@InProceedings{GonçalvesSandIrit:2007:IoBmCo,
               author = "Gon{\c{c}}alves, Jos{\'e} Am{\'e}rico Neves and Sandonato, 
                         Gilberto Marrega and Irita, Ricardo Toshiyuki",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)}",
                title = "Ion bmbardment comparative studies for hollow cathode started by 
                         anode and keeper pulse voltage",
                 year = "2007",
         organization = "Encontro Brasileiro de F{\'{\i}}sica dos Plasmas, 9.",
             abstract = "Hollow cathodes have been studied extensively since the early 
                         1930s due to their wide range of applications in vacuum 
                         microelectronic devices, microwave tubes, lasers, and materials 
                         processing. Over the past two decades hollow cathodes have also 
                         become critical components in many °ight electric propulsion 
                         systems such as Kaufman-type and Hall-e®ect thrusters. Cathodes 
                         made of either porous tungsten inserts or tantalum rolled foils, 
                         impregnated with barium aluminates or barium oxides are potential 
                         candidates to meet the performance and lifetime requirements for 
                         both space and ground based applications. Empirical studies of 
                         impregnated cathodes in diodes and traveling-wave tubes were 
                         carried out in the late 1970s. These studies showed that lifetime 
                         is largely determined by the rate at which the emitting material 
                         is depleted by ion bombardment over the cathode surface. The 
                         hollow cathode developed and investigated in the Associated Plasma 
                         Laboratory at INPE, consists of components mechanically assembled 
                         and rolled tantalum foil oxide emitters. A 5mm outside- diameter 
                         Ta tube, 40mm long and 0:3mm thick, having in one end a small 
                         Molybdenum tip disk (mechanically pressed) with an ori¯ce of 1:2mm 
                         diameter comprises the body of the hollow cathode. The emitter was 
                         built using a Ta foil painted with (Ba; Sr;Ca)CO3 and rolled into 
                         an approximately ¯ve-turns insert, with an outside- diameter of 
                         4:7mm, an inside-diameter of 3mm and a length of 12mm. This work 
                         will show the harmful e®ects of the ion impacts on the insert 
                         surface, when the hollow cathode is started up by turning on both 
                         voltages at the keeper and anode at the same time. The tantalum 
                         foil is melted close to the molybdenum tip and sprayed through the 
                         ori¯ce, reducing its life time to only few hours. However, when 
                         the hollow cathode is started up only by the keeper and the 
                         discharge set to the anode afterwards, there are no signi¯cant 
                         damages. These results were investigated by Scanning Electron 
                         Microscopy with X-ray microanalysis.",
  conference-location = "S{\~a}o Pedro, SP",
      conference-year = "25-28 Nov.",
             language = "pt",
        urlaccessdate = "18 maio 2024"
}