KEKB Status
MAC 2010 Feb. 15
Y. Funakoshi

tuning withskew-sextupoles

2Se+/e- simultaneous
injection

off-resonance
4S – 60MeVKEKB was operated at Y(5S), Y(2S) and off-resonance(4S-60MeV).

KEKB/Belle total integrated
luminosity surpassed 1000 fb-1 !!!

skew-sextupoles

Machine parameters
DateCurrent

Nov.15 2006
before crab

Jun. 17 2009
with crab

LER

HER

LER

HER

LER

HER

1.65

1.33

1.60

0.933

1.64

1.19

A

0.750

mA

Bunches
Bunch current

May 19 2008
with crab (Last MAC)

1389
1.19

spacing

1584
0.961.01

2.10

1584
0.590

1.03

1.84

1.84

mA

emittance εx

18

2415

24

18

24

nm

βx*

59

56

90

90

120

120cm

βy*

6.5

5.9

5.9

5.9

5.9

5.9

mm

σx @IP103

107116

147

147

170µm

σy @IP

1.8

1.8

1.1

1.1

0.94

0.94

µm

νx

45.50543.53445.50544.50945.50644.511

νy44.50941.56543.56741.59643.56141.585

νs-0.0246-0.0226-0.0240-0.0204-0.0246-0.0209

beam-beam ξx

0.117

0.070

0.099

0.119

0.127

0.102

beam-beam ξy

0.108

0.058

0.101

0.096

0.129

0.090

Luminosity

17.6

16.8

21.08

1033cm-2s-1

KEKB operation in FY2009• The machine 9me was rather limited.
• Outcomes– The total integrated luminosity accumulated byBelle detector reached 1000 C‐1 on Nov. 29th .
– We have con9nued eﬀorts to increase theluminosity with crab crossing.
• The peak luminosity exceeded 2 x 1034 cm‐2 s‐1 by using
skew‐sextupole magnets.
• e+/e‐ simultaneous injec9on was realized.

– We conducted many machine studies for KEKB
and SuperKEKB.

What is the origin of steep slope ofspecific luminosity?

xx• Short beam lifetime– Horizontal offset at IP• Beam current dependent emittance growth in a single
beam mode?
• Machine errors– Usual knob tuning is not enough to compensate the machineerrors?
• Too many knobs?

– Side effects of large knobs?

• Beam-beam simulation misses something?

xx– Cross-check the beam-beam simulation code
– Wakefield effect + beam-beam?
– Off-momentum optics play some role to decrease theluminosity?
Slide shown in the last MAC on Feb.9th 2009 by Funakoshi

Chromaticity of x-y coupling at IP
LER skew-sextupoles (4 pairs)
HER skew-sextupoles (10 pairs)

••

•

•

Ohmi et al. showed that thechroma9city of x‐y coupling parameters(R‐parameters) at IP could degrade theluminosity, if the residual values, which
depend on machine errors, are large.
To control the chroma9city, skew
sextupole magnets, 10 pairs for HER and4 pairs for LER, were installed during
winter shutdown 2009.
It turned out that the skew sextuples
are very eﬀec9ve to increase theluminosity at KEKB. The knobs to control
the chroma9city of the x‐y coupling
parameters at IP were introduced forbeam opera9on on May 2 2009.
The gain of the luminosity by thesemagnets is 15~17%.

D. Zhou, K. Ohmi, Y. Seimiya,
Horizontal size

Vertical size
Luminosity

*
∂r2N
/∂δ

*
∂r1N
/∂δ

€

€

*
∂r3N
/∂δ

€

*
∂r4N
/∂δ

€

 r*1N * r3N * * *r2*N   R1 β x / β y=r4*N   R *3 β x*β y*
β y* / β x* R *2 / β x*β y*R *4Definition of x-y coupling
parameters (SAD notation)u pu =Tv 
pv 

x px y py  µIT (s) =  Rt
SR S
 =
µ I 
µ0−R40µ

R3R1R2µR3R40R2 
−R1 0 µ 

 0 1 2S=,µ+ det R = 1
 −1 0 
Normal (decoupled)
coordinate
Usual coordinate

Measurement on chromaticity of x-y coupling at IP (HER)
blue: without skew-sextuples
red: with skew-sextuples(after luminosity tuning)

Y. Ohnishi

Examples of scan of chromatic
x-y coupling at IP

Acer chroma9c
coupling tuning

Luminosity gain is larger
than the geometrical loss
Before chroma9c
coupling tuning

Specific luminosity with fewer numberof bunches (200 bunches/beam)

Specific luminosity with fewer numberof bunches (200 bunches/beam)
30

Crab-off
Skew-SX ON and OFF

simulation (βx = 1.5 m)

simulation (βx* = 1.2 m)
20

30-2-1-2cm s mA ]25

[10Specific Luminosity / bunch

*

1510*

black：200bunches、w/ skew-sx crab on（June 2009）β =1.2m

50*

x

red：200bunches、w/ skew-sx crab on（May 2009）β =1.5mx*
green：200bunches、w/ skew-sx crab off（June 2009）β = 1.2mx*
blue：200bunches、w/o skew-sx crab off（Nov. 2008）β = 1.5m

00.2

0.4

0.6

0.8

11.2

1.4Ibunch(e+) x Ibunch(e-) [mA2]1.6xe+/e- simultaneous injection
(fast beam mode switching)• e+/e‐/PF(e‐) simultaneous injec9on was ﬁnally realized inApril 2009 !!!.
• e+/e‐/PF(e‐) simultaneous injec9on (Furukawa’s talk)– Switch beam mode fast (in principle pulse‐to‐pulse for 50Hz linacpulses)– Magnet segngs in the linac are unchanged among the modes. We usesome pulse steering/bending magnets.
– Many 9ming signals and klystron phases are switched pulse‐to‐pulse.

• Beneﬁts of the simultaneous injec9on– The beam condi9on became more stable.
– Much faster beam tuning became possible.
– The luminosity decrease during the PF injec9on and the PF machine
study can be avoided.

Fast beam mode switch scheme isstrongly required.
5~10min

Schematic view of the beam-mode switches.
The block pulses show beam gate timings.

Stored Current (mA)

LERHER~50mA
Slow switching

PF

Stored Current (mA)

One day< ~1mAAR injection

Acer achievement of pulse‐to‐pulse switching injec9on
AR has not participated inthe simultaneous injection yet.

< ~33μA

HER:12.5Hz
LER:12.5Hz
PF:0.5Hz

Machine studies• SuperKEKB– Vacuum R&D (Suetsugu’s talk)• Counter‐measures for ECI• Movable mask, radia9on from vacuum chamber etc.
– RF system• High power opera9on of klystron• SCC reverse phase opera9on (Y. Morita’s talk)– Beam monitor system• Feedback system• BPM signal detec9on circuit– Beam transport• Abort window (Mimashi’s talk)Machine studies [cont’d]• SuperKEKB (cont’d)– Beam behavior, beam dynamics• Stability of beam orbit, eﬀects of electron clouds– Physics Detector• Background study (Iwasaki’s talk)• KEKB performance– e‐/e+/PF simultaneous injec9on (Furukawa’s talk)– Side eﬀect of large tuning knobs– eﬀect of compensa9on solenoid– Measurement of x‐y coupling at IP and its chroma9city– Horizontal oscilla9on in physics run• Others– Study for LHC crab cavity, Positron target for ILC

Side effect of a large tuning knob
R2=37.29 units

LER R2

η=10 units

iSize Bump 3 mm
to check response of size monitor

Original segng
R2=7.99

Knob zeroThe vertical beam size is enlarged due to the side effect of a large tuning know such as 30
units
of R2 knob.
21
If a large x-y coupling remains at IP, the luminosity degradation may not be recovered bythe tuning knobs.

Vertical beam size [µm]R2=‐21.36 unitsx-y coupling measurements at IP(Ohmi, Tobiyama, Ieiri, Seimiya, Zhou, Ohnishi)• Methods– Kick the beam horizontally by injec9on kicker or
PLL– Measure the horizontal and ver9cal (turn‐by‐turn)posi9ons near IP (at OctoPos BPM or QCSBPM).
– Both the cases of single beam (single bunch) andthe the pilot bunch (physics run) were measured.

• Preliminary results– Measured values of coupling at IP are diﬀerent
between the single beam and the physics run.

There is a big difference between the single beam and physics run.

R1
R4
Monitor calibration is not enough.

R3
R2

Machine study on the effect ofBelle solenoid• It has been known that the luminosity at 1S or 2S ismuch lower than that at 4S or 5S.
• At KEKB, the strength of Belle solenoid and thecompensa9on solenoid are not changed dependingon the beam energy.
• It was suspected that this untracked solenoid ﬁeld is
responsible for the lower luminosity at 2S and 1S• A machine study was done at 2S with the Bellesolenoid and compensa9on solenoid which is tracked
to the beam energy.

5S and 2S runs in 2008

Y(5S)

Crab oﬀY(4S)
oﬀ‐reso.

Y(2S)Machine Study on the effect of Belle solenoid at 2S

5S run2SMS

2S run (c. sol.)

2S run2S oﬀ‐reson.

Horizontal dipole oscillation• Observa9ons– In the physics run, the both beams oscillate con9nuously inthe horizontal direc9on.
– The oscilla9on frequency corresponds to the π‐mode ofthe beam‐beam interac9on.
– The oscilla9on amplitude changes like a saw‐toothinstability. One cycle of the saw‐tooth is about 300 turns(~3 msec). The maximum amplitude is about 1/3 σx.
– Some luminosity degrada9on may be brought by thisoscilla9on.
– This oscilla9on became conspicuous in FY2009, although
the oscilla9on had been observed before depending on
the beam currents.

Example of Horizontal oscillation of
an LER bunch

Amplitude (arbitrary unit)

This oscilla9on exists constantly during
the physics.

turns
The amplitude is ~ 1/3 σx.

M. Tobiyama

Horizontal dipole oscillation[cont’d]• Machine studies and data analysis– Coupled bunch mode?
• ‐2 mode is dominant (M. Tobiyama)– Small number of bunches• ~100 bunches: No oscilla9on wasobserved with the same bunch currents.

– Single beam with the same numberof bunches• No coupled bunch oscilla9on wasobserved even at the π‐mode tune.

π-modetune

Operation statistics

Annual integrated luminosityAveraged daily luminosity

Operation statistics

2008

[%]

Physics Run

73.5

Machine Study

9.8

Machine Tuning

1.7

Beam Tuning

8.5

Trouble3.5

Maintenance2.7

Others

0.3

2009

[%]

Physics Run

76.8

Machine Study

6.8

Machine Tuning

7.5

Beam Tuning

4.4

Trouble2.2

Maintenance

1.9

Others0.4

Troubles

2008

[%]

Vacuum

24.5

Magnet

11.0

BT

7.3

RF

24.2

Safety0.0

Facility

0.0

Control

0.7

Beam Monitor

1.1

Belle

9.5

LINAC

2.2

Refrigerator

0.4

Others

19.0

2009

[%]

Vacuum

10.5

Magnet

7.8

BT

35.0

RF

26.5

Safety0.0

Facility

0.0

Control

0.0

Beam Monitor

0.0

Belle

2.2

LINAC

4.2

Refrigerator

13.2

Others0.6

Beam aborts (LER)

Beam aborts (HER)

Summary and future prospects• The total integrated luminosity accumulated by Belle detector
reached 1000 C‐1 on Nov. 29th .
• The peak luminosity exceeded 2 x 1034 cm‐2 s‐1 by using skew‐
sextupole magnets.
• e+/e‐ simultaneous injec9on was realized.
• We are s9ll making eﬀorts to increase luminosity with crabcrossing.
• Since KEKB is the world‐highest luminosity machine, anythingthat improves its performance might be important inSuperKEKB.
• KEKB has been useful for the R&D machine for SueprKEKB.
• In the next ﬁscal year, 1 or 2 months’ beam opera9on isscheduled. We will make the best use of this last opportunity
at KEKB for SuperKEKB.

SPARE SLIDES

2S run in Autumn 2009

R2=31.58 unit

Comments

R2= ‐28.42 unit

HER R2元値
R2=1.58（1）HERも Knobを大きく(30 unit) 立てると副作用でビームが太る。
（2）HERもKnobを戻せばビームサイズは戻る。再現性は良い。
41zeroComments

Side eﬀect is large also in calcula9on.

Emisance and horizontal beta‐func9on at IP becomes large.

42（1.5 m→ 2m）

Summary of R(0) measurements

HERLERr1r2r3r4r1r2r3
r4

4/30
0.01120.00163
0.0616-0.05470.01040.01370.673-0.144• LER R2 is very large.

5/13
0.01420.001390.111-0.0926
0.00850.01370.189
0.0277

1 unit (R2)=4.1x10‐4m

5/26
0.009740.00169
0.06180.02450.00961
0.01310.221-0.061
K. OhmiPossible scenario• Remaining R2 of LER at IP even acer the op9cs
correc9on is very large.
• But, it can not be corrected by the tuning knob
due to the side eﬀect of the knob.
– Belle solenoid compensa9on is not good?
• Change the solenoid ﬁeld slightly?
• Re‐consider the method of op9cs correc9on?

D. Zhou, K. Ohmi, Y. Seimiya, Y. Ohnishi

β x*β y* ≅ 0.094m
β y* / β x* ≅ 0.063

HER coupling chroma9city scan panel

R‐chroma9city knob (HER)

5/3 evening

5/6 morning

R‐chroma9city knob (LER)

5/3 evening

5/6 morning