Patent Number: 
Section: claims

1. An extreme ultraviolet light source in which a magnetically self-confined plasma is produced via a pulsed discharge and subsequently the plasma energy in a small region of the plasma is increased by absorption of laser light resulting in locally increased excitation of ionic species that radiate extreme ultraviolet light, wherein a direction of current flow is reversed on successive pulses. 2. A source as in claim 1, in which an axial static magnetic field is applied to guide a coaxial discharge between opposed open-ended heat pipes and the laser impinges radially onto the discharge plasma. 3. A source as in claim 2, in which ignition of the discharge is assisted by a potential applied to a disc electrode located symmetrically between the main discharge electrodes, with a central hole through which the discharge passes. 4. A source as in claim 3, in which lithium is confined within a buffer gas heat pipe formed by the electrodes and the central disc with wide angle vapor containment and reflux. 5. A source as in claim 1, in which each phase of the discharge comprises a quiescent low current period followed by a high current period of shorter duration that pinches the plasma and increases its density and temperature in preparation for laser heating. 6. A source as in claim 5, in which the low current ranges from 1 Amp to 100 Amp and the high current ranges from 100 Amp to 10 kAmp. 7. A source as in claim 5, in which the quiescent period has a duration between 5 μsec and 50 μsec and the high current period has a duration between 500 nsec and 5 μsec. 8. An extreme ultraviolet light source at 13.5 nm based on the emission of lithium ions in which a magnetically self-confined lithium plasma of electron density less than 1019 cm−3 is produced via a pulsed discharge and subsequently the plasma energy in a small region of the plasma is increased by absorption of laser light at the carbon dioxide laser wavelength, resulting in locally increased excitation of hydrogen-like lithium to its resonance level and increased radiation at 13.5 nm, wherein a direction of current flow is reversed on successive pulses. 9. A source as in claim 8, in which an axial static magnetic field is applied to guide a coaxial discharge between opposed open-ended lithium heat pipes and the carbon dioxide laser impinges radially onto the discharge plasma. 10. A source as in claim 8, in which the lithium is confined within a buffer gas heat pipe with wide angle vapor containment and reflux. 11. A source as in claim 8, in which a Z-pinch discharge provides the magnetically self-confined lithium volume for the purpose of increasing the lithium ion density and creating a plasma density greater than 1017 electrons per cm3 at an electron temperature exceeding five electron volts. 12. A source as in claim 8, in which a hypocycloidal pinch discharge geometry is applied to the production of a lithium plasma density greater than 1017 electrons per cm3 at an electron temperature exceeding five electron volts.