1. Question from the GDE : Could local “doughnut” type muon spoilers like those in SLC be substituted for the 5 meter magnetized wall? 5m magnetized wall Plot showing how the 5m wall disperses muons from a single source which reach the IR hall Push-pull, single IP detector L. Keller October 31, 2006

2. Issues: 1.The wall is used to reduce detector background AND for personnel protection when the IR hall is occupied and beam is on the tuneup dump. 2.In the case of a failure of all “beam containment” devices, the maximum dose rate in an occupied area is 25 Rem/hr, so some sort of wall is needed – use 1 meter of steel, unmagnetized, as a bare-minimum wall. An errant beam is prevented from hitting the wall by burn-through-monitors in stoppers and protection collimators. Don’t worry about 1 TeV CM now: Will have experience with magnitude of halo Will need to fill in missing E coll dipoles The wall can always be made thicker if necessary. October 31, 2006

3. B Doughnut spoiler a la SLC dc winding, ~300 A, 10 turns beam hole 5 cm diam. 1.4 m diameter, 4.0 m long October 31, 2006 (beam hole not to scale)

4. Plot showing trajectories of muons which reach the IR hall with 11 four meter long, 1.4 m diameter magnetic spoilers in the collimation sections. 1 m thick un-magnetized steel wall Push-pull, single IP detector Spoilers are toroidal, magnetized “doughnuts” October 31, 2006

5. Number of Muons per Bunch Hitting a 6.5 m Radius Detector from each of 14 Sources in the Collimation Sections 5 m magnetized wall fills tunnel at Z = 349 m, intergral = 13 muons/bunch 11, four meter long, 1.4 m diam. toroidal spoilers, same polarity, integral = 8 muons/bunch 11, four meter long, 1.4 m diam. toroidal spoilers, alternating polarity, integral = 5 muons/bunch #/source October 31, 2006 Distance from the IP (meters) betatron section energy section

6. 2.5 m radius TPC, 200 bunches 2.0 m radius TPC, 160 bunches 5 m wall, integral = 387 11 toroidal spoilers, same polarity, integral = 448 11 toroidal spoilers, alternating polarity, integral = 290 11 toroidal spoilers, same polarity, integral = 847 11 toroidal spoilers, alternating polarity, integral = 538 5 m wall, integral = 192 #/source Distance from the IP (meters) October 31, 2006

7. Condition 6.5 m radius detector 1 bunch 2.5 m radius TPC 200 bunches 2.0 m radius TPC 160 bunches 5 m long magnetized wall fills tunnel at 349 m 13387192 11, 4 m long “doughnuts” same polarity, 1 m unmagnetized wall 8 (all same sign) 847 (all same sign) 448 (all same sign) 11, 4 m long “doughnuts” alternating polarity, 1 m unmagnetized wall 5538290 Summary Table Number of Muons in Detector for Three Shielding Conditions Push-pull IR, 500 GeV CM, BDS 2006c * Collimate 0.1% halo, muons from both beams October 31, 2006

8. Condition Z = 340 m (just behind wall)Z = 200 mZ = 100 mIR hall Beam hits stopper 1 at Z = 1490 m 0.230.120.100.09 Beam hits stopper 2 at Z = 1197 m 0.400.240.170.15 Muon Dose Rate in Occupied Areas in Maximum Credible Accident (Rem/hr) Limit is 25 Rem/hr Push-pull IR, 500 GeV CM, BDS 2006c Shielding conditions: 11 doughnut spoilers, field off 1 m unmagnetized steel wall at Z = 349 m E coll dipoles off – required for occupancy * The dose rate from neutrons and photons is smaller in all cases October 31, 2006

9. Summary: 1.Compared to a 5 m magnetized wall at Z = 345 m from the IP, a series of eleven, four meter long, 1.4 m diameter magnetic spoilers will reduce the number of muons/bunch in a 6.5 m radius detector from 13 to 5. 2.Compared to a 5 m magnetized wall at Z = 345 m from the IP, a series of eleven, four meter long, 1.4 m diameter magnetic spoilers will increase the number of muons/160 bunches in a 2.0 m radius TPC from ≈200 to ≈300. 3.In a worst case accident where all electronic beam containment devices fail, the maximum dose rate behind a 1 m steel shield wall is < 1 Rem/hr, well below the 25 Rem/hr limit for such an accident. October 31, 2006