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