摘要:

Simple and convenient interferometer methods are described for determining the concentration of a substance in solution at various radial distances in an ultracentrifuge cell. These measurements are necessary for the usual molecular weight determinations by the ultracentrifuge method. The methods are particularly well adapted to equilibrium ultracentrifuge determinations of molecular weight and weight‐average molecular weights.

ISSN:0034-6748    

DOI:10.1063/1.1718287

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A symmetrical rf bridge for pulsed nuclear magnetic resonance experiments is described. The bridge is non‐microphonic and permits the quick damping of the transients from rf driving pulses without the degrading of free induction decay signals.

ISSN:0034-6748    

DOI:10.1063/1.1718288

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

An instrument is described which measures microsecond time intervals by counting pulses from a 100‐Mc CW oscillator; a commercially available scaler is employed as the major component. The over‐all differential non‐linearity of the instrument is ≤10−2. Data are stored in a magnetic core memory. The deadtime associated with measurement and storage has been minimized to permit use in experiments with pulsed accelerators.

ISSN:0034-6748    

DOI:10.1063/1.1718289

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A cryostat is described for use in absorption spectrophotometric measurements. With liquid nitrogen as coolant optical cells of variable path length can be maintained at any temperature from −194 to −40°C with a precision of ±0.1°. An optical cell assembly is also described which eliminates the problem of cracking of windows due to rapid temperature changes.

ISSN:0034-6748    

DOI:10.1063/1.1718290

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Many interference techniques have been employed for the thickness measurement of thin films. An interference technique which is inexpensive and easy to operate consists of a silvered lens placed over a stepped film with silver overlay. The resultant interference pattern when viewed in reflection is a series of sharp dark rings against a bright background, modified Newton's rings. The step in the film to be measured causes a shift in the rings from which the thickness is calculated. Step heights in silver films, vacuum deposited on fire‐polished microscope slides, of 160 and 780 Å were measured.

ISSN:0034-6748    

DOI:10.1063/1.1718291

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A spectrograph has been designed that simultaneously records broad‐range, charged‐particle spectra at twenty‐four different reaction angles, 7.5° apart, from 0 to 172.5°. At each angle, the spectrograph records a spectrum with a total energy range of about 2.3:1 and with a resolving power exceedingR=E/&Dgr;E=1000, where &Dgr;Eis the full width at half‐maximum of a peak. The recorders are seventy‐two 2×10 in. nuclear‐track plates, which are developed and scanned under a microscope after the exposures. When half‐millimeter strips across the nuclear‐track plates are scanned, the information contained on the nuclear‐track plates after one exposure corresponds to about 36 000 data points. A typical exposure time with about a 0.5‐&mgr;A beam is of the order of 2 to 3 h.

ISSN:0034-6748    

DOI:10.1063/1.1718292

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Methods of developing a photosensitive film to a high degree of uniformity are demonstrated to be dependent upon the effectiveness of the mixing of the developing solution and the disruption of the formation of a concentration boundary layer during the developing process. Adaptation of the hydraulic brush developing technique and use of film and microphotometer calibration procedures based on a primary standard of measurement made possible the extension of the useful range of commercial films for photometric purposes to a density of over 2.5. These methods permit the use of photographic photometry to make measurements of irradiance varying over a range of 100 to 1 with an accuracy of better than 10% over the entire range.

ISSN:0034-6748    

DOI:10.1063/1.1718293

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The design and mechanical details of a rotating‐vane radiant power control for use with a vertical, paraboloidal mirror, arc image furnace are given. Optical measurements show this design to give an attenuation of total radiant power at the image point which is approximately a linear function of vane angle, in the vane angle range 0 to 25°. In addition, the radiant flux profile is left essentially unchanged. The loss in maximum total power incurred by introduction of a specific design of the device, and an example of results obtained by its use in crystal growth experiments are also included.

ISSN:0034-6748    

DOI:10.1063/1.1718294

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A cryostat has been constructed and is described which permits the tensile deformation of metal specimens under loads up to 150 kg and simultaneous measurements of the thermal and electrical conductivity, thermal diffusivity, and heat of deformation, preferably at temperatures of liquid helium. The apparatus is designed to keep liquid helium for approximately 20 h, which permits the investigation of occurrences requiring high resolution in time, as for example the discontinuous slip at low temperatures. The measurement of the temperature and small temperature differences is achieved through the application of gas thermometers in connection with electronic differential pressure sensors of small dead volume. Automatic recording allows for an accurate observation of thermal transients. The thermal conductivity measurements are based on the Kohlrausch method. Some results which are representative for the application of the apparatus are presented.

ISSN:0034-6748    

DOI:10.1063/1.1718295

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Radiatively heated ovens have been used as vapor sources for vacuum deposition of superconductive films, primarily tin and lead. They delivered uniform deposition rates in the entire range tested from tenths of angstroms per second to ∼100 Å/sec. For the experimental arrangement employed, a deposition rate of 1 Å/sec is found by calculation to correspond to an effusion rate from the oven of 2×10−5moles/cm2/sec. By effectively reducing the length of the oven opening to zero and increasing the ratio of oven diameter to opening diameter to about four, emission characteristic of a surface source was obtained for the same range of deposition rates. For one such oven of typical dimensions, a chart is included by use of which compromise may be made between effective source enlargement, due to self‐scattering effects at the source, and deposition rate.

ISSN:0034-6748    

DOI:10.1063/1.1718296

出版商:AIP    

年代:1963

数据来源: AIP