1. Positron Sources of Next generation B-factories (SuperKEKB, SuperB)
POSIPOL-2011 workshop in Beijing,
Positron Sources of Next generation B-factories (SuperKEKB, SuperB)
Takuya Kamitani (KEK)
with helps of A. Variola and S. Guiducci
on SuperB positron source information

2. KEKB view from sky Belle detector 8.0 GeV HER (e-) 3.5 GeV LER (e+)
circ. 3.0 km
ex-TRISTAN tunnel
Injector linac
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

3. SuperKEKB overview 7.0 GeV HER (e-) 4.0 GeV LER (e+)
from a slide by M. Maszawa at IPAC 2010 in Kyoto
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

4. SuperB Layout 4.2 GeV LER (e-) 6.7 GeV HER (e+) circ. 1.26 km
from a slide by M. Biagini at SuperB workshop in Elba, 2011
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

5. SuperB site plan Tor Vergata
from a slide by M. Biagini at SuperB workshop in Elba, 2011
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

6. machine parameter comparison
SuperKEKB
SuperB (Frascati)
particle type e- e+
beam energy
GeV
7.0
4.0
4.2
6.7
stored current A
2.6
3.6
2.5
1.9
bunch intensity
x1010
6.5
9.0
5.1
# of bunches
2500
978
circumference m
3016
1258
emittance ex/ey
nm/pm
5.1/14
3.2/13
2.5/6.2
2.0/5.0
beam lifetime
min 10
4.5
polarization -
80 %
luminosity
cm-2s-1
8 x 1035
10 x 1035
SuperB parameters from reports by S. Guiducci & A. Variola at SuperB workshop in Elba, 2011
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

7. requirements on beam injection
SuperKEKB
SuperB (Frascati)
particle type e- e+
beam energy
GeV
7.0
4.0
4.2
6.7
beam intensity
nC/pulse 10 8
0.78
0.64
# bunches/pulse 2
1 (5 Max)
beam repetition Hz
total 50 50
for main rings
emittance gex/gey mm
20/20
98/7
45/TBD
54/9
energy spread 1s %
0.08
0.07
0.14
0.11
for damping ring -
3000
2200
energy spread ( (hard-edge)
1.5
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

8. Injectors SuperKEKB injector SuperB injector high current gun 1.1 GeV
Damping Ring
circ. 136 m
low emittance
RF gun
Bunch
Compressor
50 Hz (e+ or e-)
3.5 GeV
10nC x 2 (prim. e-)
5nC x 2 (inj. e-)
Energy-spread
Compression System
4.0 GeV e+
4nC x 2
S-band
linac
ECS
e+ target &
120 MeV L-band
capture section
7.0 GeV e-
5nC x 2
0.6 GeV
10nC
SuperB injector
L-band linac
300 MeV
CAPTURE
SECTION
THERMIONIC
GUN
0.7 GeV PC
0.6 GeV
SHB
S-band (TM020)
+L-band
1.0 GeV
Damping Ring
circ. 51 m
combiner
DC dipole e+
6.7 GeV e+ 0.6nC
BUNCH
COMPRESSOR
50 Hz (e+)
+ 50 Hz (e-)
5.7 GeV e+
4.0 GeV e-
B graded
S band
Sections
50 MeV
POLARIZED
SLAC GUN
SHB
0.2 GeV e-
4.2 GeV e- 0.8nC
from a report by A. Variola at SuperB workshop at Elba, 2011
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

9. SuperKEKB Capture section
KEKB e+ capture section
QWT system (2.0 T x45mm T x8m) air-core pulse coil DC solenoids
KLY1 (S-band) -> Acc1, Acc2 1m-long 12 MV/m, aper 2a = 27 -> 25 mm
KLY2 (S-band) -> Acc3, Acc4 2m-long 10 MV/m, aper 2a = 25 -> 21 mm
beam energy at capture section exit : 80 MeV
N(e+)/N(e-) = 10 % at 3.5 GeV linac-end
N(e+)/N(e-)/E(e-) = 2.5 %/GeV
SuperKEKB e+ capture section
AMD system (6.0 T x200mm T x15m) flux concentrator DC solenoids
beam energy at capture section exit : 120 MeV
Deceleration
mode
L-band -> Acc1, Acc2 2m-long 10 MV/m, aper 2a = 39 -> 35 mm S-band -> Acc3~Acc6 2m-long 10 MV/m, aper 2a = 32 -> 30 mm
L-band -> Acc1, Acc2 2m-long 10 MV/m, aper 2a = 39 -> 35 mm L-band -> Acc3~Acc6 2m-long 10 MV/m, aper 2a = 39 -> 35 mm
to be upgraded
in a few years
N(e+)/N(e-) = 65 % at 1.1 GeV DR
N(e+)/N(e-)/E(e-) = 19 %/GeV
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

10. SuperB capture section
34 meter
AMD system (6.0 T x200mm T x34m) DC solenoids
beam energy at capture section exit : 333 MeV
Deceleration
mode
L-band -> 3m-long x10 (13 MV/m), aper 2a = 40 mm
S-band TM020 -> 3m-long x2 (22.5 MV/m), aper 2a = 30 mm + L-band -> 3m-long x8 (13 MV/m), aper 2a = 40 mm
N(e+)/N(e-) = 33 % at 1.0 GeV (total yield)
N(e+)/N(e-) = 19 % at 1.0 GeV (after dE/E<1.0% cut)
N(e+)/N(e-)/E(e-) = 32 %/GeV
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

11. SuperB TM020 cavity
from a slide by A. Variola at SuperB workshop in Elba, 2011
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

12. SuperB capture simulation
Deceleration phase !
from a slide by A. Variola at SuperB workshop in Elba, 2011
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

13. SuperKEKB e+ linac beam optics
Optics calculation by N. Iida
Many Quadrupoles are wound
outside the accelerator structures.
Capture
section exit
End of
Sector-2
FODO system
triplet system
Start
N(e+)/N(e-)
Slit:
42mm
S-band
large aper.
φ30
S-band
normal aper.
φ20
S-band：Separated Quads
φ20
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

14. Satellite bunch elimination (SuperKEKB)
satellite bunches generated in capture section make radiation problem in DR injection
due to coprime (5:11) frequency relation of L-band (1298 MHz) and downstream S-band (2856MHz), most of L-band satellites are eliminated during S-band acceleration
only S-band case
(loss = 0.40%)
L + S-band combination case
(loss = 0.05%)
particles outside
the separatrix
are lost at
DR injection
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

15. SuperB beam optics
from a slide by A. Variola at SuperB workshop in Elba, 2011
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

16. ECS & BCS (SuperKEKB) Bunch Energy-spread Compression Compression
System
Energy-spread
Compression
System
BCS reduce bunch-length of e+ extracted from DR
ECS reduce energy-spread of e+ entering DR
energy gradient by RF field
+ non-isochronous arc
non-isochronous arc +
energy correction by RF field
Vc = 37 MV (L-band)
R56 = m
compression 1/9
R56 = m
Vc = 41 MV (S-band)
compression 1/3
schematic view
scale is not precise !
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

17. Energy equalization idea
This idea is proposed for linear colliders, but still in conceptual consideration level and not for SuperB baseline design.
from a slide by A. Variola at SuperB workshop in Elba, 2011
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

18. e+ capture animation (SuperKEKB)
from target to capture section exit (120 MeV)
Acceleration phase mode
in capture section
Deceleration phase mode
in capture section
Energy (MeV)
Energy (MeV)
longitudinal position (mm)
longitudinal position (mm)
Capture efficiency is comparable
in either mode.
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

19. e+ acceleration (SuperKEKB)
during S-band linac acceleration (120 -> 1100 MeV)
Acceleration
mode in CS
Deceleration
mode in CS
Relative Energy
Relative Energy
longitudinal position (mm)
longitudinal position (mm)
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

20. energy-spread compression (SuperKEKB)
in Energy-spread compression system
Acceleration
mode in CS
Deceleration
mode in CS
Relative Energy
Relative Energy
longitudinal position (mm)
longitudinal position (mm)
Deceleration phase mode is favorable
in viewpoint of energy tail distribution.
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

21. Flux concentrator BINP-type (SuperKEKB)
BINP prototype field measurement & high-power operation test performed at KEK
Breakdown problem over 7 Tesla relating to a flux disturbance by a target or a gap to vacuum chamber
Investigation of the magnet will be performed at BINP by disassembl-ing.
Beam test at KEK positron station cancelled by the 3.11 earthquake damage of KEKB linac
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

22. Flux concentrator SLAC-type (SuperKEKB)
SLAC-type of conventional flux concentrator is also considered as a candidate due to the proven stability in long-term operation.
Discussion will be started with IHEP people who have recent experience of fabrication and operation of a SLAC-type of flux concentrator.
from drawings of SLAC-type flux concentrator fabricated at IHEP
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

23. Super-Conducting solenoid (SuperKEKB)
As an alternative focusing device, superconducting solenoid is considered.
Quenching due to heating by radiation from target will be a obstacle in operation.
Beam irradiation tests are performed to evaluate quenching limit.
No quench in 10 minutes at 3.2 Tesla with irradiation of 1.7 GeV e- beam of 6nC x2 x 49 Hz.
Cost of refrigerator will be a problem.
1.7 GeV e- beam
6nC x2 x 49 Hz
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

24. L-band components (SuperKEKB)
First L-band accelerating structure completed in 2010 March.
First L-band 30 MW klystron is in conditioning operation.
The accelerating structure will be tested in KEKB linac tunnel in 2012 April after constructing a test bench.
Collinear dummy load is under consideration to avoid output coupler and enable smaller DC solenoid aperture size.
RF frequency 1298 (=2856 x5/11) MHz
traveling-wave structure
constant gradient
(2/3)pi phase advance per cell
structure length 2.2 meter
disk aperture 2a = > 35.0 mm
field strength 10 MV/m
attenuation constant tau = 0.26
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani

25. Summary
SuperB needs higher energy (6.7GeV) positrons than SuperKEKB (4.0GeV) due to opposite energy asymmetry.
SuperKEKB needs higher positron bunch intensity due to (x2.4) longer circumference and (x1/2) lower pulse repetition.
SuperKEKB uses higher energy (3.5GeV) primary electrons than SuperB (0.6GeV).
SuperB uses longer (34m) capture section than SuperKEKB (15m) for higher e+ capture efficiency.
SuperKEKB uses L-band capture section + S-band linac, SuperB uses (S-band TM020 + L-band cavities) in the capture section + L-band linac.
SuperKEKB coprime frequency relation (5:11) is useful for satellite bunch elimination.
SuperKEKB uses Energy-spread Compression System (non-zero R56 arc & supplementary accelerator) to improve DR injection efficiency.
Detailed design study and R&D are ongoing in the both projects.
POSIPOL workshop in Beijing, 2011 August 28-30, "Positron sources of Next generation B-factories" by Takuya Kamitani