Production Target at J-PARC Hadron Experimental Facility Hitoshi - PowerPoint PPT Presentation

Production Target at J-PARC Hadron Experimental Facility Hitoshi Takahashi KEK / J-PARC Center

RCS n ＭＬＦ Hadron Bird’s eye photo in July, 2009

Hadron Experimental Facility (HD-hall) T1 target beam dump (50% loss) Extraction from K1.8BR K1.8 50GeV MR KL (K1.1) (High-p) (COMET) Switch Yard: 200m HD-hall: 56m ü Various secondary beams: p , K, p-bar, …. ü Currently only one production target: T1 ü KL: kaon rare decay ü K1.8, K1.8BR, (K1.1): strangeness nuclear physics, etc. ü New primary beam lines are now under construction (high-p, COMET)

Requirements for Production Target • Target to produce secondary beams (Kaons, pions, antiprotons, ...) for particle and nuclear physics experiments K1.8 K1.8BR • Charged secondary beam lines: K1.8, K1.8BR, (K1.1) → Point source is desirable in order to separate secondary particles. • Neutral secondary beam line: KL → Point source is desirable in order to reduce experimental background. Proton beam KL • Requirements ① Large mass number and high density for intensity and quality of secondary beams T1 target K1.1 ② Radiation hardness and chemical stability for stable operation (under construction) ③ Sufficient cooling efficiency for high-intensity beam Beam conditions slow extraction beam • Primary proton beam energy: 30 GeV 5.52s intensity • Spill structure: 2-sec extraction and 5.52-sec 2s Beam repetition • Beam loss at target: 50% • Beam size at T1 target: (σ x , σ y ) = (2.5mm, 1.0mm) time

Current Hadron Target Gold (6-divided) Target replacement using target driver Proton beam 66mm Cross-sectional view Copper *Gold, copper, and stainless-steel are bonded by HIP (Hot Isostatic Pressing) Stainless-steel target chamber Cooling water Ø Up to 50 kW beam Ø Indirectly water-cooled Ø Gold was chosen due to the good thermal conductivity and thermal expansion coefficient close to that of copper Ø Involved in airtight chamber and He gas is circulated to monitor the target soundness

Structure of Target chamber Water Fittings for (bored-through remote lifting Thermocouple connectors) (hermetic He connector) Beam windows He Airtight chamber Target Beam Driver Gold target Front view Since the beam windows are always exposed to a primary beam directly, we designed the windows to keep their soundness even in the case of 5- µ s pulse beams. * 5- µ s = revolution of Main Ring

Gas-Circulation System Gas storage tank (1.7m 3 ) 2 nd machine Circulating pump (5m 3 /h), bldg. Filter, Monitors Gas piping (total 180m) • To detect target failure within 5 min. To collect 99.9% of gas to storage • tank within 30 min. Gas storage tank (1.7m 3 ) Hadron experimental hall Proton beam Target chamber (0.23m 3 )

Beam Operation Ø Installation: Sep. 2014 Ø Beam ope.: Apr. 2015 - Temperature of each gold Temperature @41.6kW piece is measured with on spill (2sec) o ｆｆ spill (3.52sec) thermocouples every 100ms max 297 ℃ （ ΔT=267K ） f 0.5 mm sheath thermocouples 1.5 Beam 6 1 2 3 4 5 6 Copper beam-power dependence 350 Max. temp. rise (K) 300 250 200 data 150 calc 100 50 Measured temperature was in 0 good agreement with calculation 0 10 20 30 40 50 Beam power (kW)

Upgrade Plan of Production Target • Current • indirectly water-cooled gold target • up to 50 kW • Next • indirectly water-cooled gold target with improved structure • up to 80 kW • fabrication process is established • will be installed in 2019 • Next to next • directly cooled rotating euro-coin target • water or He-gas cooled • up to 150 – 200 kW • several R&Ds are in progress • will be installed in 2022?

Indirectly water-cooled fixed target • Gold target with copper cooling block is turned over and stacked on another gold target. • Each of the gold targets has almost same structure as current target. • Size of gold is optimized for secondary-beam yield and cooling efficiency. • ~80 kW proton beam can be accepted. • Fabrication process is already established. Ready to manufacture Results of thermal analysis (80kW, 5.52s cycle) temperature von Mises stress 1 1 (Only the lower max 333°C block is shown) MX MX MN Y Y Z Z X X 6 MN beam beam bonded interface bonded interface 46MPa sold-target161128(Au0-6,ƒ Ð 2.5,1.0) @ 30GeV-9.19e13ppp @ 5.52s, c1 t161128(Au ƒ Ð 2.5,1.0) @ 30GeV-9.19e13ppp @5.52s-cycle c1 237°C Design margin: 2.7 View from upstream vertical expansion: max 0.10mm

Directly cooled rotating target Au or Pt • “Euro Coin” target • nickel disks with gold or platinum edge Ni • Water cooled or He-gas cooled • Several R&Ds are in progress temperature von Mises stress Results of max 72 °C beam beam thermal analysis 1 1 ANSYS 15.0 FEB 20 2015 10:10:32 ( D T=42K) NODAL SOLUTION STEP=4 (Au, 150kW, bonded interface SUB =1 MX TIME=116 MN SEQV (AVG) MX PowerGraphics 6.3MPa EFACET=1 5.52s cycle) water AVRES=Mat DMX =.243E-04 SMN =177808 Y Y SMX =.631E+07 cooled X X Z Z MN thermal stress is max 200 °C kaiten120-346-1 (Au-Ni,ƒ Ð 2.5,1.0) @ 30GeV-18.72e13ppp @ sold-kaiten120-346-1 (Au-Ni,ƒ Ð 2.5,1.0) @ 30GeV-18.72e13ppp @ beam beam considerably smaller 1 1 ( D T=170K) than that of indirectly MX MX cooled target He gas Y Y X X Z Z cooled MN MN bonded interface 15MPa kaiten120-346-1P-He (Au-Ni,ƒ Ð 2.5,1.0) @ 30GeV-187.2e13ppp @ 100w/m2/k sold-kaiten120-346-1P-He (Au-Ni,ƒ Ð 2.5,1.0) @ 30GeV-18.72e13ppp @

Rotating method Previous design New idea water turbine He gas turbine motor shield blocks No need for motor and long shaft • airtightness of chamber can be achieved easily rotating disk • simple and small target components in high- radiation area issues: • airtightness of chamber • large system in high-radiation area

Comparison of cooling/rotating methods water He gas • good cooling efficiency • clean (small amount of NOx, H gas, and tritium • capable of higher beam power generation) • large rotating torque • no need for water circulation • need corrosion resistance system • large amount of tritium • cooling efficiency is unknown generation • rotating torque is unknown • need R&Ds of water • need large-flow He-gas circulation system circulation system • pumping up from bottom tank • ion exchanger • recombinator • also need He-gas circulation system • moisture is contaminated to He gas

Bonding test of “Euro Coin” Electron Beam Welding Au or Pt Au + Ni Pt + Ni Ni 10mm Au Alloy Ni Pt Alloy Ni • alloy layer is thick (~2mm) • beam was deflected to gold side • need more optimization Au + Ni Hot Isostatic Pressing • applied to current hadron target (Au+Cu) • thin boundary layer (several ten microns) between Au(Pt) and Ni

Gas turbine test mockup for target disks (iron) outlet ( f 8mm) bearing gas gas blow turbine • Simple rotation test using exhaust of scroll pump • The gas turbine (plate fan) was prepared by disassembling and modifying a commercial blast fan

Result of gas turbine test 500 450 Rotation speed (rpm) 400 350 300 250 200 150 120rpm 100 assumption in 50 thermal analysis 0 0 20 40 60 80 100 Time (min.) Target disks can be driven even with flow rate of scroll pump (~35 l/min) Next step • rotation test with He gas • rotation speed control (feedback system) • bearing, rotation speed monitor, .....

Efficiency of He-Gas Cooling Simple flat disk(s) Single disk 3 disks gas blow rotating disk Cooling efficiency for the inner disk compared with the outer disks flat type: less than half Spoke-type disk(s) • • spoke type: almost same Single disk 3 disks

Beam Windows of Target Chamber Current: Titanium alloy (Ti-6Al-4V) Titanium alloy ( f 300-t4mm) • Thermal stress: OK up to 10 7 cycles (~ 15k hours) • Accumulated strain due to creep deformation: will reach the endurance limit (1 %) in ~50 kW x 7.5k hours => This limited the life of current target Nickel flange Beryllium (brazed to Be) ( f 460-t8mm) Next: Beryllium or Titanium alloy (with improved cooling)

Soundness of Be windows (80kW) S M : design stress intensity (=UTS/3.5) Material Case Estimated Stress Allowable Stress 48 MPa (edge) Maximum static stress 133 MPa by atmospheric pressure 31 MPa (center) (1.5xS M @100°C) Equivalent 3.7 MPa 126 MPa Shot by shot Upstream stress (10 7 fatigue str. @100°C x1/2) ( D T=3.6K) Beryllium amplitude 3.8 MPa 126 MPa in normal 3 mm t Average temp. (10 4 fatigue str. @100°C x1/2) ( D T=3.9K) operation 166 MPa Thermal stress range 256 MPa by 5- µ s beam ( D T=93K) (3xS M @150°C) 42 MPa (edge) 133 MPa Maximum static stress 27 MPa (center) by atmospheric pressure (1.5xS M @100°C) Equivalent 2.8 MPa 126 MPa Shot by shot Downstream stress (10 7 fatigue str. @100°C x1/2) ( D T=3.2K) Beryllium amplitude 17.2 MPa 126 MPa in normal 6 mm t Average temp. (10 4 fatigue str. @100°C x1/2) ( D T=18K) operation 151 MPa Thermal stress range 256 MPa by 5- µ s beam ( D T=93K) (3xS M @150°C) In all cases, estimated stress are lower than allowable stress. *allowable stresses are according to JIS-B8266.(construction for pressure vessels)