摘要:

An analog circuit is presented for the detection in real time of the turbulent‐nonturbulent interface at the free stream edge of turbulent shear flows. The output of the circuit is a square wave whose value is unity when the detector probe is in turbulent flow, and is zero when in nonturbulent flow. The effectiveness of several detection schemes is evaluated. A method for calibrating the detector circuit is given by using a ``synthetic,'' intermittently turbulent simulated signal of known intermittency properties. A circuit for generating the simulated signal is also presented.

ISSN:0034-6748    

DOI:10.1063/1.1686827

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The operating characteristics of field ionizing tungsten tips used as detectors of low temperature beams of3He and4He are presented. These include typical I‐V characteristics, effective detection area, conditions for fast ionization time, and details necessary for reliable detector performance. In addition, we report that, under our operating conditions the detection efficiency was independent of the incident atom velocity. This is in contradiction to predictions from current field ionization theory.

ISSN:0034-6748    

DOI:10.1063/1.1686828

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The construction of a microminiature axial magnetic field probe, and its associated instrumentation, is described. With an active area measuring approximately 100×100 &mgr;, and an over‐all cross‐sectional dimension of 1.2 mm diam, the probe is sufficiently small to be maneuvered about within the polepiece of a conventional electron microscope objective lens. The axial component of the magnetic field can be measured on, as well as off, the axis of the polepiece to a higher spatial resolution than can be achieved with a commercial axial probe.

ISSN:0034-6748    

DOI:10.1063/1.1686829

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An intracavity dye laser technique has been used to study the photodetachment of electrons from gaseous OH−ions in an ion cyclotron resonance (icr) spectrometer. Enhancement of the photodetachment effect by a factor of 6.8 when comparing the intracavity technique to a double‐pass experiment has been observed. Under the conditions of these experiments approximately 93% of the OH−ions in the icr cell undergo photodetachment using the intracavity technique.

ISSN:0034-6748    

DOI:10.1063/1.1686830

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The emergent stem correction for liquid‐in‐glass thermometers can be avoided by heating the capillary of the thermometer with a heat pipe to the temperature of the bath. Experiments show that full compensation of the error can be achieved by proper thermometer design.

ISSN:0034-6748    

DOI:10.1063/1.1686831

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A coupling scheme and a probe damper for use with a pulsed nuclear magnetic resonance single coil probe are described. The designs for both circuits incorporate the unique properties of PIN diodes. The performances of the circuits at the signal processing level are evaluated at 4.3, 15.78, and 49.0 MHz.

ISSN:0034-6748    

DOI:10.1063/1.1686832

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A device is described which permits accurate measurements of the heat flow through a horizontal fluid layer. The heat sensor provides for a uniform cooling of the fluid layer and prevents heat losses to ambient air or other parts of the apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1686833

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A clarification of the mechanism responsible for reported high electron emissivities of barium zirconate cathodes in the presence of electronegative gases is made. A suggestion for simplifying the preparation of such cathodes is given.

ISSN:0034-6748    

DOI:10.1063/1.1686834

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A simple electronic analog divider is described for plotting the transmittance or reflectance characteristics of optical materials as a function of wavelength. It is designed with commercially available integrated circuits and it automatically takes the ratio of any two signals connected to its inputs. The output is recorded as the spectrum is scanned by a monochromator.

ISSN:0034-6748    

DOI:10.1063/1.1686835

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A gridded electrostatic electron energy analyzer is described which has been used successfully to time resolve trapped electron distributions at 200 MHz in a beam plasma device. Examples of raw data and extracted phase space plots are presented.

ISSN:0034-6748    

DOI:10.1063/1.1686836

出版商:AIP    

年代:1974

数据来源: AIP