PEP-II Status

Yunhai Cai
March 22, 2006
KEK
KEKB MAC Meeting

Parameters

Description(10/4/05)

LER(e+)

HER(e-)

E(Gev)

beam energy

3.1

9.0

Nbbunch population

7.783x1010

4.585x1010(1.70 mA)

(1.00 mA)

βx*(cm)beta x at the IP

40

35.0

βy*(cm)beta y at the IP

1.08

1.08

εx(nm-rad)emittance x

33.0

55.0

εy(nm-rad)emittance y

1.50

1.30

νxx tune

0.52500.5160νyy tune

0.57900.6223νssynchrotron tune

0.032

0.049

σz(cm)

bunch length

1.25

1.15

σpenergy spread

6.5x10-4

6.1x10-4

τt(turn)transverse damping time

9800

5030

τl(turn)longitudinal damping time

4800

2573

Peak Luminosity October 10, 2005
(I+=2940mA, I-=1733mA, nb=1732)

beam-beam
parameters:ξ x+ = 0.098
ξ y+ = 0.070
ξ x− = 0.086
ξ y− = 0.037
Data taken in the history buffer for a 24 hours period.
The simulation used an approximately fixed current ratio.

Specific Luminosity October 10, 2005
(I+=2940mA, I-=1733mA, nb=1732)

Data taken in the history buffer for a 24 hours period.
The simulation used an approximately fixed current ratio.

Projected Luminosity: 2E34 cm-2s-1
in 2007• HER 900 lattices to lower momentum
compaction factor and beam emittance• Low-beta optics near βy* = 8 mm
• Use wiggler in the LER as a damping wiggler• More RF stations in the HER, LER?
• More currents 4000/2200 mA in the machine• Shorten the bunch length to 9 mm
• Adequate dynamic aperture to ensure a good
beam-beam lifetime

Parameters

Description(2007)

LER(e+)

HER(e-)

E(Gev)

beam energy

3.1

9.0Nbbunch population

1.066x1011

5.865x1010(2.325 mA)(1.279 mA)

βx*(cm)beta x at the IP

3030

βy*(cm)beta y at the IP

0.85

0.80

εx(nm-rad)emittance x

30.0

40.0

εy(nm-rad)emittance y

1.20

1.80

νxx tune

0.51620.5203

νyy tune

0.55090.6103νssynchrotron tune

0.03810.049

σz(cm)

bunch length

0.95

0.90

σp

energy spread

6.5x10-4

6.1x10-4

τt(turn)transverse damping time

8424

5030

τl(turn)longitudinal damping time

4128

2573

Projected Luminosity: 2E34 cm-2s-1

Recent Activities• PEP-II has been limited by the vacuum bursts
near the interaction region since the beginningof this year.
• The stable beam currents below
1550mA/1250mA. The luminosity is limited at
half of its maximum reached value.
• The exact cause of the problem is unknown. The
most popular suspect is the tiles used as HOM
absorbers. The replacement of those vacuum
chambers are underway.
• Since the beam currents, we are trying to makeprogress to improve specific luminosity.

Four Orthogonal Orbits Extracted
Using FFT (Yiton Yan)

R-Matrix Elements and Orbits
ab12a b1 2a b2 1a b3 4a b4 3

ab
14a b1 2a b2 1a b3 4a b4 3

ab32

a1b2a b2 1

a3b4a b4 3

ab34

a1b2a b2 1a3b4a b4 3

R = ( x x − x x ) / Q12 + ( x x − x x ) / Q34
R = ( y x − y x ) / Q12 + ( y x − y x ) / Q34
R = ( x y − x y ) / Q12 + ( x y − x y ) / Q34
R = ( y y − y y ) / Q12 + ( y y − y y ) / Q34
where a and b are indices for the locations of the beam
position monitors, Q12 and Q34 are invariant amplitude ofthe orbits.
J. Irwin and Y.T. Yan, Proc. The 7th EPAC p151, (2000)

Beta Beating Correction in the HER
Feb. 16, 2006
• Reduce the beta beating in the HER from 250%
to 15%– Predicted the correction with an accurate model using
MIA and LEGO
– Tweaked single quadrupole: QF5L by +0.225%– Moved closer to half integer νx=0.516• Reduced coupling in the HER within several
hours, compared with several days, using MIA– Reached specific luminosity of 4.0– Tweak of skew quadrupoles for additional 15% gainPrediction from MIA/LEGO Model

Horizontal tune is fixed with tune trombones back to 0.516.

Comparison of β Functions

Actual tweak of QF5L was twice larger than predicted.

Chromatic Optics for the HER
Feb. 16, 2006

• Measured chromatic optics and dynamic
aperture in HER– Excellent agreement between measurements andLEGO model in the chromatic optics– Improvement of understanding of nonlinear dynamics
including sextupoles

J. Yocky, P. Raimondi

Built Beam-Based Online Model for HER Within Four Hours(March 7, 2006, Mark Woodley and Yiton Yan)νxx-oscillation

νydispersions

Steering in LER
March 9, 2006

J. Turner, J. Yocky, F.J. Decker, please note that the scaled was reduced
by a factor of two.

Beta Beating and Coupling
Correction After the Steeringβxβx

coupling

coupling

BeforeAfterSummary of Achievements•••••

Built fast and accurate online model in several hours and the modelis used in the control room
Developed and tested correction schemes to correct beta beatingand coupling in arcs
Reduce the amplitude of orbit by at least a factor of two in the LER
Reduced the beta beating in both machine below to 20%
Developed a systematic and orthogonal procedure to correct optics
after a major change of lattice– IR match using MIA– Arcs correction using MIA->LEGO• Beta beating• Dispersions• Coupling••

Nearly all milestones set by the end of March were reached
Most important, we worked at a term for a common goalBeam-Beam Scan After the Steering,
Mike Sullivan, March 11, 2006

Desgin:s_min = 2.5 umtheta = 0

The best specific luminosity is 5.4x1030 cm-2s-1mA-2. Σy is 6.45 um.

Vertical Beam Size at SXM
MD started

Vertical Dispersions in the LER

We need to reduce the vertical dispersion as soon as possible.

Vertical Anti-Symmetric Bumps
20% of solution• Bumps were not quite
closed• Updated MIA online
model could help
• Vertical dispersions inMIA and LEGO did notagreed well enough• LEGO needs directaccess to the dispersion
measurement