Thermal Analysis and Testing of Different Designs of LaB6 Hollow Cathodes to be Used in Electric Propulsion Applications

Kokal U., Turan N., ÇELİK M.

AEROSPACE, vol.8, no.8, 2021 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 8 Issue: 8
  • Publication Date: 2021
  • Doi Number: 10.3390/aerospace8080215
  • Journal Name: AEROSPACE
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: electric propulsion, hollow cathode, LaB6 emitter, thermal analysis
  • Istanbul Technical University Affiliated: No


LaB6 emitters are commonly used in hollow cathodes that are utilized in electric space propulsion systems. In order to obtain necessary surface current emission densities of 1-10 A/cm(2) for cathode operations, LaB6 emitters require temperatures above 1500 degrees C. Hence, the design for LaB6 cathodes presents thermal and mechanical challenges. In this paper, several design iterations for LaB6 hollow cathodes are presented and thermal analyses are conducted for each design. Temperature and heat flux distributions that are obtained from thermal analyses are investigated. The designs are evaluated according to the required heat input to the emitter, and the radiative and conductive heat loss mechanisms. In addition to the thermal analyses, experimental tests are conducted for different cathode designs and, based on these tests, various modes of failure are determined. Revising the cathode design and the material selection iteratively to eliminate the encountered failure mechanisms, a novel cathode design is achieved. Experimental tests of this novel cathode are conducted and current-voltage characteristics are presented for different mass flow rates and for discharge currents between 0.5 and 12 A. Tests and analysis results show that the selection of materials and design are crucial for a sturdy and long lifetime cathode.