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Energy Spectrometer R&D; Plans for End Station A Test Beams. Mike Hildreth University of Notre Dame ALCPG, March 22, 2011. Precision Beam Measurements. Precision Physics Measurements require precise determination of beam parameters – How well do we have to do?

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energy spectrometer r d plans for end station a test beams

Energy Spectrometer R&D;Plans for End Station A Test Beams

Mike Hildreth

University of Notre Dame

ALCPG, March 22, 2011

Mike Hildreth – ALCPG 2011, Beam Instrumentation

precision beam measurements
Precision Beam Measurements

Precision Physics Measurements require precise determination of beam parameters – How well do we have to do?

Luminosity, Differential Luminosity Spectrum:

  • Total cross sections: dL/L ~ 0.1%
  • Lineshape scans (Giga-Z) dL/L ~ 0.02%
  • Threshold scans (e.g., mtop) dL/L ~ 1%, but additional constraints:

dL/dE core to 0.1%, tails to ~1%

Energy:

  • top, higgs masses <100 ppm
  • W mass with threshold scan 50 ppm (4 MeV)
  • ALR with Giga-Z 200 ppm (comparable to 0.25% Pol)

50 ppm (if dP/P ~ 0.1%)

Polarization:

  • Standard Model Asymmetries dP/P < 0.25%
  • ALR with Giga-Z dP/P < 0.1%

Mike Hildreth – ALCPG 2011, Beam Instrumentation

energy measurements
Energy Measurements
  • A few words of Motivation...
    • Energy Calibration needs for Physics at a future Linear Collider will be similar to what we had at LEPII:

Threshold Scans:

Kinematic Fits:

Mike Hildreth – ALCPG 2011, Beam Instrumentation

prototypical energy spectrometers
Prototypical Energy Spectrometers

p

BPMs

  • “LEP-Type”: BPM based, bend angle measurement
  • “SLC-Type”: SR stripe based, bend angle measurement

 “upstream”

Aim for 10-4 Energy Measurement

 “downstream”

Mike Hildreth – ALCPG 2011, Beam Instrumentation

e g ilc upstream energy spectrometer
e.g.: “ILC” Upstream Energy Spectrometer

3

3

16.1

16.1

M. Hildreth (Notre Dame), SLAC

  • Pure “Displacement” Strategy: Prototype Design
    • ILC design: total length of chicane = 54.4 m
    • dispersion at center = 5mm (~equal to beam displacement)
      • so, 0.5mm BPM resolution gives 1x10-4 measurement (per pulse)
    • CLIC Chicane requires 100nm resolution/stability
    • Designs incorporated into Accelerator Lattices

Central BPMs measure offset, offset difference between ±B (cancel some systematic errors)

all magnets run to ±B

Incoming Beam

5 mm

Outer BPMs required to constrain beam trajectory

better resolution would allow intra-train bunch energy measurements

Mike Hildreth – ALCPG 2011, Beam Instrumentation

history esa test beam experiments
History: ESA Test Beam Experiments
  • BPM Energy Spectrometer (T-474/491)
    • PIs: M. Hildreth, Notre Dame, S. Boogert, Royal Holloway, Y. Kolomensky, Berkeley/LBNL
    • Institutions: Cambridge, DESY, Dubna, Royal Holloway, Notre Dame, UCL, Berkeley, SLAC
    • Goals:
      • Demonstrate mechanical and electrical stability at 100-nm level
      • Perform energy measurement in 4-magnet chicane
      • Develop calibration techniques, operational procedures
    • multiple BPM triplets to test overall stability, new BPM designs
  • Synchrotron stripe diagnostics (T-475)
    • PI: E. Torrence, Oregon
    • Institutions: Oregon, SLAC
    • Goals:
      • test chicane scheme with wiggler magnet
      • characterize detector (quartz fiber / other) performance and capabilities

Overall Goal:

perform cross-check of two energy measurements at the ~10-4 level

Mike Hildreth – ALCPG 2011, Beam Instrumentation

t474 t491 t475 energy spectrometers
T474 (T491), T475: Energy Spectrometers
  • BPM-based and Synchrotron-Stripe Spectrometers can be evaluated in a common four-magnet chicane

Synchrotron Stripe Detector

Wiggler

BPMs

Dipole

Mike Hildreth – ALCPG 2011, Beam Instrumentation

fy07 configuration
FY07 Configuration

Wiggler

  • Ran in 2006 with no dipole chicane
  • Runs in March, July 2007 with chicane
  • Simultaneous test of BPM and Synchrotron Stripe Spectrometers
    • first beam tests for Synchrotron Detector
    • compare measured energy, energy jitter at 100-200ppm level
    • tests of BPM movers
    • more elaborate mechanical stability monitoring

BPMs

Interf. Station

BPMs

BPMs

Dipoles

Dipoles

Straightness Monitor

Mike Hildreth – ALCPG 2011, Beam Instrumentation

energy measurement with chicane 2007
Energy Measurement with chicane (2007)
  • Beam energy computed from spectrometer Bdl and BPM offset measurement vs. time
    • energy variation from linac energy scan
    • large pulse-to-pulse jitter
  • Residual between predicted and measured BPM position at chicane center gives a value sE ~16 MeV (DE/E ~ 5.5×10-4)
  • need higher-precision test

A. Lyapin et al., “Results from a Prototype Chicane-Based Energy Spectrometer for a Linear Collider”, JINST 6 (2011) P02002.

Mike Hildreth – ALCPG 2011, Beam Instrumentation

mechanical stability
Mechanical Stability

Interferometer heads

Local motion measurement

BPM

Long Baseline Monitoring

  • Stability requirements determined by overall BPM resolution needed
  • Mechanical support structure must be designed to limit vibration, and with minimal thermal expansion properties
    • Custom temperature regulation needed...
  • Stability must be monitored: Interferometry-based system
  • Zygo 4004 Measurement System
    • Design Specs:
      • 0.3 nm single-bit resolution
      • at up to 5 m/s velocity
      • single measurement ~ 7nm

Mike Hildreth – ALCPG 2011, Beam Instrumentation

atf2 installation
ATF2 Installation

Optical Path

BPM MFB2

BPM

QD10A

QD10B

QM11

QM12

QM13

QM14

BPMs MFB2 and QD10B are part of vertical steering feedback for beam stability at ATF2 IP. Need resolution  stability of ~ 50nm

optical path uses clearance between mover rollers underneath quads

As of October 2010: three interferometers monitoring three BPMs

Mike Hildreth – ALCPG 2011, Beam Instrumentation

results from atf2
Results from ATF2

data acquisition at 1 kHz

Time (sec)

vibration data on BPM QD10B. rms = 35nm

one micron

Time (sec)

36-hour drift on BPM QD10B. scale is nm.

QD10B

Mike Hildreth – ALCPG 2011, Beam Instrumentation

retroreflector

CCD camera

interferometer

results from atf21
Results from ATF2

“Features” of FFTB mover stability:

  • “Relaxation” of mechanical position of BPM MFB2 after calibration move, measured by interferometer
  • No corresponding drift seen simultaneously on other BPM support with no mover motion
  • analysis ongoing to trace relative beam/BPM motion to prove that this is a physical movement

BPM MFB2

position (mm)

ZYGO MFB2

position (nm)

position (nm)

500nm

Time (sec)

Time (sec)

50 micron FFTB mover calibration step

(other studies ongoing: CCD camera stability, interferometer triplet stability/resolution, etc.)

Mike Hildreth – ALCPG 2011, Beam Instrumentation

end station a plans schedule
End Station A Plans/Schedule

M. Pivi, SLAC

0.25 nC

0.25 nC

  • News from ESTB (End Station Test Beam) Workshop at SLAC, March 17, 2011
    • many participants: global interest in high-purity electron test beam

Mike Hildreth – ALCPG 2011, Beam Instrumentation

end station a plans schedule1
End Station A Plans/Schedule

4 new kicker magnets including power supplies and modulators and vacuum chambers are designed and components are being ordered and manufactured

Build new PPS system and install new beam dump

Mike Hildreth – ALCPG 2011, Beam Instrumentation

end station a plans schedule2
End Station A Plans/Schedule
  • The complete 4 kickers system will not be ready until the end-of-summer 2011. Short-term solution, installed ~now
    • 1 Kicker magnet with stainless steel chamber
    • Beryllium target
    • System designed for 60 Hz, might work at 120 Hz
    • Capacity:
      • 4 GeV full intensity LCLS beam into ESA.
      • 4 - 13.6 GeV primary beam into target and generate secondary e- beam to ESA, 0.1/pulse to 109/pulse.
  • By November 2011: Installation of the full 4 kicker magnet system to direct the LCLS beam in ESA.
    • Full 14 GeV LCLS beam into ESA
    • Production of secondary electron beam down to 1 e- / pulse.
    • Future (unfunded) option: secondary hadron beams

Mike Hildreth – ALCPG 2011, Beam Instrumentation

end station a plans schedule3
End Station A Plans/Schedule
  • Critical (for Spectrometers and other tests):need precision BPMs
    • previous BPM sets no longer available
    • discussion with LCLS-II, other international sources ongoing
      • LCLS-II and Korean FEL both need new precision BPMs
      • maybe some joint venture that involves loaning BPMs to ESA for testing and commissioning before they are needed for light sources
    • would provide uniform high-precision installation, which would be very beneficial for understanding the analyses
    • time-early would be end of 2012

Mike Hildreth – ALCPG 2011, Beam Instrumentation

summary
Summary
  • Termination of ESA program in 2008 limited the current level of precision for spectrometer testing to DE/E ~ 5.5×10-4
    • factor 5 larger than what is needed
    • will need to revitalize the End Station setup to improve on this
  • ATF2 installation exploring stability issues at the 100nm level
    • 50nm BPM resolution plus 7nm interferometer resolution plus ~100nm long-range stability monitoring is a powerful system to constrain mechanical motion
    • analysis needed!
  • ESA Returns!
    • BPMs needed
    • probably 2012 before spectrometer tests can be mounted

Mike Hildreth – ALCPG 2011, Beam Instrumentation

interferometer data from end station
Interferometer Data from End Station

condense

  • Vibrations with amplitudes close to or exceeding expected BPM resolution seen on support girder
  • Synchronous data acquisition allows interferometer measurement of BPM position to be subtracted in later data analysis
  • Resolution of central BPM improved by ~700nm (added in quadrature) after vibration subtraction

500nm

500nm

BPM support girder clearly needs to be redesigned if we want to do any sort of stability testing...

Mike Hildreth – ALCPG 2011, Beam Instrumentation

bpm performance and stability 2006
BPM Performance and Stability (2006)

0.6

0.6

0.4

0.4

0.2

0.2

0

0

-0.2

-0.2

-0.4

-0.4

-0.6

-0.6

Stability of predicted position

Residual mm

s ~ 350nm

100nm

Residual mm

s ~ 700nm

100nm

Mike Hildreth – ALCPG 2011, Beam Instrumentation

upstream energy spectrometer
Upstream Energy Spectrometer

M. Hildreth (Notre Dame), SLAC, Cambridge, UCL, Royal Holloway, LBNL/Berkeley, DESY-Zeuthen, Dubna

  • Design Details:
    • Constrained by allowed emittance growth from Synchrotron Radiation
      • hard bending at points of large dispersion gives large emittance growth  Any bend magnets inside chicane need to be “soft”
    • Constrained by available real estate in Beam Delivery Syst, overall size
      • Relative positions of components need to be monitored
        • limits total size to ~50 m
      • These constraints determine needed BPM resolution/stability
        • overall design for BPM resolution of ~0.5mm
        • can always average over many pulses if things are stable
        • if we do much better, bunch-by-bunch diagnostics possible
    • Other issues drive systematic errors, diagnostics

 Complicated dependence on design parameters, options

    • Must be robust, invisible to luminosity

Mike Hildreth – ALCPG 2011, Beam Instrumentation

interferometer installation
Interferometer Installation

July 2006 March 2007

Mike Hildreth – ALCPG 2011, Beam Instrumentation

bpms and electronics
BPMs and Electronics
  • SLAC Linac BPMs form main component of instrumentation
    • new electronics developed by Y. Kolomensky (Berkeley/LBNL)(LCRD Accelerator R&D)
  • Also testing prototype ILC Linac BPMs developed at SLAC (C. Adolphsen)
  • New BPMs, optimized for energy spectrometer, designed at University College London in collaboration with BPM experts at SLAC and KEK
    • custom electronics
    • mover system
    • July 2007

Linac rf cavity BPM

ILC Linac BPM

Mike Hildreth – ALCPG 2011, Beam Instrumentation

beamline components
Beamline Components
  • Dipoles: Measured in SLAC Magnet Lab prior to installation

(SLAC/Dubna/Zeuthen)

    • RMS Reproducity of field integral: 60ppm
    • RMS Agreement across working points: 100ppm
    • Temperature coefficient: 5.7x10-5/°C
    • Excellent agreement between measured and simulated magnet properties
    • Also: measurements made of residual magnetic fields along entire beamline (Bdl ~ 3 Gm)
  • Wiggler refurbished – now installed

Mike Hildreth – ALCPG 2011, Beam Instrumentation

interferometer installations
July 2006

March 2007

Interferometer Installations

single BPM station

link two BPM stations

Mike Hildreth – ALCPG 2011, Beam Instrumentation