摘要:

A description is given of a modified Michelson interferometer that is particularly useful for locally probing highly transient plasmas such as occur behind incident shock waves in high performance shock tubes. The interferometer has the following features: (a) It is of a modified Michelson form with spherical mirrors to minimize effects of spatial variations in the index of refraction normal to the beam, (b) the light source is a cw laser that provides a very narrow coherent beam to allow high spatial and temporal resolution of the probe, and (c) it is operated in a single fringe mode over the narrow beam (constant phase difference between the two interfering beams over the illuminated field) and fringe shifts are observed through the time response of single channel detectors. Because photon transit time is negligible in shock tube diagnostics, the response time of the interferometer is determined solely by detection capabilities. Rapid response is achieved because nearly the entire laser energy is available for detection and high contrast interference takes place, allowing high signal‐to‐noise ratios at wide bandwidths. The spatial resolution can be diffraction limited. Thus, one‐dimensional observations can be made of temporally and spatially varying events with a combined temporal and spatial resolution exceeding that available with other current interferometric techniques. Index of refraction profiles behind strong shock waves have been observed at two wavelengths simultaneously and verify the usefulness of the design. A further design modification is discussed which removes the uncertainty in the sign of the temporal gradient of index of refraction and would allow accurate fractional fringe interferometry.

ISSN:0034-6748    

DOI:10.1063/1.1684506

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The apparatus for the adiabatic fast passage experiments used for the measurement of NMR spin‐lattice relaxation times is described. The different experimental conditions and techniques for theT1measurements of chemically shifted nuclei are briefly discussed.

ISSN:0034-6748    

DOI:10.1063/1.1684507

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A detailed comparison between an argon ion laser system utilizing the hollow cathode discharge (HCD) and one employing a conventional, externally heated oxide cathode, but with identical geometry, has established that there are no significant differences in their microscopic behavior, and that the excitational processes occurring in the two systems are the same. A comparison of the over‐all efficiency of the two systems operating at the same output power level shows that when bariated tungsten cathode cylinders are used in the HCD, this device does not require greater input electrical power than the conventional device. It is further shown that operation of the HCD laser does not require a continuously flowing gas system as has previously been reported. This study shows the HCD to be an attractive alternative to conventional discharge geometries for ion laser systems.

ISSN:0034-6748    

DOI:10.1063/1.1684508

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A high precision potentiometer has been constructed to determine the ratio of two voltages presented by the University of Manitoba second order mass spectrometer. The ratio can be determined to a precision of 0.4/&Dgr;Vppm, where &Dgr;Vis the smaller of the two voltages. &Dgr;Vis variable from a few millivolts to several volts. For &Dgr;V>4 V the precision remains near 0.1 ppm.

ISSN:0034-6748    

DOI:10.1063/1.1684509

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A simple and compact laser Doppler radar system capable of high resolution velocity measurements of a slowly moving surface is described. The system is nondestructive and does not contact or interfere with the object whose speed is to be measured. All required beam splitting and reflective surfaces are integrated in a solid crystal block, greatly simplifying alignment. Experiments are performed using a rotating scattering wheel in which velocities as low as 0.21±0.02 mm/sec have been measured.

ISSN:0034-6748    

DOI:10.1063/1.1684510

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A unique stroboscopic pulse radiolysis system is described which detects the transient light‐absorbing species formed in solutions by individual fine structure pulses from a 40 MeV linear accelerator. A measured time resolution of 23 psec is attained by using, as the analyzing light, the short (<10 psec) Cˇerenkov light flashes produced in air by the fine structure pulses of the electron beam. This light is suitably delayed by an optical system in which the path length is slowly changed, then passed through the irradiated sample. The integrated light passing through the sample id detected, and variations in the optical absorption at varying times after the irradiation pulse are observed. The design and performance of the optical, mechanical, and electronic devices which retrieve the absorption signal out of the noise are described in some detail. As an integrated unit, this system meets its expected performance capability, being able to successfully detect absorption signals as small as 0.2%.

ISSN:0034-6748    

DOI:10.1063/1.1684511

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A balloon borne apparatus has been designed to analyze atmospheric minor constituents: CO2, H2O, CH4. The sampling system, consisting of a compressor, delivers samples up to 35 km. Cyclic analyses are performed by gas chromatography. Concentrations as low as 1 ppm may be detected in air samples.

ISSN:0034-6748    

DOI:10.1063/1.1684512

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A flexible, inexpensive thermostat for the temperature range 100 to 400 K is described. Liquid nitrogen is the coolant and a gas serves as transfer medium. The temperature can be set to better than 1 K and is held there within ½ K by an electronic control system. The relatively small working volume of the order of 10 cm3allows quick changes of temperature, a desirable feature in typical semiconductor experiments.

ISSN:0034-6748    

DOI:10.1063/1.1684513

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Vertical temperature gradients in a helium I bath have been measured with a movable probe, using a carbon resistor as the sensor. The bath temperature was controlled so that the temperature at the bottom of the bath was fixed. The measured temperature gradients were in substantial agreement with those predicted from the change of the vapor pressure of the bath with height.

ISSN:0034-6748    

DOI:10.1063/1.1684514

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The article gives a general treatment of the electron optical properties of cylindrical electron spectrographs. The resolution, the transmission, and the ratio of them (figure of merit) for electrostatic spectrographs are computed and compared for various choices of focusing arrangement and location of the source and the image. The second order focusing, which occurs in the evaluation as an asymptotic case of the first order focusing arrangement, is shown to yield a figure of merit which is in most cases superior to first order focusing. Locating the source and the image at the cylinder axis is also found to be the optimal setup using this figure of merit as a criterion.

ISSN:0034-6748    

DOI:10.1063/1.1684515

出版商:AIP    

年代:1970

数据来源: AIP