Latest Results on the Radiation Tolerance of Diamond Detectors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2019-11-04 |
| Journal | Proceedings of XXIX International Symposium on Lepton Photon Interactions at High Energies â PoS(LeptonPhoton2019) |
| Authors | Lukas Baeni, Andreas V. Alexopoulos, M. Artuso, Felix Bachmair, M. Bartosik |
| Institutions | Syracuse University, Istituto Nazionale di Fisica Nucleare, Sezione di Perugia |
| Analysis | Full AI Review Included |
Latest Results on the Radiation Tolerance of Diamond Detectors: Engineering Analysis and 6CCVD Material Solutions
Section titled âLatest Results on the Radiation Tolerance of Diamond Detectors: Engineering Analysis and 6CCVD Material Solutionsâ6CCVD Reference ID: POS-LP2019-079 Analysis Date: 2024-05-15 Source: PoS(LeptonPhoton2019)079 (RD42 Collaboration)
Executive Summary
Section titled âExecutive SummaryâThis paper validates MPCVD diamondâs superior radiation hardness and provides critical empirical data for its adoption in extreme high-energy physics (HEP) environments, such as the High Luminosity LHC (HL-LHC).
- Radiation Hardness Validation: Confirms MPCVD Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) as highly radiation-tolerant sensor materials, suitable for inner tracking layers requiring fluences exceeding $10^{16}$ particles/cm2.
- Universal Damage Curve Established: The RD42 collaboration successfully combined damage data from various particle species (protons at 24 GeV, 800 MeV, 70 MeV, and fast neutrons) into a single predictive âUniversal Damage Curve.â
- Quantified Damage Coefficients ($\kappa$): Provides empirical damage constants, showing fast reactor neutrons ($\kappa = 4.5 \pm 0.4$) cause the greatest radiation damage relative to 24 GeV protons ($\kappa = 1.0$).
- Fluence Resistance: Devices maintained signal response stability after extreme doses, including $8.8 \times 10^{15} \text{ p/cm}^{2}$ (70 MeV protons) and $1.3 \times 10^{16} \text{ n/cm}^{2}$ (fast neutrons, >100 keV).
- Detector Configuration: Testing utilized $50 \text{ ”m}$ pitch strip detectors, validating the efficacy of CVD diamond in micro-patterned electrode architectures crucial for high-resolution tracking.
- Fundamental Charge Generation: Confirms that a minimum ionizing particle (MIP) generates, on average, 36 electron-hole pairs per micron of diamond path length traversed.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data characterizes the material performance and experimental parameters critical for the development of high-radiation tolerant diamond detectors.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Tested Material Types | SCD and PCD | N/A | Chemical Vapor Deposition (CVD) Diamond |
| MIP Charge Generation | 36 | e-h pairs/”m | Average ionization charge yield in diamond |
| Strip Detector Pitch | 50 | ”m | Front-side electrode geometry |
| Operating Bias Field (E-Field) | 1 and 2 | V/”m | Typical fields used during signal testing |
| Test Beam Particle Type | Hadrons (Charged Particles) | N/A | Used for signal response characterization |
| Test Beam Energy/Momentum | 120 | GeV/c | Super Proton Synchrotron (SPS) test facility |
| Highest Proton Fluence (70 MeV) | $8.8 \times 10^{15}$ | p/cm2 | Cyclotron irradiation dose |
| Highest Neutron Dose (>100 keV) | $1.3 \times 10^{16}$ | n/cm2 | TRIGA reactor irradiation dose |
| Relative Damage Constant ($\kappa$) | 1.0 | N/A | 24 GeV Protons (Reference Standard) |
| Relative Damage Constant ($\kappa$) | $1.67 \pm 0.09$ | N/A | 800 MeV Protons |
| Relative Damage Constant ($\kappa$) | $2.48 \pm 0.25$ | N/A | 70 MeV Protons |
| Relative Damage Constant ($\kappa$) | $4.5 \pm 0.4$ | N/A | Fast Reactor Neutrons (>100 keV) |
Key Methodologies
Section titled âKey MethodologiesâThe radiation tolerance characterization involved a multi-stage process of sequential irradiation, precise detector fabrication, and high-energy beam testing.
-
Material Selection & Preparation:
- Both single-crystalline CVD (scCVD) and poly-crystalline CVD (pCVD) diamond devices were used to ensure the applicability of the findings across material grades.
-
Irradiation Stages:
- Samples were irradiated in steps using four primary species/energies:
- 24 GeV Protons (CERN IRRAD facility).
- 800 MeV Protons (LANSCe facility).
- 70 MeV Protons (CYRIC facility, up to $8.8 \times 10^{15} \text{ p/cm}^{2}$).
- Fast Reactor Neutrons (>100 keV) (JSI TRIGA reactor, up to $1.3 \times 10^{16} \text{ n/cm}^{2}$).
- Samples were irradiated in steps using four primary species/energies:
-
Detector Fabrication:
- Before and after each irradiation step, a $50 \text{ ”m}$ pitch strip detector pattern was fabricated.
- Front side: Strip pattern metalized and wire bonded to VA2.2 readout channels.
- Back side: Single metal pad electrode metalized (necessary for biasing).
-
Signal Characterization (Beam Test):
- Devices Under Test (DUTs) were tested in a secondary beam line at CERNâs Super Proton Synchrotron (SPS).
- Test particles were $120 \text{ GeV/c}$ charged hadrons (MIPs).
- Tracking information was provided by a beam telescope, achieving position precision of roughly $2 \text{ ”m}$.
-
Damage Derivation:
- The charge collection distance (ccd) was measured using the average signal response ($q^{\text{signal}}$).
- The radiation damage constant ($k$) was derived by fitting the inverse mean drift distance ($1/\lambda$) versus particle fluence ($\Phi$) to the damage model $1/\lambda = 1/\lambda_{0} + k\Phi$.
- Final damage constants ($\kappa$) were normalized to the 24 GeV proton results to create the universal curve parameters.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe findings confirm CVD diamond is essential for next-generation radiation-hard sensors. 6CCVD is uniquely positioned to supply the high-purity, custom-engineered diamond substrates required to replicate and advance this research.
Applicable Materials
Section titled âApplicable MaterialsâThe study successfully characterized both scCVD and pCVD diamond. 6CCVD offers materials tailored precisely for particle detection and sensor applications, ensuring high charge collection distance ($\lambda$) and low trap density ($\lambda_{0}$).
| Research Requirement | 6CCVD Material Solution | Key Benefit for Detection |
|---|---|---|
| Single-Crystal CVD (scCVD) | Optical Grade SCD (High Purity) | Maximum initial charge collection efficiency; lowest inherent trap density, achieving optimal $\lambda_{0}$. |
| Poly-Crystalline CVD (pCVD) | Electronic Grade PCD | Cost-effective for large-area detectors (up to 125mm); superior homogeneity over large wafers. |
| Specialized Requirements | Boron-Doped Diamond (BDD) | Available for conductive or semi-conductive electrode/sensor layers (e.g., Ohmic contacts, p-type layers). |
Customization Potential
Section titled âCustomization PotentialâThe construction of $50 \text{ ”m}$ pitch strip detectors requires exceptional dimensional control, high-quality surface preparation, and advanced metalizationâall core competencies of 6CCVD.
- Custom Dimensions and Thickness: The paper utilized various sample sizes and thicknesses (up to 500 ”m are common for sensors). 6CCVD provides custom diamond wafers up to 125mm (PCD) and precise thickness control for SCD and PCD ranging from $0.1 \text{ ”m}$ to $500 \text{ ”m}$.
- Ultra-High Polishing: High-resolution tracking and fine-pitch metalization demand ultra-smooth surfaces. 6CCVD guarantees Ra < 1nm for SCD and Ra < 5nm for inch-size PCD to ensure optimal lithography and low surface leakage current.
- Integrated Metalization: Sensor performance relies critically on the electrode interfaces. 6CCVD offers in-house custom metalization using robust adhesion and contact layers, including Ti/Pt/Au, W/Cu, and Pd stackups, crucial for reliable wire-bonding and long-term detector operation under high bias fields ($1 \text{ V/”m}$ to $2 \text{ V/”m}$ used in the study).
- Precision Patterning: We provide high-precision laser cutting and patterning services to define complex strip or pixel architectures, allowing engineers to implement the $50 \text{ ”m}$ pitch geometry or smaller feature sizes directly onto the substrate.
Engineering Support
Section titled âEngineering SupportâThe successful development of a universal damage curve simplifies material selection, but optimizing a detector for specific operational environments (e.g., calculating equivalent 24 GeV proton fluence based on the $\kappa$ values) requires expert knowledge.
6CCVDâs in-house PhD material scientists and technical engineers are available to assist clients with:
- Material Selection: Guiding researchers to the optimal SCD or PCD grade based on required initial charge collection distance ($\lambda_{0}$) and operational fluence ($\Phi$).
- Sensor Design Consultation: Providing advice on substrate thickness, metal stack composition, and polishing requirements for high-energy physics (HEP) and radiation monitoring projects.
- Equivalent Fluence Prediction: Utilizing the universal damage curve parameters published by the RD42 collaboration to predict material lifetime for similar radiation tolerant detector projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We have measured the radiation tolerance of chemical vapor deposition (CVD) diamond against protons and neutrons. The relative radiation damage constant of 24 GeV protons, 800 MeV protons, 70 MeV protons, and fast reactor neutrons is presented. The results are used to combine the measured data into a universal damage curve for diamond material.