The Preparation for CSNS Accelerator Commissioning Sheng Wang

The Preparation for CSNS Accelerator Commissioning Sheng Wang June 8, 2015, Dongguan

Outline Ø A brief review to CSNS accelerator Ø The planned commissioning schedule Ø Preparation for accelerator commissioning Ø The Linac commissioning plan Ø The RCS commissioning plan Ø Discussion

A brief introduction to CSNS 3

Linac design CT FCT Tank 1 Tank 2 CT FCT Tank 3 Tank 4 Tank number 1 2 3 4 total Output energy (Me. V) 21. 67 41. 41 61. 07 80. 09 Number of cell 64 37 30 26 157 RF driving power (MW) 1. 35 1. 32 1. 34 5. 33 Total RF power (MW) (I=15 m. A) 1. 62 1. 63 6. 49 Accelerating field (MV/m) 2. 86 2. 96 3. 0 Synchronous phase (degree) -35 to -25 -25

RCS design l. Lattice consists of 16 triplet cells l. Small magnet aperture l. Dispersion-free long uninterrupted straight l. Straight at arc with large dispersion ¡Arcs: Triplet cells as achromatic insertion ¡Straights: Triplet, 3. 85× 2+11 m long drifts at each straight ¡Gap of Dipole : 160 mm ¡Max. Aper. Of Quadrupoles: 272 mm 5

Tune Diagram for 4 -fold Structure red： 1 st order structure resonance golden： 2 nd 1 st order structure resonance blue： 3 rd order structure resonance green： 4 th order structure resonance gray： 3 rd deference structure resonance pink：coupling resonance 6

Beam dumps Beam energy Power limit Linac-dump 1 250 Me. V 4 k. W Linac-dump 2 250 Me. V 0. 2 k. W Temp-dump 30 Me. V 0. 16 k. W Inj-dump 250 Me. V 2 k. W RCS-dump 1. 6 Ge. V 7. 5 k. W

Beam parameters for commissioning Peak current Pulse width Repetition 5 -15 m. A 50 -100μs 1 Hz Commissioning 15 m. A goal for acceptance 420μs 5 Hz Design 15 m. A 420μs 25 Hz Single shot 5 -15 m. A 150 ns~420μs Short-pulse

Planned commissioning Schedule IS+LEBT 2015. 4. 14 -2015. 4. 14 RFQ+MEBT 2015. 4. 15 -2015. 7. 8 DTL 1 2015. 10. 20 -2015. 12. 21 DTL 2 -4+LRBT 2016. 7. 25 -2016. 11. 14 RCS 2016. 11. 15 - 2017. 7. 24 RTBT 2017. 7. 25 – 2017. 9. 4 First beam on target 2017. 9. 5 Beam power to 10 k. W 2017. 8. 1 -2017. 9. 30 CSNS to acceptance goal 2017. 12. 31 Official acceptance 2018. 3 Beam power to 100 k. W 2018. 3. 1 -2021. 3. 1

Preparation for the beam commissioning

Simulation study for DTL commissioning 11 Emittance growth with different lattice structure（I=15 m. A）

Beam size with different lattice structure（I=15 m. A） 12

Calculating the emittance parameter at the exit of RFQ DTL WS 1 WS 4 WS 2 WS 3 Simulation by using PARMILA, I=15 m. A

Simulation study on DTL phase scan Signature matching Examples of the phase scan signature-matching technique for the DTL-1 at the CSNS

Tracking Error and Control The harmonic injection in time domain plays a key role in the control of the tracking errors among the main magnets of RCS in AC mode operation. 15

The Field Compensation by Harmonic Injection Dr. Shouyan Xu The field deviation from pure 25 Hz sinusoidal curve, before and after harmonic injection. The effect of harmonic injection. The harmonic injection is based on the individual measurement.

Magnet sorting

The study on the injection orbit matching

Model measurement and correction For k=1, 2, 3, …. , n; we can get and BPM offset can be solved: ,

Application software development Dr. Weibin Liu Ø First step: transplanting and modifying XAL to CSNS Ø Second step: developing the applications according to requirement of CSNS commissioning Ø Move from XAL to Open XAL Based on the application of virtual accelerator, many functions have been performed by transplanting XAL or developing 20

Linac Commissioning Plan

MEBT commissioning PR, EM(1) MEBT is comprised of: 10 electrical megnets 6 Steering magnets 2 Bunchers Beam diagnostics including: 8 BPMs 2 CTs 5 FCTs 4 Wire Scanners 1 Emittance Monitor

Ø Longitudinal tuning Find the RF set point of buncher cavities with a phase scan method. The amplitudes of two bunchers will be optimized finally by the beam transmission rate at the exit of DTL-1. Ø Transverse tuning Beased on the values of measured beam parameters, calculate the emittance and Twiss parameters at the exit of RFQ, and then the quadrupole gradient is determined based on the calculated emittance parameters.

DTL commissioning CT FCT Tank 1 Tank 2 CT FCT Tank 3 Tank 4 Temporal Beam Diagnostic system: 1 BPM, 1 CT, 2 FCT, 1 QEM, 1 x-y steering magnet, 1 EM, 1 WS 1 Energy degrader /Faraday cup, 1 Beam dump(0. 163 k. W) Tank number 1 2 3 4 total Output energy (Me. V) 21. 67 41. 41 61. 07 80. 09 Number of cell 64 37 30 26 157 RF driving power (MW) 1. 35 1. 32 1. 34 5. 33 Total RF power (MW) (I=15 m. A) 1. 62 1. 63 6. 49 Accelerating field (MV/m) 2. 86 2. 96 3. 0 Synchronous phase (degree) -35 to -25 -25

DTL-1 commissioning Ø Measuring the transmission rate The RF of DTL-1 is turned off and the quadrupole setting is 3 Me. V beam transport line mode. Ø Longitudinal tuning Find the RF set point of DTL-1 with a phase scan method. The tuning goal of the RF set point is 1 deg in phase and 1% in amplitude. Ø Match between RFQ and DTL Longitudinal match –- transmission rate Transverse match --- emittance at the exit of the DTL

DTL-2 , 3, 4 commissioning Ø The three tanks will be tuned one by one Ø The tuning procedure for each tank is similar to the DTL-1.

RCS , LRBT and RTBT Commissioning

Commissioning goal of first stage Ø Bring the LRBT, RCS, and RTBT (up to the Extraction Dump/target) into beam operation Ø Characterize the primary beam parameters with low beam intensity Ø Establish and validate the whole commissioning procedures which will used for the high intensity normal operations Ø Study the dependence of beam performance on various tuning parameters Ø Study various error effects on the beam Ø Study the beam loss, and measure the beam losses to determine threshold of beam loss for MPS

Diagnostics for RCS and Beam line commissioning Section CT FCT BPM BLM LRBT 2 20 28 RTBT 4 Inj. Dump 1 33 2 50 3 2 1 R-Dump 2 6 1 3 1 SCT MCT DCCT FCT RCS 1 1 1 3 FBLM WS 7 MWPM 3 5 8 2 1 1 WCM BPM 2 WCM BLM FBLM tune 32+3 72 9 2

LRBT commissioning Ø Transporting a beam through the LRBT line (including linac dump line), the RCS injection region, the injection dump line and to the injection dump; Ø Commissioning the diagnostic devices, BPMs, BCMs, WSs, then measure the beam energy, emittance, trajectory and optics; Ø The dispersion in LRBT can be measured by adjusting the linac energy via the accelerating phase of the last cavity; Ø In the beginning, the beam can be tracked by both BPM and BLMs; Ø The beam orbit can be corrected by correctors to minimize the beam loss; Ø The optics model can be re-calculated and calibrated based on the measured emittance , twiss parameters and the beam profiles as constraints; Ø Linac beam ready to inject into RCS…

RCS commissioning – injection Ø In day 1 commissioning, large stripping foil will be used Ø Firstly, multi-turn injection with fixed injection point Ø After the beam has been stored, the injection bump orbit need to be precisely tuned. By using one turn by turn BPM, with a single short mini-pulse injection beam (for single turn injection or 3 -5 turns injection if necessary), the relative injection orbit height can be precisely measured. The precise measurement of relative injection orbit height is one of the most important issue in the injection commissioning.

RCS commissioning – painting Ø The phase space painting will be performed first in one plane, and then in both plane Ø The painting beam will be extracted immediately after painting, and the painting beam distribution can be measured by using MWPM in the RTBT beam line Ø The injected beam momentum spread can be estimated by using WS at the dispersion region of LRBT Ø Debuncher parameters will be optimized according to the estimation of momentum spread and beam loss

RCS commissioning –DC mode Ø The RCS will be commissioned with DC mode and short pulse Ø The transverse secondary collimators can be used as beam dump Ø By using turn by turn BPM and BLM to track the beam, perform the storage of the first beam Ø Chicane and COD correction Ø Measure and restore the nominal tunes and linear optics Ø Measure the BPM offset by BBA Ø Measurement of beta-function and fudge factor of qudrupoles Ø Beam loss and collimation study Ø Application software commissioned with beam

RCS commissioning – AC mode Ø Ø Start with the minimum injection pulse Based on the optimized DC mode with RF cavities Do the orbit matching with AC mode Check the tracking among 5 families Q power supply and 1 family dipole power supply based on the beam Ø Measure the COD and optics parameters during the different stage of a RCS cycle by Response Matrix method Ø Optimizing the extraction parameters under AC mode Ø ……

RF cavity commissioning with beam Ø Commissioning for both DC mode and AC mode Ø Commissioning with both low beam density and high beam density Ø The lowest frequency will be set according to the measured energy of injection beam Ø Interlock with LEBT chopper and extraction kickers will be checked Ø 8 cavities will be firstly independently commissioned with beam, and then commissioned together Ø For AC mode, the voltage curve should be optimized based on the beam

RCS commissioning – extraction and RTBT Ø Extracting beam from RCS and transport the beam to the RCS dump; Ø The diagnostics will be commissioned in the RTBT line up to dump. Ø The kicker strength will be checked independently with beam, as well as the timing of kicker Ø In the beginning, BLMs in RCS and RTBT will be the tool to track the extraction procedure, and the extraction condition will be established by tuning the timing and amplitude of kickers Ø The emittance of extraction will be measured. Ø The optics of RTBT line up to dump will be corrected based on beam measurement

RTBT commissioning Ø The remain part of RTBT will be commissioned upon target condition Ø The orbit and optics will be corrected based on beam Ø The effect of octupoles will studied with low intensity beam OCT H OCT V

Discussion Possible uncertainty on commissioning schedule l In DTL, the drift tube quality have caused some delay, and the time for field measurement and tuning is tight. l The time planned for RF conditioning is sufficient or not. l The delay due to the hardware malfunction: the experience of front end commissioning…… l Unknown uncertainty

Thank you for your attention!