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A multiple electron beam source comprises a photon source to generate a photon beam, a lens to focus the photon beam, a photocathode having a photon receiving surface and an electron emitting surface, and an array of electron transmission gates spaced apart from the electron emitting surface of the

A multiple electron beam source comprises a photon source to generate a photon beam, a lens to focus the photon beam, a photocathode having a photon receiving surface and an electron emitting surface, and an array of electron transmission gates spaced apart from the electron emitting surface of the photocathode by a distance dg. In one version, the multiple electron beam source comprises a photocathode stage assembly to move the photocathode relative to the array of electron transmission gates. In one version, the multiple electron beam source also comprises a plasmon-generating photon transmission plate comprising an array of photon transmission apertures and exterior surfaces capable of supporting plasmons.

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What is claimed is: 1. A multiple electron beam source comprising: (a) a photocathode comprising a photon receiving surface to receive a photon beam and an electron emitting surface to emit electrons; and (b) an array of electron transmission gates having a surface facing the electron emitting surf

What is claimed is: 1. A multiple electron beam source comprising: (a) a photocathode comprising a photon receiving surface to receive a photon beam and an electron emitting surface to emit electrons; and (b) an array of electron transmission gates having a surface facing the electron emitting surface of the photocathode, the surface of the array of electron transmission gates spaced apart from the electron emitting surface of the photocathode by a separation distance dg, each electron transmission gate comprising: (i) a membrane having opposing first and second surfaces; (ii) an anode on the first surface of the membrane; (iii) an insulator on the second surface of the membrane; (iv) an aperture through the anode, insulator and membrane; and (v) a gate electrode on the insulator, the gate electrode positioned about the aperture, the gate electrode capable of receiving a gate control voltage that controls the transmission of electrons emitted from the photocathode through that electron transmission gate. 2. A multiple electron beam source according to claim 1 comprising a photocathode stage assembly to move the photocathode relative to the array of electron transmission gates. 3. A multiple electron beam source according to claim 2 wherein the photocathode stage assembly comprises a flexure, a piezoelectric actuator and a position sensor. 4. A multiple electron beam source according to claim 1 wherein the array of electron transmission gates has periodic spacing in two dimensions. 5. A multiple electron beam source according to claim 1 wherein the gate electrode comprises gate electrode segments which are independently electrically addressable. 6. A multiple electron beam source according to claim 1 wherein the separation distance dg is from about 10 μm to about 100 μm. 7. A multiple electron beam source according to claim 1 comprising a photon source to generate the photon beam. 8. A multiple electron beam source according to claim 1 comprising a lens to focus the photon beam. 9. A multiple electron beam source according to claim 1 wherein the membrane comprises silicon, silicon nitride, silicon carbide, diamond, boron nitride, or mixtures thereof; and the insulator comprises silicon oxide, a ceramic, an organic material, or mixtures thereof. 10. A multiple electron beam source comprising: (a) a plasmon-generating photon transmission plate capable of receiving a photon beam, the plasmon-generating photon transmission plate comprising an array of photon transmission apertures to transmit a plurality of photon beamlets and exterior surfaces capable of supporting plasmons; (b) a photocathode comprising a photon receiving surface to receive the plurality of photon beamlets and an electron emitting surface to emit electrons; and (c) an array of electron transmission gates having a surface facing the electron emitting surface of the photocathode, the surface of the array of electron transmission gates separated from the electron emitting surface of the photocathode by a separation distance dg, and each electron transmission gate capable of receiving a gate control voltage that controls the transmission of electrons emitted from the photocathode through that electron transmission gate. 11. A multiple electron beam source according to claim 10 wherein the plasmon-generating photon transmission plate has one or more spatial gratings, each spatial grating comprising a plurality of grooves concentric to a single photon transmission aperture. 12. A multiple electron beam source according to claim 10 wherein the plasmon-generating photon transmission plate comprises a transmission layer formed on a substrate, the transmission layer having the photon transmission apertures. 13. A multiple electron beam source according to claim 10 wherein each photon transmission aperture has a principal dimension d0 which is about less than or equal to the wavelength λ0 of the photon beam. 14. A multiple electron beam source according to claim 10 wherein the array of photon transmission apertures has periodic spacing in two dimensions, the period p0 of the spacing being equal in both dimensions. 15. A multiple electron beam source according to claim 10 wherein each electron transmission gate comprises: (a) a membrane having opposing first and second surfaces; (b) an anode on the first surface of the membrane; (c) an insulator on the second surface of the membrane; (d) an aperture through the anode, insulator and membrane; and (e) a gate electrode on the insulator, the gate electrode positioned about the aperture, the gate electrode capable of receiving the gate control voltage. 16. A multiple electron beam source according to claim 10 comprising a photocathode stage assembly to move the photocathode relative to the array of electron transmission gates. 17. A multiple electron beam source according to claim 16 wherein the photocathode stage assembly comprises a flexure, a piezoelectric actuator and a position sensor. 18. A multiple electron beam source according to claim 10 comprising a photon source to generate the photon beam. 19. A multiple electron beam source according to claim 10 comprising a first lens to focus the photon beam onto the plasmon-generating photon transmission plate and a second lens to focus the plurality of photon beamlets transmitted from the plasmon generating photon transmission plate onto the photocathode. 20. A multiple electron beam source comprising: (a) a plasmon-generating photon transmission plate capable of receiving a photon beam, the plasmon-generating photon transmission plate comprising an array of photon transmission apertures to transmit a plurality of photon beamlets and exterior surfaces capable of supporting plasmons; (b) an photon beam modulator capable of individually blanking each photon beamlet in the plurality of photon beamlets; (c) a photocathode comprising a photon receiving surface and an electron emitting surface, the photon receiving surface capable of receiving the plurality of photon beamlets; and (d) an array of electron transmission gates having a surface facing the electron emitting surface of the photocathode, the surface of the array of electron transmission gates spaced apart from the electron emitting surface of the photocathode by a separation distance dg, and each gate being aligned with a photo transmission aperture. 21. A multiple electron beam source according to claim 20 wherein the photon beam modulator is an acousto-optic modulator. 22. A multiple electron beam source according to claim 20 wherein the plasmon-generating photon transmission plate has one or more spatial gratings, each spatial grating comprising a plurality of grooves concentric to a single photon transmission aperture. 23. A multiple electron beam source according to claim 20 comprising a photon source to generate a photon beam. 24. A multiple electron beam source according to claim 20 comprising a first lens to focus the photon beam onto the plasmon-generating photon transmission plate and a second lens capable of receiving and focusing the plurality of photon beamlets from the photon beam modulator onto the photocathode. 25. A multiple electron beam source comprising: (a) a photocathode comprising a photon receiving surface and an electron emitting surface, the photon receiving surface capable of receiving a photon beam; (b) a plurality of arrays of electron transmission gates on the photocathode, each gate within each array having an associated gate in each of the other arrays, each electron transmission gate comprising: (i) an insulator on the electron emitting surface of the photocathode; (ii) an aperture through the insulator; and (iii) a gate electrode on the insulator, the gate electrode positioned about the aperture, the gate electrode capable of receiving a gate control voltage that controls the transmission of electrons from the photocathode through that electron transmission gate; (c) a single conducting lead electrically connecting the gate electrodes of associated gates to allow simultaneous control, with a single gate control voltage, of the transmission of electrons through associated gates; and (d) a controller comprising gate array switching capability to switch the functionality from one gate array to another gate array without switching control voltages. 26. A multiple electron beam source according to claim 25 comprising a photocathode stage assembly to move the photocathode relative to the photon source. 27. A multiple electron beam source according to claim 26 wherein the photocathode stage assembly comprises a flexure, a piezoelectric actuator and a position sensor. 28. A multiple electron beam source according to claim 25 comprising a photon source to generate the photon beam. 29. A multiple electron beam source according to claim 25 comprising a lens to focus the photon beam. 30. A gated photocathode comprising: (a) a substrate having opposing first and second surfaces; (b) a photon transmission layer on the first substrate surface comprising a photon receiving surface to receive a photon beam and an array of photon transmission apertures, the photon receiving surface comprising a plasmon-generating photon transmission layer having a spatial grating comprising a plurality of grooves concentric to a single photon transmission aperture; (c) a conducting layer on the second substrate surface; (d) an insulating layer on the conducting layer having an array of electron transmission apertures, each electron transmission aperture aligned with a photon transmission aperture; (e) a gate layer on the insulating layer comprising an array of gate electrodes, each gate electrode positioned about an electron transmission aperture and capable of receiving a gate control voltage; and (f) a photoemissive layer about the insulating layer and gate layer and at least partially extending into each electron transmission aperture, the photoemissive layer capable of emitting electrons and wherein emission of electrons from the photoemissive layer in each electron transmission gate is controlled by the gate control voltage. 31. A gated photocathode according to claim 30 wherein the photon transmission layer is a plasmon-generating photon transmission layer having surfaces capable of supporting plasmons. 32. A multiple electron beam source comprising the gated plasmon-generating photocathode of claim 30, a photon source to generate a photon beam, and a lens capable of focusing the photon beam onto the photon receiving surface. 33. A multiple electron beam source comprising: (a) a prism capable of receiving and transmitting a photon beam; (b) a photon beam modulator to modulate the photon beam transmitted by the prism and reflect a plurality of photon beamlets; (c) a photocathode comprising a photon receiving surface to receive the plurality of photon beamlets and an electron emitting surface to emit electrons; and (d) an array of electron transmission gates having a surface facing the electron emitting surface of the photocathode, the surface of the array of electron transmission gates spaced apart from the electron emitting surface and separated from the electron emitting surface by a separation distance dg, each electron transmission gate capable of receiving a gate control voltage that controls the transmission of electrons from the electron emitting surface through that electron transmission gate. 34. A multiple electron beam source according to claim 33 wherein the photon beam modulator comprises a spatial light modulator. 35. A multiple electron beam source according to claim 34 wherein the spatial light modulator comprises an array of movable mirrors. 36. A multiple electron beam source according to claim 33 wherein each electron transmission gate comprises: (a) a membrane having opposing first and second surfaces; (b) an anode on the first surface of the membrane; (c) an insulator on the second surface of the membrane; (d) an aperture through the anode, insulator and membrane; and (e) a gate electrode on the insulator, the gate electrode positioned about the aperture, the gate electrode capable of receiving the gate control voltage. 37. A multiple electron beam source according to claim 33 comprising a photocathode stage assembly to move the photocathode relative to a photon source that generates the photon beam. 38. A multiple electron beam source according to claim 37 wherein the photocathode stage assembly comprises a flexure, a piezoelectric actuator and a position sensor. 39. A multiple electron beam source according to claim 33 comprising a photon source to generate a photon beam. 40. A multiple electron beam source according to claim 34 comprising a first lens to focus the photon beam and a second lens to focus the plurality of photon beamlets reflected by the spatial light modulator.