NLC - The Next Linear Collider Project

Mike WoodsMay

1999

Vibrations and the NLC IR

Welcome to the NanoWorld !

Mike WoodsMay 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 EstimateVibration Standards Compliance criteria

Prototype results for tunnel quad Prototype results for IR quad

Mike WoodsMay 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 WoodsMay 1999

NLC Vibration Theory and Introduction

dsddk

FskGskPyIP

22)();();,(2

s is the distance along the beam trajectoryP(,k;s) is the 2-dimensional power spectrum describing

the vertical vibration amplitudes of the magnetsG(k;s) is the lattice response functionF() 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) = 450+1900exp(-f(Hz)/2.0)=f

Reference: ZDR

Mike WoodsMay 1999

NLC

Correlation spectrum of seismic ground motion measured by two seismometers separated by 100 meters in SLAC Linac tunnel. Data is solidline 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 WoodsMay 1999

NLC

Vibration Tolerances

Tolerance spectrum for seismic waves, togetherwith Linac tunnel floor data.

Jitter Budget (f>5Hz)

Reference: ZDR

Machine Section Vertical Accumulated Accumulated Jitter Jitter Luminosity Loss

Linac 6nm 0.35 1.5%Final Focus 4-15nm 0.52 3.4%Final Doublet 1nm 0.56 3.9%

Mike WoodsMay 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 WoodsMay 1999

NLC Vibration Effects of Cultural SourcesReferences: 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 peopleNoisy: daytime activity during shutdown water cooling, ventilation on many people nearby

Mike WoodsMay 1999

NLC Vibration Data from FermilabReference: Ground vibration measurements for Fermilab future collider projects,

PRSTAB 1, 031001 (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. 3. 20nm rms for f>5Hz. With reasonable improvements (ex. isolation from He liquefier plant) should be able to achieve XLC tolerances.

Mike WoodsMay 1999

NLCVibration Data from SLAC Linac

Rms vibration amplitude for Linactunnel floor

Rms vibration amplitude for Q701with 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 WoodsMay 1999

NLC

groundconcrete block

quadrupole table

beamdirection

KEK BSM table

IP flange

piezo electric supports

QC2QC1

QX1

Vibration Data fromFFTB Shintake Spotsize Monitor

Mark L4-CGeophone measurements

40nm Electron Beam Jitterrelative to Interferometer Fringes

References: Vertical position stability of the FFTB electron beammeasured by the KEK BSM monitor, FFTB 98-03 (1998)FFTB Results, talk by T. Slaton June 1998..

Mike WoodsMay 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 WoodsMay 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 requirements2. Prototype final doublet quad that satisfies vibration requirements

(with quad vibration feedbacks if needed)3. Prototype way fast feed-forward

Mike WoodsMay 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 WoodsMay 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 tubeQ2 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 WoodsMay 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 SensorOptical Anchor Schematic

10-meter Interferometer Prototype

Mike WoodsMay 1999

NLC

Reference: J. Frisch

(Capacitive displacement sensor)

Quad Vibration Feedback (cont.)

Mike WoodsMay 1999

NLC

Gain &Offsetadjust @120 Hz

Measure deflection relative toun-deflected beam

BPM BPM

Kicker Kicker

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 applycorrector kick to achieve collisions

Mike WoodsMay 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

1999 2000 2001 2002Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2

Milestones

Mike WoodsMay 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 ReviewPerformance and Capability

1999 2000 2001 2002Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2

Milestones (cont.)

Mike WoodsMay 1999

NLC

4. IR Quad4.1 Quad Simulator Prototype Complete Tests Document and review results4.2 10-meter interferometer Complete Tests Document and review results4.3 Interfer./Quad simulator

integrated Complete protototype Complete tests Document and review results4.4 Inertial Capacitive sensor Complete prototype Complete tests Document and review results4.5 Detector engineering Specify dimensions and B-field4.6 IR quad prototype Prototype complete Complete tests Document and review results

1999 2000 2001 2002Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2

Milestones (cont.)

Mike WoodsMay 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 EstimateVibration Standards Compliance criteria

Prototype results for tunnel quad Prototype results for IR quad