super-b factory workshop january 19-22, 2004 super-b ir design m. sullivan 1 interaction region...
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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
2Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
Outline
•General B-factory parameters and constraints
•Present B-factory IRs
•Super B-factory IR attempts
•Summary
3Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
4Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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...
5Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
6Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
7Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
8Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
9Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
10Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
11Super-B Factory WorkshopJanuary 19-22, 2004
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
12Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
13Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
14Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
15Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
16Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
17Super-B Factory WorkshopJanuary 19-22, 2004
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
18Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
19Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
20Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
21Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
22Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
23Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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)
24Super-B Factory WorkshopJanuary 19-22, 2004
Super-B IR designM. Sullivan
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
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