1 / 20

RF Gun Status LCLS Facility Advisory Committee Meeting October 26, 2005

RF Gun Status LCLS Facility Advisory Committee Meeting October 26, 2005. Mechanical design review (08/05) Commissioning plan Cathode development Response to FAC recommendations. RF Gun Mechanical Design Review. Presentation of mechanical design with RF and thermal simulations.

vbard
Download Presentation

RF Gun Status LCLS Facility Advisory Committee Meeting October 26, 2005

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. RF Gun StatusLCLS Facility Advisory Committee MeetingOctober 26, 2005 Mechanical design review (08/05) Commissioning plan Cathode development Response to FAC recommendations

  2. RF Gun Mechanical Design Review • Presentation of mechanical design with RF and thermal simulations. • Mechanical design commended by review committee. • Concerns • Heating at cathode/gun RF joint and coupler irises. • Damage from high flow in cooling channels. • Recommendations • Improve cooling design. • RF reflection in waveguide pumping slots acceptable. • Make two guns with tree sets of parts. • Start load lock development program. • Response • Water flow rate lowered. • Radii on ports increased to limit pulse heating. • Cathode plate thickened.

  3. Gun and Solenoid Courtesy of E. Jongewaard

  4. Water Flow Velocity Reduction Courtesy of E. Jongewaard

  5. Gun Commissioning Schedule • Fabrication - 01/06 • Scheduled in SLAC Klystron department. • Cold test - 04/06 • Characterize gun. • Bead pull/drop measurement (use dummy cathode?). • Cathode plate tuning with 1st cathode. • Cathode preparation - 06/06 • Characterize 2nd cathode. • QE measurement, H+ ion cleaning. • Measure surface roughness & contaminants. • Gun & Solenoid integration - 06/06 • Assemble on common girder. • Magnetic measurement with dummy cathode. • Install cleaned 2nd cathode and retune. • Hot test - 08/06 • Details follow. • Installation & commissioning at S20 - 12/06 • See next presentation.

  6. RF Gun Preparation • Part of injector commissioning schedule

  7. Gun Hot Test • Objectives • Vacuum bake to 10-10 Torr. • Stable 120 MV/m operation. • Demonstrate 130 MV/m. • Demonstrate 120 Hz operation (3.5 kW thermal load). • Measure thermal distribution with low & high RF power. • Measure Cell field balance at high RF power. • Procedure • Install assembly in Klystron department and bake. • RF processing. • Full characterization. • Test temperature control?

  8. Gun Hot Test Setup • Hardware from GTF • YAG/FC • Solenoid power supply • Thermal management • Cooling without temperature feedback • Track RF frequency with gun temperature • Controls • LLRF • Parameter logging • Algorithm for automatic processing Pump Gun Valve YAG/FC To Klystron Wave Guide Solenoid Pump

  9. Measurements for Gun Conditioning • Gun temperatures (RTD’s) • W/G and FC vacuum pressure • Klystron drive power • Gun forward/reflected power • Half and full cell probes • Dark current in FC • Image of dark current (YAG) • RF breakdowns

  10. Open Issues • Hot test schedule and location • PEP test bunker in Klystron Department • Available 08/06 • Sector 20 • Before, during, or after 2006 downtime (08/06-11/06) • More details in next presentation • Cooling water for gun • Stand alone 4 kW chiller? • Use facility water?

  11. Cathode Development* • Presently no process to improve and control QE of LCLS cathodes. • No load lock in LCLS budget. • Need for improved cathode installation procedure. • Operational contamination requires in-situ cleaning. • Avoid risky gun baking and laser cleaning *Courtesy of D. Dowell

  12. In-Situ Cleaning Methods • H-beam cleaning • Use ~1keV H-beam. • Cleans 1cm diameter area. • Requires no reconfiguration of gun system. • Benign to cathode surface. • H-plasma cleaning • Produce plasma inside gun volume. • Plasma excitation with RF • Only cleans region of high E-field. • Plasma excitation with DC • Only cleans region near electrodes.

  13. H-ion Gun Gun Solenoid LCLS Min QE 2x10-5 at 255 nm Valve H-Beam Cleaning Results & Installation on Gun Experimental results from SLAC Physical Electronics Lab See D. Dowell et al., FEL2005 Conf.

  14. Proposed Three Step Plan • Compare cathode surface processing with H+-beam vs. H+-plasma. • Find best procedure to clean, transfer, and install cathodes for LCLS gun 1. • Develop in-situ cleaner for LCLS gun 2. • Thermal emittance measurement not part of this plan.

  15. Laboratory Test (Part 1) • Goals • Comparison of H-beam and H-plasma cleaning. • Find optimum materials and fabrication techniques. • Simulation of cathode transfer and installation effects. • Compare with theory. • Plan • Testing of small samples in SLAC PE lab. • Uses existing surface diagnostics equipment. • Construct H-plasma cleaner. • Result • Capability for H-beam and H-plasma cleaning & measured data.

  16. Cathode Cleaning and GTF Test (Part 2) • Goals • Test robustness of cleaned cathodes for installation procedure and improve procedure for LCLS. • Quantify effect of gun bake on QE. • Plan • Characterization and H-beam cleaning of GTF cathodes in SLAC PE lab. • Transfer and test cathodes in GTF gun. • Compare lab QE measurement with operational QE. • Result • Improved procedure for installing well characterized, clean LCLS cathodes.

  17. In Situ Cleaning for LCLS Gun 2 (Part 3) • Goals • Design and build cleaner system for LCLS Gun 2. • Find operating parameters for H+ source. • Plasma cleaning with RF, compare with bake. • Plan • Install and test system on existing chamber in PE lab. • Move system to LCLS Gun 2 and test. • Test with RF? • Result • Complete gun assembly with cleaner ready for installation at Sector 20.

  18. Funding Status • BCR requested for part 1. • BCR in preparation for part 2. • Request for part 3 when results from parts 1 and 2 available.

  19. Response to FAC Recommendations • Completion of second gun encouraged. • Fabrication of second gun scheduled with first gun. Will be available as complete system with solenoid as fast backup at sector 20. • Investigate gun wake field effects. • Large energy spread in GTF gun contributed to pi-0 mode beating. Should not occur in LCLS gun with 15 MHz mode separation. PIC simulations planned for next year. • Continue effort on H+ ion cleaning of cathode. • Budget modified to pursue cleaning and test on second gun. • Develop permanent facility for gun testing. • No decision made yet, but funding for GTF continued through FY2006.

  20. Summary • Gun mechanical design completed. • Fabrication of gun scheduled. • Commissioning plan in progress. • Funding for cathode development underway.

More Related