Geant4 simulation of roman pots

A. Kupco, P. Ruzicka, M. Tasevsky

Geometry setup

8 m

4.5 cm10(300μm Si + 100μm Cu)

Steal 200μm

7 TeV proton

Pot 1 Pot 2

• Simulation was done using stand alone Geant4.9 code

• The code uses QGSP-EMV hadronic physics list

• The number of generated events is 200 000

Steal windows: 70% Fe, 19% Cr, 10% Ni, 1% Mn, density = 8.02 g/cm3

Doped silicon: 28.5% Si, 39% F, 32.5% O, density = 2.5 g/cm3

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 studiesEnergy 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 1.17. 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 0.55

• 95% of events are without photons• 1% of events have one photon

Geant4 studies

Relative position of secondary gamma particles with respect to initial proton (Xproton – Xsecondary) 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 1 Pot 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.

Thank you for your attention