Machine performancesince Feb. 2002
Y. Ohnishi
2/10/2003
The 8th Machine Advisory Committee

1.
2.
3.
4.

Present status
Progress since the last MAC
Operation stability
Short/long term plans
12

Date

10/29/2002

2/21/2002

Ring

LER

HER

LER

HER

Horizontal Emittance

1824

18

24nm

Beam current

1454

949

1333

822mA

0.67mA

Number of bunches

1184

Bunch current

1.23

1223
0.80

1.09

Bunch spacing

2.4

2.4

Bunch trains

11m

Horizontal size at IP σ*x103121103

121µm

σ*y

2.9

2.9

2.7

2.7µm

7.5

5.0

6.34.4%β*x/β*y59/0.62

61/0.759/0.65

61/0.70cm

Beam-beam parametersξx/ξy0.090/0.053

0.078/0.045

0.069/0.046

0.074/0.042

Beam lifetime at collision

68 @1454 mA 197@949 mA

180@1200 mA

250@800 mA

Vertical size at IP

Emittance ratio εy/εxmin

Luminosity (Belle CsI)

8.26

6.62/nb/s

Luminosity records
per day/7 days/30 days

434/2579/8617

329/2060/7560/pb

3

Performance• Luminosity increases by 25 % since the lastMAC.
–c.f. “Luminosity has been more than doubled since the last MAC.”– From K.Oide / MAC 2002

• Luminosity has been achieved more than
80 % of the design luminosity.
– Lpeak = 8.26x1033 /cm2/s• Total int. luminosity reached 100 /fb.
– “KEKB Project Leader predicted that the conservative lower limit for the monthly int.
luminosity would increase to 9 /fb; the Committee agree that….”– From recommendations / MAC 2002

– Monthly record = 8.26 /fb/monthÐ Yes, we can guarantee more than 9 /fb/month toBelle.

4Daily Luminosity in 2002
More than 400 /pb/day !
Monthly record
Summer
8.26 /fb/month

shutdown

434 /pb/day

IP chamber
broken5

Specific luminosity• Specific luminosity is much improved.
• Better working point is found.
HER
Hor. Tune

LER
10/29/2002

2/21/2002
2/21/2002

10/29/2002

Ib(LER) x Ib(HER) (mAxmA)

Ver. tune

Specific luminosity ( 1030 /cm2/s)

Pilot bunch tunes (off-collision)

6

Progress• LER current increases to 1.5 A and HER to 1 A.
– RF cavities are fully installed in LER. (20 ARES)– HER (8 SCC + 10 (design: 12) ARES)– Great success to operate SCC at 1 A !
– Additional solenoids for LER: 1850 m to 2275 m.

• 2-bunch injection of positrons is applied at standardoperation.
– Integrated luminosity increases with short inj. time (e+).
– Bunch current monitor/equalizer is cured.

• Heating of synch. light mask at IP is cured by making
cooling power strong.
• HOM (TE mode) heating of NEG cartridge near the
movable masks is cured by RF shield.
7

LER beam size blow-up• Photoelectron cloud effect• Solenoid windings (total = 2275 m) > 90%• Positron beam blow-up was not observed
up to 1.6 A (January 2003).
– Single train

29/Jan/03
5– #bunch = 1224

Vertical beam size@I.P. (micron)– 4 bucket spacing

4/320/4
4

Vertical beam size at IP
321005001000
Beam current (mA)

1500

2000

8Typical injection (24 hours)
Red bar for LER and blue bar for HER.
Bottom end shows average and top end shows max. value.

2-bunch injection in LER

Charges(nC)
Rates(mA/s)
Efficiency(%)

Positron injection rates are improved from
1.2 mA/s to 2.4 mA/s with 2-bunch injection.

9Fill patterns
Feb 2002
1224 bunches
4-bucket spacing

5-bucket spacingat every 11x4 bucket

Oct 2002
1184 bunches
Pseudo 4-bucket spacingfor 2-bunch positron
injection
Pilot bunch10

RF shield for NEG
HOM comes from Mask.
■ Pressure decreases by 25 %.
■ Temperature is 30 oC lower.
■ Allows continuous injection
NEG-port shield■* NEG: Non Evaporable Getter (SAES)

NEG port11

Progress (cont’d)• KEKB is ready for continuous injection.
– HOM heating at NEG is cured by RF shields.
– Waiting for Belle trigger system upgrade.

• Abort chamber was redesigned andinstalled.
– Vacuum leak was sometimes occurred at abortchamber. (Aborted beam hits the chamber.)– New abort chamber has larger aperture .

12

Best luminosity run of the day
8.26 x1033 /cm2/s
434 /pb/day

13

Operation stability
1.
2.

Optics measurement and correction
Betatron tune management•

3.

gated tune meter/programmable tune changer

Collision feedback
iBump feedback (collision orbit optimization)
beam size / lifetime feedback for horizontal offset at IP(optimization by experiences)
iSize feedback (beam size optimization)

4.

Luminosity tuning : Establishment of knobs
Adiabatic tuning of waist (s*) / IP dispersion (ηy*, ηy’*) / IP
tilt (r1, r2, r3, r4)

5.
6.

Circumference adjustments with COD correction
Injector linac : beam quality control•

optics measurement using wire scanner / energy
feedback / orbit feedback, etc.

14

Stability of specific luminosity• Luminosity sometimes
degrades gradually.①• Luminosity comes back withsetting steering, gold orbit,
optics when luminosity wasgood.②• Luminosity also comes backwith adiabatic tuning(waist,IP disp., IP tilt, tunes) after
optics correction.③• NEG activation• Magnet standardization• Optics correction
maintenance• waistReset• IP dispersion• steering• IP tilt• orbitTune• optics
adjustment

②
①

①

③
stableSummary of 1 week15

Optics measurement and correction
beta function

dispersion

Interactive procedure ofmeasurement + analysis + correction
Knobs:■ Local bumps at sextupoles■ Fudge factors for quads/skews
Works very well !

XY-coupling

16

Optimization of betatron tunes
Dif. btw refand meas

Ref dataRef lineMeas.

injection1.

collision

Pilot bunch is monitored bygated tune meter.
■2.
3.

Off-collision / No BxB FB

Tune patterns as a function ofbeam current
Horizontal tunes close to thehalf integer

Good control/manage of tunes ! 17

Circumference adjustment
Circumferences are adjusted by RF frequency with looking at HER orbit.
LER has an independent knob to adjust circumference with “Chicane”.
Orbit correction (CCC) applies circumference correction simultaneously.
knob∆C=C∆C∆f=−Cf∆p=pmeasurementxRF frequencyAtmosphericpressure

Bending angle of the chicane(LER circumference adjustment
w/o RF frequency)
Extension ofthe circumference

Extension about
300µm (-50 Hz).
≈60µm

Typhoon #21 (970 hPa)
(9 p.m. October 1, 2002)

ShrinkThis behavior is consistent with tidal effect.
We observe tidal effect by ground motion ??
18

Path of Typhoon #21 (October, 2002)

KEK,Tsukuba

19

Circumference drift (long term)
K. OideAir temperature (day/night)
2fMoon=1.932/day
MMoon/MSun/(RMoon/RSun)3=2.27

20

Present status• Physics run starts in January 2003.
– Total beam current is now limited to 2.2 A (from Belle).
– Condition is good. More than 300 /pb/day– We plan to increase currents gradually withchecking I.P chamber.

To Do List
• Replacement of SVD/IP chamber during summer
shutdown.
• Continuous injection• 3.5 bucket spacing or less than 3 bucket spacing• Increase HER to 1.1 A (design).
• Increase LER as long as luminosity increases.
21

Long term plan
• Test of ante-chamber/new bellows• Test of C-band accelerating structure
for e+ to energy upgrade• Test of 3.5 GeV e- in LER(Need change polarity)• Test of crab crossing in 2005
– 1 cavity at Nikko section in HER22

Next milestone• Design luminosity :1034 /cm2/s• 100 /fb/year

Long summer shutdown(replacement of SVD/IP chamber)

Next MAC~170 /fb
We are here23