Burst eddy current testing with diamond magnetometry
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-02-21 |
| Journal | Applied Physics Letters |
| Authors | Chang Xu, Jixing Zhang, Heng Yuan, Guodong Bian, Pengcheng Fan |
| Institutions | Beihang University |
| Citations | 7 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Diamond NV Magnetometry for Burst Eddy Current Testing
Section titled âTechnical Documentation & Analysis: Diamond NV Magnetometry for Burst Eddy Current TestingâThis document analyzes the research paper âBurst Eddy Current Testing with a Diamond Magnetometryâ and outlines how 6CCVDâs specialized MPCVD diamond materials and fabrication services can support the replication, optimization, and commercialization of this advanced quantum sensing technology.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a highly sensitive, non-destructive testing (NDT) technique using Nitrogen Vacancy (NV) centers in diamond for Burst Eddy Current (BEC) magnetometry.
- Superior Sensitivity: The proposed Hahn Echo (HE) based NV magnetometer achieved a magnetic sensitivity of 4.3 nT/âHz and a volume-normalized sensitivity of 3.6 pT/âHz·mm-3.
- Performance Advantage: This sensitivity is up to 5 to 10 times better than existing continuous-wave (CW) NV eddy current methods under comparable conditions.
- High Resolution NDT: The prototype achieved a minimum detectable sample size smaller than 300 ”m and a measurement accuracy of 9.85 ”m, enabling high-resolution imaging of conductive materials and layered structures.
- Thermal Mitigation: The use of burst excitation avoids adverse eddy current thermal effects, significantly expanding the application scope to temperature-sensitive materials, microelectronics, and biological samples.
- Material Requirement: The core technology relies on high-quality Single Crystal Diamond (SCD) with precisely controlled nitrogen doping (50 ppm N) and post-processing (irradiation/annealing) to maximize NV center yield and decoherence time (T2).
- 6CCVD Value Proposition: 6CCVD specializes in providing the necessary High-Purity SCD substrates, custom doping profiles, and advanced polishing (Ra < 1nm) required to optimize T2 coherence and enhance fluorescence collection efficiency for next-generation quantum sensors.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table extracts the key performance metrics and material parameters achieved in the study:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Magnetic Sensitivity (HE Scheme) | 4.3 | nT/âHz | Achieved AC sensitivity |
| Volume-Normalized Sensitivity | 3.6 | pT/âHz·mm-3 | Detection volume ~7x10-7 mm3 |
| Operating Frequency Band | 100 kHz to 3 | MHz | Wide bandwidth operation |
| Minimum Detectable Sample Size | < 300 | ”m | Achieved by the BEC prototype |
| Measurement Accuracy | 9.85 | ”m | Spatial resolution achieved |
| Initial Nitrogen Impurity | 50 | ppm | Doping level used during CVD growth |
| Electron Irradiation Dose | 1x1018 | e/cm2 | Used for NV creation |
| Annealing Temperature | 800 | °C | Post-irradiation processing |
| Decoherence Time (T2) | â 6 | ”s | Limiting factor for low-frequency performance |
| Optimal Working Frequency | 300 | kHz | Frequency for optimal scale factor |
Key Methodologies
Section titled âKey MethodologiesâThe successful implementation of the NV-BEC testing scheme relies on precise material engineering and advanced quantum control sequences:
- CVD Diamond Fabrication: Single Crystal Diamond (SCD) was grown using the Chemical Vapor Deposition (CVD) method, incorporating a controlled Nitrogen impurity level of 50 ppm.
- NV Center Generation: The material underwent 10 MeV electron irradiation (1x1018 e/cm2) followed by high-temperature annealing (800 °C for 2 hours) to mobilize vacancies and form NV centers (estimated density ~3 ppm).
- Confocal Magnetometry Setup: A confocal optical path was used for spin polarization and fluorescence readout, coupled with a ring-shaped antenna for microwave delivery.
- Burst Excitation: A single-cycle sinusoidal magnetic field (burst) was generated by a 3-mm diameter, 18-turn coil, applied at frequencies up to 3 MHz.
- Quantum Sensing Sequence: The Hahn Echo (HE) dynamical decoupling sequence was employed, consisting of laser pulses for polarization/readout and microwave pulses (Ï/2, Ï, Ï/2) for enhanced AC magnetic field sensitivity.
- Imaging and Analysis: Specimens (Copper, Lead) were scanned point-by-point using a motorized translation stage, and the resulting fluorescence signal was analyzed to determine eddy current density and material edges.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the critical need for high-quality, customized diamond substrates to maximize NV center performance, particularly by improving the decoherence time (T2) and fluorescence collection efficiency. 6CCVD is uniquely positioned to supply the materials and engineering services required to advance this technology.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate and extend the high-sensitivity results achieved in this paper, researchers require diamond optimized for quantum sensing:
- Optical Grade Single Crystal Diamond (SCD): We provide high-purity SCD with extremely low strain, essential for achieving long T2 coherence times (significantly exceeding the 6 ”s reported here) and improving low-frequency sensitivity.
- Controlled Nitrogen Doping: 6CCVD offers SCD with precise, controlled nitrogen incorporation (from sub-ppb to 100 ppm) to optimize the NV yield and density (e.g., targeting the ~3 ppm density used in this study, or higher/lower concentrations for specific applications).
- Boron-Doped Diamond (BDD) for Integrated Electronics: For future integrated or on-chip NV magnetometry (as referenced in the paper), 6CCVD can supply highly conductive BDD substrates or films, which can be used as integrated microwave transmission lines or ground planes.
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs advanced fabrication capabilities directly address the needs for optimized sensor geometry and integration:
| Research Requirement | 6CCVD Customization Service | Technical Advantage |
|---|---|---|
| Improved Optical Collection | Ultra-low roughness polishing (Ra < 1 nm for SCD) | Maximizes fluorescence collection efficiency (a key factor cited for sensitivity improvement). |
| Integrated Microwave Antenna | Custom Metalization (Ti/Pt/Au, W, Cu, Pd) | Enables direct fabrication of ring-shaped microwave antennas or contact pads onto the diamond surface for highly localized excitation. |
| Custom Sensor Geometry | Plates/wafers up to 125 mm; Custom Thickness (0.1 ”m - 500 ”m) | Provides large-area substrates for multi-sensor arrays or custom-cut geometries for integration into specialized NDT probes. |
| Enhanced Spatial Resolution | Precision Laser Cutting and Shaping | Allows for the creation of small, high-aspect-ratio diamond tips or probes necessary for sub-mm spatial resolution. |
Engineering Support
Section titled âEngineering SupportâThe optimization of NV magnetometers involves complex material science, including post-growth processing (irradiation and annealing).
- NV Center Optimization Consultation: 6CCVDâs in-house PhD team offers expert consultation on material selection, controlled N-doping levels, and post-processing protocols (including advice on electron irradiation dose and annealing temperatures) specifically tailored for NV-center magnetometry and Non-Destructive Testing (NDT) projects.
- Global Supply Chain: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-value diamond materials directly to your research facility.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
In this work, a burst eddy current testing technique based on the employment of a diamond nitrogen vacancy (NV) center magnetometer with the Hahn echo (HE) sequence is demonstrated. With the confocal experiment apparatus, the HE-based NV magnetometer attains a magnetic sensitivity of 4.3 nT/Hz and a volume-normalized sensitivity of 3.6 pT/Hz mmâ3, which are âŒfive times better than the already existing method under the same conditions. Based on the proposed magnetometer configuration, a burst eddy current testing prototype achieves a minimum detectable sample smaller than 300 ÎŒm and a spatial resolution of 470 ÎŒm, which is employed to image different metallic specimens and detect layered internal structures. Since this prototype comprises remarkable high sensitivity, it exhibits various potential applications in the fields of security screening and quality control. Moreover, its biocompatibility and promising nanoscale resolution pave the way for electromagnetic testing in the fields of biomaterials.