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Future upgrade of the neutrino beam-line for multi-MW beam

Future upgrade of the neutrino beam-line for multi-MW beam. 5 th Hyper-Kamiokande open meeting @ Vancouver July-20-2014 Yuichi Oyama (KEK) (for T2K neutrino beam-line group). Introduction.

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Future upgrade of the neutrino beam-line for multi-MW beam

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  1. Future upgrade of the neutrino beam-line for multi-MW beam 5th Hyper-Kamiokande open meeting @ Vancouver July-20-2014 Yuichi Oyama (KEK)(for T2K neutrino beam-line group)

  2. Introduction • When the J-PARC project started, the primary goal of the beam power in the neutrino beam line was 750kW. Upgrade to 4MW was second step in the future. • ~750kW beam from the accelerators will be within our reach by ~2017 if the budget is funded timely. It is possible to accept this beam power, with significant improvement for steady operation. • For operation beyond 750kW, critical improvements are needed. • In this talk, future upgrade required for ~2MW beam power is reported.

  3. Beam History • At the beginning, 750kW x 5year operation was officially approved, where 1 year is defined as 107sec = 115.7days. For 30GeV proton beam, it corresponds to 7.81 x 1021protons on target (pot). 3.2s3.04s 145kW 2.48s235kW Rep=3.52s 50kW 2.56s 190kW 2.48s 235kW [6bunches] ~7.3x1020pot until Jun.24,’14 6.63x1020pot until May.8,’13 Neutrino beam x1019 Anti-neutrino beam 3.01x1020pot until Jun.9,’12 1.43x1020pot until Mar.11,’11 Hadron Hall accident Run 1 Recovery from the earthquake Run 2 Run 5 Run 3 Run 4 • Stable operation at ~230kW has been achieved. Until June 2014, 7.39x1020 pot is accumulated. It is ~9% of our goal.

  4. Future Improvements for higher beam power (if the budget is funded as we hoped) T.Koseki in J-PARC symposium 2014 (http://j-parc jp/j-parc2014/) andT.Ishida in this HK open meeting • Present expected beam parameters for ~750kW will be~1.3sec Main Ring cycle and ~2.0x1014ppp (proton per pulse).

  5. Neutrino experimental facility at J-PARC RCS Beam Dump Near Neutrino Detectors Muon Monitors Decay Volume Target & Hornsin Target Station Main n m p P Ring 295km To Kamioka Primary Beam-line 110m 280m Extraction Point MLF

  6. Primary Beam-line Final focusing (FF) section 10 normal conducting magnets Preparation section 11 normal conducting magnets Arc section 28 superconducting combined func. magnets

  7. Primary Beam-line • All magnets in the primary beam-line , thickness of concrete tunnel and surrounding soil are designed by assuming 1W/m energy loss in Arc section, 750W loss in the preparation section, and 250W loss in the final focusing section. • When the beam power become multi-MW, emittance of the beam may become drastically larger. Much larger energy loss would be generated. • A tuning of the beam orbit as well as the beam size is important to avoid radio-activation. Beam monitors are critical for the tuning. • If emittance of the beam becomes much larger, some of the magnets must be replaced with new design of large apertures. • Production of new magnets are not difficult from a viewpoint of technology. Production period of a few years, and shut-down for installation of a few month to one year, depending on the new beam parameters, are required.

  8. Secondary beam-line Target Station Beam Transport From RCS to MLF Beam Dump Decay Volume OA2o OA2.5o 6m-thick concrete wall OA3o Helium Vessel For 3 Horns,See Sekiguchi-san’s talk 3rd Horn Beam Window 2nd Horn Target and 1st Horn

  9. 30GeV-750kW(~20kWheat load) 736oC Target • Carbon Graphite of 26mmf x 910mmare embedded in Ti-6Al-4V of0.3mm thickness. • The design was based on calculationof thermal stress and flow of Heliumgas cooling. • The present design can accept 3.3x1014 (ppp) x 5 years with a safety factor of 2. This corresponds to 1.2MW if 1.3sec of Main Ring cycle is assumed. (750kW beam with 3.3x1014 ppp and 2.1s MR cycle was the initial plan.) • Larger beam diameter will be needed for future higher power. 26mmf x 910mm CFX analyses He gas cooling: 9Nm3/m (v=200m/s) Graphite Conductivity 14020W/mK(rad. damage) Ti-6Al-4V (0.3mm-t) DT~200K ~7MPa (Tensile strength 37MPa)

  10. Beam Window • Separate Helium vessel from vacuum in primary line.Double wall of 0.3mm thick Ti-6Al-4V, cooled by He gas (0.8g/s) • Stress by partial heat load at the beam spot may break the window ! • The present design can accept 3.3x1014 (ppp) with a safety factor of 2 . This corresponds to 1.2MW if 1.3sec of Main Ring cycle is assumed. • Change the diameter of the beam and/or upgrade the cooling systemis needed for future beam.

  11. Radiation damage for Ti-6Al-4V • Radiation damage may change the characteristics of the thermal stress of the material. • The radiation damage of the Ti -6Al-4V was reported up to 0.24DPA (displace per atom), which correspondsto ~1.5x1020 pot.We are already in unknown region. • Replacement cycle of the window shouldbe considered. However, 2MW x 1 yearbeam corresponds to 4x1021 pot.Replacement more than once per yearis impossible. • Test of radiation damage is needed.We are planning an internationalcollaboration for this test.Ask Ishida-san. • According to the results of the test,use of another target/window materialmight be needed. 0.24DPA Ti-6Al-4V 0 DPA 1000MPa Stress (Mpa) Limit:400MPa ? with fatigue & high temp. 200MPa 70MPa(220kW) Strain (%)

  12. Helium Vessel, Decay Volume and Beam Dump • Large fractions of the beamenergy are absorbedin HV/DV/BD. • Thermal stress may damagethe structure of HV/DV.Their temperature must bekept less than 60 degree. The temperature of the beam dump core must be less than 400 degree. • They are cooled by cooling water system. At present, the system is adjusted for the 750kW operation. • Cooling power can be upgraded by increasing flow rate of the cooling water. Additional pumps and related components as well as the space for them in the machine room are needed. • Radioactivity of the cooling water will become higher.This is another serious problem.

  13. Helium Vessel • Thermal analysis shows that there is safetyfactor 3 for ~750kW beam. • Additional iron shields between the magnetic horns and side wall of the Helium Vessel are required for multi-MW beam. Max. stress: 47 MPa Max. temp: 54 ºC

  14. Decay Volume • Rectangular pipe of 3m(W) x 5m(H)x 100m(L), connected with TSHelium vessel. Total volume with TS Helium vessel is 1500m3. • Cooling water system for the iron walls. • Ready for 750kW without any upgrade. • Upgrade of cooling water flow rate is neededfor multi-MW. Max. temp：55C 14

  15. Beam Dump • Graphite core of 2.8m(W) x 5.3m(H) x 3.2m(L),14blocks. Max. temperature < 400 degree. • Aluminum blocks are cooled by water • Ready for 750kW without any upgrade • Upgrade of cooling water flow rate is needed for multi-MW. Max. temp:180℃ 15

  16. Radiation Issue Many restrictions about radiation in the neutrino beam-line. Radiation dose outside of the radiation control area: < 0.5mSv/h Radioactivity in disposed water: for 3H < 60Bq/cc < 5000GBq/year (from J-PARC) for 7Be <30Bq/cc < 1200MBq/year (from neutrino facility) Exhausted Air from stacks of buildings (Target Station): for 3H < 5mBq/cc for others < 0.5mBq/cc (mainly 41Ar)

  17. Cooling Water system and Radioactivity Three independent cooling water systems HV/DV water system DV/BD cooling water system （Helium Vessel and DV upstream） （DV downstream and BD） Horn cooling water system • Neutrons and other beam products break Oxygen In H2O and many kinds of isotopes are produced as spallation products.They are 3H,7Be,11C, 13N, 15O, 14O, 16N,14C. • Lifetime t1/2 < 20minutes : 11C, 13N, 15O, 14O, 16Nt1/2 = 5730 years : 14CTheir contribution can be ignored. • The source of radioactivity is 3H (t1/2 = 12.3 years) and7Be (t1/2 = 53.3 days).

  18. Ion exchangers Drainage of Radioactive Water One “drainage cycle” is 1)Buffer Tank -> DP tank 2)dilution and measurement3)drainage from DP tank • Schematic flow of the drainagesystem for radioactive water NU2 TS dilution water Horn CW Off limit during beam Also beam-on Ion exchangers DP tank Only beam-off drainage (2 tanks are used together) 21m3 Buffer tank B2 tank HV/DVCW H2SO4 NaOH (effectively 84m3) Ion exchangers pHcontrol system All drain water 30m3 Drain tank • One drainage cycle per 3 business days. • 42Bq/cc x 84m3 = 3.5GBq of 3H can be disposed per one drainage cycle.

  19. Prospect for Radioactive Water Drainage • We can ask a part of drainage to another section in JAEA by using a tank truck. Ready for 750kW beam. • 3 parallel drainage system with larger disposal tanks are needed for 2MW beam.

  20. New Buildings in the neutrino beam-line RCS Present facility buildings are too small to install upgraded facilities. Beam Dump Near Neutrino Detectors Muon Monitors Decay Volume Target & Hornsin Target Station Main n m p P Ring 295km To Kamioka Primary Beam-line 110m 280m MLF Extraction Point • We are planning to build new facility buildings for new cooling water system, new disposal tanks, and other facilities. • We need ~2 years for construction, and full 1-year shutdown?

  21. Radioactivity in Exhausted Air ~0.3mBq/cc at stack (must be < 0.5mBq/cc.This radioactivity ismonitored in real-time) Ventilation system 13000m3/h Negative pressure ~3mBq/cc in ground floor Leakage of radioactive air through gaps ~1000mBq/cc in machine room ~5000mBq/cc in service pit @230kW beam (after many efforts)

  22. Air-tight work in Target Station Caulking betweenconcrete shields Air-tight lamination(in future) Caulking+ Air-tight sheet Protection sheet under air-tight sheet Air-tight sheet(made of the samematerial for balloon) Protection sheet (over air-tight sheet) More careful air-tight in future !

  23. Bypass of Ventilation in Target Station Ventilation flow rate 13000m3/hcannot be changed • By making bypass route of the air,ventilation rate of TS ground floorreduced to be 1/10. • Radioactivity in the exhausted air become 1/3 of non-bypass mode. • About 60% of 41Ar (t1/2~110mins) decay in ground floor. Radioactivity in the ground floor increased by factor ~3. • Further change of the bypass rate will be needed for higher beam power…

  24. Summary List of works to accept ~2MW beam • Replacement of some of the magnets in the primarybeam-line? • New design of the target? • New design of the Beam Window, and study of the radiation damage? • Additional iron plate in Helium Vessel. • Upgrade of the cooling water system -> New buildings • Upgrade of radioactive water drainage -> New building • Upgrade of Air-tight in the Target station building • Bypass ventilation system • Other works not covered in my talk…… Many works are definitely neededto accept ~2MW beam…….

  25. END

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