SuperB Injector (2) R. Boni, INFN-LNF - on behalf of the “Injector Study Group” SuperB Mini-MAC, Frascati 16-17 July, 2008 D. Alesini, R. Boni, F. Marcellini, M. Preger, P. Raimondi, C. Vaccarezza, INFN-LNF. J. Seeman, SLAC SuperB

Preliminary conclusions of the Biodola-Meeting (31/05-04/06, 2008) for the SB Injector… S-band, 100 Hz, room-temperature linac, recycling (a.m.a.p.) PEP2 hardware (i.e. damping rings, dipoles, TL, etc …) 2) Use of Polarized Gun Use of Damping Rings for both e- and e+ beams The SB-Linac is a quasi-continuous injection machine: topping-up filling time: ≈ 12 sec per ring per min. ≈ 24 sec per min. SuperB Mini-MAC, Frascati 16-17 July, 2008

GOAL Talk Summary To reduce the topping-up injection time ,.. … that is … to increase the average luminosity Talk Summary 1. Injector layout e+/e- injection process (damping rings & by-pass line) Electron gun Laser system 5. Kickers 6. Parameters SuperB Mini-MAC, Frascati 16-17 July, 2008

INJECTOR SCHEMATIC LAYOUT e+ 4 Gev e- 7 Gev It is proposed to contemporary inject electrons and positrons in the respective rings. This can be carried out by means of simultaneous acceleration of both e- and e+ along the linac . A reduction of the rings filling time can be therefore achieved. SuperB Mini-MAC, Frascati 16-17 July, 2008

e+/e- INJECTION PROCESS 1 μsec SLED RF PULSE ✦ 2 bunches, ≈ 50 nsec apart, are emitted by a SLC-type polarized electron gun, illuminated by laser pulses at the rep. rate of 100 Hz. ✦ the bunches have different charge (1 nC and 0.1 nC), due to different laser beam energies. ✦ the lower charge bunch induces weaker wake-fields in the accelerating sections, therefore it travels ahead. ✦ leading and trailing bunches are accelerated down the 1.2 GeV Linac [three bunches are accelerated simultaneously down the SLC injector ….] SuperB Mini-MAC, Frascati 16-17 July, 2008

…… e+/e- INJECTION PROCESS ……cont.d ✦ the leading low-charge bunch is injected, by a stripline kicker, into the e- DR; ✦ meanwhile, an electron bunch is extracted from the DR and injected into the linac by a kicker, 50 nsec before the arrival of the high-charge bunch; ✦ the trailing high-charge bunch goes straight into the 2 GeV linac and is sent to the positron target. ✦ the previous bunch, in turn, will be extracted after 10 msec (3 damping times) and injected into the linac, 50 nsec before the arrival of the next high-charge bunch. SuperB Mini-MAC, Frascati 16-17 July, 2008

✦ Spin Rotator is needed to avoid depolarization in the electron DR …… e+/e- INJECTION PROCESS ……cont.d ✦ Spin Rotator is needed to avoid depolarization in the electron DR K K ✦ Spin direction is longitudinal when exits the Gun ✦ Spin direction must be perpendicular to the horizontal plane when the bunch enters the DR SuperB Mini-MAC, Frascati 16-17 July, 2008

Kickers timing t < ΔT ≈ …… e+/e- INJECTION PROCESS ……cont.d 20 ÷ 30 nsec t < ΔT Kickers timing t ≈ SuperB Mini-MAC, Frascati 16-17 July, 2008

BY-PASS LINE [ e+/e- INJECTION PROCESS ……] ✦ the low-charge bunch is deflected, with a stripline kicker, into the by-pass line and re-injected into the linac with a delay Δ; ✦ meanwhile, a positron bunch, generated by the PS, travels through a S-band section up to rejoin with the by-passed e- bunch. L by-pass BY-PASS length = L + Δ 50 nsec - Δ SuperB Mini-MAC, Frascati 16-17 July, 2008

… example of by-pass configuration …. BY-PASS LINE [ e+/e- INJECTION PROCESS ……] …cont.d … example of by-pass configuration ≈ L ≈ 23÷24 mt. with Δ ≈ 10 nsec BPL ≈ L + 3 mt. SuperB Mini-MAC, Frascati 16-17 July, 2008

… alternative by-pass configuration: …. BY-PASS LINE [ e+/e- INJECTION PROCESS ……] …cont.d … alternative by-pass configuration: ✦ to avoid depolarization if the by-pass introduces a degradation. ≈ SuperB Mini-MAC, Frascati 16-17 July, 2008

… alternative by-pass configuration: …. BY-PASS LINE [ e+/e- INJECTION PROCESS ……] …cont.d … alternative by-pass configuration: ✦ low charge bunches go straigth through a 5 mm hole of the positron target ✦ high-charge bunches move transversely ≈ 1 cm with a pulsed bump and hit the target ✦ the produced e+ move back to the center line before the capture section capture section ≈ SuperB Mini-MAC, Frascati 16-17 July, 2008

…… e+/e- INJECTION PROCESS ……cont.d ✦ the trailing positron bunch is kicked into the e+ DR and damps for 10 msec; ✦ meanwhile, a damped positron bunch is kicked-out the DR and injected into the linac, 40 nsec behind the electron bunch; ✦ both e- and e+ bunches are accelerated down the 3 GeV linac, up to 7 and 4 GeV respectively. SuperB Mini-MAC, Frascati 16-17 July, 2008

PEP2 Damping Rings SuperB Mini-MAC, Frascati 16-17 July, 2008 A 1.2 CeV DAMPING RING COMPLEX FOR THE STANFORD LINEAR COLLIDER, G. E. FISCHER, W. DAVIES-WHITE, T. FIEGUTH, H. WIEDEMANN Stanford Linear Accelerator Center SLAC-PUB 3170, July 1983 SuperB Mini-MAC, Frascati 16-17 July, 2008

IMPORTANT REQUIREMENT for By-Pass and DR TL’s To position the bunches at the correct accelerating phase, the length of BP and DR TL’s must be finely tuned (± 5mm, i.e. 30 psec) 175 psec e- e+ SuperB Mini-MAC, Frascati 16-17 July, 2008

ELECTRON GUN laser light input 7 x 1010 electrons in 1 nsec q ≈ 11 nC Based on the SLC polarized electron source: ✦ DC gun, ✦ GaAs derivative photocathode, ✦ 800 nm laser, ✦ SHB bunching, laser light input GaAs photocathode SLC polarized Gun - 120 kV 7 x 1010 electrons in 1 nsec q ≈ 11 nC I ≈ 11 A The Polarized Electron Gun for the SLC D. C Schultz, J. Clendenin, J. Frisch, E. Hoyt, L. Klaisner, M. Woods, D. Wright, M. Zolotorev Stanford Linear Accelerator Center, SLAC-PUB-5768, March 1992 SuperB Mini-MAC, Frascati 16-17 July, 2008

… ELECTRON GUN .. cont.d ✦ 2 bunches, 50 nsec apart, are emitted by a SLC-type polarized electron gun, illuminated by laser pulses, followed by SHB systems; ✦ RF guns with GaAs photocathode can be also considered; no SHB needed; [J.Clendenin et al., SLAC-PUB-11526, Oct. 2005] SuperB Mini-MAC, Frascati 16-17 July, 2008

LASER SYSTEM Feasible … !! ✦ the bunches have different charge (1 nC and 0.1 nC), due to different laser beam energies. Feasible … !! Laser oscillator Transport PBS PBS Laser amplifier P-pol 50 ns ell-pol QWP 50 ns delay S-pol PBS = polarizer beam splitter (reflects s-polarization and transmits p-polarization) QWP = quarter wave plate (produces an elliptical pol. to control the two pulses intensity) ( courtesy C. Vicario ) SuperB Mini-MAC, Frascati 16-17 July, 2008

POSITRON SOURCE beam power = E . N . e- . fHz NLC PS FRASCATI PS 20.2 Int.l Conf. on High Energy Particle Accelerators, 1995 FRASCATI PS beam power = E . N . e- . fHz Parameter SLC-94 NLC-II SuperB E (GeV) 30 6.22 3 N of particles 3.5 x 1010 113 x 1010 6 x 1010 Rep.rate (Hz) 120 100 Beam power (kW) 20.2 134 2.9 SuperB Mini-MAC, Frascati 16-17 July, 2008

CONVENTIONAL DEVICE … POSITRON SOURCE … cont.d High Gradient (25-27 MV/m) S-band Capture Section with focusing solenoids Adiabatic matching device + flux concentrator of ~ 6÷7 T peak field CONVENTIONAL DEVICE SuperB Mini-MAC, Frascati 16-17 July, 2008

Injection-Extraction Kickers ✦ The process of the injection/extraction of e-/e+ bunches into/from the DR’s/BP requires the use of stripline kickers. ✦ High performance fast kickers have been already developed (DAFNE) or designed (ILC). ✦ In DAFNE, fast stripline kickers allow to inject the bunches without perturbing the adjacent ones. 45 kV 5 ns SuperB Mini-MAC, Frascati 16-17 July, 2008

… injection-Extraction Kickers …cont.d 30 nsec ✦ The SuperB-Injector does not need very fast kickers. Kicker pulses with 10÷15 nsec rise/fall time and 10 nsec flat-top should be OK for the purpose. Kickers parameters: scaling from DAFNE (at constant deflection) DAFNE 510 MeV Deflection Θ 5 mrad (5mm @ 1 m) HV 45 kV Kicker length L 1mt. Plates distance d 5 cm Pulse width 5 nsec Θ Lm·VkV EGeV·dcm DEFLECTION 10 Hz SuperB Injector 1.2 GeV 3 GeV Deflection Θ 5 mrad 5 mrad HV 45 kV 45 kV Kicker length L 2.4 mt 6 mt. Plates distance d 5 cm 5 cm Pulse witdh ≈ 30 nsec ≈ 30 nsec 100 Hz SuperB Mini-MAC, Frascati 16-17 July, 2008

… injection-Extraction Kickers …cont.d Input ports Output ports (LOAD) Strip ceramic supports BEAM Tapered stripline Elliptical cross section HV feedthrough DAFNE KICKERS SuperB Mini-MAC, Frascati 16-17 July, 2008

RF Linacs Layout e- > 7 GeV e+ > 4 GeV 16 RF Stations SuperB Mini-MAC, Frascati 16-17 July, 2008

RF Linac Main Specs. N° of RF power stations 36 N° of accelerating sections 108 Klystron output peak power @ 100pps 60 MW (4 μsec) Input RF power per acc. section 50 MW (1 μsec) Average accelerating gradient [unloaded] 23.5 MV/m Total average kly RF power 800 kW Total wall-plug modulator power ≈ 3 MW Total wall-plug Injector power (incl. DR’s) ≈ 6 MW Total injector length ≈ 400 m. Total RF active length 324 m. SuperB Mini-MAC, Frascati 16-17 July, 2008

e-/e+ Production Capability Main rings particles/bunch nb = 5.5.1010 Particles injected for topping-up at 90% of peak luminosity ni = 5.5.109 Efficiency of e+ transport from PS η+ ≈ 0.9 N. of positrons after PS N+ = 6.1.109 N. of electrons at the PS (e-/e+ conversion efficiency @ 3 GeV ≈ 10%) N-PS = 6.1.1010 q-PS = 10 nC Electron transport efficiency η- ≈ 0.9 N. of e-/bunch from the Gun for e+ production N-G = 6.8.1010 q-G = 11 nC Gun current/bunch 11 A (1 nsec) “LER + HER” re-filling time (1251 bunches per ring) ≈ 12 sec Time between injections @ ≈ 90% of Lpeak ≈ 42 sec SuperB Mini-MAC, Frascati 16-17 July, 2008

! t t … about the topping-up time …. ≈ 12 sec Linac RF Rings RF = 6 DR’s RF = 4 main rings filling 4.2 nsec The simultaneous injection of more than 2 bunches at a time … can be studied. It would allow to reduce even more the re-filling time. DR’s filling t ≈ 6 sec ≈ 4.2 sec The LASER system is more tricky but still feasible ! SuperB Mini-MAC, Frascati 16-17 July, 2008

e-/e+ production with injection of “ twin bunches” 50 nsec Main rings particles/bunch nb = 5.5.1010 Particles injected for topping-up at 95% of peak luminosity ni = 2.7.109 Electron Gun current/shot 5.5 A (1 nsec) “LER + HER” re-filling time (1251 bunches per ring) ≈ 6 sec Time between injections @ ≈ 95% of Lpeak ≈ 21 sec SuperB Mini-MAC, Frascati 16-17 July, 2008

Established and firm points …… ✦ Room-temperature linac ✦ S-band @ 2.856 GHz – 100 Hz, with SLAC-type acc. structures ✦ 60 MWpeak RF power sources ✦ Damping Rings for both electrons and positrons ✦ e+ production @ 3 GeV ✦ Use of a SLC-like polarized gun SuperB Mini-MAC, Frascati 16-17 July, 2008

Matters requiring R&D and/or “Study-Groups” ✦ DR’s injection-extraction : kickers, spin-rotators, TL length tuning,… ✦ By-pass line : kickers, length tuning ✦ Electron Gun : use a copy of the SLC gun or develope a new one ? ✦ Laser system ✦ TIMING & BEAM DIAGNOSTICS SuperB Mini-MAC, Frascati 16-17 July, 2008