Institute of High Energy Physics Chinese Academy of Sciences Welcome EPICS'02 2002 EPICS Seminar Institute of High Energy Physics Chinese Academy of Sciences 20-22 August, 2002

Introduction to BEPCII EPICS Seminar 2002 （August 20, 2002, IHEP） From BEPC to BEPCII Basic Design Key Technologies Budget and schedule Summary

(1) From BEPC to BEPCII Status of the BEPC Why BEPCII What is BEPCII

1.1 The Status of the BEPC

The Layout of BEPC storage ring

Main Parameters Beam Energy (E) 1.0 ~ 2.5 GeV Revolution frequency (fr) 1.247 MHz Lattice Type FODO + Low-b 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) mmmr 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, 11031 cm-2 s-1 @1.89GeV

Statistics of 00-01 Operation Fault Start-up Injection 6% 4% 12% BSRF MD 26% 10% BES 42%

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

Physics results from BEPC/BES

BSRF dedicated operation 70 days with three times for about 300 users every year Imax=140 mA, ex0=76 nm, t=20~30 hrs., Ninj=2

Synchrotron radiation application with BSRF

2.1 Why BEPCII BEPC/BESI collected 9 106 J/y events in about two years; Upgraded BEPC/BESII obtained 5107 J/y events in two years; BEPC/BESI collected 4 106 y events; BEPC /BESII operated for y from Nov. 23, 2001 to March 13, 2002; With 1 106 a week, 1.4107 y was collected in 100 days; Nice physics results are expected; For our physics goal, 6 109 J/y 2109 y per year are expected  BEPCII/BESIII!

1.3 Luminosity Strategy of the BEPCII Multy-bunch kbmax~400, kb=1  93 Choose large ex & optimum param.: Ib=9.75mA, xy=0.04 Micro-b:by* =5cm  1.5 cm SC insertion quads Reduce impedance +SC RF sz =5cm  <1.5cm (LBEPCII/ LBEPC) D.R.=(5.5/1.5) 93  9.8/35=96 LBEPC=1.010 31 cm-2s-1  LBEPCII =110 33 cm-2s-1

(2) The Basic Design The double ring structure of BEPCII Design Goals and Main Parameters Lattice and Dynamic Aperture Beam Collective Effects Beam Lifetime & Average Luminosity

2.1 The double ring structure of BEPCII

Mock-up of the double ring installation There is no showstopper for the transportation, installation, mounting and dismount of the magnets. The existing monuments for survey and alignment will be covered by the inner ring magnets. New monuments will be fixed on the wall of the tunnel. The antechamber of the positron ring needs to be carefully designed to fit the crucial space between two rings; The cable system, the cooling-water system, the pressure-air system and others need to be rearranged.

Magnet girder and pre-alignment

2.2 Design Goals and Main Parameters

Main Parameters

2.3 Lattice and Dynamic Aperture

2.4 Single beam collective effects Bunch length and impedance Vrf = 1.5MV, Z/n|eff0.2, Ith = 37mA  Ib = 9.8mA, l ~ 1.3 cm Beam-cavity interaction (with KEKB SC cavities) Resistive wall x/y = 6.6/7.6, Nb = 99, Ib = 9.8mA,  = 4.3ms; Ion effects Electron cloud instability: Antechamber with TiN coating for e+ ring Bunch feedback：tL=5 ms, tT =2 ms  Single beam instabilities can be damped !

2.5 Beam-beam effects Head-on beam-beam effect: similar to BEPC  x=0.04 has been demonstrated Parasitic beam-beam effect  c=112 mrad Horizontal crossing angle c  (5.5-11)2 mrad (BEPCII), 2.32 mrad (CESR) 112 mrad (KEKB), 12.5 2 mrad (DAFNE) Beam-beam simulation for BEPCII with BBC code has shown that the beam-beam parameters and crossing angle of 11 mrad are acceptable.

2.5 Beam Lifetime and Average Luminosity Taking t =1.35 hrs., tf= 0.4 hr. and L0=11033 cm -2s-1, the optimized collision time is calculated as 1.0 hrs. and the maximum average luminosity is calculated as Lmax~ 0.51033 cm-2s-1. The top-off injection will further improve the average luminosity.

(3) Key Technologies Injector Upgrades 500 MHz SC RF System SC Micro-b Quads and IR Magnet System Power Supply System Injection Kickers Vacuum System Instrumentation and Feedback Control Upgrade

BEPCII will apply state of art technologies

3.1 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);

The measures to increase positron intensity

BEPCII Positron Source

3.2 500 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

RF Cavity in BEPCII Tunnel

3.3 SC Micro-b Quads and IR

3.4 Magnets System New arc magnets

Two-in-one Quadrupole IQ1

Septum Bending magnet ISPB Magnetic length 0.6m Magnetic Field 0.4 T Theckness 10mm Aperture 11078mm2 Current 2100 A Current density 52.7 A/mm2

(5) Power Supplies System

3.6 Vacuum System Vacuum pressure The BEPCII poses two challenges to the vacuum system, one is vacuum pressure （Arcs: 810-9Torr， IR: 510-10Torr）, other is the impedance. Vacuum pressure Electron Ring Positron Ring

Vacuum Chamber Design

3.6 Injection Kickers

3.7 Instrumentation and Feedback Beam Position Monitor Bunch Current Monitor Beam Feedback System Synchrotron Light Monitor IP beam position control ……

3.8 Control System BEPC BEPCII  WS console Ethernet PC subsystems VAX 4500 Injection Beam diagnostic Linac CAMAC PS, Vacuum, RF BEPCII 

(4) Budget and Schedule The budget of BEPCII project is estimated as 640 MRMB. It is scheduled to finish in 4 years.

(5) Summary BEPC has been well operated with many exciting HEP and SR results for 13 years since it was put into operation in 1989. BEPCII is proposed as micro-b plus multibunches with two rings and its design luminosity is order of magnitude higher than present BEPC in energy range of J/y, y  and y. Some key technologies need to be developed to achieve the goal of BEPC II. The international collaboration will be promoted in order to accomplish this challenging and exciting project on schedule and budget.

May the EPICS’02 be a Great Success !