1. Concluding Remarks

2. 1) Take stock of the situation of the different machines, schemes, studies and R&D’s. 2) Gather information on the new technologies (fiber laser, mirrors…). Define the possible associated R&D’s. 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. ILC -Converge towards a scheme that can produce a valid “alternative” design and clearly assess what R&D’s are necessary to validate the scheme. -Point the way to EDR -Study the possibility of a demonstrator experiment -Define the aspects of the schemes that still need answering (stacking, costing…) and make a work plan SuperB -Introduce the new machine and address the case of polarized positrons. Introduce the FP7 design study Workshop Goals

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

4. 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 foreseen K. Moffeit et al., SLAC-TN-05-045

5. Take stock of the proposed solutions & technology Projects : ILC, CLIC ….SuperB 1 CLIC => New parameters : three schemes proposed

6. Major CLIC parameters changes In 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).

7. NLC (1 TeV) CLIC 2007 (3 TeV) ILC (Nominal) Energy EGeV8915 Bunch population N10 9 7.54 - 4.120 Nb bunches / train n b -1903112625 Bunch spacing  t b ns1.40.667 (8 RF periods) 369 Train length t pulse ns266207968625 Emittances  x,  y nm, nm.rad3300, 30600, 108400, 24 rms bunch length  z mm 90-14043 - 45300 rms energy spread  E  0.68 (3.2 % FW) 1.5 - 21.5 Repetition frequency f rep Hz120505 Beam power PkW21991630 Main beam parameters comparison At the entrance of the Main Linac for e - and e +

9. 2 ILC baseline and alternative

10. The asymmetries preliminary Undulator

11. Compton Ring

12. POSIPOL07. Compton Ring Lattice. E = 1.070 GeVE = 1.300 GeV ParameterWith chic.Without chic.With chic.Without chic. Gamma’s energy, MeV10 – 20 15 – 30 Circumference, m800128012001920 Energy acceptance, %75.57 Laser flash energy, J2222 Laser waist (RMS), μ15 Laser pulse length (RMS), mm0.5 RF voltage, MV2×40202×5030 Bunch length, mm4 – 6 Bunch charge, nC2222 Bunch spacing, cm48 Stored current, A1.25 Energy losses (SR + wigglers), keV 700 1000 Particles losses per sec., %< 20 Positron number per sec. 1.05  10 14

13. MARS (Multiturn Accelerator-Recuperator Source) MARS (Multiturn Accelerator-Recuperator Source) 8 GeV 2.6 GeV  E = 1.8 GeV ~1Å ~12Å Injector Beam dump G. N. Kulipanov, A. N. Skrinsky and N. A. Vinokurov, 1997 ERL

14. bunch charge Laser & optical cavity e + stacking Selection of bunch repetition: f rep 3 factors to determine f rep 163 MHz preferable 40.8 MHz preferable 40.8 MHz preferable

15. Conclusions: 15% of the x-ray energy goes into harmonics The x-ray signal filtered by the 10-  m Ag foil consists primarily of harmonics 0.2 nC bunch contains 1.25  10 9 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 ~¼ of the total electrons in the bunch participated in scattering. Thus, we conclude that x-ray yield is close to N  /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). Parametertotalharmonics Number of x-ray photons at IP 3  10 8 1.6  10 7 Integral x-ray energy at IP (eV)10 12 1.5  10 11 Number of x-ray photons at detector 7  10 7 1.5  10 7 Energy on detector (eV) 4  10 11 4  10 10 Filtered energy on detector (eV) 3.1  10 10 3.0  10 10 Agrees with experiment LINAC

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

17. 2) Gather information on the new technologies (fiber laser, mirrors…). Define the possible associated R&D’s. Technical aspects LASERS!!!!!! CAVITIES (electronics, mechanics…) Polarimetry Mirrors Too much to say only few snapshots

20. Laser Diode PM - LMA fiber OI PCF fiber High power Laser Diode Femtosecond oscillator Grating stretcher Compressor 1.PM-LMA fiber ampli. –High pump absorption –Polarized output beam 2.PCF-Fiber amplifier –High launch power –>800W pump power –Reduced non- linearities Fiber amplifiers ANR LAL / Amplitude Systemes > 300W average power Linearly polarized beam

24. 3D cavity  X Y Y X Z 11 22 11 22 plane mirror spherical mirror plane mirror spherical mirror   0  3D cavity V1V1 V2V2

27. Low Loss Coatings : Ion Beam Sputtering

28. 4) Benchmark of the GEANT4 polarized version. Knowledge & simulations POLARISED GEANT/EGS/NEW SOFT CAPTURE TARGETS

29. 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/g Cooled by internal water-cooling channel Wheel diameter (~1m) fixed by radiation damage and capture optics Materials 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, LLNL Drive motor and water union are mounted on opposite ends of through-shaft.

30. Depolarization of positrons in bremsstrahlung

32. Initial Pol. Vs Energy of Captured Positron Beam

33. n. e +  x (rms) mm mrad  y (rms) mm mrad MeV  E/ %  L (rms) mm % 215 34 32152.43 7.55 10.3449.43 205 32 31152.34 7.39 5.8548.94 Beam parameters III Parameters 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= 3085 Z= 3436

34. Spot size of photon and positron 0.4 r.l. titanium target, Drift to target: from 10cm up to 500cm Due 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.

35. Compton scattering & medical / industrial applications Extremely important : more and more fundamental science needs applications. 3 talks Jeff Rifkin Sakae Araki Philippe Balcou

36. Recommendations How to proceed.

39. 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 entry…to be supported.Evaluate the feasibility of a polarised solution

40. Recommended and supported R&D’s Lasers & cavities: LAL : 200W fiber laser, 10exp4 gain cavity, 4 mirror cavity at high finesse, full digitalized feedback KEK (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

41. Let’s add boxes… SuperB….

42. Undulator : Ring : ERL: LINAC :

43. Thank you And.. R.Chehab, A.Vivoli, F.Zomer, C. Eguren, B.Renard, Missions Service…..I surely Forgot someone

44. And thank you to you all for participation

45. PosiPol 2008 Hiroshima Univ. proposes to hold PosiPol 2008 in Hiroshima with support of KEK. The period will be May or June, which will be fixed later. HiHi Hiroshima KEK Tokyo Atomic Bomb Memorial Dome Itsukushima Shrine 2 world heritages

46. 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