Super-B-Factory Collider Work at SLAC U. Wienands, for John T. - - PowerPoint PPT Presentation

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Super-B-Factory Collider Work at SLAC

• U. Wienands, for John T. Seeman

SLAC Hawaii Super-B-Factory Meeting April 20, 2005

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The PEP-II Team

• August 2004

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Topics

• Brief PEP-II status and plans
• Super-B-Factory Collider parameter studies
• Conclusions

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SLAC Beam Lines

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PEP-II Interaction Region Components near BaBar

HER LER Collision point BaBar

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PEP-II arc section

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PEP-II HER RF cavities

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• Total >240 fb-1!

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PEP-II Performance Measure: Peak Luminosity

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Trickle injection at the B Factories

Best shift, no trickle

PEP-II: ~5 Hz continuous KEKB: at ~5-10 min intervals

Best shift, LER only trickle

Nov 2003

Best shift, double trickle

Mar 2004

PEP-II Lumi HER current LER current

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Overall Parameters and Goals

0.055-0.08 0.045, 0.07 0.03 ξy 1800 710 130 pb-1 Integrated lumi / day 23 9.2 3.0 x1033 Luminosity 8.5 11 15-20 mm βy* 1715 1588 1658 Number bunches 2200 1550 750 mA I- 4500 2450 2140 mA I+ Future 2007 goal Best in collision Design Units Parameter

Over five times design! Over three times design Twice design

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PEP-II Run Schedule

• SLAC was shut down until early April due to

electrical accident & ensuing safety reviews

• PEP-II Run 5 started April 15, 2005.
• Will collide steadily from April 2005 through

July 2006 with a one month break in October 2005.

• Down in 2006 August through November for

BaBar and PEP-II upgrade work.

• Three month down in Summer-Fall 2007 for

LCLS work.

• Collide through September 2008.

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Integrated Luminosity Goal

PEP II Integrated Luminosity (1/fb)

0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 A p r i l A u g

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D e c e m b e r A p r i l A u g

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D e c e m b e r A p r i l A u g

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D e c e m b e r A p r i l A u g

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Month ∫Ldt Series1

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Upgrades for Run 5

• One additional rf station for each HER and

LER

– HER beam current >1.8 A, LER, 3.6 A

• Removed NEGs in the LER upstream of

BaBar

– rf power leaking through screen caused severe heating. – more to be replaced in October

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17 Existing 3082 chamber

BPM BPM Chamber support Cooling bar NEG plenum NEG heater Quad extrusion

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Chamber shown inverted and plenum not shown for clarity SiC HOM absorber

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PEP-II/BaBar Roadmap: Super B-Factory Study May 2004

• The Roadmap Committee

is studying the long range future of PEP-II and BaBar with a possible large upgrade at the end of the decade.

• A Super-PEP-II could

produce 10 ab-1 per year with a peak luminosity of 7 x 1035/cm2/s.

• Accelerator parameter

goals have been set and work towards a solid design has started.

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Recommended scenario: 7 x 1035

• Replace present RF with SC 952 MHz frequency over

period of time.

• Use 8 x 3.5 GeV with up to 15.5 A x 6.8 A.
• New LER and HER vacuum chambers with antechambers

for higher power (x 4).

• Replace LER magnets to soften radiation and resistive wall

losses; rework HER magnets as well.

• Push βy

* to 1.7 mm: need new IR (SC quadrupoles) with

15 mrad crossing angle and crab cavities with bunch lengths of 1.8 mm.

• New bunch-by-bunch feedback for 6900 bunches (every

bucket) at 1 nsec spacing. (Presently designing feedback system being 0.6-0.8 nsec spacing.)

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SBF Overall Parameters and Goals

0.11 0.11 0.065 ξy 75 50 1.8 fb-1/day Integrated lumi / day 100 70 2.3 x1034 Luminosity 1.7 1.8 8.5 mm βy* 6900 6900 1715 Number bunches 23.0 15.5 2.2 A I- 10.0 6.8 4.5 A I+ 1E36 SBF 7E35 SBF Best of PEP-II Units Parameter

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Achieving Super B Luminosities

bnI

Higher Currents:

• More rf power, cooling, injector
• More HOM heating (more bunches)
• Beam instabilities
• Electron clouds, fast ions

Smaller βy*:

• Smaller physical/dynamic aperture
• Shorter lifetime, more background

Shorter σz:

• More HOM heating
• Coherent synchrotron radiation
• Shorter lifetime, more background

Higher tune shifts:

• Head-on collisions replaced by angled crossing
• Degrades maximum tune shift unless crabbing

cavities used

Ib ßy* ξy

L ∝ nξy EIb βy

*

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Crossing-Angle Experiment

Normalized Lsp vs. e

• angle

0.75 0.80 0.85 0.90 0.95 1.00 1.05

• 1000
• 500

500 1000

XP[e-] (murad) Lsp / Lsp(XP=0)

by-4, msrd by-4, fit

• sp. by-2, msrd
• sp. by-2, fit
• W. Kozanecki

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Initial IR Design for a Super B-Factory

M.Sullivan ±14 mr crossing angle

• First look at SR

backgrounds Try to limit luminosity component by minimizing bends

e36 B-factory IR +/- 14 mrads RevD

10 20 30

• 10
• 20
• 30

2.5 5 7.5

• 2.5
• 5
• 7.5

m cm

• M. Sullivan Apr 16, 2005

200 kW 40 kW 13 kW 83 kW 3 kW 11 kW

QF5 QD4 QF2 QD1 QD1 QF2 QD4 QF5 LER HER

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New IR magnet design (Parker)

• B. Parker

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New IR magnet design

Quadrupole, anti- solenoid, skew quadrupole, dipole and trims located in one magnet. All coils numerically wound on a bobbin.

• B. Parker

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New Rf system, s/c Technology

• 1…2 MV/cavity, 500 kW/coupler
• R/Q of 12Ω aimed at for beam stability
• 952 MHz => Potential for 6900 bunches
• up to 40 MW power to the beam (LER, 23 A)
• Support bunches as short as 1.8 mm

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New cavity design for a SBF (SC, R/Q≈5Ω)

• A. Novokhatski

Accelerating field Distance (cm)

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New Magnet Systems/Lattices

– Low momentum compaction

• short bunches without excessive rf voltage
• increase stability against longitudinal multibunch

instability

• maintain reasonable synchrotron tune

– (simulations predict high νs to be detrimental to luminosity)

– Larger-aperture magnets than present PEP-II

• allows increase of beam-pipe radius, lower res. wall loss
• becoming an issue at SBF beam current & bunch length

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Resistive-Wall Wake (bunch lengthening)

Power SS: 45 MW Al: 9 MW Cu: 7 MW SR: 18 MW

• A. Novokhatski

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New bellows design with HOM absorber

• Kurita

Novokhatski Weathersby

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LER ring (no IR yet) Small positive momentum compaction, using present LER dipoles & quads (16 families), 3 sextupole families

• M. Biagini

One sextant

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Electron Cloud Instability

• PEP-II uses solenoidal fields and gaps in the

fill to mitigate ECI

– Experiment at end of Run 4: fill all gaps

• Luminosity scaled with bunch#
• =>probably don’t need the gap at present beam

current (2.6 A).

• At Super-B beam currents, these may not be

sufficient

– Investigate means to further reduce secondary emission in the vacuum system

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Windings added for ECI reduction

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Low-Secondary Yield Test Pipe

• M. Pivi

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Wall-Plug Power

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Conclusions

• PEP-II is again producing data.
• Present B-Factories will provide solid data

for four or more years. PEP-II is heading towards 2.3 x 1034 in three years.

• Super-B-Factory designs are stabilizing.
• Designs of a Super-B-Factory should allow

for upgrade paths to allow the accelerator to remain competitive over its lifetime.

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Important Factors in Upgrade Direction

• Accelerator project should have headroom:

– Design for 7 x 1035 – Headroom for machine up to 1 x 1036; requires additional RF, which can be staged into machine

• ver time.
• Accelerator built in the timely manner with a rapid turn
• n.