1. Primary Proton Beam Transport System at J-PARC/JSNS and MUSE 1 (JAEA/J-PARC) Shin-ichiro MEIGO, Motoki OOI, Atsuhi AKUTSU, Kiyomi IKEZAKI DeeMee 1 st collaboration meeting 2012 Dec 10-11

2. Outline Introduction Beam commissioning status Beam optimization Flattening by using non linear optics Beam rotating for prolong muon target Issues for SiC target 2

3. Proton beam transport line 3 3NBT 3-50BT 3-GeV RCS 50-GeV MR Neutrino line MLF Neutro n target Muon target road to coast Length of BT: 314m Ep: 3GeV Power: 1MW Rep.:25Hz JSNS MUSE

4. 4 B ： 9 Q ： 54 STR ： 45 33m Whole length 320m

5. 5 Proton beam at the target 3NBT ・ MLF beam operational status User run stated since 2008 Nov Beam study with 0.5 MW beam User operation 0.3 MW beam Handling of high intensity proton beam Beam profile is important. Pitting damage (P4 Law: peak^4) Profile measurement with high reliability Condition of JSNS is harder than SNS SNS:60Hz, storage ring without muon target JSNS:25Hz, RCS with muon target Control of beam profile at JSNS becomes important Pin holes at target of SNS Pin holes are permitted at the inside wall of SNS but not allowed at JSNS Target vessel SNS: 4 walls JSNS: 3 walls here

6. Difficulties map of beam commissioning Difficulties at spallation neutron sources 6 Pulse operation Muon production MW operation Frequent of earth quake J-PARC○○○○ SNS○×○× PSI×○○× ISIS○○×× -CW beam eliminates issues of pressure wave at the mercury

7. 7 Diagnostics of beam profile and halo Monitors at PBW Imaging Plate MWPM Hot cell IP Target Placed by RH MWPM Halo monitor ・ SEC ・ TC  Beam profile monitor and beam halo monitor (online type) Multi Wire Profile Monitors (MWPMs) (15 sets located) : SiC wires At the proton beam window (PBW), MWPM located (1.8m from the target)  2D profile ： Activation by the Imaging Plate (IP) (Offline type) After beam operation: IP was attached at the target by the remote handling TC

8. 8 Beam behavior 120 kW 300 kW Good agreement with the design calculation 300kW:  h,v 5.7, 4.9  120kW:  h,v  2.7, 2.7  Result of RMS emittance Beam emittance and twiss parameters fitted by the observed beam width ⇒ Good agreement in whole beam line Consistence from the accelerator to the target. 300kW twiss parameter  x -1.84,  x 20.4m  y 0.57,  y 5.26m unit: mm mrad  5.4   x -2.35,  x 24.8m  y 0.89,  y 5.88m Twiss parameter at exit of RCS Calculation of 300 kW case (by RCS team) Residual dose at beam line: Back ground except several points

9. 9 Beam profile at the mercury target 2-D measurement by IP Result by MWPM Fitting by Gaussian Width of each pulse obtained Beam width transformed to the width at the target Profile result by the IP Fitted by two Gaussian curves Contribution of primary protons and secondary particles (mainly neutrons) 0.1 MW operation (2009 Dec)0.2 MW operation (2010 Dec) Obtained only 6 days of cooling duration after irradiation of 0.2 MW beam ⇒ Possible at 1MW with certain cooling time MWPM at the PBW

10. 10 Trend of beam width at the mercury target 2009 Apr (Run#22) 2009 Nov (Run#27) 2009 Dec (Run#28) 2010 Jan (Run#29) 2011 Dec (Run#36 200kW) hhvvhhvvhhvvhhvvhhvv MWPM17.310.322.811.024.411.733.816.654.322.6 IP17.312.323.811.527.012.733.215.455.720.6  Both results by MWPM and IP show good agreement Demonstration of reliable method Reliable peak density can be obtained by MWPM in real time. Unit: mm To obtain low peak density, beam width gradually expanded  Comparison of experimental results 2227282936

11. 11 Beam expand by linear optics MWPM shows that the distribution is monotonous Gaussian. Expanding Gaussian beam to decrease the peak density Vicinity of the target < 1W/cc(0.04J/cc/pulse) Target blade < 90W/cc(3.5J/cc/pulse) Beam halo was approximated to follow as monotonous Gaussian. Conserve beam aspect ratio H:V=2.2:1 Heat deposition at vicinity ＜ 1W/cc  h <37mm,  v <17mm Target blade: no issues  Limit for 1MW operation without beam flattening system. Peak at the target: 14J/cc/pulse

12. 12 Conceptual design of flattening Beam edge folding by non-linear optics Linear optics Non-linear optics w/ octupole Phase space distribution (horizontal) Two of octupole magnets necessary for horizontal and vertical

13. 13 Beam optics using OCT Flattening by the realistic magnet field of OCT(K oct ), large beta function (  ) at OCTs is necessary for the phase advance of  and RMS emittance  K oct =1/  2 tan  Large  makes difficult to have large beam acceptance RCS collimator: 324  mm mrad (For  100m -> 0.36m in diam) From the preliminary result of the beam halo measurements, smaller acceptance than 324  mmmrad may be applicable. Having large  at OCT1,2 -> Beam acceptance to be100  mmmrad Present beam optics Beam optics for flattening by OCTs Large beta at OCT1,2

14. 14 Octupole magnets OCT1,2 installed at upstream of QC12, QNQ1 Placed at 3NBT and M1 tunnels Q-O magnets distance is 1m Pole length: 0.6m Bore diameter: 0.3m Install new steering magnet: Downstream of QC12 OCT1 OCT2 M1 tunnel 3NBT tunnel 1m OCT1 OCT2 1m Horizontal view Vertical view Octupole magnet (800T/m 3 ) O3060(Width 1.2m, Length 0.6m, 6t)

15. 15 Simulation of the profile DECAY-TURTLE (PSI version) One of result ignoring the reality Ignore muon production target Small acceptance of beam: 81  mm mrad Considerable peak reduction achieved without muon target W/O OCT W/ OCT Achieved quite flat shape! Profile at mercury target

16. Effect due to muon target Phase space distribution distorted as Gaussian Without scattering effect Phase space distribution at muon production target To minimize scattering effect Focusing on the muon target as small as possible Increase divergence ⇒ Smaller effect With scattering effect

17. Beam profile with muon target Peak density ~11J/cc/pulse Having larger aperture than 250  mm mrad and muon target

18. 18 Peak heat density by OCT Even in the beam optics having large beam acceptance such as 250 , reduction of the peak enables by the ~30% of Gaussian case. Beam flattening Pitting damage on vessel with He bubbler (5000h) Necessary improve of mercury target! damage (mm) Beam power at 25 Hz (kW)

19. Octupole magnetic field Fabrication completed Mapping by hole probe Field gradient 780 T/m 3 @671A Agreement with calculation Confirmation agreement with design calculation Ready for installation next year 671A Photo of Octupole

20. Beam power trend 20 -0.1-0.2 MW operation begun after earthquake. -After installation helium bubbler in the mercury, 0.3 MW operation begun High power with very high availability (~90%) (/sr/pulse) SNS(1MW) 4.2x10 12 J-PARC/JSNS(0.3MW) 5.4x10 12 Pulse neutron yield

21. Latest beam operation for users Extremely stable beam operation with high power such as 0.3MW Number of beam stop ~10 times/day with quite high beam availability of 99 % Frequent of down decreased by the conditioning of RFQ Beam stopping time dominating by the recovering loop of the LH2 for the moderator

22. 500 kW beam demonstration Beam power: 20 kJ/pulse -> 1.2 MW !! @ 60Hz World record! Exceeded SNS (Let’s prepare Guess record!) Number of shots limited < 3000 to avoid target failure until next summer Beam profile at the PBW - Sustained low peak density: 3J/cc/pulse Beam power during tuning - 0.5 MW for 30 sec with 25 Hz

23. Present Muon target Prolong lifetime of the fixed carbon target Already rotating target was ready in this summer. But due to insufficient time for maintenance and human power, muon target did not change. Life time concern for next summer ⇒ Beam position changed every months (AKA EXILE) 23 H V Beam position at carbon target By focusing on the carbon target, beam loss kept lower R2.4mm now

24. Effect of leakage field of solenoid U-line solenoid leakage field bent the beam orbit at downstream of muon target 24 Auto compensation system has installed. By watching solenoid current, vertical steering magnet adjust the angle. Please erase the leakage field by H-line solenoid

25. SiC target DeeMee: SiC target (thickness up to 20mm) C Density: 1.82g/cc Atom density ： 9.13x10 22 Thickness 20mm SiC Si:C = 1:1 Density: 3.22 g/cc Atom density ： Si+C 9.67x10 22 Thickness: 20mm(?) Atom density comparable, however electron density 1.5 time of C

26. Simplified estimation Rutherford cross section d  /d  ∝ Z 2 /sin 4 (  ) C ： Z = 6 SiC: Z in average = (14+6)/2 =10 Scattering cross section 2.8 times of C Non elastic scattering (nuclear reaction) Cross section ～ A 2/3 （ geometrical cross section) C: 12 2/3 =5.24 SiC: (12 2/3 +28 2/3 )/2=7.23 Increase 40% Target loss due to the non elastic 4%-> 6% Loss 40kW->60kW for 1MW Logarithm scale in vertical

27. Beam loss distribution Beam Loss : excluded PBW - C: 64kW total (42 kW at target) - SiC 100kW total (64 kW at target) Simulation with DECAY-TURTLE As simplified estimation 1MW beam Cooling water problem

28. Effect on the profile at mercury target SiC - SiC with 2cm makes increase the heat at vicinities so that beam must be focused. ⇒ Consequently increasing the peak C

29. RI production in cooling water 29 20 system : Cooling water around muon target T and Be-7 production trend （ unit: Bq/cc/MWh) T production rate ： （ Calc ） 0.15 Bq/cc/MWh （ Exp ） 0.21 Bq/cc/MWh Good agreement for T production! Difficult to estimate Be-7 H-3 average Exchange 3 days

30. Summary 0.3 MW beam operation with excellent availability Achieved the most intense pulse neutron and muon facilities in the world Developing beam flattening technique using octupole magnet SiC target SiC makes worse effect on the primary beam To sustain similar effect: SiC thickness should be ～ 13 mm Issues for using SiC in thickness of 2cm Neutron production reduction of JSNS Peak reduction of current density at mercury target Revise scraper and install non-linear optics at M2 Difficulties of water handling around at muon target (In a few year, muon group will handle in any case.) Scenario of handling water is designed for C target with 2cm Shielding Shielding is design for C target with 2cm Licensing is necessary