Geant4 simulation of roman pots A. Kupco, P. Ruzicka, M. Tasevsky

Geometry setup 8 m 4.5 cm 10  (300μm Si + 100μm Cu) Steal 200μm 7 TeV proton Pot 1Pot 2 Simulation was done using stand alone Geant4.9 code The code uses QGSP-EMV hadronic physics list The number of generated events is Steal windows: 70% Fe, 19% Cr, 10% Ni, 1% Mn, density = 8.02 g/cm 3 Doped silicon: 28.5% Si, 39% F, 32.5% O, density = 2.5 g/cm 3 Copper of thickness 100μm is between each silicon layers

Geant4 studies Distribution of polar angle of proton momentum behind pot 1 Distribution of polar angle of proton momentum behind pot 2 Mean: 0.5 μrad RMS: 0.3 μrad gives mean error on the second pot 4 μm Mean: 0.8 μrad RMS: 0.46 μrad

Geant4 studies Energy spectrum of secondary charged particles in Si of pot 2 Distribution of number of secondary charged particles in Si of pot 2 Mean value of number of secondary particles in active silicon layer in the second pot is equal to These particles were created as result of initial proton pass through the first pot. 92% of events have no charged secondary particle 4% of events have one charged secondary particle Secondary charged particle position with respect to the initial proton (Xproton – Xsecondary)

Number of photons and photon energy spectrum in active silicon layer of second pot. Mean value of number of photons is equal to % of events are without photons 1% of events have one photon Geant4 studies Relative position of secondary gamma particles with respect to initial proton (X proton – X secondary ) in the active silicon layer of the second pot

Slice0 number of initial protons which die in pot 1 Slice1 number of initial protons which die in pot 2 Slice2 number of protons which survive 8 m Pot 1Pot 2 Geant4 studies 7 TeV proton

Geant4 studies Distribution of number of photons behind pot 2 Mean 0.9 RMS 5.4 Energy spectrum of photons behind pot 2. Mean 43 GeV RMS 81 GeV Energy spectrum of charged secondary particles behind pot 2. Mean 64 GeV RMS 101 GeV Distribution of number of charged secondary particles behind pot 2. Mean 1 RMS 5.5

Geant4 studies 7 TeV proton 4.5 cm 35.15% of events are lost Mean 10.8 RMS 33 Mean 3 GeV RMS 30.5 GeV Distribution of polar angle of proton momentum after passing 4.5 cm of steal Mean 5.2 μrad RMS 3.5 μrad

Summary The average polar angle of the initial proton behind the first pot is 0.5 μrad. This gives error in measurement in second pot 4 μm. Mean value of number of secondary particles in active silicon layer in the second pot is equal to 1.17 The 92.31% of events have no charged secondary particle. About 5% of events lose the initial proton due to passing the roman pots. In case that initial proton pass the 4.5 cm of the steal we lose 35% of events.

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