NLC Vibration R

1
NLC Vibration RDWhats New?

• Tom Markiewicz
• LC99, Frascati, Italy
• October 1999

2
Small Spot Size Concerns
Q1
Q1
Relative Motion of two final lenses
e
e-
sy 3.9 nm Dy sy/4 1 nm

• Conv. Fac. Mech. Eng. Detector
• review available data and supplement if needed
• develop criteria and a means of verifying
  compliance
• prototype equipment and measure

Geological sources Seismic Irreducible Site
Criteria Cultural sources Pumps, Flowing H20 or
air, DTemp Mechanical isolation / amplification
Supports, resonances
An issue throughout NLC but especially at the IP
3
Small Spot Size Concerns

• Spatial Domain Only relative motion important
• In general Lattice response function
• At the IP Want lenses on both sides of the IP to
  move up and down together
• Measurements show that seismic motion in
  frequency range where motion is large enough to
  matter ( lt 5 Hz) has sufficiently long
  wavelength to move both lenses simultaneously
  (motion is well correlated)
• To extent that there are no man-made vibration
  sources
• Tie both Q1 together by anchoring each
  independently to local bedrock
• Alternatively tie the two lenses together
  (support tube across the IP (JLC))

4
Small Spot Size ConcernsFrequency Domain if
change is slow, correct it

• NLC performance dependent on beam based feedback
• If relative motion has low frequency (lt1-5 Hz,
  set by 120 Hz rate), no problem correct with
  beam based feedback
• TESLA solution 2820 bunches w/ 337 ns. spacing
  correct in 80 bunches -gt 40 kHz
• Prepare for eventuality that, despite best
  efforts, there IS cultural noise gt 5 Hz
• Closed loop feedback that moves quad support
• Actuator piezoelectric crystal
• Sensor
• Interferometer (Optical anchor) tie each Q1
  to bedrock
• Inertial capacitive sensor correct each Q1 to
  inertial reference frame
• Open loop feedback operating within a NLC bunch
  train (95 bunches w/ 2.8 ns spacing)
• Measure beam-beam deflection and drive a very
  low current kicker with fast electronics
• Must be very fast to be worthwhile Goal correct
  in 15 ns or 5 bunches

5
Interferometric Sensors Optical anchor Begun
After Snowmass 1996 (Mike Woods)

• 10 m interferometer in place
• 100 kg quad simulator setup exists
• piezo movers, capacitive displacement sensors and
  geophone sensors
• Piezo position control with 1 nm resolution
  demonstrated
• Goal1 Integrate 10m interferometer with 100 kg
  quad
• Goal2 Integrate with full scale prototype

1 m Interferometer Piezo Test Results
Feedback ON
2.5 nm
1 nm rms fringe stability
1 Hour
6
Non-Optical Vibration Suppression RD

• Inertial Sensors (J. Frisch)
• Conceptual design frequency response,
  sensitivity, and system noise look OK
• Need to construct and test

Very fast IP feedback (M. Breidenbach) BPM
sensors and low current correctors
Kicker
Kicker
Measure deflection relative to un-deflected beam
BPM
BPM
Gain Offset adjust _at_ 120 Hz
7
Small Spot Size and Vibration Control

• Nanometer level relative stability of quads
  across the IP
• Passively
• Site requirements lt 10 nm rms for n gt 1 Hz and l
  lt 200 m (similar to SLAC Linac)
• Stable (compact?) detector
• Actively, allow for a multi-layered approach
• Closed loop active feedback driving piezo movers
  on quads
• Very Fast Feedback to correct back of bunch train
  using information from earlier bunches

Snowmass detector with optical anchor
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Small Spot Size and Vibration Control RD Program
Interferometric Sensors Optical anchor
Inertial Capacitive Sensors
Very Fast IP feedback BPM sensors and low
current correctors at IP Use beam-beam deflection
of head of bunch (or pilot bunch) to correct
following bunches of 260 ns long train Goal 15
ns latency
9
Extraction Line Instrumentation

• Standard Diagnostics Facilitate transport to
  dump with minimal loss
• BPMs, toroids, ion chambers
• Detailed simulations needed to design Lum and
  Physics detectors
• Luminosity Monitors
• Deflection scan BPMs
• Pair monitors
• Radiative Bhabha monitors
• Physics Detectors
• Compton polarimeter
• Energy spectrometer
• Wire scanner (DE)
• Co-linearity detectors
• Small angle electron taggers
• Instrumented masks
• Beamstrahlung monitors

10
Optimizing Luminosity
Deflection Scan BPMs
Energy in ee- Pairs
11
Extraction Line 150 m long with common g and e-
dump
Plot beam with lt 250 GeV of nominal 500 GeV
Y
X
0.25 of beam with 4.7 kWatts lost
12
Quadrupole Vibration Measurementsin the FFTB at
SLAC
Rachel Fenn, Tim Slaton, Mike Woods 08/23/99

• Goals of project
• Repeat vibration data measurements for QM1B
  magnet, which was claimed to have very good
  results at time of ZDR, but was not documented
  well. Quantify results.
• Take vibration data on a different type of
  quadrupole magnet in FFTB. Quantify results.
• Develop standard datataking and analysis
  procedures.

ZDR p. 395 Seismometer measurements that were
made on top of the quadrupoles and on the floor
in the FFTB show that there is only a few nm of
relative motion (fgt0.1 Hz) between them when
the quadrupoles are powered. (no reference or
figure given to support this)
13
FFTB Quadrupoles Measured
Beam height approx. 5 feet
14
FFTB QM1Bvertical geophone data
15
FFTB Measurement Summary and Conclusions
16
FFTB Measurement Conclusions
- new QM1B data is consistent with earlier data
would be good to take data with STS-2 down to
0.1Hz and combine with geophone data to cover
range 0.1 - 128 Hz - high frequency data
(60-120Hz) can be important - important to
understand QC3 data better. Take data with
water off - QM1B data is encouraging for meeting
NLC requirements, but QC3 data illustrates some
of the challenges ahead - vibration data on NLC
prototypes is needed