1. Vacuum windows at JPARC Contents Introduction Vacuum windows at hadron beam line Helium gas cooling Vacuum windows at neutrino beam line primitive discussion Yoshikazu Yamada (KEK) T.Ishii, T.Iwashita, M.Minakawa, Y.Oyama, H.Takahashi, et.al. 4th International Workshop on the Neutrino Beams and Instrumentation November 10, 2003

2. Hadron & Neutrino beam lines Neutrino beam line Hadron beam line 50 GeV PS Neutrino beam line Single turn fast extraction 8 bunches in 5  s 3.3x10 14 proton/spill Cycle: 3.53 sec. Hadron beam line Slow extraction: 0.7 sec. Time(sec.) 0.7sec.

3. Windows in hadron beam line Fast reaction valve SY Vacuum window 10 -6 ~10 -8 Torr Turbo & Ion pump 10 -3 Torr Rotary pump 50GeV PS ： 10 -8 Torr Vacuum chamber :20cm- , SS or Al or Ti Connected by ‘Radial seal’ Window for T1-upstream Window for T1-downstream Window for Dump Container of T1-target (air and water inside) Beam dump (Low Pressure?) NP-hall Switch Yard

4. SY vacuum window Separate vacuum in SY(10 -3 Torr) from one in 50GeV-PS (10 -8 Torr) Aluminum : 20cm- , 100  m-t Edge : cooled at 30ºC by water or air Average deposit: 3.5J/spill  Temperature rise : 16(K) (SS: 480(K) ) (MARS+ANSYS) Radius (cm) Deposit (W/m 3 )  r ~ 1cm Aluminum window +16(K)

5. Time dependence of temperature AluminumStainless Steel T>1 min. ： T=30 +16 ± 4 (ºC) T>20 min. ： T = 30 + 480 ± 10 (ºC) Time(sec) Center Temperature(ºC) 600 0 30 46 30 300 Temperature(ºC)

6. Beam window for T1-target Water Air Primary beam line:~10 -3 Torr Vacuum chamber ~10 -3 Torr Upstream windows for T1 diameter:10cm Downstream windows for T1 diameter:30cm He 1g/cm 2 1m/s He T1 target Double wall (SS or Al) cooled by He flow in gap gap: ~1cm remote maintenance Beam axis SS SS/Al T1 container

7. Upstream window for T1 (T1-U) Separate vacuum of beam line (10 -3 Torr) from air(1atm) in T1 container SS/Al (beam-line side) and SS (T1 side) : 10cm- , variable thickness Cooled by He(1atm & 1m/s) between two walls Average deposit:10.2 J/spill on SS window (9.2 J/spill if t=100  m) Radius (cm) Deposit (W/m 3 )  r ~ 2mm Radius (cm) Thickness (cm) 100  m 2.5mm SS window

8. Temperature of window T1-U Temperature rise : 320 (K) Natural convection : 10W/m 2 /K Temperature rise : 160 (K) Forced convection : 100W/m 2 /K Outer edge : cooled to be 30ºC by water or air One surface : cooled by convection by Helium SS window +160(K) +320(K)

9. Deformation/Stress of window T1-U Deformation:0.7mm@center Max. stress due to pressure ： 200MPa@center ＜ Tensile strength:500MPa If t=0.1mm(uniform) deformation ： 2.1mm Stress ： 310MPa@center,1000MPa@edge SS window 0.7mm

10. Helium cooling at KEK-B factory He Heat transfer coefficient 1g/s (6l/s, 1.7m/s) 120W/m 2 K(measured by U.Tsukuba) 164W/m 2 K(calculation) 220W/m 2 K(measured by IHI) Water cooled Helium cooled Aluminum Beryllium Double wall of Beryllium Water cooled Vacuum chamber for interaction point ~100W heat

11. Helium cooling system He compressorHe cooler He tankwater pump water cooler

12. Downstream window for T1(T1-D) Separate vacuum chamber (10 -3 Torr) from air(1atm) in T1 container SS/Al (beam-line side) and SS (T1 side) : 30cm- , variable thickness Cooled by He(1atm & 1m/s) between two walls Average deposit: 1060 J/spill on SS window (115 J/spill if t=0.1mm)  r ~ 5mm 100  m 5mm Radius (cm) Energy deposit (W/m 3 ) Thickness (cm) SS window Radius (cm)

13. Temperature/stress of window T1-D Outer edge: cooled to be 80ºC Temperature rise: 170(K) @100W/m 2 K 810(K) @10W/m 2 K Deformation:3.3mm Stress due to pressure: 450MPa at center ~Tensile strength 500MPa SS window +170(K) 3.3mm

14. Window for beam dump Separate vacuum in beam line (10 -3 Torr) from air in beam dump Stainless Steel : 50cm- , variable thickness Simple wall or double wall with Helium cooling Average deposit: 136 J/spill (98 J/spill if thickness is 1mm-t) Radius (cm) Energy deposit on window (W/m 3 )  r ~ 5cm Thickness (cm) 1mm 5mm

15. Temperature/stress of window(dump) Outer edge: cooled to be 30ºC Temperature rise: 8(K) @100W/m 2 K 64(K) @10W/m 2 K Deformation:5.7mm Stress due to pressure: 200MPa at R=20cm <Tensile strength 500MPa SS window +8(K)

16. Preparation Section ARC Section (Super conducting) Final Focusing Section Windows in neutrino beam line Target Station PS vacuum window (?) Separate vacuum in PS&ARC&FF(10 -6 Torr) from one in 50GeV-PS (10 -8 Torr) 50GeV PS TS exit window(?) TS entrance window Final focus Decay volume (Helium) Helium container Target Station

17.  r ~ 6mm (smallest case) Window in Preparation Section Separate vacuum in PS(10 -6 Torr) from one in 50GeV-PS (10 -8 Torr) 20cm-  Al 26  m-t(?) or SS 10  m-t(?) (0.01% loss) (realistic?) Edge : cooled at 30ºC by water or air Average deposit : 0.68J/spill   T : Al:~14(K), SS:~520(K) But,  T by single spill  Al:~67(K), SS:~104(K) study on thermal stress and durability against heat cycle study with larger beam size Al 26  m-t Radius (cm) Deposit (W/m 3 ) Al 26  m-t +14(K)

18.  r ~ 6mm Window for entrance of TS Separate vacuum in PS(10 -6 Torr) from He gas (1 atm) in TS Aluminum : 5cm-  、 1mm-t (can be thinner) Edge : cooled at 30ºC by water or air Average deposit : 34J/spill   T ~18(K) But,  T by single spill  82(K) study on thermal stress and durability against heat cycle double wall and Helium cooling? Al 1mm-t Radius (cm) Deposit (W/m 3 ) +18(K)

19. Summary We started to study on windows for 50GeV beam line. Average temperature rise and deformation/stress by pressure were estimated by MARS+ANSYS Conduction cooling for aluminum windows for Switch Yard of hadron beam line Preparation Section of neutrino beam line (?) Forced convection cooling by helium gas for windows for Upstream/downstream of T1 target in hadron beam line Beam dump in hadron beam line Entrance window of neutrino target station (?) Exit window of neutrino target station (??)

20. Plan Study of thermal stress and shock wave Optimization of thickness Measurement of thermal transfer coefficient of He cooling Test production of windows and study durability Design and production of double wall window with ‘Radial seal flange’ system developed by Y.Yamanoi et.al. Proton beam He gas Double wall ‘Radial seal flange’

21. Backup

22. Hadron beam line in Switch-Yard Fast reaction valve SY Vacuum window 10 -6 ~10 -8 Torr Turbo & Ion pump (every 20m) 10 -3 Torr Rotary pump (every 20m) 50GeV PS ： 10 -8 Torr 30m Vacuum chamber :20cm- , SS or Al or Ti Connected by ‘Radial seal’

23. Hadron beam line in NP-Hall Window for T1-upstream Window for T1-downstream Window for Dump 10 -3 Torr Container of T1-target (air and water inside) 10m Beam dump (Low Pressure?)

24. 22m Neutrino target station Iron shield Helium container Machine room Service pit Stock room for activated parts 11m 33m Iron shield Concrete blocks 40t crane Target & 1st horn Beam window 2nd horn3rd horn Final focus Decay volume Concrete Beam window Ground level Baffle

25. T1 downstream window Diameter: ~30cm Vacuum side: Aluminum Air(T1) side: SS 0.1mm-t at center 5mm-t at edge (water cooled) Temperature rise of SS window at center +170ºC (forced convection by He flow(~1m/s) : 100W/m 2 K) +810ºC (natural convection : 10W/m 2 K)

26. Remote maintenance for T1 Maintenance work should be done at service space 1.Disconnect cables and cooling tubes. 2.Detach vacuum flanges. 3.Replace shields with cask. 4.Detach shaft, disks and upper plate, and move them to stock space. 5.Install new parts with cask. 6.Replace cask with shields. 7.Connect cables and tubes. requires remote maintenance tools shield motor water beam target beam Front view Side view 3m

27. Remote vacuum sealing Design specification Inner Diameter:  30cm Metal sealing Small leak:~1  10 -10 Pam 3 /s Remote operation Operation time: 1~5 min. Small force required Candidate Mechanical holding (V-block) Pillow seal Radial seal (under development) Prototype of “Radial seal” developed by Y.Yamanoi(KEK), M.Tsuchiya(IHI Ltd) and Usui Kokusai Sangyou Kaisya Ltd.

28. Remote lifting Tools Lifting tools from CERN and PSI Magnet Crane Specification Up to 40t Short height Remote connection Video camera viewing Two or four points lifting Interlock for one-side lifting Under design

30. Neutrino beam line ν μ beam of ~1GeV Target station Decay volume Beam dump Fast-extracted proton beam line 50GeV PS Super- Kamiokande  → x disappearance  → e appearance

31. Target and secondary beam lines K1.8 HR K1.1 K0 Production target : T1 Rotating Nickel disks thickness: ~54 mm radius: ~24 cm cooled by water developed by Y.Yamanoi et. al. Proton beam NP-Hall