1. Capture and Transport Simulations of Positrons in a Compton Scheme Positron Source A. VIVOLI*, A. VARIOLA (LAL / IN2P3-CNRS), R. CHEHAB (IPNL & LAL / IN2P3-CNRS) Thanks to : T. OMORI, F. Zimmermann * E-mail : vivoli@lal.in2p3.fr

2. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 2 CONTENTS General scheme of the positron source Design and Simulation of the elements Polarization Optimization Future steps

3. 29/02/2016 A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 3 Positron Source e - injector + Bunch Compressor Compton cavities e-e- ERL Scheme  e-e- e+e+ Target Capture Section with solenoid (+ Bunch Compressor) Up to ~200 MeV 4.8 GeV superconducting linac with quadrupole focusing Damping Ring e+e+ 1.8 GeV superconducting linac e-e-

4. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 4 Gamma Production Scheme (by T. Omori)

5. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 5 Simulation (CAIN) Mean Energy : 27,7 MeV Number of photons simulated : 75177 10 5 Photons

6. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 6 Positron Production (EGS) Number of e + : 6470 10 5 Mean energy : 17.627 MeV Polarization : 21%

7. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 7 5 Interaction points e-e- e + (180 MeV) 1.8 GeV ERL e-e- Target  AMD e-e- 79 Cavities  e-e- e - source Scheme of the Capture Section (up to 180 MeV) Dump Solenoid

8. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 8 Adiabatic Matching Device Length: L = 50 cm Magnetic field at the target : B 0 = 6 T Magnetic field at the end : B(L) = 0.5 T Magnetic Field Behaviour :

9. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 9 N. e + 10 5  x (rms) p mm mrad  y (rms) p mm mrad MeV  E MeV  z (rms) mm 54991807244419.3511.690.31 286643443320.1511.087.9 Beam parameters Z = 0 Z = 50 Parameters of the positron beam at the exit of the target (z = 0 cm) and at the exit of the AMD (z = 50 cm) Capture percentage : 52,12 %

10. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 10 Captured Positron Beam

11. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 11 Pre-accelerator Solenoid Magnetic Field = 0.5 T Length = ~ 57 m Accelerating Cavities: Length = 56 cm Aperture = 2. cm Average accelerating Field = ~ 3.3 MV/m Number of cavities = 79 Drift length between cavities = 13 cm

12. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 12 New Cavity (1.3 GHz, SW, 100 KW CW)

13. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 13 N. e + 10 5  x (rms)  mm mrad  y (rms)  mm mrad MeV  E MeV  z (rms) mm  z (rms)  mm mrad 286643443320.1511.087.97.29 1591 2019164.3924.2410.769.65 Beam parameters II Z = 50 Z = 5775 Parameters of the positron beam at the exit of the AMD (z = 50 cm) and at the exit of the solenoid (z = 5775 cm) Multiple stacking needed

14. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 14 Capture Section (+ CHICANE) From Compton Cavities To the accelerator Target  Adiabatic Matching Device Pre-accelerator Chicane e-e- e+e+ SolenoidCavities  Bending Magnets Drift  = 8 - 10 cm Magnetic field Electric field

15. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 15 Bending angle = 16 degdrift length = 200 cmBM length = 60 cm

16. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 16 N. e + 10 5  x (rms) p mm mrad  y (rms) p mm mrad MeV  E MeV  z (rms) mm  z (rms)  cm MeV 1591 2019164.3924.2410.769.65 701 1715180.026.7916.242.44 Beam parameters II Z = 5775 Z = 6540 Parameters of the positron beam at the exit of the solenoid (z = 5775 cm) and at the exit of the chicane (z = 6540 cm)

17. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 17 Capture Section (+ B.C.) From Compton Cavities To the accelerator Target  Adiabatic Matching Device Pre-accelerator Bunch Compressor e-e- e+e+ SolenoidCavities  Bending Magnets Drifts Magnetic field Electric field Chicane

18. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 18 e+e+ DriftsBending Magnets Triplets Bunch Compressor Tesla Cavities

19. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 19 N. e + 10 5  x (rms) p mm mrad  y (rms) p mm mrad MeV  E MeV  z (rms) mm  z (rms)  cm MeV 701 1715180.026.7916.242.44 701 1916177.08 9.033.052.62 Beam parameters III Z = 6540 Z = 7961 Parameters of the positron beam at the exit of the chicane (z = 6540 cm) and at the exit of the BC (z = 7961 cm)

20. 29/02/2016A. Vivoli, Capture & Transmission of polarized positrons from a Compton Scheme 5 GeV superconducting LINAC Quadrupoles length :L = 10 – 20 cm Field at pole tip :B = 3 – 5 KG Quadrupoles aperture :R = 5 cm Cavities length : l = 1.25 m Mean accelerating field : E = 9 MV/m Cavities aperture : r = 3.5 cm

21. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 21 N. e + 10 5  x (rms) p mm mrad  y (rms) p mm mrad MeV  E MeV  z (rms) mm  z (rms)  cm MeV 701 1916177.08 9.033.052.62 681 1.480.805074 31.703.049.59 Beam parameters IV Parameters of the positron beam at the exit of the BC (z = 7961 cm) and at the exit of LINAC (z ~ 10 5 cm) Yield e + /  = 0.9 % Z= 7961 Z~ 10 5

22. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 22 Polarization Estimations of polarization are made assuming that the initial polarization of the positrons doesn’t change. P = 60.3 %

23. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 23 Stacking simulations performed by F. Zimmermann showed that in order to have efficient stacking a small energy spread is needed (  E /E ~10 -4 ). In order to have a smaller energy spread it’s possible: To reduce the bunch length at the beginning of the LINAC. To insert an Energy Compressor at 5 GeV. OPTIMIZATION

24. Design of the Energy Compressor 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 24 Tesla Cavities ….. Chicanes Quadrupoles Beam ellipse in the longitudinal phase space (z,E)

25. Future Steps Reduce the Energy spread of the beam trying with different devices (reduced bunch length, energy compressor, different strategy of spread control, …) Study the evolution of the polarization along the positron source. Employing a pre-damping ring in the positron source ? Employing 2 crossed laser for each interaction point ? … 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 25

26. 29/02/2016A. Vivoli, Capture and Transport Simulation of Positrons... POSIPOL 2008, HIROSHIMA 26 THANKS. The End