Recent lattice developments in the antiproton source

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Recent Lattice Developments in the Antiproton
Source
Vladimir Nagaslaev, AD/Pbar
Accelerator Physics and Technology
seminar Fermilab, May 17, 2007
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Recent lattice developments in the antiproton
source
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• Introduction Recent efforts to improve the pbar
  production
• Accumulator ring
• Debuncher ring
• Beam lines
• 8 GeV transport Accumulator-gt Recycler
• 120 GeV proton transport to the target
• 8 GeV antiprotons from the target
• D/A line

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Introduction Recent efforts to increase
production
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• Main events I will be referring to
• Study period in November-December 2005 (15 days
  RevP)
• Study period in January 2006 (1 week of RevP) ?
  stacking record
• Fast transfers to RR through 2006 -gt average
  production records
• New wave of stack-tail studies, 2006-2007, new
  stacking records

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Introduction Recent efforts to increase
production
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• Accumulator
• Stacktail
• Machine admittance

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Introduction Recent efforts to increase
production
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• Debuncher studies
• Aperture improvements

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Introduction Recent efforts to increase
production
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• 8 GeV pbar transport to RR
• Fast transfers
• Matching stability

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Introduction Recent efforts to increase
production
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• 120 GeV p transport to the target
• orbit stabilization (bpm filters)
• beam sweeping/ reducing beam size

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Introduction Recent efforts to increase
production
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• AP2 line, transport from the target
• Apertures, orbits
• Chromaticity
• Lens collection efficiency

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Optics of the Accumulator ring
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Cyan After injection before RF capture Green
After RF is turned off
Accumulator operation

• Inject to 80 MeV
• RF move to deposition
• Cool to Core -60 MeV
• Unstack to extraction
• Extract to Recycler

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Optics of the Accumulator ring
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• Main features
• Momentum aperture
• Large dispersion in arcs
• Narrow aperture in straights

• Objectives
• Stack stability and emittances
• Optimal cooling
• Cooling rates
• Low heating
• Low D in straights
• Chromaticity
• Effective aperture

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Accumulator optics model development
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• Moving to OptiM based model
• GUI based
• Interactive analysis tools
• Continuing development
• LOCO

• OptiM file commissioning, main items
• Quad excitation curves
• Corrector activation
• BPM position adjustments
• Multipoles excitation
• Multipole expansions for
• dipoles, sext, oct, LQ-quads
• Mechanical apertures
• Survey checks and corrections
• Variable corrections to elements
• Input from the PS file
• LOCO- friendly dialog

• Model development
• develop optics file
• data acquisition
• fit model parameters
• optimize the lattice

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Chromaticity tunes across momentum aperture
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• New application for tunes vs momentum
  measurement
• Large variation full scale 0.05 (2/3
  5/7)
• Octupole/sextupole corrections

A complete optics model of the Accumulator has to
reflects such chromaticity correctly
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Chromaticity in the Accumulator optics model
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• SMA-multipole
• Sextupole Octupole
• Contains also many others

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Chromaticity higher orders in SMA magnets
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Fit octupole field in median plane using
10-16-poles
Use those corrections to calculate sextupole field

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Chromaticity higher orders in SMA magnets
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Calculated tune shifts across aperture (Horz)
Sextupole and octupole corrections to the
tunes used to compare with existing model
All corrections were used in a linear fit to
measured tune dependence on momentum.
Higher order fields in the SMA magnets are
at least order of magnitude smaller than that to
fit the measured tunes vs Dp
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Chromaticity higher orders with LQ quads
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Higher order tune corrections with LQD and LQC
quads
Nonlinear chromaticity may be artificially
introduced in HD magnets Best choice of the
model can be taken after comparing with
measurements
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Model Slip factor vs momentum aperture
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Measured hc vs model calculation Base line may
be not well tuned Good agreement except the edges
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Model development Measurements
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• Data acquisition
• Goal response matrix (RMm)
• 1-bump orbits taking all correctors
• Multiple sampling and both polarities
• Dispersion measurement with multi-step momentum
  variation
• Typically takes 1.5 hour
• Special application P165 common for all
  machines

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Lattice measurements Dispersion
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Moving beam in steps of Dp/p0.05
dD 1mm
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Lattice measurements LOCO analysis
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• LOCO Linear Optics for Closed Orbits
• Takes arbitrary number of variables
• Quad errors
• BPM corrections
• Correctors, quads, bpms rolls
• PS, magnet type corrections
• Anything else, that can be included in the
  model
• Calculates response matrix (RMC) from the model
• Calculates derivative matrix for RMC on the
  vector of variables
• Calculates inverse matrix using SVD
• Solves linear equation for variables iterates
  to fit RMC to RMM
• Uses parallel processing on the Heimdall Linux
  farm
• Adopted for Pbar, Recycler and Tevatron

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Lattice measurements LOCO analysis
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Optimizing SV limit (Debuncher
example) Controls leverage of fineness/degenerac
y Rule of thumb SVmin 1
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Lattice measurements LOCO analysis
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• RM fit
• Varying
• quads (localglobal)
• correctors
• BPMs

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Lattice measurements LOCO analysis
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Residual errors sx15 m sy 6m
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Lattice measurements LOCO analysis
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BPM calibration
Different types of BPMs
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Lattice measurements LOCO analysis
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Horizontal BPM calibration check with scrapers
10 for BPHx14 agrees with LOCO calibration
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Lattice measurements LOCO analysis
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• Position correlations
• per BPM
• per Corrector
• low statistics

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Lattice measurements LOCO analysis
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Gradient errors Global component reduce
periodic component Degenerate solutions
not real, but do not affect optics
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Optics optimization for the stochastic cooling
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• New design objectives
• Slip factor increase by 15
• helps stochastic cooling
• mitigates 3.25GHz resonance
• Transverse heating
• Suppress dispersion in straights
• Lower beta-functions (IBS)
• Apertures
• Reduce beam size at tight locations

H5168 (3.25 GHz)
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Accumulator apertures
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• Feb 2006 studies
• Improved admittance 10
• Still smaller than in 1999
• Feb. 2007 Ax8.0p Ay7.1p
• Few narrow places identified
• DCCT (12.8p H)
• Injection (11.3p H)
• WBPU (11.3p H)
• CM48K (13.5p H, 13.5p V)
• SM24P (14.3p V)
• New lattice objective increase
• design aperture to 15p everywhere

Aperture search with Running wave is
pointing to the stochastic cooling tanks in
straight 30 sector
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New lattice design
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• Approach
• Dispersion in negative wells
• Beam line regime
• Iterations
• New shunts needed for vertical
• corrections

• Changes
• Slip-factor change (0.013?0.015)
• Lowering beta-functions (12for IBS)
• Apertures ? 15p (now min 11p)
• Dispersion in straights 15cm-gt 2.5cm
• Phase advances
• Symmetry

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New lattice implementation
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• 1st try April 24
• Different hysteresis conditions no
  mini-ramps
• Tunes far off
• Compaction factor grossly off
• 2nd try May 1
• Correction consistent with before-mini-ramps
  experience
• From lattice measurement and fit compaction
  factor seems right
• 3rd approach May 9
• New lattice (corrected dispersion in straight
  sections)
• Cross-measurements of compaction factor and
  gamma-t
• Measurement and dispersion correction on core
  orbit
• 4th approach Yesterday!

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Have you been in MCR yesterday afternoon?
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• Whats good
• Ramp, inject, move flawless (already well
  trained)
• Horizontal dispersion on core very good
• Slip factor very close to design
• Whats not so good
• Vertical dispersion !
• Orbit moved ?
• Admittance down (not much)
• Strong coupling
• How it is progressing
• LOTS of changes and tuning
• Emittances seem to like new lattice
• Best stacking so far ove 20mA/hr, but
• Long way to go

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Optics of the Debuncher
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Debuncher operation
Fast antiproton beam compressing in 6D Bunch
rotation, 3D cooling 10 in each plane in a 2.4
sec cycle
Debuncher lattice
57 FODO cells, 60o Dispersion cancelling 330p
transverse admittance 4.5 momentum aperture
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Optics of the Debuncher chromaticity
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• Chromaticity
• Large momentum spread
• 2 families of sextupoles in arcs
• Tunes vs Dp/p
• Fit 6- and 10-pole harmonics in dipoles
• Included in the model

Chromaticity of functions No problem for
injection matching No dynamic aperture limitation
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Optics of the Debuncher model
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Debuncher aperture optimization, January 2006

• Model development
• File (K. Gollwitzer)
• Data acquisition
• LOCO fitting
• Lattice optimization (V.Lebedev)

Best acceptances in 2005
30p/25p (design 34p/31p) Best acceptances
in January 2006 35.3p/34.6p
(40.5p/37.5p)
(as measured!)
Lattice optimization also eliminated the need to
redesign b4 tanks
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AP3-P1 8 GeV antiproton transport to RR
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• Rapid Transfers Effort
• wider beam
• larger momentum spread
• Eventually
• very fast
• no tune ups
• need to be stable
• and well matched

• Directions
• Beam quality from Accumulator
• BPM upgrade 2.5 MHz, sensitive to pbars
• Steering to aperture center, forward
  corrections
• MI dampers
• Lattice measurements/matching

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AP3 8 GeV antiproton transport to RR
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• Measurements
• using 4 orbits dispersion
• this time in both p and pbar directions
• manual fitting

Big effect of EQ2
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AP3 8 GeV antiproton transport to RR
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AP3 8 GeV antiproton transport to RR
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Better matching quad oscillations substantially
reduced Improved lifetime at injection in
Recycler helped overall Transfer efficiency
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AP2 transport from the target to Debuncher
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• Large efforts in 2005-2006 towards improving AP2
  aperture
• BPMs upgrade
• Orbit centering to quad centers
• Orbit stabilization
• Steering around injection
• New correctors installed Jan 2006
• Lattice update to match Debuncher - Dec 2005, Jan
  2006
• Collection efficiency
• Chromaticity

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AP2 collection at the target
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• Collection optics optimization
• Matching to Debuncher lattice
• Minimizing beam size at first triplet
• Target positioned at focusing point
• Optimum focusing
• Optimized for aperture

• Simulations and tracking
• Optimum at b1.5cm
• not reached yet

• Experience
• increase 640-gt760 T/m
• 760-gt830T/m no increase?!
• room for improvement will be
• investigated

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AP2 chromaticity
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Substantial chromaticity of twiss functions
LBL analysis up to 5 more yield with chromatic
corrections using sextupoles V.Lebedevs
analysis very strong correction at the
end overall yield in gain is 1.2
Technically questionable Hardly worthy
resource wise
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AP2, corrections to dipole fields
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• SDEW magnet maps
• Magnets designed for different R
• Magnets modified to larger Y-space
• No data for field expansion
• Used OPERA calculation
• Corrections are at few level
• Field fit with multipoles 20th order
• built in the optics model for tracking

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AP1 120 GeV protons to the target
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AP1 beam sizes (en20p)
Only questioned in recent past in terms of
the beam spot size on the target
Beam spot is measured with the SEM wires
Optimum 150m, not reached yet because of the
target damage Successful implementation of
partial beam sweeping recently
will try to reduce the beam size
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120 GeV p transport target damage
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D/A line
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• Beam steering to quad centers was done
• Application for injection closure in the
  Accumulator
• Lattice matching -gt Dispersion not matched!
• Planning to do optics measurement using TBT in
  Debuncher

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Summary
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• New paradigm implemented for lattice
  development
• OptiM vs MAD
• Differential orbits
• LOCO
• Model development in the Accumulator lead to
  optimizations
• aimed to help stochastic cooling
• Model developments in the Debuncher lead to
  aperture increase
• Based on recent instrumentation advances in the
  beamlines
• Better matching achieved in AP3-P1 line,
  resulting in improved
• efficiency
• AP1 beam spot size is being optimized
• AP2 lattice has been measured and matched
• D/A measurement is pending
• None of these tasks is complete, this is work
  in progress