Injection and Extraction in the JPARC RCS Hiroyuki

Injection and Extraction in the J-PARC RCS Hiroyuki Harada J-PARC beam commissioning group “Beam Dynamics Meets Diagnostics” workshop, Nov. 4 -6 th 2015, Florence, Italy

J-PARC (JAEA & KEK) 400 Me. V H- Linac 3 Ge. V Rapid Cycling Synchrotron (RCS) Neutrino Beam Line to Kamioka (NU) 1 MW 30 Ge. V Main Ring Synchrotron (MR) Materials & Life Science Facility (MLF) JFY 2006 / 2007 JFY 2008 JFY 2009 November 6 th 2015 0. 75 MW Hadron Experimental Hall (HD) 2

Contents of this talk 1. 2. 3. 4. 5. Introduction and operational history of J-PARC 3 Ge. V RCS Injection painting study Extraction kicker field ringing compensation High intensity beam study Summary November 6 th 2015 3

Design parameters of the J-PARC RCS Pulse dipole magnet to switch the beam destination Circumference 348. 333 m Superperiodicity 3 Harmonic number 2 Number of bunches 2 Injection Charge-exchange, Multi-turn Injection energy 181 Me. V ⇒ Injection period 0. 5 ms (307 turns) Extraction energy 3 Ge. V Repetition rate 25 Hz Particles per pulse 5 e 13 ⇒ 400 Me. V in 2013 Output beam power 8. 3 e 13 in 2014 600 k. W ⇒ 1 MW Transition gamma 9. 14 Ge. V Number of dipoles 24 quadrupoles 60 (7 families) sextupoles 18 (3 families) BPMs 60 RF cavities 12 Ring Collimator November 6 th 2015 <4 k. W (< 3%) 3 Ge. V proton 400 Me. V H- MLF : Material and Life Science Experimental Facility MR : 50 -Ge. V Main Ring Synchrotron ü Recently the hardware improvement of the injector linac has been completed. ü The RCS have just got all the design hardware parameters to try the 1 -MW design beam operation. 4

Operational history of the RCS Einj=181 Me. V Imax=30 m. A Output power to MLF (k. W) Injection energy upgrade Injection peak current upgrade Einj=400 Me. V Imax=30 m. A Imax=50 m. A 1 -MW-eq beam test 1000 800 Startup of the user program in December 2008 600 400 200 0 4 k. W 120 k. W Recovery works from damages caused by the “ 3/11 -earthquake” 220 k. W 539 -k. W beam test 300 k. W 573 -k. W-eq beam test 500 k. W for users 11/ 2/1/ 5/1/ 8/1/ 11/ 2/1/ 5/1/ 8/1/ 11/ 2/1/ 5/1/ 1/2 200 200 1/2 201 201 201 1/2 201 201 1/2 201 008 9 9 9 009 0 010 1 1 1 011 2 2 2 012 3 3 3 013 4 4 4 014 5 5 ü Startup of the RCS beam commissioning in October 2007 ü The beam power ramp-up of RCS has steadily proceeded following; - Progression in beam tuning, beam dynamics numerical simulation, hardware improvements ü High intensity beam tests of up to 573 k. W for both injection energies of 181 Me. V and 400 Me. V ü 1 -MW beam tests from October 2014 ü Successful achievement of 1 -MW eq. intensity output on January 2015 ü Present output beam power for the routine user program : 500 k. W November 6 th 2015 5

Fast Extraction B (T) s 20 m eler a 0. 93 0. 28 * Multi-turn H- stripping injection (0. 5 ms~307 turns). * Acceleration in rapid cycling (25 Hz). * Fast extraction. tion 1. 13 Acc Magnetic field of Bending RCS injection process and acceleration cycle Injection 0 20 600 ns 40 Time (ms) 0. 5 ms (307 turns) Intermediate Multi-turn HPulses 456 ns Fast extraction by kicker Dp/p 0 h=2 B field f stripping injection. . . 1 st bunch November 6 th 2015 814 ns ~200 ns Time (ms) 2 nd bunch 6

RCS Injection System H- x ISEP 1, 2 QFL MWPM 3 3 rd foil 2 nd foil QDL MWPM 4 MWPM 5 m H+ To a be H- Beginning s of painting H 0 HH 0 PB 1, 2 1 st foil Circulating SB 1 SB 2 End of painting <Injection scheme> Ø Chopped beam Ø H－charge exchange Ø 307 multi-turns (400 Me. V) PB 3, 4 H+ beam November 6 th 2015 p m du SB 3 - depress beam density - decrease foil scattering SB 4 “Injection painting” 7

Horizontal Injection Painting Process H- QFL MWPM 3 3 rd foil 2 nd foil QDL MWPM 4 1 st foil x MWPM 5 ISEP 1, 2 H- s H+ e b o T PB 3, 4 Circulating beam SB 1 SB 2 SB 3 SB 4 foil 0 d H 0 PB 1, 2 x’[mrad] am p um 93 124. 1 current SB x[mm] PB -4. 4 Injection Beam November 6 th 2015 Injection period(500μsec) time 8

Horizontal Injection Painting Process H- QFL MWPM 3 3 rd foil 2 nd foil QDL MWPM 4 1 st foil x MWPM 5 ISEP 1, 2 H- s H+ am e b o T PB 3, 4 Circulating beam SB 1 SB 2 Ring orbit 0 d H 0 PB 1, 2 x’[mrad] p um 93 124. 1 SB 3 SB 4 foil current SB x[mm] PB -4. 4 November 6 th 2015 Injection Beam Injection period(500μsec) time 9

Horizontal Injection Painting Process H- QFL MWPM 3 3 rd foil 2 nd foil QDL MWPM 4 1 st foil x MWPM 5 ISEP 1, 2 H- s H+ am e b o T PB 3, 4 Circulating beam SB 1 x’[mrad] SB 2 SB 3 SB 4 foil 0 November 6 th 2015 d H 0 PB 1, 2 -4. 4 p um 93 Ring orbit Pa int ing 124. 1 current SB x[mm] PB Are Injection Beam a Injection period(500μsec) time 10

Vertical Injection Painting Process y‘ foil y s MWPM 3 VPB 1 VPB 2 MWPM 4 MWPM 5 y H+ HNovember 6 th 2015 1 st foil 11

Longitudinal injection painting F. Tamura et al, PRST-AB 12, 041001 (2009). M. Yamamoto et al, NIM. , Sect. A 621, 15 (2010). Momentum offset injection RF voltage pattern RF voltage (k. V) V 1 Fundamental rf V 2 Second harmonic rf Time (ms) Dp/p=0, -0. 1 and -0. 2% Uniform bunch distribution is formed through emittance dilution by the large synchrotron motion excited by momentum offset. November 6 th 2015 V 2/V 1=80% The second harmonic rf fills the role in shaping flatter and wider rf bucket potential, leading to better longitudinal motion to make a flatter bunch distribution. 7/23 12

Longitudinal injection painting Additional control in longitudinal painting ; phase sweep of V 2 during injection Vrf=V 1 sinf-V 2 sin{2(f-fs)+f 2} RF potential well (Arb. ) V 2/V 1=0 V 2/V 1=80% (A) f 2=-100 deg (B) f 2=-50 deg (C) f 2=0 f 2=-100⇒ 0 deg The second harmonic phase sweep method enables further bunch distribution control through a dynamical change of the rf bucket potential during injection. f (Degrees) November 6 th 2015 8/23 13

RCS fast extraction system to MLF / MR to MLF to MR RCS RCS 3 DC septum magnets Beam transport line 8 kicker magnets to MLF RCS November 6 th 2015 to M R 14

Contents of this talk 1. 2. 3. 4. 5. Introduction and operational history of J-PARC 3 Ge. V RCS Injection painting study Extraction kicker field ringing compensation High intensity beam study Summary November 6 th 2015 15

Injection error and betatron oscillation 20 μsec Vertical plane Injection 20 μsec Horizontal plane Mountain view of Ionization profile monitors in the ring (Injection to first 10 turns) November 6 th 2015 16

Horizontal and vertical painting injection process 500 ms Single pulse injection 500 ms PB VPB time Horizontal phase space 100π November 6 th 2015 Vertical phase space 100π 17

Recent measurement method of painting injection process Multi-turn injection just before PB decay 500 ms (x, x’) (y, y’) x‘ (mrad) time y‘ (mrad) PB Take BPM data Measured DX (PBON – OFF) Calculated orbit T=250 ms y (mm) T=500 ms x[mm] T=0 ms x (mm) November 6 th 2015 s[m] 18

Switching transverse painting area pulse-by-pulse between MLF and MR The RCS are required different beam emittance from the MLF and MR. So, RCS is operating with switching transverse painting between MLF and MR pulse-by-pulse. Horizontal Paint bump patterns Inj. start 500 msec 50 p Inj. end 150 p Foil edge 100 p 50 p 100 p 150 p Foil edge Inj. beam 150 p for MLF 100 p for MR 50 p for MR Calculation November 6 th 2015 19

Contents of this talk 1. 2. 3. 4. 5. Introduction and operational history of J-PARC 3 Ge. V RCS Injection painting study Extraction kicker field ringing compensation High intensity beam study Summary November 6 th 2015 20

RCS kicker configuration (1) Kicker Magnet Numbers 8 (S: 3, M: 2, L 3) Configuration Twin-C distributed magnet Dimension Aperture size Schematic diagram of kicker system Vertical 960 mm Horizontal 776 mm Length 638 mm Vertical 186 mm (S), 206 mm (M), 232 mm (L) Horizontal 360 mm Length 638 mm Magnet core Ferrite [PE 14, TDK ltd] Unit number 20 units/magnet Characteristic impedance 10 W

RCS kicker configuration (2) Configuration of the one unit of kicker magnet

Field measurement and Ringing B A D D Field calculation of kicker magnetic field [A. U] Measured field of kicker magnet time [sec] November 6 th 2015 23

Extraction beam quality 600 nsec 1. Different beam positions between 1 st and 2 nd bunches by the field ringing - Non-flatness of beam profile @ Neutron targets with octupole field - Emittance growth by injection error @ MR injection points 2 1 400 nsec 800 nsec Kicker field For ringing cancellation simulation results w/o offset at oct. 2 w/ offset of 2 mm at oct. 2 1 2 400 nsec 800 nsec x[mm]@target 2. Beam fluctuation in 1 st bunch by the ringing - Emittance growth - Beam instability source November 6 th 2015 kicker(1, 3, 5, 7) Dt = -120 nsec kicker(2, 4, 6, 8) Dt = 0 nsec 24

Beam displacement measurement caused by kicker field ringing Measured Dx[mm] Beam condition : shorter single bunched beam (~150 → ~30 nsec) Monitor : Beam Position Monitor (BPM) @ extraction line Knob : Fire timing (Dt) of all kickers Kicker field +3. 3 mm -5. 5 mm Dt [nsec] Beam center positions of both 1 st and 2 nd bunches are ~0 mm. Beam fluctuation of 1 st bunch is from -5. 5 (-1. 6%) to +3. 3 mm(+0. 75%). November 6 th 2015 Time structure of the ringing is not simple! 25

Timing scan kicker-by-kicker were performed for understanding each ringing. After that, we tried to optimize each kicker timing based on scan data for the ringing compensation. KM 1 KM 2 KM 3 KM 4 KM 5 KM 6 KM 7 KM 8 Dt [nsec] November 6 th 2015 26

ID ① ΔT ② ΔT ① KM 1 0 nsec 10 nsec Measured Dx[mm] Comparison between all and each kicker timing scan KM 2 0 nsec KM 3 0 nsec KM 4 0 nsec 35 nsec KM 5 0 nsec KM 6 0 nsec KM 7 0 nsec 10 nsec KM 8 0 nsec -10 nsec : Summed positions for each scan : Measured position for all scan Measured Dx[mm] ② November 6 th 2015 Summed scan position for each KMs ( ) is a good agreement with measured position for all KM timing ( ). ) ⇒ We can discuss with kicker ringing compensation by using each scan data. timing ΔT [nsec] 27

Timing optimization for ringing compensation : Sum positions for each scan : Measured position for all scan Measured Dx[mm] ① ③ ID ① ΔT ③ ΔT Measured Dx[mm] Search of optimized timing were performed by using each scan data. KM 1 0 ns 60 ns KM 2 0 ns -20 ns KM 3 0 ns 50 ns KM 4 0 ns 30 ns KM 5 0 ns 200 ns KM 6 0 ns -30 ns KM 7 0 ns 50 ns KM 8 0 ns -40 ns November 6 th 2015 timing ΔT [nsec] 28

: Sum positions for each scan w/o compensation Max ： Δ= 10. mm (＋2. 33%) Min ： Δ= -14. mm (－3. 26%) w/ old compensation until 2013 Max ： Δ= 3. 2 mm (＋0. 75%) Min ： Δ= -5. 5 mm (－1. 38%) w/ new compensation on 2014 Max ： Δ= 0. 6 mm (＋0. 15%) Min ： Δ= -1. 1 mm (－0. 28%) November 6 th 2015 timing ΔT [nsec] 29

Extracted beam profile 2 nd bunch intensity [A. U] 1 st bunch intensity [A. U] Measured beam profile by MWPM in extraction line sx=9. 6 sx=8. 5 sx=8. 2 sy=8. 2 x[mm]

Online monitor and drift correction system for kicker timing There is a gradual change in Thyratron condition and Thyratron output timing has a drift over a period of minutes. Online monitor of Thyratron output November 6 th 2015 KM 01 KM 05 KM 02 KM 06 KM 03 KM 07 KM 04 KM 08 Thyratron outputs of kickers are monitored online. If difference from reference is more than 10 nsec, kicker timing is corrected automatically. Extraction beam stability is kept by this system. 31

Contents of this talk 1. 2. 3. 4. 5. Introduction and operational history of J-PARC 3 Ge. V RCS Injection painting study Extraction kicker field ringing compensation High intensity beam study Summary November 6 th 2015 32

Longitudinal injection painting Longitudinal beam distribution just after beam injection (at 0. 5 ms) f (degrees) Density (Arb. ) f (degrees) V 2/V 1=80% f 2=-100 to 0 deg Dp/p=-0. 2% Dp/p (%) Density (Arb. ) f (degrees) Bf ~0. 15 V 2/V 1=80% f 2=-100 to 0 deg Dp/p=-0. 1% V 2/V 1=80% f 2=-100 to 0 deg Dp/p= 0. 0% No longitudinal painting f (degrees) Bf >0. 40 f (degrees) Measurements (WCM) Numerical simulations Jun 8 th 2015 from H. Hotchi et. al. , PRST-AB 15, 040402 (2011). 9/23 33

Measurement vs Simulation (Inj. Energy = 181 Me. V) : bunching factor from injection to extraction Bunching factor ― Simulations 539 k. W (500 ms) 433 k. W (400 ms) 326 k. W (300 ms) 217 k. W (200 ms) Time structure of measured bunching factor for each intense is in good agreement with simulated results. Feed Forward of RF cavities is worked well up to 600 k. W. Time (ms) 104 k. W (100 ms) F. Tamura H. Hotchi Jun 8 th 2015 Time (ms) 34

Measurement vs Simulation (Inj. Energy = 181 Me. V) : extraction beam profile at 3 Ge. V MWPM @ extraction beam line Vertical Horizontal ― Simulations 433 k. W (400 ms) 326 k. W (300 ms) 217 k. W (200 ms) 104 k. W (100 ms) Jun 8 th 2015 Intensity dependence of RMS beam width ● Measurements ○ Simulations RMS width (mm) Charge density (Arb. ) 539 k. W (500 ms) Vertical Horizontal H. Hotchi Li pulse length (ms) Position (mm) H. Hotchi Our numerical simulation well globally reproduced the experimental results up to 540 k. W intensity beam. 35

Painting parameter dependence of beam survival rate for 550 k. W-eq. intensity Einj=181 Me. V, 539 k. W-eq. intensity (Nov. 2012) ○ Einj=400 Me. V, 553 k. W-eq. intensity (Apr. 2014) Beam survival rate By adding 100 p transverse painting By longitudinal painting Beam intensity (x 1013) ○ H. Hotchi No painting Further space-charge mitigation by higher injection energy DCCT data Einj=400 Me. V Einj=181 Me. V Beam loss : ~30% ⇒ <1% Time (ms) Expanded view Painting parameter ID Jun 8 th 2015 This experimental data clearly show ü the big gain from the injection energy upgrade ü the excellent ability of “injection painting”. 36

Achievement of 1 MW-eq. intensity beam acceleration BLM signal (arb. ) Scintillation-type BLM @ Collimator ü Mainly from foil scattering during injection ー ー 1014 k. W-eq. : 8. 45 x 1013 870 k. W-eq. : 7. 25 x 1013 731 k. W-eq. : 6. 09 x 1013 606 k. W-eq. : 5. 05 x 1013 Time (ms) BLM signal (arb. ) Scintillation-type BLM @ high-dispersion in Arc 1 MW Run#60 (Jan, 2015) H. Hotchi Time (ms) ü Beam loss by a space charge effect is well minimized, only from foil scattering. ü Integrated beam losses (<0. 2%) increase linearly with beam intensity. ü No observation of beam loss by upgrade of RF power supplies and FF tuning. ü Further loss reduction from foil scattering

Number of foil hits Beam loss reduction by foil scattering 41. 5 Jan. 2015 For beam loss reduction by foil scattering, • Optimization of foil position and size • Larger painting area H. Hotchi 27. 8 19. 2 14. 2 ID 1: 100 p(H)-100 p(V), Width=30 mm, Dx=13 mm ID 2: 100 p(H)-100 p(V), Width=30 mm, Dx=9 mm ID 3: 150 p(H)-100 p(V), Width=30 mm, Dx=9 mm ID 4: 150 p(H)-100 p(V), Width=20 mm, Dx=9 mm ID 5: 150 p(H)-150 p(V), Width=20 mm, Dx=9 mm ID 6: 200 p(H)-100 p(V), Width=20 mm, Dx=9 mm Oct. 2015 11. 6 10. 7 Parameter ID y ID 1 x November 6 th 2015 Injection beam Circulating beam Dx W 100 p(H&V) y 1 st foil ID 5 x Injection beam Circulating beam Dx W 150 p(H&V) 1 st foil 38

Summary • Injection painting are well-controlled for mitigation of space charge force and reduction of foil-hitting provability. • Extraction beam deviation caused by kicker’s field ringing was corrected well by timing optimization. • Beam loss except foil scattering was minimized well up to 1 MW-eq. beam acceleration. • Foil scattering beam loss tries to be reduced by larger injection painting. • The beam power for user program will be increased to 1 MW in the near future. November 6 th 2015 39