Skip to content
6CCVD Research

Transverse magnetic field effects on diamond quantum sensor for EV battery monitor

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-09-03
JournalFrontiers in Quantum Science and Technology
AuthorsYuji Hatano, Junya Tanigawa, Akimichi Nakazono, T. Sekiguchi, Yuta Kainuma
InstitutionsYazaki (Japan), National Institutes for Quantum Science and Technology
Citations2
AnalysisFull AI Review Included

Technical Documentation & Analysis: Diamond Quantum Sensors for EV Battery Monitoring

Section titled “Technical Documentation & Analysis: Diamond Quantum Sensors for EV Battery Monitoring”

Executive Summary

Section titled “Executive Summary”

This documentation analyzes the research demonstrating the use of Nitrogen-Vacancy (NV) center diamond quantum sensors for high-precision, wide dynamic range monitoring of Electric Vehicle (EV) battery currents (up to ±1,000 A). The core achievement is the successful compensation of transverse magnetic field effects, crucial for maintaining accuracy in high-current environments.

  • Core Achievement: Demonstrated accurate simultaneous temperature and magnetic field measurement using (111) SCD NV-sensors in a high-current EV busbar application.
  • Performance Metrics: Achieved current linearity error of less than ±0.3% across the 20 A to 1,000 A range after compensation, meeting the accuracy specifications of the current source.
  • Dynamic Range & Precision: Prototype achieved 10 mA accuracy over a measurable range of several hundred amperes, significantly improving upon conventional 1 A sensors and potentially increasing EV cruising mileage by 10%.
  • Key Challenge Solved: Quantified and compensated for misalignment (up to ±1°) between the NV-axis and the static/current magnetic fields, which otherwise causes resonance frequency midpoint shifts opposite to temperature changes.
  • Material Requirement: The experiment relied on high-quality, irradiated, and annealed diamond crystal (HPHT Ib, 2 x 2 x 1 mmÂł) optimized for NV ensemble creation.
  • 6CCVD Value Proposition: 6CCVD provides the necessary high-purity, custom-dimensioned Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) substrates, along with expert post-processing (irradiation/annealing) and metalization services, required to replicate and scale this advanced quantum sensing technology.

Technical Specifications

Section titled “Technical Specifications”

The following hard data points were extracted from the research paper detailing the sensor material, performance, and operating conditions.

ParameterValueUnitContext
Diamond Material TypeHPHT Type Ib (111)CrystalStarting material for NV creation
Diamond Dimensions2 x 2 x 1mmÂłSensor crystal size
Nitrogen Concentration (P1)100ppmInitial P1 concentration
Irradiation Dose3 x 1018cm-22 MeV electron beam
Annealing Temperature1,000°CAnnealed for 2 h in vacuum
Estimated NV Concentration5-6ppmResulting NV ensemble density
Busbar Current Range (IB)±1,000AMaximum current tested (Bipolar)
Current Step Size20AApplied in 2 s intervals
Static Magnetic Field (B0)17mTProvided by external magnet
Misalignment Accuracy±1°Achieved estimation accuracy
Linearity Error (Compensated)< ±0.3%Achieved in 20-1,000 A range
Operating Temperature Range-40 to 85°CVerified range for linearity/fluctuation
Sensor Accuracy Goal10mATarget accuracy for EV monitoring

Key Methodologies

Section titled “Key Methodologies”

The experiment focused on differential detection using two diamond sensors (A and B) to cancel common-mode noise and utilized advanced microwave techniques to track resonance frequency shifts.

  1. Material Preparation:
    • High-pressure high-temperature (HPHT) type Ib diamond (111) crystal was used.
    • Crystals were irradiated with a 2 MeV electron beam (3 x 1018 cm-2 dose).
    • Crystals were subsequently annealed at 1,000 °C in vacuum to mobilize vacancies and form NV centers.
  2. Sensor Head Assembly:
    • The diamond sensor (2 x 2 mmÂČ) was adhered to the top of a multimode fiber (400 ”m core diameter).
    • A microwave guide surrounded the diamond sensor, applying a microwave magnetic field perpendicular to the [111] NV-axis.
    • The sensor holder (PEEK) was attached to the 25 mm x 12 mm busbar, with a static magnetic field (B0 = 17 mT) applied.
  3. Differential Detection:
    • A pair of sensor holders (A and B) were placed on the lower and upper sides of the busbar.
    • The circuit traced the resonance frequency difference (RAH - RAL and RBH - RBL) for differential detection, cancelling external magnetic field noise as common mode.
  4. Resonance Tracking:
    • A lock-in amplifier fed back 0° and 90° quadrature outputs to FM modulation terminals of two microwave oscillators. This ensured the microwave frequencies continuously followed the low- and high-frequency-side resonance frequencies (RL and RH).
  5. Transverse Field Compensation:
    • The resonance frequency midpoint change (Δ(RL + RH)/2) was analyzed under bipolar current (±1,000 A).
    • Theoretical models incorporating misalignment angles (Ξ and φ) between the NV-axis and the static/current magnetic fields were used to estimate misalignment with ±1° accuracy.
    • The estimated misalignment was used to compensate for the transverse magnetic field effects, improving both temperature consistency and linearity.

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

6CCVD is uniquely positioned to supply the advanced diamond materials and customization services necessary to replicate, optimize, and scale this high-precision quantum sensing technology for EV and industrial applications.

Applicable Materials

Section titled “Applicable Materials”

To achieve the high sensitivity and wide dynamic range demonstrated in this research, high-quality SCD is essential for controlled NV creation and optimal spin coherence.

6CCVD Material RecommendationSpecification & Relevance to ResearchCustomization Potential
Optical Grade SCD (111)Required for high-fidelity NV-center creation via post-processing (irradiation/annealing). Our MPCVD SCD offers superior purity and lower strain compared to HPHT, leading to potentially longer T2 coherence times and enhanced sensitivity.Custom [111] orientation wafers up to 10 x 10 mm, or larger custom sizes.
Nitrogen-Doped SCDFor researchers seeking in-situ NV creation, 6CCVD offers controlled nitrogen doping during MPCVD growth, allowing for precise NV ensemble density (5-10 ppm range) without relying solely on post-processing.Precise control over N concentration (ppm level) and thickness (0.1 ”m to 500 ”m).
Custom SubstratesThe paper used 2 x 2 x 1 mmÂł crystals. 6CCVD can supply custom-cut plates or wafers to match specific sensor head geometries (e.g., 2 x 2 mmÂČ surface area, 1 mm thickness).Custom laser cutting and dicing services available for precise dimensional requirements.

Customization Potential

Section titled “Customization Potential”

The complexity of the sensor head (Figure 2) requires precise integration of the diamond crystal, fiber, and microwave guide. 6CCVD supports this integration through specialized engineering services:

  • Custom Dimensions and Orientation: We provide SCD plates up to 10 x 10 mm and PCD wafers up to 125 mm, cut to specific thicknesses (0.1 ”m to 500 ”m) and orientations (e.g., [111] for optimal NV alignment) required for differential detection setups.
  • Advanced Polishing: Achieving high optical coupling efficiency is critical. 6CCVD guarantees ultra-low surface roughness (Ra < 1 nm for SCD) on the active surface adhered to the fiber, minimizing scattering losses.
  • Metalization Services: While the paper focused on the diamond sensor itself, future integration may require contact pads or microwave structures. 6CCVD offers in-house deposition of standard metals (Au, Pt, Pd, Ti, W, Cu) for custom microwave guide integration or electrical contacts.

Engineering Support

Section titled “Engineering Support”

The research highlights that accurate alignment (quantified to ±1°) is the key implementation point for high-accuracy current sensing. 6CCVD’s in-house PhD team specializes in diamond material science and quantum defect engineering.

  • Material Selection Consultation: We assist engineers in selecting the optimal diamond grade (SCD vs. PCD, doping level) and post-processing recipe (irradiation dose, annealing temperature) to maximize NV yield and T2 coherence for high-precision EV Battery Monitoring projects.
  • Alignment Optimization: Our team can consult on material preparation techniques that minimize intrinsic strain and maximize the uniformity of the NV ensemble, which is crucial for maintaining the precise alignment required for transverse magnetic field compensation.
  • Global Supply Chain: We ensure reliable, global shipping (DDU default, DDP available) of sensitive diamond materials, supporting international research and manufacturing efforts.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Key implementation points for achieving full accuracy in simultaneous temperature and magnetic field measurement and linearity when applying diamond quantum sensors to electric vehicle (EV) battery monitors were investigated. Both the static and busbar current magnetic field are required to be aligned to the NV-axis. If misalignment should exist, the resonance frequency midpoint move in the direction opposite to the temperature change under a large busbar current due to the transverse magnetic field effect. Misalignment could be quantified with an accuracy of ±1° by analysing the resonance frequency midpoint change under a current of ±1,000 A. The transverse magnetic field effects compensation estimated from misalignment, confirmed that the resonance frequency midpoint changed consistently with temperature changes. Furthermore, linearity over a wide dynamic range also improved. Moreover, it will contribute to accurate alignment of the two sensors for differential detection to eliminate external noise as common mode. These are expected to expand the application of diamond sensors for high-precision measurement in a wide dynamic range.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2010 - Broadband magnetometry by infrared-absorption detection of nitrogen-vacancy ensembles in diamond [Crossref]
  2. 2009 - Diamonds with a high density of nitrogen-vacancy centers for magnetometry applications [Crossref]
  3. 2023 - Solid-state microwave magnetometer with picotesla-level sensitivity [Crossref]
  4. 2022 - Millimetre-scale magnetocardiography of living rats with thoracotomy [Crossref]
  5. 2016 - Optical magnetic detection of single-neuron action potentials using quantum defects in diamond [Crossref]
  6. 2009 - Low temperature studies of the excited-state structure of negatively charged nitrogen-vacancy color centers in diamond [Crossref]
  7. 2018 - Quantum stereomagnetometry with a dual-core photonic-crystal fiber [Crossref]
  8. 2015 - Broadband magnetometry and temperature sensing with a light-trapping diamond waveguide [Crossref]
  9. 2021 - Temperature dependence of optical centers in Ib diamond characterized by photoluminescence spectra [Crossref]

Reads Similar to This

Recombination centers in 4H-SiC investigated by electrically detected magnetic resonance and ab initio modeling Engineering of Diamond Based Sensor for Nano-Scale Magnetic Field Sources Investigation Of Diamond Circilar Saw Cutting Performance In Blended Pumice Lightweight Concrete