NLC Vibration Program

1
NLC Vibration Program

• Tom Markiewicz/SLAC
• MAC Meeting
• November 2002

2
Beam Delivery RD Plan

• In Progress
• SLAC based work on inertial systems
• Simple block capacitive sensor Himel
• Long steel beam Himel
• UBC work on Optical Anchor
• Fast Feedback demonstration in NLCTA (FONT)
• Additional Work Planned for FY2003
• Measuring the vibration properties of a SC quad
  Parker
• Measuring field position stability of SC
  Detector Solenoid
• Investigate feasibility of cavity BPMs w/ 1nm
  resolution Himel
• Future
• Single beam tests that use 1-nm BPMs to
  demonstrate 1-nm stability
• Realistic design of IP Girder prototype after we
  down-select magnet stabilization options

3
Differences from May 2000 Plan

• Do NOT make building a realistic IP Girder an
  immediate priority
• Discussion to follow
• MUST begin to investigate vibration properties of
  SC magnets
• Too important to leave to later
• Nanometer-BPM RD with BEAM TESTS can answer many
  of vibration stability issues thought previously
  to be uniquely answerably by IP Girder LINX
  programs
• Push nm-BPM program as much as possible

4
SLAC Inertial Vibration Stabilization Program
Joe Frisch, Tom HimelEric Doyle, Leif Eriksson,
Linda Hendrickson, Richard Partridge
3m magnet and 5.5m support have same
mechanical properties (mass, w) as final design
5
IP Girder Choices

• Magnet Permanent or SC ?
• Support Tube Details
• Material / wall thickness / diameter
• Resonance / stiffness requirements depend on
• Support scheme (cantilevered?)
• Sensor (inertial?)
• Support (soft)
• Activator (electrostatic pusher?)
• Simulate Magnetic Coupling of QD0 to Detector
  Solenoid Fringe Field
• 1000 lb. non-linear off-axis load on PM QD0
• Static springs or use real solenoid

6
Final Doublet Technology Choice

REC Permanent Magnet w/ Adjustable Strength
Cold Bore SC Design
7
More Engineering IssuesHow Real do we have to be?

• Vacuum
• Implement mechanical design consistent with
  vacuum requirement (1 nTorr?) and 1cm radius beam
  pipe
• May mean that 3m magnet is broken into pieces
• Decide whether beam pipe hangs free of magnet or
  not
• Nature of contact between QD0 magnet and the
  support tube
• Static FFTB cams as opposed to a fully functional
  FFTB mover
• Assembly
• Joints and flanges which allow assembly and
  servicing must be designed and included
• Do we need to support IP end of cantilever with a
  vibrating detector endcap door?

8
PeP-II IP Girder
A lot of work to do it right and, finally, the
Devil is in the Details
9
IP Girder Prototype
4.5m

• To be useful must reflect final design
• Basic technology choices are not in hand
• Will learn much from the simple 3m prototype
• Consensus at Nanobeam 2002 was nice but not
  necessary
• Design of NLC IP on paper for alternate
  technology choices first

.5m
7m
10
Magnet Measurements

• SC FD Quad See Brett Parkers talk
• BNL Funds approved to wind test short prototype
  of cold mass
• BNL group is forming that will address internal
  vibration issues
• SC Detector Solenoid
• Couples to QD0 through fringe field if m?1
• Permanent magnet m1.
• Directly steers beam through non-zero crossing
  angle
• Plan to measure field stability in fringe region
  or coil vibration of a detector solenoid to begin
  to get some idea of the size of the problem
• Adjustable Permanent Magnet
• M. Kumada (Nat. Inst. of Radiological Sciences in
  Japan)
• Nanobeam 2002 reports by Kumada, Iwashata
  Antokhin

11
Shintakes C-Band Cavity BPMs
1995 FFTB Tests 25 nm resolution _at_ 6 x 109 /
bunch
Resolution Theoretically sub-nmPractical
Limits -Common Mode Leakage -Angle
Alignment -Losses, Drifts Phase matching in
Cables, Filters, Mixers -Digitizers and Pulse
Shapers not optimized
12
Nanobeam 2002 Development

• Off-Hand remark by TorIf we had nm BPMs we
  wouldnt need the beam-beam collision to verify
  nm-level vibration stability (LINX)
• Joe Frisch/Steve Smith No problem in principle

4 C-Band ATF BPMs

• Improvements
• Digital Down Conversion Fast Scope (Drifts,
  resolution dynamic range)
• New BPM design w/couplers that remove CM
• Angle Adjustments Hardware
• Improved S/N by using rad hard electronics on
  beamline

13
BPM RD Plan

• October 2002 Discussions w/ ATF people
• December 2002
• Test one cavity w/ high gain electronics,
  tiltyaw control
• March 2003
• Array of 3 BPMs with independent tilt/yaw adjust,
  temperature control multi-channel readout on
  common concrete table or in specially design
  common support tube with full positioning
  adjustment capability (under design at LLNL)
• Future
• Stabilize array using inertial /or optical
  scheme
• Create waist with quad array
• stabilize magnet as well as BPM array(s)
• A convincing demonstration that vibration problem
  is under control

14
Single Beam Vibration Stability Test
Spot Size
Magnet
BPM
BPM
Artists conception
15
Optical Anchor
Sub-nm resolution measuring fringes with
photodiodes ? drive piezos in closed loop
16
UBC RD on Interferometers
17
UBC RD on Interferometersfrom Nanobeam 2002

• Test platform challenges
• clean system
• high natural frequency
• Resonances
• Bandwidth
• Algorithms
• Piezo stiffness

From 90 nm to 5 nm at 5 Hz
Stabilize mirror 10 Meters in Air RMS 25.4 nm
before, 0.27 nm after
18
FONT Beam Test on the NLCTA Very Fast
Intra-train IP Feedback
Kicker Amplifier
NLCTA
Kicker
NLC
4.5m
Round-trip Delay
BPM Processor
BPM
Colliding beams
Single beam
(short cable delays, long trip time)
(shorten trip time, lengthen cable delays)
19
NLCTA FONT Installation
Magnet assembly and X-band BPM installed onto
NLCTA downstream of RF structures.
Beam direction
Feedback loop
20
Feedback Performance vs. Gain
21
FONT Results 27 Sept 2002x10 Improvement in
Position
BPM for 5 Dipole Settings
After 1 Latency Period Position corrected
independent of gain, then loop turns off
As above but loop ON Beam stays corrected until
end of pulse
22
FONT Plans

• Demonstrate removal of high-frequency 'static'
  structure in bunch position within train
• Reduce latency validates delay-loop FB system
• Addition of witness BPMs
• current BPM is part of feedback loop
• Demonstrate position FB in both x, y, x, y
• Use solid-state kicker amp rather than tube amp
• NLC only requires volts

23
FY 2003 Deliverables

• For Sure
• New inertial sensor
• Results from 3m prototype w/ inertial sensor
• Understanding of resolution limits of cavity BPMs
  by measuring relative motion of BPM array _at_ 1nm
  level at ATF
• Fabrication of short SC prototype
• Measurement of SC quad field vibration w.r.to
  cryostat
• Incremental progress at UBC and FONT
• Less Likely
• Incorporate interferometer on 3m prototype
• Stabilize array of nm-BPMs measure absolute
  stability
• Measurement of one solenoid coil position or B
  in fringe region
• Engineering sketch of NLC IR w/ Perm. Magnets