Hollow cathode plasma switch with magnetic field
AssigneeHughes Aircraft Company
InventorsDan M. Goebel, Robert L. Poeschel, Robert W. Schumacher, Julius Hyman, Jr.
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Abstract
A diverging magnetic field is established between the cathode and control electrode of a hollow cathode plasma switch to expand the plasma at a passageway through the control electrode, thus significantly increasing the switch's current handling capability. Preferred ranges of magnetic field strength, gas pressure, spacing between the hollow cathode and control electrode, and the mesh aperture size for the control grid are described.
Claims25
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.
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.
A method of switching an electrical circuit, comprising:
- providing a pair of switch terminals in said electrical circuit to close the circuit when the terminals are electrically connected, and to open the circuit when the terminals are electrically disconnected,
- establishing a plasma from a hollow cathode connected to one of said terminals,
- controlling the reach of said plasma from said hollow cathode towards an anode connected to the other of said switch terminals to respectively close and open the circuit when the plasma does and does not reach all the way from said hollow cathode to said anode, the cross-sectional area of said plasma at the anode being constricted above a threshold plasma current level to limit its current interruption capacity, and
- applying a diverging magnetic field to expand the spread of said plasma between said hollow cathode and said anode, and thereby increase its current interruption capacity.
Dependencies are inferred from the claim text.