Concluding Remarks

Workshop Goals1) Take stock of the situation of the different machines, schemes, studies and R&Ds.2) Gather information on the new technologies (fiber laser, mirrors). Define the possible associated R&Ds.3) Find the overlap with the undulator solution, both for funding (EU FP7) and common work.4) Benchmark of the GEANT4 polarized version. 5) Review the industrial medical applications of Compton machine (extremely important for R&D fund request).

CLIC - Redefine the parameters. Analyze the differences from the earlier proposal and have a first feasibility scheme.ILCConverge towards a scheme that can produce a valid alternative design and clearly assess what R&Ds are necessary to validate the scheme.Point the way to EDRStudy the possibility of a demonstrator experimentDefine the aspects of the schemes that still need answering (stacking, costing) and make a work planSuperB -Introduce the new machine and address the case of polarized positrons. Introduce the FP7 design study

1st: Physics (users)Physics = f( L,P,E) => Flexible machine= flexible (POLARISED) positron source. Is there a ~ factor 3 rule?f = ? In te different cases.

Layout of positron damping ring system showing the parallel spin rotation beam lines for randomly selecting positron polarization direction. A pair of kicker magnets is turned on between pulse-trains to deflect the beam to the spin rotation solenoids with negative B-field. space for spin rotators must be foreseenK. Moffeit et al.,SLAC-TN-05-045

Take stock of the proposed solutions & technology Projects : ILC, CLIC .SuperB

1 CLIC => New parameters : three schemes proposed

Major CLIC parameters changesIn January 2007, new CLIC key parameters have been adopted:Accelerating gradient:150 MV/m => 100 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).

Main beam parameters comparisonAt the entrance of the Main Linac for e- and e+

NLC(1 TeV)CLIC 2007(3 TeV)ILC(Nominal)Energy EGeV8915Bunch population N1097.54 - 4.120Nb bunches / train nb-1903112625Bunch spacing Dtbns1.40.667(8 RF periods)369Train length tpulsens266207968625Emittances gex , geynm, nm.rad3300, 30600, 108400, 24rms bunch length szmm90-14043 - 45300rms energy spread sE%0.68(3.2 % FW)1.5 - 21.5Repetition frequency frepHz120505Beam power PkW21991630

2 ILC baseline and alternative

The asymmetriespreliminarypreliminaryUndulator

Compton Ring

POSIPOL07. Compton Ring Lattice.

MARS (Multiturn Accelerator-Recuperator Source)InjectorBeam dump G. N. Kulipanov, A. N. Skrinsky and N. A. Vinokurov, 1997ERL

ERL bunch chargeLaser & optical cavitye+ stackingSelection of bunch repetition: frep3 factors to determine frep163 MHzpreferable40.8 MHzpreferable40.8 MHzpreferable

Conclusions:15% of the x-ray energy goes into harmonicsThe x-ray signal filtered by the 10-mm Ag foil consists primarily of harmonics0.2 nC bunch contains 1.25109 electrons, i.e. 4 times the number of photons generated at IP. However, due to the approximately two times bigger cross-section of the e-beam compared with the laser focus, only ~ of the total electrons in the bunch participated in scattering. Thus, we conclude that x-ray yield is close to Ng/Ne~1, as is required for ILC.

Quantitative agreement of the BNL experiment results

e-beam - size 60 m (RMS), charge 0.2 nC, duration 3.5 ps (FWHM); laser - energy 2 J, size 35 m (RMS), duration 5 ps (FWHM). Agrees with experimentLINAC

ParametertotalharmonicsNumber of x-ray photons at IP31081.6107Integral x-ray energy at IP (eV)10121.51011Number of x-ray photons at detector71071.5107Energy on detector (eV)4101141010Filtered energy on detector (eV)3.110103.01010

Polarized Electrons: Yes And what about positrons?Is a polarized positron source interesting for the SuperB factory? Yes!SUPERB

2) Gather information on the new technologies (fiber laser, mirrors). Define the possible associated R&Ds.

Technical aspects

LASERS!!!!!!CAVITIES (electronics, mechanics)PolarimetryMirrorsToo much to say only few snapshots

Laser DiodePM - LMA fiberOIPCF fiberHigh power Laser DiodeFemtosecond oscillatorGrating stretcherCompressor

PM-LMA fiber ampli.High pump absorptionPolarized output beamPCF-Fiber amplifierHigh launch power>800W pump powerReduced non-linearities

Fiber amplifiersANR LAL / Amplitude Systemes

> 300W average powerLinearly polarized beam

3D cavity

Low Loss Coatings : Ion Beam Sputtering

4) Benchmark of the GEANT4 polarized version.

Knowledge & simulationsPOLARISED GEANT/EGS/NEW SOFTCAPTURETARGETS

Baseline Target Design Wheel rim speed (100m/s) fixed by thermal load (~8% of photon beam power)Rotation reduces pulse energy density from ~900J/g to ~24J/gCooled by internal water-cooling channelWheel diameter (~1m) fixed by radiation damage and capture opticsMaterials fixed by thermal and mechanical properties and pair-production cross-section (Ti6%Al4%V)Wheel geometry (~30mm radial width) constrained by eddy currents.20cm between target and rf cavity.T. Piggott, LLNLDrive motor and water union are mounted on opposite ends of through-shaft.

Depolarization of positrons in bremsstrahlung

Initial Pol. Vs Energy of Captured Positron Beam

Beam parameters IIIParameters of the positron beam at the exit of the solenoid (z = 3085 cm) and of the Capture Section (z = 3436 cm)Total capture efficiency ~ 2,05 %Z= 3085Z= 3436

Spot size of photon and positron0.4 r.l. titanium target,Drift to target: from 10cm up to 500cmDue to multi-scattering, positron beam spot size is bigger than photon beam spot size when photon beam is small.Due to lower probability of pair production from lower energy photons in the outer skirt of photon beam, the positron beam spot size is smaller than photon beam when photon beam spot size getting bigger.

Compton scattering & medical / industrial applicationsExtremely important : more and more fundamental science needs applications.

3 talks

Jeff RifkinSakae ArakiPhilippe Balcou

RecommendationsHow to proceed.

ILC

Baseline : need for E166 published result (V Important also for simulation benchmark)Find the common work topics (not an intellectual exercise funding)

Attempt : Capture section (simulation and prototyping), target (repository as suggested by I. Bailey), Polarization generation, transport and manipulation.

Alternative : Proceed towards STACKING simulations, Optimization, explore the different schemes and converge to a single proposal => COSTING

CLIC : Definition of a polarised scheme with the new parameters. What could be a demonstrator experiment?

SuperB : New entryto be supported.Evaluate the feasibility of a polarised solution

Recommended and supported R&Ds

Lasers & cavities:LAL : 200W fiber laser, 10exp4 gain cavity, 4 mirror cavity at high finesse, full digitalized feedbackKEK (very important) : Cavity in ATF (very important)CO2 : demonstrator of intra cavity CO2 laser (dedicated test stand, non linear optics, damages)Mirror damages @ High frep

Target : ILC demonstrator

Accelerators tech: High rep frequency and high charge per bunch e- guns

ALL this need coordinated effort of the POSIPOL community

Lets add boxesSuperB.

Undulator :

Ring :

ERL:

LINAC :

Thank youAnd.. R.Chehab, A.Vivoli, F.Zomer, C. Eguren, B.Renard, Missions Service..I surelyForgot someone

And thank you to you all for participation

PosiPol 2008Hiroshima Univ. proposes to hold PosiPol 2008 in Hiroshima with support of KEK. The period will be May or June, which will be fixed later.HiHiroshimaKEKTokyoAtomic BombMemorial DomeItsukushimaShrine2 world heritages

ILC Positron Source Group Meeting September 17 - 19, 2007Argonne National Laboratory The next ILC Positron Source Group Meeting will be held at Argonne National Laboratory, Chicago, IL, on September 17 - 19, 2007. Please visit this site for more detailed information which will be posted in a few weeks. https://www.hep.anl.gov/ILC-positron