Status of 3GeV- RCS in J-PARC Michikazu Kinsho （ J-PARC, JAEA ） Contents 1. Introduction : J-PARC RCS, brief history 2. Issues for high power operation � Reduction of beam losses � High beam quality 3. Availability of the beam operation 4. Power up scenario 5. Summary 1 FFAG10 Oct. 28-31
Linac J-PARC [181 MeV at present, (JAEA & KEK) 400 MeV with ACS] 3 GeV Rapid Cycling Neutrino Beam Line Synchrotron (RCS) to Kamioka 50 GeV Main Ring Materials & Synchrotron (MR) [30 GeV in 1 st phase] Life Science Facility (MLF) JFY 2006 / 2007 JFY 2008 Hadron JFY 2009 Experimental Hall 2
3 J-PARC today In operation
Brief history 2007 � 04/Oct. : Beam commissioning was started. � 31/Oct. : Successfully accelerated to the designed beam energy of 3GeV � 23/Dec. : The official permission was obtained from the authority for the radiation safety. 2008 � 13/May. : Startup of the beam delivery for the MLF and the MR for their beam commissioning. � 18/Sep. : 210 kW (1.77 x10 13 ppp ) was demonstrated for 70 seconds. � 23/Dec. : Startup of MLF-user operation with a beam power of 20 kW. and also Startup of 25-Hz switching beam operation for the MLF and the MR 2009 � Nov. : 120kW power user operation for the MLF was started � 10/Dec. : 300 kW (2.53x10 13 ppp ) output operation for 1 hour to the MLF target 4
History of the output beam pow er to MLF Accumulated Beam power (MWh) 120 kW Nov. 2009 Beam power (kWh/day) Startup of MLF user runs Dec. 2008 4 kW 20 kW ・ Due to the discharge problem of the RFQ, the RCS beam power was limited to 20 kW for a long period. ・ By the vacuum improvement of the RFQ section, the performance of the RFQ was recovered. ・ Then the RCS beam power was increased to 120 kW 5 and its operation has been continued up to now.
What is 3GeV-RCS in J-PARC The beams are extracted Design parameters by kicker magnets and DC septum magnets at the The H0 dump is used to dump Circumference 348.333 m extraction section and unstripped beams at the stripping then transported either to foil. The capacity is 4kW. Superperiodicity 3 MLF or to MR with a Harmonic number 2 pulsed bending magnet The stripping foil placed in the 3NBT line. No of bunch 2 in the injection H0 Dump section is used to (4 kW) Injection energy 181 MeV 1 st arc convert H- beam (400 MeV ) section from the linac into Beam Extraction energy 3 GeV protons. Extraction Collimator section from Repetition rate 25 Hz Foil LINAC to Particles per pulse 2.5e13 - 5e13 Injection RCS has a three-fold MR&MLF (8.3e13 with 1 MW) symmetric lattice section whose circumference 3 rd arc Output beam 0.3 - 0.6 MW is 348.3m. power 2 nd arc (1 MW) section sectio Transition gamma 9.14 GeV RF section n Number of dipoles 24 quadrupoles 60 (7 families) One of the three-fold symmetric sextupoles 18 (3 families) lattice comprises two arc Each arc module has steerings 52 modules and a long straight a missing-bend cell. insertion. 6 RF cavities 12 (11 at present)
Issues for high pow er operation � Reduction of beam losses � Activation � After 2 weeks user operation with 120kW. � Maximum value of activation on surface of the component was about 1.5 mSv/h. This value was not so high but not low. � Reduction of beam loss is essential to realize a higher power operation. � After 1 hour-300kW operation � An outstanding increasing of activation was not found with 300kW operation for 1 hour. � Beam quality � Satisfies the requirements as a high power injector to the MR as well as a high power beam source to the MLF.
Typical residual radiation level in RCS (A) Collimator (B) Injection area section Residual radiation level after beam shutdown - 5-hour after 120 kW operation (June 2010) 100, 8 1200, 60 Red: measured on the chamber surface 65, 9 Blue: measured at a distance of 30 cm Unit: μ Sv/h 30, 5 32, 9.0 10, 1.5 15, 0.5 1700, 140 50, 12 14, 2.0 10, 1.0 8.0, 3.0 20, 2.5 50, 2 40, 8.0 13, 1.0 (A) Collimator section 260, 23 520, 100 (B) Injection area 500, 90 Charge- 20, 1.5 exchange 200 5.0, 1.0 foil 20, 3 20 13, 2.0 120, 20 � Residual radiation downstream of the 1 st foil in the injection section 8 � Residual radiation at the arc section with dispersion maximum
Beam loss in the injection section To H0 dump Ring Collimator QFM H0 ‐ Q H0 ‐ Septum2 Circulating 3 rd foil H0 ‐ Septum1 2 nd foil beam PBH4 QDL (2) BPM2 ‐ 1 PBH3 (1) H0 dump branch H − injection SB4 SB3 beam QFL SB2 -- Two uncontrolled hot points near the RCS injection area 1 st Foil SB1 (1) H0 dump branch, (2) Near QFM (BPM2-1) (mostly at the ring side and only in the horizontal direction) g n i t a l u c m r i � Caused by the large angle C a e b multiple Coulomb scattering at the foil ! 9
Acceptance simulation To identify the loss sources, a detail experimental study as well as simulation were carriedout, where the real experimental condition, a comparatively large number of macro particle as well as a very realistic and precise machine aperture were taken into account. � As a result, a very realistic distribution of the beam loss peaking exactly at (1) and (2) and consistent with the beam loss monitor signal were obtained. Geant + SAD w/ 10 8 macro particles Horizontal Two hot points only in the horizontal direction at the H0 branch and BPM +30mrad locations are identified. Δ x(mm) QFL QDL x 1 st Foil -30mrad Shift bump orbit ISEP1, Painting 100 π 2 Painting 200 π S FOIL H0 BPM PBH1,2 SB3SB4 PBH3,4 PBH SB1 SB2 QDL PBH QFM branch 3 Vertical 4 Orbit moves towards outer side w/ larger painting area � Loss reduced in the inner side! Δ y(mm) No noticeable loss as well as residual activation in the vertical direction � the vertically focusing quadrupole QDL as 10 confirmed in the simulation.
Comparison of beam loss betw een simulation and experiment Figures show a comparison of the measured beam loss rate to that with the simulation. The beam loss monitor gain for each mode was adjusted and was different in order to measure even a lower beam loss for the former mode or the signal not to saturate in case of much higher beam loss for the later mode. The experiment was done for three different painting areas of 100 π , 150 π and 200 π mm mrad in the horizontal direction. The loss particles found in the simulation and integrated beam loss monitor signal for each case were normalized by the data with a painting area of 150 π mm mrad. The trend of the beam loss rates were found to be consistent each other and were proportional to the foil hitting rate. (1) H0 branch (ring side) (2) Near QFM (ring side) 1/3mode(simulation) 1/3mode(measurement) 1/3mode(simulation) 1/3mode(measurement) DCmode(simulation) DCmode(measurement) DCmode(simulation) Dcmode(measurement) 1.6 1.6 1.4 1.4 Consistent! Consistent! 1.2 1.2 1 1 r a t e r a t e 0.8 0.8 0.6 0.6 1/3 mode: foil hit =1 0.4 DC mode w/ paint 150 π : foil hit =9 0.4 BLM gain was different 0.2 0.2 Bigger painting area � Lower foil hit for 1/3 and DC mode 0 0 80 100 120 140 160 180 200 220 80 100 120 140 160 180 200 220 11 Painting area ( π mm mrad) paint Painting area ( π mm mrad) paint
Solutions To reduce such a uncontrolled beam losses, two actions are in consideration. � The first one is to use a smaller size foil and is very simple to adopt. It will directly reduce such a beam loss as the foil hitting particles will be reduced. The present foil size especially in the vertical direction is quite big (40 mm) and already replaced with a size of 15 mm. 1. Optimized foil size � reduce foil hit rate ~ 1/2 BLM signal (int.) However, there is no change in the horizontal direction as foil @H0 branch 120 kW operation position is adjustable very precisely and also circulating beam orbit goes away from the foil with decay patterns of the horizontal #hits painting bump magnets. ~8.8 #hits The foil hitting rate are expected to reduced about a half and thus the corresponding beam losses as well. ~4.7 Current operation - Current foil size : Δ x=7 mm - Next foil size : Δ y=10 mm BLM signal (int.) @QFM entrance small 110 (H) × 15 (V) mm 2 Linac beam ~7x7 mm 2 110 (H) × 40 (V) mm 2 foil Already installed and checked this run!! � Beam loss became 1/2 � Not sufficient !! Residual radiation with 300 kW operation might left Average number of foil hits about 1.5 mSv/h ! (simulated value) � 2nd action is to place a new collimator system at the H0 branch location (1st loss point) in order to localize 12 those uncontrolled beam losses and will be installed in the 2011 maintenance period.
Example of localization 2. Local shield ≈ Collimator is in consideration! � Simulation shows that can localize the beam losses. To be installed in 2011 maintenance period! outer inner w/ collimator Collimat or 13 H0 BPM2 ‐ 1 FOIL QDL PBH3.4 QFM branch
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