Circular Electron Positron Collider CEPC Injector Linac Design

Outline ØIntroduction • Main parameters • Layout of Linac ØSource design • Electron source

Introduction Main parameters ØLinac design goal • High Availability and Reliability • Simple structure

Introduction Layout of Linac Positron Linac ESBS FAS 50 Me. V DR PSPAS 4

Introduction Layout of Linac Electron Linac ESBS EBTL FAS 50 Me. V DR PSPAS

Introduction ESBS EBTL PSPAS FAS 50 Me. V Layout of Linac 4 Ge. V

Source design Electron source ØThermionic Triode electron gun ØSub-harmonic pre-buncher Parmela • 142. 8375

Source design Positron source ØLayout of positron source • Target (Conventional) ü tungsten@15 mm

Source design Positron source ØLayout of positron source • Capture & Pre-accelerating structure ü

Linac design Electron linac • Focusing device: Triplet • 1 triplet+4 Acc. Stru. 1

Linac design Electron linac Electron injection ØLow charge mode • 10 Ge. V with

Linac design Electron linac Positron production ØHigh charge mode • 4 Ge. V with

Linac design Positron linac ØPSPAS SAS (DR) +TAS • SAS: 200 Me. V 4

Linac design Positron linac ØPositron linac • 10 Ge. V with 3 n. C

Linac design Misalignment errors with correction Ø Whole Linac • One-to-one correction method for

Linac design Misalignment errors with correction Ø 4 Ge. V Electron Linac with high

Linac design • Simulation condition • 5000 seeds • Accelerating structure • phase errors

Linac design DR V 1. 0 Energy Circumference Repetition frequency Bending radius Dipole strength

Summary ØThe CEPC linac works with 100 Hz repetition, 10 Ge. V and one-bunch-perpulse,

Thank you! ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design

Dynamic aperture with errors • • With only COD corrections, DA is nearly two

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环形正负电子对撞机 Circular Electron Positron Collider CEPC Injector Linac Design Xiaoping Li, Cai Meng, Guoxi Pei, Jingru Zhang, , Dou Wang, Chenghui Yu, Jie Gao, Shilun Pei, Yunlong Chi Institute of High Energy Physics, CAS, Beijing

Outline ØIntroduction • Main parameters • Layout of Linac ØSource design • Electron source • Positron source ØLinac design • Electron/Positron mode • Error study ØSummary ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 2

Introduction Main parameters ØLinac design goal • High Availability and Reliability • Simple structure and mature technology: S-band accelerating structure as baseline(2856. 75 MHz) • Always should provide beams that can meet requirements of Booster • Should be have potential to meet the higher requirements and updates in the future Parameter e- /e+ beam energy Repetition rate e- /e+ bunch population Energy spread (e- /e+ ) Emittance (e- /e+ ) e- beam energy on Target e- bunch charge on Target ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA Symbol Unit Ee-/Ee+ frep Ne-/Ne+ σE εr Ge. V Hz n. C nm Ge. V n. C Value 10 100 >9. 4× 109 >1. 5 <2× 10 -3 <120 4 10 Potential >10 >1. 9× 1010 >3 <40 CEPC Injector Linac design 4

Introduction Layout of Linac Positron Linac ESBS FAS 50 Me. V DR PSPAS 4 Ge. V 200 Me. V Ø ESBS ( Electron Source and Bunching System) • 50 Me. V && 11 n. C for positron production Ø FAS (the First Accelerating Section) • Electron beam to 4 Ge. V && 10 n. C for positron production Ø PSPAS (Positron Source and Pre-Accelerating Section) SAS 1. 1 Ge. V TAS 4 Ge. V 10 Ge. V Ø SAS (the Second Accelerating Section) • Positron beam to 4 Ge. V && 3 n. C Ø DR (Damping Ring) • Positron beam 1. 1 Ge. V, 60 m Ø TAS (the Third Accelerating Section) • Positron beam to 10 Ge. V && 3 n. C • Positron beam larger than 200 Me. V && larger than 3 n. C ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 5

Introduction Layout of Linac Electron Linac ESBS EBTL FAS 50 Me. V DR PSPAS 4 Ge. V 200 Me. V Ø ESBS ( Electron Source and Bunching System) • 50 Me. V && 3 n. C Ø FAS (the First Accelerating Section) • Electron beam to 4 Ge. V && 3 n. C ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA TAS SAS 1. 1 Ge. V 4 Ge. V 10 Ge. V Ø EBTL (Electron Bypass Transport Line) • Electron beam @ 4 Ge. V && 3 n. C Ø TAS (the Third Accelerating Section) • Electron beam to 10 Ge. V && 3 n. C CEPC Injector Linac design 6

Introduction ESBS EBTL PSPAS FAS 50 Me. V Layout of Linac 4 Ge. V 200 Me. V ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA DR 1. 1 Ge. V SAS TAS 4 Ge. V 10 Ge. V CEPC Injector Linac design 7

Source design Electron source ØThermionic Triode electron gun ØSub-harmonic pre-buncher Parmela • 142. 8375 MHz • 571. 35 MHz ØBuncher & A 0 • 2856. 75 MHz ØEmittance • <100 mm-mrad (Norm. Rms) @11 n. C ØTransmission • ~90% ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 9

Source design Positron source ØLayout of positron source • Target (Conventional) ü tungsten@15 mm ü Beam size: 0. 5 mm • Electron Beam ü 4 Ge. V/10 n. C/100 Hz ü Beam power 4 k. W • Energy deposition ü 0. 784 Ge. V/e- @ FLUKA ü 784 W water cooling • AMD (Adiabatic Matching Device) ü Flux Concentrator ü Length: 100 mm ü Aperture: 8 mm 26 mm ü Magnetic field: (5. 5 T 0 T) + 0. 5 T ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 10

Source design Positron source ØLayout of positron source • Capture & Pre-accelerating structure ü Length: 2 m ü Aperture: 25 mm ü Gradient: 22 MV/m • Chicane ü Wasted electron separation • Norm. RMS. Emittance ü ~2400 mm-mrad ~120 nm@10 Ge. V • Energy: >200 Me. V • Positron yield ü Ne+/Ne- > 0. 5 @ [-8°, 12°, 235 Me. V, 265 Me. V] ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 11

Linac design Electron linac • Focusing device: Triplet • 1 triplet+4 Acc. Stru. 1 triplet+8 Acc. Stru. • Operation mode : • High charge mode (positron production) • 4 Ge. V & 10 n. C • ESBS+FAS • Low charge mode (electron injection) • 10 Ge. V & 3 n. C • ESBS+FAS+EBTL+TAS ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 13

Linac design Electron linac Electron injection ØLow charge mode • 10 Ge. V with 3 n. C charge • Energy spread (rms): 0. 15% • Emittance (rms): 5 nm ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 14

Linac design Electron linac Positron production ØHigh charge mode • 4 Ge. V with 10 n. C charge • Energy spread (rms): 0. 6% ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 15

Linac design Positron linac ØPSPAS SAS (DR) +TAS • SAS: 200 Me. V 4 Ge. V • Damping Ring @ 1. 1 Ge. V • TAS: 4 Ge. V 10 Ge. V ØTransverse focusing devices • FODO structure at low energy • Triplet at high energy ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 16

Linac design Positron linac ØPositron linac • 10 Ge. V with 3 n. C charge • Energy spread (rms): 0. 16% • Emittance with DR (rms): 40(H)/24 nm(V) ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 17

Linac design Misalignment errors with correction Ø Whole Linac • One-to-one correction method for both e- and e+ • Errors: Gaussian distribution, 3σ truncated e- Ø Beam orbit • <1 mm • <0. 5 mm at high energy region Error description Unit Value Translational error mm 0. 1 Rotation error mrad 0. 2 % 0. 1 mm 0. 1 Magnetic element field error BPM uncertainty ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA e+ CEPC Injector Linac design 18

Linac design Misalignment errors with correction Ø 4 Ge. V Electron Linac with high charge • Method: First orbit correction + multiparticles simulation • Low charge ü Beam orbit can be controlled well • High charge ü Misalignments of Acc. Tubes ü Wakefield • In a real operation, correction is based on multi-particles orbit, so the orbit and emittance growth can be controlled better. ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 19

Linac design • Simulation condition • 5000 seeds • Accelerating structure • phase errors and amp errors • 4 accelerating structures in one KLY • 3σ--Gaussian ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA Field errors • Energy jitter: 0. 2% • Energy spread < 0. 2% • Phase errors: 0. 5 degree (rms) • Grad. errors: 0. 5% (rms) CEPC Injector Linac design 20

Linac design DR V 1. 0 Energy Circumference Repetition frequency Bending radius Dipole strength B 0 U 0 Damping time x/y/z 0 0 Nature z inj ext x/y inj / ext Energy acceptance by RF f. RF VRF Unit Ge. V M Hz M T ke. V ms % mm. mrad % % MHz MV Damping Ring Value 1. 1 58. 5 100 3. 62 1. 01 35. 8 12/12/6 0. 05 287. 4 7 (23 ps) 2500 704/471 0. 3/0. 06 1. 0 650 1. 8 ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA @ D. Wang CEPC Injector Linac design 21

Summary ØThe CEPC linac works with 100 Hz repetition, 10 Ge. V and one-bunch-perpulse, which can meet the requirements of Booster; ØThe linac have the potential to provide positron beam and electron beam with bunch charge larger than 3 n. C; ØOne preliminary damping ring is proposed, the emittance with DR is smaller than 40 nm; ØUp to now, there’s no bottleneck in linac design and further works continues. ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 23

Thank you! ICHEP 2018, July 4 -11, COEX, SEOUL, KOREA CEPC Injector Linac design 24

Dynamic aperture with errors • • With only COD corrections, DA is nearly two thirds of bare lattice At 120 Ge. V, radiative damping was considered. DA requirement @ 10 Ge. V determined by the beam stay clear region DA requirement @ 120 Ge. V: 1) H- quantum lifetime, 2) V- re-injection process from the collider in the on-axis injection scheme 120 Ge. V 10 Ge. V w damping BSC DA requirement 10 Ge. V ( x= y =120 nm) 120 Ge. V ( x=3. 57 nm, y= x*0. 005) H 4 x +5 mm 6 x +3 mm V 4 y +5 mm 49 y +3 mm DA results H 7. 7 x +5 mm 21. 8 x +3 mm • Requirement for linac emittance: < 150 nm, otherwise BSC > beam pipe V 14. 3 y +5 mm 779 y +3 mm