X-ray tubes and generators

Currently, X-ray machines are widely used in various industries. They are used to study the structure of materials, evaluate the internal structure of parts of components and mechanisms, as well as for nondestructive testing of various technological operations. One of the key components of X-ray machines is the high-voltage power supply in combination with the X-ray tube. There are two design schemes for their construction: monoblock and cable. A monoblock device is characterized by placing an X-ray tube and a highvoltage power source in one housing. In a cable machine, the X-ray tube is connected to a power source using a high-voltage cable. Each of the schemes has its own advantages and disadvantages. Its choice depends on the requirements for the design of the device. Purpose of the work: Development of a stabilized high-voltage power source for X-ray tubes as part of a cable apparatus. Materials and methods: During the design, programs were used to simulate processes occurring in electronic circuits using the SPICE (Simulation Program with Integrated Circuit Emphasis) algorithm. The basis of the source was an inverter voltage converter, built on power bipolar transistors according to a full bridge circuit with an insulated gate. This approach made it possible to simplify the power part of the electrical circuit of the source, increasing its overall efficiency. A solid-state compound with increased thermal conductivity was used as high-voltage insulation, which made it possible to limit it to forced air cooling and place its structure within the dimensions of the Rack Mount standard. Results: The result of the work was a stabilized high-voltage power supply with a voltage of 50 kV, a power of 2 kW, and a total weight of 27 kg. Conclusion: In connection with the departure of Western manufacturers from the Russian market of highvoltage power supplies, broad prospects are opening up for the use of domestic developments both in the creation of new models and in operating X-ray devices. Operating experience has shown that the developed highvoltage power supply is not inferior to the best foreign analogues in its electrical and weight-size parameters.

The generation of X-rays is discussed in the first section of this chapter. X-rays are generated by (1) the bombardment of a target by electrons, (2) the decay of certain radio isotopes, (3) as part of the synchrotron-radiation spectrum and (4) in plasmas produced by bombarding targets with high-energy laser beams. The spectra produced by the first method consist of a line spectrum characteristic of the target material accompanied by a continuum of white radiation (Bremsstrahlung). The intensities and wavelengths of these components are discussed and the nomenclatures of the lines in the characteristic spectrum are compared. Synchrotron radiation and plasma generation of X-rays are discussed very briefly. X-ray wavelengths are discussed in the second section of the chapter. Tables of K- and L-series reference wavelengths and K- and L-emission lines and absorption edges are provided. X-ray absorption spectra are discussed in the third section of the chapter. A detailed discussion of the problems associated with the measurement of X-ray absorption and the requirements for the absolute measurement of the X-ray attenuation coefficients is followed by a description of the problems which are encountered in making measurements at X-ray absorption edges of atomic species in materials. The popular, and extremely valuable, experimental technique of X-ray absorption fine structure (XAFS) is discussed. This is a relative, rather than an absolute measurement of X-ray absorption, and the theoretical analysis of XAFS spectra depends on the deviation of the data points from a cubic spline fit to the data rather that the deviation from the extrapolation of the free-atom absorption. A brief description of the origin and use of X-ray absorption near edge structure (XANES) is given. In the fourth section of the chapter, X-ray absorption (or attenuation) coefficients are considered. A detailed description of the theoretical and experimental techniques for the determination of X-ray absorption (and attenuation coefficients) is given. The tables supercede the existing experimental and theoretical tables that were available up to 2001. The theoretical values given here are restricted to the characteristic radiations commonly available from laboratory X-ray sources (Ti Kβ to Ag Kα). Computational problems become significant for elements in the lanthanide and actinide series of the periodic table. These tables include a significant recalculation of the absorption and attenuation coefficients for the lanthanide series. Note that although many theory-based tables exist, few accurate experimental measurements have been made on atomic species with atomic numbers greater than 50, especially in the region of absorption edges. A comparison is given of the extent to which theoretical and experimental data agree. A recent tabulation discusses soft X-ray absorption in the XANES region. Filters and monochromators are discussed in the fifth section of the chapter. This section serves as an introduction to the use of filters and monochromators in experimental apparatus. It discusses, using synchrotron-radiation experimental configurations as examples, the use of X-ray reflectivity, X-ray refraction and X-ray Bragg (and Laue) or Fresnel scattering for the production of monochromatic or quasi- monochromatic (pink) beams from polychromatic sources. Amongst the techniques discussed are: bent and curved mirrors, capillaries, quasi-Bragg (multilayer) mirrors, multiple filters, crystal monochromators, polarization and polarization-producing systems, and focusing using a Bragg–Fresnel optical system. The development of monochromators for synchrotron-radiation research is a rapidly evolving field, but in practice all depend on either the processes of reflection, refraction or scattering, or combinations of these processes. In the final section of the chapter, X-ray dispersion corrections are considered. The various theoretical methods for the computation of the X-ray dispersion corrections and the experimental techniques used for their determination are described in some detail. The theoretical values given here are restricted to the characteristic radiations commonly available from laboratory X-ray sources (Ti Kβ to Ag Kα). An artificial distinction is made between the relativistic Dirac–Hartree–Fock–Slater (RDHFS) formalism used to calculate the data in these tables and the S-matrix method used by a number of theoreticians. Formally, the two techniques are equivalent: in terms of the computations the two approaches are different, and the outcomes are different. Comparison with experimental data shows that the RDHFS formalism gives a better fit to experimental results. Keywords: absorption; anomalous dispersion; atomic form factor; atomic scattering factors; attenuation coefficients; Auger shifts; Bijvoet-pair techniques; black-body radiation in X-ray region; characteristic line spectrum; continuous spectrum; Dirac–Fock method; dispersion corrections; EXAFS; extended X-ray absorption fine structure; filters; Friedel-pair techniques; generation of X-rays; intensity; monochromators; normal attenuation; photo-effect data; QED corrections; Rayleigh scattering; scattering; synchrotron radiation; theoretical Rayleigh scattering data; theoretical photo-effect data; wavelengths; X-ray absorption coefficients; X-ray absorption spectra; X-ray attenuation coefficients; X-ray dispersion corrections; X-ray sources; X-ray tubes; X-ray wavelengths; XAFS; X-ray absorption near-edge structure; XANES

Aim:An image-guided radiotherapy capable linear accelerator was installed at our hospital which is equipped with an X-ray volumetric imaging (XVI) system. The aim of this study was to describe the results of acceptance tests which were carried out on the XVI facility to verify the manufacturer’s specification.Materials and methods:The commissioning test had six elements: system safety, geometric accuracy, image quality, registration and correction accuracy, X-ray tube and generator performance, and quality assurance (QA) procedures.Results:We had satisfactory results for all the tests. The system passed the safety testes, and the agreement of isocentres was found to be within the tolerance limit. Imaging quality was acceptable. Registration and correction accuracy was tasted with indigenously developed phantom and positioned accurately at isocentre. X-ray tube and generator test results showed that the tube was performing properly.Findings:The described tests represent that the performance of the system is maintained at acceptable levels.

Triboluminescence is a luminous phenomenon resulted from friction; for example, peeling scotch tape, breaking rock sugar with a hammer, peeling mica and so on. Triboluminescence is well known over 50 years but in 2008 UCLA group reported the radiation of x-ray region by triboluminescence in vacuum for the first time <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> . UCLA group made an automatic machine which peels scotch tape. With a view to practical application of triboluminescence to roentgen diagnosis we made an automatic peeling machine similar to that of UCLA group. An x-ray tube for conventional roentgen diagnosis needs a high voltage power supply. In contrast, triboluminescence does not need it. So it is very useful for roentgen diagnosis to replace a conventional x-ray tube with triboluminescence. Thus far, we have attempted to confirm the x-ray generation from triboluminescence using a filtered phosphor screen when the parameters such as the followings are changed; peeling speed, atmospheric pressure, variety of scotch tape, emission angle etc. Then in a similar way we have also attempted to measure x-ray dose from triboluminescence using a potable dosemeter. It was found that the x-ray generation has a directional property. Because the method to peel scotch tapes does not enable to operate continuously, new method without scotch tapes has been proposed <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 – 3</sup> . The new method repeatedly contacts silicone with epoxy to produce x-ray. In this conference, we have reported a novel method to generate xray radiation by triboluminescence. Two circular discs are co ntacted and rotated: The discs are made of different materials. We have made a new-type triboluminescence equipment and examined its characteristics when the following conditions are changed; combinations of contact materials, rotating velo city, radiation direction, pressure and so on.

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.

The purpose of this invention is to provide an X-ray thickness gauge in which, using a simple configuration, measurement error due to temperature drift in the amount of radiation delivered by said X-ray thickness gauge after thickness calibration has been performed can be corrected, even while in the process of performing a measurement. Said X-ray thickness gauge (100) is provided with the following: an X-ray generator (1) provided with both a cooling unit (1b) that uses a cooling medium to cool an X-ray tube (1a) and a power-supply unit (1c) that supplies power that is applied to said X-ray tube; a detector (5) that detects delivered detection radiation that has passed through an object (4) being measured; a calibration device (2) provided with a thickness reference sample; and a computation unit (6) that references a calibration table to determine the thickness of the object being measured. This X-ray thickness gauge is also provided with a temperature sensor (7) that measures the temperature of the cooling medium. The computation unit is provided in advance with a temperature-correction table from which a detection-radiation delivery amount corresponding to the difference between the temperature of the cooling medium during calibration and the temperature of the cooling medium during a measurement can be determined. The computation unit references said temperature-correction table to determine the amount of detection radiation to deliver and references the abovementioned calibration table to determine the abovementioned thickness.

The purpose of this study is to characterize a newly built flat panel detector (FPD)-based cone beam CT (CBCT) prototype for dynamic imaging. A CBCT prototype has been designed and constructed by completely modifying a GE HiSpeed Advantage (HSA) CT gantry, incorporating a newly acquired large size real-time FPD (Varian PaxScan 4030CB), a new x-ray generator and a dual focal spot angiography x-ray tube that allows the full coverage of the detector. During data acquisition, the x-ray tube and the FPD can be rotated on the gantry over Nx360 degrees due to integrated slip ring technology with the rotation speed of one second/revolution. With a single scan time of up to 40 seconds , multiple sets of reconstructions can be performed for dynamic studies. The upgrade of this system has been completed. The prototype was used for a series of preliminary phantom studies: different sizes of breast phantoms, a Humanoid chest phantom and scatter correction studies. The results of the phantom studies demonstrate that good image quality can be achieved with this newly built prototype.

K-edge angiography utilizing a tungsten plasma X-ray generator in conjunction with gadolinium-based contrast media

The air kerma, which is the amount of energy given off by a radioactive substance, is essential for medical specialists who use radiation to diagnose cancer problems. The amount of energy that a photon has when it hits something can be described as the air kerma (the amount of energy that was deposited in the air when the photon passed through it). Radiation beam intensity is represented by this value. Hospital X-ray equipment has to account for the heel effect, which means that the borders of the picture obtain a lesser radiation dosage than the center, and that air kerma is not symmetrical. The voltage of the X-ray machine can also affect the uniformity of the radiation. This work presents a model-based approach to predict air kerma at various locations inside the radiation field of medical imaging instruments, making use of just a small number of measurements. Group Method of Data Handling (GMDH) neural networks are suggested for this purpose. Firstly, a medical X-ray tube was modeled using Monte Carlo N Particle (MCNP) code simulation algorithm. X-ray tubes and detectors make up medical X-ray CT imaging systems. An X-ray tube’s electron filament, thin wire, and metal target produce a picture of the electrons’ target. A small rectangular electron source modeled electron filaments. An electron source target was a thin, 19,290 kg/m3 tungsten cube in a tubular hoover chamber. The electron source–object axis of the simulation object is 20° from the vertical. For most medical X-ray imaging applications, the kerma of the air was calculated at a variety of discrete locations within the conical X-ray beam, providing an accurate data set for network training. Various locations were taken into account in the aforementioned voltages inside the radiation field as the input of the GMDH network. For diagnostic radiology applications, the trained GMDH model could determine the air kerma at any location in the X-ray field of view and for a wide range of X-ray tube voltages with a Mean Relative Error (MRE) of less than 0.25%. This study yielded the following results: (1) The heel effect is included when calculating air kerma. (2) Computing the air kerma using an artificial neural network trained with minimal data. (3) An artificial neural network quickly and reliably calculated air kerma. (4) Figuring out the air kerma for the operating voltage of medical tubes. The high accuracy of the trained neural network in determining air kerma guarantees the usability of the presented method in operational conditions.

A combination small and wide angle diffractometer is described. This instrument permits collection of both small angle and normal diffractometer data as a specimen is subjected to mechanical, chemical, or thermal treatment. Curved crystal focusing optics is utilized. The useful range of the apparatus is 0.023 to approximately 60° 2θ. The apparatus has the following features: (1) excellent resolution over the entire usable angular range (the focused primary beam has a half-breadth of 4×10−4 rad); (2) simplicity of design; (3) monochromatization of x rays; (4) ample specimen space, enabling one to heat, deform, or otherwise perturb specimens in situ. The unit utilizes a ground and bent quartz crystal, a Picker diffractometer, and a Hilger microfocus x-ray tube and generator. The basic unit can be assembled largely from factory-available apparatus, the exceptions being special mounts for the x-ray tube and the monochromator. The alignment procedure is briefly outlined and the positions of the necessary adjusting devices are described. A specimen heater, incorporated in this instrument and accurate to ±¼ C° from room temperature to about 150°C, is described. The heater utilizes the passage of hot gases to maintain the temperature. Finally, small and wide angle scattering curves are shown to illustrate the utility of the apparatus.

K. Cranley, Measurement of the Performance Characteristics of Diagnostic X-ray Systemsused in Medicine, Part 1: X-Ray Tubes and Generators (IPEM Report 32). 2nd Edn. The Institute of Physics and Engineering in Medicine and Biology

In the plasma flash x-ray generator, high-voltage main condenser of about 200 nF is charged up to 55 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 cerium target of 3.0 mm in diameter by electric field in the x-ray tube, the weakly ionized linear plasma, which consists of cerium ions and electrons, forms by target evaporating. At a charging voltage of 55 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, weakly ionized cerium plasma formed, and the K-series characteristic x-ray intensities increased. The x-ray pulse widths were about 500 ns, and the time-integrated x-ray intensity had a value of about 40 μC/kg at 1.0 m from x-ray source with a charging voltage of 55 kV. In the angiography, we employed a film-less computed radiography (CR) system and iodine-based microspheres. Because K-series characteristic x-rays are absorbed easily by the microspheres, high-contrast angiography has been performed.

The fundamental studies for the repetitive high-intensity microsecond x-ray generator utilizing a cold cathode tetrode are described. This generator consisted of the following essential components: a constant high-voltage power supply, an energy storage condenser of 500nF, an main discharge condenser of lOnF, a turbo molecular pump, a repetitive trigger device, and an x-ray tube. The condenser was charged from 40 to 80kV, and the electric charges in the condenser were discharged repetitively to an x-ray tube by a trigger device. The x-ray tube was of the tetrode type which was connected to a turbo molecular pump and consisted of the following major parts: a rod-shaped long anode tip made of tungsten, a cathode rod made of graphite, a ring-shaped grid electrode, and a trigger electrode. The trigger electrode was mounted at the center of the cathode electrode and was insulated by a ceramic tube. The tube current was about 0. 4kA with a charged voltage of 60kV. The x-ray pulse height and the time-integrated intensity increased when the condenser charged voltage was increased, and the intensity was less than 2. OpC/kg at lm per pulse. The exposure times were about 2Ops, and the repetition frequency was less than 50Hz.

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.

A miniature, interstitial x-ray generator has recently been developed and is currently undergoing clinical trials for the treatment of brain tumors. The maximum photon energy from this x-ray tube is 50 keV, although most of the initial testing has been carried out at 40 keV. Dose rates of up to 2 Gy/min in a water phantom at a distance of 10 mm from the tube tip are produced. In this paper we describe the modeling and simulation of x-ray production from this device using the ITS 3.0 Monte Carlo code. Verification of the simulation of x-ray production in the device was carried out by comparing predictions of spatial photon distribution, energy spectrum, and dose versus depth in water with experimentally obtained measurements. Agreement between the simulated results and experimental measurements was fairly good when comparing the angular distribution of photons emitted from the x-ray tube and very good when comparing dose rate versus depth in a water phantom. Discrepancies observed when comparing the calculated and measured estimates of characteristic line radiation were reduced by incorporation of a modification to the ITS code. Possible causes of the remaining discrepancy in bremsstrahlung intensity are discussed.