1. Background comparison between 20 mrad and 2 mr crossings Takashi Maruyama SLAC Machine-Detector Interface Workshop SLAC January 6-8, 2005

2. Two Crossing Angle Schemes with SiD Detector 20 mrad2 mrad L* = 3.51 m L* = 4.05 m R =2.5 cm R = 1 cm Geant 3 (e+/e-, photons) and FLUKA (neutrons)

3. More Geometry BNL Compact SC for QD0 QF1 for 2 mrad crossing Extract beam through coil pocket Spencer’s iron magnet with field map Poletip field: 10.5 kGauss, r=0.5 cm Length: 1.7 m

4. Background sources Sync radiations from beam halo - 2 mrad crossing Beam-beam pairs –120 K / BX – = 2.7 GeV Radiative Bhabhas –460 K / BX – = 195 GeV  hadrons (Barklow’s new calculation) –  =3.2  10 5 pb (0.77 events/BX) Beam parameters: TESLA TDR for 500 GeV

5. Beam extraction the 2 mr horizontal crossing scheme Sync radiations hit the face of QF1 RED: halo, upstream quads GREEN: halo, QD0 BLUE: disrupted beam, QD0 Disrupted beam with sync photons Beam can be extracted through QF1 coil pocket. QF1 fringe field ~3 kGauss.

6. Sync radiations in 2mrad crossing No sync radiations from beam core or disrupted beam would hit QF1. Sync radiations from beam halo hit QF1. QD0 upstream QD0 (MeV) 43. 5.7 # N/e- 23.5 8.6 Hit rate (%) 4.4 35. Power (kW) 2.0*f halo 0.78*f halo –Photons backscattered to IP < 200 photons/BX for f halo =10 -3 –Photo-neutrons (FLUKA) < 1  10 8 neutrons/cm 2 /yr for f halo =10 -3 0.1 1 10 100 Energy (MeV) From QD0From upstream QD0 f halo : halo fraction We really don’t know.

7. Pairs at Z = 315 cm r 2 cm X (cm) 20 mrad 2 mrad

8. Pairs in two schemes 20 mrad2 mrad QD0 QF1 QD0 QF1 < 40 GeV e+/e- hit LUMON or QD0 QD1

9. Energy Deposition 20 marad2 mrad

10. Neutron flux at Z = 0 cm (FLUKA) 20 mrad Pairs: 3.6  10 8 n s /cm 2 /yr Rad. Bhabhas: 1.1  10 8 n s /cm 2 /yr 2 mrad Pairs: 2.3  10 8 n s/ cm 2 /yr 20 mrad 2 mrad Neutron source (cm) M1 QD0 QF1 Beam pipe R at Z = 0 cm 0.01 0.1 1 10 100 Energy (MeV)

11. Conclusions Background seems tolerable for both crossing angle schemes. More pair-energy will be deposited in –LUMON for 20 mrad –QD0 for 2 mrad. Similar neutron flux at 2-4  10 8 /cm 2 /yr