2nd ILC Accelerator Workshop Personal Impressions of a Beam Instrumentalist

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2nd ILC Accelerator Workshop(Personal
Impressions of a Beam Instrumentalist)

• Manfred Wendt
• Sept. 7, 2005

http//alcpg2005.colorado.edu/
Seminar on Beam Instrumentation Techniques and
Technology
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Organization and Statistics

• Working Fields
• Detector
• Physics
• Accelerator (2nd ILC Accelerator Workshop)
• Education and Outreach
• Participants (1st week)
• 650 total ( 80 Fermilab)
• 250 accelerator experts
• 1520 typical GG/WG attendance

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Accelerator Working Groups
WG1 LET Beam Dyn. WG2 Main Linac WG3a
Sources WG3b DR WG4 BDS WG5 Cavity WG6
Communication
Sub-System WG
Global Group
GG1 Parameters GG2 Instrumentation GG3 Operations
Reliability GG4 Cost Engineering GG5
Conventional Facilities GG6 Physics Options
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• 1st Week
• Plenary Presentations (Mo, Fr)
• Parallel Session Talks (Tu, We, Th)
• 2nd Week
• WG Discussions (MoTh)
• Plenary Presentations (Fr)
• Special Events
• 7x Lunch-Time Seminars
• Evening Events, Discussions, Dinner,

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The GDE Plan and Schedule
2005 2006 2007 2008
2009 2010
Global Design Effort
Project
LHC Physics
Baseline configuration
Reference Design
Technical Design
ILC RD Program
Bids to Host Site Selection
International Mgmt
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ILC Goals and Parameters

• Ecm adjustable from 200 500 GeV
• Luminosity ? ?Ldt 500 fb-1 in 4 years
• Ability to scan between 200 and 500 GeV
• Energy stability and precision below 0.1
• Electron polarization of at least 80
• The machine must be upgradeable to 1 TeV

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Configuration Parameter Space
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48 BCD Questions (Himels List)

• 2. Beam and luminosity parameters?
• 3. SCC starting gradient and upgrade path?
• 4. 1 or 2 IRs?
• 5. 1 or 2 tunnels, deep or shallow?
• 6. DR size and shape?
• 7. e source conv., undulator, compton?
• ...
• 29. How many diagnostic sections in the linac?
• 33. MPS design?
• 35. Use structure (HOM) BPMs?
• 43. Re-entrant or cavity BPMs for the main
  linac?

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Global Group 2Instrumentation Controls

• Conveners
• Marc Ross (SLAC), Hans Braun (CERN), Junji
  Urakawa (KEK)
• Presentations
• S-Band Cavity BPM for ILC Linac, Zenghai Li
• Cold Linac BPMs, Manfred Wendt
• Cold BPM Options, Olivier Napoly
• Cold Re-entrant BPM, Claire Simon
• ILC Cavity BPMs, Steve Smith
• ILC Laserwires, Grahame Blair
• Survey and Alignment of ILC, Armin Reichold
• Beam Based Feedback Systems, Phil Burrows
• High Availability Electronics Standards for
  ILC, Ray Larsen
• Stabilization of the Final Focus, David Urner

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Beam Position Monitors

• Cold Linac BPMs
• 2 x 400 dedicated re-entrant cavity or CM-free
  cavity BPMs
• 2 x 10000 HOM (structure) monitors for beam
  displacement (???)

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Simple Pill-Box Cavity BPM

• Problems
• TM010 monopole common mode (CM)
• Cross-talk (xy-axes, polarization)
• Transient response (single-bunch measurements)
• Wake-potential (heat-load, BBU)
• Cryogenic and cleanroom requirements

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CM-free Cavity BPMs

• KEK ATF nanoBPM
• collaboration
• BINP cavity BPM
• C-Band (6426 MHz)
• 20 mm aperture
• Selective dipole-mode waveguide couplers
• 3 BPMs in a LLBL hexapod spaceframe (6 degrees
  of freedom for alignment)
• Dual-downconversion electronics (476 25 MHz)
• 14-bit, 100 MSPS digitizer

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BPM ASSEMBLY
BPM struts
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• Beam Parameters
• Qbunch 1.5 nC
• sx 80 µm
• sy 8 µm
• sz 8 mm (!)
• ?E/E 5 E-4
• Jitter
• - sx 20 µm
• - sy 3.5 µm
• - sx 1000 µrad
• - sy 2 µrad

• Signal Processing
• Digital Downconversion
• Multiply digital waveform by complex local
  oscillator eiwt
• Low-pass filter (currently 2.5 MHz B/W)
• Sample complex amplitude of position cavity at
  peak
• Divide by complex amplitude from reference cavity
• Scale/rotate by calibration constants
• Refine calibration with linear least-squares fit
  to other BPM measurements, e.g. y2pred
  f(y1,y3,x2)
• Removes beam jitter, rotations, cal. errors.
• Monopole modes appear as offset in (I,Q) space
  (as do mixer offsets, rf leakage).

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• 10 minute run
• 800 samples
• s 24 nm

Move BPM in 1 µm steps
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Cavity BPM Shapes
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KEK Cavity BPM

• Very compact design to save space
• Waveguide has fold, asymmetry
• Differs from BINP design
• BINP BPM has long waveguide taper to coax adapter
• KEK coax adapter is very close to cavity

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X2
Y1

• KEK group sees 70 nm resolution
• Also X-Y coupling
• Monopole mode leakage

Y2
X1
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Re-entrant Cavity BPM

• Coaxial cavity BPM
• Evanescent fields of the TE11 dipole mode
• Very low Q 4
• Cryogenic and cleanroom approved

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• Improved re-entrant BPM design
• Better to be cleaned (12 holes)
• More reliable feedthrough construction

• Reduced damping
• Qdipole 52 (fdipole 1.72 GHz)
• Qmono 24 (fmono 1.25 GHz)
• Expected single-bunch resolution 1 µm

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Q43 Re-entrant or Cavity BPM?

• Answer Not yet decided, RD required!
• Re-entrant BPM meets cryogenic and cleanroom
  requirements, but has limited resolution.
• CM-free cavity BPM meets resolution
  requirements, but has to show cryogenic and
  cleanroom compatibility.
• The required single-bunch resolution was set by
  GG2 to s/3 0.5 µm for diagnostic purposes, WG1
  (LET) assumes 110 µm BPM resolution.

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Accelerating Cavity HOM Couplers as BPM (HOM-BPM)

• Naturally narrow band cavity QL 104 , ?? 1
  µs
• single bunch,
• but not bunch to bunch BPM

• Relative position resolution 4 µm (cf. M. Ross
  and J. Frisch).

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Centering accuracy lt 40 µm, using a single mode
(2 polarisations)
Angular scan resolution and accuracy lt 50 µrad
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High Availability Electronics
ATCA Telecom System A0.99999

• 2 Control 12 Applications slots
• Up to 200 W/module at 45ºC ambient, 2.8KW Shelf
• Redundant speed controlled DC fans

Mezzanine Card Option 3x7inch Hot Swappable Up
to 8/Mbrd
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Data Acquisition Controls
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Personal Impressions

• Many beam instrumentation collaborations in
  progress
• SLAC, KEK, LLNL, LBL, nanoBPMs at ATF
• SLAC, DESY HOM-BPM at TTF
• CEA-Saclay, DESY Re-entrant BPM at TTF
• SLAC, DESY LOLA long. bunch profile at TTF
• SLAC, Uni London (QM) Fast IP feedback at the
  SLAC Linac
• Uni London (RH), JAI, DESY Laserwire trans.
  profile at PETRA
• Very good working atmosphere!
• Technology choice (1.3 GHz SC Cavities) accepted!
• SLAC seems to me very active(!), not only in the
  field of beam instrumentation.