摘要:

Time‐resolved measurements of the neutron flux from the Scylla IV–P linear theta‐pinch experiment have been made with scintillator‐photomultiplier combinations. Calibration of the detectors is accomplished by a comparison of their time‐integrated output with the total neutron yield measured using a foil‐activation technique for which an accurate calibration has been established. The temperature of the Maxwellian ion velocity distribution that would produce the observed flux is obtained from the Maxwellian reactivity <&sgr;v≳DDforD(d,n)He3and measurements of the temporal evolution of the plasma column density and dimensions. This determination of the time history of the ion temperature is in good agreement with the plasma energy measured using other techniques.

ISSN:0034-6748    

DOI:10.1063/1.1135974

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We have developed a fast‐scanning heterodyne receiver into a plasma diagnostic that measures the fundamental cyclotron emission from the PLT plasma and thus ascertains the time evolution of the electron temperature profile. The receiver scans 60–90 GHz every 10 ms and is interfaced to a computer for completely automated calibrated temperature measurements.

ISSN:0034-6748    

DOI:10.1063/1.1135975

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A hot wire has a limited life in high‐speed wind‐tunnel flows because it is typically subjected to large dynamic loads. As a consequence hot films and modified hot wires are frequently used for turbulence measurements in such flows. However, the fluctuation sensitivities of such probes are reduced because of various factors, leading to erroneous results. This paper described the results of tests on some sensors in both subsonic and supersonic boundary‐layer flows. A simple technique to determine dynamic calibration correction factors for the sensitivities is also presented.

ISSN:0034-6748    

DOI:10.1063/1.1135976

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

This paper describes the construction of an optically pumped laser device. The device utilizes a line‐tunable CO2TEA laser as a source to optically pump a cell which is capable of cooling candidate laser gases down to ∼150 °K. Laser outputs of 750 mJ in the 13‐&mgr;m region and 100 mJ in the 16‐&mgr;m region are obtained by pumping NH3and CF4respectively with 10 J of CO2laser radiation. The measured conversion efficiencies are 15% for NH3and 3% for CF4. These lasers can be used to photodissociate polyatomic molecules and are attractive sources for practical laser isotope separation.

ISSN:0034-6748    

DOI:10.1063/1.1135977

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Unprotected glass windows can be used at hydrostatic pressures up to at least 45 kbar on a 0.5‐mm‐diam aperture, and up to 40 kbar on a 0.8‐mm‐diam aperture.

ISSN:0034-6748    

DOI:10.1063/1.1135978

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The effect of piston rotation speed and fluid viscosity on the performance of free‐piston gauges with a controlled clearance was studied as part of an experimental program aiming at the better evaluation of pressure by these primary pressure standards. Calculated effective area is shown to be greatly influenced by both speed of rotation and choice of a fluid. An optimum rpm resulting in the smallest possible uncertainty in effective area should be determined experimentally for each fluid and pressure range involved. When all the pertinent parameters are properly selected an appreciable improvement in accuracy can be achieved.

ISSN:0034-6748    

DOI:10.1063/1.1135979

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

In pulsed optically detected magnetic resonance (ODMR) spectroscopy, a lock‐in amplifier is used to monitor the signal which is phase‐matched to the duty cycle of an applied sequence of pulses. However, since the desired signals reside atop a much larger amplitude‐modulated signal, lock‐in amplification methods are difficult to use. Commerically available photon counters are of limited use, because the pulsed ODMR method requires sequential counting over several time intervals, often with minimum time delay between the intervals. The multiaccumulator photon counter described here is capable of such sequential counting over as many as four intervals. The microprocessor which controls the counter algebraically manipulates the photon counts during each of the duty cycles. The result is an inexpensive yet versatile photon counter which is suited for pulsed ODMR and other applications in which sequential counting is necessary.

ISSN:0034-6748    

DOI:10.1063/1.1135980

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An array of vacuum photodiode detectors has been used to monitor discharge equilibrium, stability, and cleanliness in the Macrotor tokamak. These detectors use the photoelectric effect on small tungsten plates to measure UV emission in the band &lgr;∼200–1200 A˚, and so are sensitive mainly to impurity line radiation in Macrotor. The response of this system to controlled impurity contamination experiments and to disruptions is described. The design, construction, and background problems associated with these detectors are discussed in detail.

ISSN:0034-6748    

DOI:10.1063/1.1135981

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A circuit has been developed to display the temperatures measured using platinum resistance thermometers. The thermometer number and the temperature are displayed sequentially together with the highest temperature and the number of the corresponding thermometer.

ISSN:0034-6748    

DOI:10.1063/1.1135982

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

This paper describes the design, construction, and characterization of a variable‐temperature wafer apparatus for use in the detection of electrically active defects which produce deep levels in the band gap of silicon. In its present form, the wafer chuck can heat and cool wafers as large as 51 mm in diameter over the temperature range from −196° to 350°C. Heating rates as high as 7°C/s have been achieved. Sensitivity for electrical measurements is sufficient to allow current measurements as low as 0.2 pA or capacitance changes (1 MHz) as small as 5 fF. The use of this apparatus is illustrated by wafer mapping the gold defect density in diodes fabricated across a silicon wafer.

ISSN:0034-6748    

DOI:10.1063/1.1135983

出版商:AIP    

年代:1979

数据来源: AIP