Cold Cathode Materials for Pseudospark Switches

Abstract

In general, for plasma switches, the initiation of the plasma is critical and this is usually achieved by a “trigger” scheme. The seed electrons needed to initiate a breakdown can be generated by several means such as thermionic, field or optical emission. While the thermionic emission has been used mainly in vacuum tubes and is a mature technology, field emission (or cold-cathode electron emission) has been the subject of recent studies and technology. The efficiency of these seed electron emission determines how well the plasma switch can close or open. It is known that the carbon nano tubes (CNTs) have excellent field emission characteristic under high vacuum pressure of 10-7 to10-6 Torr and they have been considered as prima candidates as cold-cathode electron emitters. On the other hand, most plasma switches operate at mTorr pressure ranges, which is relatively higher than the vacuum pressure levels mentioned above. Therefore, the electron emission characteristics of CNTs in elevated pressures higher than vacuum need to be known to evaluate possible use of them as trigger electrode. The purpose of this research is to observe the field emission characteristics of several different kinds of CNT samples and other nano materials in background pressures ranging from 10-3 Torr to 1 Torr.