Ring commissioning
2014.3.4
SuperKEKB Review
Y. Funakoshi for the SuperKEKB
commissioning groupSuperKEKB rings master schedule�
Calendar�

2011�

2010�

Japan FY�

2010�

2013�

2012�
2012�

2011�

2014�

2015�

2014�

2013�

・・・�

2016�
2016�

2015�

now here

KEKB operaEon�

SuperKEKB‐MR(LER&HER) construc:on�SuperKEKB commissioning�

opEcs design�

phase 1dismantling KEKB�

w/o QCS
w/o Belle II�fabricaEon and tests of MR components�
TiN coaEng & baking of beam pipes�

MR buildings construcEon�

ﬁnal assembly,
RF condiEoning�

reinforce electricity and cooling facility�
fabricate QCS‐L�
detector upgrade to Belle II�

cool down
w/Belle II�reinforce RF, vac, etc.
for higher beam current

fabricate QCS‐R�
roll in �

roll out �

Belle roll out�

opEcs design�rotaEon�roll in �

phase 3w/ full Belle II�
w/ QCS
w/ Belle II (no VXD)�

DR complete before phase 2 �

install, assembly and set up�cabling and piping�phase 2

SuperKEKB‐DR construc:on�

VXD install �

fabricaEon and tests of DR components�
install, assembly and set up�
DR tunnel construcEon�
DR buildings construcEon�
electricity and cooling system�
K. AKAI, Overview of ring construcEon status and schedule, 19th KEKB Accelerator Review, Mar. 3, 2014, KEK

2Commissioning phase 0 (2013 Sep. ~ 2014 Dec.)• Machine condiEon– SuperKEKB rings: construcEon– Linac commissioning in parallel with its
construcEon• Tuning items– Presented by the talk by Satoh san this morning.
– The ring commissioning team is parEcipaEng to
the linac commissioning.
– In parallel, the commissioning so_ware forSuperKEKB rings is being prepared (A. Morita).

Commissioning phase 1 (2015 Jan. ~ June)• Machine condiEon– No QCS, No solenoid (no Belle II), No beam collision• Tuning items– Linac tuning (if necessary)– Basic commissioning of machine (~ 1.5 month)• InjecEon tuning, Hardware check and bug ﬁx, so_ware bug ﬁx– Vacuum scrubbing (>~3 months)• Belle II people request enough vacuum scrubbing in this stage (before
Belle II roll‐in). At least one month with beam currents of 0.5 ~ 1 A.

– Damping ring commissioning (start from May 2015)• Beam injecEon with damping ring

– Detector beam background• Study with Beast detectors, check of collimator system (two new‐typecollimators in LER)

– Some opEcs tuning• With day‐1 opEcs• Low emigance tuning w/o Belle‐II solenoid– Study of beam instability (FII, e‐cloud)• Tuning on bunch‐by‐bunch feedbackPhase 1 optics (HER)M. Kikuchi
Commissioning WS

The is the original scenario.
It is desirable to complete the commissioning of DR before Belle II roll‐in.
There is no “Damping Ring Group”. The same stuﬀs as SuperKEKB team must do thethe commissioning. Collaborators (from SLAC?) for DR commissioning will be welcome.

Phase 1 beam monitors• X‐ray monitor– Can measure verEcal emigance with small beam currents(~30mA) with nominal bunch current.

• Streak camera– Can measure bunch length• Turn‐by‐burn BPM– ~110 bpms

• Energy spread measurement– Not easy
– At KEKB, the measurement was done by using Belle detector(hadron raEo) at narrower resonance (Y(2S)). We didn’t noEce
that the microwave instability actually happened in KEKB LER
for a long Eme.

Commissioning phase 2 (2016 Feb. ~ June)• Machine condiEon– w/ QCS, w/ Belle II (w/o VXD),TOP detectors parEally installed, fullaccelerator tuning, no physics experiment• Tuning items– OpEcs tuning••••

TentaEve target values of IP beta’s: βx*: x4, βy*: x8
OpEcs tuning with QCS and Belle II solenoid
Low emigance tuning w/ Belle II solenoid
OpEcs tuning w/ beam collision– Detector beam background• Study with Belle II detector, Beast II detector, test of conEnuous injecEon– Increase of beam currents (instability, RF power, vacuum issues)• Detector background will be tested.
• ConEnue upgrade for RF system (support ~70% of design beam currents)– Beam collision tuning• Orbit feedback (fast verEcal feedback, dithering system)• Collision tuning w/ “Nano‐Beam” scheme– Luminosity tuning• Tuning knobs (x‐y coupling at IP etc.)• Target luminosity: 1 x 1034 cm‐2 s‐1 (design of KEKB)

Detuned Optics (4x8)
Example of machine parameters for 1034 cm-2s-1

βx*: x4, βy*: x8, x-y coupling =2 %, ξy ~ 0.025, ILER = 1 A.
9Commissioning phase 3 (2016 Oct. ~ )• Machine condiEon– Full set of Belle II, Physics experiment will start.
• Maybe some TOP counters will be delayed.

• Tuning items– OpEcs tuning• Toward design values of IP beta’s– Maybe it will take several years.

• Low emigance tuning:– Design values for verEcal emigances are very small. DemonstraEon of feasibility of
TLEP.

• OpEcs tuning w/ beam‐beam eﬀect– Detector beam background• Establishment of conEnuous injecEon (azimuthal VETO)– Increase of beam currents• Design values are as twice high as those of KEKB.

– Luminosity tuning• Study on eﬀects of laqce non‐linearity and space‐charge and theircorrecEons or compensaEons?
• Stability of tuning will be an important issue. (conEnuous opEcs correcEon?)• The ﬁrst important milestone in phase 3 is to achieve the luminosity 1 x 1035.

Beam monitors in phase 2, 3
• Turn‐by‐turn BPM– ~270 BPMs

• Gated turn‐by‐turn BPM– Measure oscillaEons of pilot bunches• Enable conEnuous opEcs correcEon?

• BPM for orbit interlock– Libera Brilliance+• turn-by-turn mode, latency <10 turns• Evaluation in progress: Latency < 4 turns• Beamstrahlung monitor• BPM for IP orbit feedback• Fast luminosity monitor (S. Uehara, P. Bambade)SuperKEKB BxB FB

Gated turn-by-turn monitor
509MHz/1GHz narrow band detector, or
medium-band detector

TBT
Data

FPGA
(Spartan6)

Pilot bunch signal or
injection beam
BPM
Fast gate
switch

BPF
&Amp

Log
Amp

14bit
ADC

Gate width˜6ns

508.886MHz & FID

M. Tobiyama

phaseLattice preparation

Y. Ohnishi

sub-phaselattice, commissioningIb (mA)

Phase 1.1

wiggler off, device check,
optics tuning, vacuum scrub.

< 30-100Phase 1.2

wiggler on, circumference, optics
tuning< 30

high emittance for vacuum
scrubbing (LER)

500-1000

Phase 1.4

optics tuning (low emittance)< 30

Phase 2.1

vertical beta* = 80 mm,
optics and injection tuning

< 30

:

:

Phase 2.x

vertical beta* = 2.2 mm,
optics and luminosity tuning

1000/800

Phase 3.1

vertical beta* = 2.2 mm,
optics and luminosity tuning

1000/800::

ultimate beta*,
optics and luminosity tuning

3600/2600

Phase 1
Phase 1.3

Phase 2Phase 3::Phase 3.x

IR status

No QCSNo Belle II

QCS
Belle II
w/o VXD

QCS
Belle II
with VXD(Physics Run)

13

Injection/Abort Construction Schedule
T. Mori
Commissioning WS• Phase 1– The new HER injecEon/abort system is installed• This is urgent issue & main topic of this talk

– The KEKB LER injecEon/abort system is preserved.
• DR is not ready at the beginning of Phase 1– Emigance is large; new LER system doesn’t work well for Phase 1• The LER current must be low to protect the abort window (< 500mA)• Phase 2

Or the ring emigance should be enlarged.

– The new LER injecEon/abort system is installed• DR is ON• New LER chambers has smaller apertures than those of KEKB
– They should be installed at the same Eme not to build cavity structures– New injecEon channel can’t be used for large emigance beam of Phase 1

ICFA Mini-Workshop on Commissioningof SuperKEKB and e+e- colliders• 11‐13 November 2013 KEK• Registrated a-endees: ~70• hgp://kds.kek.jp/conferenceDisplay.py?
ovw=True&confId=12760• Reports from LHC, BEPC‐II , PEP‐II, CesrTA,
DAΦNE, τ‐Charm plans at LNF and SuperKEKB

Challenges at SuperKEKB
Summary of SuperKEKB commissioning workshop (by U. Wienands)*)• Emigance tuning and geqng the beam opEcs under control– Should learn from other machines (CesrTA, LHC, DAΦNE,…)• Electron‐cloud eﬀects– Maybe no problem at SuperKEKB?

• HOM heaEng and discharges– “High beam current supervisor”• IR and background tuning– More collaboraEve works between accelerator and Belle II
people than KEKB will be needed.

• Injector tuning– Should learn from FACET and ATF.

*) to be appeared in ICFA Beam dynamics Newsleger

More challenges at SuperKEKB• Beam‐beam related issues (most serious issues so far)– Dynamic aperture with beam‐beam eﬀects– Beam‐beam + laqce nonlinearity– Beam‐beam + space charge• InstabiliEes and their suppression by feedback system– So far, it seems that we will well control the instabiliEes byusing feedback system based on experiences at KEKB.

• Damping ring issues– No experience at KEKB.

• RadiaEon safety issues– Study has just started.

Beam lifetime
KEKB (design)

KEKB (opera3on)

LER

HER

LER

HER

LER

HER

RadiaEve
Bhabha

21.3h

9.0h

6.6h

4.5h

28min.

20min.

Beam‐gas

45ha)

45ha)

24.5min.b)

46min. b)

10h‐10min.
(3.85min.c))

10min.

5.9h

7.4h~133min.

~200min.

6min.
(2.97min.)

6min.

2.6A

1.1A

1.6A

1.1A

3.6A

2.6A

0.12mA/s

0.04mA/s

0.23mA/s

0.11mA/s

10mA/s(20.2mA/s)

7.2mA/sTouschek
Total
Beamcurrent
Loss Rate

SuperKEKB

4nC@25Hz 2.9nC@25Hz(8nC@25Hz)a) Bremsstrahlungb) Coulomb scagering, sensiEve to collimator seqngc) With beam‐beam best so far
As for loss rate, beam loss accompanied with the beam injecEon should be added.

Optimization of DA with beam-beam effect(νx, νy)=(44.65, 46.535)(νx, νy)=(44.53, 46.54)
LER

LER

L~6x1035
Δx/
σx

Δx/
σx

L~8x1035

H. Sugimoto

Δε
/σε

Δε
/σε

Optimization is done by sextupoles, skew sextupoles, and octupoles.
Touschek lifetime is improved up to 230 sec. Still short lifetime.

19SuperKEKB requirements (tentaEve)
KEKB(e+/e‐)

SuperKEKB(e+/e‐)

Charge [nC]

1/1

4/5

Normalized
emigance[µm]2100/300

100/50 (H)20/20 (V)Summary of Session on 
Ring Optics and Intensity
Effects
Frank Zimmermann
SuperKEKB Commissioning Workshop
KEK, Tsukuba, 13 November 2013

F. Zimmermann“to do” list:‐ oﬀ‐momentum opEcs correcEon‐ idenEfy dominant la6ce nonlineari8es inboth rings aﬀecEng luminosity‐ develop nonlinear opEcs measurement &correc8on scheme‐ opEmize nonlinear op8cs & DA including
space charge & beam‐beam eﬀect‐ compensa8on scheme for space charge‐ correc8on scheme with/for crab waist

Integrated luminosity(ab-1)

SuperKEKB luminosity projection
Goal of Belle II/SuperKEKB

Peak luminosity(cm-2s-1)

9 months/year
20 days/month

Commissioning starts
in early 2015.
Shutdown
for upgrade

Calendar Year

Spare slides

Software development (A. Morita)• Develop base so_ware– Class‐based so_ware stack– Reuse of so_ware components will be easier byusing an abstracted layer.
– Oﬀer an abstracted layer to apply to LER/HER/DR.
• OpEcs model• CommunicaEon between so_ware panels– OpEcs panel, COD correcEon panel …

Abort system of SuperKEKB
Horizontal kicker：
fast kick to abort window
VerEcal kicker：
slow sweep verEcally

VerEcal kicker

Beam proﬁle on abort window

Vert. kick

±​𝜎↓𝑥

Power
densitymaximum
at turning
points !!

••Low emigance beam has higher possibility of destroying
abort window than KEKB beam
Enlarging horizontal beam size required addiEonallySuperKEKB(LER)

SuperKEKB(HER)

Horizontal kicker：
fast kick to the Abort window
VerEcal kicker：
slow sweep verEcally
PULSED quadrupole：enlarge the horizontal beam size

Horizontal kicker：
fast kick to the Abort window
VerEcal kicker：
slow sweep verEcally
DC sextupole：enlarge the horizontal beam size

Abort fail‐safe system like KEK is also designed
SchemaEc view of new beam proﬁle on abort window±​𝜎↓𝑥Vert. kick

KEKB

T. MoriT. Mori, ICFA mini‐workshop @ KEK

20μm

6μm shi_T. Mimashi
27

Vacuum scrubbing at KEKB （HER/LER）

HER

LER

HER

LER

Emittance change in arc
Emittance of arc cell can be changed by field strength ofquadrupols.
Range is from 2 to 12 nm in LER and from 5 to 17 nm in HER,
respectively. nominal αpnominal αp29LER: Emittance change in wiggler section
Emittance can be adjusted by optics in Nikko section(No cavity).
Only adjust field strength of the quadrupole magnets
Emittance becomes 20* nm in case of 1 m dispersion at midpoint thestraight section.
LER: Nikko* without intra-beam scattering

30

Phase 2.1 LER (1/2)
Phase 3.x

Phase 2.1

LER

LER

beam size

σx = 1100 μm at QC2
rb = 35 mm at QC2
rb/σx = 31 (linear calc.)beam size

σx = 350 μm at QC2
rb = 35 mm at QC2
rb/σx = 100 (linear calc.)
KEKB
31

Phase 2.1 LER (2/2)Δy (mm)LER

Δy (mm)

QC1P: misalignment
ΔyQC1P = 100 µm(opposite)+‐5 mmArc: < 5 mm

The ver3cal orbit distor3on is less than 10 mmwithout any correc3ons. We can ﬁnd the orbit.

32

Machine parameters with QCS
Pilot runUl3matePhase 2.x

Phase 3.x

Parameters

symbolEnergyE#Bunches

nb

Emittance

εx

2.2

5.2

Coupling

εy/εx2Hor. beta at IP

βx*Ver. beta at IP

unit

LER

HER

LER

HER

4

7.007

4

7.007

GeV

3.2

4.6

nm

2

0.27

0.28

%

128

100

32

25

mm

βy*

2.16

2.4

0.27

0.3

mm

Bunch current

Ib

1

0.8

3.6

2.6

A

Beam-beam

ξy

0.024

0.0257

0.088

0.081

Hor. beam size

σx*

16.8

22.8

10

11

µm

Ver. beam size

σy*

308

500

48

62

nm

Luminosity

L

2500

2500

1x10348x1035cm-2s-1
33

Collimator control systems• Careful operaEon is important at SuperKEKB/Belle‐II– Keep IR loss <1GHz, while total collimator loss >600GHz– Miss‐operaEon of collimator(espc. verEcal ones) easily resultsin x10 or even x100 detector background level– Aim to develop semi‐automaEc control algorithm• Input informaEon:– beam lifeEme, loss rates at collimators, sub‐detector BG levels,
injecEon eﬃciency, and IR loss distribuEons, etc..

• IR loss rate distribuEon gives insight on which BG source andtherefore which collimator we should adjust• IR loss monitor R&D has started
BPAC (Sep. 10, 2013)

Difficulty of SuperKEKB• The commissioning phase 3 will be the mostcriEcal phase.
– The true diﬃculty of SupeKEKB will be recognizedin this phase.
• CorrecEons of machine errors seem the key issue.
• Stability of machine condiEon seems important.
– ConEnuous opEcs correcEon?

– Some unknown diﬃculEes will possibly appear.
– My personal impression: Important milestone ofluminosity: 1 x 1035 cm‐2 s‐1.

Detector beam background• Belle II has to be operated under the situaEon of low beta and low
emigance opEcs and high beam currents.
• In phase 2 and 3, we will study the beam background under therealisEc beam condiEon.
– Seqng of Belle abort level is important.
– Tuning with collimators (movable masks) is essenEally important.
– Comparison with simulaEon is important.
– We will need an extrapolaEon to lower beta funcEons• RadiaEve Bhabha process: relaEvely straigh„orward• Touschek eﬀect: not so straigh„orward ‐> rely on simulaEon (step‐by‐step)• Beam‐gas scagering: not so straigh„orward ‐> rely on simulaEon (Step‐by‐step)– Beam current increase will be done with carefully observing the beam
background.
– More closer collaboraEve works between accelerator and Belle II people
than in KEKB will be essenEal.

w/ beam-beam w/ damping andradiation excitation

CoordinateBeamLossInjecEonLER2013_8_28_14_50_7.dat
CoordinateBeamLossInjecEonLER2013_8_28_14_50_7_SelectedEvents.dat ( ‐4m < IP < 4m):
9 events ‐> ~781 MHz

Dynamic Aperture with beam-beam(sler_1686) with damping 4000
turns

ΔΕ / σε

σx@InjecEon = 0.55mm‐> 14σx ~ 7.7mm

Countermeasures

Y. Suetsugu• For the upgrade of the vacuum system forSuperKEKB, the electron cloud is a key issue.
Countermeasures are carefully chosen based on thevarious studies.

Drift section

Antechamber +Solenoid +TiN Coating

Q and Sx mag.

Antechamber +Solenoid +TiN Coating

Bend section

Antechamber +Groove+ TiN Coating

Wiggler section

Antechamber +Electrode (Cu)41

Countermeasures for electron clouds
GrooveDri_ secEon: Antechamber + TiN coaEng
Inside view

Wiggler secEon:
Antechamber + Clearing electrode
Electrode

Y. Suetsugu