SLAC Accelerator Department PEP-II Super-B-Factory Collider John T. Seeman Assistant Director of the...

SLAC Accelerator Department

PEP-II Super-B-Factory Collider

John T. SeemanAssistant Director of the Technical Division

Head of the Accelerator DepartmentDESY Meeting

November 9, 2004


Abstract: B Physics at a Super B Factory• Part I: The Detector and Physics Capability [David MacFarlane]• Part II: The Collider [John Seeman]

• Abstract: The present generation of B Factories at SLAC and KEK have now accumulated between them more than 0.5 ab-1 of e+e- to Upsilon(4S) events or about 500 million B-anti-B meson pairs. These samples have been used to establish CP violation in the B meson system and to study rare B decays with unprecedented sensitivity, both within the context of the Standard Model and as a window for new physics. There may even be hints for new physics in b to s penguin modes in present data, which is, in any event, an important example for the future. Building on the successful foundation of KEKB and PEP-II, including an understanding of the capabilities for both the colliders and detectors, the B Factory community is now looking at the physics case and technical requirements for extrapolating present day luminosities another factor of 20-50 at so-called Super B Factories. These talks will examine the physics case for the Super B Factory, the technical requirements and parameters for the collider, and the implications for an upgraded detector that have emerged at SLAC and KEK.


Topics

• Brief status: PEP-II and short range plans

• Super-B-Factory Collider parameters

• Super-B-Factory Plans


SLAC Beam Lines


PEP-II e+e- Collider• Use the SLAC linac as

upgraded for the SLC for the injector.

BaBar Detector

FeedbacksDiagnostics

LERRF476 MHz

HERRF476 MHz

3.1 GeV positrons x 9 GeV electronsC = 2200 m


PEP-II arc section


PEP-II Interaction Region Components near BaBar

HER

LER

Collision point

BaBar



Improvements last year

– Peak luminosity (L): 6.6 9.21033

– Number of bunches: 1050 1588 bunches • by-2 pattern (24 long mini-trains) with 2% ion gap

– Parasitic collision effects seen but small(<5% on L)– Electron Cloud (ECI) effects are small (<2% on L)– I current 1500 2450 mA (3 RF stations)– Icurrent 1050 1550 mA (8 RF stations)

y* of 12 11 mm

– All data now taken in trickle charge mode • Both beams: LER in November, HER in March


Peak luminosity of 9.21 x 1033

PEP-II RecordPeakLuminosity


Daily Integration Record with Trickle Injection

710/pb

LER I

HER I

Luminosity


Trickle injection at the B FactoriesBest shift, no trickle

PEP-II: ~5 Hz continuousKEKB: at ~5-10 min intervals

Best shift, LER only trickleNov 2003

Best shift, double trickleMar 2004

PEP-II LumiHER currentLER current


PEP-II Performance Measure: Peak Luminosity



•

Total >240 fb-1!


Overall Parameters and Goals

Parameter Units DesignBest in collision

Future 2007 goal

I+ mA 2140 2450 4500

I- mA 750 1550 2200

Number bunches

1658 1588 1715

y* cm 15-20 11 8

y 0.03 0.045, 0.07 0.055-0.08

Luminosity x1033 3.0 9.2 24

Integrated lumi / day

pb-1 130 710 1800

Over five times design!Over three times design

Twice design


New transverse kicker electrodes


New Longitudinal Feedback Kicker Assembly


New LER Synchrotron Light Monitor

Improved resolution

Single bunch capabilities


Near Term PEP-II Goals

• 530 fb-1 total integrated by Fall 2006.

• About 1.5 to 1.8 ab-1 integrated by Fall 2010.


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

• 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.

• The long range time goal is to have a new upgraded accelerator running in 2011 or 2012.


Achieving Super B Luminosities bnI Higher Currents:

o More rf power, cooling, injectoro More HOM heating (more bunches)o Beam instabilitieso Electron clouds, fast ions

* y Smaller y*:o Smaller physical/dynamic apertureo Shorter lifetime, more background

Shorter z:

o More HOM heatingo Coherent synchrotron radiationo Shorter lifetime, more background

y Higher tune shifts:

o Head-on collisions replaced by angled crossing

o Degrades maximum tune shift unless crabbing cavities used

34*

2.17 10 y b

y

n EIL


Parameters for High-Luminosity B Factory

Luminosity (x1034)

0.9 2.4 15 25 70 Units

e+ 3.1 3.1 3.1 3.5 8.0 GeV

e- 9.0 9.0 9.0 8.0 3.5 GeV

I+ 2.45 4.5 8.7 11.0 6.8 A

I- 1.55 2.2 3.0 4.8 15.5 A

(y*) 11 8 3.6 3.0 1.5 mm

(x*) 30 30 30 25 15 cm

Bunch length 10 7.5 4 3.4 1.7 mm

# bunches 1588 1700 1700 3450 6900

Crossing angle 0 0 0 11 15 mrad

Tune shifts (x/y)

4.5/7 8/8 11/11 11/11 11/11 x100

rf frequency 476 476 476 476 952 MHz

Site power 40 40 75 85 100 MW

J.Seeman Jul 04 Jul 07 LERvacuum

+IR +HER vacuum, 952MHz rf


Lessons learned from PEP-II & KEKB

• Asymmetric beam energies work well.

• Energy transparency conditions are relatively weak.

• Asymmetric interaction regions can be operated.

• IR backgrounds can be handled though are not easy.

• High current RF can be operated (1 A x 2 A).

• Bunch-by-bunch feedbacks work (4 ns spacing).

• Beam-beam tune shifts reach 0.08 (v) to 0.10 (h).

• Injection rates good; continuous injection feasible.

• Electron Cloud Instability (ECI) ameliorated for now!


New techniques for Super B-Factory

• Beam lifetimes will be low continuous injection.

• Very low y* (6 to 10 mm 1.5 to 3 mm).

• Higher beam-beam parameters (trade beam-beam lifetimes for tune shifts)

• Higher beam currents (x 5 or so).

• Higher frequency RF (more bunches).

• Bunch-by-bunch feedbacks at the 1 ns scale.

• Very short bunch lengths (<2 mm).

• High power vacuum chambers with antechambers and improved or no bellows.

• Reduce energy asymmetry to save wall power.


LER aluminum vacuum system: limit at 4.5A

Total LER SR power

= 2 MW

High powerphoton stops

AntechambersReduce Electron-Cloud-Instability

4.5 A at 3.1 GeV

Photon Stop limits


Vacuum system for Super B Factory (S-KEKB)

• Antechamber and solenoid coils in both rings.

• Absorb intense synchrotron radiation.

• Reduce effects of electron clouds.

Circular-chamber

Ante-chamber

Ante-chamberwith solenoid field

Build-up ofelectron clouds


Electron Cloud Instability & multipacting


Windings added for ECI reduction


PEP-II HER RF cavities


HOM calculations: 476 MHz cavity

476 MHz cavity with a larger beam

opening

S.Novokhotski

Rbeam = 95.25 mmTotal loss = 0.538 V/pC

Loss integral above cutoff = 0.397 V/pC

HOM Power = 203 kW @ 15.5A


HOM calculations: 952 MHz cavity

952 MHz cavity with a larger beam

opening

S.Novokhotski

Rbeam = 47.6 mmTotal loss = 0.748 V/pC

Loss integral above cutoff = 0.472 V/pC

HOM Power = 121 kW @ 15.5A


PEP-II 1036 B-Factory +/- 12 mrad xing angle Q2 septum at 2.5 m

30

20

10

0

-10

-20

-30

cm

-7.5 -5 -2.5 0 2.5 5 7.5m 31-JAN-2002

M. Sullivan

Q1

Q1Q1

Q1

Q2

Q4

Q5Q2

Q4Q5 e+

e-

IR concept for a Super B-Factory

M.Sullivan

±12 mr crossing angle

o No background calculations yet

Can luminosity component be reduced?


New IR magnet design (Parker)


New IR magnet designQuadrupole, anti-

solenoid, skew quadrupole,

dipole and trims located in one

magnet.

All coils numerically wound on a bobbin.


87.57

6.56

5.5

4

3.532.5

21.51

0.5

4.55

HER Radiative Bhabhas

-7.5 -5 -2.5 0 2.5 5 7.5

0

10

20

30

-10

-20

-30

m

cm

M. SullivanFeb. 8, 2004API88k3_R5_RADBHA_TOT_7_5M

3.1 G

eV

3.1 G

eV

9 GeV

9 GeV

Luminosity-dependent backgrounds

o SR in bend & quadrupole magnets

o Current dependent terms due to residual vacuum

o Bhabha scattering at IP

PEP-II Head-On IR Layout


Activities towards luminosity upgrade

crossing angle 22 mrad

Head-on(crab)

◊

◊◊

◊◊

y

(Strong-weak simulation)

(Strong-strong simulation)

Crab crossing may boost the beam-beam parameter up to 0.2!

Superconducting crab cavities are under development, will be installed in KEKB in 2006.

I.R. 20

I.R. 90

I.D. 188

I.D. 120

I.D. 30

I.D. 240

Input Coupler

Monitor Port

I.R.241.5

483

866Coaxial Coupler

scale (cm)

0 50 100 150

K. Ohmi

K. Hosoyama, et al


Power scaling equations• Synch rad ~ I E4/• Resistive wall ~

I2total/r1/frf/z

3/2

• Cavity HOM ~ I2

total/frf/z1/2

• Cavity wall power = 50 kW

• Klystron gives 0.5 MW to each cavity

• Magnet power ~ gap ~ r1


Site power limits

476 MHz

952 MHz

(Linac, PEP-II magnets and campus power = 40 MW)

1.5x10342.5x1034 7x1034


Recommended scenario: 7 x 1035

• Replace present RF with 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.• 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.)

• Push y* to 1.5 mm: need new IR (SC quadrupoles) with

15 mrad crossing angle and crab cavities


Possible Timeline for Super B Program

LOI

Construction of upgrades to L = 5-7x1035

-1~10 ab / yrLdt

Super-B Program

CDR Installation

R&D, Design, Proposals and

Approvals

P5

Construction

2001 2003 2010200820062005

Planned PEP-II Program

-1140 f bLdt -1500 f bLdt -1~1 2 abLdt

(June 30, 2003) (End 2006) (PEP-II ultimate)

Commission

2012

Super B Operation

2011


Conclusions

• PEP-II has reached a luminosity of 9.21033/cm2/s in May 2004.

• PEP-II has delivered 710 pb-1 in one day and over 256 fb-1 since May 1999.

• Trickle injection is used in both rings all of the time.

• Planned upgrades toward 2.41034 are on track.

• We will finalize technical specifications over the next few months for the 2005 and 2006 downs.

• The parameters of a Super-B-Factory were studied with RF frequencies of 476 MHz and 952 MHz.

• At the present, for 90 to 120 MW of total power, linac and campus included, 476 MHz provides a luminosity of about 2 to 4 x 1035 and 952 MHz provides about 0.7 to 1.0 x 1036. Vertical beam-beam parameters are 0.107.

• Studies are continuing with a technical document coming about January.


PEP-II upgrades schemesLuminosity (x 1035)

1.5 2.5 7 57

RF frequency (MHz)

476 476 952 476952

Site power (MW)

75 85 100 70100

Crossing angle No Yes Yes Yes

Crab cavities No Yes Yes Yes

Replace LER Yes Yes Yes Yes

Replace HER No Yes Yes Yes

Upgradeable NoYes

(to 952MHz)Yes Yes

Detector requirements depend on projecting backgrounds for luminosities that are >20 times

larger than at present

Recommended




Important Factors in Upgrade Direction• Project is “tunable”

– Can react to physics developments

– Can react to changing geopolitical situation

• Project anti-commutes with linear collider

• Will emerge from BABAR and Belle, but could be attractive to wider community in context of other opportunities

– As we learn more about machine and detector requirements and design, can fine tune goals and plans within this framework

• Project has headroom

– Major upgrades to detector and machine, but none contingent upon completing fundamental R&D

– Headroom for detector up to 5 x 1035; with thin pixels beyond

– Headroom for machine up to 8.5 x 1035; requires additional rf, which can be staged into machine over time


Timeline for a Super-B-Factory at PEP-II• The key is the approval date by DOE’s P5 and to enter the DOE

Budget cycle for FY2008 which is about July of 2006!• Thus, the plan as needed:

• SBF LOI to the SLAC EPAC/SPC in late 2004.• SBF LOI to the NAS in January 2004.• SBF CDR to SLAC EPAC/SPC in Fall 2005.• CDR endorsed by SLAC EPAC/SPC in January 2006.• CDR endorsed by NAS in Spring 2006.• P5 approves SBF proposal in June 2006.• DOE enters SBF into FY2008 Budget in Fall 2006.• SBF receives construction funds about January 2008.• Construct SBF parts for 1.5 years while running present PEP-II.• Run PEP-II to July of FY2009.• Install for two years.• Start SBF data taking in July 2011with 3x1035 collider.• Upgrade to 7 x 1035 in two years (by fall 2013).


Super KEKB machine parameters

Beam-beam parameter is obtained from simulations: strong-strong (weak-strong)


Coherent synchrotron radiation

• Numerical simulations with mesh (T.Agoh and K.Yokoya)

– Analytic formula is not reliable due to strong shielding.

• Loss factor estimation :– No synchrotron oscillation and no interference between bends.– 1 V/pC for 6 mm bunch length (LER)– 10 V/pC for 3 mm bunch length (LER) ⇔ 30~40 V/pC in the ring

Energy change as a function of z/zKEKB LER/ 2.6A (5120)

c h3 2.5 mm

bunch length dependence

chamber height dependence

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