Extraction Grid Research Articles

ITER-HNB plasma and extraction grids in BUG: Characterization of magnetic deflection correction

The BATMAN Upgrade test facility aims to extract H-/D- at high current densities. The inevitably co-extracted electrons are deflected out of the beamlet by permanent magnets before acceleration. These magnets induce a row-wise zig-zag deflection of the beamlets. In the new MITICA-like extraction system, this deflection is compensated by additional deflection correction magnets. IBSimu modeling studies indicate that the deflection correction system not only acts on the horizontal beamlet deflection, but also causes aberrations to the vertical angular distribution. Dependencies of the beamlet position and size are studied in several parameter scans with the available diagnostic tools (CFC tile calorimetry, Beam Emission Spectroscopy). The horizontal beamlet deflection is robustly compensated within the systematic uncertainty of the experiment. The triangular beamlet shape predicted on basis of the magnetic field structure is visible in the CFC calorimetry.

Difference of co-extracted electron current and beam acceleration in a negative ion source with hydrogen-isotope ions

Improvement of the performance on a hydrogen/deuterium negative ion source for a nuclear fusion device is reported. In particular, the suppression of the co-extracted electron current, Ie, is an important issue to ensure the stable beam acceleration. Improvement of the Ie has been confirmed by optimizing the magnetic field of the electron deflection magnet in the extraction grid. Two other new methods for reduction of the Ie were validated. The first was an electron fence whose rods were set between the rows of apertures on a plasma grid. The electron and negative ion current ratio, approximately Ie/I acc, was greatly improved from 0.7 to 0.25 in deuterium. The second was an outer iron yoke which enhanced the magnetic flux density 19% inside the arc discharge chamber. The Ie/Iacc using the outer yoke decreased by 0.1 compared with using a normal magnetic filter in a deuterium operation. These attempts have improved the total deuterium injection beam power of 8.4 MW by three negative ion based NBIs.

Comparison of ion source plasma responses to extraction grid bias between hydrogen and deuterium operations in NIFS-RNIS

An isotope effect of negative ion motion in plasma near a plasma grid (PG), which is a plasma-beam boundary grid, has been investigated in a negative hydrogen-ion source with the surface production process of the negative ion on the PG surface. Negative deuterium-ion (D-) density was higher than negative hydrogen-ion (H-) density in the condition without extraction-grid bias (V egb) and approached the H- density in the condition with V egb. Thus, the D- density responded stronger than the H- density to the V egb. The density of the negative hydrogen-ion isotopes and the density response to the V egb have been organized into respective identical trends by momenta of isotopes emitting from the PG. The Larmor motion can be a dominant mechanism of the negative ion transport from the PG to the plasma.

Sexual health promotion messages for young people in Netflix most-watched series content (2015–2020): mixed-methods analysis study

IntroductionSexual health is a major issue for young people, and there is a need to promote it. Sexual health promotion messages may be included in Netflix series that are widely...

Recognition of rice seedling rows based on row vector grid classification

Recognition of rice seedling rows under machine operation is affected by many factors such as light conditions, duckweed, weeds, and blur caused by machine vibration. Recognition of rice seedling rows is a challenging research problem for mechanized rice weeding. This paper proposed a novel and fast rice seedling row recognition method based on row vector grid classification. This method builds an end-to-end CNN model composed of seedling feature extraction and row vector grid classification, which converts seedling row recognition into a grid classification problem based on row vectors using global feature. Our method can significantly reduce the computational cost through the selection based on row vectors, and can reach a running speed close to 170 fps at an image resolution of 800*288; the loss function of the proposed CNN model is modeled based on the two prior constraints including the continuity between the row vectors of the seedling row and the shape of the seedling row. The proposed method for recognizing rice seedling rows was tested on a test set composed of normal conditions, duckweed, weeds, and vibration blur scenes. The test results showed that the proposed CNN model reached an F1 score of 89.22% and a running speed of 170 fps with an image resolution of 800*288.

Prognostic factors for persistent symptoms in adults with mild traumatic brain injury: protocol for an overview of systematic reviews

BackgroundMild traumatic brain injury (mTBI) is an increasing public health problem that can lead to persistent symptoms that have several functional consequences. Understanding the prognosis of a condition is an important component of clinical decision-making and can help guide the prevention of long-term disabilities of patients with mTBI. Several studies and systematic reviews have been conducted in order to understand prognosis of chronic symptoms following mTBI. We aim to synthesize evidence from systematic reviews on factors that affect the risk of persistent symptoms in mTBI-affected adults.MethodsWe will conduct an overview of systematic reviews following steps described in the Cochrane Handbook. We will search in Cochrane, Medline, CINAHL, Embase, PsycINFO, and Epistemonikos for systematic reviews about the prognosis of persistent symptoms following mTBI in the adult population. Two reviewers will independently screen all references and then select eligible reviews based on eligibility criteria. A data extraction grid will be used to extract relevant information. The risk of bias in the included reviews will be assessed using the ROBIS tool. Data will be synthesized into a comprehensive conceptual model in order to have a better understanding of the predictive factors of post-concussion symptoms following mTBI.DiscussionResults will help multiple stakeholders, such as clinicians and rehabilitation program managers, to understand the prognosis of long-term consequences following mTBI. It could guide stakeholders to recognize their patients’ prognostic factors and to invest their time and resources in patients who need it the most.Systematic review registrationPROSPERO CRD42020176676.

Computational design of magnetic beamlet deflection correction for NNBI

Coextracted electrons are inevitable for negative ion based NBI systems. To avoid wastefully accelerating these electrons to the full energy, they are magnetically deflected out of the beamlet onto the extraction grid. The deflection of the electrons creates an unwanted deflection of the ions, which is magnetically corrected in the ITER heating neutral beam. In order to gain experience with magnetic deflection correction, IPP has designed a magnetic deflection correction system in collaboration with the ITER organization, which will be characterized in the BATMAN Upgrade test facility. The ion-optics code IBSimu is used for the design of the magnetic deflection correction system. A comparison of the design candidates shows that the magnetic deflection correction system inherently leads to an increased divergence as result of the magnetic field structure. The divergence increase manifests itself as an increased fraction of a broader halo component.

Silicon Field Emission Electron Source With Individually Controllable Single Emitters

An electron source with an array of individually controllable single tips allows the observation of each emitter current simultaneously as well as the measurement of the integral current. Furthermore, the initial activation process of the individual tips and current distribution of the source can be examined. The Si cathode consists of an array of 2×2 conically shaped emitter structures on a borosilicate glass substrate. The emitters were fabricated by laser micromachining and wet etching. Integral field emission (FE) measurements were performed in a diode configuration in a vacuum chamber at pressures of about 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> mbar with a self-aligned Si extraction grid, due to adjustment pins. The total emission current was regulated to a predefined value (4.0, 10, 20, 40, and 50 μA) by an external regulating circuit and recorded individually during the measurement. The onset voltage for a current of 1 nA varied between 320 and 430 V. The voltage conversion factor is in the range of 7.6×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> to 1.3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . Constant current measurements over a longer period of time (1800 values with a sample rate of 0.5 Hz) were performed and show a total current fluctuation less than 0.6% due to the regulation circuit. Despite the stable total current in regulated operation, it was observed that the individual emitters fluctuate up to 75% for low (~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> A) and 5% for high (~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> A) currents.

The engineering design of quarter size negative beam source for the comprehensive research facility for fusion technology

A high-power radio frequency (RF) beam source is a key component for Negative Neutral Beam Injector (NNBI) in ASIPP. According to the technical route planning of CRAFT-NNBI beam source project, ASIPP started the development of quarter-size RF negative source and corresponding test facility. The inner diameter of the faraday shield (FS) of RF driver is 240 mm, the outer diameter of the accelerator is 1 m, with three-layer grids extraction system, which comprises the plasma grid (PG), extraction grid (EG) and ground grid (GG). The size of PG is 512 mm × 396 mm × 9 mm, with two rows of 16 × 6 apertures made of pure molybdenum. The structure design of RF negative beam source and the manufacturing process of key components are presented, with emphasis on the manufacturing process of FS as well as grids. Furthermore, the fluid-thermal-structural analysis of PG, the mechanical analysis and material bonding strength test of the main insulation structure of beam source, as well as the preliminary layout of the latest test facility are presented.

Tetanus vaccine coverage in recommended and more than recommended doses among mothers in a West Cameroon health district: a cross sectional study

Background: Vaccination is the best way to protect newborns and mothers against tetanus. The number of doses of Td vaccine recommended by the Expanded Program of Immunization is based on documented protective immune response. During this decade, the Foumban Health District (FHD) was the seat of an epidemic despite the satisfactory administrative immunization coverage. This study was conducted in 2019 in the FHD to assess tetanus vaccine coverage among mothers for their last pregnancy and the cumulative number of vaccine doses administered to the mothers. Method: This was a descriptive cross-sectional study conducted in the FHD in 2019. Mothers living in the district with at least one child younger than five years were included and were selected by random stratified cluster sampling. Trained surveyors used a face-to-face questionnaire, data extraction grid and data-tracking grid to review and collect data from antenatal care booklets, vaccination cards and the women’s own reports of immunization. The immunization coverage per vaccine dose and vaccination completeness rate were estimated. Results: From 621 women visited, 602 (96.9%) responded. A total of 176/511 women (34.4%) had evidence of vaccination. For the last pregnancy, the two-dose immunization proportion was 21.7% (111/511) for documented coverage and 47.6% (243/511) for undocumented coverage. 306/570 women (53.7%) had received more than the recommended five doses necessary for lifetime protection. The recruitment, two and five doses completeness rates were 99.9% (569/570), 95.8% (546/570) and 65.3% (372/570), respectively. Conclusion: More than half of mothers received more doses of tetanus toxoid vaccine than necessary in FHD. This increased the resources needed and the cost of vaccination. Health personnel should be trained and supervised to assess pregnant women’s vaccination status before planning the number of vaccine doses to be administered during pregnancy.

Conceptual design of a beam source for negative neutral beam injector of CRAFT facility

The Comprehensive Research Facility for Fusion Technology (CRAFT) is a large scientific device that is preferentially deployed in China's "Thirteenth Five-Year Plan" for the construction of major national science and technology infrastructures. A beam source of negative neutral beam injector (NNBI) is required for the CRAFT device with the beam energy of 400 keV, neutral beam power of 2 MW, and beam duration of 100 s. The beam source is the key component of NNBI system. A radio frequency (RF) based negative beam source was designed for the CRAFT NNBI system. It contains a large plasma generator and a negative ion accelerator. The plasma generator contains a large expansion chamber and four RF drivers which arrange in a vertical column (1 × 4). The accelerator has a similar design to ITER. Consider the 400 keV beam energy, the accelerator was designed with four layers of electrodes, which are plasma grid, extraction grid, acceleration grid, and ground grid. The detailed structures of negative beam source were designed initially with the RF plasma generator and the negative ion accelerator.

Electrostatic analysis and preliminary design of transmission line for the CRAFT NNBI test platform

Based on the development of Experimental Advanced Superconducting Tokamak (EAST), Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) has launched the project of China Fusion Engineering Test Reactor (CFETR). In order to explore and master fusion DEMO level key technologies, build key prototype systems for CFETR, a Comprehensive Research Facility for Fusion Technology(CRAFT)is being established. Negative-ion based Neutral Beam Injectors (NNBI), as one of the important parts of CRAFT, can provide neutral beam with 200∼400 keV beam energy and 2 MW beam power. Stable high voltage transmission is needed for the establishment and safe operation of NNBI. As one of the key components of high voltage transmission, transmission line (TL) plays an extremely important role. In this paper, four indexes, including the maximum electric field intensity (Emax), the inner surface electric field intensity (Esur) of the electromagnetism interference screening (EMIS), the equivalent distributed capacitance (Ceq) and the electric field non-uniformity coefficient (f), are used to evaluate the electric field performance of TL. And the relationship between these indexes and the position of acceleration grid (AG) conductor, the position of extraction grid (EG) conductor and the radius of EMIS is obtained by finite element (FE) analysis. Under the requirements of Esur and f, in order to reduce the maximum electric field intensity in the TL and equivalent distributed capacitance of the TL, the layout position of the TL is determined, which lays some theoretical foundations for the engineering design of the TL.

Long-pulse diagnostic calorimeter for the negative ion source testbed BATMAN upgrade.

The RF-driven negative ion source testbed BATMAN upgrade is being developed at IPP Garching in the framework of the ion source development for ITER and DEMO neutral beam injection systems. The testbed has recently been enhanced to allow for steady state operation with a focus on beam optics studies. The previous titanium sublimation pumps and inertial calorimeter limited the beam pulse length to about 6s every 3min. The upgrade comprises a long-pulse compatible, actively cooled diagnostic calorimeter. This has been designed and is currently being manufactured to substitute the inertially cooled calorimeter that has limited diagnostic capabilities. The new diagnostic calorimeter consists of a copper plate with dimensions of 910 × 660 × 25mm3 placed about 2m from the ion source extraction grids, and through a novel solution, it will provide a 2D profile of beam power density with a 20mm spatial resolution. Water flowing through cooling channels embedded in the copper plate will actively cool the calorimeter, which is loaded with about 160 kW beam power at ITER-relevant current density, but 45 kV acceleration. A fraction of the beam will pass through many small apertures (ø2mm) positioned in the calorimeter plate and will be collected by thin (0.2mm) copper foils attached to the calorimeter back side. Evaluation of power density will be performed by measuring the temperature of the heat flux foils with a high-resolution infrared camera observing the calorimeter from the back side and calibrated by thermocouples.

EFFECTIVENESS OF COMPUTER-BASED NURSING DOCUMENTATION IN NURSING CARE IN HOSPITAL – A LITERATURE REVIEW

Background: Nurse population in hospitals has a greater proportion than other health workers. Nearly 60-70% of the total human resources available, occupied by nurses. In fact, 90% of the health services provided are a form of nursing service. Therefore, nursing service is a form of professional service that is the biggest indicator in realizing the quality of hospital services. One of the duties of nurses in providing nursing services in accordance with standards is to document all nursing care provided. Objective: To review journals about documenting computer-based nursing care in hospitals for the effectiveness of the preparation of nursing care. Methods: Quantitative, mixed-methods, and qualitative reviews that aim to evaluate the influence of computerized nursing documentation (eg, management, computerized decision support systems and information systems) on nursing care were included. We used the nursing care performance framework as an extraction grid and analytical tool. This model illustrates how the interplay between nursing resources and nursing services can produce changes in patient conditions. The primary outcomes included nurses' practice environment, nursing processes, professional satisfaction, and nursing-sensitive outcomes. The secondary outcomes included satisfaction or dissatisfaction with computerized nursing documentation according to nurses 'and patients' perspectives. Reviews published in English, French, or Spanish from January 1, 2000 to December 15, 2019, were considered.&#x0D; Results: A total of 5515 titles or abstracts were assessed for eligibility and full-text papers of 72 articles were retrieved for detailed evaluation. It was found that 22 reviews published between 2002 and 2015 met the eligibility criteria. Many nursing care themes (ie, indicators) were influenced by the use of computerized nursing documentation, including time management; time spent on patient care; documentation time; information quality and access; quality of documentation; knowledge updating and utilization; nurse autonomy; intra and interprofessional collaboration; nurses' competencies and skills; nurse-patient relationship; assessment, care planning, and evaluation; teaching of patients and families; communication and care coordination; perspectives of the quality of care provided; nurses and patients satisfaction or dissatisfaction with computerized nursing documentation; patient comfort and quality of life related to care; empowerment; and functional status.

DHW tank sizing considering dynamic energy prices

Due to the rapid development of the building stock in Norway, the energy use in this segment is drastically increasing. Therefore, improving the energy performance of buildings becoming an urgent problem. Among technical systems in buildings, domestic hot water (DHW) systems have still significant untapped potential for energy saving. Storage tanks enable us to change DHW demand in buildings in a more energy-efficient and cost-effective way. However, to achieve this effect, the proper sizing and operation of the storage tanks are required. The aim of this study was to define a method for the DHW tank size optimization considering dynamic electricity prices and to assess how different electricity pricing methods would influence the DHW tank size. A dynamic discretized model of the DHW tank was used as a DHW tank model. Dynamic optimization was implemented as the optimization method to find the optimal tank charging rate based on the different pricing methods. Two pricing methods were considered in this study: 1) the current method with the fixed grid fee and 2) the power extraction method with the pricing of the maximum power extraction. The results showed that the electricity pricing pattern had significant impact on the DHW charging heating rate. In the case of the extraction fee pricing method, the charging rate was more stable over the day than in the case of the fixed grid fee. This stable charging rate gave stable DHW tank temperature over the day and the highest decrease in the total cost. A general conclusion was that the extraction grid fee pricing method would promote for stable charging over the day.

Development of technology for fabrication of prototype ion extraction grid for fusion research

• Ion extractor grids are the heart of any NBI system. • Ion extractor grid fabrication involves various critical technologies. • Friction welding for joining of dissimilar metals of SS304 L rod and OFHC copper plate. • Electro-deposition technique is best for making embedded coiling channels inside thin OFHC copper plate. • Surface flatness of 100 μm of grid is most important during CNC machining. Steady-state Superconducting Tokamak (SST-1) has a provision for a positive hydrogen ion-based Neutral Beam Injection (NBI) system. This system has a capability of injection of neutral hydrogen beam power of 1.7 MW at 55 kV. This NBI system consists of a 3-grid accel-decel ion extractor system. Each grid has 774 apertures distributed in the area of 23 cm × 48 cm on the OFHC copper plate. During beam operation grid received maximum heat load of ∼1.75 MW/m 2 which is removed by a dense network of 22 semi-circular ( r = 1.1±0.05 mm) cooling channels embedded between the rows of shaped apertures. The water flow velocity inside the cooling channel is 13 m/s and the pressure drop is 9 bar. To maintain the high electric field (∼7 kV/mm) between grids, the required surface flatness of the OFHC copper plate is 100 μm. Another requirement is positional tolerance of aperture of ±60 μm. All these critical requirements imply that the fabrication of the ion extractor grid is very complex and several technologies are involved: (i) Friction Welding (FW) for joining of dissimilar metals of SS304 L rod to the specific location of OFHC copper plate for the fabrication of water manifold of the grid. This has been successfully developed and obtained FW joint strength of 264 MPa (ii) 2.5 mm thickness electro-deposition of OFHC copper for making embedded cooling channels (iii) Precision CNC grid machining. This paper shall describe the development of these technologies for the manufacturing of the extractor grid.

Negative ion beam extraction in volume mode on the RF negative ion source at ASIPP

• A test equipment of RF negative ion source was modified according to the commissioning results of negative ions extraction. • The negative ion beam current density without Cs seeding was increased to 25 A/m 2 at 50 kW RF power. • The extracted H- current tended to be saturated at high RF power, but the co-extracted electron current kept increasing. • The e/H- ratio is monotonously decreased with the rising bias voltage. Hefei utility negative ions test equipment with RF source (HUNTER) has been developed at the Institute of Plasma Physics Chinese Academy of Sciences (ASIPP), in order to study the RF negative ion source for neutral beam injection application. This paper reports on several recent modifications made to HUNTER, including magnetic confining field, magnetic filter field, extraction area, pumping system, RF generator, high voltage power supply. And then, the performance of negative hydrogen ion beam extraction in volume mode without Cs seeding was reviewed and compared to the former commissioning results. The current of extracted negative ions and co-extracted electrons were recorded by the Hall current sensors installed on the electric wires connecting to the extraction grid, and ground grid and calorimeter. A similar extraction experiment from argon plasma verified the effective deflection and absorption of co-extracted electrons on the extraction grid, where the leaking electrons were less than 2%. The characteristic of negative ion beam extraction in volume mode was analyzed in different RF power, extraction voltage, bias voltage. The extracted negative ion density of 25 A/m 2 was achieved and the corresponding ratio of electron and negative ion current I e /I H- was 9.1, with the RF power of 50 kW and the bias voltage of 29 V. The extracted H − current saturated with RF power, while the co-extracted electron current increased. The current experimental results indicated the HUNTER source was operated on a right trace and is ready for the surface mode operation with Cs seeding.

A systematic review of patient prioritization tools in non-emergency healthcare services

BackgroundPatient prioritization is a strategy used to manage access to healthcare services. Patient prioritization tools (PPT) contribute to supporting the prioritization decision process, and to its transparency and fairness. Patient prioritization tools can take various forms and are highly dependent on the particular context of application. Consequently, the sets of criteria change from one context to another, especially when used in non-emergency settings. This paper systematically synthesizes and analyzes the published evidence concerning the development and challenges related to the validation and implementation of PPTs in non-emergency settings.MethodsWe conducted a systematic mixed studies review. We searched evidence in five databases to select articles based on eligibility criteria, and information of included articles was extracted using an extraction grid. The methodological quality of the studies was assessed by using the Mixed Methods Appraisal Tool. The article selection process, data extraction, and quality appraisal were performed by at least two reviewers independently.ResultsWe included 48 studies listing 34 different patient prioritization tools. Most of them are designed for managing access to elective surgeries in hospital settings. Two-thirds of the tools were investigated based on reliability or validity. Inconclusive results were found regarding the impact of PPTs on patient waiting times. Advantages associated with PPT use were found mostly in relationship to acceptability of the tools by clinicians and increased transparency and equity for patients.ConclusionsThis review describes the development and validation processes of PPTs used in non-urgent healthcare settings. Despite the large number of PPTs studied, implementation into clinical practice seems to be an open challenge. Based on the findings of this review, recommendations are proposed to develop, validate, and implement such tools in clinical settings.Systematic review registrationPROSPERO CRD42018107205

Expansion of alternatively extracted ion–ion beam in a low pressure collisional medium

The aim of this paper is to investigate, through particle-in-cell with Monte Carlo collisions (PIC-MCC) simulations, the effects of collisions on the expansion of an ion–ion beam formed by the alternate extraction of oppositely charged ions. This beam is extracted from an ion–ion plasma, formed in the downstream of a radiofrequency magnetically filtered iodine electronegative plasma, by the mean of two extraction grids. In this grid system, the screen grid is biased with a square voltage waveform, in the low MHz range, while the acceleration grid is grounded. The collisionless interaction between the extracted ion packets involves and enhances electrostatic waves propagating at beam velocity. Our results show that in addition to these electrostatic waves, the presence of significant fraction of low energy ions, produced by charge exchange, beside extracted fast ions gives rise to two-stream instability. Furthermore, space and time dependent electric field might accelerate the slow ions, produced by charge exchange collision. This acceleration, involving Landau damping and its inverse mechanism, is mainly due to the interaction between ions and potential patterns inherent to two-stream instability.

E × B electron drift current across the aperture of an ion source surrounded by a cusped magnetic field profile

In negative ion sources, a cusped magnetic field is generated by magnets placed around each aperture of the extraction grid in order to limit the co-extracted electron current. In spite of this suppression magnetic field, the co-extracted electron current is large, on the same order as the negative ion current extracted from the plasma. In this paper, we study the mechanisms of electron extraction from the plasma through a cusped aperture in a simplified situation, in the absence of negative ions, with the help of a three-dimensional Particle-In-Cell Monte Carlo Collisions model. The calculation results show that the electron current extracted from the plasma is small for an infinite slit aperture with a suppressed (cusped) magnetic field and significantly increases in the case of finite slit or circular grid apertures. We find that the E×B electron drift plays an important role in the extraction of electrons through a finite slit grid aperture and that current driven micro instabilities are present in the aperture region. This work is relevant to negative ion sources and micro-ECR neutralizers designed for space propulsion.