Super-B Factory in a

1
Super-B Factory in a 4400m Tunnel

• John T. Seeman
• SBF Workshop at Frascati
• March 16, 2006

2
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!

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PEP-II Parameters

C 2200 m
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Super-KEKB Parameters

C 3016 m
5
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
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Layout of One Ring Other Ring is the Reverse!
Linac injector

Bunch compressor
Bunch expander
Damping ring 2200 m
Final Focus
Reverse Final Focus
IP And Detector
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Super-B-Factory in a 4400 m Tunnel 0.4 mm

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SUPER-B Factory in a 4400 m tunnel 0.3 mm

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SBF as shown in Traditional Ring Collider
Parameters

Emittances 12.x1.5 nm
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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.

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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.

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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.