Physics Requirements for Conventional Facilities Thermal Settlement and

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

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 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

Sensitive CF Areas Vibration Thermal Settlem ent 4/29/04 J. Welch Undulat or Hall X X MMF X X Sector 20 X X Near Hall … X X Start with Undulator Hall (UH) Pine, Bldg 48, Room 232 welch@slac. stanford. edu

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 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

FEL Mechanism Micro-bunching • 2 radiation phase advance per undulator period Narrow Radiation Cone ~1 r, (1/g ~ 35 rad) Exponential Gain 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

Phase Sensitivity to Orbit Errors Path Length Error Phase Error from H-D Nuhn LCLS: A < 3. 2 m LEUTL: A < 100 m VISA: A < 50 m 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

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 10 -4 for 10 degrees error per undulator segment Undulator alignment error limited to 50/300 micron vertical/horz. Temperature coefficient of remanence of Nd. Fe. B is 0. 1%/C, which, because of partial compensation via Ti/Al assembly, leads to a magnet temperature tolerance of ± 0. 2 C. 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

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 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

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 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

Motion Due to Temperature Change Dilitation CTE ppm/deg C Granite 6 -8 Anocast 12 Steel 11 Aluminum 23 1. 4 m T ~ 2 m / 1. 4 m x 10 -6 = 0. 1 deg C (for a nominal 10 ppm/deg C) 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

Motion Due to Heat Flux or temperature gradients d L = 3 m, titanium strongback 3 W/m 2 -> 2 micron warp for an undulator segment ∆T ≈ 0. 05 deg C across strongback 4/29/04 J. Welch Note that 3 W/m 2 can be generated by ~1 degree C temperature difference between the ceiling and floor via radiative heat transfer Pine, Bldg 48, Room 232 welch@slac. stanford. edu

Motion of the Foundation 1 mm/year = 3 m/day 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

Implications for Undulator Hall Expect differential settlement of 1 - 3 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 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

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

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

Magnetic Measurement Facility Air Temperature ± 0. 1 deg C band everywhere in the measurement area. 23. 50 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 x 10 -4 error. Measurements show vibrations below 100 nm. 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

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. 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

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. 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

Xray Beam Pointing Sensitivity ’FEL ~ 1 rad Near Hall FEL ~ 400 m Undulator 250 m ~ 320 m ~ 400 m 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu Far Hall

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 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

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 ≤ 10 -5/ 2 ~ 10 -6 m, which is quite reasonable since typical A~100 nm or less High Q support structures could cause a problem 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu

Conclusion Reliable production of ultrahigh brightness, FEL x-rays requires Exceptional control of 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. 4/29/04 J. Welch Pine, Bldg 48, Room 232 welch@slac. stanford. edu