# US 2014/0152175 A1 · Photocathode enhancement system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152175 A1 - Document ID: US20140152175A1 - Status: Published application - Kind: A1 - Application number: 13/691,708 - 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/US20140152175A1 ## CPC - H01J 1/34: Photo-emissive cathodes (H01J1/35 takes precedence) - H01J 1/88: Mounting, supporting, spacing, or insulating of electrodes or of electrode assemblies - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A photocathode enhancement system includes a cathode plate that is movably positioned relative to an incident optical beam. The emission surface of the cathode plate has an area between about 0.5 cm2 to greater than 100 cm2. The system includes a motion controller that is configured to control the movement of the cathode plate relative to the optical beam, so that the optical beam successively strikes non-overlapping portions of the emission surface, and may reach substantially the entire emission surface over a time period of about 10 seconds to about 100 seconds. The movement of the cathode plate is controlled so that on average, the heat from the optical beam is uniformly distributed over the emission surface of the cathode plate. ## Claims ### Claim 1 A system comprising: a photocathode having a cathode plate movably positioned relative to an incident optical beam, wherein the cathode plate has an emission surface of an area between about 0.5 cm2 to about 100 cm2; and a motion controller configured to control movement of the cathode plate relative to the optical beam, so that the optical beam successively strikes non-overlapping portions of the emission surface. ### Claim 2 (depends on 1) The system of claim 1, wherein the area of the emission surface of the cathode plate is greater than 100 cm2. ### Claim 3 (depends on 1) The system of claim 1, wherein the motion controller is further configured to control movement of the cathode plate so that the optical beam reaches substantially the entire emission surface over a time period. ### Claim 4 (depends on 3) The system of claim 3, wherein the time period is between about 10 to about 100 seconds. ### Claim 5 (depends on 1) The system of claim 1, wherein the optical beam comprises a laser beam. ### Claim 6 (depends on 2) The system of claim 2, wherein charge lifetime QT of the photocathode is between 20,000 C and 100,000 C. ### Claim 7 (depends on 1) The system of claim 1, wherein the motion controller is configured to control the movement of the cathode plate so that on average, heat from the optical beam is uniformly distributed over the emission surface of the cathode plate. ### Claim 8 (depends on 1) The system of claim 1, wherein the movement of the cathode plate has a speed between about 1 cm/sec to about 10 cm/sec. ### Claim 9 (depends on 1) The system of claim 1, wherein the movement of the cathode plate is one of: a curvilinear motion; a rectilinear motion; and a combination of curvilinear and rectilinear motions. ### Claim 10 (depends on 1) The system of claim 1, further comprising an UHV (ultra-high-vacuum) bellow and an insulator pillar mounted on a flange of the UHV bellow, wherein the insulator pillar is configured to support the cathode plate. ### Claim 11 (depends on 10) The system of claim 10, wherein the motion controller is further configured to control the motion of the flange of the UHV bellow. ### Claim 12 (depends on 1) The system of claim 1, further comprising a cathode electrode electrically coupled to the cathode plate and separated from the cathode plate by a cathode gap. ### Claim 13 (depends on 12) The system of claim 12, wherein the cathode plate is transversely movable relative to the cathode electrode. ### Claim 14 (depends on 12) The system of claim 12, wherein the anode and the cathode electrode are separated by an accelerating gap, and wherein the accelerating gap has a width of about 2 cm to about 6 cm. ### Claim 15 (depends on 1) The system of claim 1, wherein the laser beam has a spot size of about 2 mm to about 10 mm in diameter, and wherein the sweep time on one or more points on the emission surface of the cathode plate during a sweep cycle is less than about 200 ms. ### Claim 16 (depends on 12) The system of claim 12, wherein the cathode electrode is supported by a HV (high voltage) feedthrough, and further comprising an optics assembly configured to guide the electron beam emitted from the cathode electrode. ### Claim 17 (depends on 11) The system of claim 11, wherein the motion controller comprises a motion confinement system configured to keep the cathode gap and the accelerating gap substantially constant in width, during operation of the system. ### Claim 18 (depends on 1) The system of claim 1, further comprising a laser feedback system configured to correct for uneven QE (quantum efficiency) distribution. ### Claim 19 (depends on 1) The system of claim 1, wherein the motion controller comprises a processing system, and wherein the processing system includes a computer-usable medium having stored therein computer-readable instructions, wherein said instructions when executed by said processing system cause the processing system to control movement of the cathode plate relative to the optical beam so that the optical beam successively strikes non-overlapping portions of the emission surface. ### Claim 20 (depends on 1) The system of claim 1, wherein the cathode plate comprises a plurality of discrete components. ### Claim 21 A method comprising: movably positioning a cathode plate of a photocathode relative to an incident optical beam, wherein the cathode plate has an emission surface between about 0.5 cm2 and about 100 cm2; and controlling movement of the cathode plate relative to the optical beam so that the optical beam successively strikes non-overlapping portions of the emission surface. ### Claim 22 (depends on 21) The method of claim 21, wherein the emission surface is great than 100 cm2. ### Claim 23 (depends on 21) The method of claim 21, wherein the act of controlling movement of the cathode plate comprises controlling the movement of the cathode plate so that the optical beam reaches substantially the entire emission surface over a time period, thereby increasing a charge lifetime QT of the photocathode. ### Claim 24 (depends on 23) The method of claim 23, wherein the time period is between about 10 to about 100 seconds, and wherein the optical beam comprises a laser beam. ### Claim 25 (depends on 23) The method of claim 23, wherein the charge lifetime QT of the photocathode is increased to at least 100,000 C, and wherein electron beams emitted by the photocathode in response to the optical beam are unpolarized. ### Claim 26 (depends on 21) The method of claim 21, wherein the act of controlling movement of the cathode plate comprises controlling the movement of the cathode plate so that heat from the optical beam is, on average, uniformly distributed over the emission surface of the cathode plate.