LCLS XTOD Mechanical and Vacuum Systems; Gas Attenuator

1. LCLS XTOD Mechanical and Vacuum Systems; Gas Attenuator Lehman Review May 10-12, 2005 Pat Duffy, Mark McKernan, Donn McMahon, Stewart Shen, John Trent, Louann Tung

2. Outline Scope & Goals Systems Engineering – integrated plan Mechanical and Vacuum System Development Gas Attenuator Status Summary

3. Scope and Goals • Mechanical & Vacuum Subsystems - This includes specification, design, and procurement pumps, pipes and stands for interconnecting the experimental tanks in the FEE, Near Hall, Tunnel and Far Hall. • Gas Attenuator - The gas attenuator is a device filled with gas whose purpose is to attenuate the FEL beam especially at low photon energies. The gases under consideration are N2, Ar and Xe at pressures up to 150 Torr. The gas attenuator must be windowless because of damage and absorption issues with the FEL beam. This means that gas will leak into the beam pipe and must be differentially pumped.

4. Minor Revised Planning Better Reflects our System Engineering Approach • High Level Plans remain unchanged • DOE Level 3 Milestones will remain unchanged • Current Cost Plan will remain unchanged • Staffing plan reflects plans & goals • Lead ME for Mechanical, Vacuum, and Gas Attenuators • Vacuum systems modeling and instrumentation & control experts • Lead designer – configuration drawings and staffing detailed design • Revised approach emphasizes concurrent development of Mechanical/Vacuum systems and XTOD instrumentation • Stretch FEE Mechanical & Vacuum design completion date • Advance instrumentation development schedules • Development starts with Beam Dump and progresses down beamline

5. Treaty Flange Fixed Mask Muon Shield Gas Attenuator Solid Attenuator WFOV Camera Fast Valve Slit A Slit B PPS Configuration Drawings are Critical to Tracking Design Progress and Changes

6. Stretch FEE Completion Date but add to it Baseline and Revised Plans Advanced design faster starting in FY05

7. The Overall Cost Plan for the Baseline Design will Remain Unaltered

8. LCLS XTOD Mechanical & Vacuum Systems Development

9. Mechanical and Vacuum Systems Development Plan • Baseline requirements are being refined • Beam dump area is undergoing revision • Incorporation of a FEE low pass mirror is being tracked • XTOD Interfaces are being defined (Beam dump, XES, Conventional Facilities, Controls) • ICDs are being written • Control conventions, operational & safety strategies are being formed • Detailed designs are under development • Baseline supporting structures (pumps, pipes, tanks) • Resulting requirements and interfaces for vacuum systems are being refined • Seismic design, Vibration analysis • Detailed vacuum modeling and instrumentation & controls • Revised mechanical & vacuum cost estimates

10. Detailed Seismic And Vibration Analyses will be Conducted for all Structural Components • Seismic Design: • Seismic model is based on components chosen by initial vacuum analyses • Baseline design for pump stands and flex supports meet LLNL and SLAC Seismic Design Standards • Anchoring for baseline supports are chosen (HILTI Kwik Bolt 3) • Vibration Analyses • SLAC typical input spectra required • Vibration mode requirements TBD Pump Stand with Pipe and Flex Supports

11. The Proposed FEE Mirror Design will Impact XTOD Planning, Cost and Schedule • Instrumentation space will be limited • May require potential dual use diagnostic tanks • Potential impact on the Gas Attenuator design • Two design options available • May dictate smaller form factor design • Cost and schedule impact still needs to be done Beam Dump XTOD Instrumentation Proposed Low Pass Mirror System FEE XTOD Instrumentation

12. Pressure History at Any Location is Calculated With Our Custom Vacuum Model • Model uses Mathematica to solve for pressure using N coupled differential equations for roughing, turbo, and ion pumps Vi dPi/dt =  Qin -  Qout for i = 1, N where N = total volume elements Qin = time-dependent outgassing into volume i Qout = Cij (Pi-Pj) where Cij is the conductance into adjacent volume j or Qout = Sp Pi and Sp is the pressure dependent pump speed • Input local outgassing history that depends on material and handling procedures for each component • Use curve fit to pump speed curves as supplied by vendor • Can also model effects of pump failure on pressure at any location • These capabilities allow one to optimally choose the number and size of vacuum pumps for any system • This method was used to model an rf linac (where N=200) and actual hardware tests confirmed the model’s predictions (Spallation Neutron Source at LANL)

13. Assume outgassing rate of 10-10 T-l/sec/cm2 is reached in 100 hrs. Pressure scales with outgassing rate so the model accuracy is only as good as the outgassing rates that are input. 100 300 L/min rough on for 30 min 1 Torr 10-2 70 L/s Turbo on for 10 hours 10-4 75 L/s ion pump on for remaining time 10-6 1.0 x 10-7 T 10-8 102 103 104 105 seconds 100 hrs Pressure history at ends of 40 ft, 4” OD tube with pump in the middle

14. LCLS Gas AttenuatorProject Status

15. Gas Attenuator Status • Project Progress • Resources, costs & schedule confirmed • Design Concept • “Rotating Aperture” scheme added • Passive Gas attenuator Modeled • Prototype • Scope and schedule being modified

16. Passive Pumping- Calculations for 6-Port configuration Gas flow to chamber 37.7 T-L/sec 2976 sccm Pump Speed 6 x 50 L/s Inter-connection Coupling L = 3 cm Hole size = 3 mm dia. 6-port configuration can maintain 10 Torr with 3 mm apertures (GA Chamber Length = 6 m)

17. Another OptionNeutron Imaging Rotating Aperture ConfigurationsA Prototype Was Recently Successfully Tested apertures Gas cell With apertures motor Major advantage is, by precisely gating the aperture opening synchronized with beam pulses, the amount of gas flow can be lowered by at least one order of magnitude ~ 1/(duty factor) • For NI application: • duty factor is 2% • two 5-mm apertures @ 4000 rpm

18. Gas Attenuator with Rotating Aperture Configurations

19. 100-cm Design with RA* * Based on NIST X-Ray Form Factor, Attenuation, Scattering Tables

20. Nitrogen Pressure Requirements Operation from 0 to 150 Torr has been modeled with reasonable pumping

21. LCLS GA/RA Model

22. LCLS GA/RA Calculation Results Gas Attenuator set at 150 Torr Cell 1 at 2.2 mTorr Cell 2 at 3.76x 10-6 Torr Pumping Condition S2: one Scroll 600 L/m one Turbo 300 L/s S3: one Turbo 600 L/s Qi: 7.5 T-L/s (592 sccm)

23. System Comparisons of GA Design Options

24. Summary of the Design with Rotating Aperture Scheme • Potential Benefits • Shorter length • Less gas circulation • May extend the photon energy level beyond 2 KeV • Potential Risks • Moving parts inside vessel, but the risk can be managed • Prototype for other LLNL program has been successfully tested • Simultaneous Design(s) in progress • Design revision of existing rotating aperture design for LCLS • “Optimization” of space constrained passive systems • Down selection of design options • Will be included in the Prototype Task

25. Summary • The XTOD Mechanical And Vacuum Systems will provide the infrastructure interconnecting the diagnostics and experimental tanks in the FEE, Near Hall, Tunnel and Far Hall • Mechanical requirements and interfaces are being refined with detailed design proceeding • Vacuum models are being vetted and detailed system models will follow • The XTOD Gas Attenuator has 2 design concepts • Design based upon an existing LLNL rotating aperturte design and a passive design • We will down select amongst these options • Minor schedule revision will permit a more integrated design process by starting key instrumentation designs earlier • XTOD mechanical team has staffed up for FY05 • The detailed design work will escalate in FY-06 and FY-07 • We are mindful of the FEE deflection mirror and its potential impact