The Experimental Study Of Oxide Coated Cathode Plasma Source

1903,Wehnelt.A found that the platinum wire emit current is greatly increased at high tem-perature when some alkaline earth metal oxide stick on the surface of wire, which is the starting point of the oxide coated cathode. The oxide cathode is short for the emitters which are made of alkaline earth metal(barium, strontium, calcium) oxides. There are some advantages of oxide cathode,such as large emission current,low working temperature.so it has been using widely in the fields of defense and communications since 1940s.From 1970s,oxide cathode began to be used as the plasma source in America, but there are no device using large area oxide cathode till now.The LMP device designed the first large area indirected heated oxide coated cathode in our country.at the temperature of 650℃～1000℃,the cathode achieve a larger emission curren-t (3～10A/cm2),and uniform,stability,quiet.In a weak magnetic fleld,the cathode produce a higher density and spanning four orders of magnitude (1010～1013/cm3),which is an ideal plasma source for the study of plasma physics. At first.This paper presents the main compo-nents of the cathode, detailed described design parameters and material properties, all of the components of the cathode are stability at the temperature as high as 1000℃,achieve the en-gineering Indicators.Every part of the cathode was carefully designed.to keep the entire equip-ment installation space as small as possible to successfully installed in LMP device.To ensure that the heating efficiency to maximize, We analyzed the temperature of various components by the means of simulations.Second,i completed the launch slurry preparation, milling, processing of base metal, cath-ode spraying, a set of process of the activation process and the handling of accidents by con-stantly experiment summary and explore, we achieved the steadily discharge of the oxide cath-ode in large current.To have a understanding of the oxide cathode emission properties, we anal-ysis the oxide cahtode discharge at different conditions such as discharge voltage,neutral pres-sure,magnetic field,discharge frequency.pulse width.the cathode temperature and so on.I ex-plained all the phenomenons of the oxide cathode discharge in detailed, we excite ion-acoustic waves in oxide cathode discharge and estimated the ion temperature about 0.25 eV by it’s Lan-dau damping.At the same time,we can make the plasma column carrying hundreds of amps of current to achieve the discharge of different uses.In this discharge condition,we have some study on the current driven Electrostatic Ion-Cyclotron Instability(EICI).At last.I create a new type of oxide cathode by changing emitting material formulation-s,such as restore or catalytic material.We find that the new type oxide cathode discharge ability about 2～3 times of the common oxide cathode when adding some Sc2O3,This is the first time of oxide cathode achieved so high emission ability in plasma science by so simple means.The new cathode’s emission ability as high as LaB6 cathode and no higher demands on the materi-als and temperature.