Recent Studies on ILC BDS and MERIT S. Striganov APD meeting, January 24

Muon background from ILC BDS  Halo interacts with thin primary spoilers and produces electrons and photons  Electons and gammas hit thick secondary collimators  Electromagnetic shower produce muons – about muon/lost electron  Muon background can be reduced about 2000 by using two magnetized spoilers

New tunnel geometry

Magnetized wall

Concrete wall and doughnuts

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, 2m concrete wall – MARS 13 (3) 387 (152)192 (74) 11, 4 m long “doughnuts” same polarity, 1 m unmagnetized wall – Lew, 2m concrete wall – MARS 8 (9.6) (all same sign) 847 (1268) (all same sign) 448 (646) (all same sign) 11, 4 m long “doughnuts” alternating polarity, 1 m unmagnetized wall Summary Table Number of Muons in Detector for Three Shielding Conditions Push-pull IR, 500 GeV CM, BDS 2006c Black numbers – Keller, red numbers - MARS * Collimate 0.1% halo, muons from both beams October 24, 2006

Keller v.s. MARS Halo distribution: MARS and Keller – from STRUCT Interactions with primary collimator: MARS – internal routine, Keller – TURTLE (electron/positron only, no photon transport) Interaction with secondary collimator: MARS – internal routine, Keller – approximation of shower Muon production: MARS and Keller – based on same model Muon transport: MARS – internal routine, Keller uses MUCARLO – no fluctuation of energy loss, simplified multiple Coulomb scattering

Source TURTLE does not transport photons – there are no photons (about 60% of total energy) produced on primary collimator in Keller simulations. All photon energy goes to electrons/positrons. Secondary electrons/positrons and gammas produced in MARS calculations agree well with STRUCT.

Geometry update

Detailed comparizon

Conclusions Acceptable agreement between Keller and MARS calculations in collimation section Large differences in bending sections Zeuthen package based on GEANT3 gave 2-3 times more muons than MUCARLO (TESLA, 1994)

Target for muon collider

MERIT experiment The MERIT experiment, to be run at CERN in 2007, is a proof-of-principle test for a target system that converts a 4-MW proton beam into a high- intensity muon beam for either a neutrino factory complex or a muon collider. The target system is based on a free mercury jet that intercepts an intense proton beam inside a 15-T solenoidal magnetic. The Hg jet delivery system will generate a 1-cm diameter mercury stream with velocities up to 20 m/s.

MERIT geometry in MARS

Simulations tasks  Particle fluxes, energy deposition, absorbed doses and residual activities in experimental hall  Absorbed dose and activation of mercury vapor analyzer  Activation of hydraulic fluid  Activation of mercury vapor filter  Secondary particles production

Radiation levels Absorbed dose in Gy/ protons30day/1day residual activity in mSv/h

Radiation levels in detector elements Absorbed dose in mercury vapor analyzer is 630 Gy (top) and 14 Gy (back). Acceptable level is Gy. Residual dose rate on contact after 5 day of irradiation and 1 hour of cooling: mercury vapor analyzer – 0.17 mSv/hr (top), mSv/hr (back), hydraulic fluid – mSv/hr, mercury vapor filter mSv/hr. Acceptable level is about 1 mSv/hr at FNAL, 0.1(?) mSv/hr at CERN

Detector positions and particle fluxes per pulse ( protons). charged hadrons (E>200 keV) neutrons (E>100 keV)

Detector positions and particle fluxes per pulse ( protons). electrons (E>200 keV)gammas (E>200 keV)

Energy spectra ( 0 degree detector). Blue lines – all particles, red lines- particles created in attenuator.

Time distributions in 0 degree detector

Energy spectra ( 6.7 degree detector). Blue lines – all particles, red lines- particles created in attenuator.

Energy spectra ( 11.5 degree detector). Blue lines – all particles, red lines- particles created in attenuator.

Energy spectra ( 45 degree detector). Blue lines – all particles, red lines- particles created in attenuator.

Time distribution in 45 degree detector