Krytron

Abstract: A cold cathode vacuum discharge tube is used in a circuit for generating pulsed autoelectronic emissions which are particularly intense and frequent in the abnormal glow discharge region, and involve much lower current densities than predicted by the Fowler-Nordheim vacuum arc discharge region law. The discharge tube is characterized by a large electrode area at least of the cathode, and a large interelectrode gap. The electrodes are preferably spaced at least 2 cm apart in a parallel relationship. A probe may be introduced between the electrodes to reduce still further the field required to generate the emissions. In another configuration the probe forms the anode and two plates form cathodes. The circuit is driven from a direct current source of having an impedance sufficient to prevent establishment of a vacuum arc discharge.

Abstract: A spark gap device that is formed in an integrated circuit (IC). The IC has a dielectric substrate upon which a high-voltage switch is disposed. The switch includes an anode element and a cathode element separated from each other by a spark gap. A trigger electrode is disposed on the substrate material in the spark gap. A capacitor is electrically coupled to the trigger electrode. The cathode and anode elements and the trigger electrode preferably are at least partially covered with a dielectric material. When the capacitor is charged, the charge on the capacitor exerts a strong electric field on the cathode and anode elements that causes ions to migrate in the cathode and anode elements toward the spark gap. When the trigger electrode is excited by an electrical current, the ions arc across the gap and a conductive path is created between the cathode element and the anode element.

Abstract: A high voltage switch tube with a central cathode cylindrically symmetric to and surrounded by a tubular anode, with a grid interposed between the cathode and anode. A high negative voltage is applied to the cathode, but the flow of electrons to the anode is blocked by the grid which is held near cathode potential. After a space charge is created at the grid by electrons from the cathode, the grid is pulsed to ground potential, releasing electrons from the cathode to yield a very high current pulse. The cathode is preferably a graphite foam sleeve mounted on a support structure.

Abstract: The paper presents an overview on the current status of the development of the so called pseudospark switches. The pseudospark itself is characterized as a low pressure gas discharge located on the left branch of the Paschen curve. Based on this discharge a family of fast gas discharge closing switches for pulsed power applications have been developed at Erlangen for more than 10 years. Due to the similarity to thyratrons however without having a hot cathode the pseudospark devices are often described in literature as cold cathode thyratron. One main task is to replace switching devices like ignitrons or high-pressure spark gaps due to their mercury filling or their limited lifetime. They are also able to replace thyratrons in many applications. The main features of the pseudospark switches are a high current rise closed to 10/sup 12/ A/sec., the ability to carry reverse currents up to 100 per cent, low pulse jitter and a high lifetime. The cold cathode reduces also the required standby power one magnitude lower than in thyratrons. On the other hand one gets especially at low peak currents also undesired phenomena by the physics of the cold cathode. Current quenching, chopping and impedance fluctuations are problems which occur at currents less than 2-3kA. At very high peak currents above 20-30kA a transition to a metal vapor arc occurs which is correlated with high cathode erosion. Depending on the requirements of different pulse power applications solutions are discussed to solve or to reduce the above described problems of the cold cathode emission.