Low voltage rep-rate cathode investigations
- Army Research Lab., Watertown, MA (United States)
An experiment is underway to study the performance of several materials as field-emission cathodes for low voltage ({le} 100 kV), repetitive (< 1 kHz) electron accelerators. A thyratron-switched Blumlein line modulator with a 70 {Omega} characteristic impedance, and 1 {mu}s pulse width, is operated between 20 and 100 kV, from single-shot to 300 Hz rep-rate. This provides a high average power (50 kW) test bed for the study. A comparison is made of cathodes fabricated from velvet, carbon, diamond coatings, niobium wire nanocomposite, and poly-crystalline tungsten. Surface emission is monitored by an array of Faraday Cups. The turn-on time, uniformity of emission, and gap closure time are measured as a function of the spatially averaged, macroscopic electric field at the cathode. Beam emittance is determine for a variety of cathodes using a pepperpot emittance diagnostic. A cold cathode capable of > 100 A/cm{sup 2}, with a long lifetime (> 10{sup 6} shots), and reproducible from shot-to-shot would be valuable in the new generation of repetitively pulsed electron beam sources useful in industrial, military, and research applications. The goal of this effort is to identify high-current-density cathodes that have reproducible and uniform emission, when operated at applied diode potentials {le} 100 kV. In addition, this cathode should provide high durability in repetitive ({approx} 1kHz) operation and not produce fast moving plasmas which short circuit, i.e. close, the diode anode-cathode (AK) gap.
- OSTI ID:
- 51785
- Report Number(s):
- CONF-940604-; ISBN 0-7803-2006-9; TRN: IM9524%%253
- Resource Relation:
- Conference: 1994 Institute of Electrical and Electronic Engineers (IEEE) international conference on plasma science, Santa Fe, NM (United States), 6-8 Jun 1994; Other Information: PBD: 1994; Related Information: Is Part Of IEEE conference record -- Abstracts; PB: 252 p.
- Country of Publication:
- United States
- Language:
- English
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