Sppc injector chain design update Yuanrong Lu Peking University

Special thanks to : Yuanrong LU, Haipeng LI, Qiuyun TAN, Xiaowen ZHU, Zhi WANG, Kun ZHU, Peking University Xiangqi WANG, Tao LIU, Hongliang XU , NSRL, USTC Jingyu TANG, Feng SU, Hong Yang, et al, IHEP Linhao ZHANG, Chuanxiang TANG, Tsinghua University And lots of colleagues from individual affiliations are not mentioned here.

Outline : Injector chain (for proton beam) p-Linac: proton superconducting linac p-RCS: proton rapid cycling synchrotron MSS: Medium-Stage Synchrotron SS: Super Synchrotron Ion beams have dedicated linac (i-Linac) and RCS (i-RCS)

Major parameters Value Unit p-Linac MSS Energy 1.2 GeV 180   p-Linac MSS Energy 1.2 GeV 180 Average current 1.4 mA 20 uA Length ~300 m Circumference 3500 RF frequency 325/650 MHz 40 Repetition rate 50 Hz 0.5 Beam power 1.63 MW 3.67 p-RCS SS 10 2.1 TeV 0.34 Accum. protons 2.55E14 900 7200 36-40 200 25 Repetition period 30 s 3.4 Protons per bunch 2.0E11 Dipole field 8 T

p-Linac parameters: Parameter Value Unit Particle type H- Beam energy 1.2 GeV Superconducting cavities for >20MeV Beam rigidity 6.4 Tm RF frequency 325/650 MHz 325 for <160MeV, 650 for >160MeV Peak current 40 mA Repetition rate 50 Hz RF duty factor 3.4% Chopping rate 50% For injection to p-RCS Average current 1.4 Half for RCS injection Beam power 1.63 MW Without chopping, for linac beam applications 1. 斩束率为50% 2. P-RCS为25Hz, 一半注入RCS，一半直接引出做束流

Many high energy p-Linac based on SNS, ADS project. Superconducting cavity has great development. Almost mature technology. Key question: high acceleration gradient, chopper Project Energy (GeV) Beam power (MW) Duty factor (%) Length (m) Current (mA) SC input (MeV) Frequency (MHz) LHC 5.0 0.08…10 590 40 160 352.2 MYRRHA 0.6 2.4 100 260 4 17 176/352 ESS 2.0 5 4.0 362 62.5 90 352.21 C-ADS 1.5 150 10 3.2/2.1 325 SNS 1.0 2 6 335 65 186 402.5 超导加速器适用的能量也越来越低

LHC-Linac4 & SPL Linac4: room temperature accelerator SPL (Superconducting Proton Linac) 两种超导椭球腔 R. Garobay, Geneva, “SPL AT CERN”, SRF2009

European Spallation Source (ESS) Parameter Value Ion P Energy (GeV) 2.0 Beam power (MW) 5 Repetition rate (Hz) 14 Beam Current (mA) 62.5 Beam pulse (ms) 2.86 Duty factor (%) 4 The input energy to the SC linac is 89.8 MeV out of DTL. Total length (before HEBT) is about 362m 常温加速器，通过RFQ和DTL将加速到90MeV，超导部分包括spoke腔和两种椭球腔 M. Eshraqi, et al, “The ESS LINAC”, IPAC2014, M. Eshraqi, H. Danared, et al, “ESS LINAC, DESIGN AND BEAM DYNAMICS”

MYRRHA—RFQ RFQ为4杆型，176MHz, 出口能量为1.5MeV，长度达到了4m，极间电压只有40kV，功耗只有100KW。 C.Zhang, et al, “Front-end linac design and beam dynamics simulations for MYRRHA”, LINAC2012

MYRRHA—CH DTL C.Zhang, et al, “Front-end linac design and beam dynamics simulations for MYRRHA”, LINAC2012

C-ADS Li, Zhihui, et al. "Physics design of an accelerator for an accelerator-driven subcritical system." PHYSICAL REVIEW SPECIAL TOPICS-ACCELERATORS AND BEAMS 16.8(2013):080101.

SppC p-linac RFQ, CH-DTL, Spoke cavity & elliptical cavity. 160MeV 3.0MeV 20MeV 1200MeV RFQ CH-DTL Spoke Elliptical MEBT1 MEBT2 LEBT Ion 325MHz 650MHz 0.05MeV RFQ, CH-DTL, Spoke cavity & elliptical cavity. Superconducting linac for >20MeV RFQ, DTL and spoke cavities operate at 325MHz, elliptical cavities operate at 650MHz. 基于上面质子直线加速器的设计，给出SppC质子直线加速器的布局， 超导加速器有较大的孔径，高的加速梯度，相比常温加速器，具有很大的优势，超导加速器能量相对较低，20MeV，beta=0.20 超导spoke腔发展迅速，CH-DTL可以用低beta的spoke腔替代

Main RFQ parameters Parameters value Frequency (MHz) 325 Input/output energy(MeV) 0.05/3.0 Beam Current(mA) 40 Transmission(%) 98.5 Vane voltage(kV) 85 Maximum surface field(MV/m) 31.97 Kilpatrick Factor 1.79 Vane Length(cm) 361.32 Synchronous Phase(deg) -90/-25 Maximum Modulation 2.308 Average Aperture(cm) 0.278 Minimum Aperture(cm) 0.20 Input transverse x,y,norm,rms(mm-mrad) 0.250 Output transverse x,y,norm,rms (mm-mrad) 0.232 Vane voltage keep constant at 85kV, and Kp factor is 1.79. RFQ length is 3.6m Four-vane RFQ cavity power dissipation is about 440kW.

RFQ Dynamic Parameter Φs—— Synchronous phase B —— Focusing strength Ws —— Synchronous energy Φs—— Synchronous phase m —— Modulation factor a —— Minimum bore radius

Beam transmission given by ParmteqM RFQ Simulation Particle distribution in the transverse phase space at the entrance (top) and exit (bottom) of the RFQ Beam transmission given by ParmteqM Input transverse x,y,norm,rms(mm-mrad) 0.250 Output transverse x,y,norm,rms (mm-mrad) 0.232 Output longitudinal z,norm,rms (MeV-deg) 0.1106

Different 4-vane RFQs Project SppC C-ADS CSNS CPHS SNS LINAC4 particle Frequency(MHz) 325 324 402.5 352.2 Win (MeV) 0.05 0.035 0.065 0.045 Wout (MeV) 3.0 3.2 2.5 Duty factor 3.4 100 1.05 6.0 0.1-10 Peak current(mA) 40 15 20 50 52 10-80 Vane voltage(kV) 85 55 80 60~130 83 78 Length(cm) 361.32 469.95 362 296.87 370 300 Transmission(%) 98.5 98.7 97 97.2 >90 95 Maximum surface field(MV/m) 31.97 (1.79Ek) 33.0 (1.85Ek) 31.68 (1.78EK) 32.0 (1.8Ek) 1.85 1.84 Cavity power dissipation(kW) 440 420 390 538 800 一些项目相似的RFQ的对比，

Crossbar H-Type DTL CH-Type DTL: velocity range: 𝛽=0.1-0.5 frequency: 150 ~ 700MHz. High mechanical stability KONUS Dynamics High real estate gradient Small cavity Easily cooled Room temperature- and superconducting operation 352 MHz,Win = 3 MeV/u 横向聚焦通过四级磁铁实现，纵向聚焦通过几个-35°相位的聚束间隙实现。 Crossbar H-Type DTL is usually the right candidate for KOUNS designs in the velocity range beat=0.1-0.5 and for resonance frequencies between 150 and 700MHz typically. CH-cavities have an excellent mechanical rigidity due to the crossed stems and can be easily cooled. This opens the possibility of high duty cycle or superconducting multi-cell cavity applications of the CH structure.

KONUS Dynamics One structure period consists of a quadrupole triplet, a rebunching section and a main acceleration section. Main acceleration along a 0° synchronous particle structure with asynchronous beam injection and a surplus in bunch synchronous particle. 加速聚集分离作用 Main acceleration at Φs = 0°, by a multi-gap structure (1). Transverse focusing by a quadrupole triplet or solenoid (2). Rebunching: 2 - 7 drift tubes at Φs = - 35 ° typically (3).

DTL parameter Only need about 5m. Two Coupled CH (CCH) cavity Simulation based on LORASR code & TraceWin Cavity power Cavity CCH1 CCH2 Input(MeV) 3.0 8.1 output energy 20.2 Mean beta 0.108 0.172 Length (cm) 145 315 Gap number 11+13 17+18 Acceleration gradient (MV/m) 3.50 3.84 Max field (MV/m) 13.09 17.78 𝑍 𝑒𝑓𝑓 𝑐𝑜 𝑠 2 ∅ 𝑠 (MΩ/m) 70 60 Cavity power(kW) 260 770 CH-DTL has high accelerate gradient ~5m, CSNS DTL Tank1 up to 21MeV @ 8m 第二个腔加速梯度大，长，功耗很大

Beam envelope

Beam envelope

Beam envelope

Emittance growth(40mA)

FAIR The proposed layout for the FAIR Proton injector G. Clemente, et al, The FAIR project linac: the first linac based on a room temperature CH-DTL, HB2010

Coupled-CH (CCH) cavity

MYRRHA: Multi-purpose hYbrid Research Reactor for High-tech Applications 1. 常温加速器为RFQ和CH-DTL，工作在176MHz，加速到17MeV，超导部分为352MHz的spoke和704MHz的椭球腔。 During the EUROTRANS project the RF frequency of the 17 MeV injector part has been set to 352MHz. The new layout is changed to 176 MHz. The main reason is the possibility to use a flexible and cheap 4-rodRFQ instead of the 4-vane-RFQ. This 176 MHz RFQ accelerates the particles to 1.5 MeV. M.Vossberg, H.Klevin, et al, “Test RFQ for the MAX-Project”, LINAC 2012

SC cavity 4 sections of constant beta cavities Spoke cavity (20~160MeV, 325MHz) Single spoke resonator (SSR) Double spoke resonator (DSR) elliptical cavity(160~1200MeV, 650MHz) 5 cell/ 6 cell 𝛽=0.4 Spoke cavity 5 cell elliptical cavity

CM1+CM2带束调试达到项目验收指标 超导腔 成功加速10.6mA脉冲质子束至10.6MeV CM1+CM2：每个恒温器包含7个由超导腔、超导螺线管、BPM组成的周期单元，共14个周期单元——首次、无先例可循 CM2腔在老练时达到7-10MV/m，运行在5－7MV/m 成功加速10.6mA脉冲质子束至10.6MeV Weiming PAN

6只用于25MeV的CM4正式腔性能测试达到国际先进指标 超导腔 主加速器Spoke021腔成功研制和批量制造 6只用于25MeV的CM4正式腔性能测试达到国际先进指标 Weiming PAN

Spoke cavity (20~160MeV, 325MHz) Elliptical cavity(160~1200MeV, 650MHz) The TTF versus a ratio of beam velocity β to the optimum βopt

SC cavity 20MeV 0.20 50MeV 0.31 160MeV 0.507 350MeV 0.685 1200MeV SSR026 325MHz Elliptical 062 650MHz Elliptical 082 DSR041 20MeV 0.20 50MeV 0.31 160MeV 0.507 350MeV 0.685 1200MeV 0.899 Cavity type frequency（MHz） Focusing type β No. of cavities Energy range (MeV) Focusing period Cryomodules Spoke 325 Solenoid 0.22 32 20—50 SR 8 0.42 40 50—160 SRR Elliptical 650 Triplet 0.62 44 160—350 TR(4) 11 0.82 85 350—1200 TR(5) 17 As can be seen from the figure, a small number of cells cavity provides a large velocity acceptance. On the other hand, using a larger number of cells/cavity has the advantage of reducing the overall number of system components, system size and system complexity. As a compromise between the two, in our design, we have chosen 5 cells/cavity. the entire energy range from 100 MeV to 1 GeV is divided into 3 sections of constant beta cavities as shown in Fig. 9.

Spoke Cavity Fremi SSR0 325 0.115 109.2 5.66 6.83 SSR1 0.215 242 3.84 Lab Spoke Type Frequency (MHz) 𝛽 𝐺 R/Q （Ω） 𝐸 𝑝 / 𝐸 𝑎𝑐𝑐 𝐵 𝑝 / 𝐸 𝑎𝑐𝑐 mT/(MV/m) Fremi SSR0 325 0.115 109.2 5.66 6.83 SSR1 0.215 242 3.84 5.81 SSR2A 0.414 247 3.78 5.64 SSR2B 0.480 304 3.5 5.9 IHEP Single-Spoke 0.12 142 4.54 6.37 0.21 206 3.88 8.13 0.40 250 3.678 8.31 Argonne SSR 350 251 4.0 DSR 345 3.47 TSR 0.30 492 2.77 0.63 349 2.92

Works under going p-RCS/i-RCS: Tang Jingyu and Zhang Linhao MSS: a student studying lattice (with Tang Jingyu, pending) SS: Wang Xiangqi and students

More about p-RCS p-RCS will serve not only medium-stage acceleration for colliding beams at SPPC, but also other physics programs. It is designed to work with high-duty factor The continuous beam power from p-RCS is 3.5 MW. No other similar accelerators have been built or studied in details (FNAL is conducting a study to replace its 8-GeV Booster). High repetition rate of 25 Hz will shorten the beam filling time in the MSS. Only a fraction of this power is needed to fill the MSS. Thus most of the beam pulses from the p-RCS could be used for other physics programs. p-RCS will use mature accelerator technology but be on a larger scale than existing rapid-cycling proton synchrotrons. Examples: CSNS/RCS, J-PARC/RCS, ISIS/RCS, FNAL/Booster, NF/RCS

Injector chain for SPPC 1 Hong YANG Jingyu TANG Injector chain for SPPC  

MSS Lattice design 1.Vladimirskij and Tarasov reversed bending magnets 2.Teng π-straight sections 3.S.Y.Lee flexible momentum compaction FMC 4. Yu.Senichev “resonant” lattice

Pi-straight sections

Resonant lattice

Superperiods and Circumference

Magnets and RF B gap=38.4mm H=51.2mm Sagitta 11.8mm Q r=25.6mm

Injection and Extraction 向MSS注入:快注入 固定靶等实验:多圈慢引出 向SS注入:单圈快引出 单圈注入：一个束团注到一个空的 RFbucket 内

Parameters List

CEPC-SPPC CCNU Symposium Recent progress of the design study on the SS USTC Group: Xiangqi WANG, Tao LIU, Hongliang XU IHEP Group: Feng SU, Jingyu TANG 报告题目不好，建议改为：Recent progress of the design study on the SS CEPC-SPPC CCNU Symposium Apr. 19-21, 2017, IHEP, Wuhan 2018/12/5

2018/12/5

Recent progress The main design objectives, 2.1 TeV-7200 m, unchanged Reduce working magnetic field, from 9.0319 T to 8.2397 T Constant number of SC dipole magnets Constant effective length of each SC dipole magnet 4804 of harmonics number Circumference to meet longitudinal stability 88 arc FODO cell: 4 dipoles, 2 quadrupoles, 2 sextupoles 16 no-standard arc FODO cell: 4 dipoles, 2 quadrupoles 4 long straight sections used for SCRF cavities & inj. or ext. Have filed a patent application 2018/12/5

Have not changed over the past year 2018/12/5

To meet the requirement of dynamic aperture tracking Total length is 7201.014123 m. Two super period structure Four long straight sections: 2 for injection or extraction; 2 for RF cavities and other equipments 2018/12/5

Comparison of variable parameters before 19 Apr. 2017 质子静止能量：938.2720813（58）MeV。299792428.1. 2018/12/5

The new arrangement reduces the working magnetic field * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

To increase the transverse focusing effect * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

The beta function is reduced by 56.4% 2018/12/5

The beta function of arc region is reduced * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

The dispersion function at the ends of arc region is reduced to zero * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

To meet the requirements of synchronization * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

The beta function of RF installation location is reduced by 57.5% The beta function of RF installation location No change in the length of the long line segments * Assuming the injection filling factor from MSS to SS is 80% for inj. or ext. 2018/12/5

Beta function curve of RF cavity segment * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

No change in the length for inj. or ext. * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

Beta function of long straight section for inj. or ext. * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

Structure and Twiss function of a super period * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

Beam bunch structure parameters of SS * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

synchrotron radiation, cavity pressure & power Energy storage, synchrotron radiation, cavity pressure & power * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

Physics performance of kickers in SS ring * Assuming the injection filling factor from MSS to SS is 80% 2018/12/5

Tune-x & tune-z in the SS ring/SPPC 29.5460, 28.5930 2018/12/5

Dynamic aperture by Six Track: 40.322 mm, 80.680 mm 29.5460, 28.5930 2018/12/5

Summary Injector chain is a very complicated and powerful accelerator system, large enough by a single stage Work on the injection chain continues, and more volunteers (both experts and students) are needed. Key technical challenges should be identified, so R&D program can be pursued. Collaboration and coordination are needed. Beam applications or physics programs of each stage will be discussed.