Positron Sources of Next generation B-factories (SuperKEKB, SuperB) POSIPOL-2011 workshop in Beijing, 2011.08.28 Positron Sources of Next generation B-factories (SuperKEKB, SuperB) Takuya Kamitani (KEK) with helps of A. Variola and S. Guiducci on SuperB positron source information

KEKB view from sky Belle detector 8.0 GeV HER (e-) 3.5 GeV LER (e+) circ. 3.0 km ex-TRISTAN tunnel Injector linac POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperKEKB overview 7.0 GeV HER (e-) 4.0 GeV LER (e+) from a slide by M. Maszawa at IPAC 2010 in Kyoto POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperB Layout 4.2 GeV LER (e-) 6.7 GeV HER (e+) circ. 1.26 km from a slide by M. Biagini at SuperB workshop in Elba, 2011 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperB site plan Tor Vergata from a slide by M. Biagini at SuperB workshop in Elba, 2011 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

machine parameter comparison SuperKEKB SuperB (Frascati) particle type e- e+ beam energy GeV 7.0 4.0 4.2 6.7 stored current A 2.6 3.6 2.5 1.9 bunch intensity x1010 6.5 9.0 5.1 # of bunches 2500 978 circumference m 3016 1258 emittance ex/ey nm/pm 5.1/14 3.2/13 2.5/6.2 2.0/5.0 beam lifetime min 10 4.5 polarization - 80 % luminosity cm-2s-1 8 x 1035 10 x 1035 SuperB parameters from reports by S. Guiducci & A. Variola at SuperB workshop in Elba, 2011 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

requirements on beam injection SuperKEKB SuperB (Frascati) particle type e- e+ beam energy GeV 7.0 4.0 4.2 6.7 beam intensity nC/pulse 10 8 0.78 0.64 # bunches/pulse 2 1 (5 Max) beam repetition Hz total 50 50 for main rings emittance gex/gey mm 20/20 98/7 45/TBD 54/9 energy spread 1s % 0.08 0.07 0.14 0.11 for damping ring - 3000 2200 energy spread ( (hard-edge) 1.5 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

Injectors SuperKEKB injector SuperB injector high current gun 1.1 GeV Damping Ring circ. 136 m low emittance RF gun Bunch Compressor 50 Hz (e+ or e-) 3.5 GeV 10nC x 2 (prim. e-) 5nC x 2 (inj. e-) Energy-spread Compression System 4.0 GeV e+ 4nC x 2 S-band linac ECS e+ target & 120 MeV L-band capture section 7.0 GeV e- 5nC x 2 0.6 GeV 10nC SuperB injector L-band linac 300 MeV CAPTURE SECTION THERMIONIC GUN 0.7 GeV PC 0.6 GeV SHB S-band (TM020) +L-band 1.0 GeV Damping Ring circ. 51 m combiner DC dipole e+ 6.7 GeV e+ 0.6nC BUNCH COMPRESSOR 50 Hz (e+) + 50 Hz (e-) 5.7 GeV e+ 4.0 GeV e- B graded S band Sections 50 MeV POLARIZED SLAC GUN SHB 0.2 GeV e- 4.2 GeV e- 0.8nC from a report by A. Variola at SuperB workshop at Elba, 2011 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperKEKB Capture section KEKB e+ capture section QWT system (2.0 T x45mm + 0.4 T x8m) air-core pulse coil DC solenoids KLY1 (S-band) -> Acc1, Acc2 1m-long 12 MV/m, aper 2a = 27 -> 25 mm KLY2 (S-band) -> Acc3, Acc4 2m-long 10 MV/m, aper 2a = 25 -> 21 mm beam energy at capture section exit : 80 MeV N(e+)/N(e-) = 10 % at 3.5 GeV linac-end N(e+)/N(e-)/E(e-) = 2.5 %/GeV SuperKEKB e+ capture section AMD system (6.0 T x200mm + 0.4 T x15m) flux concentrator DC solenoids beam energy at capture section exit : 120 MeV Deceleration mode L-band -> Acc1, Acc2 2m-long 10 MV/m, aper 2a = 39 -> 35 mm S-band -> Acc3~Acc6 2m-long 10 MV/m, aper 2a = 32 -> 30 mm L-band -> Acc1, Acc2 2m-long 10 MV/m, aper 2a = 39 -> 35 mm L-band -> Acc3~Acc6 2m-long 10 MV/m, aper 2a = 39 -> 35 mm to be upgraded in a few years N(e+)/N(e-) = 65 % at 1.1 GeV DR N(e+)/N(e-)/E(e-) = 19 %/GeV POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperB capture section 34 meter AMD system (6.0 T x200mm + 0.5 T x34m) DC solenoids beam energy at capture section exit : 333 MeV Deceleration mode L-band -> 3m-long x10 (13 MV/m), aper 2a = 40 mm S-band TM020 -> 3m-long x2 (22.5 MV/m), aper 2a = 30 mm + L-band -> 3m-long x8 (13 MV/m), aper 2a = 40 mm N(e+)/N(e-) = 33 % at 1.0 GeV (total yield) N(e+)/N(e-) = 19 % at 1.0 GeV (after dE/E<1.0% cut) N(e+)/N(e-)/E(e-) = 32 %/GeV POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperB TM020 cavity from a slide by A. Variola at SuperB workshop in Elba, 2011 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperB capture simulation Deceleration phase ! from a slide by A. Variola at SuperB workshop in Elba, 2011 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperKEKB e+ linac beam optics Optics calculation by N. Iida Many Quadrupoles are wound outside the accelerator structures. Capture section exit End of Sector-2 FODO system triplet system Start N(e+)/N(e-) Slit: 42mm S-band large aper. φ30 S-band normal aper. φ20 S-band：Separated Quads φ20 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

Satellite bunch elimination (SuperKEKB) satellite bunches generated in capture section make radiation problem in DR injection due to coprime (5:11) frequency relation of L-band (1298 MHz) and downstream S-band (2856MHz), most of L-band satellites are eliminated during S-band acceleration only S-band case (loss = 0.40%) L + S-band combination case (loss = 0.05%) particles outside the separatrix are lost at DR injection POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

SuperB beam optics from a slide by A. Variola at SuperB workshop in Elba, 2011 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

ECS & BCS (SuperKEKB) Bunch Energy-spread Compression Compression System Energy-spread Compression System BCS reduce bunch-length of e+ extracted from DR ECS reduce energy-spread of e+ entering DR energy gradient by RF field + non-isochronous arc non-isochronous arc + energy correction by RF field Vc = 37 MV (L-band) R56 = -1.05 m compression 1/9 R56 = -0.61 m Vc = 41 MV (S-band) compression 1/3 schematic view scale is not precise ! POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

Energy equalization idea This idea is proposed for linear colliders, but still in conceptual consideration level and not for SuperB baseline design. from a slide by A. Variola at SuperB workshop in Elba, 2011 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

e+ capture animation (SuperKEKB) from target to capture section exit (120 MeV) Acceleration phase mode in capture section Deceleration phase mode in capture section Energy (MeV) Energy (MeV) longitudinal position (mm) longitudinal position (mm) Capture efficiency is comparable in either mode. POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

e+ acceleration (SuperKEKB) during S-band linac acceleration (120 -> 1100 MeV) Acceleration mode in CS Deceleration mode in CS Relative Energy Relative Energy longitudinal position (mm) longitudinal position (mm) POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

energy-spread compression (SuperKEKB) in Energy-spread compression system Acceleration mode in CS Deceleration mode in CS Relative Energy Relative Energy longitudinal position (mm) longitudinal position (mm) Deceleration phase mode is favorable in viewpoint of energy tail distribution. POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

Flux concentrator BINP-type (SuperKEKB) BINP prototype field measurement & high-power operation test performed at KEK Breakdown problem over 7 Tesla relating to a flux disturbance by a target or a gap to vacuum chamber Investigation of the magnet will be performed at BINP by disassembl-ing. Beam test at KEK positron station cancelled by the 3.11 earthquake damage of KEKB linac POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

Flux concentrator SLAC-type (SuperKEKB) SLAC-type of conventional flux concentrator is also considered as a candidate due to the proven stability in long-term operation. Discussion will be started with IHEP people who have recent experience of fabrication and operation of a SLAC-type of flux concentrator. from drawings of SLAC-type flux concentrator fabricated at IHEP POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

Super-Conducting solenoid (SuperKEKB) As an alternative focusing device, superconducting solenoid is considered. Quenching due to heating by radiation from target will be a obstacle in operation. Beam irradiation tests are performed to evaluate quenching limit. No quench in 10 minutes at 3.2 Tesla with irradiation of 1.7 GeV e- beam of 6nC x2 x 49 Hz. Cost of refrigerator will be a problem. 1.7 GeV e- beam 6nC x2 x 49 Hz POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

L-band components (SuperKEKB) First L-band accelerating structure completed in 2010 March. First L-band 30 MW klystron is in conditioning operation. The accelerating structure will be tested in KEKB linac tunnel in 2012 April after constructing a test bench. Collinear dummy load is under consideration to avoid output coupler and enable smaller DC solenoid aperture size. RF frequency 1298 (=2856 x5/11) MHz traveling-wave structure constant gradient (2/3)pi phase advance per cell structure length 2.2 meter disk aperture 2a = 39.4 -> 35.0 mm field strength 10 MV/m attenuation constant tau = 0.26 POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

Summary SuperB needs higher energy (6.7GeV) positrons than SuperKEKB (4.0GeV) due to opposite energy asymmetry. SuperKEKB needs higher positron bunch intensity due to (x2.4) longer circumference and (x1/2) lower pulse repetition. SuperKEKB uses higher energy (3.5GeV) primary electrons than SuperB (0.6GeV). SuperB uses longer (34m) capture section than SuperKEKB (15m) for higher e+ capture efficiency. SuperKEKB uses L-band capture section + S-band linac, SuperB uses (S-band TM020 + L-band cavities) in the capture section + L-band linac. SuperKEKB coprime frequency relation (5:11) is useful for satellite bunch elimination. SuperKEKB uses Energy-spread Compression System (non-zero R56 arc & supplementary accelerator) to improve DR injection efficiency. Detailed design study and R&D are ongoing in the both projects. POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani