Super-B Factory in a “4400m” Tunnel John T. Seeman SBF Workshop at Frascati March 16, 2006

Motivation Use an existing tunnel and injector (2200 m) Use existing RF system (476 MHz) Make two rings for each beam in the tunnel First ring provides damping and low emittances in x, y, and z planes Second ring is for bunch compression by a factor of about x6 Second ring has an ILC final focus for collisions Collide every bunch on every turn (really two turns= 4400 m) Collide 4 x 7 GeV with bunches 1 m apart Keep bunch charges and beam currents at about present or soon-to-be levels. Keep beam-beam parameters at the present PEP-II / KEKB levels (or very nearly)  Do not need short damping times which saves AC power!

PEP-II Parameters C = 2200 m

Super-KEKB Parameters C = 3016 m

crossing angle optional Raimondi Feb 2006 ILC ring with ILC FF ILC Compressor Colliding every turn crossing angle optional C = 6000 m Decompressor Decompressor FF FF IP Compressor Compressor

Layout of One Ring: Other Ring is the Reverse! Linac injector Bunch compressor Bunch expander Damping ring = 2200 m Final Focus IP And Detector Reverse Final Focus

Super-B-Factory in a 4400 m Tunnel 0.4 mm

SUPER-B Factory in a 4400 m tunnel 0.3 mm

SBF as shown in Traditional Ring Collider Parameters Emittances = 12.x1.5 nm

Approximate AC Power PEP-II (2200 m) (1 ring LER and HER) RF AC Power LER at 3.1 GeV = 1 MeV/turn x 4 A x 2 = 8 MW RF AC Power HER at 9.0 GeV = 3.6 MeV/turn x 2 A x 2 = 14.5 MW Total RF AC power = 22.5 MW. Super-B factory (4400 m) (2 rings LER and HER) RF AC Power LER at 4 GeV ~ 1.8 MeV/turn x 4 A x 2 x 2= 29 MW RF AC Power HER at 7.0 GeV ~ 2.2 MeV/turn x 2.5 A x 2 x 2= 22 MW Total RF AC power = 51 MW.

First Look at Bunch Compression With a long damping time, each ring has a natural energy spread of about 2.5E-4. The natural bunch lengths will be about 3 mm. The desired bunch length at the IP is about 0.5 mm. The needed compression is a factor of 6. The energy spread at the collision point is then about 1.3 E-3 for both beams. Probably ok. (?) The RF compressors are likely ~1.43 GHz (3 x 476) with 65 MV and 110 MV with lengths about 10 and 20 m of SC structures but use very little power.

Conclusions Colliding every turn helps with the collision rate. The ILC final focus will allow very small by* = 0.4 mm. The beam emittances are not very small (12 nm x 1.5 nm). Bunch compressors are needed to shorten the bunch. Having two “loops” per ring in a tunnel allows adequate damping in one ring, room for bunch compression and final focus in the other, and twice as many bunches. Standard beam-beam parameters can keep the needed damping time long and the AC power low. We must study further the bunch compression and Final Focus beam issues.