1. SuperB project. Injection scheme design status
R. Boni, S Guiducci, M. Preger, P. Raimondi (LNF)
O. Dadoun, F. Poirier, A. Variola (IN2P3)
A. Chancé, CEA Saclay
XIV SuperB general meeting
Frascati, 29/09/2010

2. Evolution of the Injection System Layout
CDR2 SCHEME
SHB
POLARIZED
SLAC GUN t1 t2
e- prod.
e+ prod.
e+ Inj.
e- Inj.
40 msec
20 msec
Damping Ring operated alternately
for
both electrons and positrons
Main Rings injection rate: 25 Hz
Klystron HV rep. rate: 50 Hz
TIMING
R. Boni, XiV SuperB meeting, Frascati

3. New proposed scheme e+ e+ e+ e- PC 0.6 GeV SHB SHB
positron linac e+
1 GeV
CAPTURE
SECTION PC
0.6 GeV
SHB
THERMIONIC
GUN
combiner
DC dipole e+ e+
BUNCH
COMPRESSOR
5.7 GeV e GeV e-
50 MeV
CAPTURE
SECTION e-
POLARIZED
SLAC GUN
SHB
0.25 GeV
Parameter
Units
SLC
Electron charge per bunch nC 16
Bunches per pulse 2
Pulse rep rate Hz
120
Cathode area
cm2 3
Cathode bias kV
-120
Bunch length ns
Gun to SHB1 drift cm
150
en,rms,gun (fm EGUN)
10-6 m 15
from A. Brachmann - SuperB Workshop SLAC, October 2009
Round beam
Emittance @ 4.16 GeV = 1.8 nm
Required bunch charge for electrons ≈ 0.3 nC
… scrapers .. collimators needed
R. Boni, XiV SuperB meeting, Frascati

4. t1 e+ e- PC 0.6 GeV SHB SHB new injector scheme … t1 t2 TIMING
e+ prod.
e+ Inj.
e- Inj.
20 msec
10 msec
TIMING
Electron Linac e+
CAPTURE
SECTION PC
0.6 GeV
SHB
THERMIONIC
GUN
Positron Linac t1
50 MeV
CAPTURE
SECTION
POLARIZED
SLAC GUN
SHB
0.25 GeV
3.9 GeV e- e-
main rings
R. Boni, XiV SuperB meeting, Frascati

5. t2 e+ The most important advantage of this scheme is
new injector scheme … t1 t2
e+ prod.
e+ Inj.
e- Inj.
20 msec
10 msec
TIMING t2 e+
BUNCH
COMPRESSOR
5.7 GeV e+
main rings
The most important advantage of this scheme is
the higher injection rate in the main rings:
(DR damping time 20 msec)
50 Hz vs 25
R. Boni, XiV SuperB meeting, Frascati

6. POSITRON LINAC
> 600 MeV e- beam
1 GeV e+
CAPTURE
SECTION PC
the positron linac must capture high divergence particles,
Proposal of the LAL-IN2P3 group
Deceleration with a large iris S-band (2856 MHz) section followed
by an L-band (1428 MHz), 300 MeV linac (e+ yield ≈ 30 % ± 10 MeV),
immersed in a solenoidal field, followed in turn by a 700 MeV L-band linac.
S-band, decelerating,
large aperture,
10MV/m
≈ 1 mt long
L-band linac,
13÷15 MV/m,
16 sections, 3 mt long
L-band linac,
13÷15 MV/m,
8 sections, 3 mt long PC
S-BAND
L-BAND
L-BAND
300 MeV
solenoid
1 GeV
≈ 90 ÷ 120 mt
R. Boni, XiV SuperB meeting, Frascati

7. One is in operation at the Osaka Univ. (JP).
… positron linac …
L-band “room temperature” linacs are unusual in the field of accelerators.
One is in operation at the Osaka Univ. (JP).
It uses one, 3m. long acc. structure supplied with
a 1300 MHz Thales klystron TH2022E
Input power: 30 MW – 4 μsec – 60 pps
Gradient: 13 MV/m
Another one (1298 MHz) is being developed at KEK for the SuperKEKB
It will use 6÷14, 2 m. long structures, supplied by four 40 MW klystron (to be developed).
Input power per section: 10 MW
Gradient: 12 MV/m
The chosen frequency (very close to 1300)
is timed with the e+ bunch separation (96.3 nsec)
1300 MHz
KLY
R. Boni, XiV SuperB meeting, Frascati

8. a train of 4÷5 bunches separated by 4.2 = (6/1.428) nsec. However:
… positron linac …
The SuperB e+ L-band linac should operate at 1428 MHz since we accelerate
a train of 4÷5 bunches separated by 4.2 = (6/1.428) nsec.
However:
the Thales klystron TV2022D is a 30 MWP, 60 kWAV , 7 μsec, 1300 MHz source.
Thales should be available to modify the frequency if the number of sockets is >> 1.
Scaling the Osaka Univ. acc. sections,
the parameters of a 1428 MHz section are:
Freq.
1428 MHz
Type
TW - CG
Mode
2π/3
Length
3 m
Period
7 cm
Attenuation Constant
0.3 Np
Shunt Impedance
45 to 50 MΩ/m
Filling time
1.7 μsec
Quality factor
≈ 18000
In/Out VSWR
≤ 1.2
Energy gain per section
VMeV = [PZL.(1-e-2τ)]1/2 ≈ 7.8.(PMW)1/2
PIN = 30 MW ≈ 42 MeV (14 MV/m)
R. Boni, XiV SuperB meeting, Frascati

9. ? … positron linac … How many structures per klystron ?
Use of Pulse Compressor ? (must be designed ad hoc …)
Design a more efficient L-band acc. structure,
with
higher shunt-impedance but smaller irises ….
open questions ?
Linac scheme
Gradient (MV/m)
N. of klystrons
N. of
sections
Linac
Length (m) 14 24
≈ 90 10 17 34
≈ 125
14÷16 12
R. Boni, XiV SuperB meeting, Frascati

10. Injector RF Layout PC 17 L-band klystrons 28 S-band klystrons
2856 MHz
476 MHz
238 MHz
17 L-band
klystrons PC
Thermionic
GUN
0.6 GeV
SHB
476 MHz X
SHB
POL.
GUN
0.25 GeV
28 S-band
klystrons
238 MHz
476 MHz
2856 MHz
Total RF Power Sources
S-band 36
L-band 17
UHF 5
X-band 1
R. Boni, XiV SuperB meeting, Frascati

11. Bunch Compressor for e+
….. A. Chancé, Annecy meeting (march 2010).
BUNCH
COMPRESSOR
5.7 GeV e+ e+
combiner
DC dipole
≈ 13.1 m
R. Boni, XiV SuperB meeting, Frascati

12. X X e+ TL length = 34 m e+ Linac DR .. Transfer Lines
….. A. Chancé, Annecy meeting (march 2010).
No special dipoles X
No kickers and septa,
half-sine-wave kickers
in the damping ring X
e+ TL length = 34 m
R. Boni, XiV SuperB meeting, Frascati

13. Sub Harmonic Buncher
The Bunching System performs bunch length compression from 1 nsec to 10 psec.
238 MHz
476 MHz
2856 MHz
10 ps
1 ns
Standard solution, adopted in other labs (SLAC, IHEP,….)
10 ps FWHM ≈ 17 ps (±2)
R. Boni, XiV SuperB meeting, Frascati

14. Conclusions e+ e- PC 0.6 GeV SHB SHB
positron linac
1 GeV e+
CAPTURE
SECTION
L-band PC
0.6 GeV
SHB
THERMIONIC
GUN
≈ 170 m
≈ 350 m e+
BUNCH
COMPRESSOR
5.7 GeV e GeV e-
50 MeV
CAPTURE
SECTION
POLARIZED
SLAC GUN
SHB
0.2 GeV
≈ 300 m e-
combiner
DC dipole
≈ 50 m
Main Rings injection rate: 50 Hz instead of 25
Damping Ring operates just for positrons
Only 2 TL’s between Linacs and D.R., instead of 4; no special dipoles; no by-pass of the PC.
No long flat top kickers in the damping ring and transfer lines
The gun for the positron line can be thermionic, thus delivering larger current
Main Linac Klystron rep. rate: 100 Hz
The e- beam emittance is higher (round beam)…. can be reduced with scrapers/collimators …
(see Preger talk in Elba-meeting, june 2010)
R. Boni, XiV SuperB meeting, Frascati