摘要:

A new technique for the measurement of electromagnetic power at millimeter wavelengths is described. A gas filled waveguide is used to measure the absorption of an electric dipole rotational line. From a study of the change in the absorption as a function of power, the degree of saturation of the gas is measured. The experimental results are then compared to a collision broadened absorption theory including linear waveguide losses to determine the input power required for the measured saturation. The technique can be used to measure powers as low as 10−6W.

ISSN:0034-6748    

DOI:10.1063/1.1720447

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A low temperature liquid helium level indicator which is capable of detecting the liquid helium level in an opaque Dewar in the temperature range of below 1°K to above 4.2°K is described. A high current electronic switch has been designed so that only one calibration of the instrument is necessary for the entire temperature range.

ISSN:0034-6748    

DOI:10.1063/1.1720448

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An improved double channel electronic sampling integrator with digital output is described which is particularly suitable for enhancing signal‐to‐noise in pulsed NMR studies in solids where narrow sampling gate widths and long data memory are essential. The sampling gate widths are 1 &mgr;sec or less. The difference signal between the channel inputs is converted to digital form and stored in a standard counter which may be modified to add successive counts, thereby computing the mean numerically. Since there is no analog integration the system has a pulse response time of 1 &mgr;sec. The system is free of ion or grid current drift problems common to previous designs. Thermal drift is small. Details of the circuits and graphs of integrating performance are presented.

ISSN:0034-6748    

DOI:10.1063/1.1720449

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An apparatus for determining theccrystallographic axis of transparent uniaxial crystals is described. This system utilizes the crossed polarizer technique for locating thecaxis. With this small portable device, irregularly shaped crystals, both large and small, may be oriented and polished to within 10′ in a relatively short time. This method is particularly useful for determining thecaxis of crystals for fluorescence and absorption studies and for orienting long cylindrical optical maser crystals.

ISSN:0034-6748    

DOI:10.1063/1.1720450

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A new method for the direct measurement of the convective heat loss from a human body working in a natural posture under different environmental conditions in a climatic chamber is described. The method is based on the integration of the increase in heat in the wake behind the body by the use of temperature integrating grids. A unique method of calibration takes account of the variation of velocity across the wake. An accuracy of better than 5% is expected with the method for normal test conditions.

ISSN:0034-6748    

DOI:10.1063/1.1720451

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A dual path ultrasonic flowmeter has been developed in which the measurement of fluid flow and the speed of sound can be made with the same meter without major interdependence. By placing two sound‐speed meters in opposition, sum, and difference frequencies can be extracted. The sum frequency is proportional to the speed of sound and the difference frequency to the velocity of the flowing medium. Small errors which arise from differential path lengths and time delays between the two measuring paths can be minimized by an iterative process of adjustment. Based on this technique, an instrument to measure flow in pipelines was developed and tested. The resulting flowmeter is considered to have an accuracy of 0.25%. By correction for changes in the speed of sound of the measured fluid, the accuracy can be increased to approximately 0.1%.

ISSN:0034-6748    

DOI:10.1063/1.1720452

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A continuous averaging technique for avoiding the effects of long period drift in x‐ray scattering measurements has been developed. Only minor changes in conventional diffractometer equipment are required. A high speed drive motor is substituted for the conventional one in the diffractometer, and the scattered intensities are stored on paper tape. Thus, the sum of many rapid scans is substituted for one slow scan and the effective drift time is reduced to a negligible value. The actual summation of scattering patterns in proper register is done with an electronic computer. The scattering patterns obtained in this manner are expected to provide better structural information than was previously available concerning amorphous substances. Comparison of conventional and continuous averaging scattering patterns with and without an artificially imposed drift demonstrates that the method is effective.

ISSN:0034-6748    

DOI:10.1063/1.1720453

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A scanning beam profile monitor is described that was developed for use along the Stanford 3 km linear accelerator. The maximum beam loss due to scattering caused by this monitor can be made to be a small fraction of that which would be caused by a Cˇerenkov radiator or scintillating screen.

ISSN:0034-6748    

DOI:10.1063/1.1720454

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A transistorized temperature regulator that is capable of controlling the temperature of a liquid helium bath to better than ±10 &mgr;°K for periods of 20 to 30 min is described. The circuit employs a carbon resistor as the temperature sensing element and achieves its temperature control by varying the current supplied to a 200 &OHgr; heater located in the liquid helium bath. Both a null meter and a heater current meter are incorporated in the design so that regulator performance can be continuously monitored.

ISSN:0034-6748    

DOI:10.1063/1.1720455

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A very important feature of present day semiconductor device technology is the measurement of the complex impedance or admittance characteristics of two‐terminal diodes or three‐terminal transistors. An electronic technique has been developed to automatically and continuously display the incremental conductance and capacitance of any two terminal nonlinear admittance as a function of applied dc bias over a frequency range 10 cps to 100 kc. The method employs phase sensitive detection to separate the in‐phase and quadrature components of the signal generated by a diode under test. Phase angle settings can be made to better than 0.1°. The system can measure over at least five orders of magnitude in admittance, and conductances as low as 0.001 &mgr;mho can be detected. The detection sensitivity of the apparatus is 0.0032 &mgr;V in a signal‐to‐noise ratio of 6.5×10−3. The performance of the system is described in terms of actual experimental data that have been obtained on various metal‐insulator‐semiconductor diodes.

ISSN:0034-6748    

DOI:10.1063/1.1720456

出版商:AIP    

年代:1966

数据来源: AIP