Interaction%20Region%20Upgrade%20Options

1
Interaction Region Upgrade Options
M. Sullivan for the SLAC B-day March 20, 2003
2
Outline

• General B-factory parameters and constraints
• Present B-factory IRs
• Upgrades to PEP-II
• Super B-factory IR
• Summary

3
Some Issues and Constraints

• There is always some local synchrotron radiation
  from bending magnets
• PEP-II generates a large amount of local SR in
  order to make head-on collisions.
• KEKB also generates a lot of SR even though they
  have a large crossing angle because they designed
  for on-axis incoming beams. This shifts all of
  the bending SR to the downstream side and
  consequently increases the power levels of the
  fans striking the nearby vacuum chambers.

4
Constraints...

• The Q1 magnet is always going to be shared
• At least one beam is always bent in this magnet
  generating SR bending fans.
• The Q2 magnet must be a septum magnet
• If this magnet is shared by both beams then one
  loses most of the beam separation because it is
  x-focusing.
• Making this magnet a septum magnet forces a
  certain amount of beam separation at the face of
  the Q2 magnet (about 100 mm between beam center
  lines).

5
(No Transcript)
6
(No Transcript)
7
Detector requirements

• Maximum solid angle
• Try to keep all accelerator components far enough
  away from the IP to maximize the detector
  acceptance
• This conflicts with accelerator requirements to
  minimize the spot size by pushing in the final
  focus magnets
• Adequate shielding from local SR
• The collision beam pipe (usually Be) must be
  shielded from locally generated SR and lost beam
  particles at least well enough to avoid swamping
  the detectors.

8
More detector requirements

• Minimum amount of material in the detector
  beampipe
• This conflicts with having enough SR shielding
  (usually a thin coating of Au) to keep detector
  occupancy at acceptable levels
• Minimum radius for the beam pipe
• This must be balanced with the requested thinness
  of the beam pipe. The smaller the beam pipe the
  more power it must be able to handle (kW).

9
Still more detector requirements

• Large high-field solenoid
• This forces the final shared magnet (Q1) to be
  either permanent magnet or super-conducting
  (maybe also Q2)
• Adequate shielding from beam backgrounds
• Collimators and shield walls are needed to
  protect the detector from backgrounds generated
  around the ring
• Low pressure vacuum system near the IP
• This minimizes lost beam particles generated near
  the IP that can not be collimated out

10
Machine Parameters that are Important for the IR
PEP-II KEKB LER energy 3.1 3.5 GeV HER
energy 9.0 8.0 GeV LER current 1.8 1.5 A HER
current 1.0 1.0 A ? y 12.5
6.5 mm ?x 35 60 cm X emittance 50 20 n
m-rad Estimated sy 5 3 mm Bunch spacing 1.89
2.4 m Number of bunches 921 1184 Collision
angle head-on ?11 mrads Beam pipe
radius 2.5 2.0 cm Luminosity 5?1033
8?1033 cm-2 sec-1
11
PEP-II Upgrade Plans

• Now Projected Upgrade
• LER energy 3.1 3.1 3.1? GeV
• HER energy 9.0 9.0 9.0? GeV
• LER current 1.8 2.4 3.3 A
• HER current 1.0 1.4 1.5 A
• y 12.5 9.0 5.0 mm
• ?x 35 35 35 cm
• X emittance 50 50 50 nm-rad
• Estimated sy 5 4.3 3 mm
• Bunch spacing 1.89 1.89 1.26 m
• Number of bunches 921 1130 1700
• Collision angle head-on head-on ?3.25 mrads
• Beam pipe radius 2.5 2.5 2.5 cm
• Luminosity 5?1033 8?1033
  2?1034 cm-2 sec-1

12
(No Transcript)
13
(No Transcript)
14
Beam Parameters for a PEP-III 1?1036 Luminosity
Accelerator
15
PEP-III Super B

• Now Projected Upgrade Super B
• LER energy 3.1 3.1 3.1? 3.5
  GeV
• HER energy 9.0 9.0 9.0? 8.0
  GeV
• LER current 1.8 2.4 3.3
  22.2 A
• HER current 1.0 1.4
  1.5 9.7 A
• y 12.5 9.0 5.0 1.5
  mm
• ?x 35 35 35 15
  cm
• X emittance 50 50 50 70
  nm-rad
• Estimated sy 5 4.3 3 1.7
  mm
• Bunch spacing 1.89 1.89
  1.26 0.63 m
• Number of bunches 921 1130
  1700 3400
• Collision angle head-on head-on
  ?3.25 ?12 mrads
• Beam pipe radius 2.5 2.5
  2.5 1.5-2.0? cm
• Luminosity 5?1033 1?1034
  2?1034 1?1036 cm-2 sec-1

16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
2 cm radius and 1 cm radius beam pipes
The 1 cm radius beam pipe intercepts about 5 kW
of power from the LER and nearly the same amount
of power from the HER
23
KEKB Upgrade Plans

• Now Upgrades SuperKEKB
• LER energy 3.5 3.5 3.5 GeV
• HER energy 8.0 8.0 8.0 GeV
• LER current 1.4 2.0 9.4 A
• HER current 0.95 1.1 4.1 A
• y 6.5 6.5 3.0 mm
• ?x 60 60 15 cm
• X emittance 20 20 33 nm-rad
• Estimated sy 3 3 2 mm
• Bunch spacing 2.4 2.4 0.6 m
• Number of bunches 1184 1184 5018
• Collision angle ?11 crab ?15
  (crab) mrads
• Beam pipe radius 2.0 1.5 1-2 cm
• Luminosity 8?1033 1-2?1034
  1-3?1035 cm-2 sec-1

24
(No Transcript)
25
Summary
The Interaction Region of a B-Factory has many
conflicting requirements. The trick is to
achieve a kind of best balance between these
requirements that maximizes the luminosity for a
given B-factory design.