1. Physics Requirements for Conventional Facilities
May 2005 Lehman Review
May 11, 2005
J. Welch,

2. J. Welch, welch@slac.stanford.edu
Topics
MMF status
Undulator Hall
Ground motion
Temperature stability
Tolerances
May 11, 2005
J. Welch,

3. J. Welch, welch@slac.stanford.edu
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
May 11, 2005
J. Welch,

4. J. Welch, welch@slac.stanford.edu
MMF Status (cont.)
Thermal control
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.
May 11, 2005
J. Welch,

5. Undulator Hall Temperature Control
Experience base
Heat sources in the Undulator Hall
Effect of changing the temperature tolerance
May 11, 2005
J. Welch,

6. Temperature control at other labs
Temporal Stability ± ˚C
Spatial Stability ± ˚C
Description
LCLS UH
0.2
Tunnel, below ground
LCLS MMF
0.1
Air shower
ALS
A few degrees
Lab in bldg
APS ring 1
A couple of degrees
APS MMF
0.3
NSSRRC, Taiwan
“several degrees”
Tunnel, above ground
NIST, AML
Diamond
0.5
NIF, target building
0.28
May 11, 2005
J. Welch,

7. Jacobs HVAC Experience
Confidential client
+/- 0.3 C
+/- 2% RH
National Semiconductor
+/ C
Linear Technology
+/- 1.1 F
+/- 3% RH
Rockwell Semiconductor
+/- 1.7 C
Atmel Semiconductor
+/- 0.6 F
May 11, 2005
J. Welch,

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 W per meter of tunnel length transmitted to air
May 11, 2005
J. Welch,

9. J. Welch, welch@slac.stanford.edu
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
May 11, 2005
J. Welch,

10. Tolerance to Temperature
Assumed MMF
Temperature
Tolerance is
1/2 of Undulator
Hall
May 11, 2005
J. Welch,

11. Differential Settlement in the Undulator Hall
Physics Requirement  “Ground Motion Model”
 0.2 mm rms / 10 m separation
Fits with once per week BBA with on % chance of going out of tolerance.
Linac Performance 0.08 mm rms / 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)
May 11, 2005
J. Welch,

12. J. Welch, welch@slac.stanford.edu
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.
May 11, 2005
J. Welch,

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.
May 11, 2005
J. Welch,

14. J. Welch, welch@slac.stanford.edu
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
May 11, 2005
J. Welch,

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
May 11, 2005
J. Welch,

16. Support system quadrupole stability tolerance
The phase error that results if only the quadrupoles are allowed to move.
May 11, 2005
J. Welch,

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
May 11, 2005
J. Welch,

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
May 11, 2005
J. Welch,

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
May 11, 2005
J. Welch,

20. J. Welch, welch@slac.stanford.edu
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.
May 11, 2005
J. Welch,