Compton Based Polarized Positron Sources for ee Linear

Compton Based Polarized Positron Sources for e+/e- Linear Colliders A. Vivoli* Thanks to : A. Variola, R. Chehab, T. Omori, F. Zimmermann, Bulyak, M. Kuriki, * E-mail : Alessandro. Vivoli@cern. ch E.

CONTENTS • Introduction to Pol. e+ Sources • Simulation Results • Different Schemes for Compton Sources • Possible application to CLIC • Conclusions 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 2

MOTIVATION For next e-e+ colliders polarization of both e- and e+ would be very useful. (G. Moortgat-Pick et al. , Physics Reports 460 (2008) 131 -243 ) 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 3

General Scheme of P. P. S. (Polarized) e+ are not available in nature! Target Positron Source: • Primary e- beam generation • Generation of Gamma rays (Ondulator, Compton, …) • Pair production in a target (W, Ti, Liquid Pb, …) • Capture of e+ • Acceleration and Transport • Stacking in a Damping Ring 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 4

Compton Backscattering l el’ Ee-= gmec 2 Linear Compton Backscattering • l’ ≈ l /(4 g 2) Optimum Energy for e+ production and capture: Eg ≈ 30 Me. V l ≈ 1 mm Eg ≈ 4 g 2 hc/ l ≈ 30 Me. V g ≈ 2500 Ee- ≈ 1. 3 Ge. V • 10/30/2021 , r 02 = 6. 66 · 10 -25 cm 2 A. Vivoli, Compton Based Polarized Positron Sources 5

Compton e+ Sources • Proof-of-principle demonstration: T. Omori et al. , PRL 96 (2006) 114801 • Compton Ring + Stacking Cavity • ERL + Stacking Cavity (T. Omori, J. Urakava, M. Kuriki – KEK) (A. Variola, F. Zomer, R. Chehab – LAL) (E. Bulyak, P. Gladkikh – NSC KIPT) NEED STACKING IN DR • Linac + CO 2 laser (V. Yakimenko, I. V. Pogorelsky - BNL) NO NEED STACKING 10/30/2021 Very interesting, not treated here. A. Vivoli, Compton Based Polarized Positron Sources 6

Stacking Cavity Laser power = W Laser frequency = flaser Cavity length = L Energy gain = G flaser ≈ Elaser= W/ flaser ·G 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 7

By T. Omori 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 8

By T. Omori 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 9

Polarized Positron Source ERL Scheme e- g e- Compton cavities 1. 8 Ge. V superconducting linac e- injector + Bunch Compressor 10/30/2021 e+ ee+ Target 4. 8 (2. 2) Ge. V superconducting linac with quadrupole focusing Capture Section with solenoid (+ Bunch Compressor) Up to ~150 (200) Me. V A. Vivoli, Compton Based Polarized Positron Sources (PRE)Damping Ring 10

Gamma Production Scheme (by T. Omori) 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 11

10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 12

Simulation (CAIN) Photons Mean Energy : 27, 7 Me. V 10/30/2021 1. 8 Ge. V – 5 IP Number of photons simulated : 75177 105 A. Vivoli, Compton Based Polarized Positron Sources 13

COMPARISON OF DIFFERENT ENRGY SCHEMES 1. 3 Ge. V – 5 IP 10/30/2021 1. 3 Ge. V – 10 IP A. Vivoli, Compton Based Polarized Positron Sources 1. 8 Ge. V – 5 IP 14

Positron Production (EGS) • Number of e+ : • Mean energy : • Polarization : 10/30/2021 6470 105 17. 627 Me. V 21% A. Vivoli, Compton Based Polarized Positron Sources 1. 8 Ge. V – 5 IP 15

Scheme of the Capture Section (up to 180 Me. V) 79 Cavities 5 - 10 Interaction points e- source Target AMD e- g e 1. 3 – 1. 8 Ge. V ERL e- 10/30/2021 e+ (180 - 200 Me. V) eg Solenoid Dump A. Vivoli, Compton Based Polarized Positron Sources 16

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 : 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 17

Beam parameters Parameters of the positron beam at the exit of the target (z = 0 cm) and at the exit of the AMD (z = 50 cm) N. e+ ex 105 (rms) p mm mrad ey (rms) <E> s. E sz (rms) p mm mrad Me. V mm Z=0 5499 1807 2444 19. 35 11. 69 0. 31 Z = 50 2866 434 433 20. 15 11. 08 7. 9 Capture percentage : 52, 12 % 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 18

Captured Positron Beam 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 19

New Cavity (1. 3 GHz, SW, 100 KW CW) 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 20

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 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 21

Beam parameters II Parameters of the positron beam at the exit of the AMD (z = 50 cm) and at the exit of the solenoid (z = 5775 cm) N. e+ ex 105 (rms) p mm mrad ey (rms) <E> p mm mrad Me. V s. E sz (rms) Me. V mm Z = 50 2866 434 433 20. 15 11. 08 7. 9 Z = 5775 1591 20 19 164. 39 24. 24 10. 76 ez (rms) p mm mrad 7. 29 9. 65 Multiple stacking needed 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 22

COMPARISON OF YIELD & POLARIZATION FOR DIFFERNET Ee - 10/30/2021 Energy (Ge. V) Yield e+/g (%) Pol (%) 1. 0 0. 9 48 1. 3 1. 7 48 1. 5 2. 3 33 1. 8 4. 0 27 A. Vivoli, Compton Based Polarized Positron Sources 23

Capture Section (+ CHICANE) Target From Compton Cavities g Adiabatic Matching Pre-accelerator Device Chicane eg Solenoid e+ Cavities Bending Magnets To the accelerator Drift f = 8 - 10 cm Magnetic field Electric field 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 24

Bending angle = 16 deg 10/30/2021 drift length = 200 cm A. Vivoli, Compton Based Polarized Positron Sources BM length = 60 cm 25

Beam parameters II Parameters of the positron beam at the exit of the solenoid (z = 5775 cm) and at the exit of the chicane (z = 6540 cm) N. e+ ex 105 (rms) p mm mrad ey (rms) <E> p mm mrad Me. V s. E sz (rms) Me. V mm ez (rms) p cm Me. V Z = 5775 1591 20 19 164. 39 24. 24 10. 76 9. 65 Z = 6540 701 17 15 180. 02 6. 79 2. 44 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 16. 24 26

RESULTS (180 Me. V) CASE N. g Yield e+/g % N. e+ ez ex ey s. E sz p cm Me. V p mm mrad Me. V cm 1. 3/10 1. 06 1010 0. 31 A 3. 26 107 1. 86 19 21 4. 14 1. 93 1. 3/10 1. 06 1010 0. 28 A 3. 00 107 1. 73 19 21 3. 88 1. 83 1. 3/10 1. 06 1010 0. 25 A 2. 62 107 1. 58 19 20 3. 42 1. 64 1. 3/5 0. 67 1010 0. 36 2. 39 107 1. 53 15 17 3. 55 1. 67 1. 8/5 0. 75 1010 0. 88 6. 65 107 2. 15 19 19 5. 60 1. 85 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 27

Capture Section (+ B. C. ) Target From Compton Cavities g Adiabatic Matching Pre-accelerator Device Chicane Bunch Compressor eg Solenoid e+ Cavities Bending Magnets Drifts To the accelerator Magnetic field Electric field 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 28

Bunch Compressor Tesla Cavities e+ Triplets 10/30/2021 Bending Magnets A. Vivoli, Compton Based Polarized Positron Sources Drifts 29

Beam parameters III Parameters of the positron beam at the exit of the chicane (z = 6540 cm) and at the exit of the BC (z = 7961 cm) N. e+ ex 105 (rms) p mm mrad ey (rms) <E> p mm mrad Me. V ez s. E sz (rms) Me. V mm (rms) p cm Me. V Z = 6540 701 17 15 180. 02 6. 79 16. 24 2. 44 Z = 7961 701 19 16 177. 08 3. 05 2. 62 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 9. 03 30

5 Ge. V 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 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 31

Beam parameters IV Parameters of the positron beam at the exit of the BC (z = 7961 cm) and at the exit of LINAC (z ~ 105 cm) N. e+ ex 105 Z= 7961 Z~ 105 (rms) p mm mrad ey (rms) <E> p mm mrad Me. V s. E sz (rms) Me. V mm ez (rms) p cm Me. V 701 19 16 177. 08 9. 03 3. 05 2. 62 681 1. 48 0. 80 5074 3. 04 9. 59 31. 70 Yield e+/g = 0. 9 % 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 32

Polarization Estimations of polarization are made assuming that the initial polarization of the positrons doesn’t change. P = 60. 3 % 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 33

STACKING SIMULATIONS By F. ZIMMERMANN 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 34

frep = 40. 8 MHz : 1 st turn of DR stacking 24. 6 ns (1) 1 st turn begin e+ 6. 1 5 bunches from ERL ns DR 24. 6 ns (2) 1 st turn end e+ 6. 1 5 bunches from ERL ns DR By T. Omori 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 35

(b) frep = 40. 8 MHz : 2 nd turn of DR stacking 24. 6 ns (1) 2 nd turn begin e+ 6. 1 5 bunches from ERL ns DR 24. 6 ns (2) 2 nd turn end e+ 6. 1 5 bunches from ERL ns DR By T. Omori 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 36

(b) frep = 40. 8 MHz : 3 rd turn of DR stacking 24. 6 ns (1) 3 rd turn begin e+ 6. 1 5 bunches from ERL ns DR 24. 6 ns (2) 3 rd turn end e+ 6. 1 5 bunches from ERL ns DR By T. Omori 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 37

(b) frep = 40. 8 MHz : 4 th turn of DR stacking 24. 6 ns (1) 4 th turn begin e+ 6. 1 5 bunches from ERL ns DR 24. 6 ns (2) 4 th turn end e+ 6. 1 5 bunches from ERL ns DR By T. Omori 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 38

(b) frep = 40. 8 MHz : 5 th turn of DR stacking 24. 6 ns (1) 5 th turn begin e+ 6. 1 5 bunches from ERL ns DR 24. 6 ns (2) 5 th turn end 6. 1 5 e+ bunches from ERL ns DR By T. Omori 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 39

Compton source megatable - 1 beam energy circumference particles per extracted bunch rf frequency harmonic number no. trains stored in the ring #bunches/train bunch spacing gap between trains #e+ / injection #turns btw inj. in 1 bucket injections/bucket per cycle injection frequency full cycle length time between inj. periods #turns between cycles length of one inj. period TI=total # injections/bucket ST=store time after last inj. IP=interval with inj. periods energy loss/turn longitudinal damping time t|| 10/30/2021 ILC-DR Snowmass ILC 2008 – ‘ 05 proposal Compton “CR-B” “CERL-B” 5 Ge. V 3223 m 2. 4 x 1010 650 MHz 6983 10 (10/pulse) 280 4. 202 ns 80 (336 ns) 2. 4 x 108 1 10 ~240 MHz 200 ms 10 ms 930 0. 107 ms 100 109 ms 91 ms 5. 5 Me. V CLIC pre-DR CLIC 2008 (& 2007 (NLC CLIC CERL 2004 ) Compton vers. ) 5 Ge. V 1. 98 Ge. V 6695 m 230. 93 m 10 2. 0 x 10 4. 0 x 109 650 MHz 2 GHz 14516 1540 52. 5 (52. 5/pulse) 4 (1/pulse) 50 312 6. 15 ns 0. 5 ns ~50 ns 73 (36. 5 ns) 6. 65 x 107 2 5 40 30 1020 (cont. ) 3 80 MHz 32 MHz ~50 MHz 200 ms 80 ms 1. 9 ms 450 (5155) 2470 1. 34 ms 114 ms 0. 046 ms 300 1020 60 97 ms 86 ms 42 ms 103 ms (114 ms) 38 ms 8. 7 x 2 Me. V 0. 803 Me. V 10 ms A. Vivoli, Compton 6. 4 ms Based 6. 4 ms Polarized Positron Sources 2 ms 2. 424 Ge. V 251. 6 m 4. 5 x 109 2 GHz 1677 1 312 0. 5 ns 682. 7 ns 6. 65 x 107 40 80 (cont. ) 50 MHz 20 ms (20647) 2. 6837 ms 80 17. 3163 ms (2. 6837 ms) 1. 63 Me. V (4. 08 Me. V) 1. 25 ms (0. 5 40 ms)

Compton source megatable - 2 ILC-DR ILC 2008 - ILC 2008 CLIC pre- CLIC 2008 (& Snowmass Compton vers. DR 2007 CLIC CERL ‘ 05 proposal “CR-B” “CERL-B” (NLC 2004) Compton vers. ) 0. 05 rad-m 0. 063 rad-m transv. normalized edge emittance at inj. (10 x rms) transv. normalized dynamic >>0. 05 rad 0. 4 rad-m 0. 2 rad-m? aperture (Ax+Ay)gamma m? rms bunch length at injection 3 mm 9 mm 11. 4 mm 3. 8 mm 11. 4 mm rms energy spread at injection 0. 14% 0. 06%(3 Me. V) 0. 04% 0. 28% 0. 08% [2 Me. V] final rms bunch length 6 mm 5. 2 mm 5. 12 mm 0. 79 mm (0. 47 mm) final rms energy spread 0. 14% 0. 091 % 0. 089% 0. 095% (0. 12%) longit. “edge” emittance at inj. 0. 7 me. V-s 0. 72 me. V-s 0. 73 me. V-s rf voltage 20 MV 36 MV 1. 72 MV (16. 3 MV) momentum compaction 3 x 10 -4 4. 2 x 10 -4 1. 69 x 10 -3 9 x 10 -5 2 nd order mom. Compact. 1. 3 x 10 -3 5. 8 x 10 -2 (3 x 10 -4) synchrotron tune 0. 0356 0. 084 0. 0188 0. 0045 (0. 0127) bucket area 292 me. V-s 129 me. V-s 10 me. V-s 12 me. Vs (234 me. Vs) ICM=bckt area/edge emit. /p 133 57 4 (102) RMIN=TI/ICM 0. 75 18 15 (0. 59) IP/RMIN/t|| 12 1 1. 3 (9. 1) IP/RACT/t|| 0. 09 0. 15 0. 31 (0. 09) o o o synchronous phase 15. 58 28. 97 26. 47 (14. 49 o) separatrix phases 1&2 164. 42 o, 151. 03 o, -82. 64 o 153. 53 o, (165. 51 o, 159. 19 o 95. 66 o -163. 83 o) max. momentum acceptance +/-2. 7% +/- 1. 6% +/- 1. 0% +/-1. 6% (+/- 13%) injection offset d, z ramped in d +1. 5%, 0. 01 m ramped in d (+13. 20%, 0 m) simulated stacking efficiency 82% ~95% ~94% not comp. 95. 5% final # positrons / bunch 2 x 1010 1. 94 x 1010 6 x 1010 not comp. 5. 1 x 109

Design of the Energy Compressor Chicanes Tesla Cavities …. . Quadrupoles Beam ellipse in the longitudinal phase space (z, E) 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 42

FINAL RESULTS 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 43

Compton Ring (CR) vs Compton Energy Recovery Linac (C-ERL) Unit Energy e. Bunch length (rms) Operation Bunch Charge 10/30/2021 CR C-ERL Ge. V 1. 0 - 1. 3 – 1. 8 ps 10 - 20 ~1 mode Burst ‘Almost’ CW n. C 5 - 10 0. 5 – 1. 6 A. Vivoli, Compton Based Polarized Positron Sources 44

REQUIREMENTS • ILC Ne+ = 2· 1010 x 2625 = 5. 25· 1013 e+ /pulse tpulse ~ 22 ms fr= 5 Hz 2. 625· 1014 e+/s Polarization : Min 30% Possibly ≥ 60% • CLIC Ne+ = 4· 109 x 312 = 1. 248· 1012 e+/pulse tpulse = 156 ns fr= 50 Hz 6. 24· 1013 e+/s Polarization : 10/30/2021 Min 30% Possibly ≥ 60% A. Vivoli, Compton Based Polarized Positron Sources 45

ILC - CR By T. Omori, A. Variola et al. 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 46

2 10 exp 8 positrons 1. 3 Ge. V Linac 100 bunches T b_b = 18. 45 ns C=553 m Gamma Ng = 4 10 exp 10 bunch Collision 226 turns (416 micro sec) then wait 2 msec. Single cycle ~ 2. 5 m sec. Waiting time Between stack In the same bucket = 1/200 Tcool To DR CW linac 1. 5 Ge. V CW linac 3. 5 Ge. V Stack 40 times 416 microsec 564 bunches Tb_b =6. 15 ns C=1040 m Tcool = 2 msec wait = 2 msec single cycle ~2. 5 msec Transfer at 400 Hz It means that in 100 msec => 40 shots Total 320 stackings/bunch in main-DR

Compton Ring Scheme for ILC • Compton scattering of e- beam stored in storage ring off laser stored in Optical Cavity. • 5. 3 n. C 1. 8 Ge. V electron bunches x 5 of 600 m. J stored laser -> 2. 3 E+10 γ rays -> 2. 0 E+8 e+. • By stacking 100 bunches on a same bucket in DR, 2. 0 E+10 e+/bunch is obtained. Electron Storage Ring 1. 8 Ge. V 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 1. 8 Ge. V booster 48

ILC – C ERL By T. Omori, A. Variola et al. 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 49

ERL scheme for ILC • High yield + high repetition in ERL solution. – 0. 48 n. C 1. 8 Ge. V bunches x 5 of 600 m. J laser, repeated by 54 MHz -> 2. 5 E+9 γ-rays -> 2 E+7 e+. – Continuous stacking the e+ bunches on a same bucket in DR during 100 ms, the final intensity is 2 E+10 e+. 1000 times of stacking in a same bunch Photon Conversion Target To Positron Liniac Capture System Laser Optical Cavities RF Gun Dump SC Linac 1. 8 Ge. V 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 50

CLIC - CR By L. Rinolfi, E. Bulyak, P. Gladkikh 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 51

Compton ring design E. Bulyak, P. Gladkikh / NSC KIPT Number of e- = 312 x 6. 2 x 1010 = 1. 93 x 1013 in the ring 1 cycle = 15 000 turns = > T = 156 ns x 15 000 = 2. 3 ms Laser on during 2500 turns Photon yield = 85 photons / e 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources C ≈ 47 m 52

CLIC Compton scheme Compton configuration for polarized e+ 2. 424 Ge. V e+ DR L. Rinolfi 2. 424 Ge. V 20 turns makes 312 bunches with 4. 4 x 109 e+/bunch Compton ring Stacking cavity 1 YAG Laser pulse 10/30/2021 600 m. J 2 GHz 50 Hz g e+ target 1. 06 Ge. V GHz 2 Injector Linac 2. 2 Ge. V Drive Linac RF gun C = 47 m, 156 ns/turn, 312 bunches with 6. 2 x 1010 e/bunch e+ PDR and Accumulator ring Pre-injector Linac for e+ 200 Me. V g (10 -20 Me. V) 2 GHz 2. 1 x 109 /turn/bunch A. Vivoli, Compton Based Polarized Positron Sources e+ 2. 6 x 108 pol. /turn/bunch 53

CLIC – C ERL By F. ZIMMERMANN 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 54

2008 CLIC e+ Compton scheme example 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 55

Conclusions A Compton based Polarized Positron Source with stacking cavity scheme could fulfill the requirement of ILC (more difficult) and CLIC (easier), but improvements are necessary in : • Laser technology (power/repetition rate) • Optical cavity technology (energy gain/repetition rate) • Capture section efficiency (higher yield, smaller emittance, polarization) • Stacking (relaxation of too strict assumptions) 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 56

THANKS. The End 10/30/2021 A. Vivoli, Compton Based Polarized Positron Sources 57