摘要:

An NMR spectrograph using an electromagnet is superstabilized by a feedback loop which uses the error signal from a secondary nuclear resonance probe to control the oscillator driving frequency. Field fluctuations thus produce such frequency variations as to preserve the Larmor condition for both short and very long times. The same oscillator is used for the measurement probe and thus also the Larmor condition is preserved in the sample being measured. Means are provided for sweeping frequency to produce precalibrated spectra of high precision at various magnifications and scale shifts with a very convenient and rapid setup procedure. Frequency scales are directly related to graph paper markings. Improved temperature control of the magnet and a reproducible precycling recipe also contribute to an unusually high degree of stability and reliability of day‐to‐day operation.

ISSN:0034-6748    

DOI:10.1063/1.1715873

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Single synthetic CdS crystals 3×4×10 mm, having dark conductivities from 10−9to 10−10ohm−1cm−1, were prepared for gamma‐ray detection. In a 50 r/hr Co60field the conductivity increased to 10−6ohm−1cm−1. The crystals were grown in a static system at 930±5°C. Indium electrodes were applied by an ultrasonic soldering technique. The effect of constant excitation from radium to reduce the crystal rise time is illustrated. The time response and spectrographic analysis of crystals and commercial CdS powders is presented.

ISSN:0034-6748    

DOI:10.1063/1.1715874

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An instrument has been developed to automatically find the level of mercury in a glass tube and indicate on a digital register the height of the mercury column. The first model has a range of 80 cm, a precision of better than ±0.05 mm and a maximum deviation of ±0.11 mm. The range and deviation depend upon the length and linear accuracy of the metric screw.

ISSN:0034-6748    

DOI:10.1063/1.1715875

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The balance point of a Wheatstone bridge with a slide wire for ratio arms is a nearly linear function of the temperature of a thermistor in a third arm, the maximum errors of a linear calibration are made equal and proportional to the cube of the temperature range, and the off‐balance sensitivity is nearly constant for a considerable temperature range. For a small thermistor with a 2000‐ohm resistance at 25°C, the slide position of a linear potentiometer is proportional to the thermistor temperature ±0.5°C, and the deflection of a taut suspension pointer galvanometer is 20±1 mm/°C over the temperature range from 0°C to 50°C with a maximum thermistor temperature rise of 0.05°C in still air.

ISSN:0034-6748    

DOI:10.1063/1.1715876

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A chloral hydrate‐agar gel has been used for depth‐dose measurements with x‐rays and electrons. HCl is formed from the chloral hydrate by the radiation and thus changespH and electrical conductivity of the gel. Radiation beams can be visualized by adding an acid‐base indicator. Quantitative measurements are made by spectrophotometry or by probing the gel with apH electrode or a conductivity electrode pair. Spatial resolution of perhaps 0.2 mm has been obtained with conductivity electrodes. Doses of 2000 rad or more are required to obtain satisfactory records, the lower limit being set by inhomogeneities in the unexposed gel.

ISSN:0034-6748    

DOI:10.1063/1.1715877

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The principle of transient temperatures inside a semi‐infinite solid is applied to two identical sets of composite plates. Each of these sets consists of a standard specimen of a certain metal whose properties are known and a test speciment of a metal whose thermal diffusivity is to be determined. When these two sets, initially at different but uniform temperatures, are brought into contact with each other, the transient temperature at the contact plane between the test and standard specimens corresponding to a certain time is measured, then the coefficient of thermal diffusivity of the test specimen can be computed. It takes about 30 seconds for the measurement and will yield a result with an estimated accuracy of about 3%.

ISSN:0034-6748    

DOI:10.1063/1.1715878

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A moving‐plate camera, suitable for investigating the angular and energy distributions of photoprotons, is described. Two nuclear plates, 1×3 in., are accurately held with the emulsion surfaces vertical, parallel and facing each other on a carriage, which moves forwards and backwards at constant speed below the target and parallel to the x‐ray beam in an evacuated tube. Targets are thin metal foils, 1.5×1 in. The angles and energies of tracks recorded in each plate coated with 200‐micron emulsion are 20 to 160 degrees and approximately 2 to 16 Mev. The theory of the camera is developed in detail.

ISSN:0034-6748    

DOI:10.1063/1.1715879

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A high temperature‐high pressure assembly has been designed to be used with a Straumanis‐type powder camera and a modified oscillatory attachment. The assembly consists of a small resistance furnace with a cooling shield and a specimen holder. The furnace is capable of heating the sample to a maximum temperature of 500°C and the temperature of the sample can be controlled to within ±1°C. The specimen holder, which is constructed from beryllium and Monel metal, has withstood hydrogen gas pressures above 600 psi at 500°C. The apparatus has been applied to the structural study of the system: uranium‐uranium hydride‐hydrogen gas. The lattice parameter of uranium hydride (&bgr;‐tungsten structure) is reported for the temperature range, 25°C to 500°C, with an accuracy of ±0.001 A.

ISSN:0034-6748    

DOI:10.1063/1.1715880

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A cell is described in which one can measure pressure coefficients of the dielectric constant and loss of liquids and solids to 10 000 psi. Data are reported for the liquids benzene, dioxane, and toluene to illustrate the use of the cell. Data are also reported for polyethylene‐5% butyl rubber to illustrate the use of the cell for the measurement of solids.

ISSN:0034-6748    

DOI:10.1063/1.1715881

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Small Teflon and Kel‐F bearings have been developed which operate in the temperature range below 80°K. They have been used to modify a commercially available induction motor for operation directly in a bath of liquid helium.

ISSN:0034-6748    

DOI:10.1063/1.1715882

出版商:AIP    

年代:1957

数据来源: AIP