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

Topics Super-B design Polarization of e- Daphne status KEK-B Crab cavity studies

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 1x1036 with longitudinal polarization of one beam at the interaction point is the primary goal. Overall parameters have a x4 luminosity growth potential to the 4x1036 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 Tor Vergata University close to the Frascati Lab M. Sullivan

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 -50m, 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 30m

3 km

Footprint SuperB Ring (about 1800m) SPARX SuperB Injector (about 400m) Roman Villa 100m SuperB Main Building

Super-B Tunnels Tunnel boring machine available with 6.70m external diameter. Internal diameter a bit less than 5.80m. 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.

November 2007 layout Total length ~1800 m Length 20 m Length 280 m Courtesy E.Paoloni, G. Marchiori

SuperB Parameters (Nov. 2007) (In red the CDR values)

Rings optical functions LER HER

Dynamic Aperture With crab sextupoles DA represents stability area x-plane xmax = 60 sx no coupling DA represents stability area of particles over many turns Lifetimes depend on it y-plane ymax = 30 sy full coupling Crab sextupoles reduce DA by 30%

Basic concepts

Vertical waist has to be a function of x: bY e- e+ 2Sx/q q 2Sz*q z 2Sz 2Sx 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/2q at low current) Z= sx/q for particles at + sx (sx/2q at low current) Crab waist realized with 2 sextupoles in phase with the IP in X and at p/2 in Y

KEKB Beams distributions SuperB Beams distributions 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 Beams distributions at the IP KEKB SuperB current 1.7 A 2. A betay 6 mm 0.3 mm betax 300 mm 20 mm sigmax ~80mm ~6mm sigma y ~3mm 0,039mm Sigma z L 1.7 1034 1 1036 SuperB Beams distributions at the IP

Final Focus optical functions Crab sextupoles LER: bx* = 35 mm, by* = 220 m HER: bx* = 20 mm, by* = 390 m

Accelerator parameters [4x1036 parameters] LER HER Energy (GeV) 4.0 7.0 Current (A) 3.69 3.69 No. bunches 2502 Bunch spacing (m) 0.63 Beta x* (mm) 20 20 Beta y* (mm) 0.2 0.2 Emittance x (nm-rad) 1.6 1.6 Emittance y (pm-rad) 4 4 Full crossing angle (mrad) 34 These parameters constrain or define the IR design M. Sullivan

SR Power Numbers The total power is similar to PEP-II SR power in QD0 (kW) for beam currents of 1.44A HER and 2.5A LER No QD0 offsets SuperB PEP-II 3A on 1.8A Incoming HER 41 4 49 Incoming LER 28 1 16 Outgoing HER 41 93 49 Outgoing LER 28 55 16 Total 138 153 130

“Foot print” shape preferred

IP Spin Rotator layout

Polarization Components from the SLC at SLAC Example of Injected Polarized Electrons Polarization Components from the SLC at SLAC Polarized Photo-Gun 120 Hz, 87% 2 x 5x10^10/pulse Spin manipulators SLC IP Located at the Stanford Linear Accelerator Center Polarization equipment ready for reuse!

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).

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 PEP-II ring

B-Factory RF Klystrons and Cavities

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

Raimondi: Status of Crab Waist Studies at Daphne (Frascati) Installation of the crab-waist IR finished in November 2007. Present currents: 950 mA e- x 400 mA 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 x2. e+ instability threshold down by x2. Luminosity looks ok but needs to be cross checked. Run until ~end July. Overall the situation looks good! (February 7, 2008)

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)

Crab RF system

Crab cavities in the KEKB tunnel LER HER

Overview of crab cavity operation High-current High-current Physics run with Crab Low-current collision tuning Low-current collision tuning Summer shut down Warm up to room temperature

Specific Luminosity y~0.089 L18 H24 (3/11, 4/3) L18 H24 (4/10, 4/19) y~0.089 L24 H24 (3/29, 4/1) L24 H29 (6/14) 22mrad crossing L18 H24

beam-beam simulation (IbL/IbH = 7/4) y~0.089

Beam-beam parameter with crab crossing (simulation) : experiments

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?