# US 2014/0152176 A1 · Multi-dimensional photocathode system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152176 A1 - Document ID: US20140152176A1 - Status: Published application - Kind: A1 - Application number: 13/691,721 - Filed: 2012-11-30 - Published: 2014-06-05 - Earliest claimed: 2012-11-30 - Assignees: FAR-TECH, Inc. - Applicants: FAR-TECH, Inc. - Inventors: Xiangyun CHANG - Web page: https://patentgrep.com/patent/US20140152176A1 ## CPC - H01J 1/34: Photo-emissive cathodes (H01J1/35 takes precedence) - H01J 25/10: Klystrons, i.e. tubes having two or more resonators, without reflection of the electron stream, and in which the stream is modulated mainly by velocity in the zone of the input resonator - H05H 2007/084: {Electron sources} - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - H05H: PLASMA TECHNIQUE (apparatus or processes specially adapted for producing X-rays H05G2/00); PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS ## Abstract A photocathode system includes a plurality of photocathodes, and at least one combining device. The photocathodes have individually adjustable voltages, and each photocathode generates an individual electron bunch at an emission period. The combining device combines the individual electron bunches, generated at each emission period, into a combined bunch along a combined axis. The timing of the individual electron bunches is independently adjustable, so that an electron bunch with a lower energy arrives at the combined axis earlier in time compared to another electron bunch with a higher energy, thereby allowing the combined beam of electron bunches to be longitudinally compressed. The photocathodes may be distributed along a 1D column, or a 2D array, or a 3D array, or any arbitrary configuration. A linac is located near a longitudinal focusing point to boost beam energy and therefore freeze bunch length and emittance. ## Claims ### Claim 1 A photocathode system comprising: a plurality N of photocathodes, each photocathode configured to generate an individual electron bunch at an emission period; and at least one combining device configured to combine the individual electron bunches, generated at each emission period, into a combined bunch along a combined axis; wherein timing of the individual electron bunches is independently adjustable, so that an electron bunch with a lower energy arrives at the combined axis earlier in time compared to another electron bunch with a higher energy, thereby allowing the combined beam of electron bunches to be longitudinally compressed. ### Claim 2 (depends on 1) The photocathode system of claim 1, wherein the photocathodes have independently adjustable voltages, and wherein the longitudinal compression of the combined bunch of electron occurs from energy differences between the individual electron bunches. ### Claim 3 (depends on 1) The photocathode system of claim 1, wherein the combining device is configured to bring together the individual electron bunches through ideal linear transport lines so as to combine the individual electron bunches. ### Claim 4 (depends on 1) The photocathode system of claim 1, wherein the combining device is configured to combine one or more static fields at a plurality of locations. ### Claim 5 (depends on 4) The photocathode system of claim 4, wherein the static fields comprise at least one of: a static magnetic field; and a static electric field. ### Claim 6 (depends on 1) The photocathode system of claim 1, further comprising a linac configured to provide an acceleration for the electron bunches so as to freeze their relative longitudinal motions and their transverse emittances. ### Claim 7 (depends on 1) The photocathode system of claim 1, wherein the photocathodes are disposed along a 1D (one-dimensional) column. ### Claim 8 (depends on 7) The photocathode system of claim 7, wherein the photocathodes are evenly distributed along the column. ### Claim 9 (depends on 1) The photocathode system of claim 1, further comprising a static field bending component between the plurality of photocathodes and the combining device, the static field bending component configured to bend the individual electron bunches toward the combining device by applying a static field. ### Claim 10 (depends on 9) The photocathode system of claim 9, wherein the static field comprises one of: a static magnetic field; and a static electric field. ### Claim 11 (depends on 1) The photocathode system of claim 1, wherein the energies of each electron bunch are individually adjustable so that the electron bunches self-compress without need for additional energy modification. ### Claim 12 (depends on 1) The photocathode system of claim 1, wherein the electron bunches are matched near a longitudinal focusing point of the combined bunch, so that the emittance of the combined bunch is minimized and is less than the emittance of the highest emittance individual sub-bunch. ### Claim 13 (depends on 1) The photocathode system of claim 1, wherein the N photocathodes are disposed along an n×m two dimensional (2D) array having n rows and m columns, and wherein N=n×m. ### Claim 14 (depends on 1) The photocathode system of claim 1, wherein the at least one combining device comprises: a vertical combination component and a horizontal combination component. ### Claim 15 (depends on 14) The photocathode system of claim 14, further comprising a transition component between the vertical combination component and the horizontal combination component, the transition component configured to match the different energies of the electron bunches that enter the vertical combination component at the same position. ### Claim 16 (depends on 1) The photocathode system of claim 1, wherein the photocathodes are disposed along a three-dimensional (3D) array. ### Claim 17 (depends on 1) The photocathode system of claim 1 wherein charge lifetime of the system is N times QTF, where QTF represents the charge lifetime of a single one of the photocathodes, and has a value of about 1000 C when electron beams emitted by the photocathodes are non-polarized, and 200 C when electron beams emitted by the photocathodes are polarized. ### Claim 18 A method comprising: generating individual electron bunches from each one of a plurality N of photocathodes, at a respective emission period; combining the individual electron bunches, generated at each emission period, into a combined bunch along a single combined axis; and adjusting the timing of the individual electron bunches, so that an electron bunch with a lower energy arrives at the combined axis earlier in time compared to another electron bunch with a higher energy, thereby allowing the combined beam of electron bunches to be longitudinally compressed. ### Claim 19 (depends on 18) The method of claim 18, wherein the act of combining the individual electron bunches comprises bringing together the individual electron bunches along ideal linear transport lines.