KEKB and Super KEKB Y Ohnishi Super B

KEKB and Super. KEKB Y. Ohnishi Super. B Workshop LAL, Orsay 15 -18 February, 2009 Y. Ohnishi / KEK 1

March – December, 2008 Machine parameters Luminosity history Specific luminosity Vertical beam size Lifetime Beam-beam simulations RECENT STATUS OF KEKB Y. Ohnishi / KEK 2

March-December, 2008 Winter shutdown Summer shutdown Y. Ohnishi / KEK 3

KEKB machine parameters 15 Nov. 2006 (before crab) Date Current 19 May 2008 ( with crab) LER HER 1. 65 1. 33 1. 60 0. 933 A Bunches 1389 Bunch current unit 1584 1. 19 0. 96 1. 01 0. 590 m. A Emittance 18 24 15 24 nm x* 59 56 90 90 cm y* 6. 5 5. 9 mm x* 103 107 116 147 mm y* 1. 8 1. 1 mm nx 45. 505 44. 509 ny 43. 534 41. 565 43. 567 41. 596 ns -0. 0246 -0. 0226 -0. 0240 -0. 0204 xx 0. 117 0. 070 0. 099 0. 119 xy 0. 108 0. 058 0. 101 0. 096 Spec. L/#bunchluminosity Specific Luminosity 1030 cavity. cm-2 s-1/m. A 2 with 11. 1 crab cavity is 60 % larger 17. 8 than before crab 17. 6 geometrical loss due to X-angle ~ 11% 16. 8 Y. Ohnishi / KEK 1033 cm-2 s-1 4

Lspec/nb (x 1030 cm-2 s-1 m. A-2) Specific luminosity x*/ y* 0. 9/0. 007 m crab on 1. 5/0. 0059 m crab off beam-beam simulation 1. 5/0. 0059 m crab on 0. 8/0. 0059 m crab on 0. 59/0. 0065 m crab off x*=0. 8 m k=1% with crab x*=1. 5 m k=1. 0 % k=1. 3 % with crab x*=1. 5 m k. LER=0. 5 % k. HER=0. 3% w/o crab I bunch(LER) x I bunch(HER) m. A 2 Y. Ohnishi / KEK 5

Estimation of vertical beam size with dynamic effect Vertical Beam Size (mm) nx, LER/HER = 0. 508/0. 510 ny, LER/HER = 0. 590/0. 590 x*LER= x*HER y*LER= y*HER 0. 59/0. 0065 m crab off 0. 8/0. 0059 m crab on 0. 9/0. 007 m crab on 1. 5/0. 0059 m crab off k=0. 5 % I bunch(LER) x I bunch(HER) m. A 2 Y. Ohnishi / KEK 6

Beam-Beam Tune Shift (HER) w/o dynamic effect x*/ y* xy (HER) xy, HER = 0. 09 0. 9/0. 007 m crab on 0. 8/0. 0059 m crab on xy, LER<xy, HER 1. 5/0. 0059 m crab on 1. 5/0. 0059 m crab off 0. 59/0. 0065 m crab off I bunch(LER) m. A Y. Ohnishi / KEK 7

Beam-Beam Tune Shift (LER) w/o dynamic effect 0. 59/0. 0065 m crab off xy (LER) 0. 9/0. 007 m crab on 0. 8/0. 0059 m crab on 1. 5/0. 0059 m crab off I bunch(HER) m. A Y. Ohnishi / KEK 8

Summary of specific luminosity • Specific luminosity is decreasing as increasing bunch current products. • Beam-beam tune shift is reaching the ceiling by 0. 09. • Vertical beam size estimated from the luminosity is small at lower bunch current products. – Emittance ratio(ey/ex) should be small without beam-beam (k=~0. 5 %). – Vertical beam size blowup can be seen as increasing bunch currents. – Crab ON can reduce the vertical beam size blowup than Crab OFF. Y. Ohnishi / KEK 9

Degradation of specific luminosity Candidates – Horizontal offset at IP depends on bunch currents. • In order to keep beam lifetime at higher bunch currents, horizontal offset has to be increased. – Beam current dependence of emittance growth in a single beam? – Machine errors • X-Y coupling, R-chromaticity, etc. – Something wrong for the beam-beam simulation • Is there any missing effects ? • Y. Cai gives a beam-beam simulation with wakefield. Y. Ohnishi / KEK 10

Horizontal offset Beam-beam simulation K. Ohmi & Y. Funakoshi Horizontal offset scan at physics run lifetime vertical size luminosity Horizontal offset Typical value(~15 mm) • Horizontal offset of colliding beams can not be set at a value giving maximum luminosity due to short beam lifetime. • Short beam lifetime is caused by a strong beam-beam interaction. • The allowed horizontal offset depends on the bunch currents. ⇒ slope of the specific luminosity. Y. Ohnishi / KEK 11

Horizontal offset: Why lifetime is short? • Dynamic beta and dynamic emittance. • Smallest aperture in the vicinity of the crab cavity. miss-alignment of the components • To cure this effect, we make a beta function around the crab cavity small as possible. – reduce the horizontal beta function by changing magnet configuration – increase the beta function at IP • Positron/electron simultaneous injection Y. Ohnishi / KEK 12

Aperture survey around HER crab cavity • Orbit at the crab is determined to minimize beam loading(blue). crab • Additional horizontal bump(green) makes beam lifetime longer. HER Beam lifetime Ib, LERx. Ib, HER = ~1. 5 m. A 2 Y. Ohnishi / KEK 13

Beta function at LER (without beam-beam) H. Koiso before summer crab x*=0. 9 m after summer crab x*=0. 9 m crab Y. Ohnishi / KEK x*=1. 5 m 14

HER/LER simultaneous Injection N. Iida • HER and LER injection can be switched in 2 sec so far. – pulse-to-pulse injection(20 msec interval at minimum) will be available for the next run. • The injection rate is good as usual. • The beam current variations are one order smaller than before for both rings. 0. 19% 1. 7% HER 2. 5% 0. 25% LER Y. Ohnishi / KEK 15

Vertical beam size measurement HER LER N. Iida Bunch current (m. A) The vertical beam size is less dependent on the bunch current. Y. Ohnishi / KEK 16

Machine error • Beam-beam simulations with machine errors and knob tuning are studied. • Machine errors are 4 or 5 units deviation for coupling parameters and dispersions at IP as the initial condition. • The luminosity was achieved by only 60 % of the ideal case when the downhill simplex optimization together with single knob scan was performed. • If the simulation is relevant, we can not reach a real peak luminosity at the real machine includes error. • For instance, X-Y coupling error at IP affects the luminosity performance. Y. Ohnishi / KEK 17

Measurements of R-chromaticity Measured by single-pass BPMs LER model (SAD) r 4, IP r 3, IP (m-1) LER model (SAD) Dp/p 0 We will install skew sextupoles to correct R-chromaticity. HER model (SAD) HER r 4, IP r 3, IP (m-1) Dp/p 0 model (SAD) Dp/p 0 Y. Ohnishi / KEK Dp/p 0 18

Summary of KEKB • Efforts to explain the steep slope of the specific luminosity are still going on. • We found the reason of the short beam lifetime at high bunch currents. – aperture in the vicinity of the crab cavity restricts the lifetime. – by changing beta functions, 1. 5 m. A 2 could be stored. (design bunch currents of Super. KEKB) • Machine errors seems to be able to explain the degradation of the specific luminosity. – method of the IP knob tuning – X-Y coupling at IP, R-chromaticity, etc. Y. Ohnishi / KEK 19

Total integrated luminosity KEKB+PEP-II KEKB 895 fb-1 PEP-II We will reach 1 at-1 in the next fiscal year. Y. Ohnishi / KEK 20

BELLE at KEK-B and Babar at SLAC confirmed Kobayashi-Maskawa Model A. Suzuki Congratulations ! Kobayashi Maskawa Y. Ohnishi / KEK 21

Update from 2008 Summer Machine parameters CSR Travel waist IR design RECENT PROGRESS ON SUPERKEKB MACHINE DESIGN Y. Ohnishi / KEK 22

Machine Parameters of Super. KEKB (1) symbol LER HER unit Beam Energy E 3. 5 8. 0 Ge. V Beam current I 9. 4 4. 1 A Circumference C 3016 Number of bunches nb 5018 Number of particles N/bunch Emittance ex 12 nm Emittance ratio ey/ex 0. 5 % Beta (hor. ) at IP x* 200 mm Beta (ver. ) at IP y* 3 mm Bunch length z 3 mm Crossing angle qx* 30 to 0(crab crossing) mrad Beam-Beam (hor. ) xx 0. 27 Beam-Beam (ver. ) xy 0. 30 Tunes nx/ny/ns Luminosity L 11. 8 m 5. 1 x 1010 . 505/. 590/-0. 025(+ap) 5. 5 Y. Ohnishi / KEK x 1035 cm-2 s-1 23

Machine Parameters of Super. KEKB (2 a) symbol LER HER unit Beam Energy E 3. 5 8. 0 Ge. V Beam current I 9. 4 4. 1 A Circumference C 3016 Number of bunches nb 5018 Number of particles N/bunch Emittance m 11. 8 5. 1 x 1010 ex 24 18 nm Emittance ratio ey/ex 1 0. 5 % Beta (hor. ) at IP x* Beta (ver. ) at IP y* 3* 6 mm Bunch length z 5 3 mm Crossing angle qx* Beam-Beam (hor. ) xx 0. 182 0. 138 Beam-Beam (ver. ) xy 0. 295 0. 513 Tunes nx/ny/ns . 505/. 590/0. 025(-ap) Luminosity L 200 mm 30 to 0 (crab crossing) 5. 3 Y. Ohnishi / KEK *Travel waist in LER mrad x 1035 cm-2 s-1 24

Machine Parameters of Super. KEKB (2 b) symbol LER HER unit Beam Energy E 3. 5 8. 0 Ge. V Beam current I 9. 4 4. 1 A Circumference C 3016 Number of bunches nb 5018 Number of particles N/bunch Emittance m 11. 8 5. 1 x 1010 ex 24 18 nm Emittance ratio ey/ex 1 0. 5 % Beta (hor. ) at IP x* Beta (ver. ) at IP y* 3* 6 mm Bunch length z 5 3 mm Crossing angle qx* Beam-Beam (hor. ) xx 0. 184 0. 139 Beam-Beam (ver. ) xy 0. 228 0. 385 Tunes nx/ny/ns . 505/. 590/0. 025(-ap) Luminosity L 400 mm 30 to 0 (crab crossing) 4 Y. Ohnishi / KEK *Travel waist in LER mrad x 1035 cm-2 s-1 25

Coherent synchrotron radiation • Coherent synchrotron radiation(CSR) in studied by T. Agoh. Square cross section for the beam pipe (see Lo. I, 2004). • An independent estimation has been done by K. Oide in 2008. Realistic ante-chamber and other impedances are included. • Both results are consistent each other. • The CSR problem gives us a big change of the machine design. Y. Ohnishi / KEK 26

Wakefield at Super. KEKB K. Oide, et al. LER CSR wake chamber radius=45 mm Y. Ohnishi / KEK 27

Bunch length and energy spread LER positive alpha z/ z 0 K. Oide HER positive alpha Super. KEKB d/ d 0 design LER has a big problem. Bunch length increases by 80 %. Energy spread increases by 60 %. HER has no problem on CSR. 20 % increase for positive a a few % for negative a z/ z 0 d/ d 0 HER negative alpha d/ d 0 z/ z 0 Y. Ohnishi / KEK 28

Optimization of bunch length LER positive alpha z/ z 0 negative alpha z/ z 0 d/ d 0 positive alpha zero bunch current K. Oide d/ d 0 negative alpha LER HER z 0 5 3 4. 5 3 mm d 0 7. 1 6. 8 x 10 -4 6 3. 6 5. 3 3. 1 mm 8. 0 7. 0 8. 5 7. 7 x 10 -4 design bunch current z d Y. Ohnishi / KEK 29

Travel waist scheme • Original idea is given by a linear collider (Balakin, et al. , 1992) • Crab cavities and sextupoles can make a travel waist at IP. • Travel waist is applied to LER to compensate longer bunch length. Vertical waist moves backward along z. HER LER Y. Ohnishi / KEK LER 30

Travel waist scheme (cont’d) • In order to make HI=zpy 2 at IP, combination of the crab cavities and sextupoles are used. • The Hamiltonian of a sextupole is: • Transformation from the sextupoles: Travel waist Crab waist Y. Ohnishi / KEK 31

Travel waist scheme (cont’d) Dyx=p/2 Travel waist must be localized. SX 2 Crab SX 1 IP SX 1 Crab SX 2 Dyx=p X Dyy=p/2 • X 3 and XPY 2 terms can be canceled by –I pair of the sextupoles with keeping ZPY 2 term. • In order to make the travel waist, required strength of the sextupole is K = 2~3 m-2 B’’L = 23~35 T/m Y. Ohnishi / KEK 32

Travel waist in LER lattice H. Koiso x/ y, sext=15/350 m x, crab =50 m Vcrab=1. 56 MV Y. Ohnishi / KEK 33

Dynamic aperture with travel waist in LER Crab OFF, K 2=0 Crab OFF, K 2=1. 846 Crab ON, K 2=1. 846 Required acceptance for injection: Ax=7. 5 x 10 -6 m Ay=1. 2 x 10 -6 m Dp/p=+-0. 3 % H. Koiso Y. Ohnishi / KEK 34

Beam-beam simulation (Strong-Strong) Super. KEKB (2 a) Luminosity (x 1035) Travel waist to compensate LER long bunch Negative alpha K. Ohmi ex(LER) =24 nm ex(HER) =18 nm y*(LER) =3 mm y*(HER) =6 mm 5. 3 x 1035 number of turns Y. Ohnishi / KEK 35

IR design • IR design is still “chaotic”. • One candidate of x*=40 cm is found, however no consistent solution for 20 cm so far. • Issues are: – – – – physical apertures dynamic beta injection synchrotron light path detector background. design of final focus magnets technical issue for assembly Y. Ohnishi / KEK 36

New IR quadrupoles • New quads are introduced to reduce beta function at IR magnets. – – – 1. 9 K superconducting and permanent. x at QC 2 in new optics for x*=20 cm is smaller than old x*=40 cm optics. Left-side of IP is acceptable for physical aperture and SR fan. Old: HER BX*/BY*= 40/0. 3 cm New: HER BX*/BY*= 20/0. 5 cm R-side Left-side HER beam QC 2 L QC 1 L QCSLF QCSLD QCSRF QC 1 R QC 2 L QC 1 L QCSR QC 1 R QC 2 R Y. Ohnishi / KEK 37

New IR geometry QC 2 RE QC 2 LP QC 1 RE QCSL (1. 9 K) QCSR LER beam HER beam QCSLFE (permanent) M. Tawada QC 1 LE QC 2 RP QC 2 LE Y. Ohnishi / KEK 38

Super. KEKB IR magnet configuration QC 1 RE Vert. f QC 2 LP Horz. f Positrons Off axis of QCSLD S-L Detector solenoid axis Electrons Off axis of QCSRD Vert. focus S-R IP 30 mrad QC 2 LE Horz. f IP chamber axis 7 mrad 8 mrad 15 mrad QC 1 LE Vert. f QC 2 RE Horz. f QCSLFE Horz. f Electrons Off axis of the solenoid On axis of QCSLD Vert. focus Positrons Off axis of the solenoid On axis of QCSRD Vert. focus QC 2 RP Horz. f QCS[L, R]D are overlapped with anti-solenoids N. Ohuchi, M. Tawada Y. Ohnishi / KEK 39

IR Beam Envelops based on the beam optics by Koiso HER QC 2 REH 17. 49 T/m, 10. 49 T QC 1 RES 15. 87 T/m, 12. 69 T QCSRD 36. 38 T/m, 12. 11 T QCSLD 53. 01 T/m, 23. 33 T QCSLF 44. 34 T/m, 23. 06 T QC 1 LES 34. 79 T/m, 22. 27 T QC 2 LEH 5. 13 T/m, 10. 26 T LER QC 2 RP 3. 06 T/m, 3. 10 T QCSRD 36. 38 T/m, 12. 11 T QCSLD 53. 01 T/m, 23. 33 T QC 2 LP The space for the magnet design is defined by the area of 5 of beam size + 5 mm for the design margin of beam pipe + 3 mm thickness of beam pipe. 10. 58 T/m, 6. 49 T N. Ohuchi, M. Tawada Y. Ohnishi / KEK 40

LER IR optics • • • x* is still 40 cm determined by the right-side. A new superconducting quadrupole are used for the left-side. Field gradient is optimized for LER. IR: BX*/BY*= 40/0. 3 cm Right-side Tsukuba: BX*/BY*= 40/0. 3 cm Left-side IP QC 2 L QCSR QC 2 R QCSL Field gradient 53. 0 T/m Distance (IP-Mag. center) 0. 66 m Effective 0. 44 m Y. Ohnishi /length KEK H. Koiso 41

HER IR optics • • New quadrupoles are adopted in the left-side. Additional horizontal focusing quad (permanent) is introduced. BX*/BY*= 40/0. 5 cm R-side BX*/BY*= 40/0. 5 cm L-side IP QC 2 L QC 1 L QCSLF QCSLD QCSRD QC 1 R QC 2 R QCSLF Field gradient 44. 3 T/m Y. Ohnishi / KEK H. Koiso 42

Summary of Super. KEKB • CSR is a serious problem for the short bunch in LER. • We make the bunch length in LER longer than the original design, z = 3 to 5 mm. • In order to compensate the long bunch length, the travel waist scheme is applied in LER. • Emittance and beta functions at IP are optimized by beam-beam simulations for the new machine parameters. • IR design is going on. IR for x*=40 cm exists, however we are still optimizing optics for x*=20 cm. Y. Ohnishi / KEK 43

APPENDIX Y. Ohnishi / KEK 44

Definition of X-Y coupling Transformation from a decoupled coordinate to a physical coordinate: When Y=0 and Y’=0 (H-mode): This induces a vertical betatron oscillation. Y. Ohnishi / KEK 45

Travel waist • Linear part for y. z is constant during collision. α=0 • Minimum β is shifted at s=-az Y. Ohnishi / KEK 46

LER straight section βx/y @ SX = 15/350 m βx @ crab = 50 m Vcrab = 1. 56 MV sextupole - crab – sextupole -I’ transformation between sextupoles Y. Ohnishi / KEK 47

Injection aperture • Injection apertures are evaluated: – – HER/LER 4. 5 E-6/7. 5 E-6 m w/o Damping Ring HER/LER 1. 9 E-6/2. 6 E-6 m with Damping Ring emittance of injection beam (m) Y. Ohnishi / KEK M. Kikuchi 48

Injection aperture (cont’d) • Larger aperture is required with a large beam-beam effect. red points: no beam-beam Y. Ohnishi / KEK M. Kikuchi 49

Lattice parameters (1) symbol LER Horizontal emittance ex 12 12 nm Beta (hor. ) at IP x* 200 mm Beta (ver. ) at IP y* 3 3 mm Bunch length z 3 3 mm RF voltage VC 12 17. 4 MV Momentum compaction ap 1. 9 x 10 -4 1. 4 x 10 -4 Betatron tune nx/ny 45. 505/42. 590 44. 505/41. 590 -0. 0231 -0. 0157 Synchrotron tune ns Y. Ohnishi / KEK 50

RF parameters * Assumption symbol LER HER unit Beam Energy E 3. 5 8. 0 Ge. V Beam current I 9. 4 4. 1 A Energy loss U 0 0. 84 3. 42 MV Radiation loss Prad 7. 91 14. 02 MW Total loss factor* k 40 ± 5 45 ± 10 V/p. C Parasitic loss PHOM 7. 09 ± 0. 89 1. 52 ± 0. 34 MW Total beam power Ptot 15. 0 ± 0. 9 15. 5 ± 0. 3 MW Cavity type modified ARES SCC Number of cavities Ncav 22~24 16~18 8 Voltage/cavity Vcav 0. 5 1. 3 MV Beam power/cavity Pcav 650 720 460 k. W Wall loss/cavity Pwall 233 150 - k. W Detuning frequency Dfdetuning 44 31 75 k. Hz Klystron power Pkly 940 930 490 k. W RF voltage VC 12 19. 4 MV AC plug power PAC 35 33 MW Y. Ohnishi / KEK 51

Parameters related to vacuum system Bending radius LER HER 16. 31 104. 46 m Bending angle 56. 1 mrad Half Aperture 112 mm Max line power density of SR 27. 77 21. 63 k. W m-1 Max power density of SR 38. 73 35. 00 W mm-2 Critical energy of SR 5. 84 10. 88 ke. V Average photon density 1. 21 x 1019 1. 20 x 1019 photons m-1 s-1 Average gas load 4. 56 x 10 -8 4. 54 x 10 -8 Pa m 3 s-1 m-1 Average pressure 5 x 10 -7 Y. Ohnishi / KEK Pa 52

Loss factor of arc section z = 3 mm nb= 5000 f 0 = 1 x 105 Ib = 10 A k (V/C) Number of Items Total k (V/C) HOM (k. W) Resistive wall 4. 1 x 109 2200 m 8. 9 x 1012 1780 Pumping holes 8. 8 x 105 2200 m 1. 9 x 109 0. 38 Flange 1 x 108 800 8 x 1010 16 Bellows 4 x 109 800 3. 2 x 1012 640 Photon mask 1 x 104 800 8 x 106 0. 0016 Gate valve 3 x 109 16 4. 8 x 1010 9. 6 Movable mask 1 x 1012 16 1. 6 x 1013 3200 Taper 3 x 109 72 2. 2 x 1011 44 BPM - 450 - - IR chamber - - 2. 8 x 1013 5690 Total Y. Ohnishi / KEK 53

Budgetary Process toward Super-KEKB JFY 2009 JFY 2010 JFY 2011 Best Scenario Government Full Budget Review Proposal Council Construction Worst Scenario Good Scenario R&D Budget Proposal Super-KEKB R&D Better Scenario Supplement Budget Super Best Scenario Supplement Budget Y. Ohnishi / KEK 54

Budget Requirement for Coming 5 Years Super-KEKB : (300 -400) M$/construction + 100 M$/operation (-> 60 M$) ILC R&D : ~200 M$/5 years J-PARC : ~90 M$/ year (-> 70 M$) Compact-ERL, LHC-upgrade : ? ? ? Y. Ohnishi / KEK 55