Super-B Factory Workshop January 19-22, 2004 Super-B IR design M. Sullivan 1 Interaction Region Design for a Super-B Factory M. Sullivan for the Super-B.

1Super-B Factory WorkshopJanuary 19-22, 2004

Super-B IR designM. Sullivan

Interaction Region Designfor a

Super-B Factory

M. Sullivan

for the

Super-B Factory WorkshopHawaii

January 19-22, 2004



Outline

•General B-factory parameters and constraints

•Present B-factory IRs

•Super B-factory IR attempts

•Summary



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 downstream fans striking the nearby vacuum chambers.

Some Issues and Constraints



The Q1 magnet is always going to be shared

The Q1 magnet is the closest quadrupole to the IP. At least one beam is always bent in this vertically focusing magnet. This bending generates SR fans.

The Q2 magnet must be a septum magnet

If this next closest magnet is common to 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 for PEP-II).

Constraints...







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.

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).

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

Still more detector requirements



Machine Parameters that are Important for the IR

PEP-II KEKBLER energy 3.1 3.5 GeVHER energy 9.0 8.0 GeVLER current 1.96 1.51 AHER current 1.32 1.13 A y

* 12.5 6.5 mm

x* 25 60 cm

X emittance 50 20 nm-radEstimated y

* 5 2.2 m

Bunch spacing 1.26 2.4 mNumber of bunches 1317 1284Collision anglehead-on 11 mradsBeam pipe radius 2.5 1.5 cm

Luminosity 7.21033 11.31033 cm sec


Super-B IR designM. SullivanAssumptions e36 with 8 GeV e+

1) Tune shift in X equals tune shift in Y for each beam.2) IP spot sizes identical.

Input Calculations

E- (GeV) 3.5000 gamma - 6849E+ (GeV) 8.0000 gamma + 15656

Tune shift - 0.11 I- (A) [3] 22.249Tune shift + 0.11 I+ (A) [3] 9.734

Bunch spacing (m) 0.63 Number of bunches 3316HER Bunch current (mA) 6.71

Luminosity (cm-2 sec-1) 1.25E+36 LER Bunch current (mA) 2.94Specific Luminosity 19.14

Beam aspect ratio (v/h) - 0.01 N- (electrons/bunch) 3.072E+11Beam aspect ratio (v/h) + 0.01 N+ (electrons/bunch) 1.344E+11

Beta y* - (cm) 0.15 emittance x - (nm-rad) [100] 79.21Beta y* + (cm) 0.15 emittance x + (nm rad) [100] 79.21

Ion gap (%) 5 emittance y - (nm-rad) 0.79emittance y + (nm rad) 0.79

Beta x* - (cm) 15.0Constants Beta x* + (cm) 15.0

2 pi 6.283185 sigma x- (microns) 109Electron mass (GeV) 0.000511 sigma x+ (microns) 109Electron radius (m) 2.81794E-15Electron charge (Coul.) 1.60218E-19 sigma y- (microns) 1.09Speed of light (m/sec) 299792458 sigma y+ (microns) 1.09

Luminosity constant 2.16724E+34 sigma x'- (microradians) [314] 727sigma x'+ (microradians) [444] 727

1S mass (GeV) 9.4602S mass (GeV) 10.023 sigma y'- (microradians) [314] 7273S mass (GeV) 10.355 sigma y'+ (microradians) [444] 7274S mass (GeV) 10.5805S mass (GeV) 10.865 15 uncoupled sigma x'- (mrads) 10.95

15 uncoupled sigma x'+ (mrads) 10.95

15 coupled sigma y'- (mrads) [20] 77.4615 coupled sigma y'+ (mrads) [28] 77.46

30 nominal sigma y'- (mrads) [20] 21.8030 nominal sigma y'+ (mrads) [28] 21.80

Center of mass (GeV) 10.583

Beam Parameters for a PEP-III 11036 Luminosity Accelerator



PEP-III Super B

Now Projected Upgrade Super BLER energy 3.1 3.1 3.1? 3.5 GeVHER energy 9.0 9.0 9.0? 8.0 GeVLER current 1.8 3.6 4.5 22.2 AHER current 1.0 1.8 2.0 9.7 A

y* 12.5 8.5 6.5 1.5 mm

x* 28 28 28 15 cm

X emittance 50 40 40 70 nm-radEstimated y

* 4.9 3.6 2.7 1.7 m

Bunch spacing 1.89 ~1.5 1.26 0.63 mNumber of bunches 1034 1500 1700 3400Collision angle head-on head-on 03.25 12-14 mradsBeam pipe radius 2.5 2.5 2.5 1.5-2.0? cm

Luminosity 6.61033 1.81034 3.31034 11036 cm sec



Present PEP-II beam energies

9 GeV and 3.1 GeV

Symmetric optics

Generates upstream SR fans

+/- 12 mrad crossing angle (a la KEK)

Must have a crossing angle. Very difficult if not impossible to have 3400 bunches (1st parasitic crossing is at 31.5 cm from the IP) without a crossing angle.

In addition, the radiation fans from B1 type magnets would become very intense at these high beam currents.

1st attempt



E36 B-Factory +/- 12 mrad xing angle Q2 septum at 2.5 m

30

20

10

0

-10

-20

-30

cm

-7.5 -5 -2.5 0 2.5 5m

Q1

Q1Q1

Q1

Q2

Q4Q5

Q2

Q4Q5



E36 B-Factory +/- 12 mrad xing angle Q2 septum at 2.5 m

30

20

10

0

-10

-20

-30

cm

-7.5 -5 -2.5 0 2.5 5m

Q1

Q1Q1

Q1

Q2

Q4Q5

Q2

Q4Q5



KEK beam energies

8 GeV and 3.5 GeVLowering the energy ratio improves the SR fans at the IP. The upstream fans are further away from the beam pipe allowing for a smaller radius pipe.

Symmetric optics

+/- 12 mrad crossing angle (a la KEK)

2nd attempt


Super-B IR designM. SullivanE36 B-Factory +/- 12 mrad xing angle Q2 septum at 2.5 m 8 GeV

30

20

10

0

-10

-20

-30

cm

-7.5 -5 -2.5 0 2.5 5m

Q1

Q1Q1

Q1

Q2

Q4Q5

Q2

Q4Q5

3.5 GeV

8 GeV



100 kW

100 kW

20 kW

20 kW

E36 B-Factory +/- 12 mrad xing angle Q2 septum at 2.5 m 8 GeV

30

20

10

0

-10

-20

-30

cm

-7.5 -5 -2.5 0 2.5 5m

Q1

Q1Q1

Q1

Q2

Q4Q5

Q2

Q4Q5

3.5 GeV

8 GeV



100 kW

100 kW

20 kW

20 kW

E36 B-Factory +/- 12 mrad xing angle Q2 septum at 2.5 m 8 GeV

30

20

10

0

-10

-20

-30

cm

-7.5 -5 -2.5 0 2.5 5m

Q1

Q1Q1

Q1

Q2

Q4Q5

Q2

Q4Q5

3.5 GeV

8 GeV

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



Asymmetric optics (again a la KEK)

The upsteam QD1 magnet for the LER is essentially on axis

The magnet locations are still symmetric (+/-Z)

Still have some upstream bending but the fans are greatly reduced from the previous symmetric optics case. The main SR fans still clear the local IR.

+/- 14 mrad crossing angle

The larger crossing angle is needed to keep the QF2 magnet at the 2.5m point from the IP

This large a crossing angle opens up the possibility of filling all 6800 bunches if the RF freq. is doubled

3rd attempt



0

10

20

30

-10

-20

-300-5 5m

cm

Super B-factory IR

E36_2_5M_8_RL

M. Sullivan, Jan. 16, 2004

QD1QD1

QF2

QF2

QD4

QF5

QD4

QF5

HER

LER

83 kW

11 kW

40 kW

200 kW



0 0.5 1-0.5-1

0

2

4

-2

-4

cm

m

Super B-factory +/- 14 mrad crossing angle

HER

LER

from: B3$E36_2_5M_8_R,L.OUT

M. Sullivan, Jan. 16, 2004

A 1 cm radius beam pipe might be possible now



Detector magnetic field axis

This constraint has not been added in yet. In order to minimize the torques on the QD1 magnets these two magnets need to be aligned with the detector magnetic field. The average axis of the two magnets is then the detector axis.

4th attempt (to be continued)



A super B-factory IR is quite challenging

The very high beam currents rule out designs in which SR fans are intercepted locally

The IR design in the areas of detector backgrounds, HOM power and SR quadrupole radiation are all very difficult and need to be thoroughly studied.

The trick is to find a solution that satisfies all of these requirements without compromising the physics

Summary

Super-B Factory Workshop January 19-22, 2004 Super-B IR design M. Sullivan 1 Interaction Region Design for a Super-B Factory M. Sullivan for the Super-B.

Documents

superb ir design

general bfactory parameters

q2 magnet

q1 magnet

closest magnet

septum magnet

beam separation

permanent magnet