A Study of the Radiation Tolerance of CVD Diamond to 70 MeV Protons, Fast Neutrons and 200 MeV Pions
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-11-20 |
| Journal | Sensors |
| Authors | L. Bäni, Andreas V. Alexopoulos, M. Artuso, Felix Bachmair, M. Bartosik |
| Institutions | Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Institute for Theoretical and Experimental Physics |
| Citations | 13 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This study quantifies the radiation tolerance of Chemical Vapor Deposition (CVD) diamond, establishing its suitability for extreme radiation environments in high-energy physics and nuclear applications.
- Universal Damage Curve: A comprehensive universal damage curve was successfully derived, combining data from 70 MeV protons, fast neutrons, 200 MeV pions, and previous 24/800 MeV proton data. This curve allows engineers to predict the degradation of the mean drift path (λ) for diamond detectors under various irradiation conditions.
- Quantified Damage Constants: Fast reactor neutrons (energy > 0.1 MeV) were found to be the most damaging species, exhibiting a relative damage constant (κ) of 4.3 ± 0.4 compared to 24 GeV protons (κ=1.0).
- Proton Damage: 70 MeV protons showed a relative damage constant of 2.60 ± 0.29, significantly higher than 24 GeV protons, confirming the energy dependence of displacement damage.
- Superior Radiation Hardness: CVD diamond demonstrated greater than a factor of two better radiation tolerance than silicon for all tested proton and pion energies. Silicon is only comparable to diamond under fast neutron irradiation.
- Improved Uniformity: Irradiation was shown to improve the spatial uniformity of charge collection in polycrystalline CVD (pCVD) diamond, evidenced by a decrease in the FWHM/MP ratio of the signal spectrum as fluence increases.
- Model Validation: The first-order damage model (1/λ = 1/λ0 + kφ) accurately describes the degradation of charge collection distance across all tested particle types and fluences.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Damage Constant (Fast Neutrons) | 2.65 ± 0.13 (stat) ± 0.18 (syst) x 10-18 | cm2/(nµm) | pCVD diamond |
| Damage Constant (70 MeV Protons) | 1.62 ± 0.07 (stat) ± 0.16 (syst) x 10-18 | cm2/(pµm) | pCVD diamond |
| Damage Constant (200 MeV Pions) | 2.0 ± 0.2 (stat) ± 0.5 (syst) x 10-18 | cm2/(πµm) | Combined pCVD/scCVD |
| Relative Damage (Fast Neutrons, κ) | 4.3 ± 0.4 | Dimensionless | Relative to 24 GeV protons (κ=1.0) |
| Relative Damage (70 MeV Protons, κ) | 2.60 ± 0.29 | Dimensionless | Relative to 24 GeV protons (κ=1.0) |
| Relative Damage (200 MeV Pions, κ) | 3.2 ± 0.8 | Dimensionless | Relative to 24 GeV protons (κ=1.0) |
| Detector Strip Pitch | 50 | µm | Standard fabrication for pCVD and scCVD |
| Nominal Electric Field (E) | ±2 | V/µm | Used for charge collection distance (ccd) measurement |
| MIP Charge Generation | 36.0 ± 0.8 | e/µm | Electron-hole pairs created per micron in diamond |
| Readout Chip | IDE AS VA2.2 | N/A | 128-channel integrated circuit |
| Annealing Process | 400 °C for 4 min | N2 atmosphere | Post-metalization treatment |
Key Methodologies
Section titled “Key Methodologies”- Sample Preparation: High-purity polycrystalline (pCVD, ~500 µm thick) and single-crystalline (scCVD) diamond samples were used. Surfaces were cleaned via multi-step hot acid treatment followed by an oxygen plasma etch.
- Metallization and Annealing: Both sides were metalized (500 A Cr and 2000 A Au). A 50 µm pitch strip detector (25 µm strips, 25 µm gap) was fabricated on the readout side. Devices were annealed at 400 °C in N2.
- Initial Calibration: Unirradiated signal response (initial ccd) was measured using a calibrated 90Sr beta source setup and single pad detectors to determine the baseline charge collection efficiency.
- Irradiation Sources and Fluence:
- 70 MeV Protons: Irradiated at the CYRIC facility (Tohoku University). Fluence measured via aluminum foil activation (~10% uncertainty).
- Fast Neutrons: Irradiated in the JSI TRIGA nuclear reactor (energy > 0.1 MeV). Fluence measured via gold foil activation (~10% uncertainty).
- 200 MeV Pions: Irradiated at PSI, managed by CERN IRRAD. Fluence measured via aluminum foil activation (~20% uncertainty).
- Signal Measurement: After each irradiation step, the detectors were characterized in a 120 GeV hadron test beam at CERN. An eight-plane silicon strip telescope provided particle tracking with ~1.3 µm precision.
- Charge Collection Distance (ccd) Calculation: The average signal charge (qsignal) was converted to ccd using the constant 36 e/µm for a Minimum Ionizing Particle (MIP). The mean drift path (λ) was derived from ccd using the Hecht equation, assuming a hole-to-electron drift ratio (λh/λe) of 1.3 ± 0.8.
- Damage Constant Determination: The damage constant (k) was extracted by fitting the inverse mean drift path (1/λ) linearly against the irradiation fluence (φ) using the first-order damage model: 1/λ = 1/λ0 + kφ.
Commercial Applications
Section titled “Commercial Applications”The demonstrated radiation hardness and predictable degradation behavior of CVD diamond are critical for applications requiring extreme durability and reliability in high-flux environments.
- High-Luminosity Collider Upgrades (HL-LHC): Diamond is essential for beam condition monitors (BCMs) and precision tracking detectors, protecting sensitive silicon components and measuring luminosity under fluences exceeding 1016 particles/cm2.
- Fusion and Fission Reactors: Used as robust, high-temperature neutron and proton flux monitors within reactor cores or near plasma chambers where conventional electronics fail rapidly.
- Hadron Therapy and Medical Dosimetry: Precision monitoring of high-energy proton and pion beams used in cancer treatment, leveraging diamond’s tissue equivalence and stability.
- Space and Satellite Electronics: Deployment in satellite systems and deep-space probes for particle detection and radiation dosimetry, offering superior resistance to high-energy cosmic rays and solar protons compared to silicon.
- Radiation Hard Industrial Sensors: Development of sensors for industrial environments (e.g., nuclear waste processing, high-power accelerators) where long-term operational stability under intense radiation is mandatory.
View Original Abstract
We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 μm pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV), and a third group of samples with 200 MeV pions, in steps, to (8.8±0.9) × 1015 protons/cm2, (1.43±0.14) × 1016 neutrons/cm2, and (6.5±1.4) × 1014 pions/cm2, respectively. By observing the charge induced due to the separation of electron-hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be 1.62±0.07(stat)±0.16(syst)× 10−18 cm2/(p μm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65±0.13(stat)±0.18(syst)× 10−18 cm2/(n μm), and the damage constant for diamond irradiated with 200 MeV pions to be 2.0±0.2(stat)±0.5(syst)× 10−18 cm2/(π μm). The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2019 - A study of the radiation tolerance of poly-crystalline and single-crystalline CVD diamond to 800 MeV and 24 GeV protons [Crossref]