Pine, Bldg 48, Room 232 J. 4/29/04 Physics Requirements for Conventional Facilities Thermal, Settlement, and Vibration Issues J. Welch

Pine, Bldg 48, Room 232 J. 4/29/04 General Background What are Physics Requirements for CF? Needed to accommodate technical systems Distinguished from programming and site requirements Used by system managers as input for further design Where do they come from? GRD, System physicists, system managers Types of Requirements Environmental, Layout, Space, Utility and Radiation Critical Issues are Thermal, Settlement, and Vibration

Pine, Bldg 48, Room 232 J. 4/29/04 Sensitive CF Areas VibrationThermalSettlement Undulator Hall XXX MMFXX Sector 20XX Near HallX … Start with Undulator Hall (UH)

Pine, Bldg 48, Room 232 J. 4/29/04 Physics Sensitivities for UH FEL saturation length (86 m) increases by one gain length (4.7 m), for the 1.5 Angstrom case if there is: 18 degree rms beam/radiation phase error 1 rms beam size ( ~ 30  m) beam/radiation overlap error. Xray beam will move 1/10 sigma if ~ 1/10  rad change in angular alignment of various Xray deflecting crystals electron trajectory angular change of ~ 1/10  rad

Pine, Bldg 48, Room 232 J. 4/29/04 FEL Mechanism Exponential Gain Micro-bunching Narrow Radiation Cone ~1  r, (1/  ~ 35  rad) 2  radiation phase advance per undulator period

Pine, Bldg 48, Room 232 J. 4/29/04 Phase Sensitivity to Orbit Errors from H-D Nuhn LCLS: A < 3.2  m LEUTL: A < 100  m VISA: A < 50  m Path Length Error Phase Error

Pine, Bldg 48, Room 232 J. 4/29/04 LCLS Phase Tolerance Trajectory Straightness 2  m rms tolerance for the electron trajectory deviation from an absolutely straight line, averaged over 4.7 m Maintaining an ultra-straight trajectory puts demanding differential settlement and thermal requirements on the Undulator Hall Undulator magnet uniformity ∆K/K <= 1.5 x for 10 degrees error per undulator segment Undulator alignment error limited to 50/300 micron vertical/horz. Temperature coefficient of remanence of NdFeB is 0.1%/C, which, because of partial compensation via Ti/Al assembly, leads to a magnet temperature tolerance of ± 0.2 C.

Pine, Bldg 48, Room 232 J. 4/29/04 Obtaining an Ultra-Straight Beam BBA is the fundamental tool to obtain and recover an ultra-straight trajectory over the long term. Corrects for BPM mechanical and electrical offsets Field errors, (built-in) and stray fields Field errors due to alignment error Input trajectory error Does not correct undulator placement errors Procedure Take orbits with three or more different beam energies, calculate corrections, move quadrupoles to get dispersion free orbit Disruptive to operation

Pine, Bldg 48, Room 232 J. 4/29/04 Maintaining Alignment Ultra-straight trajectory will be lost if BPM’s move and feedback incorrectly corrects the beam Quads move Stray fields change Launch trajectory drifts Phase accuracy will also be lost if undulator segments move ~ 10  m, (50  m assuming zero fiducialization and initial alignment error) note that unless the actual motion is known, there is no effective way to re-establish the undulator position except through magnetic measurements. BBA once a month OK, once a day intolerable

Pine, Bldg 48, Room 232 J. 4/29/04 Motion Due to Temperature Change Dilitation 1.4 m Granite6-8 Anocast12 Steel11 Aluminum23 CTE ppm/deg C  T ~ 2  m / 1.4 m x 10 x = 0.1 deg C (for a nominal 10 ppm/deg C)

Pine, Bldg 48, Room 232 J. 4/29/04 Motion Due to Heat Flux or temperature gradients L = 3 m, titanium strongback Note that 3 W/m2 can be generated by ~1 degree C temperature difference between the ceiling and floor via radiative heat transfer 3 W/m 2 -> 2 micron warp for an undulator segment ∆T ≈ 0.05 deg C across strongback 

Pine, Bldg 48, Room 232 J. 4/29/04 Motion of the Foundation 1 mm/year = 3  m/day

Pine, Bldg 48, Room 232 J. 4/29/04 Implications for Undulator Hall Expect differential settlement of  m / day, in some locations. Make foundation as stable as possible geotechnical, foundation design, uniformity of tunnel construction and surrounding geologic formation, avoid fill areas Thermally stabilize the Undulator Hall reduce heat fluxes to a minimum HVAC designed to precisely regulate temperature to within a ± 0.2 deg C band everywhere in the Undulator Hall

Pine, Bldg 48, Room 232 J. 4/29/04 Title I Undulator Hall Foundation High Moment of Inertia, T shaped foundation Pea Gravel supportSlip planes Completely underground Imprevious membrane blocks groundwater Located above water table (at this time anyway) Low shrink concrete, isolated foundation “Monolithic”

Pine, Bldg 48, Room 232 J. 4/29/04 Title I Undulator Hall HVAC Cross flow to ducts AHU in alcoves 9X

Pine, Bldg 48, Room 232 J. 4/29/04 Magnetic Measurement Facility Air Temperature ± 0.1 deg C band everywhere in the measurement area deg C year round temperature Vibration Hall probe motion is translated into field error in an undulator field such 0.5  m motion causes 1 x10 -4 error. Measurements show vibrations below 100 nm.

Pine, Bldg 48, Room 232 J. 4/29/04 Sector 20 RF electronics Timing signals sensitive to temperature Special enclosure for RF hut Laser optics Sensitive to temperature, humidity and dust, vibration Class 100,000 equivalent, humidity control, vibration isolated foundation (separated from klystron gallery), fix bumps in road nearby.

Pine, Bldg 48, Room 232 J. 4/29/04 Near Hall Hutches with a variety of experiments to house Thermal, humidity, and dust control Class 10,000 equivalent Adjacent to Near Hall are Xray beam deflector which have significant vibration sensitivities.

Pine, Bldg 48, Room 232 J. 4/29/04 Xray Beam Pointing Sensitivity 250 m ~ 320 m Near Hall Far Hall Undulator ~ 400 m  FEL ~ 400  m  ’ FEL ~ 1  rad

Pine, Bldg 48, Room 232 J. 4/29/04 Pointing Stability Tolerance 0.1  spot stability in Far Hall (conservative) implies 0.1  rad pointing stability for deflecting crystals and electron beam Feedback on beam orbit or splitter crystal can stabilize spot on slow time scale. Typical SLAC beam is stable to better than 1/10  with feedback. Still have to face significant vibration tolerances on deflecting crystals Corrector magnets in BTH must be stable to better than 1/10 sigma deflection net. Electron beam stability is not expected to be not quite as good as 1/10 sigma

Pine, Bldg 48, Room 232 J. 4/29/04 Vibration and Pointing Stability Angular tolerance can be converted to a vibration amplitude for a specific frequency, for CF spec. y=A coskx-  t where y is the height of the ground, dy/dx is the slope. We want average rms(dy/dx) ≤ 0.1  rad  A ≤ 0.1  rad/2 . is the wavelength of the ground wave Typical worst case is around 10 Hz and speed of ground wave is around 1000 m/s.  A ≤ / 2  ~ m, which is quite reasonable since typical A~100 nm or less High Q support structures could cause a problem

Pine, Bldg 48, Room 232 J. 4/29/04 Conclusion Reliable production of ultrahigh brightness, FEL x-rays requires Exceptional control of the thermal environment in the Undulator Hall and MMF Excellent long term mechanical stability of the Undulator Hall foundation Care in preventing undesirable vibration near sensitive equipment at several locations Requirements are understood, what remains is to obtain and implement cost effective solutions.