Exposure Step Research Articles

Temperature Dependence of Hydrolysis of Polyimide Wire Insulation

Degradation of polymeric materials as a chemical reaction rate, related to exposure temperature, has been confirmed by many laboratory studies, and the rate equation, enhanced by other stresses and environmental conditions, has been utilized to compare the service life expectancy of various electrical insulation materials and systems for many years. In recent Naval aircraft wiring applications it has been experienced that a popular polyimide insulation undergoes degradation by a hydrolytic chain-splitting reaction that can be attributed to an unexpected number of service failures. In this initial study it has been determined that the reaction does proceed in a neutral pH aqueous environment at a rate that is temperature dependent, and the data of life versus temperature conforms to an Arrhenius plot so that from accelerated tests at elevated temperatures it is possible to extrapolate to service temperatures. Continuing studies will lead to the development of a functional aging procedure for applying a moisture exposure step into each cycle in order to more nearly predict service life of this insulation system and provide a comparison with other candidate systems.

Photomasking Film Using Phthalocyanine Electrophotographic Layer

AbstractPhotoconductive copper-phthalocyanine is dispersed in a negative-working-type photopolymer and coated on an ITO transparent layer or the conductive layer including SnO, and negative-type photopolymer. The film-making process consists of corona charging, image exposure, liquid toner development, uniform UV exposure and trichloroethylene development steps. A film can be charged positively to 340 V and the incident energy required to discharge the photoreceptor to one-half its maximum surface potential is 650erg/cm2. The toner image formed on the photoconductive layer can be served as a good optical mask for the UV exposure to photopolymer as binder resin. The photoconductive layer under the toner layer can be dissolved away by an organic solution, and the other area exposed to UV light is left on the transparent sheet. This negative-type electrophotographic film can be used for the optical mask to a negative-working-type presensitized printing plate.

Resolution and noise in xeromammography.

The resolution and noise characteristics of the xeromammographic image are analyzed by means of a multistage model which considers the exposure, toner deposition, and toner transfer steps. A frequency-dependent theory of xeromammographic noise is developed and comparison is made with experimental results. Central to this theory is the concept of a toner electrode formed in the immediate vicinity of the Se layer. Comparison is also made between the imaging capabilities of xeromammography and screen/film systems. The paper concludes by addressing the question of normalization of the transfer function in an electrostatic system.

A Man-Machine Communication System for Boiling Water Reactor Core Management Planning

A man-machine communication system has been developed for boiling water reactor (BWR) core management planning to provide a very flexible tool, which is complementary to automated optimization programs that maximize or minimize one particular performance index under certain constraints. A three-dimensional BWR simulator, which can cover a wide range of BWR operating conditions, has been developed and coupled with a graphic display serving as a main input-output controlling device. The system has been successfully applied to generate a long-term control rod programming of a BWR in which locally poisoned fuel assemblies are loaded. The time required for one cycle analysis is approximately 3 h, out of which the actual computation time is only 4 min with an average of three trials of rod pattern search per exposure step. The quick response (5 sec) and the visualized results on the screen are very helpful in understanding the complicated characteristics of the BWR core, and it is found that this kind of tool has a very great educational effect. A similar approach is expected to be applied in other fields such as core design and safety analysis, as well as in core management.

The Herschel Effect and the Structure and Stability of the Photographic Latent Image*

In a previous investigation carried out with a contrast motion-picture positive emulsion of uniform grain size, it was found that for the first few minutes of development in a standard Elon-hydroquinone developer the differential density decrease produced by the Herschel effect was constant in each exposure step of the pre-exposure to white light. This led to the conclusion that the “critical size” of the development centers remained essentially unchanged during that time.In the present investigation with the same emulsion, the constancy of the Herschel effect was confirmed, both with the same developer and with a pure surface ferrous oxalate developer. When development baths were used which contained varying amounts of sodium thiosulfate, the Herschel effect decreased, corresponding to the solvent action. This agrees with the widely accepted view that the Herschel effect produces a redistribution of centers through the grain.The Herschel effect proved also to be a sensitive indicator of the growth of surface centers which occurred when white-light and infra-red exposures were separated by longer time intervals. When the film was kept at higher temperatures, the decrease of the Herschel effect was the only evidence of latent-image change. Furthermore, the very great difference in the Herschel effect corresponding to different intensity levels of pre-exposure gave a striking illustration of the difference in center size produced at these different intensity levels.

Analysis of the particle-size distribution of the grains producing a photographic image

1. 1. The concentration of silver halide grains (number per square centimeter) in the multilayer photographic film coating and their size distribution were determined for the emulsion under investigation. These two analyses were also made for the halide grains unaffected by exposure and development for the steps of an unfixed sensitometric step wedge; a corresponding normally fixed density step wedge was used to determine the densities. The concentration and size distribution of the developable grains that, upon exposure and development, produce the densities of the step wedge were obtained by subtraction of the data of the residual grains from the corresponding data of the original total number of emulsion grains. 2. 2. The grains of this emulsion were formed during precipitation principally on two types of nuclei, as evidenced by the break in the normal function. 3. 3. The ratio of the number of grains, N d, to the optical density, D, is a constant, N d =4.0×10 8·D , which is substantially unchanged between 3- and 12-min. development. 4. 4. The relation between the average size (as projective area) of the developable grains and the density is practically a linear one. 5. 5. The size distribution of the undeveloped grains in the maximum densities, D max, by exposure, with increasing development times, is shown graphically and discussed. About 32 per cent of the grains are still undeveloped as the development approaches maximum development. The size distribution resembles that of a simple negative exponential form, with the smallest grains being predominant in number. These fine grains have a very low sensitivity. 6. 6. A case is cited in which a very slow but definite increase of density occurred upon prolonged exposure after the usual shoulder was reached. 7. 7. Since the size distribution of the residual undeveloped grains of each exposure step resembles that of the undeveloped emulsion in type, the effect of exposure on the statistical size-distribution parameters is presented. For a lognormal distribution, the ratio of the arithmetic average to the median size, x ̄ a / x ̄ med , or the difference of their logarithms, is simply related to the fundamental dispersion, K, of the emulsion precipitate and is a good measure of it. 8. 8. The arithmetic average size and also the median size of the developable grains decrease linearly with increase of the logarithm of the exposure for the range studied. The fundamental dispersion of the developable grains, however, increases with exposure.

Absolute Sensitivity Measurements on Single-Grain-Layer Photographic Plates for Different Wave-Lengths*

Single-grain-layer photographic plates were prepared from a non-color-sensitized, slow-speed, uniform-grain-size emulsion and exposed to very pure monochromatic light of wave-lengths λ3600A, λ4500A, and λ5000A. Intensity-scale characteristic curves were made on a double monochromator in which the energy of the exposures could be measured with an accuracy of ±5 percent. Data for plotting the characteristic curves were obtained by microscopic grain counts of developed and undeveloped grains for successive exposure steps. These were then plotted in several different ways: First, the fractions of developed grains, k/N (k is the developed and N the total number of grains per unit area) were plotted as a function of the incident exposure in terms of ergs per square centimeter of plate area. Second, the k/N values were plotted as a function of incident exposure in terms of quanta per average grain. Finally, using absorption data obtained for thin layers of silver bromide, the k/N values were plotted as a function of quanta absorbed per grain. Experimentally, it is found that the characteristic curves increase their slope with increasing wave-length of exposing radiation and also show a tendency to increase in slope with decreasing development time.The characteristic curves are analyzed by means of the Poisson statistical equation to determine the number of quanta actually utilized in formation of the latent image. Preparatory to this analysis, exposures were made to alpha-particles, and it is shown that the single-grain-layer plates accurately obey the single-hit formula derived from the Poisson equation. From the analysis of the curves obtained with monochromatic light exposures, it is concluded that the threshold sensitivity of a grain, expressed as the minimum number of quanta to produce developability of the grain, is of the order of ten quanta per grain for the emulsion under test. The upper limit of sensitivity is specified by the number of quanta absorbed per grain as shown by the abscissa values of the characteristic curves.Reciprocity-law failure measurements were made on the single-grain-layer plates, using unfiltered tungsten radiation. Time-scale characteristic curves were made over an intensity range of 1:16,384. The curves showed some loss of speed with reduced intensity but mainly a reduction in slope. This indicates that the grains of the upper and lower parts of the characteristic curve do not behave the same toward reduced intensity, and the grains of the upper part of the curve show the greater loss in speed at low intensity.