@MastersThesis{Asencio:2014:CaCáOc,
               author = "Asencio, Jenny Carolina Robledo",
                title = "Caracteriza{\c{c}}{\~a}o de c{\'a}todos ocos para 
                         propuls{\~a}o i{\^o}nica",
               school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
                 year = "2014",
              address = "S{\~a}o Jos{\'e} dos Campos",
                month = "2014-06-04",
             keywords = "c{\'a}todos ocos, propulsores i{\^o}nicos, sonda 
                         eletrost{\'a}tica, hollow cathodes, ion thrusters, eletrostatic 
                         probe.",
             abstract = "Os c{\'a}todos ocos s{\~a}o dispositivos que podem fornecer de 
                         forma eficiente alta densidade de corrente de el{\'e}trons, de 
                         modo que s{\~a}o componentes fundamentais para propulsores 
                         i{\^o}nicos como principal fonte de el{\'e}trons para a 
                         gera{\c{c}}{\~a}o de plasma na c{\^a}mara de descarga e para 
                         neutraliza{\c{c}}{\~a}o do feixe de {\'{\i}}ons. O 
                         Laborat{\'o}rio Associado de Plasma (LAP) do Instituto Nacional 
                         de Pesquisas Espaciais (INPE) tem desenvolvido c{\'a}todos ocos 
                         desde o ano 2002, e estudos experimentais detalhados para 
                         caracterizar o seu desempenho n{\~a}o foram realizados at{\'e} o 
                         momento. A presente disserta{\c{c}}{\~a}o apresenta um estudo 
                         experimental minucioso sobre a caracteriza{\c{c}}{\~a}o da 
                         descarga de c{\'a}todos ocos equipados internamente com insertos 
                         de folha de t{\^a}ntalo e externamente com eletrodos de vigia 
                         envolventes. Foram testados tr{\^e}s diferentes di{\^a}metros de 
                         orif{\'{\i}}cios das ponteiras dos c{\'a}todos e dos eletrodos 
                         de vigia envolventes. Foram identificados os modos de descarga 
                         (pluma, difusivo, pontual e transi{\c{c}}{\~o}es) e foram 
                         medidos par{\^a}metros de plasma (usando uma sonda de Langmuir 
                         cil{\'{\i}}ndrica simples) para diferentes condi{\c{c}}{\~o}es 
                         operacionais, onde se variaram par{\^a}metros tais como 
                         vaz{\~a}o m{\'a}ssica, tens{\~a}o de descarga e corrente de 
                         descarga e usando arg{\^o}nio ou xen{\^o}nio. Tr{\^e}s 
                         diferentes circuitos el{\'e}tricos de corrente de descarga foram 
                         comutados, diodo com anodo, diodo com eletrodo de vigia e 
                         tr{\'{\i}}odo, dependendo da estabilidade da descarga de catodo. 
                         Os dados coletados pela sonda eletrost{\'a}tica foram 
                         p{\'o}s-processados usando-se um algoritmo para estimar as 
                         densidades de el{\'e}trons e {\'{\i}}ons, potencial flutuante, 
                         potencial de plasma e temperatura de el{\'e}trons em diferentes 
                         posi{\c{c}}{\~o}es axiais da sonda, a partir da 
                         superf{\'{\i}}cie do eletrodo de vigia at{\'e} perto do anodo. 
                         Os resultados obtidos neste trabalho, em termos de modos de 
                         descarga e par{\^a}metros de plasma est{\~a}o de acordo com os 
                         relatados na literatura e s{\~a}o considerados como os 
                         t{\'{\i}}picos para c{\'a}todos ocos. ABSTRACT: Hollow cathodes 
                         are devices that can provide, efficiently, high electron current 
                         densities, so that, they are primary components for ion thrusters 
                         as the main source of electrons for plasma generation in the 
                         discharge chamber, and for the ion beam neutralization, as well. 
                         The Associated Plasma Laboratory (LAP) at National Institute for 
                         Space Research (INPE) has been developing hollow cathodes since 
                         2002, and no detailed experimental studies have been carried out 
                         to characterize their performance, so far. The present 
                         dissertation brings a detailed experimental study on the discharge 
                         characterization of hollow cathodes equipped internally with 
                         rolled tantalum foil inserts and externally with enclosed keepers. 
                         Three different orifice diameters on the tips of the cathodes and 
                         enclosed keepers were tested. Discharge modes (plume, diffuse, 
                         spot and transitions) were identified, as well as, the plasma 
                         parameters were measured (the latter using a single cylindrical 
                         Langmuir probe) under different operating parameters, such as the 
                         mass flow rate, discharge voltage and current, and using argon or 
                         xenon. Three different configurations of the electrical circuit 
                         carrying the discharge current were switched, namely, anode-diode, 
                         keeper-diode and triode, depending on the stability of the cathode 
                         discharge. The data collected by the electrostatic probe were post 
                         processed using a numerical algorithm, such that, densities of 
                         electrons and ions, plasma and floating potentials, and electron 
                         temperature could be all estimated for different axial locations 
                         of the probe, apart from the keeper tip up to distances near the 
                         anode. The results obtained in this work, in terms of discharge 
                         modes and plasma parameters, are in agreement to those reported in 
                         the literature and are considered as typical ones for hollow 
                         cathodes.",
            committee = "Marques, Rodrigo Intini (presidente/orientador) and Sandonato, 
                         Gilberto Marrega (orientador) and Costa, Fernando de Souza and 
                         Maciel, Homero Santiago",
         englishtitle = "Characterization of hollow cathodes for ion thruster",
             language = "pt",
                pages = "169",
                  ibi = "8JMKD3MGP5W34M/3GD2HTE",
                  url = "http://urlib.net/ibi/8JMKD3MGP5W34M/3GD2HTE",
           targetfile = "publicacao.pdf",
        urlaccessdate = "27 abr. 2024"
}