J-PARC 3GeV RCSにおける ビーム調整 ～入射部におけるビームロス起源の同定 原田寛之 原子力機構/J-PARCセンター ビーム物理研究会2010＠理研 2010年11月12日 Linac [181 MeV at present, 400 MeV with ACS] J-PARC (JAEA & KEK) 3 GeV Rapid Cycling Synchrotron (RCS) Neutrino Beam Line to Kamioka Materials & Life Science Facility (MLF) 50 GeV Main Ring Synchrotron (MR) [30 GeV in 1st phase] Hadron Experimental Hall Design parameters of RCS Circumference 348.333 m Super periodicity 3 Harmonic number 2 No. of bunch 2 Injection energy 181 MeV (400 MeV with ACS) Extraction energy 3 GeV Repetition rate 25 Hz Particles per pulse 2.5e13 - 5e13 (8.3e13 for 1 MW) Output beam power 0.3 - 0.6 MW (1 MW for upgraded Linac) Transition gamma 9.14 GeV Number of dipoles 24 quadrupoles 60 (7 families) sextupoles 18 (3 families) steerings RF cavities 52 12 (11 at present) Start of the beam commissioning : October 2007~ RCS Injection System H- QFL 3rd foil 2nd foil QDL MWPM3 MWPM5 MWPM4 x H+ ISEP1,2 HH0 s HH0 PB1,2 PB3,4 1st foil Circulating beam SB1 SB2 SB3 SB4 4 Horizontal Painting Injection Process H- QFL MWPM3 3rd foil 2nd foil QDL MWPM4 1st foil x MWPM5 H+ ISEP1,2 H- s H0 PB1,2 PB3,4 Circulating beam x’[mrad] Circulating beam H- SB1 SB2 SB3 SB4 current 0 93 124.1 SB x[mm] PB -4.4 Injection Beam 5 Injection period(500μsec) time Horizontal Painting Injection Process H- QFL MWPM3 3rd foil 2nd foil QDL MWPM4 1st foil x MWPM5 H+ ISEP1,2 H- s H0 PB1,2 PB3,4 Circulating beam Circulating beam x’[mrad] H- SB1 SB2 SB3 SB4 current 0 93 124.1 SB x[mm] PB -4.4 Injection Beam 6 Injection period(500μsec) time Horizontal Painting Injection Process H- QFL MWPM3 3rd foil 2nd foil QDL MWPM4 1st foil x MWPM5 H+ ISEP1,2 H- s H0 PB1,2 PB3,4Circulating beam Circulating beam x’[mrad] H- SB1 SB2 SB3 SB4 current 0 93 124.1 SB x[mm] PB -4.4 Injection Beam 7 Injection period(500μsec) time Vertical Painting Injection process y‘ y s MWPM3 MWPM4 MWPM5 VPB1 VPB2 y H+ H1st foil 8 Issue of beam loss @ injection section • Radioactivity at Horizontal plane of HO branch and BPM – ~200μSv/h@20kW operation – ~1-2mSv/h@120kW operation • Radioactivity at Vertical plane of them – ~ several 10μSv/h • No change of loss monitor signal for open/close of ring collimator • Ratio of loss signal between 1pass and circulating mode @ 20kW operation is 17 →equals to calculation value of averaging foil hit counts →Must identify the source of beam loss at high radioactivity points Issue of beam loss @ RCS Injection section Ring Collimator (1) HO branch ~200μSv/h@20kW operation ~1.2mSv/h@120kW operation H0-Septum2 H0-Q H0-Septum1 QDL (2) (1) BPM QFL Foil (2) BPM BPM ~200μSv/h@20kW operation ~2mSv/h@120kW operation Foil Scattering Distribution Multiple Coulomb scattering Multiple Coulomb scattering Nuclear scattering** (p, p), (p, n) . . . . Nuclear scattering Coulomb & nuclear scattering Coulomb & nuclear scattering rad foil rad By H. Hotchi Scattering angle calculation of 106 events by GEANT simulator（Foil : 300μg/cm2） →Loss particles at H0 branch are 1 or 2 events from particle tracking simulation →Full simulation with beam core should be avoided in the view point of simulation time and increasing statics Scattering angle calculation of 108 events by GEANT simulator (Foil : 300μg/cm 2） →Select about 104 events of large scattering more than ±3mrad Horizontal Phase Space @ 150π Painting Process 1 turn 30 turn Foil Foil Length between Injection beam position and Foil edge→12mm Painting injection only for horizontal direction 10 turn 40 turn 57 turn Foil Foil 20 turn 50 turn Foil Foil Foil Particles w/ foil hit Particles w/o foil hit Particle Tracking (1turn) @150π 3mrad -3mrad Total = 2069 Total = 1144 FOIL QDL H0 branch PBH3 PBH4 BPM QFM Particle Tracking (57turn) @150π 3mrad -3mrad Total = 2293 Total = 1080 FOIL QDL H0 branch PBH3 PBH4 BPM QFM Estimation of residual radioactivity @150πpaint for horizontal FOIL QDL PBH3 PBH4 BPM QFM Total = 1926 Total = 1115 Assumption : 1W/m = 1mSv/h 1.2kW(47×108) 220144counts (1.59m) 109034counts (0.1m) 105899counts (1.36m) 278μSv/h 35μSv/h 20μSv/h 161141counts (0.2m) 206μSv/h Estimation of residual radioactivity @150πpaint for vertical Total = 310 23@1turn → 18766@circulating Total = 319 18766events(0.1m)→48μSv/h FOIL QDL H0 branch PBH3 PBH4 BPM QFM Solution of this issue(1) 40mm 15mm Current Foil Size (110mm x 40mm) – Average Hit Count @ foil = 8.77 New Foil Size (110mm x 15mm) – Average Hit Count @ foil = 4.66 1 turn x’[rad] Particles w/ foil hit 20 turn y[m] Particles w/o foil hit x[m] y’[rad] 40 turn 60 turn 80 turn 94 turn 1 turn x’[rad] Particles w/ foil hit 20 turn y[m] Particles w/o foil hit x[m] y’[rad] 40 turn 60 turn 80 turn 94 turn Solution of this issue(2) H0-Septum1 Install the new collimator and shield at H0 branch duct for localization of this beam loss H0 branch duct QDL Example of localization Total = 1965 Total = 1096 FOIL H0 branch BPM Example of localization Collimator Total = 1965 Total = 1306 FOIL H0 branch BPM Summary • The source of beam loss for injection section is identified as the rare events of large-scattering by the foil hits. • As the solution of this issue, foil size is smaller and beam loss is localized at new collimator system. Decay Curve of redial radioactivity 1/3mode、ACmode(Foil:260μg/cm2) 1/3mode, 560nsec, 1bunch 0.255 1/3mode, 280nsec, 2bunch 0.267 ACmode, 280nsec, 2bunch 4.372 (~17 times) By K.Satou & H. Harada Estimation of Loss Particle 1ターンで入射された粒子数を108として考える。周回ごとに粒子数は増加し、100μs 入射では47ターン入射されるので、トータルの粒子数は47× 108である。 現在、フォイルに当たった粒子を108として大角度のイベント104を飛ばしているため、 各ターンごとに規格化してやる必要がある。 規格化したロス数 = トラッキングでのロス数 × ( ヒットした数 ÷ 全体数 ) × 入射数 (例) 1ターン目 100 = 100 × ( 30000 ÷ 30000 ) × 1 = 100 × ( 30000 ÷ 30000 ) × 2 = 100 × ( 15000 ÷ 30000 ) × 20 = 100 × ( 10000 ÷ 30000 ) × 47 (例) 2ターン目 200 (例) 20ターン目 1000 (例) 57ターン目 1566 Estimation of Loss Particle ペイン ト軌道 平均 ロス数 ヒット数 (1/3) @分岐部 ロス数 (周回) @分岐部 比率 ロス数 ロス数 （1/3vs周回） (1/3) (周回) @BPM @BPM @分岐部 比率 (1/3対周回) @BPM 100π 22.9 7050 158924 22.5 10058 224060 22.3 150π 17.4 6439 109034 16.9 9635 161141 16.7 200π 14.2 5828 80559 12.9 9494 122879 12.9 47×108粒子に対するロス粒子数（入射パルス回数：47回、周回数：57回） 第2章6節 大電流ビームの空間電荷効果 ビーム出力100kW時、 Simpsonsのシュミ レーションによるベータトロン振動数の広がり ビームの空間電荷力によって発散力 を生じ、粒子は電磁石による外部収束 力を弱く感じる。 (6.40, 6.42) Δν ～ －0.4 ベータトロン振動数の広がりを生じる。 νy = 6 共鳴線に抵触し、大きなビームロスを 生じる。 νx = 6 垂直方向のベータトロン振動数 νy ビーム出力を増強する。 Laslettのチューンスプレッドの nt rp 1 式 水平方向のベータトロン振動数 νx １次共鳴線 ２次共鳴線 2 2 3 B f nt ：全電流、Bf:バンチングファクター rp ：陽子の古典半径、ε：エミッタンス β,γ：ローレンツファクター 27 第2章6節 空間電荷力の緩和 ～ペインティング入射 x‘ 入射ビーム x 入射軌道や周回軌道を時間的に変 化させつつ、ビーム入射を行い、実 空間上に一様にビームを広がらせる。 入射ビーム 電荷密度を小さくし、空間電荷力を緩 和させる。 y‘ ペインティング入射 入射ビーム Δν ～ －0.4 → －0.1 y 入射ビーム / ε: 周回ビームエミッタンス、β,γ: リングのTwiss parameter 28 Correction of Ring Optics Tune measured:(6.68, 6.25), Tune set:(6.64, 6.25) Dispersions estimated by looking at a rf-frequency dependence of the closed orbit Beta estimated from a response of the closed orbit for a dipole kick (STM) Curves：Design value, Dots：Measured values, Solids：Reconstructed value ηx, ηy[m] βx, βy[m] 1/3 ring (straight＋arc) s[m] We could makeoptics the optics to thewas design curves well The measured (tune,almost beta, fitted dispersion) reasonably 29 with no iteration. reconstructed in our accelerator model. Control of Ring Optics (νx,νy)=(6.38,6.45) on 2008/05/26 (νx,νy)=(6.40,6.42) on 2009/11/02 We can easily control the ring optics (betatron tunes and beta amplitude functions) with good accuracy!! Measurement of Response Matrix for frequency domain and Identification of Injection Phase Space xn x0 cos2n x x sin2n x x0' x sin2n x x0 : injection position, x0’ : injection derivative, νx: betatron tune, αx, βx: twiss parameter @ beam monitor, n : number of turns Fourier Transform Obtain the real and imaginary part of betatron oscillation component, which have outputs by a response matrix for injection position and derivative ReX x x0 ImX R x x ' x 0 A12 x0 A 11 x' A A 22 0 21 x A 0' 11 x0 A21 A12 ReX x A22 ImX x 1 31 Measurement of response matrix ReX x ImX x Re X x A11 ImX A x 21 A12 x 0 A22 x 0' A11 A12 A21 A22 x 0 x0 ' 32 Correction of the injection mismatching Injection beam Closed orbit Injection bump x at the 1st foil of injection & closed orbits : adjusted by the shift bump magnet x'at the 1st foil of the injection orbit : adjusted by the injection septum magnets Mountain plot of the beam profile measured by IPM for 1-intermediate pulse injection Horizontal profile Corrected !! Adjusted so as to minimize the betatron oscillation Correction of the injection mismatching (y,y’) at the 1st foil of the injection orbit: adjusted by injection steering magnets Mountain plot of the beam profile measured by IPM for 1-intermediate pulse injection Vertical profile Corrected !! Adjusted so as to minimize the betatron oscillation Footprint of (x, x’) over the painting injection process Single-short pulse injection (25 mA peak, 560 ns long) 600ms SB PBH 500ms t5 X’(rad) t0 ○ 1-pass BPM 1101-1102 △ PB magnet off at t5 □ MWPM3-4 t0 100 ⇒~110 t5 150 ⇒~163 X(m) 200 ⇒~220 Footprint of (y, y’) over the painting injection process Single-short pulse injection (25 mA peak , 560 ns long) ○ 1-pass BPM 1101-1102 □ MWPM3-4 600ms SB 500ms t0 Y’(rad) PBV t5 (Correlate painting) 100 Y(m) Acceptance Simulation 30mrad -30mrad FOIL QDL H0 branch PBH3 PBH4 BPM QFM Result of Acceptance Simulation Foil Edge Loss up to branch 7mm ±30mrad Loss up to BPM Survive through the Collimator Loss at BPM Loss up to BPM Loss up to branch Acceptance Simulation for vertical 30mrad -30mrad FOIL QDL H0 branch PBH3 PBH4 BPM QFM 100π paint injection orbit x QFL QDL 1st Foil ISEP1,2 (100pi paint bump orbit ) (shift bump orbit) PB1,2 PB3,4 S SB1 SB2 SB3 SB4 150π paint injection orbit x QFL QDL 1st Foil ISEP1,2 (150pi paint bump orbit ) (shift bump orbit) PB1,2 PB3,4 S SB1 SB2 SB3 SB4 200π paint injection orbit x QFL QDL 1st Foil ISEP1,2 (200pi paint bump orbit ) (shift bump orbit) PB1,2 PB3,4 S SB1 SB2 SB3 SB4 Loss Monitor signal of H0 branch @single pass mode Loss Monitor signal by K. Yamamoto Integral Values 100πpaint 150πpaint 200πpaint decrease Loss Monitor signal of H0 branch @circulating mode Loss Monitor signal by K. Yamamoto 100πpaint 150πpaint 200πpaint decrease Loss Monitor signal of BPM @single pass mode Loss Monitor signal by K. Yamamoto 100πpaint 150πpaint 200πpaint constant Loss Monitor signal of BPM @circulating mode Loss Monitor signal by K. Yamamoto 100πpaint 150πpaint 200πpaint decrease Comparison of beam loss between simulation and experiment at ring inside of H0 branch rate 1/3mode(simulation) DCmode(simulation) 1/3mode(measurement) DCmode(measurement) 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 80 100 120 140 160 paint 180 200 220 Comparison of beam loss between simulation and experiment at ring inside of BPM rate 1/3mode(simulation) DCmode(simulation) 1/3mode(measurement) Dcmode(measurement) 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 80 100 120 140 160 paint 180 200 220
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