Cathodic arc deposition of barium oxide for oxide-coated cathodes

Conference · Thu Dec 31 04:00:00 EST 1998

OSTI ID:346867

Umstattd, R; Pi, T; Luhmann, N Jr ^[1]; Scheitrum, G ^[2]; Monteiro, O; Brown, I ^[3]

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1. Univ. of California, Davis, CA (United States)
2. Stanford Linear Accelerator Center, CA (United States)
3. Lawrence Berkeley Lab., CA (United States)

Cathodic arc deposition is used to create a barium oxide plasma which is then deposited/implanted onto a cathode nickel substrate. The primary motivation for this work is the critical need for a reliable, repeatable thermionic cathode for the production of high power, microsecond duration microwave pulses. The deposition is performed by generating a cathodic arc discharge at the surface of a barium of barium-strontium alloy rod. The metal plasma thus created is deposited onto the target in the presence of small amounts of oxygen. Difficulties in handling the highly hygroscopic barium and strontium sources were addressed by encapsulating the source rods in thin nickel sleeves (nickel being the major constituent of the deposition target). Both filtered and unfiltered depositions were performed; the former in the interest of improving film quality and the latter in an effort to improve deposition rate. The plasma deposition is monitored via a rate thickness monitor, an optical emission spectrometer for plasma composition information, and an electrostatic probe for the density and temperature profile of the plasma. Good film adhesion is critical for oxide cathodes since they are continually cycled, this, substrates are pulse biased during deposition to encourage implantation. An initial test was performed in which a film of barium oxide approximately one micron in thickness was deposited onto a small section of a 1 in. diameter nickel cathode with better than expected mission results. These preliminary results will be presented together with the results from follow-up experiments done to improve overall coating quality and emission performance.

• OSTI ID: 346867
• Report Number(s): CONF-980601--
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
BARIUM OXIDES
CATHODES
MICROWAVE EQUIPMENT
PLASMA PRODUCTION
SUBSTRATES
SURFACE COATING
THERMIONIC EMITTERS