1. 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

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

3. 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.

4. Possible site in the Tor Vergata University close to the Frascati Lab
M. Sullivan

5. 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

6. 3 km

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

8. 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.

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

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

11. Rings optical functions
LER
HER

12. 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%

13. Basic concepts

14. 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

15. 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 1036
SuperB Beams distributions
at the IP

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

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

19. 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
Incoming LER
Outgoing HER
Outgoing LER
Total

20. “Foot print” shape preferred

21. IP Spin Rotator layout

22. 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!

23. 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).

24. 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

25. B-Factory RF Klystrons and Cavities

26. 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

27. 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)

28. 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)

29. Crab RF system

30. Crab cavities in the KEKB tunnel
LER
HER

31. 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

32. 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

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

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

36. 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?