1. INJECTION SYSTEM UPDATE
R.Boni, S.Guiducci, M.Preger, P. Raimondi, LNF
J.Seeman, SLAC
O. Dadoun, F. Poirier, A. Variola, IN2P3
XI SuperB General Meeting – LNF – Dec. 2009
With respect to the previous solutions, the IN2P3 group proposes
a scheme with e+ production at lower energy (0.6 vs 6 GeV)
(see Variola talk). The positron surplus is less, but
the linac is more compact and less expensive.
Otherwise, if the positron yield of the above solution will be
considered not enough, an injection scheme with a recirculation
line can provide a number of positrons per shot, amply sufficient
for topping-up the HER.
In both cases, one damping ring can be used for both e- and e+
This presentation follows those of :
Isola d’Elba …. June 2008
LNF Mini-Mac …. July 2008
Orsay Workshop …. Febr. 2009
LNF Mini Mac …. Apr. 2009
Perugia workshop ... June 2008
SuperB

2. # # # # INJECTION SCHEME with e-/e+ production at Low Energy
1 Damping Ring for both e- and e+ #
Electron-positron conversion at lower energy (*) #
Reduced tunnel length, because low and high energy linacs share the same gallery section #
HER and LER rings filled every 40 msec (25 Hz)
(*) subject to the IN2P3 simulations
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

3. t1 e+ injection in HER and …… low charge e- in DR
INJECTION SCHEME with e-/e+ production at low energy
INJECTION PHASES
t e+ injection in HER and …… low charge e- in DR t
t2 = t msec e- injection in LER and …. positrons in DR t
> 4 GeV
6 GeV
3 GeV
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

4. Rings injection rate: 40 msec (i.e. @ 25 Hz)
INJECTION SCHEME with e-/e+ production at low energy
TIMING t1 t2 t1 t2
20 msec
20 msec
e- prod.
e+ prod.
e- prod.
e+ prod.
e+ Inj.
e- Inj.
e+ Inj.
e- Inj.
40 msec
40 msec
Rings injection rate: 40 msec 25 Hz)
e- DR storage time = 20 msec
e+ DR storage time = 20 msec
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

5. Layout still schematic but to scale
INJECTION SCHEME with e-/e+ production at low energy
D.R. & T.L. outline
≈ 13 m
≈ 5 m
18 m.
Layout still schematic but to scale
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

6. # # # A B INJECTION Scheme with Conversion at 6 GeV
Injection process in 3 phases, to avoid simultaneous acceleration of
high-charge e- bunches and damped e+ bunches in the linac B. #
HER and LER rings filled every 60 msec (16.66 Hz) #
1 Damping Ring for both e- and e+ DR
SLAC
polarized
gun A
> 7 GeV e+
SHB
1 GeV
> 5 GeV
0.2 GeV
0.8 GeV B PS
> 4 GeV e-
Schematic Layout
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

7. RECIRCULATED INJECTION SCHEME
Injection phases
t e+ injection in HER and …… low charge e- in DR DR e+
to HER P P DC DC P P
t2 = t msec e- injection in LER DR P P DC e- DC
to LER P P
t3 = t msec e+ production DC DR PS DC
high charge e- bunches
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

8. Rings injection rate: 60 msec (i.e. @ 16.666 Hz)
RECIRCULATED INJECTION SCHEME
TIMING t1 t2 t3 t1 t2 t3
20 msec
e- prod.
e+ prod.
e- prod.
e+ prod.
e+ Inj.
e- Inj.
e+ Inj.
e- Inj.
60 msec
60 msec
Rings injection rate: 60 msec Hz)
e- DR storage time = 20 msec
e+ DR storage time = 20 msec
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

9. RECIRCULATED INJECTION SCHEME
D.R. & T.L. outline
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

10. DR & TL phases t2 = t1 + 20 ms t1 t3 = t1 + 40 ms e- injection
RECIRCULATED INJECTION SCHEME
DR & TL phases k1
≈ 60 ÷ 70 ns t e+ e- DR k2
t2 = t ms t1 k1 DR k3 k4 k3 SR e+ t e- e+ e- PM PM PM PM
e- injection
e- production and e+ injection
t3 = t ms DR k2 k4 e+
high charge e-
e+ production
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

11. Parameter list 1 GeV Damping Ring … for details, see Perugia workshop
Energy (GeV)
1.0
Circumference (m)
51.1
Horizontal betatron tune
7.40
Vertical betatron tune
2.72
Momentum compaction
0.0057
Horizontal phase advance per cell (deg)
270
Vertical phase advance per cell (deg) 90
Maximum horizontal beta (m)
7.9
Maximum vertical beta (m)
7.3
Maximum dispersion (m)
0.77
Uncorrected horizontal chromaticity
-11.5
Uncorrected vertical chromaticity
-8.7
Equilibrium horizontal emittance (nm) 23
Horizontal betatron damping time (ms)
7.26
Vertical betatron damping time (ms)
7.36
Synchrotron damping time (ms)
3.70
Equilibrium energy spread (%)
0.062
RF frequency (MHz)
476
Harmonic number 81
RF voltage (MV)
0.5
Bunch length (low current, cm)
0.48 K S
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

12. SLAC Polarized Gun courtesy A. Brachmann Parameter SLC gun
Electron charge per bunch
16 nC
Bunches per pulse 2
Pulse rep rate
120 Hz
Cathode area
3 cm2
Cathode bias
-120 kV
Bunch length
2 ns
Gun to SHB1 drift
150 cm
en,rms,gun (fm EGUN)
15•10-6 m
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

13. Standard solution, adopted in other labs (SLAC, IHEP,….)
Bunching System
The Bunching System performs bunch length compression from 1 nsec to 10 psec.
2856 MHz
238 MHz
476 MHz
10 ps
1 ns
Standard solution, adopted in other labs (SLAC, IHEP,….)
2856 MHz
476 MHz
238 MHz G
SHB
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

14. RF System
For the moment, …… it is based on the use of the S-band, room temperature, technology.
Klystron parameters
Frequency
2856 MHz
Peak power
60 MW
RF pulse length
4 μsec
Cathode voltage
350÷370 kV
Beam current
400÷420 A
HV pulse width
6 μsec FWHM
Rep. rate
50 pps
Accelerating Section parameters
Frequency
2.856 GHz
Type
TW, CG
Structure
Disk-loaded, 3mt length
Mode of operation
2π/3
Number of cells
86 (with couplers)
Attenuation constant
0.57 nepers
Normalized group velocity
to (Vg/C)
Shunt impedance
53 to 60 MΩ/m
Filling time
0.85 μsec
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

15. RF System shopping list
> 7 GeV e+
> 4 GeV e-
SHB
476 MHz
238 MHz G DR PC
0.6 ÷ 1 GeV
1 GeV
6 GeV
2856 MHz
476 MHz
5 kly’s
6 kly’s
30 kly’s
L ≈ 350 m.
476 MHz
2856 MHz
476 MHz
238 MHz DR PC G
SHB
1 GeV
1 GeV
6 GeV
6 kly’s
5 kly’s
30 kly’s
L ≈ 450 m.
N. of S.band acc. sections: 124.
In addition: 1 bunching 238 MHz
1 bunching 476 MHz
1 D.R. 476 MHz
In both cases, 42 S-band klystron stations are needed.
In addition: 2 tetrodes or IOT amplifiers for the buncher
MHz klystron for the DR
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

16. After being successfully introduced in the FEL Spring8,
the RF System option ….
The option to adopt, perhaps for the high energy section, a C-band RF system, however, is still open.
After being successfully introduced in the FEL Spring8,
the C-band RF systems are also generating interest in European laboratories.
A C-band (5712 MHz) RF system is under project for the LNF SPARC photoinjector….
The PSI Lab. (CH) is considering to use the C-band technology for its X-FEL.
The main advantage of the C-band is the reduction of the linac length (≈ 30%).
The C-band RF station for SPARC will employ two, 1.5m., CI, accelerating sections designed and
manufactured by LNF in collaboration with local firms.
The new system is expected to provide an acc. gradient > 35 MV/m.
Prototyping is in progress. A 50 cm model will be brazed, vacuum and power tested by the Spring 2010
 14 cm
iris dia. = 14 mm
courtesy D. Alesini, L. Ficcadenti, F. Marcellini, V. Spizzo, LNF
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

17. Linac Linac PC PS and By-pass l d
Pulsed
Focusing
Coil
Off-axis
Linac section l d
Linac
Linac
Pulsed
dipoles
DC dipoles PC
Low charge damped electron bunches are bent by pulsed dipoles l-d and travel through the PS-hole,
2) High charge electron bunches are bent reversely and hit the PS target
Generated positron bunches follow along a straigth trajectory.
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

18. 7 x 1010 electrons in 1 nsec q ≈ 11 nC I ≈ 11 A SLAC polarized
Estimate of positron charge for topping-up
low energy
conversion
injector
recirculated linac
with 6 GeV conv.
Injection rate
40 msec
60 msec
Filling time
(5 bunches/shot)
10 sec
15 sec
Loss of peak luminosity
L/Lp
0.967
0.95
Loss of bunch current
i/io = (L/Lp)1/2
0.983
0.975
Positron/bunch at linac output
(1-i/io)•nb [nb = 5.5•1010]
0.93•109
(0.15 nC)
1.37•109
(0.22 nC)
Positron lost per second per ring
1.16•1011
1.71•1011
7 x 1010 electrons in 1 nsec
q ≈ 11 nC
I ≈ 11 A
SLAC polarized
electron source
SuperB
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009

19. Interesting proposal of IN2P3 group:
SUMMARY
Interesting proposal of IN2P3 group:
“ … long and tapered PC matching section allows to collect, with good efficiency,
enough positrons for HER topping-up, at rather low (0.6÷1 GeV) energy conversion….”
An alternative solution can be adopted if the conversion at low energy does not guarantee sufficient margin of positron current.
This solution would be more expensive (because of the longer gallery).
In this regard, the C-band option deserves great consideration.
Use of one Damping Ring for both particle types reduces costs
R.Boni, XI SuperB General Meeting – LNF – Dec. 2009