Semiconductor Detector Study for Detecting Fusion Neutrons using Geant4 Simulations
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-05-05 |
| Journal | HNPS Advances in Nuclear Physics |
| Authors | K. Kaperoni, Î. Diakaki, M. Kokkoris, M. Axiotis, Anastasia Ziagkova |
| Institutions | National Technical University of Athens, National Centre of Scientific Research âDemokritosâ |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: MPCVD Diamond for Fusion Neutron Detection
Section titled âTechnical Documentation & Analysis: MPCVD Diamond for Fusion Neutron DetectionâExecutive Summary
Section titled âExecutive SummaryâThis research validates the critical role of diamond (C) and silicon carbide (SiC) semiconductor materials for neutron detection in extreme environments, specifically targeting the 2.45 MeV fusion neutrons produced during the D-D phase of the ITER reactor.
- Material Superiority: Diamond (C) and SiC detectors demonstrated significantly better performance than Silicon (Si), primarily due to their high bandgap and low atomic number (Z), which minimizes interaction probability with contaminating gamma-rays.
- Gamma Rejection: Diamond exhibits a clear energy deposition threshold around 0.4 MeV, allowing for effective discrimination between neutron signals and high-energy gamma-ray contamination (500 keV, 1 MeV, 2 MeV).
- Extreme Environment Resilience: The study confirms that materials must withstand ITER conditions, including high neutron fluxes (up to 1014 n/cm2) and high temperatures (operational 70°C-100°C, baking up to 340°C). MPCVD diamond is ideally suited for this radiation-hardened requirement.
- Detector Geometry: Simulations focused on a standard thin-film geometry (4 mm x 4 mm x 50 ”m), a dimension easily achievable and customizable using 6CCVDâs MPCVD growth and processing capabilities.
- Methodological Validation: GEANT4 simulations successfully utilized biasing techniques to achieve high statistical accuracy, confirming the feasibility of modeling complex nuclear interactions in thin diamond films.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the simulation parameters and environmental requirements detailed in the study:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Neutron Energy | 2.45 | MeV | D-D Fusion Neutrons |
| Detector Dimensions (C, Si, SiC) | 4 x 4 x 50 | mm x mm x ”m | Sensor active volume |
| Diamond/SiC Gamma Threshold | ~0.4 | MeV | Minimum energy deposition for clear neutron signal discrimination |
| Maximum Neutron Flux (D-T) | 1014 | n/cm2 | ITER operational environment (14 MeV neutrons) |
| ITER Operating Temperature | 70 to 100 | °C | Vacuum vessel and port plug locations |
| ITER Baking Temperature | 200 to 340 | °C | Shutdown periods (Tritium removal) |
| Proton Beam Energy (Input) | 3.805 | MeV | Used for 3H(p,n) reaction |
| Diamond Biasing Factor | 100 | N/A | Optimized factor for neutron detection simulation |
| Si/SiC Biasing Factor | 2 | N/A | Optimized factor for neutron detection simulation |
Key Methodologies
Section titled âKey MethodologiesâThe study relied on detailed GEANT4 simulations, incorporating realistic experimental setup parameters to model the neutron source and detector response:
- Detector Geometry Construction: Solid volume detectors (C, Si, SiC) were modeled with precise dimensions (4 mm x 4 mm x 50 ”m).
- Physics List Selection: The QGSP-BIC physics list was used, focusing on accurate modeling of hadronic elastic, inelastic, and capture processes relevant to neutron interactions.
- Neutron Source Generation: A quasi-monoenergetic 2.45 MeV neutron beam was simulated, produced via the 3H(p,n) reaction using a solid TiT target.
- Target Specifications: The TiT target was modeled with a density of 3.75 g/cm3, a thickness of 0.00057 cm (5.7 ”m), and a composition of 42.8% Tritium and 57.1% Titanium.
- Biasing Implementation: To achieve high statistics despite the low cross section, the mean free interaction length (λ) was reduced by multiplying the macroscopic cross section (Σt) with a biasing factor.
- Factor Optimization: Extensive testing determined the optimal biasing factors to minimize deviation from the unbiased simulation: 100 for Carbon (C) and 2 for Silicon (Si) and Silicon Carbide (SiC).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD specializes in the production of high-purity MPCVD diamond materials essential for replicating and advancing this critical fusion research. Our capabilities directly address the material, dimension, and processing requirements identified in this study.
Applicable Materials
Section titled âApplicable Materialsâ| Research Requirement | 6CCVD Material Recommendation | Technical Justification |
|---|---|---|
| High Purity Diamond (C) | Optical Grade Single Crystal Diamond (SCD) | SCD provides the highest purity and crystalline quality, maximizing charge carrier mobility and lifetime, which is essential for achieving the high energy resolution and irradiation resistance required for ITER diagnostics. |
| Large Area/Array Potential | Polycrystalline Diamond (PCD) | For future development of large-area detector arrays (up to 125mm), PCD offers a cost-effective, radiation-hard alternative, maintaining superior thermal conductivity compared to Si or SiC. |
| Specialized Sensing/Thermal | Boron-Doped Diamond (BDD) | Can be utilized for specialized thermal management or as a conductive electrode layer in complex detector architectures. |
Customization Potential
Section titled âCustomization PotentialâThe study utilized a specific thin-film geometry (4 mm x 4 mm x 50 ”m). 6CCVDâs advanced MPCVD growth and post-processing capabilities ensure precise replication and customization of these critical parameters:
- Thickness Control: We offer SCD and PCD wafers with thicknesses ranging from 0.1 ”m up to 500 ”m, allowing for exact matching of the 50 ”m sensor thickness used in the simulation.
- Custom Dimensions: While the study used small 4 mm x 4 mm samples, 6CCVD can provide custom plates/wafers up to 125 mm (PCD) and offers precision laser cutting services to achieve any required geometry for detector integration.
- Surface Finish: Achieving high energy resolution in thin films requires minimal surface defects. Our SCD wafers are polished to an ultra-smooth finish (Ra < 1 nm), significantly improving charge collection efficiency.
- Integrated Metalization: The future validation phase requires developing realistic detector geometry, including metal contacts. 6CCVD offers in-house metalization services, including deposition of Ti, Pt, Au, Pd, W, and Cu, enabling the creation of robust electrode structures capable of surviving high-temperature baking cycles (up to 340°C).
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team provides expert consultation on material selection and optimization for extreme environment applications. We can assist researchers in:
- Material Selection: Determining the optimal diamond grade (SCD vs. PCD) and thickness for specific neutron energy ranges (e.g., 2.45 MeV vs. 14 MeV D-T neutrons).
- Detector Design: Advising on metalization schemes (e.g., Ti/Pt/Au) and surface preparation to maximize detector efficiency and long-term stability in fusion environments.
- Replication and Extension: Supporting projects aimed at replicating the NCSR âDemokritosâ experimental setup or extending the research to 14 MeV neutron detection.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Accurate neutron flux measurements in fusion reactors are essential, in order to determine the feasibility and progress of the reaction as well as for safety issues. Semiconductor neutron detectors exhibit promising characteristics for operation in the extreme environmental conditions of fusion reactors. Silicon, Diamond and Silicon Carbide are the most studied and anticipated materials for constructing detectors with high efficiency and irradiation resistance. The ITER fusion reactor is expected to run D-D plasma measurements in the near future, so the detection of 2.45 MeV neutrons with appropriate detectors is of great and immediate importance. In the present work the study of 2.45 MeV neutrons interactions with a silicon, diamond and silicon carbide detector was made, using GEANT4 [1] simulations, in order to compare their response. An experimental study will follow at the neutron production facility of the TANDEM accelerator of the I.N.P.P. of the NCSR âDemokritosâ, with detectors provided by CIVIDEC Instrumentation GmbH, so the geometry of the simulations was built accordingly. A quasi-monoenergetic neutron beam of 2.45 MeV was produced through 3H(p,n) reactions in a TiT target. Due to the low cross section of the reaction, biasing techniques were implemented in the simulation to increase the counting rate and thus producing realistic results. These biasing techniques were studied, with various tests and the parameters affecting the choice of the biasing factor are shown and discussed.