NLC - The Next Linear Collider Project Mike Woods May 1999 Vibrations and the NLC IR Welcome to the NanoWorld !

Mike Woods May 1999 NLC Facilities Engineer site selection compressors, cooling systems, ventilation traffic, construction complying with tolerances Particle Physicist wants luminosity! detector design machine-detector interface Accelerator Physicist beam optics design setting tolerances machine-detector interface Mechanical Engineer design and modeling manufacturing complying with tolerances Controls Engineer feedback systems - beam-based (deflections) - quad vibration sensors fast feed-forward (deflections) CDR Design and Cost Estimate Vibration Standards Compliance criteria Prototype results for tunnel quad Prototype results for IR quad

Mike Woods May 1999 NLC CDR Planning Overview Sensitivity to vibrations (tolerances) Characterizing vibrations - seismic sources - cultural sources - response of mechanical structure Existing prototype results - SLAC Linac tunnel and quads - SLAC FFTB quads and Shintake spotsize monitor - Fermilab tunnel and quads Existing criteria for site selection and compliance Strategy and R&D plans - passive compliance - quad vibration feedback - beam-based feedbacks Outlook

Mike Woods May 1999 NLC Vibration Theory and Introduction sis the distance along the beam trajectory P( ,k;s) is the 2-dimensional power spectrum describing the vertical vibration amplitudes of the magnets G(k;s) is the lattice response function F(  ) is the feedback suppression function P( ,k) results from: i) seismic motion ii) cultural effects (cooling systems, ventilation, traffic…) iii) response of mechanical support structure Seismic motion effects i) if NLC quad motion is as good as seismic motion of SLAC tunnel floor, then luminosity loss due to vibrations will be less than 1%. ii) At SLAC, seismic motion is well described by a model consisting of horizontally traveling waves that are isotropically distributed in direction. Wave phase velocity fits empirically to v(m/s) = exp(-f(Hz)/2.0)=f Reference: ZDR

Mike Woods May 1999 NLC Correlation spectrum of seismic ground motion measured by two seismometers separated by 100 meters in SLAC Linac tunnel. Data is solid line and model prediction is dashed line. Vibration Theory and Introduction (cont.) Final Focus lattice response function, G(k). Low-frequency seismic waves have very long wavelengths. Lattice response, G(k), is insensitive to long wavelengths. Reference: ZDR

Mike Woods May 1999 NLC Vibration Tolerances Tolerance spectrum for seismic waves, together with Linac tunnel floor data. Jitter Budget (f>5Hz) Reference: ZDR Machine Section Vertical Accumulated Accumulated Jitter Jitter Luminosity Loss Linac 6nm0.35  1.5% Final Focus 4-15nm 0.52  3.4% Final Doublet 1nm 0.56  3.9%

Mike Woods May 1999 NLC Vibration Tolerances (cont.) Normalized Luminosity vs Offset at IP  Offset (  x ) ~10-15% luminosity loss at 5nm vertical offset *differential offset of two colliding beams is relevant, not their absolute positions *differential vibration of two opposing quads is relevant, not their absolute vibrations

Mike Woods May 1999 NLC Vibration Effects of Cultural Sources References: 1. CERN-SL/94-41 (RF) 2. CERN-SL/93-53 Ratio of vibrations for ventilation system on and off Ratio of vibrations for water cooling station on and off Vibration measurements of LEP tunnel floor; location is at furthest point from Geneva, under Jura ~100 meters deep. Quiet: weekend night all accelerator systems off no people Noisy: daytime activity during shutdown water cooling, ventilation on many people nearby

Mike Woods May 1999 NLC Vibration Data from Fermilab Reference: Ground vibration measurements for Fermilab future collider projects, PRSTAB 1, (1998). “During the daytime and on the Fermilab site, neither the E4 building (on surface) nor the main ring tunnel are quiet enough for future colliders” comments: 1. should qualify this statement for existing conditions 2. X-band Linear Collider tolerance curve shown is tolerance assuming seismic wave-like motion only nm rms for f>5Hz. With reasonable improvements (ex. isolation from He liquefier plant) should be able to achieve XLC tolerances.

Mike Woods May 1999 NLC Vibration Data from SLAC Linac Rms vibration amplitude for Linac tunnel floor Rms vibration amplitude for Q701 with accelerator water on/off Linac tunnel floor vibrations are acceptable at 2am during an accelerator downtime seismic motion at quiet sites is acceptable! Linac quad vibrations are unacceptable - improved (variable speed) water pumps needed (59Hz resonance) - improved mechanical support needed (10-15Hz resonance) Reference: Vibration Studies of the Stanford Linear Acclerator, SLAC-PUB-6867 (1995).

Mike Woods May 1999 NLC ground concrete block quadrupole table beam direction KEK BSM table IP flange piezo electric supports QC2QC1 QX1 Vibration Data from FFTB Shintake Spotsize Monitor Mark L4-C Geophone measurements 40nm Electron Beam Jitter relative to Interferometer Fringes References: Vertical position stability of the FFTB electron beam measured by the KEK BSM monitor, FFTB (1998) FFTB Results, talk by T. Slaton June

Mike Woods May 1999 NLC Vibration Data from FFTB Tunnel/Quad Reference: figure from T. Slaton » FFTB Quad support is a good starting point for NLC tunnel quad support BPM Box has same mechanical support as FFTB Quad, so measurement is equivalent to a quad with no cooling. Vibration Measurements at rf BPM Box at IP Image Point

Mike Woods May 1999 NLC Strategy and R&D Plans 1. Passive Compliance - site selection - vibration standards - mechanical design - machine-detector interface 2. Quad Vibration feedbacks (final doublet only) - laser interferometer or inertial sensors - piezoelectric movers on quads 3. Beam-based feedback - intertrain feedback using measured deflections - way fast feed-forward using measured deflections Strategy R&D 1. Prototype tunnel quad that satisfies vibration requirements 2. Prototype final doublet quad that satisfies vibration requirements (with quad vibration feedbacks if needed) 3. Prototype way fast feed-forward

Mike Woods May 1999 NLC Criteria for Site Selection and Compliance Existing Criteria from Conventional Facilities Web page on Site Selection Criteria: “During operations, motion of the quadrupole magnets in the vertical plane must not exceed 10 nanometers rms for frequencies greater than 1 Hz and wavelengths less than 200 meters.” This needs needs to be fleshed out in detail » need to review criteria by Linac and Beam Delivery experts » need to document criteria in an NLC Note and give details on how to assure compliance (ie. measurement specs and tolerances). » Need separate criteria for: - site selection - tunnel floor measurements - tunnel quad measurements - IR floor measurements - IR quad measurements (how to comply with this??)

Mike Woods May 1999 NLC Detector Installation in IR Hall » Detector designers need to minimize longitudinal size of detector and IR hall » Beam optics designers need to accommodate detector with final doublet Q1 permanent magnets inside detector in common support tube Q2 magnets in tunnels leading to IR » Mechanical engineers will attempt to satisfy vibration criteria passively Eliminate z space taken by this support Minimize z opening of endcap door Allow for lateral install/remove of detector in keyhole-shaped IR Hall

Mike Woods May 1999 NLC Quad Vibration Feedback Quad Simulator Prototype 3 vertical piezo movers capacitive displacement sensors vertical and horizontal geophone sensors 100kg ‘quad’ Laser Interferometer Vibration Sensor Optical Anchor Schematic 10-meter Interferometer Prototype

Mike Woods May 1999 NLC Reference: J. Frisch (Capacitive displacement sensor) Quad Vibration Feedback (cont.)

Mike Woods May 1999 NLC Beam-based Feedbacks Sample deflections of first bunches in train and kick most of train into collision 1. Slow feedback (inter-train)2. Fast feed-forward (intra-train) Measure deflections of trains and apply corrector kick to achieve collisions

Mike Woods May 1999 NLC 1. Vibration Standards Accelerator physicist updates tolerances Vibrations physicist writes Standards document Conv Facilities engineer evaluates compliance with Standards and completes compliance document Vibrations physicist review compliance document prepared by CF engineer Vibrations physicist updates Standards document Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Milestones

Mike Woods May 1999 NLC 2. Tunnel Quad Prototype Document performance of FFTB Quads Prototype complete Prototype tests complete Document and Review Performance and Capability 3. Fast Feedforward Prototype complete Prototype tests complete Document and Review Performance and Capability Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Milestones (cont.)

Mike Woods May 1999 NLC 4. IR Quad 4.1 Quad Simulator Prototype Complete Tests Document and review results meter interferometer Complete Tests Document and review results 4.3 Interfer./Quad simulator integrated Complete protototype Complete tests Document and review results 4.4 Inertial Capacitive sensor Complete prototype Complete tests Document and review results 4.5 Detector engineering Specify dimensions and B-field 4.6 IR quad prototype Prototype complete Complete tests Document and review results Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Milestones (cont.)

Mike Woods May 1999 NLC Summary and Outlook Vibration Standards and compliance criteria will be fully developed. Successful prototypes will demonstrate ability to collide nanometer-scale beams. Strategy and Conceptual R&D Plan are well-defined. Need to update calculations of vibration tolerances, and optimize beam optics design to minimize sensitivity. Need more characterization of cultural vibration sources and demonstrate means to mitigate these effects. Need coordination of facilities, mechanical and controls engineers with accelerator and detector physicists. CDR Design and Cost Estimate Vibration Standards Compliance criteria Prototype results for tunnel quad Prototype results for IR quad