Photographing the x-ray image intensifier in the RUM-20m system
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The system for controlling the anode current while maintaining the voltage at the anode at the value selected in screening mode directly before photography in the RUM-20M provides for photography with the recording circuits of the power supply and raises the x-ray dose rate appropriately.
The RUM-20M provides exposure times of 0.013–0.05 sec for all values of the anode voltage corresponding to viewing conditions, which allows photographs to be recorded up to 6 frames per second. This range of exposure times is provided with a variation in dose rate at the exposure screen of the image intensifier before recording between 60±10 and 300±30 µR/sec.
The error in maintaining constant density in the frames in a series is not more than ±10%.
The setting of Va.p should be chosen in accordance with curve 4 of Fig. 2, with the 48 kV setting replaced by 52 kV and 91 kV by 100 kV. The setting for Ia.p should be 40, 60, and 100 mA in accordance with the number of divisions of the range in Va.v.
The discrete settings of Va.p are equal in number to the settings of Va.v, and therefore in automatic control there can be up to 20% difference between these values. Such conditions arise when Va.v is close to the threshold values for the interface unit. Any reduction in Va.p by comparison with Va.v causes a considerable increase in the exposure time relative to the optimum value, while an excess value for Va.p results in a considerable reduction in texp. Consequently, future development must include an increase in the number of settings for Va.p, which should be at least as many as the number of settings for recording series in the RUM-20M.
KeywordsExposure Time Dose Rate Automatic Control Photography Considerable Increase
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