Muons, Inc.
Overview of
the Tevatron Collider
V.S. Morozov
Old Dominion University
Collider Review Retreat, Jefferson Lab, February 24, 2010
1
Outline
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Accelerator Complex Overview
Tevatron
Low- insertion
Electrostatic p/p
¯ beam separators
1st- and 2nd-order chromaticity control
Beam-beam effects
Instabilities
2
Accelerator Complex Overview
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30 September 2002
Elvin Harms - HCP 2002
3
Accelerator Complex Overview
f
– Proton source
•Cockroft-Walton preaccelerator 750 keV
4
Accelerator Complex Overview
– Proton source
• Drift tube Linac 116
MeV
f
– Proton source
• Side-coupled cavity
Linac 400 MeV
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Accelerator Complex Overview
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– Proton source
•Rapid-cycling Booster synchrotron 8 GeV
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Accelerator Complex Overview
f
• Main Injector/Recycler 8 to 150 GeV
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Accelerator Complex Overview
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• Antiproton source
– Antiproton production target station 120 GeV
– Debuncher 8 GeV
– Accumulator 8 GeV
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Accelerator Complex Overview
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• Tevatron
– Superconducting synchrotron 980 GeV
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Tevatron Loading scheme
f
• Protons are loaded first - 1 bunch at a time and spaced in 3
groups of 12 (20 empty buckets between bunches, 139
empty buckets between trains)
• Antiprotons are loaded four bunches at a time for a total of
9 transfers from the Accumulator to MI to the Tevatron
• The 36 bunches of Pbars are equally spaced in 3 groups of
12 around the Tevatron
Elvin Harms
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Tevatron Parameters
Synchrotron with superconducting magnets.
Collide 36 proton bunches on 36 pbar bunches.
Radius
1 km
Energy
150 Gev to 980 Gev
Lattice
6 identical 60º arcs with 15 FODO cells/arc
FODO cell
min = 30 m, max = 100 m, ~60º betatron phase
advance in both planes
Run with tunes at 20.575 (vertical) and 20.585 (horizontal).
h
1113
RF frequency
53.14 MHz
Bucket spacing 18.8 nsec
Low Beta regions at B0 and D0. * is 35 cm
Electrostatic separators to separate the proton and antiproton orbits.
772 dipole magnets with B = 4.4 Tesla @ 1000 GeV.
November 8, 2002
Fermilab Snapback Workshop
Mike Martens
11
Parameter List
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RUN
Ib (1993-95)
6x6
Run IIa
(36 x 36)
Current best
Protons/bunch
2.3 x 1011
2.7
2.1 x 1011
Antiprotons/bunch
0.55 x 1011
0.3
0.17 x 1011
Total Antiprotons
3.3 x 1011
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6.1
Pbar Production Rate
6.0 x 1010/hour
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12.4
Proton Emittance
23p mm-mrad
20p
20p mm-mrad
Antiproton Emittance
13p mm-mrad
15p
20p mm-mrad
35 cm
35
35 cm
900 GeV
1000
980
0.60 meter
0.37
~0.60 m
0 mrad
0
0
1.6 x 1031cm-2s-1
8.6
3.0
best-to-date
3.2 pb-1/week
17.3
4.3
~3500 nsec
396
396
2.5
2.3
2.3
*
Energy
Bunch Length (rms)
Crossing Angle
Typical Luminosity
Integrated Luminosity
Bunch spacing
Interactions/Crossing
30 September 2002
Elvin Harms - HCP 2002
12
Ingredients of Tevatron
Luminosity
• Low- insertions
• Reduction of beam-beam tune shift by
separation of p and p¯ beams on helical orbits
• Control of 1st and 2nd-order chromaticities
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Retrospective View
Talk by R. Johnson, ~1986
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Standard Cell in the Tevatron Lattice
F
D
T:QF
Horz
BPM
T:QD
T:SF
Tevatron Dipole
Vert
BPM
T:SD
Tevatron Quad corrector
(There are 772 Tevatron dipoles)
Tevatron Sextupole corrector
F
Tevatron Beam Position Monitor
Tevatron Quadrupole
November 8, 2002
Fermilab Snapback Workshop
Mike Martens
15
Low- Insertion
• Two low- insertions at B0 and D0
• 18 cold-iron quads arranged as a
triplet and 6 “trims” on each side of
interaction region
• Fully matched to lattice by “trims”
• Approximately symmetric around
interaction point
• Magnetic gradients antisymmetric
• Each insertion’s * independently
adjustable within 0.25-1.7 m range
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Low- Insertion
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•
•
Each insertion adds half unit to betatron tunes
Horizontal dispersion zero at interaction point
* limited by max, magnet’s bore tube and field errors
Inner quads specially designed to fit detector clearance
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Low- Insertion
• * of 35 cm prior to 2005
• New optics with * of 28 cm implemented in July 2005
based on precise knowledge of lattice details obtained using
Orbit Response Matrix (ORM) and Linear Optics from Closed
Orbit (LOCO) methods
• Gain in luminosity of ~10%
• Further reduction of *
undesirable because of
2nd-order chromaticity and
hour-glass effect
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Low beta
Un-squeeze
Low beta
Squeeze
Inject porotns
& pbars
Tev Energy
Tevatron Ramp Cycle
150 Gev
Front Porch
980 Gev
flattop
150 Gev
Back porch
90 Gev
Reset
Time
• During injection and acceleration * kept at 1.7 m then “squeezed” to 0.28 m by
ramping trim magnets while triplet elements remain unchanged
• In fixed target runs low- insertions approximate “normal-” straight sections
Typical times for Tevatron store
• 150 Gev Front porch: ~2 hours
• 980 Gev Flattop:
~12-24 hours
• 150 Gev Back Porch: ~1 minute
• 90 Gev Reset:
~20 seconds
November 8, 2002
Typical times for dry squeeze
• 150 Gev Front porch: ~10 minutes
• 980 Gev Flattop:
~15 minutes
• 150 Gev Back Porch: ~1 minute
• 90 Gev Reset:
~20 seconds
Fermilab Snapback Workshop
Mike Martens
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Separation of Proton and
Antiproton Orbits
• Tevatron’s betatron tune working point between 4/7 and 3/5
resonance lines leaving 0.028 tune space available
• Beam-beam tune shift 0.025 for antiprotons and 0.02 for protons
• Unseparated beams  multiple crossing locations each
contributing to beam-beam tune shift  limited number of
bunches and beam intensity
• Keep beams separate everywhere except interaction regions with
electro-static separators
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Electro-Static Separators
• Function as “3-bumps” in vertical
and horizontal planes
• Bunches go in helical orbits
around unseparated orbit
• Orbits remain separated during
injection and acceleration
• Separators adjusted to bring
beams into collision at interaction
regions
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Electrostatic Separators
1986 talk by R. Johnson
1991 paper by D. Herrup et al.
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Chromaticity in the Tevatron
•
High chromaticity
- large betatron tune spread
- some beam loss on ramp (~15%).
•
Reducing chromaticity ma cause transverse instabilities
•
Keep chromaticities at 8 units (horz and vert) on front porch
Increase chromaticites to 12 units just before ramp.
Keep chromaticity at 15 to 20 units on the ramp.
•
Chromaticity drifts are created by drifting b2 (sextupole) fields in dipoles.
•
b2 compensation scheme keeps chromaticity constant at 150 Gev and on
the snapback (sort of.)
November 8, 2002
Fermilab Snapback Workshop
Mike Martens
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Chromaticity in the Tevatron
• The total chromaticity has several components
Total = Natural + Dipoles + Sext corr
Natural = -29 units (from optics calculations)
Dipoles = b2 drift + b2 geometric
Sext corr = T:SF + T:SD + C:SFB2 + T:SDB2
• 176 chromaticity correction sextupoles
Originally combined into two families, SF and SD
88 elements in each family powered in series
Sextupoles located next to quadrupoles of regular FODO lattice
November 8, 2002
Fermilab Snapback Workshop
Mike Martens
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Transverse Dampers
• Lower chromaticity by 4-6 units thus reducing betatron tune
spread and improving beam lifetime
• Use transverse dampers to keep beam stable
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nd
2 -Order
Chromaticity Correction
• Needed to move betatron tune
working point to new place near
1/2 resonance where there is more
tune space available
• Elimination of chromatic
dependence of beta function at IP
should improve beam lifetime
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nd
2 -Order
Chromaticity Correction
• Sextupoles with p or p/2 betatron
phase advance with respect to
final focus quads were identified
• 22 sextupoles were taken out from
each of SF and SD families
• They were grouped into 4 families
• New groups allow one to change
2nd-order chromaticity while
keeping linear chromaticity
constant
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2nd-Order Chromaticity Correction
• 2nd-order chromaticity reduced from
-15000 to -3000 units
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Beam-Beam Effects – 150 GeV
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Issue
Solution
Impact on Luminosity
Schedule
Increased Proton Intensity
Transverse Dampers
30% to L0
Horizontal commissioning
in progress, vertical to
follow (this month)
Improve injection aperture
and emittance growth
Improved MI to Tevatron
transfer line match
6% to L0
Matching in progress
Improve injection aperture
and emittance growth
Turn-by-turn position
diagnostics and orbit
closure algorithm
6% to L0
Pbar system in operation
Improve injection aperture
and emittance growth
Fast injection dampers
5-10% to L0
Limited aperture and
separation at 150 GeV
Replace C0 Lambertson
magnets with larger
aperture dipoles (double the
vertical aperture)
10% to L0
Limited aperture and
separation at 150 GeV
Improved optics across A0
straight section
5-10% to L0
Time-dependent tune and
coupling drift at 150 GeV
Tune drift compensation
2-5% on integrated L
Early 2003
Next extended shutdown
Early 2003
Put into operation last week
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Beam-Beam Effects – 980 GeV
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Issue
Solution
Drifting tunes during store
On-line tune stabilization
Low lifetime – restore to
Run I values (>15 hours)
Explore larger helix
separation
Low lifetime – restore to
Run I values (>15 hours)
Optimize tunes for most
bunches
Pbar tune shift by protons
Beam-beam compensation
with electron lens
Impact on Luminosity
Schedule
4-10% in integrated
Luminosity
Long-term
10-30% in integrated
Luminosity
Long-term
up to 30% in integrated
Luminosity
Long-term
10% in integrated
Luminosity
Long-term
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Instabilities
f
Issue
Solution
Impact on Luminosity
see above
Schedule
Coherent transverse beam
blow-up at all beam
energies
Transverse dampers,
additional investigation
Damper commissioning in
progress
Coherent longitudinal
bunch by bunch beam blowup
Longitudinal bunch-bunch
dampers, additional
investigation
better understanding
Longitudinal damper in
operation at 150 and 980
GeV
Coherent ‘dancing bunches’
Observed, under study
better understanding
December 2002
Incoherent bunch length
growth
Observed, under study
better understanding
early 2003
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1986 talk by R. Johnson
2006 paper by A. Valishev
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