Light initiated high power electronic switch

• US 4,771,168 A
• Filed: 05/04/1987
• Issued: 09/13/1988
• Est. Priority Date: 05/04/1987
• Status: Expired due to Term

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Gundersen, Martin, Kirkman, George
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US07/046,405
• Time in Patent Office: 498 Days
• Field of Search: 250/211 R, 250/211 J, 250/432-438, 250/207, 313/523, 313/532, 313/538, 313/539
• US Class Current: 250/214.1
• CPC Class Codes: H01T 2/00 Spark gaps comprising auxiliary triggering means triggering circuits H01T15/00

Abstract

The invention disclosed herein includes a low pressure, light initiated, glow discharge switch for high power application. The switch is comprised of an insulating envelope formed into a cylindrical shape having conductive plates at each end. Contained within the envelope is a cathode cup and an anode cup. Each of the cups has a plate at one end which defines two central apertures. The central apertures are positioned opposite one another a short distance apart and centrally axially aligned. A quartz window at the lower end of the cathode cup defines a visual opening to allow unfocused high energy electromagnetic radiation (UV light) to be shined upon the back side of the cathode plate. When UV light is presented to the back of the cathode plate, a photoemissive mechanism is initiated which causes an avalanche effect in the gas-filled chamber of the switch which leads to the discharge of current across the gap between the anode and cathode allowing the switch to close. A system includes the electronic switch is also disclosed which may be used to trigger a high energy flash lamp or excimer laser, as well as other high power applications. A system for controlling the flow of gas into the chamber defined by the envelope of the electronic switch is also disclosed.

Claims

1. A high powered electronic switch, capable of providing a high stand-off voltage, comprising:

a cylindrical anode cup having a bottom plate having a first aperture;

a cylindrical cathode cup having a top plate having a second aperture;

said anode and cathode cups having juxtaposed anode bottom plate to cathode top plate, and being separated by a small gap wherein said first and second apertures are in substantial alignment;

envelope means for hermetically sealing said anode and cathode cups;

ionizable material within said envelope;

means for directing unfocused light toward said apertures, of a sufficiently short wavelength to trigger the flow and discharge of high amperage current across the gap between said top and bottom plates.

2. The high powered gas-filled electronic switch of claim 1, wherein said means for directing unfocused light includes an unfocused laser directed at a quartz window capable of transmitting electromagnetic waves of a wavelength of 308 nm.

3. The high powered gas-filled electronic switch of claim 1, wherein said means for directing unfocused light provides said high amperage current which flows across the gap includes a high current density plasma operating in the pseudospark range of the Paschen curve.

4. The high powered gas-filled electronic switch of claim 1, wherein the envelope of said electronic switch is filled with helium gas at a pressure within the range of 0.1-0.5 Torr.

5. The high powered gas-filled electronic switch of claim 1 wherein photoemission of electrons from the back of the cathode cup, caused by a directed unfocused laser beam, results in the discharge of high amperage current across the gap between said top and bottom plates.

6. A system for triggering a high energy load, such as a laser, comprising:

an electronic switch having an anode cup and a cathode cup;

means for storing electrical energy;

a high voltage source operatively associated with the anode cup of the electronic switch;

said high voltage source associated with said switch through the electrical energy storage means;

said electronic switch comprising;

said anode cup and said cathode cup each having at least a single plate positioned at one end, each plate defining an aperture, said apertures being substantially aligned;

envelope means for hermetically sealing said anode and cathode cups;

means for directing unfocused light toward said apertures of a sufficiently short wavelength at the back of the cathode top plate to trigger flow and discharge of high amperage current across the gap between the respective plates of the anode and cathode; and

means for controlling the flow of gas into said switch, so that said switch operates on the left side of the Paschen curve, whereby when light is applied, the electronic switch is closed and the electrical energy storage means applies a pulse of electrical energy to said load.

7. The system for triggering a high energy load of claim 6 wherein said means for controlling the flow of gas into the envelope defining the switch includes controllable operable gas valves and a capacitive manometer for monitoring the pressure levels contained within the vessels into which gas is allowed to flow.

8. The system of claim 6 for triggering a high energy load wherein said means for storing electrical energy comprises:

a pulse forming network, including a high storage capacitor,

so that said capacitor may discharge through said electronic switch when the switch is closed and may be recharged once fully discharged so as to bring the anode of the electronic switch back to a sufficient stand-off voltage to reopen the switch for further and repeated activation;

where said capacitor is electrically isolated from said unfocused light.

9. A gas filled electronic switch, exhibiting high standoff voltage characteristics, for high power application, comprising:

an elongated, hermetically-sealed, high dielectric constant material envelope, said envelope being filled with ionizable material at a relatively low pressure;

a pair of metallic, conductive cups, positioned bottom to bottom;

each of said cups being cylindrical with flat bottom plates, said plates defining a pair of apertures;

said cups being mounted substantially coaxially within said envelope and separated by a small gap, the distance of which is comparable to the diameter of said central apertures;

means for applying a high voltage between said two cups;

means for operating said electronic switch at a low pressure to maintain a high standoff voltage in the absence of a trigger;

said switch being thermally and electrically isolated from a triggering means.

10. The gas filled electronic switch of claim 9, further including:

a thermally and electrically isolated triggering means, comprising;

a high frequency electromagnetic radiation source means;

said source means producing an unfocused light beam on the backside of said cathode;

whereby, said electronic switch is triggered.

11. The gas-filled electronic switch of claim 10, wherein said radiation source is:

an unfocused laser producing electromagnetic radiation of a wavelength of 308 nm or less.

12. The gas-filled electronic switch of claim 9, wherein said gas filling said envelope is helium at a pressure of 0.1-0.5 Torr, so that said switch operates during voltage standoff at the left side of the Paschen curve.