摘要:

The concept of Mo¨ssbauer spectroscopy on time dependent systems is explored. Several Mo¨ssbauer spectra are simultaneously generated, each with a different time relation to a pulsed perturbation. Obtainable resolving times span the range of hours to nanoseconds.

ISSN:0034-6748    

DOI:10.1063/1.1685983

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

We describe a feedback stabilization circuit useful for measuring optical reflectivity (or absorptivity) derivatives. The circuit is designed to suppress signal amplitude variations from the measured &Dgr;R/Rwithout involving the light source, spectrometer, or detector in the feedback stabilization loop. The use of this circuit for normal incidence reflectance measurements is also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1685984

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Vacuum wafer chucks are useless for electron beam microfabrication. An analysis of the required electrostatic forces and frequency response of a specimen wafer on a field plate is made. An experimental electrostatic chuck and its high voltage square wave power supply have been fabricated. Full clamping action has been provided by electrostatic pressures of 1/6 atm, and 1 atm pressures are feasible. In‐vacuum operation is excellent down to supply frequencies of 0.01Hz.

ISSN:0034-6748    

DOI:10.1063/1.1685985

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

We present measurements of window energy loss and pulse height defect in a silicon surface barrier detector for nuclei of hydrogen, helium, nitrogen, neon, and argon at incident energies of ≲ 15 to ≳ 200 keV. The values ofdE/dxin the gold window were low by [inverted lazy s] 20% for neon and [inverted lazy s] 40% for argon, and high by [inverted lazy s] 30% for nitrogen and [inverted lazy s] 50% for helium, compared to previously calculated energy loss curves extrapolated to these low energies. The pulse height defect energy losses were within [inverted lazy s] 10% for neon, low by [inverted lazy s] 15% for argon and low by [inverted lazy s] 30% for nitrogen compared to theoretical calculations.

ISSN:0034-6748    

DOI:10.1063/1.1685986

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A practical preamplifier modification is described which replaces the vacuum tube amplifier by a low noise cascoded dual field effect transistor. An improvement of 10 in signal‐to‐noise ratio has been effected using the Varian 4333 probe. These modifications are of potential application to NMR spectrometers other than the HA series.

ISSN:0034-6748    

DOI:10.1063/1.1685987

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The helium‐neon laser is utilized in many applications today by scientists and engineers. These applications frequently require a visible amplitude‐stable optical source. Helium‐neon lasers have been shown to have amplitude fluctuations of typically ± 1%. Amplitude stabilization techniques have been previously concerned with mechanical improvements, discharge current regulation, and variable loss modulation. The Zeeman effect of a magnetic field will be shown to control the output power of a helium‐neon laser. A servo feedback system was constructed to demonstrate the ability to stabilize the visible power by reducing power fluctuations from ± 1.0% to ± 0.05%. The Zeeman effect stabilizer overcomes the necessary insertion loss of the current regulation stabilizer. It is also independent of the negative impedance high voltage discharge system.

ISSN:0034-6748    

DOI:10.1063/1.1685988

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A high‐temperature calorimetric probe was shown to be a reliable method of measuring temperatures in argon and helium plasma jets in the range 2000 to 10 000 K. A number of simple corrections were found to be necessary to account for the heat transfer interactions between the calorimeter, its insulating jacket, and its water‐cooled support, as well as for the flow of heat to the nose section of the calorimeter. At the high temperature level (12 000 K), the probe measurements agreed with the spectroscopic data reported in the literature, while the values in the lower temperature range were confirmed by thermocouple measurements. The probe could also be used to measure gas composition and gas velocity, and results of typical applications are given.

ISSN:0034-6748    

DOI:10.1063/1.1685989

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The kinetic theory of a drifting Maxwellian gas has been applied to the gas sampling problem in atmospheric density measurements aboard satellites and high velocity probes; and a molecular beam mass spectrometer has been developed for gas density measurements in the upper atmosphere which substantially eliminates gas‐surface scattering and gas‐surface reactions in the sample, and preserves the integrity of the gas sample during the analysis process. An ion source lens system has been developed and experimentally evaluated over the pressure range 10−7−10−4Torr. The extracted ion beam was analyzed for energy distribution and angular distribution. For ion energy sufficiently high that the thermal energy of the gas can be neglected, the ion energy spread is less than 4 eV on‐axis and 90% of the ions are within 2.5° of the beam axis. It is concluded that the application of this technique to atmospheric composition studies will substantially improve our knowledge of the upper atmosphere of the earth and other planets.

ISSN:0034-6748    

DOI:10.1063/1.1685990

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A technique is described for using a fast scintillator and high speed streak camera in conjunction with a magnetic spectrograph to measure the time dependence of the momentum to charge ratio of particles. Time resolution, limited by the scintillator decay time, was 1.7 nsec. Momentum to charge ratios of positive ions and of electrons were measured in an intense relativistic electron beam.

ISSN:0034-6748    

DOI:10.1063/1.1685991

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A new method for investigating microchannel plate quality is described. The microchannel plate is operated with an applied voltage, either with normal or reverse polarization. Without any polarization, the scanning electron microscope takes a picture only of the external flat face. With a reverse voltage, the secondary electrons may be collected from the full depth of the channel and give a clear and bright picture of the internal surface of the channel. With normal polarization, the secondary electrons are multiplied through the plate and give the image of the electron gain of each individual channel. This use of the SEM is therefore very helpful for studying the quality of the microchannel array.

ISSN:0034-6748    

DOI:10.1063/1.1685992

出版商:AIP    

年代:1973

数据来源: AIP