1. with contributions from
CLIC e+ sources
L. Rinolfi
with contributions from
E. Bulyak, F. Zimmermann
Tanks to
H. Braun, R. Chehab, P. Gladkikh, T. Kamitani, M. Kuriki, A. Latina, T. Omori, J. Sheppard, D. Schulte, J. Urakawa, A. Variola

2. Short history of CLIC e+ source
1997, CLIC conventional unpolarized source (L. Rinolfi) => CLIC Note 354
2000, CLIC undulator source (T. Kamitani)
2001, CLIC detailed e+ study: target, capture, pre-linac (T. Kamitani, L. Rinolfi)
=> CLIC Note 465
2001, Snowmass meeting (R. Assmann, F. Zimmermann)
=> JLC Compton scheme preferred option CLIC Note 501
2005, new ILC Compton scheme (F. Zimmermann) => CLIC Note 639
2006 April, POSIPOL 2006 workshop (Collaboration CERN/KEK/LAL/KIPT)
=> Laser Compton study for CLIC
2006 June, EPAC Conference => CLIC Note 674 CERN; 1)NSC/KIPT,Kharkov; 2)KEK; 3)DESY, Zeuthen; 4)LAL, Orsay; 5)IPN, Lyon; 6)BINP, Novosibirsk ; 7) IHEP, Beijing; 8) INFN Frascati; 9)LPI, Moscow; 10)NIRS, Chiba, Japan; 11) Waseda University, Japan; 12) Hiroshima University; 13)Sumitomo Heavy Indust. Ltd., Tokyo
2007, Major CLIC parameters changes (CLIC Study group)

3. Major CLIC parameters changes
In January 2007, new CLIC key parameters have been adopted:
Accelerating gradient:
150 MV/m => MV/m
RF frequency:
30 GHz => 12 GHz
=> All CLIC study is today under revision, in particular the CLIC Injector complex and the e+ production (polarized and unpolarized).

4. Possible CLIC methods for e+ production
The basic three:
conventional
undulator-based
laser Compton based
Two other methods:
head-on collision using the CLIC Drive Beam
ERL

5. The CLIC Injector complex in 2007 Base line configuration
e+ Main Linac
e- Main Linac
e- BC2
e+ BC2
12 GHz
2.3 GV
12 GHz
2.3 GV
12 GHz, 100 MV/m, 21 km
12 GHz, 100 MV/m, 21 km
9 GeV
48 km maximum
3 TeV
Base line configuration
Booster Linac
6.6 GeV
3 GHz
 360 m
e+ BC1
e- BC1
 10 m
 10 m
3 GHz
162 MV
3 GHz
162 MV
2.424 GeV
360 m
e+ DR
2.424 GeV
360 m
e- DR
e+ PDR
e- PDR
2.424 GeV
2.424 GeV
Injector Linac
2.2 GeV
1.5 GHz
 150 m
e-/e+
Target
Laser
Primary beam
Linac for e-
2 GeV
Pre-injector
Linac for e+
200 MeV
Pre-injector
Linac for e-
200 MeV
Laser
DC gun
Polarized e-
RF gun
Unpolarized e-
1.5 GHz
1.5 GHz
1.5 GHz
 150 m
 15 m
 15 m

6. Main beam parameters comparison
At the entrance of the Main Linac for e- and e+
NLC
(1 TeV)
CLIC 2007
(3 TeV)
ILC
(Nominal)
Energy E
GeV 8 9 15
Bunch population N
109
7.5 20
Nb bunches / train nb -
190
311
2625
Bunch spacing Dtb ns
1.4
0.667
(8 RF periods)
369
Train length tpulse
266
207
968625
Emittances gex , gey
nm, nm.rad
3300, 30
600, 10
8400, 24
rms bunch length sz mm
90-140
300
rms energy spread sE %
0.68
(3.2 % FW)
1.5
Repetition frequency frep Hz
120 50 5
Beam power P kW
219 91
630

7. CLIC parameters relevant for e+ source
# of bunches per pulse
# of positrons per bunch
# of positrons per pulse
Total charge
(nC)
Train pulse
(ns)
Current
(A)
Frequency
(Hz)
Entrance of Main Linac
311
4.1 x 109
1. 275x1012
242
207
1.17 50
At exit Pre- Damping ring
4.5 x 109
1.4 x 1012
265
1.3
Assuming ~ 90 % efficiency between the PDR and the Main Linac

8. CLIC conventional e+ source
Parameter
Unit
CLIC (*)
Primary Beam
Energy (E)
GeV 2
N e- /bunch (N)
109 13
Beam power kW 66
Linac frequency
GHz
1.5
Bunch length (rms) (sz) mm 3
Parameter
Unit
CLIC (*)
Target
Material
W75Re25
Length (4 c0) mm 14
Beam power deposited kW 16
Pulse energy density
1012 GeV/mm2
0.33
Energy lost per volume
1012 GeV/mm3
0.04
Deposited P / Beam Power % 25
(*) T. Kamitani, L. Rinolfi CLIC Note 465

9. Simulations for the Pre-Injector Linac (e+)
For positrons at 200 MeV
The normalised transverse emittances are:
x,y = rad.m  rad.m [at 1 ]
E = 7 MeV and t = 17 ps.

10. Injector Linac entrance (e+)
Assuming 95 % of transmission efficiency in the Injector Linac and 70% of capture efficiency in the PDR
=> N (e+) = 6.7 x 109
Parameter
Unit
CLIC 2007
Energy (E)
GeV
0.2
No. of particles/bunch (N)
109
6.7
Bunch length (rms) (sz) mm 5
Energy Spread (rms) (sE) %
3.5
Longitudinal emittance (el)
eV.m
35000
Horizontal emittance (gex)
nm. rad
9.2 x 106
Vertical emittance (gey)
Simulations have shown
Yield = 0.31 e+/ e- GeV
=> N (e-) = 11 x 109
at 2 GeV
If decelerating phase used
=> Yield = 0.39 e+/e- GeV

11. Simulations for the Injector Linac (e+)
PLACET simulation results at Injector linac exit
For positrons
E mean = 2.4 GeV
Ne+ = 6.4 x 109 / bunch
DE = 17 MV/m
Total distribution:
sE = 1.5 %
rms bunch length 5 mm
For acceptance DE/E = 2 % FW
Capture = 74 % of e+
rms bunch length 3.2 mm
Longitudinal distribution obtained with PLACET
A. Latina (CERN)
=> We have data to design the CLIC e+ Pre-Damping Ring

12. Polarization Polarisation is not a cheap option
In addition to cost of conventional source: For undulator
Layout of machine must accommodate:
civil engineering for longer linac tunnel (cost and geologic limitations)
photon dump
e+ transfer line …
Impact on operation and commissioning
Impact on beam performance
In addition to cost of conventional source: For Compton
civil engineering for new ring
laser system and optical cavity
Laser power
Design Compton ring
e+ stacking

13. Experimental results obtained at ATF (KEK): Compton
Polarization results
Experimental results obtained at ATF (KEK): Compton
104 polarized e+ per bunch with 73% ± 15% ± 19% polarization
Experimental results expected at E-166 (SLAC):Undulator
2 x107 polarized e+ per bunch with % polarization

14. CLIC and ILC Damping rings
(3 TeV)
ILC
(Nominal)
Energy E
GeV
2.424 5
Circumference C m
360
3230
Bunch population
109
4.4 20
Nb bunches / train -
311
2625
Bunch spacing ns
0.667 3
Final emittances ex,y
nm, nm.rad
430, 4
8000, 20
rms bunch length sz mm
1.5 9
Final rms energy sE %
0.137
0.15
RF frequency
MHz
1500
650
Repetition frequency frep Hz 50

15. The CLIC Injector complex (Undulator)
BDS
BDS
e- Main Linac
e+ Main Linac
e- BC2
e+ BC2
12 GHz
12 GHz
1.8 km
12 GHz, 100 MV/m, 21 km
Booster
Linac
7 GeV
e+ BC1
21 km
e+ DR
3 GHz
Booster
Linac
7 GeV
2.424 GeV
20 km
To the IP
e- beam
e- BC1
e- DR
e- PDR
Linac for e-
2.2GeV
Injector
1.5 GHz
2.2GeV
Injector
Linac for e+
150 GeV
e- beam
Target
Ti alloy
Pre-injector
Linac for e+
Undulator ~100 m
1.5 GHz
2.424 GeV
e-/e+
Target
Laser
Primary beam
Linac for e-
200 MeV
Pre-Injector
Linac for e+
200 MeV
3 TeV
Undulator configuration for polarized e+
Unpolarized e-
RF gun
Keep Alive Source

16. CLIC layout from ILC scheme Undulator configuration for polarized e+
Injector Linac
2.2GeV
1.5 GHz
50 Hz
500 m

17. Undulator questions Coupling operation between e- and e+
e+ generated on the previous e- pulse. Constraints on the lengths for main linac + transport lines => multiple of DR circumference
Today the linac length just fit to reach the Luminosity and the 3 TeV at the center of mass (with conventional e+ source). Estimate the reduced performance of the CLIC-IP
Emittance growth from ey = 10 nm.rad ?
Polarized e- through the undulator. What is the polarization and spin behavior after ?

18. The CLIC Injector complex (Compton)
e+ Main Linac
e- Main Linac
e- BC2
e+ BC2
12 GHz
2.3 GV
12 GHz
2.3 GV
12 GHz, 100 MV/m, 21 km
12 GHz, 100 MV/m, 21 km
9 GeV
48 km
3 TeV
Laser Compton configuration
Booster Linac
6.6 GeV
3 GHz
 360 m
e+ BC1
e- BC1
 10 m
 10 m
3 GHz
162 MV
3 GHz
162 MV
2.424 GeV
360 m
e+ DR
2.424 GeV
360 m
e- DR
e+ PDR and Accumulator ring
e- PDR
2.424 GeV
2.424 GeV
Injector Linac
2.2 GeV
RF gun
1.5 GHz
e- Drive Linac
1.3 GeV
 150 m
Compton ring
3 GHz e+
Target
Pre-injector
Linac for e+
200 MeV
Pre-injector
Linac for e-
200 MeV
Laser g
DC gun
Polarized e-
Laser
Stacking cavity
1.5 GHz
1.5 GHz
 15 m
 15 m

19. ILC - CLIC differences for Compton
Bunch structure:
CLIC has 5 x less bunch charge and 8 x less bunches per pulse:
Should relax laser parameters
Single one optical cavity
Bunch spacing:
CLIC has 4 x less bunch spacing:
=> Optical cavity more challenging
Repetition frequency:
CLIC has 10 x more repetition frequency:

20. Compton e+ source parameters
CLIC
ILC
Energy
1.3 GeV
Circumference
68 m
277 m
RF frequency
1.5 GHz
650 MHz
Bunch spacing
0.20 m
0.923 m
Nb bunches stored
311
280
e- Bunch population
6.2 x 1010
Nb optical cavities 1 30
Photons/bunch/turn
4.3 x 109
5.8 x 1010
Photons (23-29 MeV)
6.9 x 108
1.36 x 1010
Pol. e+/bunch/turn
9.8 x 106
1.9 x 108
Nb injections/bunch
450
100
Total Nb e+/pulse
1.4 x 1012
5.3 x 1013
Total Nb e+/second
6.8 x 1013
2.7 x 1014

21. CLIC Compton ring E. Bulyak Parameters CLIC Energy 1.3 GeV
RF frequency
1.5 GHz
RF voltage
50 MV
e- Bunch charge
10 nC
e- bunch length at IP
5 mm
Synchrotron losses
400 keV/turn
Laser photon energy
1.164 eV
Laser rms pulse length
0.9 mm
Laser rms pulse radius
0.005 mm
Laser pulse energy
600 mJ
Full cycle (turns)
15000

22. CLIC Compton ring E. Bulyak Simulated yield = 0.07 photons/e-/turn
Simulated photon yield as a function of turns number for continuous interaction with 600 mJ YAG laser pulse over 2500 turns

23. Compton configuration for polarized e+ e+ PDR and Accumulator ring
CLIC scheme in 2007
Compton configuration for polarized e+
2.424 GeV
360 m
e+ DR
2.424 GeV
450 turns makes 311 bunches with 4.5x109 e+/bunch
e+ PDR and Accumulator ring
C = 68 m, 226 ns/turn, 311 bunches with 6.2x1010 e-/bunch
Injector Linac
2.2 GeV
1.5 GHz
RF gun
Drive Linac
1.3 GeV
1.5 GHz
Compton ring
3 GHz
50 Hz
Pre-injector
Linac for e+
200 MeV g
Stacking cavity
g (23-29 MeV) 6.9x108 /turn/bunch
9.8x106 pol. e+/turn/bunch
e+ target
1 YAG Laser pulse

24. Compton questions Can we get the requested laser power ?
YAG laser into the Compton ring => large momentum acceptance (7-8%). Up to which value energy spread can be tolerated ?
Is the present lattice design optimized for low and non linear momentum compaction ?
What is the status of the feed-back on the laser, on the optical cavity ?
Could we design a e+ Pre-Damping ring which allow e+ stacking and minimum transverse emittance as requested for the CLIC DR ?

25. CLIC scheme with Drive Beam ILC proposal from BNL(*)
Parameters
CLIC
ILC proposal from BNL(*)
Energy
2.3 GeV
6 GeV
Current
100 A
4 A
Nb bunches / train
3600
2625
e- Bunch population
5 x 1010
8 x 1010
Bunch charge
8 nC
13 nC
Repetition fequency
50 Hz
5 Hz
g to e+ conv. target
2GeV 100A e- beam
g beam
e+ beam
(*) V. Yakimenko, POSIPOL 2006

26. Letter of Intent for EU-FP7-POSIPOL
Design study
Compton ring design
Collection system design
Multiple injection schemes
Technological R&D
High power & high repetition rate lasers
Fabry-Perot optical cavities in pulsed regime
Polarimetry
Test Facility Experiments
Validation at ATF & DANE

27. Conclusion
1) CLIC made major changes on their basic parameters. Therefore all parameters are under revision and could still be changed.
2) For the e+ conventional source, a solid study exist. The design of a e+ Pre-Damping Ring is urgently needed.
3) For polarized e+ based on Undulator, critical issues remain to be study.
4) For polarized e+ based on Compton, the scheme is more appropriate for a central injector complex and several parameters are relaxed compared with ILC. Nevertheless here also some critical issues remain to be study.
5) For polarized e+ based on head-on collision using the CLIC Drive Beam, study with new CLIC parameters has just started.