The SuperKEKB Accelerator :Construction and Operations
2018/12/13
M. Iwasaki (Osaka City Univ. & RCNP, Osaka Univ.)

April 26, 2018
Belle II control room

First collisions
on April 26, 2018

First hadronic event

First collisions
on April 26, 2018
OCU Advisor to the President(H. Suzuki)

SuperKEKB First Collisions Ceremony(June 26, 2018 @ KEK)

Today I’ll talk
1. SuperKEKB / Belle II introduction- Motivation of the experiment- SuperKEKB upgrade strategy
2. SuperKEKB construction
3. SuperKEKB operations
4. Activities at OCU for SuperKEKB
5. Summary

Introduction
SuperKEKB / Belle II experiment“Luminosity frontier experiment”
Low energy experiment indirectly probinghigh energy using high statistics data- KEKB/Belle has upgraded to SuperKEKB/Belle II- Luminosity of the SuperKEKB accelerator
x40 of the KEKB’s world record
to accumulate high statistics of 50ab-1 data
→Probe > O(TeV) energy scale
5Introduction
Belle detectorBelle

1km diameter

KEKB at KEK

8GeV (e-)  3.5GeV (e+)

KEKB / Belle has upgraded toSuperKEKB / Belle II

Asymmetric Energy e+ e- collider
6Mt. Tsukuba

KEKB

Belle1kmKEKLinac
2012.11.8

B workshop @ Hanamaki

7

KEKB to SuperKEKB
SuperKEKB1036

40 times higherluminosity

KEKB

Next generation
B-factories

Strategies for increasing Luminosity
Three Key factors for a factor of ~40 gain
Beam-beam parameter
Beam current

Vertical beta function @ IP
(1) Smaller by*(2) Increase beam currents(3) Increase xy“Nano-Beam” scheme
First proposed by P.Raimondi for SuperB

Collision with very small spot-size beams

Nano-Beam scheme

If we squeezing the beams at IP,
particles in the bunch-tails experiencea much higher b*y and loss L→b*y should be around the size ofthe beam overlap (~bunch length)

Vertical beam size (relative value)

To increase L, we want to squeeze beams (=small b*y )However β*y cannot be much smaller than the bunch length
to avoid the “hourglass” effectHourglass effectβy* = 1/20 σz
Too smallβ y * = σz
The best size

Too large

βy* = 2σzIPNano-Beam scheme
To overcome the “hourglass” effect,Enlarge crossing angle & Make horizontal beam size small
Two colliding beams overlap region becomesmuch smaller than the bunch lengthIntersect bunches only at highly focused region
Head-on collision

Nano-beam scheme

Lssoverlap region = bunch length

overlap region ~L

Hourglass condition: βy*> ~σs

Hourglass condition: βy*> ~LNano-Beam scheme
In the nano-beam scheme, we1) Enlarge the crossing angle, and2) Make the horizontal beam size small
Make b*y small to increase the luminosity
Small size horizontal beam → Small b*x and small ex
Head-on collision

Nano-beam schemeLssoverlap region = bunch length

overlap region ~LHourglass condition: βy*> ~σs

Hourglass condition: βy*> ~LMachine Design Parameters
KEKBparameters

SuperKEKB

LER

HER

LER

HER

3.5

847units

Beam energy

Eb

Half crossing angle

φHorizontal emittance

εx18

24

3.2

4.6

nmEmittance ratio

κ0.88

0.66

0.27

0.25%

Beta functions at IP

βx*/βy*32/0.27

25/0.30mm

Beam currents

Ib

1.64

1.19

3.6

2.6

A

beam-beam parameterξy0.129

0.090

0.088

0.081

Luminosity

L1141.5

1200/5.9

2.1 x 1034

GeVmrad8 x 1035

cm-2s-1• Small beam size & high current to increase luminosity• Large crossing angle• Change beam energies to solve the problem on LER short lifetimeKEKB to SuperKEKB How to upgrade
Belle2New IR
Colliding bunches

New beam pipe
& bellows
7 GeV
Positron Beam

4 GeV
Positron
Beam

Replace short dipoles
with longer ones (LER)

Add / modify
the RF system

Redesign the lattices of HER &LER to squeeze the emittanceTiN-coated beam pipewith antechambers

New Positron
Damping Ring

New positronsourceNew Lowemittance gun

To get x40 higher luminosity

K. AkaiSuperKEKB Master Schedule
・・・ JFY2010

JFY2011

JFY2012

JFY2013

JFY2014

JFY2015

JFY2016

JFY2017

・・・

JFY2018

KEKBOperation
Dismantle
KEKB

SuperKEKB construction
Startup,Conditioning,etc

3 step operations
Phase-1 For machine studies (w/o Belle, w/o QCS)
Phase-2 Experiments w/o Vertex Detector
Phase-3 Experiments with full detector

BelleII Upgrade

For about 10 years

SuperKEKB
Operation
Phase 1

Phase 2

QCS install
Belle2 roll inPhase 3

SuperKEKB Luminosity Projection
Y. Ohnishi

We are here

Milestone of SuperKEKB

9 months/year
20 days/monthCalendar Year

SuperKEKB
Construction
17

New Positron Damping Ring
RTL Line±2.7mm

1.1 GeVΔp/p

DR±2%Z (m)(BCS)

Bunch Comp.
SystemPositron
Target(ECS)DR → Linac →SuperKEKB

Energy Compression System

Collimators in the arc
20% is cut at tailDesignDRInjection

Extraction

gex(mm)

2800

89.3

64.6 (estimated)gey(mm)2600

4.5< 2.0±0.36 (measured)

N. Iida, M. Kikuchi et al.

Linac → DR

±5%

New SC magnets around IP (QCS)
Assembly of the QC1LP, QC2LP, QC1LE, correctors and QC1LP leak field cancel magnets
N. Ohuchi(Front cold mass of QCSL)
QC1LE
a1, b1, a2, b4 correctors

Magnetic shield

QC1LP leak field cancel magnets

QC2LP
a1, b1, a2, b4 correctors
Magnetic shieldb4 corrector

QC1LP
a1, b1, a2 correctors

2018/05/01

IPAC'18

19

New SC magnets around IP (QCS)• Compensation solenoids [ESL, ESR1, ESR2-3]

N. Ohuchi

ESR2-3 compensation solenoid

ESL compensation solenoid

ESR1 compensation solenoid

Magnet length= 914 mm
Maximum field at 404 A= 3.53 T
Stored Energy= 118 kJ
2018/05/01

IPAC'18

Magnet length= 1575 mm
Maximum field at 450 A=3.19 T
Stored Energy= 244 kJ
Cold diode quench protection system
20

QCS cryostats in SuperKEKB IR
N. Ohuchi

Belle II detector
before Roll-in.

QCSL was installed
in 2016
QCSR was installed
in 2017.

20170321
2018/03/22

物理学会シンポジューム（東京理科大学野田）21
From the presentation by Prof. K. AKAI @KEKB review at Mar. 14, 2018

SuperKEKBOperation
22

History of Commissioning
Y. Funakoshi
Y. Ohnishi

Beam dose: 120 Ah in LER / 114 Ah in HER
Max. beam current: >400 mA in LER / >300 mA in HER

March 19 Phase 2 commissioning started.
April 25 First Beam-Beam deflection was observed.
April 26. First Collision (Physics event) was observed.

23

History of Commissioning
Y. Funakoshi Y. OhnishiMax. IHER = 800 mA

Max. ILER = 860 mA

Lpeak = 5.55 x 1033 cm-2s-1

Integrated Luminosity (delivered from SuperKEKB) = 1853 pb-1
24

βy* Evolution over 50 Years
SuperKEKB will try to make the smallest βy* in the world !

Y. Ohnishi

PEP
SPEAR

VEPP-2000
LEP, BEPCPETRATRISTAN CESR-C BEPC-II
PEP-IICESR
DAFNE
KEKBmm-world
SuperKEKB
Phase 3μm-world

Phase 2.0(LER)

Phase 2

FCC-eeCEPCFinal designYear25

Beta Squeezing at IP
Y. Ohnishi

β*y = 2mm trial (single beam)

26

Verification of N a n o - B e a m Scheme
Y. Ohnishi

Emittance
is improved
XY coupling at IP
is corrected by QCS

βy* < σzβy* = σz

βy* > σz27

Luminosity
Y. Funakoshi Y. Ohnishi

5.55 x 1033/cm2/s(by*3mm, LER: 800mA, HER: 780mA)

by*= 80mm

by*= 8mm

4/1/2018

5/16mm6/1

by*= 4mm

7/1

by*= 3mm28QCS Quench
Y. Ohnishi

Stable Operation

29

Damage of Movable Collimator HeadLER
D02V1

Damaged during collisions

HER
D01V1
D01V1

D02V1

Damaged during current storage (w/o collisions)Y. Suetsugu, T. Ishibashi, S. Terui
30

Activities at OCU
for the SuperKEKB
Accelerator
31

Injector Linac Operation
Tuning using MLBelleII
1km diameter

Injector
Linac

To achieve the high luminosity,
precise operation tuning to get
the higher injection efficiency
is very important

Currently R&D of operation tuning
for the injector Linac
using Machine Learning (ML)is ongoing
KEK, Osaka-City U., IDS Osaka U.
32

In Osaka, we form a group working on“Application of Deep Learning
for Accelerator Experiments”→ Approved as a RCNP project
The group is formed with particle physicists and data scientists

Particle
Physics

DataScienceML applications in our project• Flavor-tag in ILC & continuum rej. in Belle(Osaka-City U., IDS, RCNP)• Pattern recognition in medical (Showa P. U.)• Beam size measurement in ILC (Tohoku U.)• EM calorimeter calibration in ILC SiD(Osaka-City U., U. Oregon, PNNL, SLAC)• Accelerator operation tuning in KEK Linac(KEK, Osaka-City U., IDS)
34

Online Data for the ML study
Injector Linac is for SuperKEKB, PF and PF-AR

We can accumulate online data
even SuperKEKB is not running35

Summary- KEKB has upgraded to SuperKEKB
First collisions in April 2018
Peak luminosity 5.5x1033/cm2 /sec
- At OCU, R&D of the operation tuning
for the injector Linac using ML is on going
Collaboration : KEK, OCU, and IDS Osaka U.

New physics commissioning (phase-3)
will start from 2019!