摘要:

A doubly balanced optical quadrature mixer is proposed for use in light‐beating spectroscopy. The technique allows one to examine asymmetric optical spectra. The ratio of the antisymmetric to symmetric spectral densities can be found directly. The use of the device in the photon‐counting regime is also discussed. The instrument has direct applicability in the measurement of the dynamical properties of hydrodynamic systems out of equilibrium.

ISSN:0034-6748    

DOI:10.1063/1.1139326

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The design and operation of a differential absorption lidar (LIght Detection And Ranging) system capable of remotely measuring the vertical structure of tropospheric pressure and temperature are described. The measurements are based on the absorption by atmospheric oxygen of the spectrally narrowband output of two pulsed alexandrite lasers. Detailed laser output spectral characteristics, which are critical to successful lidar measurements, are presented. Spectral linewidths of 0.026 and 0.018 cm−1for the lasers were measured with over 99.99% of the energy contained in three longitudinal modes.

ISSN:0034-6748    

DOI:10.1063/1.1139327

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A theoretical discussion is presented of the design features that have been incorporated into a multipass cell appropriate for use in laser molecular‐beam experiments. A detailed description of the cell in two dimensions is given, and this is later expanded to highlight the problems of alignment in three dimensions. A prototype cell, constructed using the guidelines presented here, has demonstrated that 31 passes through a molecular beam can be easily achieved. Computer simulations suggest that the optimum potential of the cell is ≊101 passes. The fact that the position of the emergent laser beam is clearly defined makes the cell particularly useful for the purposes of studying absorption spectra.

ISSN:0034-6748    

DOI:10.1063/1.1139328

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A technique is described for measuring transient real and imaginary conductivity histories in a single pulse using the microwave cavity perturbation technique when the perturbations are large, that is, when the frequency shift is larger than the FWHM of the cavity resonance and/or when the cavityQchanges significantly. A demonstration of the use of the technique to measure laser photoionization yields in a high‐pressure buffer gas is presented.

ISSN:0034-6748    

DOI:10.1063/1.1139329

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Quadrupole mass analyzers (QMA) are the most common type of instruments for the measurement of partial pressures of residual gases in semiconductor industry. The maximum range of this instrument available today is 1–1000 amu, which is equivalent to charge‐to‐mass ratios (Q/m) of 108–105C/kg. Here, we report in detail the design, construction, and testing of a QMA capable of measuring (Q/m) ratios down to 5 C/kg. This instrument has been used to measure theQ/mdistribution of ions, clusters, and microdroplets emitted from a needle‐tip type liquid metal ion source (LMIS). TheQ/mdistribution of clusters and microdroplets has been found to form a broad peak, and is concentrated mainly between 105and 103C/kg. The variation of this distribution as a function of total beam current and beam emission angle has been studied.

ISSN:0034-6748    

DOI:10.1063/1.1139330

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The NMR stabilizer has been constructed for the purpose of magnetic field stabilization. The error signal for field correction is derived from the1H resonance of pure H2O. A NMR transducer, operating in the pulse mode with time multiplexing, is connected to the transmit–receive radio frequency stage and yields information about the magnetic induction changes in the frequency form which is compared with the reference frequency. The frequency deviation is evaluated as a voltage that controls the power supply of the electromagnet coil. The stability achieved was slightly better than ±1 ppm.

ISSN:0034-6748    

DOI:10.1063/1.1139331

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We discuss the asymmetric double Langmuir probe (ADLP) and demonstrate the possibility of using it to measure plasma temperatureTeand densitynwhen it is operated in the region of small signal response. The area of one of the ADLP collectors is considerably larger than the other. This probe can be operated at a relatively low applied voltageeVa/Te<1, and still provides sufficient information to determine the plasmaTeandn. There is no need for a direct measurement of the ion saturation current, which can be on the order of a few amperes in large fusion devices. This reduces the requirements on the probe power supply.

ISSN:0034-6748    

DOI:10.1063/1.1139332

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A new technique using a silicon surface barrier (SSB) diode has been developed for measuring the escaping fast ion flux from a tokamak plasma. Calibration of the detector with an ion beam showed that at a fixed energy the diode’s output current varied linearly with the incident deuteron flux. The diode was mounted inside the PDX vacuum vessel with collimating apertures designed to admit the spiraling orbits of 50‐keV deuterons expelled from the plasma by MHD instabilities. Results from PDX indicated that relative measurements of the escaping fast ion flux due to several plasma instabilities could be made.

ISSN:0034-6748    

DOI:10.1063/1.1139333

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A new method has been described elsewhere for measuring transient temperature changes using the absorption of the 254‐nm resonance radiation from an optically thick Hg lamp by traces of Hg vapor. The method is based upon the fact that the Hg resonance lines broaden in a known way with increasing temperature and pressure. The sensitivity and dynamic range of the temperature measurement depends upon the extent of line reversal which varies with the optical depth of the Hg lamp. It is shown here that this can be controlled by means of a proper lamp design. The mounting assembly for the lamp and the circuitry required for this purpose are described. It was demonstrated that the output of such a lamp is stable and reproducible with line profiles (optical densities) that could be varied over about a 20‐fold range. Within such a range of operating parameters, the measurement of transient temperature to 1500 K in gases at pressures below 100 Torr could be made.

ISSN:0034-6748    

DOI:10.1063/1.1139334

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have compared the low‐frequency capacitance of glass thermometers of various shapes, made of very pure SiO2doped with ≊1200 ppm OH−, in the temperature range of 4–100 mK in a magnetic field of 9 T. The construction of the electrodes, the way the contacts are made, and the connection of the leads or cables influence both the voltage and the field dependence of the capacitance and of the loss. We have been able to construct capacitive glass thermometers of which the capacitance is not shifted in a field of 9 T at temperatures down to 4 mK, within our temperature accuracy of ≊5%. This has been determined by comparison with a cerium magnesium nitrate (CMN) thermometer in a field‐free region, and by comparing ultrasound measurements versus the thermometer capacitance with and without a magnetic field.

ISSN:0034-6748    

DOI:10.1063/1.1139335

出版商:AIP    

年代:1987

数据来源: AIP