Accelerator Systems Division SuperB Accelerator Overview John Seeman
Accelerator Systems Division Super-B Accelerator Overview John Seeman for the Super-B Study Group PPA Directorate Stanford Linear Accelerator Center Super-B Detector R&D Workshop February 14 -16, 2008
Accelerator Systems Division Topics • • Super-B design Polarization of e. Daphne status KEK-B Crab cavity studies
Accelerator Systems Division Accelerator status • SBF accelerator layout has converged and been defined. • Site constraints suggest 1650 m + polarization component length for a total of 1800 m. • A luminosity of 1 x 1036 with longitudinal polarization of one beam at the interaction point is the primary goal. • Overall parameters have a x 4 luminosity growth potential to the 4 x 1036 level. • Many of the systems use existing components or component designs. • Interaction region has new features. Most of the future design work will be concentrated there.
Possible site in the. Systems Tor Vergata University Accelerator Division close to the Frascati Lab M. Sullivan
Accelerator Systems Division Super-B Territory • The Tor Vergata campus area is owned by the University • The building code allows development with limited bureaucratic complexity (within reason): – – limit number and extension of buildings no shacks or barracks distance from Roman Villa archeological area possible archeological issue with access shafts • Geology is good – Terrain is geologically stable (pozzolanic ash and then tuff) – Water is at about -50 m, no interference with tunnels – Need extensive geological samples to evaluate local stability – Micro seismic data are not available at this time – tunnel depth between 10 and 30 m
Accelerator Systems Division 3 km
Accelerator Systems Division Footprint SPARX Super. B Ring (about 1800 m) Super. B Injector (about 400 m) Roman Villa 100 m Super. B Main Building
Accelerator Systems Division Super-B Tunnels • Tunnel boring machine available with 6. 70 m external diameter. Internal diameter a bit less than 5. 80 m. • Linac will need a double tunnel for the RF and klystrons • Main ring will use a single tunnel with 4 or 6 surface service buildings Division not necessarily useful.
Accelerator Systems Division November 2007 layout Total length ~1800 m Length 280 m Courtesy E. Paoloni, G. Marchiori
Accelerator Systems Division Super. B Parameters (Nov. 2007) (In red the CDR values)
Accelerator Systems Division Rings optical functions LER HER
Accelerator Systems Division Dynamic Aperture With crab sextupoles x-plane • DA represents stability area of particles over many turns • Lifetimes depend on it y-plane xmax = 60 sx no coupling Crab sextupoles reduce DA by 30% ymax = 30 sy full coupling
Accelerator Systems Division Basic concepts
Accelerator Systems Division x b. Y e+ e- 2 Sx/q q 2 Sz*q z 2 Sx Crab waist removes bb betratron coupling Introduced by the crossing angle Vertical waist has to be a function of x: Z=0 for particles at –sx (- sx/2 q at low current) Z= sx/q for particles at + sx (sx/2 q at low current) Crab waist realized with 2 sextupoles in phase with the IP in X and at p/2 in Y
Accelerator Systems Division KEKB Beams distributions at the IP Super. B Beams distributions at the IP Beams are focused in the vertical plane 100 times more than in the present factories, thanks to: - small emittances - small beta functions - large crossing angle - Crab waist Tune shifts and longitudinal overlap greatly reduced KEKB Super. B current 1. 7 A 2. A betay 6 mm 0. 3 mm betax 300 mm 20 mm sigmax ~80 mm ~6 mm sigma y ~3 mm 0, 039 mm Sigma z 6 mm L 1. 7 1034 1 1036
Accelerator Systems Division Final Focus optical functions Crab sextupoles LER: bx* = 35 mm, by* = 220 m HER: bx* = 20 mm, by* = 390 m
Accelerator Systems Division Accelerator parameters [4 x 1036 parameters] Energy (Ge. V) Current (A) No. bunches Bunch spacing (m) Beta x* (mm) Beta y* (mm) Emittance x (nm-rad) Emittance y (pm-rad) Full crossing angle (mrad) LER 4. 0 3. 69 HER 7. 0 3. 69 2502 0. 63 20 0. 2 1. 6 4 34 These parameters constrain or define the IR design M. Sullivan
Accelerator Systems Division
Accelerator Systems Division SR Power Numbers The total power is similar to PEP-II SR power in QD 0 (k. W) for beam currents of 1. 44 A HER and 2. 5 A LER No QD 0 offsets Super. B PEP-II 3 A on 1. 8 A Incoming HER 41 4 49 Incoming LER 28 1 16 Outgoing HER 41 93 49 Outgoing LER 28 55 16 138 153 130 Total
Accelerator Systems Division “Foot print” shape preferred
Accelerator Systems Division IP Spin Rotator layout
Accelerator Systems Division Example of Injected Polarized Electrons Polarization Components from the SLC at SLAC Polarized Photo-Gun 120 Hz, 87% 2 x 5 x 10^10/pulse Spin manipulators SLC IP Located at the Stanford Linear Accelerator Center Polarization equipment ready for reuse!
Accelerator Systems Division Polarization Comments • Long polarization times and short beam lifetimes indicates a need to continuously inject polarized electrons in the vertical plane. • There are several possible IP spin rotators. – Solenoids look better at present. • Expected longitudinal polarization at the IP of about 87%(inj) x 97%(ring)=85%(effective).
Accelerator Systems Division PEP-II Arc Section Usable PEP-II components for Super-B Magnets (Over 1500) Vacuum chambers (4400 m) RF systems (15 stations, 28 cavities) Power supplies Bunch-by-bunch feedback systems Diagnostics Instruments Injection septa and kickers Supports
Accelerator Systems Division B-Factory RF Klystrons and Cavities •
Accelerator Systems Division Where to go from here for Super-B? • Complete next round of studies for: – Updated design document. – Dynamic aperture studies. – Vibration and stability tolerances. – IR layout (+/- 50 m) – Injection conditions – Polarization rotation hardware
Accelerator Systems Division Raimondi: Status of Crab Waist Studies at Daphne (Frascati) • • • Installation of the crab-waist IR finished in November 2007. Present currents: 950 m. A e- x 400 m. A e+ Ring optics (betas) are well matched (<5%). Betas y/x = 9 mm/0. 25 m 6 -7 mm/0. 25 m after detector is installed. X-Y coupling ~0. 6% Collisions are well established. Crab sextupoles are successfully tested to 40% value with beam. Ring impedance better (40% lower). e- instabilities threshold up by x 2. e+ instability threshold down by x 2. Luminosity looks ok but needs to be cross checked. Run until ~end July. • Overall the situation looks good! (February 7, 2008)
Accelerator Systems Division KEKB MAC: Status of KEKB Crab Cavity Studies • Crab cavities work well. • Beam “crabs” properly all around the ring. • At low current the specific luminosity is higher as predicted (geometric gain). • At high current some beam-beam force removes the gain in specific luminosity. • At high currents the beam lifetimes are reduced. • Studies have been going on for a year and will likely continue for the next year. (December 2007)
Accelerator Systems Division Crab RF system •
Accelerator Systems Division Crab cavities in the KEKB tunnel LER HER
Accelerator Systems Division Overview of crab cavity operation High-current Low-current collision tuning Warm up to room temperature Low-current collision tuning High-current Summer shut down Physics run with Crab
Accelerator Systems Division Specific Luminosity L 18 H 24 (3/11, 4/3) y~0. 089 (4/10, 4/19) L 24 H 24 (3/29, 4/1) L 24 H 29 (6/14) 22 mrad crossing L 18 H 24
Accelerator Systems Division beam-beam simulation (Ib. L/Ib. H = 7/4) y~0. 089
Accelerator Systems Division
Accelerator Systems Division Beam-beam parameter with crab crossing (simulation) beam-beam parameter : experiments
Accelerator Systems Division Machine Parameters (Nov. 28 2007) This is almost equal to the value achieved at collision with longer bunch spacing. Effects of high current and short spacing are not so big?
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