Isotope labeling of the uniformity for Ba active composition in a dispenser cathode powder during grinding

Abstract

With the aim of serving various microwave devices in IECAS since the middle of the 19th century, various Ba dispenser cathodes such as the tungstate, the aluminate, the scandate Ba dispenser cathodes, and the carbonate Ba dispenser cathode [1,2] have been researched and quanlified. For carbonate Ba dispenser cathode, excellent emission property has been obtained [1], its various performance measurements [3] and analysis researches in the field of physiochemistry [4] have been made, in those efforts, some were useful for reference up to now, in which the topic of distribution uniform research of Ba active composition during grinding is one of topics. For the grind problem, a small amount of cathode powder material used as research, a redundant time of grinding by hand is very hard, and for a large amount of cathode powder material which is used for industry, a grinded time by machine is anxious to know how much grinded time the powder is uniform. There are lot of methods can measure the distribution uniform of a powder material. The surface science method, for example the photoelectron spectroscopy is convenient, but the way can be make just for some larger units which have more funds. The chemical analysis method is in common use, but some time it isn't effectual when it must be through chemical operating with over-elaborate procedures, occupy more samples, sources of manpower and material, and analysis times etc. The radioactive isotopes method has advantages and disadvantages, the radionuclide has the radiation, which maybe harmful to the health, but this method has advantages: the measurement of the radioactive radiation is rather easy, thus very low amounts of these isotopes sample can be enough, for example, under a normal apparatus for detection 14C labeled compounds, needed amount of sample can be decrease to milligrams, even reach to an order of magnitude of (10−9–10−12) g, means a high sensitivity, and no destroy can be happen to original sample material.. Besides the tracer and the same original material move together, change together, sampling for measuring is unable to destroy original process and original material. The measurement is simple, fast, saving, and is able to realize a measurement with fixed quantity. There are lot of reports about research electron emission phenomena by isotopes methods, this way has been used for research the performances of cathode base, the diffusion, evaporation, separation under bombardment, decomposition and activation, surface absorbing, and interactive of cathode composition from cathode layer or base etc in history [5]. In recent years, as we knew from references, a great contribution about exposing the growing mechanism of the single wall carbon nanometer tube SWCNT also is done in using of the isotope labeled method [6].