Gbar beam stopper study dump and shielding F

Gbar beam stopper study: dump and shielding F. Cerutti, A. Ciccotelli EN-STI-FDA C. Theis HSE-RP-AS 25/04/2017 alessia. ciccotelli@cern. ch

Beam parameters and geometry Antiproton beam: 2 energy configurations: 100 Ke. V pbar and 5 Ke. V pbar Spatial distribution: σx =σy =1 mm Intensity: 5 E 5 pbar/s (average); 5 E 7 pbar/pulse Irradiation pattern: 200 days of beam on Cooling time: 10 minutes, 1 day, 1 week, 1 month, 1 year Annichilation in less than 1 μm in stainless steel Geometry: Stainless-steel beam stopper corresponding to the vacuum window Disk: r=5. 3 cm, h=1 cm Material: SS 304 L with 0. 2 wt% Co Beam Pipe + Vacuum window + Concrete shielding (Geometry 1, 2) → Dimensions are chosen for mechanical requirements 2

Geometries Stainless-steel beam pipe (rint=5 cm; rext=5. 3 cm) Stainless-steel cylindrical beam dump (r=5. 3 cm and 1 cm thick) Shielding geometry 1 40 x 40 cm 3 concrete Cylindrical opening (r=7 cm; L=20 cm) Shielding geometry 2 90 x 40 cm 3 concrete Wide opening of 50 x 20 cm 3

Materials Compound "Steel_304 L" definition: Density: 8 g/cm 3 CARBON 0. 03 CHROMIUM 18. 5 COBALT 0. 2 IRON 67 MANGANESE 2 NICKEL 11. 2 PHOSPHORUS 0. 0225 SILICON 0. 999 SULFUR 0. 015 wt% wt% wt% Compound "Concrete CERF with Europium": Density: 2. 4 g/cm 3 ALUMINUM 2. 11 wt% CALCIUM 23. 9 wt% CARBON 4. 38 wt% EUROPIUM 0. 00175 wt% HYDROGEN 0. 561 wt% IRON 1. 26 wt% MAGNESIUM 1. 51 wt% OXYGEN 48. 2 wt% POTASSIUM 0. 833 wt% SILICON 16. 2 wt% SODIUM 0. 446 wt% SULFUR 0. 414 wt% TITANIUM 0. 173 wt%

Annihilation peak • • • Annihilation peak and no ionization Antiprotons stopped completely into the dump π0 fluence

Nuclei recoil effect with 250 e. V/n transport threshold on the local energy deposition Nuclei recoil transportation neglect would produce a local energy deposition peak higher than the correct one.

Energy deposition and temperature rise pbar beam energy Peak energy density [Ge. V cm-3/primary] Peak energy density [J cm-3/pulse] Max temperature rise [°C/pulse] 100 Ke. V 1163 9. 3 2. 3 5 Ke. V 1583 12. 7 3. 2 The temperature rise is induced by the deposited energy (J/cm 3/pulse of 5 E 7 pbar/pulse) and evaluated taking into account a specific heat value 0. 5 [J/g°C] for SS 304 L and the density 8 [g/cm 3] 5 Ke. V 100 Ke. V ~900 nm ~140 nm Deposited energy density along the stainless-steel dump (expressed in Ge. V/cm 3). The bin size in the transverse direction is equal to 1 mm and in the longitudinal direction is equal to 10 nm. Temperature rise along the stainless-steel dump (expressed in °C/pulse).

Spectrum beyond the dump The antiproton beam is fully stopped in the dump but the radiation is dominated by the secondary particle produced by the annihilation. Part/primary Protons 0. 3 Neutrons 5. 5 Pions +- 1. 5 Antiprotons 0 Electrons 1. 8 Photons 23. 5 Positrons 1. 3 Muons 0. 005 Kaons 0. 006 Pi 0 0

Prompt dose (5 E 5 pbar/s) Averaged equivalent dose to the region between y=-10 cm and y=10 cm, x=140 cm and x=160 cm for both geometries (1, 2) Geometry 1 Geometry 2 Average between y=-10 cm and y=10 cm Considerably bigger backsplash

Prompt dose (5 E 5 pbar/s) Average between y=-10 cm and y=10 cm Geometry 1: equivalent dose is the same for 5 Ke. V beam and 100 Ke. V beam

Activation of stainless steel beam dump Irradiation pattern: 200 days of irradiation @ 5 e 5 pbar/second Residual nuclei activity after 10 minutes Residual nuclei production Z Element Nuclei /primary 1 H 2. 32 2 He 0. 92 26 Fe 0. 67 24 Cr 0. 34 25 Mn 0. 20 23 V 0. 15 22 Ti 0. 14 28 Ni 0. 09 Decay time Residual activity [Bq] 1. 74 E+04 10 min 183246 Sc 1. 03 E+04 1 day 124942 23 V 9247 1 week 99971 54 25 Mn 7544 1 month 65832 45 22 Ti 6308 1 year 16295 52 25 Mn 6040 55 26 Fe 5392 49 24 Cr 5088 A Z Element Activity [Bq] 51 24 Cr 3. 38 E+04 48 23 V 44 21 49 LE-design = 472 requires ~15 years of cool-down to reduce radiotoxicity by a factor of 500 rad. waste with clearance potential 10 minutes of cooling Mn-54 47% t 1/2 = Co-56 20% t 1/2 = Sc-46 12% t 1/2 = V-48 5% t 1/2 = Co-58 3% t 1/2 = Mn-56 3% t 1/2 = Mn-52 m 2% t 1/2 = Co-57 2% t 1/2 = Mn-51 1% t 1/2 = 2. 6968 e+07 6. 67958 e+06 7. 23928 e+06 1. 38015 e+06 6. 1223 e+06 9295. 2 483408 1272 2. 34835 e+07 2772 s s s s s [Source: [Source: [Source: CHROMIUM COBALT CHROMIUM : : : : : 0. 04%, 0. 35%, 39. 72%, 31. 17%, 1. 63%, 0. 00%, 4. 56%, 4. 48%, 0. 80%, 7. 84%, COBALT IRON COBALT : : : : : 0. 13%, IRON : 89. 32%, MANGANESE : 31. 14%, MANGANESE : 0. 00%, NICKEL : 0. 11%, IRON : 54. 00%, MANGANESE : 0. 08%, IRON : 59. 89%, MANGANESE : 0. 06%, MANGANESE : 0. 00%, NICKEL : 0. 15%, IRON : 89. 44%, MANGANESE : 0. 10%, IRON : 81. 13%, MANGANESE : 0. 10%, IRON : 81. 05%, MANGANESE : 0. 51%, MANGANESE : 0. 00%, NICKEL : 0. 09%, IRON : 75. 87%, MANGANESE : Usually unknown Co content is of minor importance in this case 6. 15%, NICKEL 68. 51%] 2. 79%, NICKEL 1. 58%, NICKEL 98. 31%] 9. 56%, NICKEL 1. 50%, NICKEL 1. 48%, NICKEL 98. 69%] 1. 07%, NICKEL 11 : 4. 35%] : : 3. 38%] 7. 27%] : : : 0. 85%] 12. 71%] 12. 89%] : 15. 13%]

Residual dose rate 16 u. Sv/h in front of hole ~4 u. Sv/h in front of hole beam 10 min cooling beam 1 hour cooling Residual dose rates compatible with Supervised Radiation Area 12

Residual DR, 200 days of operation 200 days @ 5 e 5 pbar/s + 10 minutes of cooling Classification still Supervised Rad. Area but higher exposure of maintenance personnel not optimized 13

Relative residual dose rate decrease Irradiation = 1 year, cooling t 0 = 10 min Concrete • Concrete cool-down factor of ~20 in 1 st month, steel factor of ~3 • Radiotoxicity of steel is higher than concrete Iron 14

Layout Beam dump (Stainless-steel and thickness 1 cm) + shielding 15

RP recommendations for shielding Use of concrete for shielding of beam stopper • Lead beam pipe into shielding assembly as deep as possible & shield backsplash • If dump is located towards the walkways/racks (1 st floor) then increase thickness of top shielding Assembly can of course be constructed by stacking individual blocks 60 cm • 80 cm beam stopper > 15 cm 40 cm (20 cm of concrete next to opening on each side) 60 cm recommended (min. total length 40 cm) 16