Physics Requirements for Conventional Facilities

1. Physics Requirements for Conventional Facilities May 2005 Lehman Review J. Welch, welch@slac.stanford.edu

2. Topics • MMF status • Undulator Hall • Ground motion • Temperature stability • Tolerances J. Welch, welch@slac.stanford.edu

3. MMF Status • Reviewed by Javier Sevilla • 100% Title II • Vibration mitigation included • Isolated slabs • Large slab under magnet measurement bench • Mechanical equipment moved as far away as feasible • Isolators under the HVAC equipment J. Welch, welch@slac.stanford.edu

4. MMF Status (cont.) • Thermal control • +- 0.1 C in critical areas: (~1600 sf) • Air washes down on equipment and is returned near the bottom of the walls. • Excess heat sources are water cooled • Racks and computers are put near the end of the airstream. J. Welch, welch@slac.stanford.edu

5. Undulator Hall Temperature Control • Experience base • Heat sources in the Undulator Hall • Effect of changing the temperature tolerance J. Welch, welch@slac.stanford.edu

6. Temperature control at other labs J. Welch, welch@slac.stanford.edu

7. Jacobs HVAC Experience J. Welch, welch@slac.stanford.edu

8. LCLS Tunnel Heat Sources • No high power electromagnets • EM quads less than 27 W • Undulator magnets are permanent magnets • No high temperature “cooling water” • Tempered cooling water delivered and returned near ambient air • No high power electronics • Almost all racks are in three service buildings on the surface and are accessible during operation • Budget for equipment and lighting load +- 50 W per meter of tunnel length transmitted to air J. Welch, welch@slac.stanford.edu

9. Heat Source Variables • Lighting load • Requirement is two level lighting, 5 fc (~ covered parking lot) for operation and 30 fc (~ conference room) for access • Systems will take a few hours to recover from extended access. AC response is in minutes. • Motors • Design not fixed, might include significant variable local heating • Vacuum pumps • Depend on pressures • Tunnel walls • Warm very slowly, respond to groundwater, essentially no transient effect J. Welch, welch@slac.stanford.edu

10. Tolerance to Temperature Assumed MMF Temperature Tolerance is 1/2 of Undulator Hall J. Welch, welch@slac.stanford.edu

11. Differential Settlement in the Undulator Hall • Physics Requirement  “Ground Motion Model” •  0.2 mm rms / year @ 10 m separation • Fits with once per week BBA with on 10 - 20% chance of going out of tolerance. • Linac Performance 0.08 mm rms / year @ 10 m • Averaged over the first 17 years of operation • Jacobs is required to design to the Linac value • Tunnel / Floor design is actively underway • Stretched wires and a hydrostatic leveling systems developed in parallel to provide a straightness reference. (R. Ruland) J. Welch, welch@slac.stanford.edu

12. Ground Motion Model Based mainly on the SLAC Linac. Best estimate of average motion of the floor of the Undulator Hall during the first three years of operation, if the Undulator Hall performed exactly like the linac structure. J. Welch, welch@slac.stanford.edu

13. Correlation with Distance • Relative motion correlates with distance between measurement points. • LCLS will have support points around 10 m apart, and quad separation of 4 m. • Stiffness of foundation may improve this correlation. J. Welch, welch@slac.stanford.edu

14. Startup Effect • PEP data • Much greater velocities occur in the first few years after construction • Motion continues at a signficant level indefinitely • SLAC Linac data • Model of Seryi and Raubenheimer give about a factor of two between 17 year average rate and first three average rate J. Welch, welch@slac.stanford.edu

15. Tolerance to Ground Motion A total phase error of roughtly 360 degrees is sufficient to lose one gain length and start to reduce the FEL performance This calculation assumes the phase error is produced only by ground motion transmitted directly to the quadrupole positions J. Welch, welch@slac.stanford.edu

16. Support system quadrupole stability tolerance The phase error that results if only the quadrupoles are allowed to move. J. Welch, welch@slac.stanford.edu

17. Segment axis stability tolerance Phase error that results if only the average position of the segment axes are allowed to move with respect to the axes connecting the adjacent quadrupoles J. Welch, welch@slac.stanford.edu

18. BBA residual phase error The phase error leftover after Beam based alignment is performed. Should have average slope of unity. Typical value is 180 degrees J. Welch, welch@slac.stanford.edu

19. Fiducialization Tolerance The true magnetic axis will not exactly coincide with the axis derived from the fiducials on the segments. Furthermore, when the segment is aligned in the tunnel, the fiducials will not exactly align with the beam axis. This tolerance is to account for the combined effect of these errors J. Welch, welch@slac.stanford.edu

20. Summary • Practical designs were found to address the vibration and temperature tolerances for the MMF • A general tolerance model, including the Undulator Hall ground stabilty and temperature stability, has been developed and tolerance space is being explored • Various UH tunnel and floor designs are actively being studied by Jacob since Title II started • Basics for good temperature control are in place. Flow studies would be nice. J. Welch, welch@slac.stanford.edu