Determination of Optical Properties of a Field Emission Gun Coupled with a Linear Accelerator for High Voltage Microscopy

The electron optical properties of a field emission gun plus a twenty-stage linear accelerator system have been determined in the case where the entrance pupil of the system is defined by one of the electrode apertures. The first part of the calculation concerns the electrical and geometrical parameters of triode and tetrode field emission guns which can give a fixed location of the source and a small spherical aberration coefficient. The second part is related to the possibility of placing a tetrode field emission gun at the top of the linear accelerator of the scanning high voltage electron microscope which is being constructed in the Toulouse Laboratory. Interesting conditions can be obtained when the electrical parameters are fixed as follows: either Vi/Ve= 0 or Vi/Ve= 20 (Ve is the extracting voltage, Vi is the potential of the second anode of the gun) whatever the accelerating voltage may be

BUILD-UP OF MONOCRYSTALLINE TUNGSTEN TIPS FOR F.E.G.

Le remodelage de l'apex de pointes de tungsten monocristallines (111), (310) et (611) est étudié en fonction de la durée, de la température et de la tension de remodelage. Pour une même tension d'extraction le courant d'émission peut être multiplié par 103 à 105, l'angle d'emission étant divisé par 4 voire 7.5 dans le cas de pointes (611).The build-up of monocrystalline tungsten tips (111), (310) and (611) is studied as a function of the build-up duration, temperature and voltage. For the same extraction voltage the emitted current can be increased by a factor between 103 and 105 when the emission angle is divided by 4 or even 7.5 for (611) tips

Electronic environment for a field emission gun in electron microscopy

The high brightness, the low energy spread and the small diameter of the source given by a field emission gun is particularly interesting in electron microscopy. This paper describes the extracting anode supply, the polarity of which may be reversed in order to remolde the tip. The heating device of the tip enables its cleaning, the room temperature emission, and also the temperature and field emission. A particular attention has been paid to the protection of the tip and supplies, because of the numerous disruptive breakdowns which can occur in that type of gun. The fluctuations of the emitted current are one of the difficulties encountered with this kind of source. The study of the current feedback control which drives the extracting voltage generator with respect to the total current or partial current emitted is dealed.En microscopie électronique, un canon à émission de champ est particulièrement intéressant par sa très grande brillance et la faible dispersion en énergie du faisceau électronique. Cependant, son emploi qui s'avère très délicat, nous a amenés à concevoir et réaliser un environnement électronique. Cet article décrit l'alimentation de l'anode d'extraction, dont la polarité peut être inversée afin de remodeler la pointe, le dispositif de chauffage de celle-ci permet son nettoyage ainsi que l'émission en température ambiante (T.A.) et l'émission assistée (T.F.). Un soin particulier a été porté pour la protection de la pointe et des alimentations, car ce type de canon est fréquemment le siège de phénomènes disruptifs. Une des difficultés de son utilisation est due à l'instabilité du courant émis. L'étude d'un asservissement de la tension d'extraction à la valeur du courant émis total ou partiel est abordée

Uso de infravermelho próximo para estimativa das falhas no estande e produtividade do amendoim

This research aims to study the use of NIR images for peanut production estimates in three different planting processes (conventional tillage, no-tillage, and planting Rip Strip) relating productivity information with extracted parameters Orthophoto generated by an Air Vehicle No manned (UAV). The images 0.2 cm error range compounds were analyzed in extracts of two central lines launched in all replicates of the various treatments. For each line, 100 linear meters were measured and quantified the existence of faults; subsequently determined the actual planting observed in each treatment and correlated with output in the treatments. planting lines and identified failures were analyzed through the Geographic Information System (GIS) Quantum Gis. The results of the correlation tended to a positive correlation between the failure data and foliar weight and yield, is a positive indicator of the use of the tool for productivity measurements by the NIR. The studies will be repeated in different conditions and variables for an improvement in productivity analysis and estimationO presente trabalho tem por objetivo estudar o uso de imagens NIR para estimativa de produção de amendoim em três diferentes processos de Plantio (plantio convencional, plantio direto e plantio Rip Strip) relacionando informações de produtividade com parâmetros extraídos de Ortofoto gerada por um Veículo Aéreo Não Tripulado (VANT). As imagens em escala de erro de 0.2 cm foram analisadas em extratos compostos de duas linhas centrais lançados em todas as repetições dos diferentes tratamentos. Para cada linha, com 100 metros lineares foram medidas e quantificadas a existência de falhas; posteriormente determinou-se o efetivo plantio verificado em cada tratamento e correlacionou- se com a produção obtida nos tratamentos. As linhas de plantio e as falhas identificadas, foram analisadas, através do Sistema de Informação Geográfica (SIG) Quantum Gis. Os resultados da correlação tenderam a uma correlação positiva entre os dados de falhas e massa foliar e produtividade, sendo um indicador positivo de uso desta ferramenta para medições de produtividade através de NIR. Os estudos serão repetidos em diferentes condições e variáveis para um aprimoramento da análise e estimativa de produtividade

Avaliação de RPAs para pulverização em diferentes culturas

The present work had as objective to study and to validate the application of defenses through RPAs (Remotely Piloted Aircraft), commonly denominated Drones. The experiment happened at APTA East Center in Ribeirão Preto, Sao Paulo. The herbicide solution glyphosate 1.5 kg ha-1 (Roundup WG®) was used using 15 L ha-1 of syrup volume. The RPA that overflew the study area at three different altitudes together with three different spray nozzle models in a range of 50 m x 5 m, with water-sensitive papers being distributed in these bands to verify the size, quantity and distribution of drops that fell on the plants. Once the information was counted, it was expected that it would be possible to create different application models, leading to greater efficiency and effectiveness of theapplications. In addition, avoid waste of defense, contributing to decrease environmental impacts and increase safety in the field (lower risk of intoxication). The results allowed to identify competitive advantages, highlighting the practicality and speed, besides allowing localized control of weeds, without the need of tractors, which increases soil compaction and requires greater investment in equipment. From these results, use protocols will beestablished for various agricultural crops, such as: Peanut (Arachis hypogaea L.), Sugarcane (Saccharum officinarum L.), Soya (Glycine max L.), Maize (Zea mays).O presente trabalho teve como objetivo estudar e validar a aplicação de defensivos através de RPAs (Aeronave Remotamente Pilotadas), comumente denominadas de Drones. O experimento foi realizado na APTA Centro Leste no município do Ribeirão Preto, SP. Foi utilizado a: solução de herbicida glifosate 1.5 kg ha-1 (Roundup WG®) utilizando 15 L ha-1 de volume de calda. O RPA que sobrevoou a área de estudo em três diferentes altitudes, juntamente com três diferentes modelos de bicos pulverizadores em uma faixa compreendida de 50 m x 5 m, sendo que nessas faixas foram distribuídos papéis sensíveis à água, para verificar o tamanho, quantidade e distribuição de gotas que caíram sobre as plantas. Uma vez contabilizadas as informações, esperou-se que fosse possível criar diferentes modelos de aplicações, levando a uma maior eficiência e eficácia das aplicações. Além disso, evitar desperdício de defensivo, contribuindo para diminuição dos impactos ambientais e aumento da segurança no campo (menor risco de intoxicações). Os resultados permitiram identificar vantagens competitivas, com destaque para a praticidade e rapidez, além de permitir controle localizado de plantas daninhas, sem a necessidade de uso detratores, o qual aumenta compactação do solo e requer maior investimento em equipamentos. A partir destes resultados, serão estabelecidos protocolos de utilização para diversas culturas agrícolas, tais como: Amendoim (Arachis hypogaea L.), Cana-de-açúcar (Saccharum officinarum L.), Soja (Glycine max L.), Milho (Zea mays)