Parameters of a Super-B-Factory Design Page: 1 of 3
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SLAC-PUB-11726
PARAMETERS OF A SUPER-B-FACTORY DESIGN*
J. Seemant, Y. Cai, S. Ecklund, J. Fox, S. Heifets, N. Li, P. McIntosh,
A. Novokhatski, M. Sullivan, D. Teytelman, U. Wienands
SLAC, Menlo Park, CA 94025, USA
M. Biagini, INFN, Frascati, ItalyAbstract
Parameters are being studied for a high luminosity eCe-
collider operating at the Upsilon 4S that would deliver a
luminosity in the range of 7 to 10 x 105/cm2/s. Particle
physics studies dictate that a much higher luminosity
collider than the present B-Factory accelerators will be
needed to answer future new key physics questions. The
success of the present B-Factories, PEP-II and KEKB, in
producing unprecedented luminosity with very short
commissioning times has taught us about the accelerator
physics of asymmetric ee- colliders in a new parameter
regime. Such a collider could produce an integrated
luminosity of 10,000 fb1 (10 ab') in a running year. A
Super-B-Factory [1-8] with 30 to 50 times the
performance of the present PEP-II accelerator would
incorporate a higher frequency RF system, lower
impedance vacuum chambers, higher power synchrotron
radiation absorbers, and stronger bunch-by-bunch
feedback systems. The present injector based on the
SLAC linac needs no improvements and is ready for the
Super-B-Factory.
PARAMETERS
The design of a 7 to 10 x10 cm 2s e e collider
combines an extension of the design of the present B
Factories with a few new ideas and special
circumstances to allow improved beam parameters to be
achieved. The luminosity L in an ee- collider that has a
limited vertical tune shift , with flat beams is given by
the standard expressionL = 2.17x1034(1+r)nf jmb CM2sec-
(1)
where I is the bunch current (amperes), n is the number
of bunches, E is the beam energy (GeV), r is the vertical
to horizontal emittance ratio (-0.01) and ,* is the
vertical beta function (cm) at the collision point. The
luminosity gain of the Super B Factory comes from the
increase of the beam currents by about a factor of five,
lowering ,* about a factor of four, and increasing the
beam-beam tune shifts about 80%. The resulting gain is
about a factor of 30 to 50 over that of the present B
Factories. In addition, due to continuous injection with
the luminosity always near the maximum as shown
*Supported by US DOE contract DE-AC02-76SF00515.
tseemanA~slac. stanford.edusuccessfully in the present B-Factories, the overall
integrated luminosity per unit time of the Super B
Factory is expected to be 10 ab' per year with a peak
luminosity of 7x105 cm2s . The parameters of a
representative ee colliders at SLAC at 7 x1035 cm2s
are listed in Table 1. The PEP-II tunnel at SLAC is an
excellent site for this collider.
The beam energies are 8 GeV for the high-energy ring
(HER) and 3.5 GeV for the low-energy ring (LER).
Lowering the high-energy ring energy from the present 9
GeV reduces the overall synchrotron radiation load on
the RF system and raises the instability thresholds for the
low energy beam. The e and e may be exchanged if
need be as either particle can be stored in either ring
using the versatile SLAC injector. The linac can provide
low emittance beams with 80 Hz of e- and 20 Hz of e+.
Table 1: Parameters for a Super B Factory at 952 MHz
Parameter LER HER
Energy (GeV) 3.5 8
RF frequency (MHz) 952 952
Vertical tune 72.64 56.57
Horizontal tune 74.51 58.51
Current (A) 15.5 6.8
Number of bunches 6900 6900
Ion gap (%) 1.2 1.2
RF klystron/cavity 24/24 18/18
RF volts (MV) 30 23
py* (mm) 1.7 1.7
P* (cm) 14 14
Emittance (x/y) (nn) 24/0.28 24/0.28
6z (mm) 1.8 1.8
Hourglass-X-angle 0.81 0.81
factor
Crossing angle(mrad) 14 14
IP Horiz. size (gm) 58 58
IP Vert. size (gm) 0.7 0.7
Horizontal X 0.12 0.12
Vertical 0.12 0.12
Lumin. (x1034/cm2/s) 70 70Contributed to Particle Accelerator Conference (PAC 05), 16-20 May 2005, Knoxville, TN
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Seeman, J.; Cai, Y.; Ecklund, S.; Fox, J. D.; Heifets, S. A.; Li, N. et al. Parameters of a Super-B-Factory Design, article, March 3, 2006; Menlo Park, California. (https://digital.library.unt.edu/ark:/67531/metadc875049/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.