摘要:

Two spherical drag probes which use variable inductance devices as displacement transducers were built to measure turbulent water velocity fluctuations. The associated circuitry provides voltage outputs which are proportional to the three components of force acting on the spherical sensor of each probe. The probes respond to the fluid drag force and also to the fluid inertial force in an accelerating flow field. The frequency at which the response is 3 dB down is 18 Hz for one probe and 41 Hz for the other. The instruments have been calibrated for oscillating flows with velocities from 10 to 150 cm/sec.

ISSN:0034-6748    

DOI:10.1063/1.1684687

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A program controlled, inductively heated, compact high temperature dilatometer was designed and built. The dilatometer is capable of measuring the thermal expansion of arc‐melted hemispherical metal samples as small as 1.5 mm high by 3.2 mm diam up to 1600°C. The design of the instrument incorporates a linear variable differential transformer (LVDT) transducer with a sensitivity of 1.02×10−3mm/mV.

ISSN:0034-6748    

DOI:10.1063/1.1684688

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The construction and operating characteristics of a pressurized laser‐triggered spark gap capable of switching voltages exceeding 10 kV with a risetime of less than 300 psec are described. Other desirable features are its low delay and jitter times (∼1 nsec), the ability to deliver rectangular pulses with less than 10% ripple during and after the pulse, and its simplicity of construction. The gap has been investigated using the output of either a single mode ruby laser or a mode‐locked neodymium‐glass laser as a trigger.

ISSN:0034-6748    

DOI:10.1063/1.1684689

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A system simplifying Hall effect measurements is described. With this system the operator effort is reduced from the usual time consuming sequence of control and measurement steps to simply recording the data values. A single digital voltmeter is used to display all the values of currents and voltages required for these measurements and also the temperature of the Hall sample. The proper sequence of measurements, including magnetic field control, is achieved by using a programming switch driven by a stepping motor energized by timers. An original design of a constant current source is included. The output from the digital voltmeter could be connected to a digital punch or automatic data acquisition system providing full automation of measurements.

ISSN:0034-6748    

DOI:10.1063/1.1684690

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A mechanism is described for changing the signal detector in the Cambridge ``Stereoscan'' scanning electron microscope without breaking the vacuum. This has three main advantages. First, it makes it easier to compare the back scattered electron image, the secondary electron image, and the luminescent image, which can help the interpretation in some cases. Second, a spare secondary electron detector can be kept in reserve for high resolution work, thus avoiding the degradation of scintillator performance that occurs after prolonged use. Finally, it makes it possible to optimize detectors by comparing different versions of the same basic design.

ISSN:0034-6748    

DOI:10.1063/1.1684691

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A simple approach for improving the resolution in electron paramagnetic resonance absorption measurements by use of a third derivative technique is presented. The advantages in the case of broad absorption signals as well as of barely resolved lines are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1684692

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A simulant with a suitable surface and the correct thermal inertia, &bgr;=k&rgr;c, meets the primary requirement of accepting heat at the same rate as the skin. For protected skin, a simulant with a blackened opaque surface, &bgr;½=0.035 cal·cm−2·sec−½·°C−1, and equivalent depthx/2√&agr;=0.12sec12(&agr;=k/&rgr;c)is suitable. Such simulants have been made of fused silica and of an epoxy resin filled with aluminum powder. The detector was a butt welded copper‐constantan thermocouple, flattened to a thickness of 0.0015 cm, or a thermocouple of evaporated gold and bismuth films, ∼6000 Å thick. Results with water flow simulating blood flow in the skin indicate that an inert system simulates the response of skin rather well; if some adjustment must be made for varying blood flow it can be done experimentally or by calculation.

ISSN:0034-6748    

DOI:10.1063/1.1684693

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

This paper analyzes and describes a K‐band saturation effect spectrometer designed for the detection of resonance absorption in gas phase microwave spectroscopy. As a means of obtaining molecular information, this spectrometer exploits the nonlinear response of a balanced bridge to the amplitude modulation of a saturating microwave field. To enhance saturation the sample cell terminating the signal arm of the bridge is in the form of a high‐Q cavity consisting of a half‐symmetric confocal resonator excited in the fundamental TEM00q(q≃50) mode. Microwave detection is accomplished with a sensitive superheterodyne technique using phase coherent 30 MHz intermediate frequency (i.f.) conversion. By combining the double feature of in‐phase and quadrature‐phase i.f. demodulation, this system provides means for a fully automatic bridge balance giving rise to a detected molecular signal which depends on absorption only. The theory implied in the interpretation of this signal as a function of the unsaturated absorption coefficient of the gas is worked out and the techniques relevant to the construction and operation of the instrument are presented in detail. New and potentially useful methods of using the spectrometer for the precise determination of linewidth and absolute intensity of spectral lines are outlined. The capabilities of the methods have been tested on selected lines of the molecules OCS, C2H4O, and CH3OH and the resulting data have shown that a measurement accuracy on the order of a few percent can be achieved for both linewidth and intensity.

ISSN:0034-6748    

DOI:10.1063/1.1684694

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

An apparatus for photofragment spectroscopy, a new type of molecular spectroscopy for dissociative electronic states, is described. Inside an ultrahigh vacuum system, a molecular beam is crossed by pulses of polarized light (from a theta‐pinch discharge or from various lasers, including ruby, second harmonic ruby, second harmonic neodymium‐glass, and laser pumped tunable dye) and the recoiling photodissociation fragments are detected by a quadrupole mass spectrometer a few centimeters away. The data are collected and analyzed by an on‐line time shared computer and presented on a computer driven oscilloscope display as plots of number of fragments detected per microsecond vs time after the laser pulse. Parameters such as photon energy, photon flux, fragment mass, and fragment laboratory recoil angle with respect to the electric vector of the light can be varied to obtain a multidimensional spectrum. This spectrum, the probability of photodissociation as a function of photon energy and flux and of fragment mass, center‐of‐mass translational energy, and center‐of‐mass angle of recoil, may be used to study many aspects of molecular states.

ISSN:0034-6748    

DOI:10.1063/1.1684695

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Plane Chapman‐Jouguet detonations in equimolar acetylene‐oxygen mixtures are used to calibrate piezoelectric pressure probes of high spatial and temporal resolution in the range of 1–30 atm. The output voltage of the gauges is found to be proportional to the pressure,V=&agr;P, where &agr; is a calibration constant particular to each probe.

ISSN:0034-6748    

DOI:10.1063/1.1684696

出版商:AIP    

年代:1970

数据来源: AIP