Tungsten dispenser cathodes have been Semicon Associates’ core business for more than 50 years. Semicon has extensive experience in supplying not only dispenser cathodes, but various other cathodes and cathode assemblies. 20,000 cathodes are produced each year for virtually any application or customer requirement. These cathodes consist of a porous tungsten matrix impregnated with a barium based emission enhancing material.

Additional structures such as support sleeves, mounting flanges, heat shields, emission shields , high voltage insulators and grids, all the way to the complete Electron Gun, are added per customer requirements (See Electron Guns.) The cathode matrix may also be a mixed metal such as tungsten iridium or tungsten molybdenum (Sembo).

Dispenser cathodes are used in all types of vacuum devices and in inert and reducing atmospheres. The most common applications include TWTs, klystrons, magnetrons, and plasma devices.

Semicon controls the entire cathode manufacturing process beginning with basic raw materials and including the manufacturing of critical components. The standard manufacturing process includes chemical cleaning of the emitting surface which ensures open porosity and verification using scanning electron microscopy. Cathode heater assemblies are also 100% tested for proper heater operation. Semicon has quality systems in place that can provide full flight qualified cathode assemblies with all required backward and forward material and process traceability.

Semicon's engineering staff is ready to assist in any custom design requirement. Our specialists can assist with a design that will satisfy customer requirements while maintaining manufacturability. Assistance with establishing tradeoffs needed to obtain required emission, limit barium evaporation rate and adequate lifetime is also provided.

Typical Specifications
Commercial, Military, or Space Qualification

Size range	0.010" - - 8.00" (0.25 mm - 200 mm)
TungstenDensity Range	74% - 84%
Impregnant Types	4:1:1 (S), 5:3:2 (B),6:1:2,3:1:1, or any other required type
Sputter Coatings	Osmium Ruthenium (M), Iridium. Other coatings possible.
Materials	Tungsten, molybdenum, molybdenum-ruthenium, rhenium, tungsten-rhenium, Kovar, nickel, stainless steel, Monel, and others.
Machined Tolerances	To +/-.0002" (+/-0.005 mm)
Brazes	Ranging from molybdenum-ruthenium (mp 1980°C) to low temperature alloys such as copper-gold (mp 910°C)
Operating Temperature	From 910°CB to 1200°CB
Emission Density	Continuous, as high as 20 A/cm2, typically 2-5 A/cm2; pulsed, as high as 120 A/cm2, typically 30-70 A/cm2
Life Expectancy	From 3,000 hours to 150,000 hours

Beyond technical expertise, we offer a market and team driven approach. Semicon Associates will partner with you to develop customized solutions tailored to your needs. Our partnership continues after the sale is completed to ensure you get maximum benefit from your purchase.

Cathode Type	Description	Work Function
B	Porous tungsten impregnated with 5:3:2 Ba)-Ca)-Al2O2	2.1 ev
S	As above (4:1:1)	2.1 ev
M	Above coated with Os/Ru	1.8 ev
MM	Porous tungsten iridium with Ba)-Ca)-Al2O2	1.8 ev