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

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

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.

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

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

Baseline and Revised Plans Stretch FEE Completion Date but add to it WBS Title Need Baseline FY05 Plans Revised FY05 Plans 1.5.2 Controls Comiss Specify & Cost same 1.5.3 Mechanical & Vacuum FEE Prelim Eng BD/FEE, NEH, Tunnel, FEH Prelim Eng 1.5.4.2.2 Fixed mask Facility Calc Backgrounds Prelim Eng 1.5.4.2.3 Slits 1.5.4.2.5 Gas attenuator Prelim Eng, Proto & Simulation 1.5.4.2.8 Solid attenuator 1.5.4.4.2 Far Hall monochromater Users 1.5.4.4.3 Far Hall pulse split and delay Prototype 1.5.5.2 Modeling and simulation Instrument Sim 1.5.5.3.1 Direct Imager Detailed Eng Proto & Sim 1.5.5.3.2 Indirect Imager Simulation, R&D 1.5.5.4.2 Total energy measurement Proto & Sim 1.5.5.4.4 Spectrometer(s) 1.5.4.2.4 Flipper Mirror Advanced design faster starting in FY05

The Overall Cost Plan for the Baseline Design will Remain Unaltered PROJECT WBS[5] FY05 FY06 FY07 FY08 FY09 Cumulative 1.05.03.02 Mech/Vac Front End 146,025 96,467 225,718 527,936 996,146 1.05.03.03.01 NEH Hutch 1 119,554 142,001 261,555 1.05.03.03.02 NEH Hutch 2 64,781 132,788 197,569 1.05.03.03.03 NEH Hutch 3 127,741 192,522 1.05.03.04 Mech/Vac Tunnel 42,833 2,061,857 2,104,690 1.05.03.05.01 FEH Hutch 1 32,049 108,829 140,877 1.05.03.05.02 FEH Hutch 2 114,728 146,777 1.05.03.05.03 FEH Hutch 3 69,553 101,601 1.05.04.02.02 Fixed Mask 254,605 94,903 349,508 1.05.04.02.03 Slit/Collimator A 1,090,360 960,139 2,050,499 1.05.04.02.04 Slit/Collimator B 1,030,057 1.05.04.02.05 Gas Attenuator 404,996 565,148 1,385,774 2,355,917

LCLS XTOD Mechanical & Vacuum Systems Development

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

Pump Stand with Pipe and 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

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

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)

Pressure history at ends of 40 ft, 4” OD tube with pump in the middle 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 1 10-2 10-8 10-6 10-4 Torr 102 103 104 105 seconds 300 L/min rough on for 30 min 70 L/s Turbo on for 10 hours 75 L/s ion pump on for remaining time 100 hrs 1.0 x 10-7 T

LCLS Gas Attenuator Project Status

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

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)

Another Option Neutron Imaging Rotating Aperture Configurations A 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

Gas Attenuator with Rotating Aperture Configurations

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

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

LCLS GA/RA Model

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)

System Comparisons of GA Design Options internal moving components Design Features Passive Pumping Space Constraint Rotating Aperture Length 10 m <10 m <4 m Photon Energy Limits Up to 2 KeV Up to 3 KeV Circulated N2 Gas 3000 sccm > 3000 sccm 590 sccm Number of vessels 7 7+ 5 Prototype planned demonstrated Risk low moderate internal moving components Risk Management may not need prototype needs prototype can be minimized by: 1. using commercial components (air bearings) 2. long-term prototype testing Control System vacuum vacuum and motor control synchronized with beam pulse

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

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