1. High Power Target Experience with T2K Chris Densham T2K Beamline Collaboration including RAL / KEK / Kyoto

2. Chris Densham NuFact 2010 p  120m0m280m 295 km on-axis off-axis 2.5 o Super-K -mon Target& 3 horns NearDetector T2K Beam-line

3. Chris Densham NuFact 2010 DV TS BD Hadron Absorber (Beam Dump) graphite core in helium vessel Target station (TS) Target & horns in helium vessel Helium vessel and iron shields cooled by water Decay Volume (DV) 94m long helium vessel cooled by water 6m thick concrete shield ‘280 m’ neutrino detector 30 GeV PS ring Primary beam line Fast extraction Kamioka T2K Beam-line p  120m0m280m 295 km on-axis off-axis 2.5 o Super-K -mon Target& 3 horns NearDetector

4. Chris Densham NuFact 2010 T2K Secondary Beam-line 110m Muon Monitor Target station Beam window Decay Volume Hadron absorber

5. Chris Densham NuFact 2010 T2K Secondary Beam-line 2nd horn 3rd horn BEAM Iron shield (2.2m) Concrete Blocks Helium Vessel Muon Monitor Target station Beam window Decay Volume Hadron absorber

6. Chris Densham NuFact 2010 T2K Secondary Beam-line Baffle 1st horn Target 2nd horn 3rd horn BEAM Iron shield (2.2m) Concrete Blocks Helium Vessel Muon Monitor Target station Beam window Decay Volume Hadron absorber

7. Chris Densham NuFact 2010 Specified Beam Powers for T2K Secondary Beamline design – towards a Superbeam Start-up schedule date: 1 st April 2009 –Actual first beam 23 April (Not bad!) Components built for Phase I: 0.75 MW –Beam window –Baffle (collimator) –Target + 1 st horn Phase II power: 1.66 MW –Road map anticipates within 5 years Components built for ultimate power:3-4 MW –Target station –Decay volume –Hadron absorber (beam dump)

8. Chris Densham NuFact 2010 8 Beam Graphite Blocks 3-4 MW Beam Dump / Hadron Absorber analysis Displacement (max) = 8.5 mm at 4 MW 620C o at 3MW Thermal convection links between blocks included in simulation Thermal convection links between blocks included in simulation Can survive for 3MW/30GeV Can survive for 3MW/30GeV Assumption: target in situ and horns operating

9. Chris Densham NuFact 2010 Hadron Absorber (Installed November 2008)

10. Chris Densham NuFact 2010 Design beam & target parameters for start-up (April 2009) Proton beam kinetic energy 30 GeV Average beam power 750 kW Protons per pulse 3.3× 10 14 Beam cycle 2.1 s Pulse width 5 µs Bunch structure 8 bunches Bunch length / spacing 58 ns / 598 ns Beam size at target (1σ) 4.2 mm Target material Graphite (Toyo Tanso IG430) Target radius 13 mm Target length 900 mm (c.2λ) Heat load on target 23.4 kW Peak temperature rise per beam pulse 200 K Cooling medium Helium (g), 32 g/s

11. Chris Densham NuFact 2010 Specification of Phase 1 Target Design c.20 kW (3%) of 750 kW Beam Power dissipated in target as heat Helium cooled to minimise pion absorption, to avoid secondary particle induced pressure waves from liquid coolants e.g. water to allow higher operating temperature (above 400°C to reduce radiation damage in graphite) Target rod completely encased in titanium to prevent oxidation of the graphite Helium cools both upstream and downstream titanium window first before cooling the target due to Ti-6Al-4V material temperature limits Pressure drop in the system should be kept to a minimum due to high flow rate required (max. 0.8 bar available for target at required flow rate of 32 g/s (30% safety margin)) It should be possible to remotely change the target in the first horn Start-up date: April 2009

12. Chris Densham NuFact 2010 Titanium target body Graphite ( ToyoTanso IG-43) Target Mk 2.0 Design Graphite to titanium diffusion bond Ti-6Al-4V tube and windows (0.5 mm thick) Graphite (purified) ( ToyoTanso IG-430) Aluminium support plate Isolators Stainless pipe + flange Titanium pipe + flange Remote connector + bellows + isolator (Al 2 O 3 )

13. Chris Densham NuFact 2010 Graphite to titanium diffusion bond Graphite-to-graphite bond Flow turns 180° at downstream window Inlet manifold Outlet manifold Upstream Window Target Design: Helium cooling path

14. Chris Densham NuFact 2010 Pressures (gauge) Pressure drop = 0.792 bar Helium cooling velocity streamlines Maximum velocity = 398 m/s

15. Chris Densham NuFact 2010 Steady state target temperature 30 GeV, 0.4735Hz, 750 kW beam Radiation damaged graphite assumed (thermal conductivity 20 [W/m.K] at 1000K- approx 4 times lower than new graphite) Maximum temperature = 736˚C

16. Chris Densham NuFact 2010 IG43 Graphite diffusion bonded into Ti-6Al-4V titanium, Special Techniques Group at UKAEA Culham Diffusion Bond + Graphite-Graphite bonding test Aluminium intermediate layer, bonding temperature 550ºC Soft aluminium layer reduces residual thermal stresses in the graphite Graphite-Graphite bonding Graphite transfer to Aluminium

17. Chris Densham NuFact 2010 All graphite components assembled and bonded in one operation

18. Chris Densham NuFact 2010 Final titanium components assembled and electron beam welded Upstream window Outer tube Downstream window

19. Chris Densham NuFact 2010 Pulsed beam induced thermal stress waves in graphite Max. Von Mises Stress = 7 MPa - cf graphite strength ~37 MPa – should be OK Bunch length: 58ns (Full width) 8 bunches/spill Bunch spacing: ~600(300) ns Rep. rate: 0.47 Hz Spill width ~5  s

20. Chris Densham NuFact 2010 Expected radiation damage of the target –The approximation formula used by NuMI target group : 0.25dpa/year –MARS simulation : 0.15~0.20 dpa/year Dimension change : shrinkage by ~5mm in length in 5 years at maximum. ~75μm in radius Degradation of thermal conductivity … decreased by 97% @ 200  C 70~80% @ 400  C Magnitude of the damage strongly depends on the irradiation temperature. –It is better to keep the temperature of target around 400 ~ 800  C Irradiation Temperature(  C) 400600 8001000 2dpa 1dpa -0.5% Dimension change 123 (dpa) 400 o C 800 o C Thermal conductivity (After/Before) Toyo-Tanso Co Ltd. IG-11 JAERI report (1991) Irradiation effects on Graphite

21. Chris Densham NuFact 2010 Target Remote Handling requirements Want to be able to replace a failed target and re-use Horn 1. –1 month cool down required (at 750 kW operation) –Horn 1 with failed target to be lifted from beamline and installed in Remote Maintenance Area –Failed target to be removed, new target installed, and Horn 1 assembly re-installed in beamline. –Failed target to be placed inside disposal flask Many limitations within Remote Maintenance Area –Very limited space –No crane access – lift tables only –Horn can only be installed in RMA with reproducibility of ±10 mm but target needs to be installed within horn to accuracy of ≈0.1 mm.

22. Chris Densham NuFact 2010 Installing spare horn 1 in the hot cell (August 2010)

23. Chris Densham NuFact 2010 Model of Target installed in 1 st magnetic horn

24. Chris Densham NuFact 2010 Target Exchanger Replacement target pre- installed here Exchanger docks to horn

25. Chris Densham NuFact 2010 Twin jack system used to offer up target exchanger to horn and to adjust angle Load cell, gimbals and spring system to prevent overload during operation

26. Chris Densham NuFact 2010 Final exchanger commissioning (August)

27. Chris Densham NuFact 2010 Load cell readouts from jacks crucial for docking exchanger to horn – more important than visual

28. Chris Densham NuFact 2010 Target Exchanger Commissioning

29. Chris Densham NuFact 2010 Experience from 1st physics run He Temp. (out) ≡ Tout He ΔT ≡ (Tout – Tin) Beam Power He flow rate

30. Chris Densham NuFact 2010 T2K target status summary Start-up date of April 2009 achieved During 1 st year of operation mk 1.0 target has run at 50 kW continuously and 100 kW short-term (few minutes) Upgrades to kicker magnet and target station should enable operation at up to 750 kW beam power Spare 1 st horn and 2 spare targets now ready Possible to replace targets within 1 st horn