time‐constant ratio, a substantially invariant function of geometry, needs to be known. Under favorable circumstances, even this ratio need not be known in advance and can be determinedinsitu. The improvement in frequency response depends on the magnitude of the temperature fluctuation and is limited by the quality of the electronics. The system is useful when the thermocouple time constants vary appreciably during the course of the temperature fluctuations because of correlative fluctuations in gas flow rate. A thermocouple simulator is used to adjust the analog circuit and to test its efficacy. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145598

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have developed a technique for fabricating high resolution, ohmic contacts for cryogenic silicon detectors operated at temperatures well below 1 K. In this paper, we give a detailed description of the techniques used to fabricate these boron‐implanted contacts, and present characterization data obtained on 24 test samples studied during the design phase of our program. We then describe the fabrication and operation of a 23 g prototype silicon hybrid detector which simultaneously senses both the phonons and ionization produced by a single event, and which incorporates these new contacts into its design. Finally, we present data obtained using a radioactive source of241Am and this detector operated at 20 mK, and conclude that the contacts are fully sufficient for applications in particle astrophysics as well as in many other areas of physics. ©1995 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1145599

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Double relaxation oscillation superconducting quantum interference devices (SQUIDs) (DROSs) based on Nb/AlOxtunnel junctions have been fabricated and characterized. The estimated relaxation frequencies range from 400 MHz up to 14 GHz. Transfer coefficients from flux to voltage of 2 up to 7 mV/&fgr;0have been obtained. Both the intrinsic flux noise and the performance in a flux‐locked loop with direct‐voltage readout have been determined. Special attention is paid to the effect of damping resistors on the sensitivity of DROSs. The intrinsic sensitivity improves with increasing relaxation frequency, leveling off to a value of 13hat relaxation frequencies above 2–3 GHz for SQUID inductances of about 30 pH. This sensitivity is very close to the theoretical maximum sensitivity of 6hof a comparable standard type dc SQUID. In a flux‐locked loop based on direct‐voltage readout, a noise level of 0.55 &mgr;&fgr;0/&sqrt;Hz corresponding to an energy sensitivity of 34hhas been obtained for a DROS with a SQUID inductance of 29 pH. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145600

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We describe the design and performance of compact, low‐pass electrical filters, suitable for operation at cryogenic temperatures. The filters are two poleLCfilters with a cutoff at ≊100 kHz, an attenuation of −24 dB/octave, and a stop band rejection of −80 dB between 5 and 20 MHz. Their function is to suppress rf voltage noise to sensitive cryogenic detectors. The low‐pass filters are realized using surface mounted devices on thin PC boards which can be stacked for maximum packing density. Compact modules containing 14 and 35 filters have been developed and installed in the Infrared Telescope in Space. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145601

出版商:AIP    

年代:1995

数据来源: AIP