Directional detection of dark matter with diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-02-12 |
| Journal | Quantum Science and Technology |
| Authors | Mason C. Marshall, Matthew J Turner, Mark J. H. Ku, David F. Phillips, Ronald L. Walsworth |
| Citations | 27 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThe research proposes a novel âhybridâ solid-state detector using diamond and Nitrogen Vacancy (NV) centers for directional detection of Weakly Interacting Massive Particles (WIMPs), aiming for sensitivity below the solar neutrino floor.
- Core Challenge & Solution: Future WIMP detectors will be limited by solar neutrino backgrounds (the âneutrino floorâ). Directional detection is required for discrimination. The solution uses large-volume (mÂł) solid-state diamond targets.
- Hybrid Detection Process: Traditional particle detection (charge/phonon) triggers an event, followed by atomic physics techniques (NV center spectroscopy) to read out the directionality of the nuclear recoil damage track.
- Enabling Technology (NV Centers): NV centers act as integrated sensors for local crystal strain induced by WIMP recoil. This strain signal (estimated 1 x 10-7 to 3 x 10-6 fractional strain) is used for localization and mapping.
- Localization Requirement: The damage track must be localized to a ~”m³ voxel within 1-3 days (to outpace the expected neutrino floor event rate of O(10-30) events/year/m³). This requires achieving a strain noise floor of 1 x 10-7.
- Direction Mapping Requirement: Nanoscale mapping of the track (20-50 nm length) requires < 20 nm 3D spatial resolution, achievable via superresolution optical techniques (STED/CSD combined with Fourier magnetic imaging) or Scanning X-ray Diffraction Microscopy (SXDM).
- Material Requirements: Detector material must be high-quality, low-strain CVD diamond. Alternatively, high-nitrogen HPHT diamond can be used to create new NV centers at the recoil site for background-free localization.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Detector Scale | Multi-ton | kg | Required mass for sensitivity below the neutrino floor. |
| Target Detector Volume | Cubic meter | m3 | Required volume scale for diamond target. |
| WIMP Recoil Energy Range | 10-100 | keV | Corresponding to WIMP masses in the 1-100 GeV range. |
| Expected Damage Track Length | 20-50 | nm | For 10-30 keV initial recoil energy. |
| Expected Vacancies per Track | O(50-300) | vacancies | Estimated from SRIM simulations. |
| Target Strain Sensitivity (QDM) | 1 x 10-7 | Fractional Strain | Required noise floor for WIMP track detection. |
| WIMP Strain Signal Magnitude | 1 x 10-7 to 3 x 10-6 | Fractional Strain | Estimated voxel-averaged strain amplitude. |
| Target Localization Time | 1-3 | days/mm3 | Required speed to outpace neutrino floor event rate. |
| Nanoscale Mapping Resolution | < 20 | nm | Required 3D resolution for track directionality. |
| Pulsed MW Imaging Time (1 ”m res) | ~18 | hours/mm3 | Estimated time to image a detector segment using pulsed MW protocol. |
| Large-Scale Strain Gradient Limit | 3 x 10-5 | Fractional Strain | Maximum acceptable gradient (1 MHz NV shift) for wide-field QDM. |
| SXDM Strain Resolution | 10-4 to 10-5 | Fractional Strain | Routinely attainable via X-ray methods. |
Key Methodologies
Section titled âKey MethodologiesâThe proposed detection procedure is a three-step hybrid process combining particle physics and quantum sensing:
-
Initial Event Registration and Triangulation (mm Scale):
- WIMP or neutrino collision initiates a nuclear recoil cascade in the diamond target.
- The event is detected by traditional semiconductor methods (charge, photon, or phonon collection).
- The event location is triangulated to a single mmÂł detector segment.
-
Damage Track Localization (”m Scale):
- The triggered diamond segment is removed from the bulk detector.
- Method A: NV Strain Spectroscopy: A Quantum Diamond Microscope (QDM) is used to map crystal strain.
- Pulsed microwave (MW) protocols are employed to achieve high sensitivity (1 x 10-7 strain noise floor) and fast measurement times (~18 hours/mmÂł).
- Optical sectioning techniques (e.g., Structured Illumination Microscopy or light-sheet microscopy) are implemented to restrict the optical point spread function (PSF) axially, localizing the track to a ~”m³ voxel.
- Method B: NV Center Creation: High-nitrogen (Type Ib HPHT) diamond is used.
- Post-exposure, the diamond is annealed at high temperature, allowing recoil-induced vacancies to migrate and combine with nitrogen impurities, forming new NV centers at the track site.
- Confocal fluorescence microscopy detects the newly created NV centers, providing background-free localization.
-
Nanoscale Track Direction Mapping (< 20 nm Scale):
- The localized ”m³ voxel is analyzed using superresolution techniques to extract the head-tail asymmetry and orientation of the damage track (20-50 nm length).
- Method A: Superresolution NV Strain Spectroscopy:
- Lateral resolution (< 20 nm) is achieved using optical depletion techniques (STED or CSD) with a doughnut-shaped laser beam.
- Axial resolution (< 20 nm) is achieved using Fourier magnetic imaging, where a microfabricated gradient coil encodes the NV position onto its spin precession frequency, followed by post-processing deconvolution.
- Method B: Scanning X-ray Diffraction Microscopy (SXDM):
- A nanofocused hard X-ray beam is scanned across the sample held at the Bragg condition.
- Coherent Bragg ptychography is used to invert diffraction patterns from overlapping beam spots, yielding 3D strain maps with resolution as low as 5 nm. Multiple Bragg angles are required to fully define the strain tensor.
Commercial Applications
Section titled âCommercial ApplicationsâThe technologies developed for this directional dark matter detector have direct relevance across several high-tech industries, particularly those focused on quantum technologies and advanced materials:
- Quantum Sensing and Metrology:
- NV Center Microscopy: Commercialization of high-speed, high-sensitivity Quantum Diamond Microscopes (QDM) for magnetic, electric, and thermal sensing at the nanoscale.
- Solid-State Quantum Devices: Development of low-noise, high-coherence diamond substrates for quantum computing and quantum memory applications, leveraging low-strain CVD growth protocols.
- Advanced Semiconductor Manufacturing:
- Strain Engineering: High-resolution, 3D strain mapping (using QDM or SXDM) for quality control and defect analysis in wide-bandgap semiconductors (like diamond and SiC) used in high-power electronics and RF applications.
- CVD Diamond Production: Optimization of Chemical Vapor Deposition (CVD) processes to produce large-volume, electronic-grade diamond with extremely low intrinsic strain inhomogeneity.
- Medical and Scientific Imaging:
- Superresolution Optics: Adaptation of advanced optical sectioning methods (SIM, light-sheet) and superresolution techniques (STED, CSD) for use in high-refractive-index materials, extending their use beyond biosciences into material science.
- Radiation Dosimetry: Development of highly sensitive Fluorescent Nuclear Track Detectors (FNTDs) for precise 3D mapping of radiation dose in oncology and nuclear physics experiments.
- Nanofabrication and Microcoils:
- Techniques for fabricating microcoils and microwave guides directly onto diamond surfaces, critical for implementing Fourier magnetic imaging and other spatially selective NV spectroscopy methods.
View Original Abstract
Abstract Searches for weakly interacting massive particle (WIMP) dark matter will in the near future be sensitive to solar neutrinos. Directional detection offers a method to reject solar neutrinos and improve WIMP searches, but reaching that sensitivity with existing directional detectors poses challenges. We propose a combined atomic/particle physics approach using a large-volume diamond detector. WIMP candidate events trigger a particle detector, after which spectroscopy of nitrogen vacancy (NV) centers reads out the direction of the incoming particle. We discuss the current state of technologies required to realize directional detection in diamond and present a path towards a detector with sensitivity below the neutrino floor.