The dark and light current-characteristics of Xeroradiographic plates have been considered by the theoretical and preliminary experimental investigation.
The relations between the surface potential on the plates and the dv/dt in a dark decay curve have approximately indicated an exponential curve. Therefore, an RC model cannot fit to it.
The X-ray decay characteristics of Xeroradiographic plates in X-ray radiation are disclosed as follows: ,
where E is the X-ray energy, φ is X-ray density, β is the X-ray energy absorption coefficient, L is the thickness of selenium film, μ is the mobility of carrier and F(t) is the factor to time in which the effects owing to trapping carriers, recombination of carriers and radiation of secondary electrons have been included.
Results are that the photosensitivity in X-ray radiation has proportionately increased with the thickness of selenium film and X-ray energy absorption coefficient and X-ray dose rate.

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We have made some experiments on X-ray characteristics of selenic plates in Xeroradiography. We prepared several different materials in selenic layer thickness and then charged upon the surface of selenium film with electrostatic charge, and we irradiated X-ray radiation to measure the decay of surface potential in succession.
1) To measure the decay of surface potential of selenic plates when a selenic layer 10~50μ in thickness is irraddiated by a certain intensity of X-ray radiation.
2) To measure the decay of surface potential of selenic plates for a selenic layer thickness 50μ when the X-ray intensity is changed.
Our preliminary experiments have proved that the more thicker the se layer, the more the X-ray sensitivity in the selenic plates is increased.

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Influence of moiture on the surface conductivity of Zinc Oxide was examined. While the dark conductivity was found to increase by adsorbing moisture, the photoconductivity was decreased and so the photoconductive sensitivity was decreased in proportion to relative humidity.

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Some electrophotographic methods using PIP (persistent intemal polarization) of phosphor layers are reported recentry about their characteristics and their possibility of utllization to practical uses in the region of visible infrared, and ultraviolet light.
The performance, of PIP in radiology, however are quite unknown essentially. We have examined the characteristics of the radiography with PIP, mainly in the tube voltage region from 60 kVp to 90 kVp X-ray for medical purposes. Experiments were perfomed by the nearly same procedures as in the visible region, applying dc field to phosphor sheets sandwiched between two electrodes during excitation with X-ray, as one of which electrodes on the incident side an Al film evaporated on a 2mm thick bakelite base was used.
Using an electrometer of rotating sector type, polarization charge quantities were measured, and also the reflection density corresponding to the charge quantities was decided after having fixed toners on the sheets by usual methods.
Comparing this method with the usual silver halide photographic method (using intensifying screen Fs), sensitivity from 1/10 to 1/25, a little poorer contrast, and higher resolving power were obtained, and this sensitivity was competitive to that with radiography of nonscreen type.
Improvements in the characteristics of the photography are expected to be possible by several means. Essential increase of sensitivity could be effected by using Phosphor sheets more sensitive to X-ray.

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The authors reported some experimental data on reversal dqvelopment of continuous tone latent images on electrophotographic layer. It makes use of the phenomena that the corona charging is considerably suppressed at the surface of electrophotographic layer when deposited with somewhat conductive toner particles.
The process is as follows, roughly coinciding with Mr. Sugarman's⁽¹⁾: First, the photoconductive layer after exposure is developed using a magnetic brush (powdered iron mixed with semi-conductive toner particles), and then the layer is completely discharged by lightexposure and by natural leakage. Then, the powder-deposited layer is re-charged by corona in the dark, producing reversed latent images on the layer. The image is re-developed by another magnetic brush, containing toner particles for common printing use (not necessarily semiconductive), thus reversed visible images are given.
The above mentioned method is suitable for representing continuous tone images.
Theoretical discussions are given with some photographic examples.

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Potential drops of charged organic resin films were experimentally studied when they were irradiated by X-ray. And a behavior of the potential variation was qualitatively analysed. From these experimental results, the value of life time-drift mobility product of excited free carriers in silicicon resin was obtained.

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