Geant4 simulationsPonomarenko Daniil

02.12.2016

In this presentation:● Current model description:

○ Physics list;○ Materials;○ Geometry and optical surfaces.

● Evaluation of:○ N photons in the SiPM per event;○ Cherenkov/scintillation photons contribution;○ Regions where photons have been created;○ Photons energy distributions.

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Statistics: 5000 events

Model description (physics list)● Basic part is “QGSP_BERT_HP”

○ All electromagnetic processes are on boat

● Optical Physics ○ WLS

■ fWLSProcess->UseTimeProfile("delta");○ Cherenkov

■ fCerenkovProcess->SetMaxNumPhotonsPerStep(300);■ fCerenkovProcess->SetTrackSecondariesFirst(true);

○ Scintillation ■ fScintProcess->SetScintillationYieldFactor(1.);■ fScintProcess->SetTrackSecondariesFirst(true);■ fScintProcess->SetScintillationExcitationRatio(0.0);

○ Absorption○ Rayleigh scattering○ MieHG scattering○ Boundary

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MSPhysicsList.hh

MSOpticalPhysics.hh

Model description (Material HBP)

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● Absorption is preliminary.○ Have correct distributions, but conversion

from % to length is needed.

● Is emission zero?

Model description (Material EJ-309)

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● Chemical formula is wrong.○ Affects on Cherenkov process. ○ We have concentration of atoms per cm3.

● Scintillation from the EJ-309 pasport.○ Resolution scale?

● Absorption is preliminary. ● Briks constant is preliminary.

○ What is correct value?

Model description (Optical surface)

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Plate / Air

EJ-309 / Plate

Model description (SiPM)

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● Flat 40% quantum efficiency.○ f( ) is used since Slide 18

● Reflection 0%● SiPM now is a small black hole.

○ Stop and kills all particles.

y

z

Existing prototype

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Electron 2.23 MeV

● HBP plate○ 8*cm x 25*mm x 1.96*mm

○ Polished

● SiPM x4○ 0.1*mm x 1.*mm x 1.*mm○ No reflection○ Quantum efficiency 40%

● HBP material (0.5*mm) in front of SiPM

● Channel x4○ 79*mm x 0.5*mm x 1.*mm

○ Ground

● Gun (CH#2) counting from 0

z

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Photon generation processes (all photons in all volume)

Peak at:● ~2000 scintillation photons● ~60 Cherenkov photons

Even

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Even

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Gun (-3,5cm, 0.5mm, 0.2cm+plate_widthZ/2.)

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Photon generation (all photons in all volume)

We can setup scintillation profile more precisely.

Even

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at gunpoint

N photons in the SiPMs per event (ground channel)

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● Same behaviour as in the experiment.

● Does channel surface is really “ground”?

Gun (-3,5cm, 0.5mm, 0.2cm+plate_widthZ/2.)

Is problem in channel surface?

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Electron 2.23 MeV

● HBP plate○ 8*cm x 25*mm x 1.96*mm

○ Polished

● SiPM x4○ 0.1*mm x 1.*mm x 1.*mm○ No reflection○ Quantum efficiency 40%

● HBP material (0.5*mm) in front of SiPM

● Channel x4○ 79*mm x 0.5*mm x 1.*mm

○ Ground

No photons are escape.

● Gun (CH#2) counting from 0

Is problem in channel surface?

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Electron 2.23 MeV

● HBP plate○ 8*cm x 25*mm x 1.96*mm

○ Polished

● SiPM x4○ 0.1*mm x 1.*mm x 1.*mm○ No reflection○ Quantum efficiency 40%

● HBP material (0.5*mm) in front of SiPM

● Channel x4○ 79*mm x 0.5*mm x 1.*mm

○ Polished

That’s what we want!

● Gun (CH#2) counting from 0

Even

ts

at gunpoint

N photons in the SiPMs (polished channel)

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● Needs to take in account real SiPM quantum efficiency.

● We can tune the “roughness” of the channels surfaces.

Gun (-3,5cm, 0.5mm, 0.5cm+plate_widthZ/2.)

Per channel contribution

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● Highest contribution from the fiered channel (MCh_2).

● There are no photon generation in the support channels.

Even

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Even

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at gunpoint

“MCh_#” - tag for main channels

“SCh_#” - tag for support channels

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Per process contribution

● Cerenkov photons coming from the plate and EJ-309!

● Scintillation photons comes from the fiered channel.

Even

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ents

Even

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ents at gunpoint

Energy spectrum

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Energy spectrum mostly same for all SiPMs.

Here photon detection efficiency was flat and equal

to 40%.

Let's use correct one.

Energy spectrum as f( )

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Maximum of EJ-309 emission spectrum is in the region between 400-450 nm. So, there are no big changes

even for Cherenkov spectrum.

Even

tsN photons in the SiPMs (polished channel, fQE( ))

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● Real SiPM quantum efficiency doesn’t change distributions

a lot.● We can tune the “roughness”

of the channel's surface.

Let’s shoot between channels!

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Electron 2.23 MeV

● HBP plate○ 8*cm x 25*mm x 1.96*mm

○ Polished

● SiPM x4○ 0.1*mm x 1.*mm x 1.*mm○ No reflection○ Quantum efficiency 40%

● HBP material (0.5*mm) in front of SiPM

● Channel x4○ 79*mm x 0.5*mm x 1.*mm

○ Ground/Polished

● Gun (between CH#2 and CH#3) counting from 0

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Photon generation processes (all photons in all volume)

● Compare with Slide 9● Total ~= Cherenkov

Even

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Even

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Gun (-3,5cm, 1.mm, 0.2cm+plate_widthZ/2.)

N photons in the SiPMs

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Even

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Ground channel

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Polished channel

Gun (-3,5cm, 0.5mm, 0.2cm+plate_widthZ/2.), between MCh2 and MCh3

● Compare with Slide 11 and Slide 14

There was ideal gun...

What if we’ll set particle gun distance to the plate surface

from 0.2 cm to 2 cm?

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Photon generation processes (all photons in all volume)

● Higher probability to get event, where e- generates only cherenkov in the plate.

● Compare with Slide 9.

Even

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Even

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Gun (-3,5cm, 0.5mm, 2cm+plate_widthZ/2.)

N photons in the SiPMs

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Even

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Even

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Ground channel

Polished channel

Gun (-3,5cm, 0.5mm, 2cm+plate_widthZ/2.)

● Higher probability to have events, where e-

generates only cherenkov in the plate (passes near the scintillation channel).

● Compare with Slide 11 and Slide 14

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TODO list● Check effects from the aluminium collimator.

○ Set random E and angular e- distributions.■ Some examples for Sr90?

● Add additional volumes and parts:○ simple trigger under the plate (box of scintillator EJ-309) ○ simple aluminium boxes around for reflection simulation from the

supporting constructions and ect.● Paste plate over with black duct tape.● Something else?

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Back Up Slides

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Talks history● 11.11.16 - intro to the Geant4 toolkit and what we can do.

https://gitlab.cern.ch/microscint-experts/G4MicroScint29

EJ-309 channel solo in the air

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● Channel○ 8*cm x 0.5*mm x 1.*mm

○ Polished○ EJ-309 scintillator

● SiPM○ 0.1*mm x 1.*mm x 1.*mm○ No reflection○ Quantum efficiency 40%

Not centered (-0.01*mm shift)

y

z

● Gun (center of CH)○ Position (0,0,0.3*cm)○ Electron 2.23 MeV

EJ-309 channel solo in the air

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Even

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Even

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EJ-309 channel solo in the air

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EJ-309 channel solo in the airEv

ents