1. 1 Weiguo Li Institute of High Energy Physics Sep. 16, 2002 Overview of BEPCII/BESIII PROJECT BESIII International Review Sep. 16-18, 2002, Beijing

2. 2 Goals of the BESIII review Examine the overall design of BESIII detector, if this design can accomplish the goals? Examine the technical feasibility of detector overall design, the designs of all the sub-systems Suggestions and opinions for important detector design choices, such as the magnet and the EMC Suggestions and comments for further detector design, R&D, detector manufacture, schedule and cost

3. 3  Introduction  BEPCII Design  BESIII Design  BESIII Collaboration  Summary

4. 4 Korea (4) Korea University Seoul National University Chonbuk National University Gyeongsang Nat. Univ. Japan (5) Nikow University Tokyo Institute of Technology Miyazaki University KEK U. Tokyo USA (4) University of Hawaii University of Texas at Dallas Colorado State University Stanford Linear Accelerator Center UK (1) Queen Mary University China (18) IHEP of CAS Univ. of Sci. and Tech. of China Shandong Univ., Zhejiang Univ. Huazhong Normal Univ. Shanghai Jiaotong Univ. Peking Univ., CCAST Wuhan Univ., Nankai Univ. Henan Normal Univ. Hunan Univ., Liaoning Univ. Tsinghua Univ., Sichuan Univ. Guangxi Univ., Guangxi Normal Univ. Jiangsu Normal Univ. Introduction

5. 5 Data Collected with BESI and BESII BES Current Status

6. 6 BESII Detector ( 1995-1997 upgrade ) VC:  xy = 100  m TOF:  T = 180 ps  counter:  r  = 3 cm MDC:  xy = 250  m BSC:  E/  E= 22 %  z = 5.5 cm  dE/dx = 8.4 %   = 7.9 mr B field: 0.4 T  p/p=1.8  (1+p 2 )  z = 2.3 cm Dead time/event: 〈 10 ms

7. 7 BES BES Main Physics Results  Precise Mass Measurement of  lepton.  2-5 GeV R measurement.  Systematic study of  (2s) decays.  Systematic study of J/  decays.  Obtain f Ds from Ds pure leptonic decay.  Measure Br(D S   ) in model independent way.  BES has 116 entries in PDG.  BES has 74 invited talk ， published 216 papers, 48 papers in world-class journals.

8. 8 Physics Window for BEPC Two major directions in world HEP: – High Energy Frontier ： Search for Higgs particle and beyond STM particles and phenomena. – High precision frontier ： high statistics and high precision ， check STM ， search for phenomena beyond STM. Considering the new developments of world HEP, the main physics window for BEPC is precise measurement of charm and charmonium physics, and search for new phenomena. Advantages: huge cross section at J/  and  (2s) resonance simple topology and low background at threshold Important area to study QCD ， perturbative and non-perturbative QCD ， can search for new physics.

9. 9 BEPC II Physic Goals Precise measurements of J/  、  (2s) 、  (3770 ） Decays Precise measurement of CKM parameters Light quark hadron spectroscopy Excited baryon spectroscopy Other D and Ds physics: –precise measurement of D and Ds decays – measurement of f D, f Ds –D 0 –  D 0 mixing Check VDM, NRQCD, PQCD, study  puzzle

10. 10 BEPC II Physics Goals （ 2 ） Mechanism of hadron production ， low energy QCD ： precise R measurement  physics ： charged current ， m  and m  Search for new particles: 1 P 1 、  c ? 、 glueballs 、 quark-gluon hybrid 、 exotic states… Search for new phenomena: – rare decays; – lepton number violation; – CP violation in J/  and  (2s) decays;

11. 11 BEPC Future Development: BEPCII Precise measurements need: – High statistics → high luminosity machine – Small systematic error→ high performance detector BEPC will run at J/  and  (2s) ， with huge cross-section, also at  (3770), 4.03 or 4.14 GeV for Ds Need to have major upgrade for machine and detector (BEPCII / BESIII) ， to increase machine luminosity by more than one order of magnitude with relatively small budget and in a relatively short time.

12. 12 Competition in tau-charm physics CESR, USA runs at 10GeV for B physics, because it can hardly compete with two B factories ， on the other hand, there are important and interesting physics at tau-charm energy region as demonstrated at BEPC, plans to reduce the collision energy by installing a series of SC wigglers, expected lum. （ 1.5 – 3)x10 32 cm -2 s -1 。 VEPP-4M, Novosibirsk, Russia, has a similar plan. BEPC/BES can not enjoy the advantage of unique e+e- collider in this energy region any more ， strong competition. BEPC II single ring design can not ensure competitive edge in the race.

13. 13 BEPC II Double ring Design In the existing BEPC tunnel, add another ring, cross over at south and north points, two equal rings for electrons and positrons. Advanced double-ring collision technology. 93 bunches ， total current > 0.9A in each ring. Collision spacing ： 8 ns. In south, collision with large cross-angle （ ±11 mr ）. Calculated luminosity ： 10 33 cm -2 s -1 @ 3.78GeV. In north cross point, connecting SR beam between two outer rings, in south cross point, use dipole magnet to bend the beam back to outer ring. SR run ： 250mA @ 2.5 GeV. Major detector upgrade ： BES III. Luminosity of BEPCII is a factor of 3-7 of that of CESRc, more potential, and technically less challenge. Budget increased by 50 ％.

14. 14 BEPC Upgrade: BEPC II — double ring e - RF SR e + IP

15. 15 BEPCII Design Goals Increase beam current ， reduce beam size

16. 16 Wood Model Space Study for Double Ring

17. 17 Luminosity Increase Micro-  :  y *  =5cm  1.5 cm Super-conducting magnet Impedance red. and SC RF cavity  z  =5cm  <1.5cm D.R.: multi bunches h~400, k b =1  93 (L BEPCII / L BEPC ) D.R. =(5.5/1.5)  93  9.8/35=96 L BEPC =1.0  10 31 cm -2 s -1  L BEPCII =1  10 33 cm -2 s -1 I b =9.8mA,  y =0.04

18. 18 Means of lum. increase (E = 1.89 GeV) parameterunit BEPC BEPCII  y * cm5.0 ～ 1.5 Bunch number k b 193  y 0.04 Beam current I b mA359.8 factor for lum. increase 1 ～ 100 BEPCII cross-angle collision ： 2 x 11mr

19. 19 BEPCII Main Parameters Energy E(GeV)1.89Energy spread(10 -4 ) σ e 5.16 Circumference C(m)237.53Emittance ε x /ε y (nm)144/2.2 Harmonic number h396Momentum compact α p 0.0235 RF frequency f rf (MHz)499.8β * x /β * y (m)1/0.015 RF Voltage V rf (MV)1.5Tunes ν x /ν y /ν z 6.57/7.6/0.034 Energy loss/turn U 0 (keV) 121Chromaticities ν ’ x /ν ’ y -11.9/-25.4 Damping time τ x /τ y /τ z (ms) 25/25/12.5Natural bunch length σ z0 (cm)1.3 Total current/beam I(A)0.91 Crossing angle  (mrad) ±11 SR Power P(kW)110Piwinski angle Φ(rad)0.435 Bunch number N b 93Bunch spacing S b (m)2.4 Bunch current I b (mA)9.8 Beam-beam parameter  x /  y 0.04/0.04 Particle number N t 4.5×10 12 Luminosity(10 33 cm -2 s -1 ) L 0 1.0

20. 20 BEPCII/BEPC/CESRc Comparison

21. 21 BEPCII Key Technologies and Challenges   Linac  Injection rate: 5 mA/min.  50 mA/min.  New positron source  Stability and reliability  E inj = 1.55-1.89 GeV  500MHz SC RF System  SC RF Technology  Power source and low level  Cryogenics…   Injection  Magnets  Power supplies  Vacuum system  SC Q magnet and IP  Beam instrumentation  Control system

22. 22 Linac Upgrade Requirements:  Positron injection rate 5mA/min.  50 mA/min.;  Energy 1.3 GeV  1.55 ~ 1.89 GeV; Use 45MW Klystron,upgrade RF source, replace 8 aged acceleration tubes ； Bombarding energy for positron 150 MeV  240 MeV; Electron gun beam intensity 5A  10A ； Produce new positron source, improving efficiency ； Improve focus and orbit-correction system ； Repetition rate 12.5 Hz  50 Hz ； Pulse duration 2.5ns  1ns ； Possibility of double pulse injection (f RF /f Linac =7/40);

23. 23 means and factors for increase injection rate

24. 24 SC RF System Requirements ： Sufficient voltage Sufficient power reducing coupling instability stability, reliability Measures: collaborate with SSRF, Cornell and KEK ， using existing technology.

25. 25 Super-conducting Cavity CESR-type Cavity (ACCEL) KEKB-type Cavity (Mitsubishi ) 2IHEP/KEK/SSRF collaborating group will optimize the cavity design, follow the manufacture process and technology, master the required techniques for operating and repairing the cavities.

26. 26 Interaction point and SC Q magnet

27. 27 Beam Feedback System Challenge ： How to insure collision? Beam-beam bending and scanning techniques ：  Beam-beam bending ： accelerator physics  Bending measurement ： beam instrumentation  Scan feedback ： automatic control

28. 28 BES III Expected Event Rates At  10 33,at J/  and 4.14 GeV, ~0.6  10 33 ParticleEnergy Single Ring （ 1.2f b -1 ） Double Ring (4f b -1 ) D0D0  7.0  10 6 2.3  10 7 D+D+  5.0  10 6 1.7  10 7 Ds 4.14GeV 2.0  10 6 4  10 6 +-+- 3.57GeV 3.67GeV 0.6  10 6 2.9  10 6 0.2  10 7 0.96  10 7 J/  3-4  10 9 6-10  10 9  0.6  10 9 2  10 9

29. 29 BESIII Design Goals High event rate ： lum. :10 33 cm -2 s -1 and bunch spacing 8ns ， hardware trigger rate: 4000 Hz ， putting on mass medium: 3000 Hz. Improve detector resolutions, especially for photons Improve particle identification Enlarge detector solid angle acceptance Design interaction region to fit sc Q magnets

30. 30 Schematic of BESIII Detector

31. 31 BESIII Main Sub-systems CsI EM Calorimeter:  E/E ~3.5%@1GeV (inc. dead material)~3.5%@1GeV MDC: small cell, Al field wire and He-based gas  P/P (1GeV) = 1.4 %@0.4T, 0.6 %@1T,  dE/dx = 6-7 % Time of Flight:  T: barrel 90 ps ； endcap 110 ps  counter(RPC): readout strip width ： ~4 cm Luminosity Monitor(LM)  L/ L = 3-5% SC Solenoid ： 1 Tesla, I.R. 1.32 m, Length 3.8 m New Trigger and Online system for multi-bunch and high lum. Operation, 4000Hz, 3000Hz to mass storage New Electronics ： pipeline operation Offline computing : PC farm, mass storage

32. 32 Small cell, 46-47 layers He based gas HeC 3 H 8 ( 60:40) Position resolution 130  m Mom. Resolution 0.6% at 1 GeV at 1 Tesla 1.4% at 1 GeV at 0.4 Tesla

33. 33 BESIII mechanical structure Dimensions need final tuning

34. 34 BESIII Electronics specification list Feb. 21, 2002 Item time measurement Charge measurement Count rate per channel Information provided to trigger Numbe r of channel σtσt INL Ran ge Cro ss- talk Nu mber of cha nnels σQσQ INL Dynami c range Cro ss- talk Type Quant. MDC 9000 0.5-1 ns ≤0.5 % 0- 400n s 9000 5fc ≤2 % 15 fc - 1800fc 1% 1% 30 k/s hit TOF + CCT 352+ 104 ≤25 ps 0- 60ns 456 12bits (ENOB ) ≤2 % 20mv – 4v 2-4 k/s hit 456 EMC BAR 8064 + 1800 0.16 fc 200Ke V 1% 1% 0.5fc - 1500fc 0.3 % 1 k/s Summati on Of analog EMC (End) 1800 0.16fc 1% 1% 0.5fc - 1500fc 0.3 % 1 k/s Summati on Of analog Mu Chan ~10000 Spec Considering multiple hit time measurement

35. 35 Sub-systemBES IIIBESII  XY (  m) = 130 250 MDC  P/P ( 0 / 0 ) = 0.6 %(1 GeV) SC 1.4 %(1 GeV) Normal 1.7% √2 (1 GeV)  dE/dx ( 0 / 0 ) = 6-7 % 8.5% EM Calorimeter  E/√E( 0 / 0 ) = 3.5 %(1 GeV)  z (cm) = 0.5cm/ √E 20% (1 GeV) 3 cm / √E Time of Flight  T (ps) = 90 ps barrel 110 ps endcap 180 ps barrel 350 ps endcap  Counters9- 10 layers3 layers Magnet 1.0 tesla Option 1 0.4 tesla Option 2 0.4 tesla Comparisons between BESIII and BESII

36. 36 BESIII detector with existing magnet Worse mom. Resolution, Better low mom. efficiency

37. 37 BESIII Expected Physics Results Monte Carlo simulation show: because lum. Increase by two-orders of magnitude, a factor of 3 – 7 of that of CLEOc ， BES III can obtain many important results in tau-charm physics Topics ： Precise measure CKM parameters Precise R measurement Search for glueballs, determine spin and parity Search for 1 P 1

38. 38 Physics example 1 ： precise measure CKM matrix Measure pure-leptonic and semi-leptonic decay Br. Fractions of charm mesons to determine V cd and V cs Measure hadronic decay Br. Fractions of charm mesons for determine V cb Measure f D and f Ds for determining V td and V ts Measure semi-leptonic shape of D and Ds for V ub CKM unitarity check

39. 39 Br. Fractions of D decays （ involving leptons ） Decay Mode Input Br(%) Measured Br(%)(80 pb –1 ) Relative Error (stat.)(5 fb –1 ) 3.4 0.6 % 0.4 1.5% 8.5 1.5% 0.03 evts ~340 evts  f D /f D ≈3%

40. 40 Physics example 2 ： R measurement Error Source BESII reach(%) BESIII goal(%) Luminosity 2 - 3 1 Selection effi. 3 - 4 1 - 2 Trigger effi. 0.5 Radiation corr. 1 - 2 1 Model of hadron decay 2 - 3 1 – 2 Statistical 2.5 -- Total error 6 – 7 2 - 3

41. 41 Physics example 3 ： Search for 1 P 1  S)    P 1    c     r = (1.2 – 3.3)×10 -6  1 P 1: 450-1200 evts/year  ackground:  S)   c1,  c2,,     

42. 42 Other expected physics reaches and background study by MC simulation will be covered by Dr. Wang Yifang Most of the main detector sub-systems will be covered by other speakers, I will say a few words about these sub- systems which are not presented separately today. Interaction region Mechanical preliminary design Slow Control

43. 43 Interaction Region It is very compact at IR, very close cooperation is needed in the designs of detector and machine components at IR Understand the space sharing, the support, vacuum tight Understand the backgrounds from machine and how to reduce them, good vacuum near detector is required - Beam loss calculation (masks) - Synchrotron radiation (masks) - Heating effect (cooling if necessary) Understand the effects of the fringe field from SCQ to the detector performances, the preliminary study shows that, field uniformity should be better than 5% in most of the MDC volume Center of beam pipe will be a double-wall Be pipe

44. 44 BESIII Mechanical design and Detector Hall Detector on two rail pads to move in south-north Iron Yoke Barrel~ 285 tons; endcap ~2  52 tons. at both sides between barrel and endcap, there should be a slot of 1100x 80mm for each side of octagon on every terminal surface of the barrel of yoke, for cable space.

45. 45 Assembled Structure, test assembling at factory

46. 46 Movable endcap yoke; reposition for field stability endcap EMC supporting and moving design, removing and reconnecting cables should not change the gain.

47. 47 Arrangements of electronic crates, moving with detector

48. 48 Arrangements for cooling water, gas, cables

49. 1.Temperature measurement: > 1000 EMC CsI, 600 ; MDC 16; , 150; electronics crates, 300; cable rack, 100; environment, 100; 2. Humidity measurement: ~250 CsI, 200 ; MDC, 8; electronics, 20; environment, 30; 3. Low HV of VME crates: 500. 4. MDC gas ： 8. 5. Voltage of power supply: several. 6. Other measurements? Magnetic field; parameters in SC magnet and cryogenics; HV parameters for detectors; radiation dose; He leakage; flammable gas;others. Slow control system Required measurements from detector and electronics

50. ONE WIRE BUS can be used to read these signals out Probe/master, doing R&D 64 bit W. A. O （ unique code worldwide), 12 bit DATE Temperature probe: DS18B20, 22 RMB/probe humidity probe: LTM8802, ~150 RMB/probe 1. Humidity range: 1~99% ， typical precision: 3%. 2. Temperature range: -30 ℃ ~60 ℃， accuracy 0.5 ℃ D. C voltage probe: DS2438/ LTM8805, several dozens of RMB/probe analog voltage:0 ～ 10V （ resolution ： 0.01V ） Light-decoupling between PC and master to reduce noise pickup, LTM － 4850/2 dual-port RS － 485 card

51. 51 BESIII Key Technology and Challenge Control background (with machine people), take good quality data at high luminosity. Small ring is more problematic with background and radiation dose! Design and operate SC magnet Stable operation of MDC(>30000 wires), obtaining better resolution Obtain best possible EMC energy resolution, by quality control in detector construction and good calibration systems Obtain best possible TOF resolution, all factors controlled Build a trigger and DAQ system, with required data transfer rate and good performance (specifications, reliability)

52. 52 Some preliminary design issues, such as TOF readout electronics, EMC support structure etc are not finalized The tasks for offline systems are defined, people are assigned, the important issue is that the overall structure of offline system should be decided ASAP, so people can start to work on the software Determination of some of main design options Magnet? super-conducting/existing normal; performances and cost Particle ID? (TOF/ Ĉerenkov based) Cost and schedule concern Cost for EMC, SC magnet and electronics is most crucial; MDC, EMC and SC magnet (including iron structure) on critical path;

53. 53 BESIII will be competitive in producing good physics results after its completion; can help to master advanced technology related to detector design and construction, fast electronics, DAQ and data analyses, help to catch up with world level or close the gap. But, construction of BESIII and obtaining world class results, are big challenge to Chinese HEP experimentalists, need to master new techniques, such as super-conducting, low-Z small cell MDC; high precision EM calorimeter; pipeline fast electronics, fast data acquisition, huge data storage and processing; Need international collaboration （ Japan, US, Korea) 。

54. 54 Conceptual design started in 1999. Feasibility study started in the summer of 2000 ， completed in Aug. of 2001. Preliminary design started in the summer of 2001 ： –Machine finished physics design, requirements for sub-systems are determined; –Sub-system designs are progressing well –Detector design is progressing well, prototype and detailed mechanical design –Expected to finish preliminary design in 2002 Upgrade of Linac started. R&D for key technologies started ： SC cavity, Q magnet Project Status

55. 55 Feasibility Study/Design Review BEPC II feasibility international review ( 01. 4. 2 – 6, Beijing ) 26 experts reviewed the feasibility of machine and detector BEPC II machine feasibility review ( 01. 7. 29 - 30 Beijing ) 21 domestic experts reviewed machine feasibility and preliminary design. BESIII International Workshop ( 01.10.13 – 15 Beijing ) International technical review of machine preliminary design at SLAC, May, 2002 BESIII preliminary design review, in Sep. of 2002

56. 56 Project Schedule and Budget Done Feasibility Study Report submitted.  End of Sep. of 2002 Preliminary Technical Design Report  June 2003 R&D and prototype  May 2004 BEPC run July 2002  June 2006 Construction May 2004  Nov. 2004 BESII dismounting and Linac upgrade Nov. 2004  Jan. 2005 Linac commissioning Jan. 2005  Apr. 2005 SR run Apr. 2005  Jan. 2006 Storage ring assembling Jan. 2006  June 2006 Commissioning of storage ring June 2006  Sep. 2006 BESIII detector moved to beam-line Sep. 2006  Commissioning machine and detector Very tight schedule

57. 57 BESIII Schedule 2001.1~2002.6 Preliminary design 2001.7~2003.6 R&D of critical parts 2002.7~2005.9 Construction of detector components 2003.1~2004.6 Construction of return yoke 2002.3~2004.12 Design of super-conducting magnet 2004.7~2004.11 BESII disassembling 2004.12~2005.3 BESIII iron yoke assembling (with magnet) 2005.4 Commissioning of cryogenics 2005.5~2005.8 Magnet field measurement （ with SCQ ） 2005.9~2006.1 Assembling of other detector components 2006.2~2006.6 Commissioning of BESIII detector 2006.7~2006.8 BESIII moved to beam-line 2006.9~2006.12 Commissioning of BEPCII+BESIII Some sub-systems maybe problematic to meet the schedule

58. 58 BEPCII Team and Administration BEPC II project leaders and headquarter are established; 4 Major systems, Linac; Ring; Detector; Technical support( cryogenics). Most of responsible persons for sub-systems are appointed. Some procedures are established, quality control; budget control; technical review; etc.

59. 59 BEPCII Budget (10K RMB) BEPCII Budget (10K RMB) ItemBudgetPercentage 1.Linac44006.87% 2.Ring2290035.78% 3.Detector2100032.81% 4.Infrastructure57809.03% 5.Assembling25003.91% 6.Building3200.50% 7.Others33005.16% 8.Overhead6000.94% 9.Contingency32005.00% Total64000100.00%

60. 60

61. 61

62. 62

63. 63 BEPCII Domestic Collaboration Participation from other Institutes and Universities from China, in charge of one sub-system or collaboration with IHEP Shanghai Synchrotron Light Source –500 MHz RF system Shanghai Institute of Ceramics ： CsI crystals Beijing University ： RF system, detector Qinghua University ： Accelerator technique, detector University of Science and Technology of China ： Detector, readout electronics

64. 64 BESIII Domestic Collaboration Design, MC simulation Sub-detectors R&D and construction Electronics R&D and manufacture Online/Offline software Software package Reconstructions Calibration Physics study In charge of some sub-system or send people to IHEP

65. 65 BEPCII International Collaboration International collaboration played an important roll in BEPC/BES project ， Expect to play major roll in the design and construction of BEPCII / BESIII ： – BNL of US: SC Q magnet; – SLAC of US: Key machine technology, design reviews; – KEK of Japan: SC cavity and SC solenoid… –Improve technical excellency and research capability Advice and help in design and construction in various systems; Technical review and follow-up in detector design, construction and commissioning.

66. 66 BEPCII / BESIII can attract international participation, especially in detector and physics; Share cost ， improve detector performances Institute of High Energy Physics, Beijing Tsinghua University, Beijing Beijing University, Beijing Sichuan University, Chengdu University of Science and Technology of China, Hefei University of Hawaii, Honolulu Shandong University, Jinan Nanjing University, Nanjing Shanghai Institute of Ceramics, Shanghai National Central University, Taipei University of Tokyo, Tokyo University of Washington, Seattle Huazhong Normal University, Wuhan

67. 67 More Institutes from US and Japan may join, Korea has interest in participating Should form BESIII international collaboration according to international standard: Institutional board; Executive board; Spokesperson; etc. International review/Documentation/ video conferencing

68. 68 Summary  BEPC/BES meet opportunity and challenge in the field of tau- charm physics.  BEPCII double-ring design luminosity 10 33 cm -2 s -1 at 1.89 GeV ， with major upgrade of BES ， can insure an important roll in world HEP, especially in tau-charm physics.  BEPCII/BESIII is technically feasible, should be started as soon as possible.  BESIII has a baseline design, optimization is needed  Strength domestic collaboration ， stimulate developments of relevant technologies in China.  International collaboration in BEPCII/BESIII construction.  BESIII Collaboration should follow international standard.

69. 69 Hope this review meeting can help BESIII to improve its design Thanks

70. 70 Sub-systemBES IIICLEOc  XY (  m) = 130 110-130 MDC  P/P ( 0 / 0 ) = 0.6 %(1 GeV) SC 1.4 %(1 GeV) normal 0.5 %(1 GeV)  dE/dx ( 0 / 0 ) = 6-7 % 6% EMC  E/√E( 0 / 0 ) = 3.5 %(1 GeV)  z (cm) = 0.5cm/ √E 2.3 %(1 GeV) 0.5 cm / √E TOF  T (ps) = 90 ps Barrel 110 ps endcap RICH  counter9- 10 layers3layers magnet 1.0 tesla option 1 0.4 tesla option 2 1.0 tesla Comparison Between BESIII and CLEOc

71. 71 Infrastructure BEPCII needs some building construction: halls for Cryogenic system and additional magnet power supplier; improving shielding of some buildings, etc. Major systems: –New cryogenic system: capacity of 1kW/4.5K –BEPCII power consumption to be doubled 110kV transformer: 6300kVA  12500kVA New electric crates and apparatus –Increase capacity of air-conditioning –Improve water circulation system –Improve pure water system

72. 72 More room is needed for electronics, two more steps

73. 73 High Energy Physics 1 ） BEPC future development  BEPC II: - BEPC / BES major upgrade, increase luminosity by more than one order of magnitude; - Main physics goal: J/ ,  ′and D/DS physics; 2 ） Strength non-accelerator experiments: Cosmic ray, astro-physics experiments, neutrino experiment…; 3 ） International Collaboration Chinese Academy of Sciences ： The strategy for Chinese HEP and Advanced Accelerator technology

74. 74 Science-education Leading Group of State Council, the 7th meeting (2000.7.27), discussed the report by CAS about HEP Conclusions ： （ 1 ） Approval in principle of 《 Report about the future development of Chinese HEP and advanced accelerator technology 》 by CAS. Meanwhile, CAS should consult further with experts in China and abroad ， strength and attract more international collaboration. （ 2 ） In view of the success of BEPC, approval of major upgrade of BEPC, with a budget of 400 M RMB. With relatively small invest, continue to obtain high-level achievements. (At that time, it was meant single-ring)

75. 75 Superconducting Cavity BEPCII Superconducting Cavity 北对撞点

76. 76 BEPCII Vacuum system  At designed current dynamic vacuum （ curve 8  10 -9  ， IP 5  10 -10  )  reduce impedance, avoid instability. Measures IP use big pump, Smooth vacuum chamber, avoid gap and cavity; Absorb SR photons; Positron ring vacuum chamber tim coated, reduced second emission.

77. 77 IP and SCQ Magnet