Hollow cathode plasma switch with magnetic field

Claim 2

A low forward-voltage drop, high current plasma switch, comprising: a hollow cathode for emitting electrons to form a plasma, an anode spaced from the hollow cathode for receiving current from the hollow cathode through the plasma when the switch is on, a control electrode between the hollow cathode and the anode for controlling the reach of the plasma from the hollow cathode towards the anode, said control electrode including a plasma passageway which is larger than the area of the plasma at the control electrode for plasma currents above a threshold current level, and means for forming a diverging magnetic field between the hollow cathode and the control electrode to expand the spread of the plasma at said passageway for plasma currents above said threshold level.

Claim 3

The plasma switch of claim 1, wherein the magnetic field strength is at least about 150 gauss.

Claim 4

The plasma switch of claim 2, further comprising a pressure housing enclosing said switch, and an ionizable gas within said pressure housing, said pressure housing maintaining said gas at a pressure less than about 0.1 torr.

Claim 5

The plasma switch of claim 3, wherein the magnetic field strength and gas pressure are on the order of 200 gauss and 0.06 torr, respectively.

Claim 6

The plasma switch of claim 4, wherein said control electrode is spaced on the order of 2-5 cm. from said hollow cathode.

Claim 7

The plasma switch of claim 4, wherein the plasma current density is maintained at less than about 3.5 amps/cmz

Claim 8

The plasma switch of claim 1, said control electrode passageway comprising a mesh having a mesh aperture size of not more than about 0.3 mm.

Claim 9

The plasma switch of claim 7, wherein said mesh aperture size is not more than about 0.075 mm.

Claim 10

The plasma switch of claim 1, said control electrode passageway comprising a mesh, the aperture size of said mesh and the plasma current density at the passageway being selected to keep the control electrode interrupt voltage necessary to interrupt the flow of switch current at not more than about 50 volts.

Claim 11

The plasma switch of claim 1, further comprising a truncated conical keeper between the hollow cathode and the control electrode for maintaining a plasma in the vicinity of the hollow cathode, said keeper having an opening in its truncated portion for the passage of plasma between said hollow cathode and said control electrode.

Claim 12

A low forward-voltage drop, high current plasma switch system, comprising: a pressure housing, an ionizable gas within said housing, a hollow cathode within said housing for emitting electrons to form a plasma from said gas, an anode spaced within said housing from the hollow cathode for receiving current from the hollow cathode through the plasma, a control electrode within the housing between the hollow cathode and the anode for controlling the reach of plasma from the hollow cathode to the anode, said control electrode including a plasma passageway, means for applying control voltage signals to said control electrode for initiating and interrupting the flow of current through said plasma between the hollow cathode and the anode, means for forming a diverging magnetic field within the housing to spread said plasma across said passageway, and means setting the pressure within said housing at a level that establishes a rounded plasma electron density distribution plot across said passageway.

Claim 13

A low forward-voltage drop, high current plasma switch system, comprising: a pressure housing, an ionizable gas within said housing, a hollow cathode within said housing for emitting electrons to form a plasma from said gas, an anode spaced within said housing from the hollow cathode for receiving current from the hollow cathode through the plasma, a control electrode within the housing between the hollow cathode and the anode for controlling the reach of plasma from the hollow cathode to the anode, said control electrode including a plasma passageway, means for applying control voltage signals to said control electrode for initiating and interrupting the flow of current through said plasma between the hollow cathode and the anode, means for forming a diverging magnetic field within the housing to spread said plasma across said passageway, and means setting the pressure within said housing at a level that establishes a rounded plasma electron density distribution plot across said passageway.

Claim 14

The plasma switch system of claim 11, wherein said pressure setting means sets the pressure within said housing at no more than about 0.1 torr.

Claim 15

The plasma switch system of claim 12, wherein the magnetic field strength is at least about 150 gauss.

Claim 16

The plasma switch system of claim 13, wherein the magnetic field strength and gas pressure within said housing are on the order of 200 gauss and 0.06 torr, respectively.

Claim 17

The plasma switch system of claim 14, wherein the plasma current density at said control gate electrode passageway is maintained at less than about 3.5 amps/cm 2 .

Claim 18

The plasma switch system of claim 12, wherein said control electrode is spaced on the order of 2-5 cm. from said hollow cathode.

Claim 19

The plasma switch system of claim 11, said control electrode passageway comprising a mesh having a mesh aperture size of not more than about 0.3 mm.

Claim 20

The plasma switch of claim 17, wherein said mesh aperture size is not more than about 0.075 mm.

Claim 21

The plasma switch of claim 11, said control electrode passageway comprising a mesh, the aperture size of said mesh and the plasma current density at the passageway being selected to keep the control electrode interrupt voltage necessary to interrupt the flow of switch current at not mor than about 50 volts.

Claim 22

The plasma switch of claim 11, further comprising a truncated conical keeper between the hollow cathode and the control electrode for maintaining a plasma in the vicinity of the hollow cathode, said keeper having an opening in its truncated portion for the passage of plasma between said hollow cathode and said control electrode.

Claim 25

The method of claim 21, wherein the magnetic field strength is at least about 150 gauss.

Claim 26

The method of claim 22, wherein said plasma is formed from a gas that is maintained at a pressure less than about 0.1 torr.

Claim 27

The method of claim 23, wherein the magnetic field strength and gas pressure are on the order of 200 gauss and 0.06 torr, respectively.

Claim 28

The method of claim 24, wherein the reach of said plasma between said hollow cathode and anode is controlled applying a voltage to a control electrode positioned between the hollow cathode and anode on the order of 3-4 cm. from the hollow cathode, said control electrode including a plasma passageway.