Injector optimization for FCCee positron production Bowen Bai

Injector optimization for FCCee positron production Bowen Bai, A. Faus-Golfe, Y. Han, I. Chaikovska, R. Chehab in collaboration with F. Zimmermann and K. Oide 16/07/2020 1

FCCee injector complex Based on Super. KEKb (common linac for e+/e- )

Three different schemes – bypass options Dogleg scheme Chicane scheme Arc scheme 3

Comparison between two e- sources Electron source (e- gun) 4. 46 Ge. V e- linac Performances Parameters Output of guns End of Section 2 (with wakefields) End of Section 2 (with wakefields and offsets) (100 machines with correction) (next page) 6. 5 n. C RF gun 100% >83% 10 n. C thermionic gun 4

1. Dogleg scheme Code: SAD 1. 1) 4. 46 Ge. V e- linac 1. 2) dogleg bypass 1. 3) e+ generation Results from Dr. Yanliang Han Accelerating mode /deaccelerating mode + Conventional target /hybrid target 1. 4) e+/e- separator chicane Code: MADX + PLACET 1. 5) 1. 54 Ge. V e+ linac Conventional target + deaccelerating mode Positron yield: 2. 3 5

2. Chicane scheme Code: SAD 2. 1) 4. 46 Ge. V e- linac 2. 2) chicane bypass 2. 3) e+ generation Results from Dr. Yanliang Han Accelerating mode /deaccelerating mode + Conventional target /hybrid target 2. 4) e+/e- separator chicane Code: MADX + PLACET Conventional target + deaccelerating mode Positron yield: 2. 3 2. 5) 1. 54 Ge. V e+ linac 6

3. Arc scheme Code: SAD 3. 1) 4. 46 Ge. V e- linac 3. 2) arc bypass 3. 4) e+/e- separator chicane 3. 5) 1. 54 Ge. V e+ linac In progress, similar to J-arc from Super. KEKB 3. 3) e+ generation Results from Dr. Yanliang Han Accelerating mode /deaccelerating mode + Conventional target /hybrid target Conventional target + deaccelerating mode Positron yield: 2. 3 7

4. Final results After positron target Performances of 100 random machines after orbit steering Error type Value Offsets 100 um/urad Rotation 100 urad Electron source: 6. 5 n. C RF Gun Electron source: 10 n. C thermionic Gun Before damping ring (DR) Before positron target Electron source: 6. 5 n. C RF Gun Electron source: 10 n. C thermionic Gun 8

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Backup e+ generation Electron source: 6. 5 n. C RF Gun Electron source: 10 n. C thermionic Gun 4 cases: 1. Conventional target + accelerating mode 3. Hybrid target + accelerating mode Positron yield: 2. 26 Positron yield: 2. 32 2. Conventional target + deaccelerating mode 4. Hybrid target + deaccelerating mode Positron yield: 2. 48 Positron yield: 2. 53 Hybrid target + deaccelerating mode Positron yield: 2. 536 10 10

Positron linac optics design For accelerating e+ from 200 Me. V to 1. 54 Ge. V Section 12 LAS + 28 normal S band LAS Acceleration 2 m Length Frequency 2856 MHz Aperture (a) ~15 mm Gradient 10 MV/m Normal S band Acceleration 2 m Length Frequency Beta (β) Starting energy （ Ge. V） End energy (Ge. V) 1 0. 3 16. 6 1 0. 215 0. 342 2 0. 4 8. 5 1. 15 0. 342 0. 699 3 0. 4 6. 86 1. 35 0. 699 0. 858 4 0. 4 5. 6 1. 65 0. 858 1. 057 5 0. 4 4. 5 2 1. 057 1. 295 6 0. 4 3. 6 2. 4 1. 295 1. 57 Section 1 Section 4 Section 2 Section 5 Section 3 Section 6 2856 MHz Aperture (a) ~10 mm Gradient Quadrupo le le length strength (k 1) 20 MV/m 11