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LCLS-XTOD Gas Attenuator

LCLS-XTOD Gas Attenuator. LCLS FAC Meeting October 27, 2005 Stewart Shen, Keith Kishiyama and Marty Roeben. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

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LCLS-XTOD Gas Attenuator

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  1. LCLS-XTOD Gas Attenuator LCLS FAC Meeting October 27, 2005 Stewart Shen, Keith Kishiyama and Marty Roeben This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  2. Contents • Requirements • Passive Pumping Design • Performance Analysis • Prototype Plan • Project Schedule • Conclusions

  3. Physics Requirements • Be able to reduce the FEL beam intensity by up to 4 orders of magnitude at any energy within the design range (0.8 to 2 keV) • Provide stable, reproducible (to within 1%) attenuation for repeated FEL shots. Implied Requirements Provide matched boundary vacuum conditions

  4. Use gas to attenuate below 2 keV Solid Attenuator Gas Attenuator Autocad Use Gas Use Solids * For a transmission of 10-4

  5. Argon and Nitrogen for 104 Attenuation* * Based on NIST X-Ray Form Factor, Attenuation, Scattering Tables

  6. Nitrogen Pressure Requirements

  7. 100-cm Design*

  8. Passive System Design Physical Variables Chamber Length (3-7.5 m) Overall Length (< 10 m) Aperture (3 mm – 5 mm) # of ports (4- 6)

  9. Design Consideration – Critical Parameters • Chamber Length • Overall Length • Pumping (Turbo & Roughing L/s) • Chamber Pressure • Injected Gas (sccm) • Boundary Vacuum Pressure

  10. Gas Attenuator Differential Pumping Configurations -Full Scale

  11. 10-m 6 port 3-mm Aperture 720 L/s Qi = 0 sccm Pump Down • Final outgassing rates of • 10-9 T-L/s-cm2 is assumed • Scroll Pump Speed vs Pressure • is modeled • Turbo Pump Speed vs Pressure • is modeled

  12. Turbo Pumping Speed Modeling Scroll (Roughing) Pumping Speed Modeling

  13. 6 port 3-mm Aperture 720 L/s Qi = 5053 sccm Normal Operation with N2 Injection

  14. 6 port 3-mm Aperture 720 L/s Qi = 5053 sccm Normal Operation with N2 Injection 15.24 Torr 1.5x10-6 Torr

  15. PrototypeGas Attenuator Differential Pumping - Passive 3-Port Objectives Configuration Phase 1 Demonstrate stable control of gas chamber pressure Validate the vacuum design for intermediate flow Verify mechanical & thermal stability Phase 2 (Optional) Demonstrate stable control of gas chamber pressure Calibrate the Ion Chamber Validate the intensity attenuation

  16. System ConfigurationPhase-1 Gas Chamber Turbo Scroll Port 1,2,3

  17. X-Ray Source Requirements • Within the range of 0.8 – 2 keV • Characteristic Beam • Collimated • Accessible (on site)

  18. Soft X-Ray Source @ Bldg. 179 Technical Contact: Jim Emig (NTED) Max 10 kV with Be window (~1 mA) Available after October 05 Power Supply & Vacuum Control

  19. 2 Views of System with X-ray SourcePhase 2

  20. LLNL Vacuum Laboratory Building 132 S RM 1571

  21. Prototype System Major Parameters

  22. Vacuum Modeling- Pump Down • Final outgassing rates of • 10-9 T-L/s-cm2 is assumed • Scroll Pump Speed vs Pressure • is modeled • Turbo Pump Speed vs Pressure • is modeled

  23. Vacuum Modeling- Gas Injection

  24. Vacuum Modeling- Normal Operation with injected N2 gas

  25. Prototype Testing Program • Facility Ready (132S RM 1571) • IWS Approved (IWS #12599) • Test Plan prepared • Engineering drawings being prepared • QA Plan prepared

  26. Mass Flow Control MKS Type 649 Electronic Pressure Controller • Fully integrated baratron, mass flow meter, normally closed proportioning • control valve and closed loop proportional/integral control electronics • Flows to 5000 sccm • Pressure control + 0.2% of full scale • Time response – 1 sec (excluding system time constants)

  27. Gas Attenuator Design Schedule

  28. Gas Attenuator Procurement/Installation Schedule

  29. Conclusions • Gas Attenuator preliminary design is near its completion • Prototype design completed and hardware procurement started • Project is on schedule

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