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 1. College of Nuclear Science and Technology, Lanzhou University, Lanzhou, China; 2. IRFU-CEA, Saclay, France; 3. Department of Nuclear Engineering, University of Tennessee, Knoxville, USA;
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Test of a Micromegas TPC for imaging by fast neutrons
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 - PowerPoint PPT Presentation
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Test of a Micromegas TPC
for imaging by fast neutrons
Test of a Micromegas TPC
for imaging by fast neutrons
Luxing An1, David Attié2, Yonghao Chen1, Paul Colas2, M. Riallot2, Huaya Shen1, Wenxin Wang1,2, Xiaodong Wang1, Chunhui Zhang2,
Xiaodong Zhang1,3, Yi Zhang1
1. College of Nuclear Science and Technology, Lanzhou University, Lanzhou, China;2. IRFU-CEA, Saclay, France;3. Department of Nuclear Engineering, University of Tennessee, Knoxville, USA;
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Neutron cross-sections are higher for light elements: see hydrocarbons through metals or glass.
Applications to rocket engines, etc…
Motivation
3
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 aFront-End Mezzanine (FEM)
• Detector layout: 1728 (48×36) pads of 1.75 mm×1.50 mm
+ bulk Micromegas• Elastic scattering on hydrogen n
p+ masks (PE)
PCB Micromegas
n
p
Aluminized polyethylene 1 mm
between 2 layers (0.5 µm) of Al
57.4 mm
88.6
mm
Cosmics
(x, y, t)
II. Other Micromegas TPC application: neutron imaging
6 Simulation for converter efficiency Neutronproton 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. Other Micromegas TPC application: neutron imaging
7 Reconstruct track
Garfield
Avalanches
Drift lines from
primary ionization
e-
Proton track
\\
II. Other Micromegas TPC application: neutron imaging
8
Experiment and Simulation Results-- n-g discrimination
Two Methods to discriminate the neutron and gamma events with Am-Be neutron source:
1. Time2. Energy
With Convertor
W/O Convertor
75 keV Threshold
9 Test with a 241Am-9Be neutron source
Letters “CEA” or “LZU” • 8 cm thickness • 4-4.5mm width
2.5mm
3 mm
3.5mm
4 mm
II. Other Micromegas TPC application: neutron imaging
10 Neutron imaging
Integrating the ADC of all events in one pad.
Reconstructed using the time information.
II. Other Micromegas TPC application: neutron imaging
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A new detector has been used to detect neutrons: a ‘flat’ TPC with O(mm) pixels and with a CH2 converter.
The time measurement along the proton track allows determination of the conversion point and improves image resolution.