Neutron beam test simulation study for CERN+US-Japan prototype 3DST - - PowerPoint PPT Presentation

Neutron beam test simulation study for CERN+US-Japan prototype

3DST weekly meeting Neha Dokania, Guang Yang (SBU)

• Mar. 15, 2019

Neutron Beam Test at LANL

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• Proposed neutron beam test at Los Alamos National Lab (LANL) using the

neutron beam (Los Alamos Neutron Science Centre facility) to be done in 2019 for the CERN + US-Japan Prototypes

• Characterize the neutron response of the scintillator tracker : eg. neutron

tagging efficiency, event topologies etc.

Sub-ns micro pulses 1.8 μs apart within a 625 μs long macro pulse Repetition rate: up to 100 Hz Time Structure of the neutron beam at LANL

Simulation Studies

• In the neutron beam test proposal
• Neutron Tagging efficiency for different energy deposit

thresholds

• Deposited Neutron Energy Spectra for incident neutron

kinetic energy ranges

• Angular distribution of outgoing particles

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Neutron Beam direction

Simulation Details

• Neutron beam generated in the neutron kinetic energy range 0 - 800 MeV

(power-law) and propagated through different prototype configurations using Geant4

Configuration 1

• Neutron beam directed from the US-Japan prototype side
• Beam width 1 cm
• Dimensions of CERN prototype : 24 x 8 x 48 cm3 (W x H x L)

and US-Japan prototype : 8 x 8 x 32 cm3

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Geometry of the prototype configuration 1

Multiplicity

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• For 105 incident neutrons
• 35% of neutrons hit two scintillator cubes
• Maximum cube multiplicity is 12

Cube Multiplicity = No. of scintillator cubes getting hit in an event (Without any energy threshold cut for now )

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Multiplicity vs Neutron Kinetic Energy

• Low Neutron Kinetic energy contributes more to hits.
• Neutron beam had power-law distribution – higher statistics sample will be

generated to get sufficient statistics for the high energy bins.

Incident Neutron Spectra

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Multiplicity vs Energy Deposit

• Higher Energy deposit has higher multiplicity
• Higher statistics sample will be generated to get sufficient statistics

Neutron Beam direction

Configuration - 2

• Neutron beam directed from the US-Japan prototype side
• Beam width 1 cm
• Dimensions of CERN segment : 24 x 8 x 48 cm3 (W x H x L)

and US-Japan segment : 8 x 8 x 32 cm3

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Geometry of the prototype configuration 2

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Multiplicity

• About 10% more events with multiplicity 1 and 2 for neutron beam incident

from the US-Japan prototype side

• For higher multiplicities (>2), more events are with configuration the beam

from CERN prototype side

Summary

• Neutron response to CERN+US-Japan Prototype studied for

neutron beam test at LANL

• Multiplicity for no. of scintillator cubes was studied for

incident neutron kinetic energy as well as deposited energy in the prototypes

• Neutron double tagging studies is under progress.

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Incident Neutron Spectrum

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Back-Up

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Los Alamos Neutron Science Center WNR facility provides a high flux neutron beam (scaled down by 3x105) with a broad energy spectrum similar to the cosmic-ray induced neutron spectrum at high altitude n/cm2/sec/MeV

Neutron Kinetic energy with zero multiplicity

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Incident neutron energy spectrum

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For an incident uniform distribution Neutron Kinetic energy

Neutron Kinetic energy having zero multiplicity

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For a uniform distribution Neutron Kinetic energy

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Neutron Tagging Efficiency = Detected neutrons / Detectable neutrons

• For 105 incident neutrons in a uniform distribution
• Energy deposit per event > Threshold value [0.1, 0.5, 1.0, 1.5 MeV]
• Detectable neutrons = 76386

[neutrons which deposit any amount of energy ,i.e. no threshold cut]

• Neutron tagging efficiency is similar to configuration 1.

Energy deposited

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With the threshold cut of energy deposited per event >1.5MeV The spectra of energy deposits for four different neutron kinetic energy ranges

Angular distribution

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With the threshold cut of energy deposited per event >1.5MeV