KEKB: Present and Future
2/25/2002
K. Oide @ Machine Advisory Committee

1. Where are we now?

2. When and How do we Upgrade?

Thank to all members of KEKB, Belle, Kurokawa san ...

by* = 7 mm
(nx,ny)=(0.52, 0.08)

LER V4
Movable masks

C-Yoke: (1) 800 m (2) 800 m

1300 m1350 mHER V4 masks

HER

LER

(nx,ny)LER=(nx,ny)=(0.52, 0.60) (0.514, 0.57)

Solenoid: 800 m

56.3 /fb

2.06 /fb/7 days
7.56 /fb/30 days

329 /pb/day

6.62 /nb/sPeak Luminosity(nx,ny)HER=(0.514, 0.59)

1850 mFast Abort Kickers

1750 mLuminosity has been more than doubled since theLast MAC:

1. Higher beam currents were made possible by• Additional solenoid windings for LER• extended from 1300 m to 1850 m• Moving-chamber damage-free masks in HER• Fast abort kickers / Recovery of a few rf cavities /New abort chambers / Better coolings /Higher positron charges from Linac, etc.

2. Optimize/maintain machine parameters:• Horizontal tunes closer to the half integer• Tune management with gated betatron tune meter• Circumference control / Skew correction at IR, etc.

Horizontal EmittanceBeam current
Number of bunches
Bunch current

HERnm

18LER

24

HER

nm

3/15/2001

LER24mA

2/24/2002
18530mA

680

1153

0.46mA0.598221223mAmmm

123mm

0.67

1333
1.09

2.4

103

2.2m

mm

2.2

2.4

121mm

Bunch spacing

103

2.7

1s *x
2.7

1

Horizontal size at IPs y*%

Bunch trains

Vertical size at IP

2.8cm

3.7

63 / 0.70%

59 / 0.70

4.4cm

6.3

61 / 0.70

ey ex

59 / 0.65

0.040 / 0.0290.074 / 0.042

0.047 / 0.043

0.069 / 0.046

Emittance ratio

b x* b y*
beam-beam parameters

xx xy

/nb/s

min.

2.90/pb

300 @ 550 mA/nb/s

168 / 970 /180 @ 700 mA
6.62/pbmin.

329 / 2060 / 7560

Beam lifetime at collision 180 @ 1200 mA 250 @ 800 mA
Luminosity (Belle CSI)
Luminosity records
per day / 7 days/ 30 days

Tune Management with the Gated Tune Meter• Off-collision• Feedback is vetoed at
the pilot bunches

Dec 2001
1153 bunches

Feb 2002
1224 bunches

Pilot bunch

More ProgressContinuous Injection• Tried a few times with an increase of integ. luminosity
by 15-20%.
• Rise of vacuum pressure in LER due to heating of NEG
by the TE mode near the movable masks.
• Some (should be minor) problems in DAQ at Belle.

2 bunch/rf pulse injection of positron• Initial success with 50% increase of the injection rate.
• Debug is necessary in the bunch current
monitor/equalizer.

Continuous Injection

Regular Injection

New Issues

1. Vacuum leak at the wiggler chambers due tosynchrotron light. (managed)
2. Vacuum leak at the abort chambers due to heating by
the wall current or hit of the aborted beam. (to be curedin March)
3. Heating of synch. light mask at IP. (to be cured in thissummer)
4. Heating of NEG cartridge by the TE mode near themovable masks. (to be cured in March)
5. Low frequency horizontal instability at HER (resistivewall?)
6. Bunch current monitor/equalizer. (to be cured inMarch)Luminosity increase in the near future

Now we guarantee 7.8 /fb/month to Belle.
After March:• Continuous injection• 2 bunch injection of positrons• 3.5 bucket spacing• Increase LER to 1.5 A, HER to 0.9 A.

After the summer shutdown in 2002:• Less than 3 bucket spacing.
• Increase HER to 1.1 A (design).
• Increase LER as long as luminosity increases.

4 bucket
3.5 bucket

4 bucket

3.5 bucket

We
are
here

SVD

9/fb/month
8/fb/month

Major Upgrade
toSuper KEKB"Super KEKB"

1035 /cm2/s peak luminosity
LER 10 A + HER 4 A (roughly)
Redesigned IR with larger crossing angle
Preserve arc lattice/magnets
Double the ring RF system
Totally new vacuum chambers in both rings
Renewed cooling/electricity facilities
Charge switch with a high-gradient linac
Positron damping ring
Separate injector for PF/PF-AR
80 - 100 MW wall-plug power
50 BY construction cost