Issues of stability and ground motion in ILC

1
Issues of stability and ground motion in ILC

• Andrei Seryi
• SLAC
• October 17, 2005

2
Introduction

• Goals of this talk
• Discuss ILC stability goals, in particular for
  the beam jitter
• jitter at the end of the linac, along the BDS and
  IP
• Suggest for discussion the criteria for site
  stability and for additional jitter of beamline
  hardware components
• Review present status of stability studies and
  discuss feasibility of achieving the stability
  goal
• Will need to refer to the latest studies for ILC,
  as well as relevant earlier developments for
  NLC/GLC, CLIC and TESLA, as well as for XFEL

3
Technical Review Committee 2002 studies
Integrated spectra of absolute (solid lines) and
relative motion for 50m separation obtained from
the models

• Intratrain feedback is a must in TESLA
• Even with intratrain, noisy site cause Luminosity
  loss
• Hardware jitter was not included in simulations !
• TRC says that linac quad stability need urgent
  study

4
Beam jitter and its control in ILC

• Sources of IP beam jitter
• motion of beamline components (in linac, BDS,
  FD), energy jitter, kicker jitter
• Motion of beamline components consist of
• site ground motion and ILC in-tunnel and
  near-tunnel hardware noise
• additional noise of beamline components including
  amplification of floor motion supports
• Approach to IP beam jitter control
• fast intra-train feedback to recover luminosity
• range is finite 1-2s in X, 50-100s in Y, will
  be discussed below
• With fast feedback, the requirements to
• ground motion linac and BDS quads jitter and FD
• has to be determined not from IP jitter, but
  from diagnostic performance and emittance
  preservation

5
ILC jitter goals discussion

• The large capture range (10s of s) of fast
  feedback does not mean that larger jitter is
  allowed along the machine
• Many reasons why the jitter should be smaller
  that beam size
• The need to minimize De/e due to collimator
  wake-fields,
• to provide acceptable conditions for beam
  diagnostics,
• to minimize jitter effects on dispersion free
  steering, etc.
• The edge of the comfortable range jitter lt 50 s
• the 50 jitter at the end of main linac gt 40nm
  jitter of linac quads
• BDS (w. nonlinear elements) is more sensitive
  than weak linac
• criteria for BDS must be different, tighter than
  in linac
• may allow beam jitter to grow to 100 before FD
• FD contributes one to one to IP jitter, but less
  relevant
• FD jitter of 100nm should be OK
• No active stabilization should be needed
  (position monitoring useful)

6
Jitter affecting linac tuning, NLC example

• Procedure
• steer to min Q-BPMs
• perform DF steering
• apply e bumps in Y
• Quad vibration budget
• 42nm in X (rms)
• 11nm in Y (would cause 30 beam jitter at linac
  exit)
• Twice larger jitter deteriorates e
  significantly
• Would averaging solve this?
• Effect should be generic issue for ILC as well

P.Tenenbaum, NLC MAC, June 2003
7
ILC simulations with GM, jitter feedback

• Integrated simulations performed by Linda
  Hendrickson
• Assumptions
• 5Hz feedbacks loops, cascaded, exp response of
  36 5Hz pulses
• Linac 5 distributed loops, each with 4 X 4 Y
  dipole correctors, and 8 BPMs
• BDS 1 loop, 9 BPMs and 9 dipole correctors
• IP deflection (XY) 5Hz loop, not cascaded, exp 6
  pulses
• Ground motion and component jitter
• Ground motion models K and C (fit to KEK and
  DESY) and B
• component jitter (25 nm in BDS including FD, 50
  nm in linac)
• kicker, current, energy jitter, BPM resolution
• kicker jitter (0.1 sigma), current jitter (5),
  energy jitter (0.5 uncorrelated amplitude on
  each klystron, 2 degrees uncorrelated phase on
  each klystron, 0.5 degrees correlated phase on
  all klystrons), BPM resolution 100 nm

8
Model K
(nm)

• Based on measurements at KEK, in a borehole near
  Higashi-Odori, Toshiaki Tauchi et al.
• Close to model C in 1-10Hz, but less noisy above
  20Hz

model K
80m
9
ILC simulations with GM, jitter feedback
Linda Hendrickson
Preliminary results. Statistics for gm C is
smaller
10
ILC simulations, continued

• ILC simulations are ongoing, more studies are
  happening as we speak here
• In particular, growth of jitter along the BDS is
  being studied
• Luminosity with 5Hz and intratrain feedback is
  being studied
• In particular observe noticeable luminosity
  reduction with gm C and K, e.g. Lumi is
• 37 with 5Hz feedback only 84 with ideal
  intratrain gm K only
• 17 with 5Hz feedback only 70 with ideal
  intratrain gm K and all jitters
• Luminosity reduction is due to effects in BDS
  (not FD, not linac)
• More details see talk of Glen White
• These ILC simulations, as well as earlier
  simulations for TRC, allow to discuss stability
  goal for ILC systems

11
Discussion of ILC simulation results

• Linac (driving criteria is jitter)
• GM K or C is OK for linac
• If GM K or C, then linac component vibration 50nm
  is a bit too high, wish it to be no more than
  30nm
• BDS (driving criteria is luminosity)
• GM K or C is too noisy for BDS, wish to be 3
  quieter
• GM B is just fine for BDS, can allow 3 worse
• Component jitter 25nm too high for BDS, wish it
  would be lt 10nm
• For FD may allow several times larger, 100nm?
• Linac and BDS may have different specs for
  on-the-floor noise
• the noise consist of ground noise noise from
  nearby utilities, which are different in linac
  and BDS areas
• BDS area may be located in a quieter place than
  linac average
• Goals for tunnel floor stability add. component
  jitter
• Linac up to gm K or C up to
  30nm
• BDS up to gm B3 or gm C/3 up to 10nm

12
How to divide vibration budget?

• Let say the requirement for on the tunnel floor
  stability in linac area is ground motion C (and
  gm C /3 in BDS)
• This motion includes
• natural ground motion of the site
• added noise by ILC conventional facility and
  other nearby equipment
• One can set the budget for added noise to be
  1/20.5 of gm C and require initial site to be
  also 1/20.5 of gm C, but this way may show
  limitations in the future
• We may discuss another approach, when initial
  site motion is significantly more quiet than gm
  C, and all vibration budget is given to CF and
  other added noise

13
10 nm goal for BDS component jitter

• FFTB quad
• Small (2nm at 5Hz) difference to ground (on
  movers, with water flow, etc.)
• Lower frequency is relevant for 5Hz machine
  (0.2-0.5Hz) but was not studied accurately
• The 10nm goal may be achievable (for BDS area in
  gm B to B3)

14
30 nm goal for linac components jitter

• Presently, there are insufficient data to find
  how challenging is this goal
• It appears to be 5-10 times below what was
  observed for vibration of quads in cryostats
• However, present observations were performed in
  very noisy environment of on-surface labs
• The measurement methods in-cold are difficult and
  just being developed
• Focused engineering can improve stability
  significantly
• Need to be optimistic and concentrate our efforts

15
ILC linac quad stability
HeGRP
TTF cryomodules, since 1995, were equipped with
vibration sensors. Studies at TTF were ongoing
in September 2002 1. At that time there was
still big uncertainty in the measured data, due
to not well determined calibration at cold
temperature, issues with sensor grounding,
measured spectrum being limited to lt100Hz,
etc. 1 Private communication with DESY
engineers Heiner Brueck and Erwin Gadwinkel.
cavity
quad
TRC R2 A sufficiently detailed
prototype of the main linac module (girder or
cryomodule with quadrupole) must be developed to
provide information about on-girder sources of
vibration.

• Recent progress in studies of quad stability in
  cryomodules
• use of piezo sensors
• use of wire position system

16
XFEL stability goals and ILC

• XFEL plan to achieve beam jitter goals by both
  using fast feedback and improving the cryomodule
  stability
• Beam jitter stability requirements 0.1s (or
  somewhat better)
• With 70 nm (rms) quad movement about 0.05s at
  linac end
• 11 transfer ground to quad assumed, may need
  redesign of present quad mounting in cryostat
• Measurements of quad vibration in cryostat not
  yet conclusive
• XFEL WG-Minutes, Oct.2003, http//xfel.desy.de/xf
  el/content/e154/upload/upload_file/Meetings/WG-Min
  utes

17
XFEL
Ground motion along XFEL site
XFEL beam optics to end of linac
R.Brinkmann, ESFRI XFEL Workshop 30/10/2003

• XFEL is shorter and has less quads than ILC
  linac, but focusing is stronger, more quads per
  km gt jitter effects are comparable

70nm ground motion jitter gt 0.050 s 120nm quad
jitter gt 0.086 s
XFEL
gt 0.1 s goal
ground motion K gt 0.33 s 30nm quad jitter
gt 0.37 s
gt 0.5 s goal
ILC
Factor of 4
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WPM to measure cryomodule vibration

• A. Bosotti et al. PAC2005 use of WPM (wire
  position monitors)
• difficult task, complicated by vibration of
  wire
• Qualitatively, observed less motion near the
  support post
• Data are preliminary
• Normalization?
• e.g. blue at 10Hz0.9 mm left plot14nm right
  plot

A.Bosotti et al., PAC2005
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Vibration study at TTF in cold

• Heiner Brueck et al., TESLA Meeting, Hamburg
  03/31/2005
• Piezo sensors (cold) at the quad, in X and Y
  directions
• Sensors on top of the module, on ground,
  support, geophone

Heiner Brueck, et al.
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TTF vibration study pump modification

• Decouple pump from cryomodule, use flexible pipe
  and foam under the pump

Heiner Brueck, et al.
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TTF vibration study vertical

• With or without pump modificationgt improvement
• Quad vibration about 3 tunnel
• Low f noise of electronics
• Horizontal motionabout twice larger
• Also studies forcedvibration of HERA dipole
  cryostat observed strong (10) resonance at
  14.5 Hz
• Midnight data may be close to XFEL goal, overall
  may need up to a factor of 2 improvement to reach
  0.1s stability goal at XFEL (not relying on
  feedback)
• For ILC would need factor of several improvement

Heiner Brueck, et al.
22
Next slides

• Briefly review
• site studies
• FD stabilization
• sensors for IR
• noise propagation
• equipment noise
• etc.
• Also discuss issues of IR and common collider
  hall stability

23
Site stability studies
Mine near FNAL

• Many places around the world

LHC P4
KEK
Ellerhoop
Near SLAC
Near KEK, Kita-Ibaraki
Ellerhoop
24
Stabilization studies
SLAC 1996

• Experience invaluable
• Components of developed hardware may be
  applicable

DESY 1995
CERN, now Annecy
UBC
Extended object SLAC
SLAC
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Development of sensors for IR

• Nonmagnetic inertial seismometers
• SLAC home built low noise, as good as Mark4
  geophone or better
• Molecular Electronic Transfer sensor low
  noise, tested in 1.2T field, but cannot be
  cooled
• Interferometer methods
• Will need to use these or more advanced sensors
  to monitor FD motion

SLAC, UBC, etc
PMD/eentec
SLAC
26
Vibration transmission

• LA twin tunnel between tunnels and from surface
  (figs shown)
• Results are valuable for ILC

Mobility (response / driving force) measured in
LA metro twin tunnel test and modeled with 3D
code SASSI.
27
Vibration isolation of vibration sources

• Should be a standard practice for ILC

Vibration on the floor vs distance. For chiller
on springs, its vibration effects are
indistinguishable on the floor.
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Stability of the common collider hall

• Baseline has two Beam Delivery Systems, two
  collider halls separated in z by 130m, for two
  independent experiments
• The paradigm of two BDS, two IRs, two collider
  halls and detector is challenged and likely will
  be changed
• The considered alternative is single IR, single
  or two push-pull detectors, at least at the start
  of ILC
• plan of upgrade to two IRs need to be worked out
• Next slide will show an example with single
  14mrad IR at start
• Single collider hall is more challenging for IR
  stability
• With fast feedback, the FD stability goal is
  100nm
• It should be achievable for single collider hall
• Lower frequency 0.5Hz? Temperature stability?
• Monitoring of FD motion is needed

29
Upgrades IR stability
Tunnel stubs for beam dump
A
Tunnel stubs for future upgrades. At first stage
can be used as alcoves for diagnostics
electronics, lasers for laser wires, etc.
B

• Example of 14mr single IR and some of possible
  upgrades
• The cases B C may be more challenging for
  stability, as they may allow construction or
  assembly activity for second detector

C
30
FD magnet stability

• Stability of FD magnets need to be studied
• BNL preparing to measure stability of compact SC
  quads
• First results with CQS quad will be presented
  encouraging results
• Annecy group is aimed to study FD stability
  (simulation experiments) with BNL FD design
• Studies at ATF2 ?

RHIC CQS
Evolution of FD design with compact quads,
B.Parker et al
31
IR stability

• Vibration is not the only concern
• Temperature stability?
• Wakes heating the IR chamber and deforming it?
  During 1ms?
• SR should be well masked in IR, but may it cause
  deformations in other parts of BDS?
• Example of PEP-II IR heated by SR from LER and
  is moving by 0.1 mm as e current vary

min LER current
max LER current
Current of Low Energy Ring, slope of the girder
measured by HLS and wire, and reconstructed
position of FD magnets for min and max LER current
32
Intratrain feedback

• Low latency FONT invaluable for ATF2 facility
• ILC intratrain hardware optimization
• BPM location (background)
• kicker location (range)
• Number of intratrain feedbacks
• baseline is one at IP
• if linac stability is not achieved, may need
  multiple feedbacks along the ILC?
• How more difficult this will be? Was never
  studied in details.

P.Burrows, S.Smith, G.White at al
Angle scan
Position scan
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Fast feedback range

• If kicker of fast feedback upstream of SD0, for
  aperture reasons, nonlinear effects limit the
  safe range of fast feedback
• Kicker near SD0
• safe range of feedback 20 sX and 70 sY
• Kicker near QF1
• safe range of feedback5 sX and 10 sY
• May be possible to place kicker in-bore of SD0?

Near SD0
Near QF1
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Summary

• ILC stability goals for the beam, site and
  hardware suggested
• beam jitter
• 50 s at the end of linac (or in BDS diagnostics)
• 100 s at the end of BDS, before FD
• several s at IP
• Tunnel floor stability (site noise of nearby
  ILC equipment)
• Linac area up to gm K or C
• BDS area up to gm B3 or gm C/3
• Additional noise due to beamline components
• Linac area up to 30 nm
• BDS area up to 10 nm
• FD up to 100nm
• Need to discuss these goals, their feasibility
  and consequences
• Many other issues not discussed, e.g. long term
  stability