Overview of Phase 1Commissioning

Y. Funakoshi for SuperKEKB Commissioning
GroupAccelerator Laboratory, KEK
2016.06.13@21th KEKB Review

SuperKEKB
Ø Upgrade project of KEKB B-factory
pSearch for new physics beyond the standard model at B-meson regimeØ e− - e+ two-ring collider consisting ofInjector (Linac): L ~600 m
p Damping ring (e+): C ~100 m
p Main ring (MR): C ~ 3016 m− HER: 7 GeV e−, 2.6 A− LER: 4 GeV e+, 3.6 A
p Belle-II detectorp

Ø Design luminosity
p80 x 1034 cm−2s−1(~40 times of KEKB)

2SuperKEKB Commissioning Phases
2016 Feb. ~ June

Phase 1w/o QCS and Belle II~2017 Autumn (~ 5month)~2018 Autumn

Phase 2
w/QCS and Belle IIPhase 3
w/ full Belle II

w/o Vertex detector

basic machine tuning
vacuum scrubbing
OpPcs tuning
BKG study

DR commissioning
BKG study
Luminosity tuning
Target luminosity:
1 x 1034 cm-2 s-1

Physics Run
Luminosity tuning

Mission of Phase 1 operation(Feb. 2016 ~ June 2016)• Startup of each hardware system• Establish beam operaPon so_ware tools• PreparaPon for installaPon of Belle-II detector– Enough vacuum scrubbing• Request from Belle II group: ~1 month vacuum scrubbing with beam
current of 0.5~1A (360~720Ah).

– Beam background study with test detector (named Beast)• High beam current operaPon– Find/solve problems associated with high beam current
operaPon• OpPcs study w/o IR (no detector solenoid)– Low emibance tuning• Other machine studies

History of Phase 1 operation
e-HER wiggler ONe+LER wiggler ON

Short break forInjector work

Red: total beam current
Purple: vacuum pressure
Cyan: beam lifePme
Regular maintenace

Short break

Short break
Solenoid installaPonat bellows (LER)

We plan to shutdown the rings on June 28th.

Machine parameters in Phase 1LER

HER

Units

Beam energy

4.000

7.007

GeV

Beam current

910 (~40)

830 (~40)mA# of bunches

1576

1576

Bunch current

0.58

0.52

Hor. emibance

1.8

4.6

MomentumcompacPon

2.45 x 10-4

4.44 x 10-4

Energy spread

7.5 x 10-4

6.3 x 10-4

Total Vc

7.56

12.45

MV

Bunch length

4.6

5.3mm

νs-0.019-0.02544.59/44.63

45.57/43.61

U0

1.76

2.43

Wiggler ON

τx,y/τx

46/23

58/29

Wiggler ON

Tune νx/νy(): opPcs correcPonmA
Zero current

Zero current

as of June 12th

Machine parameters in Phase 3

Y. Suetsugu

Guideline for vacuum scrubbing and achievement as of June 12th

Request from Belle II group: ~1 month vacuum scrubbing with beam current of
0.5~1A (360~720Ah).

Startup of SuperKEKB (3 months)• Much faster startup than KEKB– KEKB beam currents achieved a_er ﬁrst 3 months• LER: ~300mA, HER: ~200mA (540mA, 300mA: 4 months)– SuperKEKB beam currents achieved a_er ﬁrst 3months• LER: ~650mA, HER: ~590mA (820mA, 740mA: 4 months)• Compared with KEKB…

– Each hardware component has been upgraded withexperiences at KEK and has worked ﬁne (RF, Magent,Vacuum...)– The bunch-by-bunch feedback system has more
eﬀecPvely suppressed instabiliPes.
– OperaPonal tools (such as closed orbit correcPonsystem) has worked ﬁne based on experiences atKEKB.
– Less machine troubles than KEKB so farBeam background study using Beastdetector• Touschek background– Change verPcal beam size by using ECK (EmibanceControl Knob)• Vacuum background– Vacuum bump study• InjecPon background• Collimator study
Details are given in the talk by H. Nakayama.

H. Nakayama

BEAST Phase1 sensors at IP
PIN diodes

LYSO/CsI
crystals

He3 tubes(thermal neutrons)

BGO crystals
Diamonds

CLAWS
scinPllators

Micro TPCs
（fast neutrons）

Various measurements (fast charged parPcle, high-energy photons, thermal/MeV neutron, dosimetry, etc..) to validate beam loss simula4onIssues with high beam currents••••

Nonlinear vacuum pressure rise as funcPon of beam current (LER)
VerPcal beam size blowup as funcPon of beam current (LER)
Frequent beam aborts associated with vacuum burst (LER)
Longitudinal coupled bunch instability (LER)– Instability was ﬁrst observed around 660mA. The mode number is~600. We needed the use of longitudinal feedback system to suppress
it. The source of the instability is sPll unknown. At KEKB, we neverneeded the longitudinal feedback system.

• Longitudinal coupled bunch instability (HER)– SomePmes, detuned caviPes induce the instability due to thefundamental mode. -1 mode damper was set up to suppress theinstability.

• Hardware troubles due to the high beam currents– Vacuum leakage by the direct hit by the beam at bellows near theabort kickers (HER) (Suetsugu’s talk)– Damage to the feedthrough of the transverse FB kicker (LER)(Tobiyama’s talk)Y. Suetsugu

Nonlinear pressure rise against beam current in LERnnnn

The pressures at whole LER ring showed the nonlinear behavior
against the beam current.
The behavior is quite similar to that of electron currents measured
at aluminum parts without TiN coating.

We have aluminum bellows chambers
along the ring without TiN coating. The
bellows chamber has a length of 0.2 m
and located every 3 m on average.
Number of such bellows chamber is 810.
Countermeasuren Installation of solenoid magnets at thebellows.
n We have installed permanentsolenoid magnets at all of bellows
chambers during short break (June02-05)

Solenoid: 50~100Gauss

More details are discussed in the talk by Y. Suetsugu .

13

LER vertical beam size blowup
Blowup study with shorter bunch spacing
w/ emibance knob

w/o emibance knob

w/o emibance knob

3.06 spacing (1576 bunches)

June 1st (before installaPon of solenoids
at bellows chambers)

3.06 spacing (1576 bunches)

June 6th (a_er installaPon of solenoids
at bellows chambers)

One of the moPvaPon of installing solenoids was to check their eﬀects to the beam size.

Blowup study
beforeJune 1st (before installaPon of solenoids
at bellows chambers)

a_erJune 8th (a_er installaPon of solenoids
at bellows chambers)

The solenoids at bellows were eﬀecPve to raise the blowup threshold by a factor 1.5.
The electron clouds seem to be responsible for the beam blowup.
We may need more solenoids for higher beam operaPon.
More details will be given in the talks by Y. Suetsubu and K. Ohmi.

Vacuum burst in LER

Y. Suetsugu

Ø Pressure bursts accompanying beam loss in LERnnn

One big concern is that beam aborts accompanied by localized pressurebursts have been frequently observed from the early stage of thecommissioning in the LER.
The beam loss monitors trigger the beam aborts.
Frequent pressure bursts have occurred near or inside the aluminum beam
pipes in dipole magnets.
Our beam pipes for dipole magnets have a groove structure as a countermeasure against electron cloud effects.
The beam current where the bursts occurred has
Increased gradually.
The reason for the pressure bursts is not well understood.
Possible causes are the discharge at poor
electrical contacts by the wall current andthe collision of dusts (small particle) with circulatingbeams. A knocker against vacuum chamber could
reproduce the vacuum burst. This result seem to support
the hypothesis that the burst is induced by dust parPcles.
nnnn

More details are discussed in the talk by Y. Suetsugu.

16Locations of vacuum burst in LER

ArPﬁcial

17

Optics corrections• Base measurements for hardware system check– BPMs

• BPM check with beams (orbit bumps) -> We found misconnecPon or mis-cabling of BPM cables with ~>20 BPMs.
• Gain calibraPons of BPMs have been done with beams.
• Quad-BPM measurements (to measure diﬀerence between
ﬁeld center of quadrupole magnets and the center of nearby BPM) have been almost ﬁnished.

– Steering magnet• Check with beams (orbit bumps) -> We found an error withthe excitaPon curve of steering magnets.

– Closed orbit correcPon system• Closed orbit correcPon is a basis of opPcs correcPon. A
reliable closed orbit correcPon system has been establishedbased on the above measurements and modiﬁcaPons.

Beam based BPM offset measurement(Quad-BPM, SextBPM)

Ring circumference• From the orbit measurement, we can know
the ring circumference.
– LER: CMeasurement – CDesign ~2.0mm (Cir: 3016m)– CLER – CHER ~ 0.2mm (LER chicane can adjust +/3mm)– Magnet group has done a good job in thealignment work.

Method of optics correction• At SuperKEKB, we follow the method successfully
used at KEKB.
• OpPcs correcPons on X-Y coupling, dispersions
and beta-beat are done iteraPvely.
• Since there are not enough single path BPMs, werely on convenPonal BPMs.
• For the measurements of X-Y coupling and betabeta, orbit responses are measured with single
kicks by steering magnets.
• For the measurement of dispersion, we use ausual RF phase frequency change.
Details are given in the talk by H. Sugimoto.

Highlight of low emittance tuning• The X-Y coupling correcPon and dispersion
correcPon are important to get a low verPcal
emibance.
• While the HER correcPons went well, weencountered a diﬃculty in the LER correcPons.

– The obstacle of the correcPons was leakage magnePc
ﬁeld from the Lambertson septum magnets whose
main component is skew-Q.
• We have made two countermeasures against the problem.

– The use of skew-Q coils of the SF magnet nearby the Lambertson.
(downstream of the Lambertson septum)– InstallaPon of permanent skew-Q magnet in the upstream of theLambertson septum.

H. Sugimoto

KEKB

H. Sugimoto
Measurement:

VerPcal leakage orbit induced byindependent 6 steering kicks.
- Induced horizontal orbit amplitude
Is about 2-3 mm in its peak.

Correctors:
SkewQ winding of sextupolesH. Sugimoto

Correctors:
SkewQ winding of sextupoles

H. Sugimoto

The skew quadrupole magnets to cancel
the leakage field from the Lambertson

Ferrite block
Ferrite block
Size: 100 x 25.4 x 150 (mm)B 〜 550 (Gauss)r = 85.5 (mm)→ SK1 = - 7.7e-3 (/m)
which is adjusted the requirement from opPcs.
N. Iida, M. Kikuchi, K. Kodama, T. Mimashi, T. Mori, T. Tawada

Before and a_er installaPon of Ferrite blocks
X-Y Coupling<rms(Δyi)>= 26.785 → 19.839 µm

H. Sugimoto

VerPcal dispersionΔηyp= 6.2 mm à 4.2 mm

Present status of linear optics corrections
Items

KEKB typicalvalue (LER)

LERHERUnit

X-Y coupling
average of rms (Δy1-6 )

19.8

7.7

H. Dispersion
rms (Δhx )

14.8

16.1

10mm

V. Dispersion
rms (Δhy )4.2

4.88mmBeta-xrms (Δbx/bx )

4.9

4.36%

Beta-yrms (Δby/by )

5.3

3.76%

mm

More details will be discussed in the talk by H.Sugimoto.

Beam size measurement by using X-ray monitor
March 23rd, 2016
εy = 96pm (by = 67 m @source)
εy/εy = 5.3% (ex = 1.8nm)

εy =356pm (by = 7.7 m @source)
εy/εy =7.7 % (εy= 4.6nm)

April 5th, 2016
εy = 20pm (by = 67 m @source)
εy/εy = 1.1% (ex = 1.8nm)

Target verPcal emibance (LER) in Phase 1 is ~5pm.

Vertical beam size measurement(after permanent skew-Q installation)
Before ferrite installaPon
A_er ferrite installaPon
Targetεy〜20pm

εy〜10pm
εy〜5pm32

HER Beam size measurement by using X-ray monitor
June 1stHER σy@source point = 40µm? -> εy=210pm
This verPcal emibance is inconsistent with opPcs correcPon results.

HER X-ray monitor study (June 9th)Single slit

URA
ε knob=0mulP.

βy=7.636m (original)
βy=4.00m

knob=1.3

Change camera gain
The current dependence of HER verPcal beam size seems to be fake.
34

Single slit

HER X-ray monitor study (June 9th)βy=7.636m(original)
βy=4 mData with βy =7.636 x √⁠4/7.636
The measured beam size does not scale the beta funcPon.
Is there any oﬀset in the measurement such as coupling from horizontal size?
35

More details are given in the talk by J. Flanagan.

Summary• A_er 5 year’s upgrade work from KEKB, Phase 1 operaPonof SuperKEKB (w/o Belle-II detector and IR) started in Feb.
2016 and on the way.
• The startup of SuperKEKB operaPon is relaPvely smooththanks to experiences at KEKB.
• In preparaPon for installaPon of Belle II detector in Phase2, vacuum scrubbing is being done and beam backgroundstudy has been done with Beast detector.
• The opPcs correcPon study is going on energePcally.
• The LER low emibance has been much improved by thecorrecPon of leakage ﬁeld of Lambertson septum.
• The calibraPon of X-ray monitor is an important tuningitem.
• We observed the verPcal beam size blowup in LER. The
source of the blowup seems to be the electron clouds.
• Injector has worked stably. For Phase 2 and 3 operaPon, wewill need more improvements.

SPARE SLIDESHER Phase 1 LatticeInjection phase vs efficiency

Error bar: RMS in 100 shots.

入射位相を変えながら入射効率を測定した。
測定時の電流HER: 40~95 mALER: 40~90 mA・現在の設定値は最適な位相からずれている
HER変更: 255° à 245°
LER変更: 6° à -5°

HER: Δφfull = 45 deg. → 14 σδ ↔ 28 σδ (model); ); 16 σδ @ x/ σx > 25
LER: Δφfull = 80 deg. → 28 σδ ↔ 32 σδ (model)
see next pageComments• HERのεy は、本当に巨大なのか？ (really big ?)Touschek lifePme ~530 min
when εy =180 pm (εy / εx = 3.9 %)HER

σy = 37 μm @ X-ray
HERのopPcs測定からは推測できない (see next)
HER

abort sext. OFFLER
abort sextをOFFすればoﬀ-momentumの横方向の口径はかなり大きくなる。

Injector Status• Requirements to Linac– Higher charge for electron and positron– Lower emibance for electron and positron• Linac challenges– Low emibance and high intensity e• high-charge RF-gun– Low emibance e+• damping ring

– Higher e+ beam current• new capture secPon
with ﬂux concentrator– Emibance preservaPon• precise beam control• Status in Phase 1– RF gun: sPll under development– Damping ring: under construcPon– Flux concentrator: in pracPcal use– Charge at end of BT• e-: ~0.6nC, e+:~0.6nC (2bunches)–41 Dedicated machine study for injector: 1 day / week

SuperKEKB requirements (Phase 3)
KEKB(e+/e-)

SuperKEKB(e+/e-)

Charge [nC]

1/1

4/5

Normalizedemibance[µm]2100/300

100/50 (H)20/20 (V)

Target charge in Phase 1: ~1nC

Layout of electron gun(Thermionic DC gun andphoto-cathode RF gun)

予備実験(4/25)• 南トンネルの 3個のベローズに「永久磁石」を取り付けて、圧力の振る舞いを調べた。
NN

S

NS

CCG

S

30 x35 x6個 x上下
970G@磁石表面
S

ベローズ内部表面で中央付近Bz = 60～120 G
磁石の真下で極性反転

Sｔ1.6 Fe plateNN

Vertical Emittance and Dispersion⌅y ⇠2Jz ⇤ 2yh⇥y2 iLERHERJz ⇠ 2y ⇠ 17 [m]⇠ 6.3 ⇥ 10 4"y [pm]"y [pm]Jz ⇠ 2y ⇠ 20 [m]⇠ 7.7 ⇥ 10 4qh⌘y2 i [mm]qh⌘y2 i [mm]Beam lifetime from vacuum andTouschek effect

1/LifePme– Change verPcal beam size -> LifePme measurement– LifePme from vacuum: 129.7 min. @(350 mA, 1576bunches)– Actual lifePme: 75min. -> Touschek LifePme:177min.

1/σyTouschek lifetime from simulation• εy/εx = 15%, Ib = 0.25 mA• LifePme from simulaPon: 113 min.
113min15％

History of Phase 1 operatione-e+

HER injecPon tuning
LER injecPon tuning
BT tuning

Short break forInjector work
Red: total beam current
Purple: vacuum pressure

Short breakHistory of vacuum scrubbing

Y. Suetsugu

Ø The beam currents and average pressures (2016/4/30)[LER]• Max. Beam current: 650 mA• Avg. Pressure ~ 3x10-6 Pa• Life Pme ~ 60 min.

[HER]
• Max. Beam current: 590 mA• Avg. Pressure ~ 3x10-7 Pa(whole ring)~ 1x10-7 Pa(arc secPons)• Life Pme ~ 600 min.

Request from Belle-II group: ~1 month vacuum scrubbing with beam current of 05~1A.48

Blowup study

Machine study to be donein May and June (>30 shifts)• More opPcs study• X-ray monitor calibraPon• LER beam size blowup• Longitudinal/transverse bunch-by-bunch
feedback system• Beast background study• Impedance measurement• RotaPonal sextupole magnet• Dithering coils• Beam transport line study• Linac study (RF gun etc.)