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A diagnostic fluoroscopy X-ray system uses a 32kW or greater X-ray generator for obtaining real-time moving images and high-resolution images. Fluoroscopy X-ray systems have to use a high-capacity AC power source to perform long-time low-power fluoroscopy and short-time high-power spot exposure. In this paper, we propose a hybrid type X-ray generator for fluoroscopy X-ray system which can perform fluoroscopy and spot exposure with a low-capacity AC power source and an energy storage device. The characteristics of energy storage devices are compared and each energy storage device is modelled to equivalent circuit. And the characteristics of available energy are analyzed as a function of output voltage and power. A 32kW class hybrid X-ray generator with EDLC as an energy storage device for fluoroscopy X-ray system was constructed, and its validity was verified by means of simulations and experiments.

X-ray systems for medical treatment use noninvasive procedures. Being capable of locally inspecting the inside of the body, X-ray systems are routinely used for basic diagnosis. X-ray systems to be used for medical purposes were originally made with a gas filled tube inside an induction coil in the initial stages of development but with this approach it becomes difficult to take a satisfactory picture through thick body sections, non invasively. However continued development made it possible to take non-invasive pictures of breasts, blood vessels and other body parts through thick body sections. Recently, high-voltage X-ray generators of more compact size, increased generation efficiency, and sophisticated output control have become possible. All of these features are made possible by the use of a high-frequency output from an inverter and a fast switching semiconductor device. In this paper, we describe a new X-ray generator operating with a resonant inverter in order to reduce switching loss and high frequency noise. In addition, in order to identify the differences amongst types of rectification, we have compared output and the quality of X-ray pictures obtained with full-wave rectification and dual-voltage rectification methods.

A preliminary experiment for producing narrow-photon-energy cone-beam X-rays using a silicon single crystal is described. In order to produce low-photon-energy X-rays, a 100-μm-focus X-ray generator in conjunction with a (1 1 1) plane silicon crystal is employed. The X-ray generator consists of a main controller and a unit with a high-voltage circuit and a microfocus X-ray tube. The maximum tube voltage and current were 35 kV and 0.50 mA, respectively, and the X-ray intensity of the microfocus generator was 48.3 μGy/s at 1.0 m from the source with a tube voltage of 30 kV and a current of 0.50 mA. The effective photon energy is determined by Bragg's angle, and the photon-energy width is regulated by the angle delta. Using this generator in conjunction with a computed radiography system, quasi-monochromatic radiography was performed using a cone beam with an effective energy of approximately 17 keV.

The tungsten plasma flash X-ray generator is useful in order to perform high-speed enhanced K-edge angiography using cone beams because K-series characteristic X-rays from the tungsten target are absorbed effectively by gadolinium-based contrast media. In the flash X-ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash X-rays are produced by the discharging. The X-ray tube is a demountable diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current were approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the characteristic X-ray intensities of tungsten K α lines increased. The K α lines were clean, and hardly any bremsstrahlung rays were detected. The X-ray pulse widths were approximately 110 ns, and the time-integrated X-ray intensity had a value of approximately 0.35 mGy at 1.0 m from the X-ray source with a charging voltage of 80 kV. Angiography was performed using a film-less computed radiography (CR) system and gadolinium-based contrast media. In angiography of non-living animals, we observed fine blood vessels of approximately 100 μm with high contrasts.

High-voltage condensers in a polarity-inversion two-stage Marx surge generator are charged from -40 to -60 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. Sharp K-series characteristic X-rays of molybdenum are produced without using a monochromatic 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 and increasing space between the target and cathode electrodes. At a charging voltage of -60 kV and a target-cathode space of 1.0 mm, the peak tube voltage and current were 110 kV and 0.75 kA, respectively. The pulse width ranged from 40 to 100 ns, and the maximum dimension of the X-ray source was 3.0 mm in diameter. The number of generator-produced K photons was approximately 7×1014 photons/cm2s at 0.5 m from the source.

We describe a generator of soft X-rays of energy between 2 and 10 keV by sparking in hydrogen, air, nitrogen, argon and xenon gases at low pressure with a sparking voltage as low as ∼0.8 kV. The X-ray events appear to come in clusters, with an average mean multiplicity of 3 per single event into the solid angle of our detector; the extrapolated production into a 4π-solid angle is more than ∼1500 pulses per event, assuming the isotropic distribution. The device operates with the peak spark currents 0.2–0.5 kA and the total spark charge more than 4×10 14 electrons/spark. The spark stored energy 0.024–0.17 J/pulse is more than four orders of magnitude smaller compared to experiments reporting similar X-ray production. The X-ray generator can be used as a simple monitor of the gaseous detectors, or a device to study various gaseous phenomena occurring in large sparks.

Indirect determination of X-ray generator kilovoltage (kV) using the ratio of differentially filtered beam measurements has been known for 20 years. Measurement of generator potentials used for diagnostic computed tomography (CT), conventional X-ray, and mammography typically requires filter cassettes or special instruments in the X-ray beam; the resulting readings are usually accurate within /spl plusmn/2%. A related technique, free of many theoretical and practical restrictions, provides simplified generator potential measurements with significantly improved accuracy. Curve fitting provides a simple relationship predicting generator kV from a measured filter response ratio. Routine use has established that this technique is robust, reliable, repeatable, and more accurate than most working standards.

The survey of the parameters of diagnostic X-ray apparatus, that is, tube voltage, tube current and exposure time, was carried out. The nominal parameters chosen were 70kV, 200mA and 0.1s. Forty-seven institutions were visited, using a total of 63 machines. Most devices meet the JIS for the voltage (±7% to the nominal value) and exposure time (±10%). As for the current, 19 (30.2% of all) devices were out of the JIS (±10%). No significant differences were found between the rectifying methods. If the specific dose (mGy/mAs) is estimated by the nominal parameters, the error of the dose would be 20 to 30%. The quality assurance of the device is very important for the optimization of medical exposure.

High voltage power is needed by diverse application fields such as high precision medical equipment, and development of an X-ray generator equipped with large capacity power is accordingly required. Commercial AC power based X-ray generator has a disadvantage of having limitation in the location and of being sensitive to the power characteristics, the necessity for an independent power type X-ray generator is increasing recently. For this reason, development of an energy storage device based stand-alone type X-ray generator is required. This paper compared characteristics of energy storage devices, and composed equivalent models of each energy storage devices, and analyzed characteristics of available energy as a function of output voltage and power. An energy storage device based 32 [kW] class X-ray generator was constructed, and the output characteristics of diagnostic X-ray generators with each energy storage devices were compared through simulations and experiments.

A 10 kHz pulsed X-ray generator utilising a hot-cathode triode in conjunction with a new type of grid control device for controlling X-ray duration is described. The energy-storage condenser was charged up to 70 kV by a power supply, and the electric charges in the condenser were discharged to the X-ray tube repetitively by the grid control device. The maximum values of the grid voltage (negative value), the tube voltage, and the tube current were -1.5 kV, 70 kV, and 0.4 A, respectively. The duration of the flash X-ray pulse was primarily determined by the time constant of the grid control device and the cut-off voltage of thermoelectrons. The X-ray duration was controlled within a region of less than 1 ms; the X-ray intensity with a pulse width of 0.27 ms, a charged voltage of 70 kV, and a peak tube current of 0.4 A was 0.92 microC kg-1 at 0.5 m per pulse. The maximum repetition rate was about 10 kHz, and the size of the focal spot was about 3.5 x 3.5 mm.

The fundamental studies of a repetitive soft flash x‐ray generator having a high‐durability diode for high‐speed radiography in biomedical and technological fields are described. This generator consisted of the following essential components: a constant negative high‐voltage power supply, a line‐type high‐voltage pulser with two 10 m coaxial‐cable condensers, each with a capacity of 1.0 nF, a thyratron pulser as a trigger device, an oil‐diffusion pump, and a flash x‐ray tube. The x‐ray tube was of a diode type which was evacuated by an oil‐diffusion pump with a pressure of approximately 6.7×10−3 Pa and was composed of a planar tungsten anode, a planar ferrite cathode, and a polymethylmethacrylate tube body. The space between the anode and cathode electrodes (AC space) could be regulated from the outside of the tube. The two cable condensers were charged from −40 to −60 kV by a power supply, and the output voltage was about −1.5 times the charged voltage. Both the first peak voltage and current increased a...

The constructions and the radiographic characteristics of a kilohertz-range harder pulsed x-ray generator having a hot-cathode diode are described. This generator consisted of the following major components: a thyratron pulser (HRTP-16), a high-voltage pulse transformer, a DC power supply for the filament, and a hot-cathode diode. The ceramic condenser in the thyratron pulser was charged from 8 to 16 kV, and the electric charges in the condenser were discharged to the primary coil of. the transformer. Then the high-voltage pulse of about 100 kV flour the secondary coil was applied to the diode, and harder pulsed x rays were produced. The thyratron pulser was driven by the repetitive electric or light pulses. When the multiple-pulse-type was employed, the x-ray duration was nearly equivalent to the damped oscillation of the tube voltage. In the case where the single-pulse-type was employed, the x-ray pulse width had a value of about 300 ns. The repetition rate was controlled by the frequency of the driving pulse.

The construction and the fundamental studies of a repetitive flash x‐ray generator having a simple diode with an energy‐selective function are described. This generator consisted of the following components: a constant high‐voltage power supply, a high‐voltage pulser, a repetitive high‐energy impulse switching system, a turbo molecular pump, and a flash x‐ray tube. The circuit of this pulser employed a modified two‐stage surge Marx generator with a capacity during main discharge of 425pF. The x‐ray tube was of the demountable‐diode type which was connected to the turbo molecular pump and consisted of the following major devices: a rod‐shaped anode tip made of tungsten, a disk cathode made of graphite, an aluminum filter, and a tube body made of glass. Two condensers inside of the pulser were charged from 40 to 60 kV, and the output voltage was about 1.9 times the charging voltage. The peak tube voltage was primarily determined by the anode‐cathode (A‐C) space, and the peak tube current was less than 0.6 kA. The peak tube voltage slightly increased when the charging voltage was increased, but the amount of change rate was small. Thus, the maximum photon energy could be easily controlled by varying the A‐C space. The pulse width ranged from 40 to 100 ns, and the x‐ray intensity was less than 1.0 μC/kg at 0.3 m per pulse. The repetitive frequency was less than 50 Hz, and the effective focal spot size was determined by the diameter of the anode tip and ranged from 0.5 to 3.0 mm in diameter.

High-sensitive radiography system utilizing a kilohertz-range stroboscopic x-ray generator and a night-vision CCD camera (MLX) is described. The x-ray generator consists of the following major components: a main controller, a condenser unit with a Cockcroft-Walton circuit, and an x-ray tube unit in conjunction with a grid controller. The main condenser of about 500 nF in the unit is charged up to 100 kV by the circuit, and the electric charges in the condenser are discharged to the triode by the grid control circuit. The maximum tube current and the repetition rate are approximately 0.5 A and 50 kHz, respectively. The x-ray pulse width ranges from 0.01 to 1.0 ms, and the maximum shot number has a value of 32. At a charging voltage of 60 kV and a width of 1.0 ms, the x-ray intensity obtained without filtering was 6.04 μGy at 1.0 m per pulse. In radiography, an object is exposed by the pulse x-ray generator, and a radiogram is taken by an image intensifier. The image is intensified by the CCD camera, and a stop-motion image is stored by a flash memory device using a trigger delay device. The image quality was improved with increases in the x-ray duration, and a single-shot radiography was performed with durations of less than 1.0 ms.

The gadolinium plasma flash x-ray generator is useful for performing high-speed enhanced K-edge angiography using cone beams because K-series characteristic x-rays from the gadolinium target are absorbed effectively by iodine-based contrast media. In the flash x-ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash x-rays are produced by the discharging. The x-ray tube is a demountable cold-cathode diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current are approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the K-series characteristic x-ray intensities of gadolinium increased. Bremsstrahlung x-ray intensity rate decreased with increasing the charging voltage, and clean K lines were produced with a charging voltage of 80 kV. The x-ray pulse widths were approximately 100 ns, and the time-integrated x-ray intensity had a value of approximately 500 μGy at 1.0 m from the x-ray source with a charging voltage of 80 kV. Angiography was performed using a filmless computed radiography (CR) system and iodine-based contrast media. In the angiography of nonliving animals, we observed fine blood vessels of approximately 100 μm with high contrasts.

A prototype thermionic-electron gun for a highly bright X-ray generator has been developed. Its extraction voltage and design current are 60 kV and 100 mA (DC), respectively. Based on the EGUN simulation, the first prototype electron gun is fabricated. The main specifications of the prototype electron gun were firstly measured by pulsed beams, and confirmed that the maximum beam current of 85.7 mA focused on the rotating anticathode with a spot size of 0.79 mm times 0.13 mm. In the DC beam test in progress, beam current is limited by the increase of temperature on the periphery of beam duct. With the treatment for the heating, extracted beam current has been growing to 24 mA without serious increase of temperature.

A microfocus x-ray tube is useful in order to perform magnification digital radiography including phase-contrast effect. The 100-µm-focus x-ray generator consists of a main controller for regulating the tube voltage and current and a tube unit, with a high-voltage circuit and a fixed anode x-ray tube. The maximum tube voltage, current, and electric power were 105 kV, 0.5 mA, and 50 W, respectively. Using a 3.0-mm-thick aluminum filter, the x-ray intensity was 26.0 µGy/s at 1.0 m from the source with a tube voltage of 60 kV and a current of 0.50 mA. Because the peak photon energy was approximately 35 keV using the filter with a tube voltage of 60 kV, the bremsstrahlung x-rays were absorbed effectively by iodine-based contrast media with an iodine K-edge of 33.2 keV. Real-time magnification radiography was performed by twofold magnification imaging with an image intensifier camera, and angiography was achieved with iodine-based microspheres 15 µm in diameter. In angiography of non-living animals, we observed fine blood vessels of approximately 100 µm with high contrasts.

Energy-selective high-speed radiography utilizing a kilohertz-range stroboscopic x-ray generator and its application to high-speed angiography are described. This generator consists of the following major components: a main controller, a condenser unit with a Cockcroft-Walton circuit, and an x-ray tube unit in conjunction with a grid controller. The main condenser of about 500 nF in the unit is charged up to 120 kV by the circuit, and the electric charges in the condenser are discharged to the triode by the grid control circuit. Although the tube voltage decreased during the discharging for generating x-rays, the maximum value was equal to the initial charging voltage of the main condenser. The maximum tube current and the repetition rate were approximately 0.5 A and 50 kHz, respectively. The x-ray pulse width ranged from 0.01 to 1.0 ms, and the maximum shot number had a value of 32. At a charging voltage of 100 kV and a width of 1.0 ms, the x-ray intensity obtained using a 50-μm-thick tungsten filter was 9.88 μGy at 1.0 m, and the dimensions of the focal spot had values of approximately 1×1 mm. Angiography was performed using the filter at a charging voltage of 100 kV.

In the plasma flash x-ray generator, a 200 nF condenser is charged up to 50 kV by a power supply, and flash x rays are produced by the discharging. The x-ray tube is a demountable triode with a trigger electrode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Target evaporation leads to the formation of weakly ionized linear plasma, consisting of molybdenum ions and electrons, around the fine target, and intense characteristic x rays are produced. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 16 kA. When the charging voltage was increased, the linear plasma formed, and the K-series characteristic x-ray intensities increased. The K lines were quite sharp and intense. The x-ray pulse widths were approximately 600 ns, and the time-integrated x-ray intensity had a value of approximately 65 μC/kg at 1.0 m from the x-ray source with a charging voltage of 50 kV.

In the flash x-ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash x rays are produced by the discharging. The x-ray tube is a demountable diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current were approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the K-series characteristic x-ray intensities of molybdenum increased. The K lines were clean and intense, and hardly any bremsstrahlung rays were detected at all. The x-ray pulse widths were approximately 100 ns, and the time-integrated x-ray intensity had a value of approximately 15 μC/kg at 1.0 m from the x-ray source with a charging voltage of 80 kV.

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.

Energy-selective high-speed radiography utilizing a kilohertz-range stroboscopic x-ray generator and its application to high-speed angiography are described. This generator consists of the following major components: a main controller, a condenser unit with a Cockcroft-Walton circuit, and an x-ray tube unit in conjunction with a grid controller. The main condenser of about 500 nF in the unit is charged up to 100 kV by the circuit, and the electric charges in the condenser are discharged to the triode by the grid control circuit. Although the tube voltage decreased during the discharging for generating x rays, the maximum value was equal to the initial charging voltage of the main condenser. The maximum tube current and the repetition rate were approximately 0.5 A and 32 kHz, respectively. The x-ray pulse width ranged from 0.01 to 1.0 ms, and the maximum shot number had a value of 32. At a charging voltage of 80 kV and a width of 1.0 ms, the x-ray intensities obtained without filtering, using an aluminum filter, and using a barium sulfate filter were 14.8, 5.48 and 5.05 μGy per pulse, respectively, at 1.0 m, and the dimensions of the focal spot had values of 3.5×3.5 mm. Angiography was performed using both the aluminum and the barium sulfate filters at a charging voltage of 60 kV.

The high-voltage condensers in a polarity-inversion two-stage Marx surge generator are charged from -50 to -70 kV by a power supply, and the electric charges in the condensers are discharged to an x-ray tube after closing gap switches in the surge generator with 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 silver Kα lines are produced using a 30 μm-thick palladium 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. At a charging voltage of -70 kV, the instantaneous tube voltage and current were 90 kV and 0.8 kA, respectively. The x-ray pulse widths were approximately 80 ns, and the instantaneous number of generator-produced Kα photons was approximately 40 M photons/cm 2 per pulse at 0.3 m from the source of 3.0 mm in diameter.

In the plasma flash x-ray generator, a high-voltage main condenser of approximately 200 nF is charged up to 50 kV by a power supply, and electric charges in the condenser are discharged to an x-ray tube after triggering the cathode electrode. The flash x-rays are then produced. The x-ray tube is a demountable triode that is connected to a turbo molecular pump with a pressure of approximately 1 mPa. As electron flows from the cathode electrode are roughly converged to a rod copper target of 3.0 mm in diameter by the electric field in the x-ray tube, weakly ionized linear plasma, which consists of copper ions and electrons, forms by target evaporation. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 15 kA. When the charging voltage was increased, the linear plasma formed, and the K-series characteristic x-ray intensities increased. The K-series lines were quite sharp and intense, and hardly any bremsstrahlung rays were detected. The x-ray pulse widths were approximately 700 ns, and the time-integrated x-ray intensity had a value of approximately 30 μC/kg at 1.0 m from the x-ray source with a charging voltage of 50 kV.

In the plasma flash x-ray generator, high-voltage main condenser of about 200 nF is charged up to 50 kV by a power supply, and electric charges in the condenser are discharged to an x-ray tube after triggering the cathode electrode. The flash x-rays are then produced. The x-ray tube is of a demountable triode that is connected to a turbo molecular pump with a pressure of approximately 1 mPa. As electron flows from the cathode electrode are roughly converged to a rod iron target of 3.0 mm in diameter by electric field in the x-ray tube, the weakly ionized linear plasma, which consists of iron ions and electrons, forms by target evaporating. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 20 kA. When the charging voltage was increased, the linear plasma formed, and the K-series characteristic x-ray intensities increased. The x-ray pulse widths were about 800 ns, and the time-integrated x-ray intensity had a value of about 10 μC/kg at 1.0 m from x-ray source with a charging voltage of 50 kV. The plasma x-rays were diffused after passing through two lead slits.

The tentative experiment for production low photon energy characteristic x-rays using a capillary is described. The capillary of this flash x-ray tube was improved in order to increase the x-ray intensity and to generate high-intensity characteristic x-rays by forming the linear plasma x-ray source. The generator consists of a high-voltage power supply, a polarity-inversion ignitron pulse generator, a turbo-molecular pump, and a radiation tube with a capillary. A high-voltage condenser of 0.2(mu) F in the pulse generator is charged up to 20 kV by the power supply, and the electric charges in the condenser are discharged to the capillary in the tube after closing the ignitron. In the present work, the pump evacuates air from the tube with a pressure of about 1 mPa, and the aluminum anode and cathode electrodes are employed to produce characteristic x-rays. The diameter and the length of the capillary are 2.0 and 29 mm, respectively, and both the cathode voltage and the discharge current displayed almost the damped oscillations. The peak values of the voltage and current increased when the charging voltage was increase, and their maximum values were -9.2 kV and 4.6 kA, respectively. The x-ray durations detected by a 1.6 micrometers aluminum filter were less than 10microsecond(s) , and we observe the intensity of aluminum characteristic x-rays.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The radiographic characteristics of the condenser-discharge stroboscopic x-ray generator and its application to high-speed radiography are described. This generator employs a condenser- discharge medical x-ray generator in conjunction with a new grid-control unit and consists of the following major components: a high-voltage control unit, a condenser unit having a Cockcroft circuit, a grid-control unit, a high- voltage grid-control unit, and a rotating-anode x-ray tube unit. The main condenser of about 500 nF in the unit is charged up to 120 kV by the circuit, and the electric charges in the condenser are discharged to the triode by the grid control unit in conjunction with a high-voltage grid-control unit. The high-voltage grid-control unit is employed in order to insulate the negative high-voltage grid and cathode electrodes from the high-speed grid control unit with almost the ground potential. In this generator the anode and cathode electrodes are applied to high-voltages with maximum values of +60 kV and -60 kV, respectively. Although the tube voltage decreased during the discharging for generating x- rays, the maximum value was equivalent to the initial charging voltage of the main condenser. The maximum values of the tube current and the repetition rate were about 0.5 A and 32 kHz, respectively. The pulse width of the x-rays ranged from 0.01 to 1.0 ms, and the maximum shot number had a value of 32. At a constant filament (cathode) temperature, the x-ray intensity increased according to increases in the charging voltage and to increases in the duration, and the maximum intensity with a duration of 1.0 ms and a charging voltage of 100 kV was 0.66 (mu) C/kg at 1.0 m from the x-ray source. The dimensions of the focal spot had values of about 1 X 1 mm, and both the inner and outer triggering for producing pulse x-rays can be employed. The high-speed radiography was primarily performed by the multiple-shot radiography using a new computed radiography (CR) system in conjunction with the computer- display system with an operation system of Windows NT Workstation 4.0.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The radiogprahic characteritics of the condenser-discahrge stroboscopic x-ray genrator and its application to high-speed radiogprahy are described.This gnerator employs a coneser- discharge medical x-ray gnerator in conjunctionwith a new grid-control unit and consists of the following major componets: a high -voltage control unit, a condenser unit having a Cockcroft circuit,a grid-control unit, a high- voltage grid-control unit,a nd a rotating-anode x-ray tube unit.The main condesner of about 500 nF in the unit is charged up to 120 kV by the circuit and the electric charges inthe condene are dischargd to the triode by the grid control unit i9n conjunction with a hgih-voltage grid-control unti The highv-otalgd grid-control unit is employed inorder to insulate the negative hgih-voltage grid and acathode electrods from th ehgihs-peed grid control unit with almost the ground potnetial. Inthis gnerator, th anode and cathode lectrodes ar applied tohigh-voltages with maximumvalues of +60 kV and -60 kV, respectively. Although the tube voltrage decased during the discharging for gnerating x-rays, the maximum vlaue was equivlaent to th eitnital charging vortlag eof th emiain condenser. Th3 amsximu values of the tub ecurrent and the repetiton rat3 awer about 0.5 A and 32 kHz, respectively. The pulse widthof the x-rays ranged from 0.01 to 1.0 ms, and the maximumshot number ahd a vlaue of 32. At a constant filament (cathode) tmerpature,the x-ray intensity incrased accordign to incrases in teh charging voltage and toincrases in the duration and the maximum intensity with a duration of 1.0 ms and a charging voltage of 100 kV awas 0.66 (mu) C/kf at 1.0 m from the -ray source.The dimensiosn sof the focal spot had values of about 1 X 1 mm, and both the inner and outer triggering for produicng pulse c-rays acan be employed. The hgih-speed radiogrpahy was primari9ly performed by temultpe- shot radiogprhay using a new computed radiogprhay (CR) system in conjuctiown tiht ehcomuter-dispaly sysem with an operationsyste of Windows NT Workstation 4.0.

The radiographic characteristics and the applications of an improved high-photon-energy stroboscopic x-ray generator are described. This generator is primarily designed in order to increase the maximum photon energy of the pulse x-rays and is composed of the following essential components: a thyratron pulse generator, a high-voltage transformer having a ferrite core with a maximum output voltage of 300 kV, a sequence controller, a DC power supply for the cathode (filament), and an x-ray tube. The main condenser of about 50 nF in the thyratron pulse generator is charged up to 15 kV, and the electric charges in the condenser are discharged repetitively to the primary coil of the transformer. Because the high- voltage pulses from the secondary coil are then applied to the x-ray tube, repetitive harder x-rays are produced. The x-ray tube is of a triode having a hot-cathode that is primarily driven at the temperature-limited current region. In this triode, because the grid is connected to the cathode, this tube is driven as a diode. The tube voltage roughly increased in proportion to the charging voltage, and the maximum value was about 300 kV. Thus, the maximum photon energy had a value of about 300 keV. The tube current was primarily regulated by the filament temperature and had values of less than 2 A. The x-ray output displayed almost single pulses, and the width of the first pulse was about 300 ns. The maximum repetition rate was about 1 kHz, and the dimension of the x-ray source had values of about 3.5 X 3.5 mm. The high-speed radiography was primarily performed by both the delayed and the multiple- shot radiographies using a new computed radiography (CR) system.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The radiographic characteristics of a high-intensity kilohertz-range stroboscopic x-ray generator (SX-C98) are described. This generator consists of the following major components: a controller, a condenser unit having a Cockcroft circuit, and an x-ray tube unit in conjunction with a grid controller. The main condenser of about 500 nF in the unit is charged up to 100 kV by the circuit, and the electric charges in the condenser are discharged to the triode by the grid controller. Although the tube voltage slightly decreased during the discharging for generating x-rays, the maximum value was equivalent to the initial charging voltage of the main condenser. The maximum values of the tube current and the repetition rate were about 0.5 A and 32 kHz, respectively. The pulse width of the x-rays ranged from approximately 0.01 to 1.0 ms, and the maximum shot number had a value of 32. At a constant filament (cathode) temperature, the x-ray intensity increased according to increases in the charging voltage and to increases in the duration, and the intensity with a duration of about Ims and a charging voltage of 70 kV was 140 nC/kg at 1.0 m per pulse. When the charging voltage was increased, the dimension of the focal spot slightly increased, and the maximum values were about 3.5 X 3.5 mm.

Various characteristics of a plasma flash x-ray generator having a cold-cathode radiation tube and its application to high-speed soft radiography are described. The x-ray generator employs a high-voltage power supply, a low-impedance coaxial transmission line with a gap switch, a high-voltage condenser with a capacity of about 200 nF, a turbo-molecular pump, a thyristor pulser as a trigger device, and a flash x-ray tube. The high-voltage main condenser is charged up to 60 kV by the power supply, and the electric charges in the condenser are discharged to the tube after triggering the cathode electrode. The flash x-rays are then produced. The x-ray tube is of a demountable triode which is connected to the turbo molecular pump with a pressure of approximately 1 mPa. As the electron flows from the cathode electrode are roughly converged to the target by the electric field in the tube, the plasma x-ray source which consists of metal ions and electrons is produced by the target evaporating. Both the tube voltage and current displayed damped oscillations, and their peak values increased according to increases in the charging voltage. In the present work, the peak tube voltage was almost equivalent to the initial charging voltage of the main condenser, and the peak current was less than 30 kA. In this experiment, we employed four types of plasma targets as follows: (1) single target, (2) coaxial double target, (3) alloy target, and (4) plate target. When the single target in conjunction with the monochromatic filter was employed, high-intensity quasi- monochromatic x-rays were obtained. Next, the characteristic x-ray intensities from the outer target increased in the case where the double target was used. By using the alloy (copper tungsten) target, the x-ray intensities of the copper K-series lines increased. Finally, when the linear plasma x-ray source was formed by using the plate target, the bremsstrahlung x- rays were absorbed and were converted into florescent rays, and high-intensity characteristic x-rays were produced.

The fundamental study on a flash water-window x-ray generator (WFX-98) is described. This generator is composed of a high- voltage power supply, a polarity-inversion ignitron pulser, an oil-diffusion pump, and a radiation tube with a capillary. The high-voltage condenser of about 0.2 (mu) F in the pulser is charged up to 20 kV by the power supply, and the electric charges in the condenser are discharged to the capillary in the tube after closing the ignitron. In the present work, the chamber is evacuated by the pump with a pressure of about 1 mPa, and the titanium anode and cathode electrodes are employed to produce L-series characteristic x-rays in the water-window range. The diameter and the length of the ferrite capillary are 2.0 and 29 mm, respectively. Both the cathode voltage and the discharge current displayed damped oscillations. The peak values of the voltage and current increased when the charging voltage was increased, and their maximum values were -11 kV and 3.8 kA, respectively.

The constructions of a plasma flash x-ray generator having a cold-cathode radiation tube and its application to soft radiography are described. The x-ray generator employs a high- voltage power supply, a low-impedance coaxial transmission line with a gap switch, a high-voltage condenser with a capacity of 0.2 (mu) F, a turbo-molecular pump, a thyristor pulser as a trigger device, and a flash x-ray tube. The high- voltage main condenser is charged up to 60 kV by the power supply, and the electric charges in the condenser are discharged to the tube after triggering the cathode electrode. The flash x-rays are then produced. The x-ray tube is a demountable triode which is connected to the turbo molecular pump with a pressure of approximately 1 mPa. This tube consists of a rod-shaped carbon cathode, a trigger electrode made from a copper wire, a stainless-steel vacuum chamber, insulators, a polyethylene terephthalate x-ray window, and two anode electrodes (targets) of molybdenum and silver. The space between the anode and cathode electrodes had a constant value of approximately 20 mm, and the trigger electrode is set in the center of the cathode electrode. As the electron flows from the cathode electrode are roughly converged to the target by the electric field in the tube, the plasma x-ray source which consists of metal ions and electrons is produced by the target evaporating. Because the bremsstrahlung spectra are absorbed by the monochromatic filter, K-series characteristic x-rays are obtained. Both the tube voltage and current displayed damped oscillations, and their peak values increased according to increases in the charging voltage. In the present work, the peak tube voltage was almost equivalent to the initial charging voltage of the main condenser, and the peak current had a value of about 25 kA with a charging voltage of 60 kV. When the charging voltage was increased, the intensities of the K-series characteristic x-rays increased. Next, the intensities decreased as the monochromatic filter was inserted. Using this quasi-monochromatic plasma flash x- ray generator, we performed high-speed soft radiography with x-ray durations of about 1 microsecond.

The fundamental study on a soft flash x-ray generator utilizing an ignitron is described. This generator consists of the following essential components: a high-voltage power supply, a high-voltage pulser having an ignitron, an oil diffusion pump, and a flash x-ray tube. The x-ray tube employs a molybdenum anode rod, a pipe-shaped carbon cathode, a polymethylmeth acrylate tube body, and a polyethylene terephthalate x-ray window. The space between the anode and the cathode electrodes (ac space) can be controlled by rotating the anode rod. The high-voltage condenser in the pulser is charged from 40 to 60 kV by the power supply, and the electric charges in the condenser are discharged to the tube by the ignitron through a 2.0 m coaxial cable. Because the maximum anode voltage of the ignitron is 50 kV, a free-air gap switch is employed in order to increase the high-voltage durability. In the present work, the anode electrode is connected to the ground, and the negative high-voltage output is applied to the cathode electrode. The flash x-rays are then produced. The peak cathode voltage and tube current had values of minus 56 kV and 11.5 kA, respectively, with a charging voltage of 60 kV and an ac space of 6.0 mm, and the pulse widths were less than 300 ns.

The fundamental study on a flash water-window x-ray generator is described. This generator is composed of a high-voltage power supply, a polarity-inversion high-voltage pulser, a krytron pulser as a trigger device, an oil-diffusion pump, and a vacuum chamber with a capillary. A combined ceramic condenser of about 5 nF in the pulser is charged up to 70 kV by the power supply, and the electric charges in the condenser are discharged to the capillary in the tube after closing a gap switch by the krytron pulser. In the present work, the chamber is evacuated by the pump with a pressure of about 1 by 10-3 Pa, and the titanium anode and cathode electrodes are employed to produce L-series characteristic x rays in the water-window range. The diameter and the length of the ferrite capillary are 2.0 and 30 mm, respectively. Both the cathode voltage and the discharge current displayed damped oscillations. The peak values of the voltage and current increased when the charging voltage was increased, and their maximum values were minus 24 kV and 2.8 kA, respectively. The pulse durations of the water-window x-rays were nearly equivalent to those of the damped oscillations of the voltage and current, and their values were less than 10 microseconds.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report the design, fabrication, and preliminary characterization of a compact X-ray generator for improved X-ray absorption imaging that uses a nanostructured field emission cathode (FEC) as the electron source and a microstructured transmission anode as the X-ray generating element. FECs consume less power, respond faster, and tolerate lower vacuum than thermionic cathodes used in conventional X-ray generators. The use of a transmission anode, instead of a conventional reflection anode, allows filtering of the background radiation (brems strahlung) while allowing efficient generation of X-rays at lower voltages by exciting atomic shell transitions, resulting in emission of X-rays with narrow spectral linewidth for sharper imaging of biological tissue. The fabricated FEC contains arrays of self-aligned, gated field emitters that turn on at bias voltages under 30 V and transmit 99.5% of the electrons to the anode. The FEC emits a maximum current of 1.2 μA per field emitter (588 μA total array current) at a bias voltage of 85 V. A facility is built and tested to generate X-rays with an FEC and a transmission anode. Using the facility, we obtained an X-ray absorption image of an ex-vivos ample that clearly shows softtissue and fine bone structures.

The development of a high-intensity kilohertz-range pulsed x-ray generator and its application to dental radiography are described. The pulsed x-ray generator consisted of the following major components: a constant high-voltage power supply, a high-voltage main condenser, a hot-cathode triode, a DC power supply for the filament (hot cathode), and a grid controller. The main condenser of 0.5 (mu) F - 100 kV in the pulser was charged from 50 to 70 kV by the power supply, and the electric charges in the condenser were discharged to the triode by the grid controller. To be exact, the tube voltage decreased during the discharging for generating pulsed x rays, yet the maximum value was equivalent to the initial charged voltage of the main condenser. The maximum values of the tube current and the repetition rate were about 0.5 A and 30 kHz, respectively. The pulse width of the x rays ranged from approximately 20 to 400 microsecond(s) , and the x-ray intensity with a charged voltage of 70 kV and a total resistance of 5.1 M(Omega) was about 0.83 (mu) C/kg at 1.0 m per pulse. Using this generator, high-speed dental radiography, e.g., delayed radiography and multiple-shot radiography, was performed.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The constructions and the fundamental studies of two types of kilohertz-range harder pulsed x- ray generators are described. The multiple-pulse generator was primarily designed in order to increase the x-ray intensities even when the x-ray duration increased. In contrast, as the damped oscillation of the tube voltage was prevented by using two high-voltage diodes, we designed the single-pulse generator to obtain short x-ray durations. Each generator employed the following essential components: a thyratron pulser, a high-voltage double transformer, a storage battery for the hot cathode (filament), and an x-ray tube. The main condenser in the pulser was charged from 8 to 16 kV, and the electric charges in the condenser were repetitively discharged to the primary coils of the transformer. Because the high-voltage impulses from the secondary coils were then applied to the x-ray tube, repetitive x rays were generated. The x-ray tube was of a diode having a hot-cathode with a maximum temperature of about 2,000 K. The tube voltage increased in proportion to the charged voltage, and the maximum value was about 170 kV. The tube current was primarily determined by both the filament temperature and the tube voltage and had values of less than 1.5 A. The maximum intensities of the multiple and single types were about 48 and 16 nC/kg at 0.5 m per pulse. The x-ray pulse widths obtained by the single generator were less than 250 ns, and the maximum repetition rate was approximately 10 kHz.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A 30 kHz pulsed x-ray generator utilizing a hot-cathode triode in conjunction with a new type of grid controller for varying the x-ray duration is described. This generator consisted of the following essential components: a constant high-voltage power supply, a high- voltage main condenser of 97 nF, a DC power supply for the filament (hot cathode), and a hot-cathode triode. The high-voltage main condenser was charged from 50 to 70 kV by the power supply, and the electric charges in the condenser were discharged to the x-ray tube repetitively by the grid controller. The maximum values of the grid voltage (negative value) and the tube current were about -2.2 kV and 0.6 A, respectively. The x-ray duration was controlled by the time constant of the grid controller and the electron cutoff voltage. The x-ray intensity with a pulse width of 70 microsecond(s) and a charged voltage of 70 kV had a value of 1.26 (mu) C kg-1) at 0.5 m per pulse. The maximum repetition rate was about 30 kHz, and the size of the x-ray source had a value of 3.5 X 3.5 mm.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The constructions and the fundamental studies of a flash x-ray generator having a liquid-anode diode are described. This flash x-ray generator consisted of the following essential components: a high-voltage power supply, a high-voltage pulser, a thyratron pulser as a trigger device, an oil diffusion pump, and a flash x-ray tube. The main condenser was negatively charged from 50 to 70 kV by the power supply, and the electric charges in the condenser were discharged to the x-ray tube after closing a gap switch by using the thyratron pulser. The flash x- ray tube was of a diode type having a mercury anode and a ferrite cathode. The pressure of the tube was primarily determined by the steam pressure of mercury as a function of temperature. The maximum output voltage from the pulser was about -1 times the charged voltage. The maximum tube voltage and current were approximately 60 kV and 3 kA, respectively, with a charged voltage of -60 kV and a space between the anode and cathode electrodes (AC space) of 2.0 mm. The pulse widths of flash x rays were about 50 ns, and the x-ray intensity measured by a thermoluminescence dosimeter had a value of about 2.5 (mu) C/kg at 0.3 m per pulse with a charged voltage of -70 kV and an AC space of 1.0 mm.

The constructions and the fundamental studies of two types of kilohertz- range pulsed x-ray generators are described. The multiple-pulse generator was primarily designed in order to increase the x-ray intensities even when the x-ray duration increased. In contrast, as the damped oscillation of the tube voltage was prevented by using a high- voltage diode in conjunction with a resistor, we designed the single- pulse generator to obtain short x-ray durations. Each generator employed the following essential components: a thyratron pulser, a high-voltage transformer, a CD power supply for the cathode (filament), and an x-ray tube. The main condenser in the pulser was charged from 8 to 16 kV, and the electric charges in the condenser were repetitively discharged to the primary coil of the transformer. Because the high-voltage impulses were then applied to the x-ray tube, repetitive x rays were generated. The x-ray tube was of a diode having a hot-cathode with a maximum temperature of about 2,000 K. The tube voltage increased in proportion to the charged voltage, and the maximum value was about 110 kV. The tube current was primarily determined by both the filament temperature and the tube voltage and has values of less than 1 A. The minimum widths of the pulsed x rays by the single type were less than 250 ns, and the maximum repetition rate was about 10 kHz.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The fundamental studies on a dual-energy flash x-ray generator for performing the energy-selective two-direction radiography are described. This generator consisted of the following components: a negative high- voltage power supply, a polarity-inversion-type high-voltage pulser having a 5 nF combined ceramic condenser, a turbo molecular pump, and two flash x-ray tubes. The condenser in the pulser was charged from -60 to -80 kV, and the electric charges in the condenser were discharged to two x-ray tubes. The maximum output voltage from the pulser was about -1.5 times the charged voltage because the cable transmission line was employed. Using a tube, the maximum tube voltage was about 110 kV. The maximum tube current and the x-ray intensity were less than 3 kA and 5 (mu) C/kg at 0.5 m per pulse, respectively. In contrast, the tube current and the intensity has approximately half the above values when two tubes were employed. The pulse widths were less than 200 ns, and two shots of flash x rays were obtained simultaneously. Each photon energy of flash x rays can be changed by controlling the space between the anode and cathode electrodes.

The fundamental studies for the repetitive flash x-ray generator operated at lowdose rates for a medical x-ray television system are described. This x-ray generator consisted of the following components: a high-voltage power supply, an energy storage condenser of lOOnF, a coaxial cable condenser with a capacity of l000pF, a repetitive impulse switching system, a turbo molecular pump, and an x-ray tube having a cold cathode. The condenser was charged from 40 to 70kV by a power supply, and the electric charges stored in the condenser were discharged repetitively by using a trigger electrode operated by an impulse switching system. The x-ray tube was of the triode-type which was connected to the turbo molecular pump and had a large discharge impedance in order to prevent the damped oscillations of the tube current and voltage. The maximum tube voltage was equivalent to the initial charged voltage, and the peak current was less than 70A. The durations were about 2ps, and the x-ray intensities were less than 1. OpC/kg at 0. 5m per pulse. The repetition frequency was less than 50Hz, and the effective focal spot size was equivalent to the anode diameter of 3. 0mm. For the x-ray television system used in conjunction with this repetitive pulsed x-ray generator, since the electromagnetic noise primarily caused by the high tube current was decreased, noise-free stroboscopic radiography performed by the television system could be realized.

The fundamental studies of the repetitive type of flash x-ray generator utilizing an enclosed-type diode with a ring-shaped graphite cathode for soft radiography are described. This generator consisted of the following essential components: a constant high-voltage power supply, an energy storage condenser of lOOnF, a highvoltage pulser, a repetitive impulse switching system, and a flash x-ray tube. The pulser employed a modified two-stage Marx circuit with a capacity during main discharge of 425pF. The x-ray tube was of the enclosed-diode type and consisted of the following major devices: a rod-shaped anode tip made of tungsten, a ring cathode made of graphite, an x-ray window made of beryllium, a spattering shield made of stainless steel, and a tube body made of glass. Two condensers in the pulser were charged from 50 to 70kV, and the output voltage was about 1. 6 times the charged voltage. Both the peak tube voltage and the peak tube current increased according to increases in the charged voltage, and the maximum values of the voltage and the current were about 90kV and 0. 5kA, respectively. The pulse width was about lOOns, and the x-ray intensity was less than 2. OpC/kg at 0. 5m per pulse. The repetition frequency was less than 50Hz, and the maximum size of the effective focal spot was nearly equivalent to the anode diameter of 3. 0mm.

The studies of a repetitive flash x-ray generator as an energy source achieved with a compact diode with a permeable anode are described. This source consisted of the following essential components: a constant negative high-voltage power supply of up to -100kV, a modified two-stage Marx pulser, a repetitive trigger device, and an x-ray tube. Two condensers in the pulser were charged from -50 to -80kV, and the output voltages (no-load) were less than -130kV. Since the capacity of each condenser was 85OpF, the total capacity during discharge was 425pF. The maximum tube voltage and the tube current were about 85kV and 0. 3kA, respectively. The xray pulse widths were less than l2Ons, and the repetitive rate was less than 40Hz. The time-integrated x-ray intensity was about 25pC/kg at 24mm per pulse with a charged voltage of 60kV and an anode-cathode (A-C) space of 9. 0mm, and the maximum size of the x-ray source was equivalent to an anode diameter of 27mm.

The fundamental studies for the repetitive pulsed x-ray generator utilizing a hot cathode triode operated at high repetitive rates in the kllz-range are described. This generator consisted of the followingessential components: a constant high- voltage power supply, an energy storage condenser, a grid pulser, a DC-DC converter for supplying grid bias voltages, and an x-ray tube. The x-ray tube was of an enclosed-triode type and consisted of the following devices: an anode rod made of copper, a plane anode tip (target) made of tungsten, a grid made from tungsten wire, a focusing electrode made of iron, a hot-cathode (filament) made of tungsten, and a glass body. The condenser which was attached to the anode electrode was charged from 50 to 70kV, and the electric charges in the condenser were discharged repetitively by the grid electrode operated by the grid pulser. The pulse width was primarily determined by the pulse width from the grid pulser, the grid bias voltage, and the cut-off voltage for thermoelectrons, and could be controlled to about ips. The x-ray pulse height primarily increased according to increases in the charged voltage at a constant grid bias voltage. The x-ray intensity was 1. 35nC/kg at 0. 5m per pulse with a condenser charged voltage of 70kV, a grid bias voltage of -1. 0kV, and the charged voltage of the grid pulser of 400V.

The fundamental studies on the high-intensity single flash x-ray generator having a low-vacuum diode for biomedical radiography are described. This generator consisted of the following essential components: a high-voltage power supply, a high-voltage pulser with a coaxial oil condenser of l5OnF, a low impedance transmission line made from four coaxial cables with lengths of 5. 6m and a total capacity of 292OpF, a mechanical booster pump, and a flash x-ray tube. The x-ray tube was of the diode-type which was connected to the booster pump with a constant pressure of 1. 7Pa and consisted of the following major devices: a long anode tip made of tungsten with a diameter (D) of less than 3. 0mm and a length (L) of 50mm, a long cathode tip made of tungsten with a D of 1. 0mm and a L of 40mm, a polyoxymethylene insulator, lead diaphragms, and an x-ray window made of polyethylene terephthalate. The coaxial oil condenser in the pulser was charged from 50 to 90kV, and the electric charges in the condenser were discharged to the flash x-ray tube through a transmission line by using a gas gap switch with a highcurrent capacity. The peak voltage increased according to increases in the condenser charged voltage and its value was more than the charged voltage. The peak current primarily increased when the charged voltage was increased, and its value was less than 4OkA. The pulse width of the flash x-rays ranged from 60 to 8Ons, and the time integrated x-ray intensity with a charged voltage of 90kV and an anode cathode (A-C) space of 3. 0mm was about 4pC/kg at 1. Om per pulse the source. The effective focal spot size was primarily determined by the diameter of the anode tip, and its value was about 3. 0mm when an anode diameter of 3. 0mm was employed.

A repetitive pulsed x-ray generator achieved with a compact diode utilizing a new type of cathode for biomedical radiography is described. This generator consisted of the following components: a high-voltage power supply, two ceramic condensers of about 850pF, a repetitive impulse switching system, a turbo molecular pump, and an x-ray tube. Since the high-voltage pulser employed a modified Marx circuit, this pulser produced twice the potential of the condenser charging voltage. The x-ray tube was of the demountable-diode type which was connected to the turbo molecular pump and consisted of the following components: a rod-shaped anode tip made of tungsten, a plane cathode made of aluminum and carbon, and a vacuum vessel made of glass with a diameter of 50mm. Two condensers were charged from 30 to 100kV, and the output of this pulser ranged from 50 to 180kV. The x-ray pulse widths primarily increased according to increases in the anode-cathode (A-C space) and their values ranged from 20 to 100ns. The repetitive rate was determined by the condenser capacity, the charging voltage, and the current capacity of the power supply, and its maximum value was about 100Hz. The time integrated x-ray intensities were less than 4.0pC/kg at 0.5m per pulse when the discharge capacity of about 430pF (Marx Circuit) was employed. The effective focal spot size was determined by the diameter of anode tip and its value ranged from 0.5 to 3.0mm in diameter.

The tantalum plasma flash X-ray generator is useful for performing high-speed enhanced K-edge angiography using cone beams because K-series characteristic X-rays from the tantalum target are absorbed effectively by gadolinium-based contrast media. In the flash X-ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash X-rays are produced by the discharging. The X-ray tube is a demountable cold-cathode diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current were approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the K-series characteristic X-ray intensities of cerium increased. The K lines were clean and intense, and hardly any bremsstrahlung rays were detected. The X-ray pulse widths were approximately 100 ns, and the time-integrated X-ray intensity had a value of approximately 300 µGy at 1.0 m from the X-ray source with a charging voltage of 80 kV. Angiography was performed using a filmless computed radiography (CR) system and gadolinium-based contrast media. In the angiography of nonliving animals, we observed fine blood vessels of approximately 100 µm with high contrasts.

The high-voltage condensers in a polarity-inversion two-stage Marx surge generator are charged from –50 to –70 kV by a power supply, and the electric charges in the condensers are discharged to an x-ray tube after closing gap switches in the surge generator with 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 silver K lines are produced using a 30-µm-thick palladium 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. At a charging voltage of –70 kV, the instantaneous tube voltage and current are 90 kV and 0.8 kA, respectively. The x-ray pulse widths are approximately 80 ns, and the instantaneous number of generator-produced K photons is approximately 4×107photons/cm2 per pulse at 0.3 m from the source 3.0 mm in diameter.