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BEPCII OverviewBEPCII OverviewC. Zhang for BEPC TeamC. Zhang for BEPC Team

Institute of High Energy Physics, CAS Institute of High Energy Physics, CAS October 13, 2001, BESIII Workshop

IntroductionIntroduction Basic DesignBasic Design Key TechnologiesKey Technologies SummarySummary

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(1) Introduction(1) Introduction

A brief description on BEPCA brief description on BEPC

Main parametersMain parameters

Operation and performanceOperation and performance

From BEPCI to BEPCIIFrom BEPCI to BEPCII

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1.1 A Brief Description on 1.1 A Brief Description on BEPCBEPC

The Beijing Electron-Positron Collider (BEPC) was constructed (1984-1988) for both high energy physics and synchrotron radiation research.

The machine has been well operated for 12 years since it was put into operation in 1989.

The BEPC accelerator system consists of a 202-meter long linac injector, a 210-meter long beam transport line and a 204.4-meter circumference storage ring.

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The Beijing-Electron Positron Collider The Beijing-Electron Positron Collider (BEPC)(BEPC)

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The Layout of BEPC storage ringThe Layout of BEPC storage ring

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1.2 Main Parameters1.2 Main ParametersBeam Energy (E) 1.0 ~ 2.5 GeV

Revolution frequency (fr) 1.247 MHz

Lattice Type FODO + Low- Insertions

*x -function at IP (*

x/ *y) 1.3/0.05 m

Transverse Tune (x/y) 5.8/6.8 (Col. Mode) 8.72/4.75 (SR Mode)

Natural Energy Spread (e) 2.64E 10-4

Momentum Com. Factor (p) 0.042 (Col. Mode) 0.016 (SR Mode)

Hor. Natural Emittance (x0) 0.4@1.55 GeV, 0.076@2.2GeV(SR) mmmr

RF Frequency (frf) 199.533 MHz

Harmonic Number (h) 160

RF Voltage (Vrf) 0.6~1.6 MV

Bunch Number (Nb) 1*1 (Col.), 60~80 (SR)

Maximum Beam Current 50mA@1.55 GeV (Col.,) 130mA (SR)

Luminosity 5 1030 cm-2 s-1 @1.55 GeV, 11031 cm-2 s-1 @2 GeV

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4%

Injection12%

MD10%

BES42%

BSRF26%

Fault6%

1.3 Operation and Performance1.3 Operation and Performance

Start-up

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Daily Daily J/J/ operation of BEPC operation of BEPC Period Days Beam time (hrs.) J/events Lmax(1030cm-2 s-1) (hrs) 99-00 142 2323 24 M 4 8-10 00-01 110 1900 22 M 5 8-10

0

10

20

30

40

50

60

0 500 1000 1500Time (min.)

Be

am

Cu

rre

nt

(mA

)

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1.4 From BEPCI to BEPCII1.4 From BEPCI to BEPCII The physics opportunity of BEPC calls h

igher luminosity BEPCII

To collect some 109 J/ events and 108 ′events in 4 years;

Light hadron spectroscopy, charmed mesons and at the thresholds;

Hadron production mechanism, low energy QCD;

Precision R values, ambiguous’ structures in 3.8-4.4 GeV;

Searches: 1P1, c’, glueball, hybrids, exotic states;

New physics: probing rare decay, LFV and CP violation from the decays of J/ and (2S);

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(2) The Basic Design(2) The Basic Design

Strategy of Luminosity UpgradesStrategy of Luminosity Upgrades

The The double ring structuredouble ring structure

Design Goals and Main ParametersDesign Goals and Main Parameters

TheThe Lattice and Dynamic ApertureLattice and Dynamic Aperture

The Collective EffectsThe Collective Effects

Beam Lifetime & Average LuminosityBeam Lifetime & Average Luminosity

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2.1 Strategy of luminosity upgrades2.1 Strategy of luminosity upgrades

)(

)()()1(1017.2)s(cm

*341-2-

cm

AIkGeVERL

y

bby

Micro-:y*=5cm 1~1.5 cm

SC insertion quadsReduce impedance +SC RF

z=5cm ~1cm

DR: multy-bunch kbmax~400, kb=1 93

(LBEPCII/ LBEPCI) D.R.=(5/1.5) 93 12/20=186

Choose large x & optimum param.: Ib=12mA, y=0.04

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BEPCIBEPCI:: IIbb=20 mA, =20 mA, yy=5cm, k=5cm, kbb=1,=1,

LL=5=510103030cmcm-2-2 s s-1 -1 @1.55GeV (1 @1.55GeV (1 10103131cmcm-2-2 s s-1 -1 @2GeV )@2GeV )

BEPCII=BEPCI+micro-BEPCII=BEPCI+micro-+ Multibunch + Multibunch + Better SR performance+ Better SR performance

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2.2 The double ring Structure2.2 The double ring Structure

e -

RFRF SR

e+

IP

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A large amount of excellent professional work has been accomplished leading to the Feasibility Study Report on BEPC II. As now proposed, BEPC II can be constructed either in a single ring or two-ring version, differing in expected performance and cost.

The committee is pleased that the luminosity goal of the BEPC II has been raised from the early proposed gain by a factor of ten to the single ring goal of 3-41032 cm-2sec-1 or the double ring goal of 11033cm-2sec-1. The committee considers these raised goals to be technically feasible and recommends the most aggressive approach consistent with the resources that can be made available. This implies a strong preference for the two-ring option.

The scientific environment in which BEPC II will have to operate has changed considerably from that in which BEPC I has a monopoly in this energy range. The now operating B-factories will accumulate extensive data, however with generally higher background, in this energy range and the recent decision by the Cornell University Laboratory of Nuclear Studies to move the operating range of its CESR collider into the tau-charm range to operate at a luminosity of about 31032 cm-2 sec-1 has major implications for the future of Chinese high energy physics. While the latter move attests to the continuing scientific importance of this field of inquiry, it should be noted that the CESR program in this energy range will commence several years sooner than is feasible for BEPC II.

The committee judges that the double ring design implies a lower risk in attaining its design luminosity in a brief commissioning time than does the single ring “pretzel” design.

From the Report of International Review on BEPCII Feasibility Study

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Model test of the double ring installationModel test of the double ring installation

No unsolvable problems are found for the No unsolvable problems are found for the transportation, installation, mounting and transportation, installation, mounting and dismount of the magnets.dismount of the magnets.The existing monuments for survey and The existing monuments for survey and alignment will be covered by the inner ring alignment will be covered by the inner ring magnets. magnets. New monuments will be fixed on New monuments will be fixed on the wall of the tunnel.the wall of the tunnel.The antechamber of the positron ring needs The antechamber of the positron ring needs to be carefully designed to fit the crucial to be carefully designed to fit the crucial space between two rings;space between two rings;The cable system, the cooling-waterThe cable system, the cooling-watersystem, system, the pressure-air systemthe pressure-air system and others need to  and others need to be rearrangedbe rearranged.

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2.4 Design Goals and Main Parameters2.4 Design Goals and Main Parameters

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Main Parameters of the BEPCII Storage RingMain Parameters of the BEPCII Storage Ring

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2.4 The lattice and dynamic aperture 2.4 The lattice and dynamic aperture (G.Xu)(G.Xu)

-15 -10 -5 5 10 15

65.2

65.4

65.6

65.8

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2.5 Collective Effects2.5 Collective Effects

2.5.1 Bunch Lengthening2.5.1 Bunch Lengthening

VVrfrf=1.5MV, =1.5MV, |Z/n||Z/n|effeff=0.23=0.23, , IIth th = 21.4mA = 21.4mA zz~ ~ z0z0=1.1cm=1.1cm

|Z/n||Z/n|00=4=4 0.2 0.2

MAFIA computation & measurementMAFIA computation & measurement

Bellows, kickers, separators, BPM’s, masks, connectBellows, kickers, separators, BPM’s, masks, connectors, valves, pumps, SR ports, IR ors, valves, pumps, SR ports, IR

BBs

bpl n

Z

E

RIec20

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2

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2.5.2 Coupled Bunch Instabilities2.5.2 Coupled Bunch Instabilities Beam cavity interaction (Nb=99, Ib=12 mA, using KEKB SC cavities)

Resistive wall instabilityx/y = 6.58/7.64, Nb = 99, Ib = 12mA, = 16.4ms;

Ion effects

Photo-electron cloud instability:

Use antechamber for positron ring

Bunch feedback

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2.2.3 Beam-beam effects2.2.3 Beam-beam effects

Head-on beam-beam effect: similar to BEPCIHead-on beam-beam effect: similar to BEPCI =0.04 has been demonstrated=0.04 has been demonstrated

Parasitic beam-beam effectParasitic beam-beam effect

xx10 10 x x andand cc=5.5=5.52 mrad2 mrad

Horizontal crossing angle Horizontal crossing angle cc

((5.5-11)5.5-11)2 mrad2 mrad (BEPCII)(BEPCII), , 2.32.32 mrad2 mrad (CESR)(CESR)

11112 mrad2 mrad (KEKB)(KEKB), 12.5 , 12.5 2 mrad2 mrad (DA(DANE)NE)

Crossing angle+Parasitic collisions (Arcs & IR) Crossing angle+Parasitic collisions (Arcs & IR) More sophisticated simulation study.More sophisticated simulation study.

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2.2.4 Beam Lifetime and Average Luminosity2.2.4 Beam Lifetime and Average Luminosity

Taking =1.35 hrs., tf= 0.4 hr. and L0=11033 cm -2s-1, the optimized collision time is calculated as 1.0 hrs. and the maximum average luminosity is calculated as Lmax=0.51033 cm-2s-1. The top-off injection will further improve the average luminosity.

fc

t

Lfc

t

tt

eL

tt

dttLL

Lcc

/

00 1)(

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(3) Key Technologies(3) Key Technologies Injector upgrading 500 MHz SC RF System SC Micro- Quads and IR Low Impedance Kickers Vacuum System Power Supply System Instrumentation Upgrade Control Upgrade

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3.1 Injector upgrading3.1 Injector upgrading Basic requirement: Higher intensity: positron injection rate 50 mA/min.; Full energy injection with E=1.55 ~ 1.89 GeV;

To enhance the current and energy of the electron beam bombarding the target and to reduce the beam spot;

To design and produce a new positron source and to improve its focusing;

To increase the repetition rate from present 12.5 Hz to 50 Hz.

To consider multi-bunch injection (fRF/fLinac=7/40);

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3.2 500 MHz SC RF System3.2 500 MHz SC RF System

Basic requirement Sufficient RF voltage for short bunches. Sufficient high RF power. Suppressing the instabilities related to RF system. Stable and reliable RF system

Strategy: to take advantage of collaboration with SSRF, Cornell and KEK and to apply the existing industrial technology.

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Options of 500 MHz SC RF Cavity Options of 500 MHz SC RF Cavity CESR-type Cavity (ACCEL) KEKB-type Cavity (Mitsubishi )

IHEP RF group will work at optimization of the cavity design, trace the manufacture and be trained to maintain the SC RF system.

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3.3 SC Micro-3.3 SC Micro- Quads and IRQuads and IR

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The SC magnets and IR DesignThe SC magnets and IR Design

Space and dimension Installation and alignment Solenoid and its compensation Magnet leakage field Background and masking Cryogenics ……

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3.4 Low Impedance Kickers3.4 Low Impedance Kickers The study has shown that the kickers are one of

major sources of impedance, where single turn air coils are located inside vacuum chamber of the kickers.

The new kickers of BEPCII impose the ferrite magnet outside the vacuum with ceramic beam pipes so that the impedance problem is avoided.

The pipes are with resistive coating on its inner surface. Magnetic field distribution in the kicker

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3.5 Vacuum System3.5 Vacuum System

The BEPCII poses two challenges to the vacuum system, one is vacuum pressure, other is the impedance. The dynamic vacuum at a high beam current should satisfy the requirements of sufficient beam lifetime, low background in the detector. The design vacuum pressure is 510-9 Torr in the arc and 510-10 Torr in the IR. To reduce the impedance, the vacuum chamber should be as smooth as possible. Some of the chamber structures will be shielded, some will be replaced with new designed components.

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3.6 Power Supply System3.6 Power Supply System The superconducting insertion quadruple magnets for micro- need to be powered with new power supplies. The pretzel scheme need more independent power supplies, namely 34 for quadruples and 18 for sextupoles. In the double-ring case, this numbers are about doubled. In order to mount the additional power supplies in the existing rooms, the new power supplies should be compact by using improved technology.

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3.7 Instrumentation Upgrade3.7 Instrumentation Upgrade Beam Position Monitor Bunch Current Monitor Beam Feedback System

Synchrotron Light Monitor

IP beam position control

Beam

Fr ont - EndEl ect r oni cs

PowerAmp.

ADC DAC

Ti mi ng Cont r olMu

ltip

lexe

r

Farm

of

DSPs

Demu

ltip

lexe

r

Modul at or

Ki ckerOsci l at or

500MHz. RFMast er Osc.

Pi ckup Par t Ki cker Par tSi gnal Pr ocessi ng Par t

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3.8 Control System: switch from BEPCI to BEPCII

VAX 4500

CAMAC

PC subsystems

WS console

Ethernet

PS, Vacuum, RF

InjectionBeam diagnosticLinac

Server WS PC

SwitchEthernet LAN

instrument

instrumentremote I/O

remote I/OPLC

PL

C L

ink

Fie

ldb

us

GP

IB

remote I/O

remote I/O

Fie

ldb

us

VME

CAMAC

CAMAC

PC Computers

PLC

PC

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Collaboration on Collaboration on BEPCII Accelerators BEPCII Accelerators

Linac: SLAC, KEK, INFN

SC Micro- quadruples: BNL, KEK

SC RF cavities: Cornell, KEK

Impedance study: LBNL

Beam Instrumentation: CERN, SLAC

Under discussion: BINP and other labs

Domestic institutions: SSRF, Tsinghua, PU

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Budget and Schedule The budget of the BEPCII project is estimated as about 600 million RMB for both accelerators and detector.

The project is expected to finish in 34 years after its approval.

0 310 620 930 1240 1550 1860

12月 6月 12月 6月 12月 6月 12月 6月 12月 6月 12月

2001 2002 2003 2004 2005 2006

工程周 26 52 78 104 130 156 182 208 234 260 286

进度标尺 0 310 620 930 1240 1550 1860

序号 工作名称 持续时间 开始时间 结束时间

1 初步设计 203 2001-09-10 2002-04-01

2 原型样机研制 659 2001-09-10 2003-07-01

3 BEPC运行 964 2001-09-10 2004-05-01

4 开工报告 61 2002-04-01 2002-06-01

5 扩初设计 378 2002-04-01 2003-04-14

6 设备加工制造 1035 2002-06-01 2005-04-01

7 直线安装、谱仪撤出184 2004-05-01 2004-11-01

8 直线调束 61 2004-11-01 2005-01-01

9 同步运行 85 2005-01-01 2005-03-27

10 储存环设备安装 275 2005-04-01 2006-01-01

11 储存环调束 151 2006-01-01 2006-06-01

12 谱仪安装 92 2006-06-01 2006-09-01

13 储存环调束 122 2006-09-01 2007-01-01

网络图说明

梦龙软件制作 2001-09-12

结束时间

起始时间

2006-12-31

2001-09-10

校对人

审核人

绘图人

项目负责人

备注：

文件名

总工期 1939天

BEPCII零级CPM计划

原型样机研制659

BEPC运行964

初步设计203

开工报告61

扩初设计378

储存环设备安装275

储存环调束151

谱仪安装92

储存环调束122

直线安装、谱仪撤出184

直线调束61

同步运行85

设备加工制造1035

1 2 3

4 5 6

7 8 9 10 11

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(4) Summary(4) Summary BEPC has been well operated with many exciting HEBEPC has been well operated with many exciting HEP and SR results for 12 years since it was put into opeP and SR results for 12 years since it was put into operation in 1989.ration in 1989.

BEPCII is proposed as micro-BEPCII is proposed as micro- plus multibunches wi plus multibunches with two rings and its design luminosity is order of magth two rings and its design luminosity is order of magnitude higher than present BEPC in energy range of nitude higher than present BEPC in energy range of J/J/ and and ’. ’.

Some key technologies need to be developed to achieSome key technologies need to be developed to achieve the goal of BEPC II.ve the goal of BEPC II.

The international collaboration and contribution will The international collaboration and contribution will be promoted in order to accomplish this challenging abe promoted in order to accomplish this challenging and exciting project on schedule and budget. nd exciting project on schedule and budget.

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Thank You for Thank You for Attention!Attention!

Thank You for Thank You for Attention!Attention!