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Home Material Sciences Efficiency increase of the hollow cathodes electric propulsions by using the modified cathode materials

Efficiency increase of the hollow cathodes electric propulsions by using the modified cathode materials

Description

The main component of electric propulsions is the hollow cathode with thermionic emitter. At present single crystals of lanthanum hexaboride LaB6 are generally used in the capacity of emitter materials. If the emitter is characterized by lower electron work function it is possible to reduce the operating emitter temperature. The latter leads to the power inputs reduce on discharge maintenance in hollow cathode, to abrupt decrease evaporation rate of the emission active components, to absence of the structural members overheating, and as it follows, to the resource increase and propulsion efficiency growth in toto.

For these goals achievement it is proposed to use modified LaB6 single crystal emitters. The modification consists in oxygen ion bombardment. In this case the electron work function decreases and the thermionic emission current density increases. E.g. the stable emission current density increase takes place from 5.6 to 66 A/cm2 after the oxygen ion bombardment at 30 KeV and fluencies 1019 -1020 cm-2. This makes it possible to a considerable extent reduce of operating emitter temperature. Another efficiency increase method is the use of the pressed emitter materials based on barium hafnate with tungsten. Emitter of 63 % BaHfO3 – 37 % W (by mass) is enables a thermionic current density of 230 A/cm2 at temperature T = 2000 K.

Innovative Aspect and Main Advantages

LaB6 single crystals use after oxygen ions bombardment and cathode materials based on barium hafnate with tungsten too allows considerably reduce the operating emitter temperature. In order to product the typical for electric propulsion thermoemission current density of 5 A/cm2 it is necessary to heat LaB6 single crystal up to 1760 K.

These operating temperatures decrease to 1630 and 1405 K for the irradiated by oxygen ions LaB6 and emitter based on 63 % BaHfO3 – 37 % W (by mass) respectively. Mentioned thermionic current density increase remains at the least a minimum of 15,000 h operational testing. Mentioned cathode materials are characterized by enhanced poisoning resistance in addition. The evaporation rate of emission active component for emitter based on BaHfO3 –W system equals to 5*10-6 кg/(m2*s) at Т = 1900 К.

Areas of Application

All developed and studied emission materials are prospective candidates for thermionic cathode applications in hollow cathode electric propulsion, high-power electric devices and electroarc plasma generators.

Temperature dependences of thermionic current
density
Fig. 1 Temperature dependences of thermionic current
density for irradiated by oxygen ions LaB6

Emitting surface of BaHfO3
Fig. 2 Emitting surface of BaHfO3 –W cathode
after emission tests

Stage of Development

The techniques for producing pressed cathodes based on barium hafnate with tungsten and modified LaB6 single crystals have been developed, laboratory tests are carried out. Cathode developments are protected by:

  • Patent USSR «The technique for producing lanthanum hexaboride cathode» № 1716916
  • Patent Ukraine «Material for thermionic cathode» № 51550 А

Contact Details

Contact person: Taran Anatoliy
National aerospace university “Kharkiv aviation institute”
Address: 17, Chalova str., Kharkiv, Ukraine, 61070
Tel: +380577074505 (w.), +380502026439 (m.)
Fax: +38057-315-11-31
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it , This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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