1. SESSION ACCELERATEURS participants au groupe de travail 3 exposés 1 invité Arguments : 1) Accélération laser-plasma 2) Futurs collisioneurs 3)Technologie des accélérateurs

2. Variola, R. Roux, S. Cavalier, M. Omeich, B. Mouton, G. Bienvenu, J
Variola, R.Roux, S.Cavalier, M.Omeich, B.Mouton, G.Bienvenu, J.Brossard, H.Jenhani, P.Puzo, P.Bambade, O.Dadoun, C.Rimbault Accelerator Physics : Future Colliders

3. New Prospects in the field of future colliders : ILC CLIC SuperB
These machines do not yet exist.
They are already projected in the future…
(near? Far?)

4. Why a linear collider?
Particle physics colliders to date have (at my knowledge) all been circular machines (with the exception – SLAC SLC).
Highest energy e+e- collider was LEP2: ECM=200 GeV
Energy increases at given radius
DE ~ E4/r (synchrotron radiation) e.g. LEP DE = 4 GeV/turn; P~20 MW
High energy in a circular machine becomes prohibitive
large power or huge tunnels (and tech. problems as e- cloud, desorption…etc)
ILC
cost
Circular
Collider
Linear Collider
Energy

5. ILC

6. The ILC : concept Beams with energy tuneable up to 250 GeV
(upgrade to 500 GeV);
Two identical linear several km long linacs.
90% polarised electron source; positrons formed by g’s creating e+-e- pairs (possibly polarisation 60%).
Damping rings to produce very small emittance beams.
Final focus to collide nanobeams (crossing angle?).

7. ILC layout
~30 km (500 GeV)
~50 km (1 TeV)
2 x 250 GeV linear accelerators ECM < 500 GeV, 20 mrad crossing angle.
Cold technology : SC cavities
Positrons made from g’s (can be polarized) striking a conversion target.
Two interaction points.
Using backscattered laser light -0ption for a g-g collider.
Option for a low energy collision region (GigaZ)

8. ILC Challenges => A lot, but we can divide them in two categories :
1 ) Technology
2) Scheme and machine physics
Bunch train length 950 ms
Train rep rate 5 Hz
Beam height at collision 6 nm
Beam width at collision 540 nm
Accel. Gradient MV/m
Wall plug effic. 23%
Site power (500 GeV) 140 MW
L = 2 x 1034 cm-2 s-1

9. ILC @ LAL : High Power Couplers (see R.Roux talk)
Polarised Positron Source & Polarimeter
Interaction point studies

10. Polarised Positron Source (POSIPOL)
The alternative solution : “Compton Ring”
1)The idea comes from LAL (K.Moenig)
2)A community is working covering a lot of different activities ( Fabry-Perot cavities, Compton simulations, Optimisation of the collection system,….)
3)We promote the first “POSIPOL” workshop
4)We are working to propose a definitive scheme based on low repetition frequency, high duty cycle, less cavities (interaction points)

11. Polarised positron source : Snowmass Proposal
Electron Beam (Compton Ring)
Electron Energy (GeV)
Ne-/bunch x x1010
Spot Size at CP (micron) (h)x25(v) (h)x25(v)
Circumferences (m)
Number of Bunches x
Number of Trains
Laser Beam
Photon Energy (eV)
Pulse Energy/bunch(mJ)
Spot Size at CP (micron) (h)x25(v) (h)x5(v)
Gamma-rays
Energy(MeV)
Very interesting and multidisciplinary activity:
machine physics, radiation theory,
lasers and cavities, positron production and
mechanisms of polarisation propagation……
It is a huge, self standing project!!!!

12. @LAL
Capture
Int.Point
Cavities

13. Very complex scheme….in continuous evolution => LAL
PROSPECTS => Playing a leading role in conceiving the right scheme
and in developing the technology for the Fabry-Perot Cavity.
Optimisation of the collection and of the positron production.
Analysis of the polarisation issue.
Example: scheme for the
Nd-Yag laser

14. Interaction region background studies in e+ e- collider
When beams collide:
mixing of classical and quantum effects
Bunches deformed by EM attraction: Disruption  luminosity enhancement
High beam-beam field  Energy loss in the form of synchrotron radiation: beamstrahlung
Secondary backgrounds
Electromagnetic : e+ + e- → gg → e+e- …
Hadronic : e+ + e- → gg → hadrons
Electromagnetic deflections
Effect on backgrounds (pairs ...)
Effect on luminosity measurements (Bhabha scattering)
e+ e- spin depolarisation effects
GUINEA-PIG & CAIN:
beam-beam simulation tools
After the collision:
disrupted beam induces backgrounds (photons, pairs, neutrons...)
Possible damage of beam magnets in the extraction beam line
Backscattering of background particles in the detector
BDSIM based on GEANT4:
uses to evaluate backgrounds generated along the extraction line

15. Ex: ILC & Super B studies (C.Rimbault)
x & y emittances (ILC)
x & y emittances superB
Biagini
Bhabha focusing versus
production angle q0 (mrad)
Pair phase space
Vertex Detector background
for 3, 4 and 5 T

16. Future
Extend GuineaPig, beam-beam interaction simulation code for linear colliders, to circular colliders.
Customize the existing neutron propagation in GEANT4.
Finalizing procedure for submitting our softwares on GRID LCG/EGEE (under ILC virtual organization) and XtremWeb.

17. CLIC

18. (relativistic Klystron)
CERN
(relativistic Klystron)
High acceleration gradient (150 MV/m)
“Compact” collider - overall length  40 km
NC accelerating structures
High frequency (30 GHz)
Two-Beam Acceleration Scheme (Relativistic Klystron)
High frequency
Cost-effective & efficient (~ 10% overall)

19. Philosophy
The RF power source can be described as a blind box combining very long RF pulses, and transforming them in many short pulses, with higher power and with higher frequency
Long RF Pulses
P0 , n0 , t0
350
Klystrons
low frequency
high efficiency
Power stored in
electron beam
Short RF Pulses
PA = P0  N
tA = t0 / N
fA = f0  N
48000
Accelerating Structures
high frequency high gradient
Power extracted from beam
in resonant structures
Electron beam
manipulation
R.Corsini

21. CLIC Parameters @ 3TeV Center of mass energy Ecm 3000 GeV
Main Linac RF Frequency
fRF 30
GHz
Luminosity L
6.5
1034 cm-2 s-1
Luminosity (in 1% of energy)
L99%
3.3
Linac repetition rate
frep
  150 Hz
No. of particles / bunch Nb
2.56 
109
No. of bunches / pulse kb
220
Bunch separation
Δtb
0.267 (8 periods) ns
Bunch train length
τtrain
58.4
Beam power / beam Pb
  20.4 MW
Unloaded / loaded gradient
Gunl/l
172 / 150 
MV/m
Overall two linac length
llinac
28  km
Total beam delivery length
lBD
2 x 2.6 
Proposed site length
ltot
  33.2
Total site AC power
Ptot
418
Wall plug (RF) to main beam power efficiency
ηtot
12.5  %

22. LAL – Now CTF3 Competence: -Vacuum -Magnetic elements -HF
2004: Start of the PHIN (CARE) project : photo-injector for the CERN
( and another similar one for machine studies at LAL)
Motivations: -High charge per pulse
-Short pulses
-Little emittances  + easy to transport
-No low energy tails
Competence:
-Vacuum
-Magnetic elements
-HF
Installation: end 2006

23. And what about the far future (CLIC)? SOURCES 1) Injector e-
2005: Start of the test gun construction
Goal: facility that simulate the principal beam at 30 GHz
Installation: half 2007 … we hope
SERA on CTF3
CERN experiments participation
Modify or built another gun (if needed)
R&D on the HF LAL in the NEPAL hall (?????)
Weak emittance gun
High gradient
High repetition rate ( average current)
And what about the far future (CLIC)? SOURCES
1) Injector e-
2) Polarised Positron Source (F.Zimmermann)

24. SUPERB B

25. For the time being : crazy schemes & ideas
Goal :1036 Luminosity
For the time being : crazy schemes & ideas
main goal : reduce the power consumption !!!!
Simplified layout in the
Small Disruption Regime
Collisions every Turn
ILC ring with ILC FF
ILC Compressor,
Crossing angle optional
Decompressor
Decompressor
Compressor IP
Compressor FF FF

26. An exemple of parameter set and solutions:
Flat case, Collisions in the Ring, Uncompressed Bunches
Nbunches=5000, 3Km ring
Crab focus on in vertical plane
X_crossing_angle=2*25mrad
sz=4 mm se=5MeV ex=0.4 nm
ey=0.002nm
ez=4.0mm
Collision frequency=500MHz
Lmultiturn=0.8*1036 (Lsingleturn=1.2*1036) with Np=2*1010
Vertical tune shift like in PEP!!! (similar currents,100 times more
luminosity, 100 times smaller betay)
L=1.6*1036 with Np=4*1010
Luminosity higher with further simultaneuos betax and betay
squeeze
A lot of work and ideas are still possible in the conception phase.
Determinant is the study of the interaction point!!!
So LAL : interaction point studies &
Positron source (conventional / Compton) &

27. Conclusions
3 main international collider projects : ILC, CLIC & SuperB
A lot of similarities between the different project and a lot of challenges
LAL: we have the possibility to give a significant contribution to the design and construction phase in the three projects
Specific topics are : positron sources (polarised and not), couplers, interaction point studies, photoguns, injectors...(in mixed order)
To reach this goal we need a close collaboration between the different LAL departments and......

28. Are these dreams? For real future prospects we need a strong accelerator group (as in the most important European Labs )!
Because now the SERA:
Logistics
Personnel
Technology
Electronics

29. Thanks very much to all the “ transparencies providers ”.