Converter Plate Research Articles

A INTERNET DAS COISAS EM SISTEMAS DE GERAÇÃO FOTOVOLTAICA

This article presents a proposal for applying the Internet of Things to monitoring photovoltaic generation. Data acquisition and transmission in the plant are performed by routines performed by a microcontroller where measures such as solar radiation intensity, temperature, humidity, electrical voltage and electrical current are verified, aiming at fault diagnosis. Through cloud computing, Internet of Things platforms and dedicated interfaces, data is processed, stored and made available in real time, with ample capacity and mobility, allowing for remote monitoring of the system. The system is implemented on an experimental bench, acquiring data from converter plates used in energy conformation and manufactured with open architecture, serving panels with a capacity of 130 Wp.

Bremsstrahlung Generation by 7.5 Mev Electrons in Converters Made of Different Materials

The present paper shows that, besides the technologically complex water-cooled converters made of Ta or W, a simple and efficient converter in the form of air-cooled Mo and Al plates can be fabricated for a number of tasks. The generation of bremsstrahlung by electrons with the energy of 7.5 MeV in the converter plates made of Ta, W, Cu or Mo and in the Al filter was studied by the Monte Carlo method in the PENELOPE software package. The thicknesses range of the plates made of Ta, W, Cu or Mo was chosen on condition that the total mass thickness of the converter and filter made of Al (in g/mm2) provided complete absorption of the primary electrons. It is shown that the photon yields from Mo at mass thicknesses above 25 g/mm2 are higher than those from Ta and W, but the energy transferred from electrons to BS is lower. With the same mass thicknesses of Ta and W converters, practically all characteristics of bremsstrahlung and the absorbed energy in the target are the same. The conditions for cooling the converter elements with water and air are determined for the level of heat release in the converter up to 10 kW. The minimum dimensions of the electron-irradiated region of Ta and Mo converters, cooled by water, are determined. It is shown that with the really existing air compressors taken into account, the permissible heat release of air-cooled Mo converters should not exceed 4 kW.

Three-dimensional repositioning accuracy of semiadjustable articulator cast mounting systems

In spite of its importance in prosthesis precision and quality, the 3-dimensional repositioning accuracy of cast mounting systems has not been reported in detail. The purpose of this study was to quantify the 3-dimensional repositioning accuracy of 6 selected cast mounting systems. Five magnetic mounting systems were compared with a conventional screw-on system. Six systems on 3 semiadjustable articulators were evaluated: Denar Mark II with conventional screw-on mounting plates (DENSCR) and magnetic mounting system with converter plates (DENCON); Denar Mark 330 with in-built magnetic mounting system (DENMAG) and disposable mounting plates; and Artex CP with blue (ARTBLU), white (ARTWHI), and black (ARTBLA) magnetic mounting plates. Test casts with 3 high-precision ceramic ball bearings at the mandibular central incisor (Point I) and the right and left second molar (Point R; Point L) positions were mounted on 5 mounting plates (n=5) for all 6 systems. Each cast was repositioned 10 times by 4 operators in random order. Nine linear (Ix, Iy, Iz; Rx, Ry, Rz; Lx, Ly, Lz) and 3 angular (anteroposterior, mediolateral, twisting) displacements were measured with a coordinate measuring machine. The mean standard deviations of the linear and angular displacements defined repositioning accuracy. Anteroposterior linear repositioning accuracy ranged from 23.8 ±3.7 μm (DENCON) to 4.9 ±3.2 μm (DENSCR). Mediolateral linear repositioning accuracy ranged from 46.0 ±8.0 μm (DENCON) to 3.7 ±1.5 μm (ARTBLU), and vertical linear repositioning accuracy ranged from 7.2 ±9.6 μm (DENMAG) to 1.5 ±0.9 μm (ARTBLU). Anteroposterior angular repositioning accuracy ranged from 0.0084 ±0.0080 degrees (DENCON) to 0.0020 ±0.0006 degrees (ARTBLU), and mediolateral angular repositioning accuracy ranged from 0.0120 ±0.0111 degrees (ARTWHI) to 0.0027 ±0.0008 degrees (ARTBLU). Twisting angular repositioning accuracy ranged from 0.0419 ±0.0176 degrees (DENCON) to 0.0042 ±0.0038 degrees (ARTBLA). One-way ANOVA found significant differences (P<.05) among all systems for Iy, Ry, Lx, Ly, and twisting. Generally, vertical linear displacements were less likely to reach the threshold of clinical detectability compared with anteroposterior or mediolateral linear displacements. The overall repositioning accuracy of DENSCR was comparable with 4 magnetic mounting systems (DENMAG, ARTBLU, ARTWHI, ARTBLA). DENCON exhibited the worst repositioning accuracy for Iy, Ry, Lx, Ly, and twisting.

Development of a High-performance Optical System and Fluorescent Converters for High-resolution Neutron Imaging

Abstract Two novel devices for use in neutron imaging technique are introduced. The first one is a high-performance optical lens for video camera systems. The lens system has a magnification of 1:1 and an F value of 3. The optical resolution is less than 5 μm. The second device is a high-resolution fluorescent plate that converts neutrons into visible light. The fluorescent converter material consists of a mixture of 6 LiF and ZnS(Ag) fine powder, and the thickness of the converter is material is as little as 15 μm. The surface of the plate is coated with a 1 μm-thick gadolinium oxide layer. This layer is optically transparent and acts as an electron emitter for neutron detection. Our preliminary results show that the developed optical lens and fluorescent converter plates are very promising for high-resolution neutron imaging.

Prototyping a 2m × 0.5m MRPC-based neutron TOF-wall with steel converter plates

A 2 m × 0.5 m large prototype of an MRPC-based (Multi-gap Resistive Plate Chamber) neutron Time-Of-Flight-wall for detecting relativistic neutrons in an energy range from 200 MeV to 1 GeV was successfully designed and realized. It consists of steel plates which convert neutrons via hadronic interactions into charged particles, followed by a 2 × 2 gap MRPC-structure to detect the charged particles. Tests were carried out using 30 MeV electrons with an energy close to the minimum of ionization in order to study the properties of the prototype achieving an efficiency larger than 90 % and a time resolution σt better than 100 ps. For units with an active area of 40 cm × 20 cm and otherwise the same design, quasi-monochromatic neutrons with a peak energy of 175 MeV were utilized to study their response to relativistic neutrons. Detailed Monte Carlo simulations were performed both for the small and for the large modules to simulate their properties to both neutrons and electrons and to study the performance of the final neutron detector assembly with an area of 2 m × 2 m for single-neutron and multi-neutron events.

Absolute detection efficiencies of an ion-counting system with a channel-electron multiplier

Absolute detection efficiencies of an ion-counting system have been examined for Li+, Rb+, Cs+, Ar+, and Ar2+ ions as a function of the incident ion-impact energy. The ion-counting system consists of a converter plate (SUS), an electrostatic-lens system, and a channel-type secondary-electron-multiplier. For all ions examined in this study, the detection efficiencies are about unity if the ion energy is greater than 5 keV. The charge-state dependence is not as high for Ar+ and Ar2+.

The munich fission neutron therapy facility MEDAPP at the research reactor FRM II

At the new research reactor FRM II of the Technical University of Munich (TUM), the facility for Medical Applications (MEDAPP) was installed where fast neutrons are available as a beam for medical use. Thermal neutrons induce fission in a pair of uranium converter plates and generate fast neutrons which are guided to the patient by a beam tube. The maximum opening of the multi leaf collimator (MLC) is 30x20 cm2 WxH. The beam is characterized by neutron-photon mixed beam phantom dosimetry. Specific safety measures are outlined. The neutron and gamma dose rates are 0.52 Gy/min and 0.20 Gy/min, respectively, in 2 cm depth of a water phantom. The half maximum depth of the neutron dose rate in water is 5.4 cm (mean neutron energy 1.9+/-0.1 MeV). Conformity with the European Medical Devices Directive (MDD) 93/42/EEG, was proven so that MEDAPP has a CE mark and since February 2007 also the license for clinical operation. The clinical neutron irradiations of malignant tumors, which were performed at the former research reactor FRM until 2000, can be continued at FRM II under improved conditions. First patients were irradiated in June 2007.

Results from In-Situ, Real-Time SEM Observations of Grain Growth in Polycrystalline Metal

The development of the converter plate detector has allowed the generation of real-time, in-situ image sequences of evolving microstructures in model and industrial polycrystalline metals. The principal metals investigated were steel, aluminium and gold. The raw video results allow a number of qualitative statements to be made about grain growth behaviour in these systems and some simplistic quantitative statements. However, the sheer volume and variety of data available in the time-stream of micrographs presents its own problems in identifying and extracting the information most useful for rigorous characterisation of the behaviour of a dynamically evolving microstructure. We present and discuss our approach to the analysis of this data and results of that analysis.

A Technique for Real-Time, In-Situ SEM Observation of Grain Growth at Elevated Temperatures

We present a novel electron detector and technique permitting orientation contrast images to be generated using back-scattered electron signals. The detector is a modification of the converter plate. It is unaffected by Infra-Red and light photons and invulnerable to the effects of heat. Consequently, the detector is removed as the temperature limiting factor in elevated temperature SEM grain observations. The detector has been successfully applied to an environmental SEM (ESEM) operating in high vacuum mode and has produced good quality video image sequences of hot metal specimens with frame rates between 1 per second and 1 per 30 seconds (largely material dependent). Temperatures attained were up to 850°C, limited by the capability of the hot stage. Although developed for the ESEM the technique is applicable to any SEM provided that adequate measures are taken to manage contamination and heat effects on other microscope components. We have produced images and short, accelerated video sequences of recrystallisation and grain growth phenomena in steel, aluminium, copper and gold by the new technique. The technique has also successfully imaged phase transformations and high temperature behaviour of microelectronic materials.

Field emission photocathode array for multibeam electron lithography

The application of an array of individually light switched cold field emitters in electron beam lithography is described. In the 1970s, extensive investigations of the field emission photocathode were performed [IEEE Trans. Electron Dev. ED-21 (1974) 785]. The emission of these emitters is much more stable than conventional cold field emitters. Quantum efficiencies of more than 1 electron per photon have been observed, which is high compared to normal photo emitters. Another advantage compared to photo emitters is that small sources can be made, without limiting the photon detection area. These properties make the Field Emission Photocathode Array a powerful device for multibeam electron lithography. It can be used as a modulated electron source as well as a continuous electron source. In the Multiple Aperture Pixel by Pixel Enhancement of Resolution, or MAPPER, concept the array can be used as a converter plate. The light sensitivity of the emitters is such that a few tens of milliwatts LASER power should be sufficient to obtain a throughput of 60 wafers per hour.

A study of the use of flat‐panel imagers for radiotherapy verification (in English)

This thesis investigates the feasibility of the application of flat‐panel imagers (FPIs) based on amorphous silicon to radiotherapy verification. Intensity modulated radiotherapy imposes new demands on verification procedures. A contrast resolution of 1% may be required from portal imaging systems to resolve the target structure and the organs at risk (OAR). Furthermore a spatial resolution of 1 mm is desired. The imaging characteristics, spatial resolution, efficiency, and noise characteristics of the FPI for megavoltage imaging were investigated regarding these demands. Possible improvements from scatter rejection by a modified detector design were investigated by simulating the spectral response of the converter plates of these detectors to photons of different energies and the response to scattered photons. Since low contrast objects like the target structure and the OAR can be detected in radiographic transmission images only for some rare cases, tomographical imaging was tested for position verification. This was also done using an FPI and the megavoltage (MV) source of the treatment accelerator. A different approach to position verification is the integration of kilovoltage (kV) computed tomography (CT) into a clinical linear accelerator. Although this approach has higher demands on the hardware side, it will deliver higher contrast images at a lower dose. A comparison of MVCT and kVCT and an outlook to new possibilities using integrated CT therefore completes this thesis.

High throughput electron lithography with the multiple aperture pixel by pixel enhancement of resolution concept

A new lithography concept for the sub-100 nm generations is proposed. The bulk of the machine is a traditional deep ultraviolet demagnification scanner–stepper. The mask is illuminated by 106–108 almost diffraction limited subbeams formed by a microlens array. After demagnification these subbeams are focused on a photon–electron converter plate. Each photon subbeam triggers the emission of a narrow beam of electrons. The electron beams are focused individually on the wafer, which is at a distance of about 1 mm from the converter plate. By scanning both mask and wafer through the many beams, the whole wafer is exposed.

The CPLEAR electromagnetic calorimeter

A large-acceptance lead/gas sampling electromagnetic calorimeter (ECAL) was constructed for the CPLEAR experiment to detect photons from decays of π 0s with momentum p π 0 ≤ 800 MeV/ c. The main purpose of the ECAL is to determine the decay vertex of neutral-kaon decays K 0 → π 0π 0 → 4γ and K 0 → π 0π 0π 0 → 6γ. This requires a position-sensitive photon detector with high spatial granularity in r−, ϕ−, and z−coordinates. The ECAL - a barrel without end-caps located inside a magnetic field of 0.44 T - consists of 18 identical concentric layers. Each layer of 1 3 radiation length ( X 0) contains a converter plate followed by small cross-section high-gain tubes of 2640 mm active length which are sandwiched by passive pick-up strip plates. The ECAL, with a total of 6 X 0 has an energy resolution of α(E) E ≈ 13% (E( GeV) and a position resolution of 4.5 mm for the shower foot. The shower topology allows separation of electrons from pions. The design, construction, read-out electronics, and performance of the detector are described.

Clinical dosimetry of an epithermal neutron beam for neutron capture therapy: Dose distributions under reference conditions

The aim of this study was to asses the dose distribution under reference conditions for the various dose components of the Petten clinical epithermal neutron beam for boron neutron capture therapy (BNCT). Activation foils and a silicon alpha-particle detector with a 6Li converter plate have been used for the determination of the thermal neutron fluence rate. The gamma-ray dose rate and the fast neutron dose rate have been determined using paired ionization chambers. Circular beam apertures of 8, 12 and 15 cm diameters have been investigated using a 15 x 15 x 15 cm3 solid polymethyl-methacrylate phantom, a water phantom of the same dimensions and a 30 x 30 x 30 cm3 water phantom at various phantom to beam-exit distances. The effect of phantom to beam-exit distance could be modeled using an inverse square law with a virtual source to beam-exit distance of 3.0 m. At a reference phantom to beam-exit distance of 30 cm, three-dimensional dose and fluence distributions of the various dose components have been determined in the phantoms. The absolute thermal neutron fluence rate at a reference depth of 2 cm in the 15 cm water phantom increased by 43% when the field size was increased from 8 to 15 cm. Simultaneously the gamma-ray dose rate increased by 46% while the fast neutron dose rate increased by only 5%. A reference treatment position at 30 cm from the beam exit allows convenient patient positioning with a relatively small increase in irradiation time compared to positions very close to the beam-exit. A more homogeneous distribution of thermal neutrons over a target volume, a higher absolute thermal neutron fluence rate and a lower contribution of the fast neutron dose to the total dose will result in improved treatment plans when using a 12 cm or 15 cm field compared to a 8 cm field. The dose distributions will be used as benchmark data for treatment planning systems for BNCT.

Liquid argon calorimetry with LHC-performance specifications

A novel geometry liquid argon calorimeter with accordion-shaped electrodes and converter plates has been recently conceived. Such a design allows for a fast readout and for a high granularity over large volumes with minimal dead spaces, properties which are considered essential for operation at the future hadron colliders. The first electromagnetic prototype based on this scheme has been built and tested at the CERN SPS. For a response peaking time of 140 ns an energy resolution of 10%/√ E(GeV) and a space resolution of 4.4 mm/√ E(GeV) with 2.7 cm cell size were achieved for electrons. A few preliminary results from a test with fast readout (response peaking time of less than 40 ns) are also presented.

Microdosimetric Spectra Measurements of Janus Neutrons

Neutron radiation from the JANUS reactor at Argonne National Laboratory is being used with increasing frequency for major biological experiments. The fast neutron spectrum has a Kerma-weighted mean energy of 0.8 MeV and low gamma-ray contamination. In 1984 the JANUS fission converter plate of highly enriched uranium was replaced by one made of low-enriched uranium. We recorded microdosimetric spectra at several different positions in the high-flux irradiation room of JANUS before the change of the converter plate. Each set of measurements consisted of spectra taken at three different site diameters (0.5, 1.0, and 5.0 ..mu..m) and in both ''attenuator up'' and ''attenuator down'' configurations. At two conventional dosimetry reference positions, two sets of measurements were recorded. At three biological reference positions, measurements simulating several biological irradiation conditions, were taken. The dose rate at each position was estimated and compared with dose rates obtained previously by conventional dosimetry. Comparison of the different measurements showed no major change in spectra as a function of position or irradiation condition. First results from similar sets of measurements recorded after the installment of the new converter plate indicate no major change in the spectra. 11 refs., 4 figs., 5 tabs.

Microdosimetric Spectra Measurements of Janus Neutrons

Neutron radiation from the JANUS reactor at Argonne National Laboratory is being used with increasing frequency for major biological experiments. The fast neutron spectrum has a Kerma-weighted mean energy of 0.8 MeV and low gamma-ray contamination. In 1984 the JANUS fission converter plate of highly enriched uranium was replaced by one made of low-enriched uranium. We recorded microdosimetric spectra at several different positions in the high-flux irradiation room of JANUS before the change of the converter plate. Each set of measurements consisted of spectra taken at three different site diameters (0.5, 1.0, and 5.0 ..mu..m) and in both ''attenuator up'' and ''attenuator down'' configurations. At two conventional dosimetry reference positions, two sets of measurements were recorded. At three biological reference positions, measurements simulating several biological irradiation conditions, were taken. The dose rate at each position was estimated and compared with dose rates obtained previously by conventional dosimetry. Comparison of the different measurements showed no major change in spectra as a function of position or irradiation condition. First results from similar sets of measurements recorded after the installment of the new converter plate indicate no major change in the spectra. 11 refs., 4 figs., 5 tabs.

An Alpha Particle Diagnostic Beam Line System to Generate an Intense Li0Beam with an ORNL SITEX Source

The Oak Ridge National Laboratory (ORNL) SITEX (Surface Ionization with Transverse Extraction) negative ion source utilizes a 100-V/20-A reflex arc discharge in a 1300-gauss magnetic field to generate Cs+ ions and H+ or D+ ions, depending on the beam required. A shaped molybdenum plate is placed directly behind the arc column. Cesium coverage on this plate is used to minimize the surface work function, which requires two-thirds of a monolayer coverage. Cesium coverage ia adjusted both by cesium flow control into the arc discharge chamber and by temperature control of the converter using gaseous-helium cooling channels in the converter plate. Normal converter operational temperatures are 300/sup 0/ to 500/sup 0/C H/sup -//D/sup -/ beams are generated at the biased converter surface (-150 V with respect to the anode) by Cs/sup +/ sputtering of absorbed hydrogen or deuterium and by the reflection-conversion mechanism of H/sup +//D/sup +/ ions which strike the converter surface at 150 eV. The negative ions are accelerated through the 150-V plasma sheath at the converter surface and are focused by the converter geometry and magnetic field so as to pass through the exit aperture with minimum angular divergence. The ion optics of the SITEX accelerator has beenmore » calculated using the ORNL 3-D optics code and results in a divergence perpendicular to the slot of theta/sub perpendicular rms/ = 0.35/sup 0/ and parallel to the slot of theta/sub parallel rms/ = 0.18/sup 0/. This beam divergence should be adequate for injection into a radio frequency quadrupole (RFQ) for further acceleration.« less

Plasma Radius Control System for Tandem Mirrors

The operation of a tandem mirror reactor (TMR) at fractions of full power is an important part of the power plant operation. It has been shown that fractional power operation can best be achieved by controlling the plasma radius, leaving the rest of plasma parameters unchanged. The physics of magnetic confinement in a TMR can be used to design the desired radius control (RC) system. It is proposed to bias the field lines through the ends of a tandem mirror device and control the radial electric field in order to guard against rotational instabilities and ensure nonstochastic radial transport. In this scheme, plasma on the unbiased field lines suffers rapid transport and is lost. As such, the potential control of the direct converter plates as well as the location of the grounded halo dumps requires the flux tube containing the core plasma to match the direct converter area at all times. Based on this effect, an RC system can be devised that uses the conservation of the magnetic flux to adjust the field near the direct converter such that a flux tube with a smaller radius in the device matches the direct converter. Field lines outside this flux tube aremore » not properly biased and cannot support core plasma. A practical design of such an RC system for the Mirror Advanced Reactor Study conceptual TMR is presented. The power consumption by the RC coil system is modest and no engineering difficulty in the design and construction of such a system is expected. Utilization of such an RC system in advanced tandem mirror experiments can also be of great use in the study of such various phenomena as radial transport, control of the radial electric field, halo plasma production, radio-frequency absorption, etc.« less

High-resolution low-cost photon detectors for large assemblies

Prototype modules for a multicell system of shower detectors, detectiong electrons or photons and measuring their energy, have been studied in the 0.25–10 GeV range. Each cell is made of a sandwich of thin layers of lead and scintillator, the produced light being extracted by acrylic rods or plates doped with a wavelength shifter (BBQ). Extensive tests led to a simple, low-cost and compact module using two extraction plates and allowing measurement of energy ( σ E ⋍ 9% E 1 2 ) and position ( σ⋍15 mm ) of the electromagnetic shower. A system of square cells seen by four converter plates is proposed for a CERN SPS experiment.