Test of a micromegas tpc for imaging by fast neutrons
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Test of a Micromegas TPC for imaging by fast neutrons. Luxing An 1 , David Attié 2 , Yonghao Chen 1 , Paul Colas 2 , M. Riallot 2 , Huaya Shen 1 , Wenxin Wang 1,2 , Xiaodong Wang 1 , Chunhui Zhang 2 , Xiaodong Zhang 1,3 , Yi Zhang 1

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Test of a Micromegas TPC for imaging by fast neutrons

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Test of a micromegas tpc for imaging by fast neutrons

Test of a Micromegas TPC for imaging by fast neutrons

LuxingAn1, David Attié2, Yonghao Chen1, Paul Colas2, M. Riallot2,

Huaya Shen1, WenxinWang1,2, Xiaodong Wang1, Chunhui Zhang2, Xiaodong Zhang1,3, Yi Zhang1

College of Nuclear Science and Technology, Lanzhou University, Lanzhou, China;

IRFU-CEA, Saclay, France;

Department of Nuclear Engineering, University of Tennessee, Knoxville, USA;


Motivation

Motivation

  • Neutron cross-sections are higher for light elements: seehydrocarbonsthroughmetals or glass.

  • Applications to rocket engines, etc…


T2k tpc electronics

T2K TPC electronics

  • Electronics designed in CEA/Irfu for the T2K TPC

  • AFTER-based electronics (72 channels/chip):

    • low-noise (700 e-) pre-amplifier-shaper

    • 100 ns to 2 µs tunable peaking time

    • full wave sampling by SCA

    • frequency tunable from 1 to 100 MHz (most data at 50 MHz)

    • 12 bit ADC (rms pedestals 4 to 6 channels)

    • zero-suppression capability

  • 6 Front-End Cards (FEC) readout by a

    Front-End Mezzanine (FEM)

  • 4 AFTER chips per FEC

  • Spark protection

FEC with 4 AFTER chips


Detector electronics setup

Detector + electronics setup

Window for x-rays source

Shielding

FEC

Trigger from

the mesh signal

FEM


Micromegas tpc for neutron imaging

Micromegas TPC for neutron imaging

  • Detector layout: 1728 (48×36) pads of 1.75 mm×1.50 mm

+ bulk Micromegas

  • Elastic scattering on hydrogen n  p

+ masks (PE)

PE

Aluminized polyethylene 1 mm

between 2 layers (0.5 µm) of Al

n

HVdrift

Edrift ~ 160 V/cm

15 mm

Gas: Argon + 5% Isobutane

128 µm

HVmesh

p

Eamp ~ 23 kV/cm

57.4 mm

88.6 mm

(x, y, t)

PCB

Cosmics

Micromegas

II. OtherMicromegas TPC application: neutron imaging


Simulation for converter efficiency

Simulation for converter efficiency

  • Neutronproton recoiling efficiency in a polyethylene [C2H4]n layer coming from 241Am-9Be source

Incident neutron spectrum

According to ISO 8529(*)

* INTERNATIONAL STANDARD ISO 8529. Reference neutron radiations – Part 1: Characteristic and methods of productions. International Standard ISO 8529-1 (2001).

II. OtherMicromegas TPC application: neutron imaging


Reconstruct track

Reconstruct track

Drift lines from primary ionization e-

Garfield

\\

Proton track

Avalanches

II. OtherMicromegas TPC application: neutron imaging


Experiment and simulation results n g discrimination

Experiment and Simulation Results-- n-gdiscrimination

Two Methods to discriminate

the neutron and gamma events with Am-Be neutron source:

Time

Energy

With Convertor

W/O Convertor

75 keV Threshold


Test with a 241 am 9 be neutron source

Test with a 241Am-9Be neutron source

4 mm

3.5mm

3mm

2.5mm

  • Letters “CEA” or “LZU”

  • 8 cm thickness

  • 4-4.5mm width

II. OtherMicromegas TPC application: neutron imaging


Neutron imaging

Neutron imaging

Reconstructed using the time information.

Integrating the ADC of all events in one pad.

II. OtherMicromegas TPC application: neutron imaging


Conclusion

Conclusion

  • A new detector has been used to detect neutrons: a ‘flat’ TPC with O(mm) pixels and with a CH2 converter.

  • The time measurementalong the proton trackallowsdetermination of the conversion point and improves image resolution.


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