Target Tube Research Articles

Quantitative contrast-enhanced mammography for contrast medium kinetics studies

Quantitative contrast-enhanced mammography, based on a dual-energy approach, aims to extract quantitative and temporal information of the tumour enhancement after administration of iodinated vascular contrast media. Simulations using analytical expressions and optimization of critical parameters essential for the development of quantitative contrast-enhanced mammography are presented. The procedure has been experimentally evaluated using a tissue-equivalent phantom and an amorphous silicon active matrix flat panel imager. The x-ray beams were produced by a tungsten target tube and spectrally shaped using readily available materials. Measurement of iodine projected thickness in mg cm−2 has been performed. The effect of beam hardening does not introduce nonlinearities in the measurement of iodine projected thickness for values of thicknesses found in clinical investigations. However, scattered radiation introduces significant deviations from slope equal to unity when compared with the actual iodine projected thickness. Scatter correction before the analysis of the dual-energy images provides accurate iodine projected thickness measurements. At 10% of the exposure used in clinical mammography, signal-to-noise ratios in excess of 5 were achieved for iodine projected thicknesses less than 3 mg cm−2 within a 4 cm thick phantom. For the extraction of temporal information, a limited number of low-dose images were used with the phantom incorporating a flow of iodinated contrast medium. The results suggest that spatial and temporal information of iodinated contrast media can be used to indirectly measure the tumour microvessel density and determine its uptake and washout from breast tumours. The proposed method can significantly improve tumour detection in dense breasts. Its application to perform in situ x-ray biopsy and assessment of the oncolytic effect of anticancer agents is foreseeable.

An EDXRF method for determination of uranium and thorium in AHWR fuel after dissolution

AbstractA fast energy dispersive x‐ray fluorescence (EDXRF) method requiring only microgram amounts of analytes, i.e. uranium (U) and thorium (Th), in their mixtures in solution form is described. Calibration solutions and samples covering the fuel composition range (0–5% of U in U + Th) of advanced heavy water reactor (AHWR) were prepared by mixing uranium and thorium solutions. A known fixed amount of internal standard yttrium (Y) was added to these solutions. EDXRF spectra of calibration solutions and samples were measured by taking 20 µl aliquots on 30 mm diameter filter papers, after drying, using a Rh target tube operated at 40 kV and 500 µA. Calibration plots were made by plotting U/Y, U/Th and Th/Y amount ratios against the respective intensity ratios of Th Lα, U Lα and Y Kα. In the first set, U was determined using Y as an internal standard, and for Th determination, U, thus determined, was used as an internal standard since the amounts of Th and Y were kept constant in the calibration solutions and samples.In the second set, both U and Th were varied and determined using Y as internal standard. The results of U and Th determinations showed a precision of about 3% (1s) and the results deviated from the expected values by <3% in most of the cases. This approach has an advantage that it requires only microgram amounts of sample, thus mitigating radiation hazards associated with radioactive samples as well as the amount of radioactive analytical waste generated is quite less. Copyright © 2009 John Wiley & Sons, Ltd.

40kV용 투과 양극형 x-ray tube의 개발 및 특성분석

휴대용 XRF (X-Ray Fluorescence) 장치에 적용할 수 있는 40 kV용 투과 양극형 W-Target tube와 Rh-Target tube를 개발하고 특성을 조사하였다. 특성 x-ray의 에너지와 연속 x-ray의 선량특성은 알려진 결과와 잘 일치함을 확인하였고, 최대 선량을 추출하기 위한 양극금속 박막의 최적 두께는 W-target tube의 경우 약 <TEX>$2.6{\mu}m$</TEX>, Rh-target tube의 경우 약 <TEX>$2.7{\mu}m$</TEX> 임을 밝혀내었다. 또한 관전압 40 kV, 관전류 <TEX>$60{\mu}A$</TEX>로 30분 동안 연속적으로 작동시켰을 때 양극에서의 온도는 <TEX>$50^{\circ}C$</TEX>를 넘지 않아 휴대용 XRF장치에 적용할 수 있음을 확인하였다. Tungsten and rhodium target tube for a 40 kV x-ray transmission anode was developed to apply to the hand-held XRF(X-Ray Fluorescence) apparatus and its characteristics were evaluated. From the measurement of the energy distribution and dose of x-ray, it was confirmed that our results were good agreements with the known ones. The optimum thickness of metal film deposited on Be window to extract the maximum dose were <TEX>$2.6{\mu}m$</TEX> and <TEX>$2.7{\mu}m$</TEX> in case of W-target tube and Rh-target tube, respectively. When it was continuously worked during 30 min. at 40 kV in tube voltage and at <TEX>$60{\mu}A$</TEX> in tube current, the temperature at target did not exceed <TEX>$50^{\circ}C$</TEX>. Our results reveals that the 40 kV x-ray transmission anode tube can be applied to the hand-held XRF apparatus.

Separable Dynamic Programming and Approximate Decomposition Methods

We consider control, planning, and resource allocation problems involving several independent subsystems that are coupled through a control/decision constraint. We discuss one-step lookahead methods that use an approximate cost-to-go function derived from the solution of single subsystem problems. We propose a new method for constructing such approximations, and derive bounds on the performance of the associated suboptimal policies. We then specialize this method to problems of reachability of target tubes that have the form of a box (a Cartesian product of subsystem tubes). We thus obtain inner approximating tubes, which are the union of a finite number of boxes, each involving single subsystem calculations

Influence of the geometrical configuration on the plasma ionization distribution and erosion profile of a rotating cylindrical magnetron: a Monte Carlo simulation

The ionization distribution of a small scale rotating cylindrical magnetron discharge is simulated by a Monte Carlo based program. The simulation describes the high energy electron trajectories and the interaction between these electrons and the sputtering gas, which finally leads to the ionization distribution. By radial projection of the ionization positions on the target surface, the erosion track dimensions can be correctly simulated. The discrepancy between the simulation and the experiments shows the need to modify the experimental design and to control the alignment between the central axis of the target tube and the magnet configuration in a better way.

HEU measurements of holdup and recovered residue in the deactivation and decommission activities of the 321-M Reactor Fuel Fabrication Facility at the Savannah River Site

This paper contains a summary of the holdup and material control and accountability (MC&A) assays conducted for the determination of highly enriched uranium (HEU) in the deactivation and decommissioning (D&D) of the Reactor Fuel Fabrication Facility at the Savannah River Site (SRS). The facility was used to fabricate HEU fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the SRS production reactors. The facility operated for more than 35 years. During this time thousands of uranium-aluminum alloy (U-Al) production reactor fuel tubes were produced. After the facility ceased operations in 1995, all of the easily accessible U-Al was removed from the building, and only residual amounts remained. The bulk of this residue was located in the equipment that generated and handled small U-Al particles and in the exhaust systems for this equipment (e.g., chip compactor, casting furnaces, log saw, lathes A & B, cyclone separator, FreonOcart, riser crusher, …, etc). The D&D project is likely to represent an important example for D&D activities across SRS and across the Department of Energy weapons complex. The Savannah River National Laboratory was tasked to conduct holdup assays to quantify the amount of HEU on all components removed from the facility prior to placing in solid waste containers. The 235U holdup in any single component of process equipment must not exceed 50 g in order to meet the container limit. This limit was imposed to meet criticality requirements of the low level solid waste storage vaults. Thus, the holdup measurements were used as guidance to determine if further decontamination of equipment was needed to ensure that the quantity of 235U did not exceed the 50 g limit and to ensure that the waste met the Waste Acceptance Criteria (WAC) of the solid waste storage vaults. Since HEU is an accountable nuclear material, the holdupassays and assays of recovered residue were also important for material control and accountability purposes. In summary, the results of the holdup assays were essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to ensure that administrative criticality safety controls were not exceeded. This paper discusses theg-ray assay measurements conducted and the modeling of the acquired data to obtain measured holdup in process equipment, exhaust components, and fixed geometry scrap cans. It also presents development work required to model new acquisition configurations and to adapt available instrumentation to perform the assays.

D–D neutron generator development at LBNL

The plasma and ion source technology group in Lawrence Berkeley National Laboratory is developing advanced, next generation D–D neutron generators. There are three distinctive developments, which are discussed in this presentation, namely, multi-stage, accelerator-based axial neutron generator, high-output co-axial neutron generator and point source neutron generator. These generators employ RF-induction discharge to produce deuterium ions. The distinctive feature of RF-discharge is its capability to generate high atomic hydrogen species, high current densities and stable and long-life operation. The axial neutron generator is designed for applications that require fast pulsing together with medium to high D–D neutron output. The co-axial neutron generator is aimed for high neutron output with cw or pulsed operation, using either the D–D or D–T fusion reaction. The point source neutron generator is a new concept, utilizing a toroidal-shaped plasma generator. The beam is extracted from multiple apertures and focus to the target tube, which is located at the middle of the generator. This will generate a point source of D–D, T–T or D–T neutrons with high output flux. The latest development together with measured data will be discussed in this article.

Calculation of 237Np and 241Am detector calibration constants from first principles

The Analytical Development Section of Savannah River Technology Center (SRTC) was requested by the Facilities Disposition Projects (FDP) to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The results of the holdup assays are essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to meet criticality safety controls. This report covers calibration of the detectors in order to support holdup measurements in the C and D out-gassing ovens. These ovens were used to remove gas entrained in billet assembly material prior to the billets being extruded into rods by the extrusion press. A portable high purity germanium detection system was used to determine highly enriched uranium (HEU) holdup and to determine holdup of 235U, 237Np, and 241Am that were observed in these components. The detector system was run by an EG&G Dart™ system that contains the high voltage power supply and signal processing electronics. A personal computer with Gamma-Vision software was used to control the Dart™ MCA and provide space to store and manipulate multiple 4096-channel γ-ray spectra. The measured 237Np and 241Am contents were especially important in these components because their presence is unusual and unexpected in 321-M. It was important to obtain a measured value of these two components to disposition the out-gassing ovens and to determine whether a separate waste stream was necessary for release of these contaminated components to the E-Area Solid Waste Vault. This report presents determination of the calibration constants from first principles for determination of 241Am and 237Np using this detection system and compares the values obtained for 237Np with the calibration factors obtained with a subsequent measurement using a point source of radioactive equilibrium 237Np/233Pa.

Calculation of 237Np and 241Am detector calibration constants from first principles

The Analytical Development Section of Savannah River Technology Center (SRTC) was requested by the Facilities Disposition Projects (FDP) to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The results of the holdup assays are essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to meet criticality safety controls. This report covers calibration of the detectors in order to support holdup measurements in the C and D out-gassing ovens. These ovens were used to remove gas entrained in billet assembly material prior to the billets being extruded into rods by the extrusion press. A portable high purity germanium detection system was used to determine highly enriched uranium (HEU) holdup and to determine holdup of 235U, 237Np, and 241Am that were observed in these components. The detector system was run by an EG&G DartO system that contains the high voltage power supply and signal processing electronics. A personal computer with Gamma-Vision software was used to control the DartO MCA and provide space to store and manipulate multiple 4096-channel g-ray spectra. The measured 237Np and 241Am contents were especially important in these components because their presence is unusual and unexpected in 321-M. It was important to obtain a measured value of these two components to disposition the out-gassing ovens and to determine whether a separate waste stream was necessary for release of these contaminated components to the E-Area Solid Waste Vault. This report presents determination of the calibration constants from first principles for determination of 241Am and 237Np using this detection system and compares the values obtained for 237Np with the calibration factors obtained with a subsequent measurement using a point source of radioactive equilibrium 237Np/233Pa.

Hydrodynamics and steel tube wastage in a fluidized bed at elevated temperature

Hydrodynamic measurements were made in a bubbling fluidized bed operated at 550°C at three different excess gas velocities (0.15, 0.40 and 0.75 m/ s ). The bed has a cross-sectional area of 0.2 m×0.3 m with an immersed tube bank consisting of 59 horizontal stainless steel tubes (AISI 304L), 21 of which are exchangeable, thus allowing erosion studies. Capacitance probe analysis was used to determine the mean bubble rise velocity, the mean bubble frequency, the mean pierced bubble length, the mean bubble volume fraction and the mean visible bubble flow rate. Tube wastage was calculated from roundness profiles obtained by stylus profilometry. A redistribution of the bubble flow towards the center of the bed occurs when the excess gas velocity is increased. Measurements along a target tube, situated next to the capacitance probe, usually show greater material wastage at the central part of the tube, since the mean bubble rise velocity and the mean visible bubble flow rate are higher there. It is suggested that the greater material degradation is also an effect of the through-flow of a particle-transporting gas stream in the bubbles. With increasing height above the distributor plate the circumferential wastage profiles for the lowest excess gas velocity show a gradual change from an erosion pattern with one maximum (Type B behavior) to a pattern with two maxima (Type A behavior). Power spectral density distributions of the fluctuating pressure signals show that this is a result of the formation of larger bubbles, when the fluidization regime is changed in the upper part of the bed. At the highest excess gas velocity the bubble flow becomes more constrained due to a more rapid coalescence of the bubbles and the tubes show Type A wastage profiles throughout the bed.

Concept design of a new liquid metal target station for high power neutron scattering facilities

A new liquid metal target station without a window wall for high power charged particle beams to pass through is proposed for neutron-scattering sources and/or neutron-spallation sources. The beams are irradiated directly from above into the free surface of the liquid metal in a target tube soaked vertically in a reservoir tank of the liquid metal. A large hollow chamber is located above the target tube. This chamber works as a getter pump to evacuate the system and as a heat siphon to remove the heat fed by the beams, where the liquid metal works as the working liquid for both functions. Bismuth, Bi in the liquid state at temperatures above 300 °C, is chosen as the target medium. Experimental data for a cylindrical bismuth target are used to calculate the temperature distribution along the liquid metal target column. The evaporation rate of Bi atoms due to boiling under reduced pressure is calculated under a simple assumption in order to evaluate its activity as the working medium of a getter pump and a heat siphon.

A CdZnTe slot‐scanned detector for digital mammography

A new high-resolution detector has been developed for use in a slot-scanned digital mammography system. The detector is a hybrid device that consists of a CCD operating in time-delay integration mode that is bonded to a 150-microm-thick CdZnTe photoconductor array. The CCD was designed with a detector element pitch of 50 microm. Two devices were evaluated with differing crystalline quality. Incomplete charge collection was a source of reduction in DQE. This occurs in both devices due to characteristically low mobility-lifetime products for CdZnTe, with the greatest losses demonstrated by the multicrystalline sample. The mobility-lifetime products for the multicrystalline device were found to be 2.4 x 10(-4) and 4.0 x 10(-7) cm2/V for electrons and holes, respectively. The device constructed with higher quality single crystal CdZnTe demonstrated mobility-lifetime products of 1.0 x 10(-4) and 4.4 x 10(-6) cm2/V for electrons and holes. The MTF and DQE for the device were measured at several exposures and results were compared to predictions from a linear systems model of signal and noise propagation. The MTF at a spatial frequency of 10 mm(-1) exceeded 0.18 and 0.56 along the scan and slot directions, respectively. Scanning motion and CCD design limited the resolution along the scan direction. For an x-ray beam from a tungsten target tube with 40 microm molybdenum filtration operated at 26 kV, the single crystal device demonstrated a DQE(0) of 0.70 +/- 0.02 at 7.1 x 10(-6) C/kg (27 mR) exposure to the detector, despite its relatively poor charge collection efficiency.

YBa/sub 2/Cu/sub 3/O/sub 7-x/ sputter deposition from rotatable targets: a scalable approach for YBa/sub 2/Cu/sub 3/O/sub 7-x/ coated conductors

Worldwide research has been done on sputter deposition of YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO). In most cases, planar ceramic targets were used. Due to a lack of suitable target tubes, YBCO deposition from rotatable magnetrons was not yet explored. Rotatable magnetron sputter sources are however standard equipment in the large-scale sputter industry. Therefore, the development of sputter deposition from YBCO rotatable targets would facilitate the realization of a large-scale deposition process for YBCO coated conductor. Several problems encountered with sputter deposition of YBCO are related to the fact that the input power and the discharge voltage are too low. In a rotatable magnetron, the power input can be much higher compared to a planar magnetron with the same race-track area. By using flame sprayed target tubes, it was possible to demonstrate the possibilities of YBCO deposition from rotatable magnetrons. This research showed that an increased power input is indeed possible resulting in an increased deposition speed and improved discharge characteristics.

Filling and Recycling Apparatus of a Cyclotron Target with Enriched Krypton for Production of Radiopharmaceuticals

An apparatus for multiple filling of a cyclotron target with enriched Kr gas is described. The system is based on recycling pressurized gas by cryogenic pumping between the target tube and storage containers. The design and construction makes use of previous experience in the construction and operation of two analogue apparatuses for Xe124 high pressure gas targets, but major modifications have been incorporated, evoked by the different physical properties of Kr, by the character of the nuclear reaction, and by the demand for automation from the side of the end user.

Enhancing the ratio of fluorescence to bremsstrahlung radiation in X-ray tube spectra

This paper describes techniques that can be used to improve the ratio of fluorescence to bremsstrahlung radiation ( F/ B) in X-ray tube spectra. Firstly, an extension of the EGS4 code system is used to evaluate the impact of the substrate in thin target applications, in terms of the yield of bremsstrahlung photons produced. The choice of materials to filter X-ray tube spectra, and its effect in the F/ B and the tube efficiency is discussed. The characteristics of spectra produced in transmission tubes with different target thicknesses, substrates and tube voltages are also presented.

Preparation of a beam quality indicator for effective energy determinations of continuum beams: establishment of traceability

A new beam quality indicator (BQI) was designed and fabricated to determine effective energies of beams extracted from neutron radiography facilities. Performances of the five new BQIs were compared with the original BQI which was recently proposed and tested by various beams. Non-filtered thermal neutrons, filtered thermal neutrons, and cold neutrons from a guide tube were used in the performance test program. The new BQIs were also examined by four different detection systems using a combination of a Gd converter and a X-ray film, a neutron imaging plate, a cooled charge coupled device camera, and a silicon intensified target tube camera.

Visualization and measurement of refrigerant flow in compression-type refrigerator by neutron radiography

The refrigerant two-phase flows in a capillary tube and a distributor used in a compression-type refrigerator were visualized by real-time neutron radiography. The thermal neutron radiography system of JRR-3M at the Japan Atomic Energy Research Institute was used. In the visualization experiments of the two-phase flow in the capillary tube of 2 mm I.D., a cooled CCD camera was used, and the axial one-dimensional distributions of void fraction were measured. For the distributor, a high sensitivity video camera with a silicone intensified target tube was used. From the visualized images, the refrigerant behaviors in the distributor were clearly shown, and the liquid fraction in each tube was measured. As a result, it was shown that the refrigerant behaviors in the distributor effected the distributing performance of the refrigerant flow.

Calculation of x-ray tube spectral distributions

Two approaches to the calculation of x-ray tube spectral distributions for x-ray fluorescence analysis are compared. One of them is the NIST algorithm based both on Kramers' law for the continuum intensity and a semi-empirical ratio between the characteristic lines and the continuum intensity. In the other, the continuum and characteristic spectra are calculated separately just as it is done in electron microprobe analysis. Some improvements concerned with the description of the shape of the continuum spectrum at long wavelength and correction for fluorescence excited by the bremsstrahlung spectrum are proposed. The calculations of the continuum intensity and the relationship between the integral continuum and the characteristic line intensities were compared with literature experimental data for Cr, Rh, W, Cu and Mo target tubes. Some estimations of the absolute intensities of x-ray tube spectra are also shown. Copyright © 1999 John Wiley & Sons, Ltd.

In vivo rat closed spinal window for spinal microcirculation: observation of pial vessels, leukocyte adhesion, and red blood cell velocity.

An in vivo closed spinal window technique in rats was designed for observing the spinal microcirculation, such as the change of vessel diameter, leukocyte adhesion, and red blood cell (RBC) velocity, which has been very rarely examined in vivo in the spinal cord. We made a very precise closed spinal window with a laminectomy at the C5 level using a dental acrylic resin and a cover glass (7 mm in diameter). Through this closed window, the dorsal surface of the rat cervical cord was observed with a video microscope, and the fluorescent images of rhodamine 6G-labeled leukocytes and fluorescein isothiocyanate-labeled RBCs were recorded and analyzed with a silicon-intensified target tube camera (30 frames/s) and an image-intensified high-speed video camera system (1000 frames/s). During CO2 inhalation, the pial arterioles responded with vasodilation of 12.4+/-10.4% (P<0.01) in 11 arterioles of seven rats. The adhering leukocytes significantly increased in 41 venular segments of seven rats after superfusion of the neutrophil chemoattractant, N-formyl-methionine-leucine-phenylalanine solution for 15 minutes (P<0.001) but not after superfusion of only artificial cerebrospinal fluid for 15 minutes. During these experiments, no adhering leukocyte was seen in the pial arterioles. Fluorescein isothiocyanate-labeled RBCs look like shooting stars in arterioles with silicon-intensified target tube camera processing at 30 frames per second, but individual fluorescein isothiocyanate-labeled RBCs could be recognized frame by frame with the image-intensified high-speed video camera system. In 13 arterioles of four rats, the RBC velocity was 5.3+/-2.0 mm per second. This closed spinal window technique in rats is available and applicable for the study of the spinal microcirculation, such as the pathophysiology of a secondary injury.

Development of a transported coaxial ECR plasma source for inner coating of metallic tubes

An inner coating system using transported coaxial ECR plasma has been developed. ECR plasmas were generated inside a coaxial tube and were transported along the tube axis using the control system for an applied magnetic field which consists of a computer, switching regulator and five solenoid coils. The microwave was introduced into the coaxial tube, which was composed of target (center conductor) and substrate tube (outer conductor), in the TEM mode that has no cut-off wavelength. Electron temperature and density were measured by using several Langmuir probes and the characteristics of discharge were also investigated at various pressures, microwave powers and magnetic flux densities.