Beam Commissioning Results of CSNS Linac Jun Peng

Beam Commissioning Results of CSNS Linac Jun Peng Zhiping Li On behalf of CSNS accelerator physics group 散裂中子源进展汇报 February 19, 2021 Page

OUTLINE • Introduction • Front End Commissioning • RF Tuning • Transverse Matching • Orbit Correction • Summary 散裂中子源进展汇报 February 19, 2021 Page 2

Introduction : CSNS Project 50 ke. V H- Ion source 3 Me. V RFQ 80 Me. V DTL 50 ~ 500 μs 25 Hz 1 MHz 50% chopping rate 500 ns -> 100 ns Target station 、Spectrometer and instruments Beam power: 100 散裂中子源进展汇报 February 19, 2021 k. W 1. 6 Ge. V 25 Hz RCS Page

Electrostatic chopper H- Linac of CSNS EMQ FFDD lattice Parameters of CSNS Linac Time Structure of Linac Beam Pulse Ion Source RFQ DTL 0. 05 3. 0 80 20/40 15/30 RF frequency (MHz) 324 Chop rate (%) 50 50 1. 05 Input Energy（Me. V) Output Energy(Me. V) Pulse Current (m. A) 散裂中子源进展汇报 February 19, 2021 Duty factor (%) 1. 3 Repetition rate (Hz) 25 25 Page 25

Commissioning of CSNS Linac u #1 Front end, full power (500μs, 25 Hz, chopped) u #4 DTL tank 1 -3, reduced beam power (100μs, 1 Hz, unchopped) u #2 DTL tank 1, reduced beam power (200μs, 5 Hz, chopped) u #5 DTL tank 1 -4, reduced beam power (100μs, 1 Hz, unchopped) u #3 DTL tank 1, full power (500μs, 25 Hz, chopped) 散裂中子源进展汇报 February 19, 2021 u #6… DTL tank 1 -4, reduced beam power (200~400μs, 1 Hz, unchopped) Page 5

1. Front End Commissioning 散裂中子源进展汇报 February 19, 2021 Page 6

Commissioning of Ion Source • Aim: less spark and higher stablity：major effort focus on long term operation with high stability, related to source body, HV supply, Cesium Temp. , EMC, …… • Result: Times: 9 in 48 Hours Duration：～ 30 s Times: 4 in 72 Hours Duration：～ 0. 05 s 散裂中子源进展汇报 February 19, 2021 Page

Chopper in LEBT Courtesy of H. F. Ouyang, FE group, CSNS 散裂中子源进展汇报 February 19, 2021 Page 8

Chopping experiments Both the rise/fall time for the chopped beam is about 4 -5 periods of the working RF(1 period T=3. 086 ns) 9 散裂中子源进展汇报 February 19, 2021 Measured effect of chopper on the beam Page

Beam Commissioning of RFQ CT measurement: beam 19, transmission ～ 93% 散裂中子源进展汇报 February 2021 Design Achieved Peak current [m. A] 15 17 Beam energy[Me. V] 3. 025 3. 02± 0. 015 Chopping rate [%] 50 50 Pulse width [μs] 420 500 Pulse repetition rate [Hz] 25 25 Page 10 =0. 27 Emittance(PI mm-mrad): simulated=0. 22, Measured

2. RF TUNING 散裂中子源进展汇报 February 19, 2021 Page

RF Tuning：Setting RF amplitude and phase Ø Phase Scan Signature Matching Method XAL, Pasta (an RF phase scan and tuning application) Model: • Input energy • RF amplitude • Cavity phase offset 散裂中子源进展汇报 February 19, 2021 Page 12

Phase Scan of Bunchers Measured phase differences with two FCTs Φcavity =-60. 097 o Buncher 1 散裂中子源进展汇报 February 19, 2021 Measured phase differences with two FCTs Φcavity =27. 857 o Buncher 2 Page

DTL 1 Amp= Phase scan results of 4 DTL tanks 散裂中子源进展汇报 February 19, 2021 Page

Energy Measurements (Phase Scan &TOF) Beam energy from two methods RFQ DTL 1 DTL 2 DTL 3 DTL 4 Design [Me. V] 3. 026 21. 669 41. 415 61. 072 80. 01 Phase scan [Me. V] 3. 029 21. 802 41. 52 60. 917 79. 87 TOF [Me. V] 3. 027 ± 0. 01 21. 685± 0. 01 41. 566± 0. 14 61. 09± 0. 34 80. 28± 0. 10 The energy deviation is all< 1% 散裂中子源进展汇报 February 19, 2021 Page

3. Transverse Matching 散裂中子源进展汇报 February 19, 2021 Page

Transverse Emittance Measurement Measured beam distribution at EM X’（rad） X’（mrad） Simulated beam distribution at EM X（mm） Y’（mrad） Y’（rad） X（cm） Y（mm）散裂中子源进展汇报 February 19, 2021 Page

Twiss Parameter Measurement 4 wire scanners XAL：Beam Envelopes Fitting 散裂中子源进展汇报 February 19, 2021 （Red：x-rms Blue： y-rms） Page 23

Twiss Measurement Results by WSs Twiss Parameters and emittance at RFQ Exit α β Emittance (norm. rms) [mm/mrad] [πmm mrad] Horizontal Measured(10 m. A) -2. 28 0. 335 0. 215 Measured(14 m. A) -2. 35 0. 328 0. 243 Designed -1. 773 0. 233 0. 215 Measured(10 m. A) 1. 1 0. 076 0. 213 Measured(14 m. A) 1. 2 0. 077 0. 243 Designed 0. 639 0. 074 0. 212 Vertical 散裂中子源进展汇报 February 19, 2021 Page

Fringe Field Effect of MEBT Magnets Ø Huge difference in Twiss parameters between hard edge model and slice model Ø Fringe field of magnets are considered in matching, DTL transport efficiency： 96% 99% Len_Quad~79 mm 散裂中子源进展汇报 February 19, 2021 Page

Transverse Matching of DTL Horizontal Linac Lattice Model Vertical MEBT DTL u 161 Quadrupoles in DTL, based on FFDD Structure 散裂中子源进展汇报 February 19, 2021 Page

Drift Tube Fault D D F F T 1 Q 13 Envelope with T 1 Q 13 ON D 0 F F T 1 Q 13 散裂中子源进展汇报 February 19, 2021 Envelope with Only T 1 Q 13 OFF Page

Rematch of DTL Lattice D 0 0 F Envelope with T 1 Q 13 + T 1 Q 14 OFF F D 0 D F F D 散裂中子源进展汇报 February 19, 2021 Envelope after rematch Page

Beam Profiles Comparison LRWS 01 LRWS 02 1*Quad Off 散裂中子源进展汇报 February 19, 2021 LRWS 02 2*Quads Off LRWS 01 LRWS 02 Rematch Page

Beam at DTL Exit Simulated Result (PARMILA) 散裂中子源进展汇报 February 19, 2021 Measured Result Page

Matching of LRBT （Linac to Ring Beam Transport Line） Before matching After matching 散裂中子源进展汇报 February 19, 2021 Red line ： X direction Blue line ： Y direction Page

4. Orbit Correction 散裂中子源进展汇报 February 19, 2021 Page 3 0

MEBT Orbit Correction Before correction maximum: ± 1. 5 mm 散裂中子源进展汇报 February 19, 2021 After correction maximum: ± 0. 15 mm Page 28

LRBT Orbit Correction before correction maximum: ± 14 mm （x, x', y, y'）=(0. 35 mm, 1 mrad, 1. 4 mm, 1. 7 mrad) after correction maximum: ± 2 mm 散裂中子源进展汇报 February 19, 2021 Page 29

Summary • The Front-end and DTL 1 -4 have been fully commissioned, the primary design goals of Ipk & Iavg, transverse emittance and beam energy have been achieved. • The DTL output energy, measured by phase scan method, agrees well with that measured by time-of-flight method. • Beam transmission efficiency and beam loss are well optimized. More work needs to be done on halo's formation mechanism and inhibition method. 散裂中子源进展汇报 February 19, 2021 Page 30