We experimentally made the high-speed drum camera which had the motor of 80,000 rounds per minute (rpm) at rotating mirror on object beam. This paper describes results of the experiments about its basic optics, the subjects in the future and plans for improvement of the performance. The experimental monochromatic CCD image showed that the optical system employed in present study is proper basically. Additionally, this camera enable to the high-speed photography at about 520,000 frames per second, and we could show the specific policy to realize 1,000,000 frames per second in the near future.
In previous experiment, some papers reported that circular truncated shape can make suitable radiation output for radiography in comparison with cylinder target. Therefore, we carried out experiments to confirm the influence of the tip shape of the titanium target in the radiation dose using the x-ray tube, which have used by former experiment. It visualized an x-ray source using the Computed Radiography (CR) system and it measured the spatial distribution of the radiation dose relatively. At the same time, tube voltage and current was measured by high-voltage divider and current transformer, respectively. Prepared target shapes are cylinder and circular truncated cone. As the result, in this experiment, a beam spot was seen only with the tip of the target. Moreover, radiation dosage is influenced in distance between target and graphite cathode, rather than in shape of the target. In present study, we did not clearly recognize improvement of x-ray output dosage by using circular truncated cone target as before.
High-voltage condensers in a polarity-inversion two-stage Marx surge generator are charged from -50 to -70 kV using a power supply, and the electric charges in the condensers are discharged to an x-ray tube after closing the gap switches in the surge generator using a trigger device. The x-ray tube is a demountable diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Clean copper Kα lines are produced using a 10-μm-thick nickel filter, since the tube utilizes a disk cathode and a rod target, and bremsstrahlung rays are not emitted in the opposite direction to that of electron acceleration. The peak tube voltage increased with increasing charging voltage. At a charging voltage of -70 kV, the peak tube voltage and current were 140 kV and 0.8 kA, respectively. The pulse widths were approximately 30 ns, and the maximum dimension of the x-ray source was 3.0 mm in diameter. The number of generator-produced Kα photons was approximately 2.5x106 photons/cm2 at 0.5 m per pulse.
Aiming to realization of compact flash x-ray facilities, flash x-ray generator with two-stage Marx generator and a krytron pulse generator was constructed and its characteristics were verified in present study. Target and cathode of the x-ray tube was tungsten rod and graphite disk plate, respectively. Two-stage Marx generator applied high voltage to the target and discharge between electrodes produced plasma and x-ray. Experiments revealed the relationship between tube voltage, tube current and applied voltage to x-ray tube. Effect of distance from target to cathode was also made clear. Measurement of radiation output with plastic scintillator indicated the shorter pulse duration than 100 ns and the effect on application of present experimental configuration to high-speed photography. Radiographs were taken with computed radiography (CR) system. The photographs displayed enough resolution to perform fine photography and existence of soft x-ray for wide purposes. Present study implies application of present simple x-ray system to realization of compact and general-purpose x-ray generator.
The fundamental study on a high-intensity flash light generator and its applications are described. This generator is composed of a high-voltage power supply, high-voltage main condensers of 8 and 4 μF, a thyristor pulse generator as a trigger device, and a high-intensity xenon tube. The main condenser is charged up to 2.5 kV by the high-voltage power supply, and the electric charges in the condenser are discharged to the xenon tube by the thyristor pulse generator. The flashlights are then produced. The tube voltage and discharge current displayed almost the dumped oscillations. The maximum voltage was equal to the initial charging voltage, and the maximum current increased according to increases in the charging voltage and the capacity. The current was 4.1 kA with a charging voltage of 2.5 kV and a capacity of 8 μF. The pulse widths of flashlights were almost constant at a constant condenser capacity and increased with increases in the capacity. The widths were about 8 μs with a capacity of 8 μF. The shadowgraphy was performed using this generator and a trigger delay device. Finally, we performed tentative studies on parallel and point light sources.
In this study, we have made a low photon energy flash x-ray generator with a titanium target and have measured the radiographic characteristics. The flash x-ray generator consists of a high-voltage power supply, a high-voltage condenser, a turbo molecular pump and a flash x-ray tube. The condenser is charged up to about 30 kV, and the electric charges in the condenser are discharged to the tube after triggering the cathode. The linear plasma x-ray source forms from the target evaporation, and then the flash x-rays are generated from the plasma in the axial direction. K-series emission of titanium has been confirmed in experiments qualitatively and characteristics of the generator have been measured. K-series x-ray of titanium had a high resolution and enable us to take radiographs of a thin rabbit's ear clearly using the CR (Computed Radiography) system. The effect of titanium on the target of the soft flash x-ray tube has been indicated accordingly.
Fundamental study on quasi-monochromatic parallel radiography using a polycapillary plate and a plane-focus x-ray tube is described. The x-ray generator consists of a negative high-voltage power supply, a filament (hot cathode) power supply, and an x-ray tube. The negative high-voltage is applied to the cathode electrode, and the transmission type target (anode) is connected to the ground potential. The maximum voltage and current of the power supply were -100 kV (peak value) and 3.0 mA, respectively. In this experiment, the tube voltage was regulated from 20 to 25 kV, and the tube current was regulated by the filament temperature and ranged from 1.0 to 3.0 mA. The exposure time is controlled in order to obtain optimum film density, and the focal spot diameter was about 10 mm. The polycapillary plate is J5022-21 made by Hamamatsu Photonics Inc., and the outside and effective diameters are 87 and 77 mm, respectively. The thickness and the hole diameter of the polycapillary are 1.0 m and 25 μm, respectively. The x-rays from the t ube are formed into parallel beam by the polycapillary, and the radiogram is taken using an industrial x-ray film of Fuji IX 100 without using a screen. In the measurement of image resolution, we employed three brass spacers of 2, 30, and 60 mm in height. By the test chart, the resolution fell according to increases in the spacer height without using a polycapillary. In contrast, the resolution slightly fell with corresponding increases in the height by the polycapillary. In angiography, fine blood vessels of about 100 μm are clearly visible.
Previous studies on deflagration-to-detonation transition (DDT) have been carried out in detonation tubes, where the role of the solid wall of the tube is important. It is necessary to eliminate the wall effect for the investigation of three-dimensional DDT. Small explosive charges with charge masses of a few milligrams are useful for ignition purposes to generate spherical shock waves without wall effects. However, it was observed in our experiments that the shape of the shock waves is not always spherical. In a detonable mixture, the shape of the wave fronts often has many conical shock protrusions behind which the main wave front expands more rapidly. The conical waves are generated by fragments, which penetrate the main spherical shock wave. Regions of high turbulence are built up behind the fragments. From the results it can be inferred that DDT occurs in these turbulence regions, inducing locally a higher velocity of the following portion of the main wave front. In this study, we conducted tests of spherical detonation waves to investigate three- dimensional DDT. Time-resolved shadowgraphs and holographic interferograms were taken for visualization.
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